Apollo Experience Report Earth Landing System

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~~

1. Report NO.

NASA TN D-7437

Lyndon B. Johnson Space CenterHouston, Texas 77058

2. Governm ent Accession No. 3. Recipient's Catalog No.

11 . Contract or Grant No.

4. Title and Subti tle

APOLLO EXPERIENCE REPORTEARTH LANDING SYSTEM

7. Author(s1

Robert B. West, JSC

9. Performing Organization Name and Address

5. Report Date

. November 1973

6. Performing Orgaioization Code

8. Performing Organization Report N o.

JSC S-370

10. Work Unit No.

91 - 11 00- 00- 2

National Aeronautics and Space AdministrationWashington, D.C. 20546

12 . Sponsoring Agency Name and Address

14 . Sponsoring Agency Code

13 . Type of Report and Period Covered

Technical Note

17 . Key Words (Suggested by Author(s) )

' Landing Aids' Spacecraft Landing* Water Landing* Apollo Spacecraf t

19. Security Classif. (o f this report)

None

18. Distribution Statement

20. Security Classif. (of this page)

None

I 21 . NO. of P a w s I 22. Price

Domestic, $3.75" I oreign, 56.25

* Fo r sale by the National Tech nical Information Serv ice, Springfield, Virginia 22151



CONTENTS

Section Page

SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

3UNCTIONAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . .

4IGNIFICANT PROBLEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5ommand Module Weight Increase . . . . . . . . . . . . . . . . . . . . . . .

8ain-Parachute-Cluster Interference . . . . . . . . . . . . . . . . . . . . .

9arachute Ri ser Abrasion . . . . . . . . . . . . . . . . . . . . . . . . . . .

Main-Parachute Canopy Strength Increase . . . . . . . . . . . . . . . . . . . .

High-Density Parachute Packing . . . . . . . . . . . . . . . . . . . . . . . . . 11

10

Forward-Heat- Shield Recontact 13. . . . . . . . . . . . . . . . . . . . . . .

Win -Pa rac hut e Oxidizer Burn Damage . . . . . . . . . . . . . . . . . . . . 14

CONCLUDING REMARKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

APPENDIX A- ESCRIPTION O F ELS COMPONENTS . . . . . . . . . . . . . A-1

APPENDIX B- SUMMARY OF TESTS. . . . . . . . . . . . . . . . . . . . . . B - 1

APPENDIX C- POLLO 1 5 MAIN PARACHUTE FAILURE . . . . . . . . . . C - 1

iii



TABLES

Table Page

I MAIN-PARACHUTE DESIGN LOADS . . . . . . . . . . . . . . . . . . . 7

11 VOLUMETRIC REQUIREMENTS OF MAM-PARACHUTE PACK . . . . 11

A-I COMPARATIVE CHARACTERISTICS O F ORIGINAL AND FINALBLOCK I1 DROGUE PARACHUTES . . . . . . . . . . . . . . . . . A-11

B-I SUMMARY O F BLOCK I LABORATORY TESTING . . . . . . . . . . . B-2

B-I1 SUMMARY O F BLOCK I QUALIFICATION DROP TESTS . . . . . . . . B-8

B-111 SUMMARY O F BLOCK 11 QUALIFICATION DROP TESTS . . . . . . . . B-10

B-IV SUMMARY O F INCREASED CAPABILITY BLOCK I1

QUALIFICATION DROP TESTS . . . . . . . . . . . . . . . . . . . . B- 13

C-I COMMAND MODULE/FORWARD HEAT SHIELD TRAJECTORY

PARAMETERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-21

FIGURES

Figure

4

5

6

7

8

A- 1

A- 2

A- 3

Logic and redundancy in the ELS . . . . . . . . . . . . . . . . . . . .

Normal recovery sequence . . . . . . . . . . . . . . . . . . . . . . .

Pad- and low-altitude-abort sequence . . . . . . . . . . . . . . . . .

Total main-parachute load compared with Chl weight . . . . . . . . .

Increa ses i n CM recovery weight . . . . . . . . . . . . . . . . . . . .

Parachute attachment and disconnect fitting . . . . . . . . . . . . . .

M a in-parac hu te reinforcement . . . . . . . . . . . . . . . . . . . . .

Block I1 forward-heat-shield parachute system . . . . . . . . . . . .

Block I ELS installation . . . . . . . . . . . . . . . . . . . . . . . . .

Block I drogue parachute . . . . . . . . . . . . . . . . . . . . . . . .

Block I drogue-parachute m or tar ass embly . . . . . . . . . . . . . .

Page

3

4

4

5

6

10

11

14

A- 1

A- 2

A- 2

iv



PageFigure

B - 6

c - 1

c - 2

c - 3

c-4

c - 5

C - 6

c - 7

C -8

c - 9

c- 0

c - 1 1

c - 1 2

C - 1 3

Deployment envelope

(a) Drogue parachute . . . . . . . . . . . . . . . . . . . . . . . . . . B - 1 4(b ) Main parachute . . . . . . . . . . . . . . . . . . . . . . . . . . . B- 14

Spacecraft descending with one main parachute fa iled . . . . . . . . . C - 4

Parachute system configuration . . . . . . . . . . . . . . . . . . . . . C -5

Sequence of events during descent on the main parachutes

Parachute location at tim e of f ailure . . . . . . . . . . . . . . . . . . C -9

. . . . . . C - 7

Parachute r is er damage during final descent . . . . . . . . . . . . . . C - 10

Approximate location of r ecovery force s at 295 hours9 minutes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C - 1 2

Main parachute connector link failure . . . . . . . . . . . . . . . . . C- 14

Magnified view of Apollo 15 Dacron ris er protective cover . . . . . . C - 1 5

C- 18

C-19

Television fr ame and trajectory analysis . . . . . . . . . . . . . . . .

Position of forward heat shield relat ive to spa cecraf t traje ctory . . .

Results of forward heat shield/suspension s ys tem impact te st . . . . . C - 2 2

C - 2 3

C - 2 9

Forward heat shield damage . . . . . . . . . . . . . . . . . . . . . . .Parachute tow test loads . . . . . . . . . . . . . . . . . . . . . . . . .

vi



APO LLO EXP ER l ENCE REPORT

EARTH LAND ING SYSTEM

By Robert B. West

Lyndon 6. Johnson Space Center

SUMMARY

The Apollo earth landing system operational requirements were defined through

detailed rev iews of the total-miss ion environments associated with both normal atmos-

pheric entry and the vari ous abort contingencies. These operational requirements andthe necessity fo r compatible inte rface with the command module dictated the basic de-

sign and performance requir ements of the earth landing sys tem. Fo r example, the highrecovery weight of the command module ruled out the use of a single main-parachute

syst em because of the lack of experience with single parachutes i n a size needed to

recover the spacecraft within the limitations placed on the rate of descent. In addition,

the Apollo upper-deck st ruc tur e presented formidable problems f or packing and install-

ing a single parachute of the required size.

Although much w a s known relative to the system requirement s during the initialphases of the program, considerably more knowledge was gained during the cou rse of

the development prog ram. The more significant problems encountered during the de-

velopment of the Apollo ea rt h landing sy st em , the solutions, and the general knowledgegained from having encountered these problems a r e discussed. A brief description of

the Block I, Block II, and Increased Capability Block II systems and a summary of the

test prog rams that were conducted are included.

INTRODU CTI ON

In January 1962, the original specifications were released for a parachute recov-

er y s yste m to be incorporated on the Apollo command module (CM). The original pro-

gr am to develop and to provide this sys tem was anticipated to extend over a period of

13 months; however, the final Apollo ea rth landing sys tem (ELS) ualification test w a snot completed unti l July 1968. Then the system was considered suitable fo r manned

lunar missions.

Early in the Apollo P rogr am, the fact was recognized that, to accomplish thelunar-landing miss ion, ce rta in major changes would have to be made to the in itial CM

design, In consideration of progr am cost and schedular, a decision w a s made to con-

tinue the orig inal CM configuration (then designated as Block I) through the initial



earth -orbit al system-verification flights. At the same time, a Block 11 program was

initiated to implement the changes to the CM that wer e needed to accomplish the lunar-landing mission.

The major differences between the Blocks I and I1 spacecra ft affecting the ELS

were as follows.

1. The docking tunnel w a s shortened and the tunnel wall was tapered slightly in-ward. This modification significantly changed the shape of the main-parachute stowage

compartment and necessi tated complete redesign of the main-parachute deployment bag

and the retention sys tem .

2. A single st ruc tura l assembly (called the flowerpot) was incorporated to attach

the two drogue risers and the thr ee main-parachute risers to the CM at a single loca-

tion. This attachment fitting al so ser ved as the housing for the riser disconnects.

3 . The pilot-parachute morta r mounts we re moved fro m the deck of the forward

compartment and relocated on the side of the gussets.

4 . The CM uprighting bags were removed fro m the gusse t-mounted conta iners

and relocated under the main-parachute packs on the deck.

The drogue, pilot, and main parachutes remained ess entia lly unchanged f rom the

Block I configuration except for a length of steel riser incorporated in the lower end of

the main-parachute riser for protection fro m abrasion. After the spacecraft 012 f i re ,

many modifications were made to the Block I1 CM, resul ting in a significant incr eas e

in vehicle weight. Analysis indicated that the projected weight incr ea se would res ult

in parachute loads grea ter than those that either the ELS or the CM str uct ure was

capable of withstanding safely. Therefore, in mid-1967, a program was initiated to

inc reas e the capability of t he ELS and to reduce the main-parachute loads to acceptable

level s with the g reat er CM weight. The major changes made to the ELS during this

program were as follows.

1. The main-parachute reefing sys tem was modified to incorpo rat e an additional

stage in the inflation proces s to reduce the peak opening loads.

2. T h e diameter of the drogue parachutes was inc rea sed to reduce the dynamic-

pr es su re conditions and to provide a more stable vehicle at the tim e of main-parachute

deployment.

3 . T he siz e of the drogue-parachute m ort ar was incr eas ed to provide the addi-

tional volume required by the l ar ger drogue parachute.

4 . The parachute reefing-line-cutter time-delay was modified to obtain delay

tim es of 6 and 10 seconds fo r the two-stage main-parachute reefing sys tem .

The various components of the Block I , Block 11, and Increased Capability

Block 11 systems ar e discussed i n detail in appendix A. In appendix B the te st pr o-

grams that were conducted to develop and to qualify the ELS are outlined.

2



FUNCTIONAL DESCR IPT ION

The ELS con sis ts of the various parachutes and rel ated components necess ary to

stabil ize and to decelerate the CM to conditions that a r e safe for landing. The ELS was

designed to recover the CM after eithe r a normal entry o r a launch abort. Nine para -

chutes are insta lled on the CM all of which function during the recovery sequence.Three main parachutes, thre e pilot parachutes, two drogue parachutes, and a forward-

heat- shield-separation-augmentation parachute are included.

The recov ery sequence is initia ted automatically through the c los ure of baro-

met ric switches o r through the function of time-delay rel ays . A logic diagram illus-

tra ting each of the ELS unctions is presented in figure 1. A normal-entry orhigh-altitude-abort recovery sequence begins with the jettisoning of t h e forward heat

shield at a nominal altitude of 24 000 feet (fig. 2). Immediately after separation of the

System

System

24 O W f t

baroswitches

Drogue-

parachute

disconnect

A

E

TD =t im e

11am-nbaroswitches

Crew:switch

(main-parachute ~ ~ i ~ -

disconnect) parachute

disconnect

-delay relay

Figure 1 . - Logic and redundancy in the ELS.

3



Splashdown velocitie r

Three parachutes - 32 fp s %@Two parachutes - 36 fps

1. Forward heat shield jettisoned at 24 Mx) R

+0.4 sec2. Drogue parachut es deployed reefed at

3. Drogueparachute single-stage disreef,

4. Drogue parachutes jettisoned and main

5 . Main-parachute initial inflation

6. Main-parachute first-stage disreef,6 sec

7 . vh f recoveryantennas and flashing

beacon deployed, 8 sec

8. Main-parachute second-stagedisreef,

10 sec, approximately 9 Mx) R9. Main parachutes released

24 OO O A +2 sec

10 sec

parachutes deployed by pilot para-

chutes at 11M)o A

heat shield fro m the CM, a small, 7.2-foot-

diameter parachute is mortar-deployed f rom

the forward heat shield. This parachute ex-

erts a force to extract the jettisoned heat

shield from the wake of the C M . Two

16.5-foot-diameter conica l ribbon drogue

parachutes are mortar-deployed 1. 6 sec-

onds after f orward-heat- shield jettison.The drogue parachute s undergo a 10-second

reefed interva l before disreefing to full

open, and remain attached to the CM to analti tude of approximately 11000 feet. At

drogue disconnect, three 7.2-foot-diameterringslot pilot parachutes are mortar-

deployed. The pilot parachutes then pro-

vide the force necessary to rele ase themain-parachute retention system and toextract the main-parachute -3ck assembl ies.

The main-parachute packs &re hen pulled

away from the CM and the th re e 83.5-foot-diamete r main parachutes are extracted

fr om the deployment bags. Each main para -

chute then inflates through two reefing s tag es

to a full-open condition.

Figure 2. - Normal recovery sequence. If a launch abort should occur and

tude attained is below the opening altitude of the baroswitches, forward-heat-shield

jett ison and deployment of the drogue and pilot parachutes occur on a timed sequence,

controlled by the time-delay r ela ys . The events that occur during a launch abort ar eillustrated in figure 3.

conditions are such that the maximum alti-

Arm EL S and jettison launch escape S I GN I F I CANT PROBLEMSower, boost protective cover, and

docking ring (1 4 seclDrogue parachutes

deployed (16 seclforward heat shield

jettisoned(14 4 se d Throughout the ELS developmental8 program, emphasis w a s placed on provid-

Mainparachutes ing a CM recov ery syste m capable of func-

tioning properly under extremely sev er eflight conditions. A t the sam e time, the de-

mands placed on the syst em in te rm s of vehi-cl e recovery weight, component stowage, and

vehicle interfac e requ irements continuedto grow. During the pro gram , extrememea sure s appeared to be necessary in term s

of system o r spacecraft redesign to satisfythe require ments imposed on the recovery

Canards deployed

111secl

[ - ) + c )

Launch escape

motor ignited

Figure 3. - Pad- and low-altitude-

abort sequence.

4



system. Through the applied effor ts of the various groups and agencies associated with

the system, these problems were resolved with minimum design changes and with t h eleast impac t on the Apollo Program.

In addition to resolving difficult des ign problems, devising and optimizing compo-

nent manufacturing and assembling techniques were a lso ne ces sar y to ensu re that each

pa rt would function properly once it w a s assembled and installed on the spacec raft. On

none of the previous space programs w a s it neces sary to contain the parachutes i n the

limited volumes and in the irregular shapes necessary in the Apollo Pro gram. This

requirement necess itated the development of preci se techniques fo r packing the para-

chutes at ve ry high densit ies without inflicting damage that could propagate dur ing de-

ployment. The incorporat ion of steel cable as an int egral part of the parachute risersrequired the development of stowage techniques that would provide assurance that the

cable deployed consistently and safely.

,

mI

In addition to stringent program requirements, sev era l specific technical prob-

lems , the solution of which required the development of innovative methods and tech-

niques, were encountered. In the following section, the more significant problems

encountered, their solutions, and the knowledge gained are discussed.

tained on two of the th ree tests and because

of the first announcement of a C M weight

Command Module Weight I ncrease

creas ed the strength of the s truc tur al

Figure 4 ' - main-parachute load members of the parachute. These changes

caused a significant increa se i n weight andcompared with CM weight.

5



reefing cutter. In conjunction with the main-parachute-design changes, definition of themaximum volume available fo r l arge r drogue-parachute mortar s became necessar y be-

cause the siz e of the drogue parachute w a s limited primar ily by the size of the mort ar

tubes that could be fitted to the spacecraft . Volume w a s made available for mortars

accommodating 16.5-foot-diameter drogue parachutes.

Because the Block 11 schedule required delivery of parachutes for installation onspacecr af t 101 (Apollo 7 mission) by mid-November 1967, the Increased Capability

Block 11program w a s recognized as a high-risk effor t in te rms of potentially delaying

the first Block 11 flight. Therefore, th e total effort was afforded a high priority and

received the utmost support at all levels. Considering the schedule requi rement s, the

plan w a s to deliver the first production system for installation on spacecra ft 101; the

followup system, which would be identical in configuration, was scheduled to support

the system-qualification aerial drop test . Satisfactory completion of the total sys tem-

qualification effort w a s placed as a constraint on the Apollo 7 mission.

The main-parachute design-limit loads defined fo r the Block 11 11 000-pound C Mand the design-limit loads fo r the final Block 11main parachutes with the 13 000-pound

CM are presented in table I. These load values provide an indication of the effective-ne ss of the changes made to the Block II s y s t e m . This table should not be used as adirect comparative evaluation of the changes, because data obtained during the Increased

Capability Block 11program allowed for considerable refinement of the para met er s used

in establishing the design-load values. The changes that were made to the ELS effec-

tively counteracted the inc rease in CM weight and accomplished the requi red reduction

in main-parachute loads.

TABLE I. - MAIN-PARACHUTE DESIGN LOADS

Parachute configurations

Individual

Fir st stage

Second stage

Full open

Design loads, lb

(a

Original Block 11 ELS

with 11000-lb C M

2 1 800

24 700

I Total cluster I 39 000

Final Block I1 ELS

with 13 000-lb CM

2 2 000

23 800

2 2 900

37 500

aThese values should not be used for direct comparison.

7



Main-Parachute-Cluster Interference

On November 27, 1962, the first aer ial drop test was made using a parachute testvehicle ( P T V ) to investigate the perf ormance characte ristic s of a cluste r of th ree inde-

pendently deployed 88.1-foot-diameter ringsa il main parachutes. Fo r the initial test,the vehicle w a s ballasted to only 4750 pounds, one-half the weight of the CM. The con-

figuration of the parachute test specimens and the related components represented the

then-current spacecraft design. Deployment of the main parachutes was achieved bysimultaneously mor ar -dep oy ed pi lot parachutes .

The resu lts of th is test indicated a significant problem rel ative to the deployment

behavior of clust ered ringsa il parachutes and eventually led to so me unique design fea-tur es in the main parachutes. The thre e ringsail parachutes inflated in a nonsynchro-

nous manner, that is, one canopy inflated rapidly and inhibited the filling of the laggingparachutes . This behavior was m ost pronounced during the inflation following disreef.This crowding effect and nonsynchronous inflation, often re fe rr ed to as cluster inter-

fer enc e, was not a new phenomenon but w a s unusually pronounced with the ringsail de-

sign. This uneven load sharing resulted in abnormally high opening loads on theleading parachute i n the clu ste r.

The approach taken to cor re ct t his condition was to explore modifications that

would reduce the ra te of inflation of the parachute . Much of this rapid inflation of the

ringsail parachute w a s attributed to a characteristic of the canopy to continue to fi l l

during the reefed in terval and thus produce a large reefed shape with internal pres sur es

throughout a large portion of the canopy. This characteri stic, in turn, contributed to arap id full-open inflation following dis ree f. The flow of air around the l arge bulbous

shape of a rapidly developed leading parachute w a s als o noted to have a distorting ef-fec t on the adjacent lagging parachutes and to greatly inhibit the inflation in the r eef ed

condition.

The modificatioh demonstrating the most favo rable e ffect in reducing the clu ste r

interference was the remova l of 75 percent of the ma ter ial from the fifth ring of thecanopy, thereby forming a n open ring around the periphery of the crown. Thi s open

rin g limited canopy growth in the r eefed condition to a more cigar-like profile and pro-

duced near-uniform growth of each of the th ree main parachutes during reefed and dis-

reefed inflation. A second change, great ly improving the shape of the lower s ki rt areaand allowing a more efficient inflow of air into all three parachutes, was the relocation

of the reefing rings on the s ki rt band fr om the radial seam-attachment point to a point

on the skirt band in the middle of the gore (r ef er re d to as midgore reefing).

Based on test res ults obtained during this sa me effort, a decision was also made

to remove fou r complete gor es fr om the main-parachute canopy to reduce weight. This

modification produced the basic 68-gore-configuration main parachute that would even-

tually be flown on Apollo spacecraft.

The combination of reduced peak opening loads and the removal of material re-sulted in a net allowable weight saving of approximately 45 pounds i n the main par a-chute and harnes s assembly without exceeding the specified maximum ra te of descent

of 33 fps at 5000-foot pr es su re altitude. The open-ring-configuration main parachutes

also reduced the syste m oscillations of the two-parachute cl ust er configuration fr om

approximately t 20" to t So, causing a reduction i n landing haza rds.

8



P a r a c h u t e R i s e r A b r a s io n

On September 6, 1962, during the fifth total-system developmental test, using the

boilerplate (BP) 3 test vehicle, a se ri es of events occurred that r esulted in separation

of the main parachutes and loss of the vehicle. The BP failed to stabilize during the

drogue-parachute interval, and the pilot mortars fired wi th the vehicle in an apex-

forward (approximately 60") flight attitude. The existing main-parachute ri se r s, whichwere joined at a confluence above the veh icle, hung under the air lock with the vehicle

in thi s flight attitude. This anomaly prevented full deployment of the ha rness until the

vehicle rotated t o a more f avorable attitude. The parachute opening loads were trans-

mitted through the unprotected textil e harness legs directly into the gusse ts and the air-lock structure, promptly severing the harnes s legs.

After this test, the main-parachute harness assembly w a s completely redesigned

to preclude the possibility of its hanging during deployment. The test also made evidentthe fact that the parachute sys tem had to be capable of deployment fr om an unstable o r

oscillating CM . To provide thi s capability, steps were taken to minimize the numberof areas on the vehicle that could cause cutting and abra sion to the parachute r is er s.

Because of requir emen ts external to the ELS, elocation of cer ta in it ems of spacecraftequipment o r provision of a surrounding st ruc ture that would not c ause damage to the

fabric r i se r s was not possible. It w a s necessary to provide risers with a high degree

of abrasive resistance.

Investigation of var ious types of protective sleeving resulted in the selection of

Dacron felt with wire-b raid covering and resin impregnation fo r the Block I main-

parachute attachment ha rness . The requi red degree of protection and the required

flexibility for stowage and deployment ruled out thi s approach f or the drogue- and pilot-

parachute risers. Thus, the decision was made to pursue the development of st ee l

cable risers to provide the necessar y abrasion resistance in the lower portion of the

risers where the re wa s high probability of contact with the C M structure.

The incorporat ion of the flowerpot parachute att achment and the disconnect fitting

on the Block I1 spacecraft made redesigning the main-parachute risers necessary

(fig. 6). The flowerpot concept brought the tw o drogue-parachute ri se r s and the thr ee

main-parachute risers into a common fitting. This concept reduced the available

volume and eliminated the possibility of using the bulky Block I-type p rotected-fabric

riser on the Block 11 spacecraft. Stowage tests on a Block I1 upper-deck mockup indi-

cated that steel-cab le main-parachute r i s e r s could be incorpor ated and stowed in amanner assuring orderly deployment. Because the steel-cable main-parachute riserprovided a solut ion to the Block 11volume problem and afforded the necessary resist-ance to abrasion, the decision was made to incorporate it in the Block 11 system.

Developmental tests on the drogue- and pilot-parachute syste ms incorporating

steel-riser segments demonstrated that th e cable risers could be stowed with the para-chute i n the mor tar tube. A major problem i n using steel cable w a s the possibility of

kinks developing during deployment and seriously degrading the s trength of the r i se r .

Some kinking w a s experienced in ear ly developmental morta r firings; however, rev er se

twisting of the cable while it w a s being stowed and a modification to the cable-end fittingeliminated the problem.

9



1rogue parachute

S e c t i o n A A

Figure 6. - Parachute attachment and

disconnect fitting.

In sev era l of the Block I1 aerial drop

te st s incorporating the flowerpot parachute

attachment fitting, numerous cable st ran dswere damaged on the drogue risers. This

damage occur red in the portion of the cable

riser that contacted the lip of the flowerpotfitting while the vehicle w a s oscillating and

the parachute loads were high.

Laboratory tests were conducted to

simulate the dynamics between the drogue

steel-cable riser and the flowerpot fitting

with loads applied to the ri se r. A s the

parachute loads were applied through the

riser over the lip of the flowerpot, the setests revealed sufficient deflection in the

flowerpot lip to cause a local misalinement

between the two halves, resulting in a slight

ridge over which the cable w a s abraded.

Abrasion w a s also caused when the fourst rands of cable in a ris er arranged them-

se lves such that one cable would be loaded

ac ro ss another while bent over the lip of

the flowerpot.

A 4-inch-wide band of lead tape, wrapped around each of the drogue riser cables

where they cro ssed the lip of the flowerpot, provided excellent protection from ab ra -

sion and proved to be a simple and an effective solution to the problem. In the Blocks I

and 11 systems , the steel-cable parachute risers proved a n acceptable design and func-tioned correc tly on all tes ts and flights.

Main-Parachute Canopy Strength Increase

During the second aer ia l drop tes t in the original Block II developmental t es t

ser ies , a significant deficiency w a s found i n the s tr uc tu ra l capability of the main-parachute canopy. The test was established to demonstrate the deployment char act er-

is ti cs of the main parachute at a full-open limit-load condition following deployment

fr om the Block 11 deployment bag. The main-parachute design remained unchanged be-tween Blocks I and II; the re was littl e concern about the s tru ctura l capability of the

main parachute because it had been demonstrat ed at ultimate-load conditions in exc ess

Of 33 000 pounds during the Block I qualification prog ram. During this test, however,a complete gore w a s spli t fro m the skir t band to the vent band of the main parachute

under an axial load between 20 000 and 23 000 pounds while inflating fro m disreef tofu ll open. Although the parachute design previously had been subjected to significantly

higher loads following dis reef , a post-test investigation revealed that it had never beenexposed to the conditions of this par ticul ar test.

Because of the inherent inflation charac te ris ti cs of the main parachute , the con-ditions of this te st produced much higher lo ca l- st re ss levels in the canopy skirt than

were experienced with conditions at a much higher axial load on previous tests. This

10



Because of the damage being sustained, a concerted effort w a s made to design

handling equipment and to establish procedures minimizing packing damage. Duringthis effort, approximately 70 trial parachute-packing operations were performed, in

addition to the parachute packing that was being accomplished to support the develop-

mental aerial drop tests. Steps taken to co rre ct this problem were as follows.

1. Several basic deployment-bag des igns were t rie d with many modifications to

each design. A Teflon-impregnated cloth liner was used i n the deployment bag to re-duce friction between the parachute and the bag.

2. A high-pressure packing ram w a s developed with rotating pr es sur e feet,

swivel-mounted hydraulic cy linders , and other special featu res designed to aid packing.

3. The design of the packing pr es su re feet and protective pads w a s modified

many times.

4. A high-capacity vacuum system was used as an integ ral par t of the packingcontainer to evacuate air from the folds of cloth during packing.

5. Severa l packing-container designs were tr ie d with many modifications toeach design.

6. Packing-container in se rt s were designed to gain subtle changes in pack

contours.

7. Various lubricants (Teflon spr ay , Tef lon-coated cloth, et cetera) were used

on the walls of the packing container to aid in packing under p res sur e.

8. Variations in packing pres su re and in soak times were introduced at various

stages in the packing pro ces s.

9. Combinations of high and low packing pressures were introduced at variousstages during the packing process.

10. Changes were made in the design of t he reefing r ings and in the method of

placing them in the deployment bag.

11. Padded reefing-cutter packets were developed and incorporated into the

parachutes.

Because of the high densi ties achieved and because of the tendency fo r the para-

chute packs to expand when removed f ro m the packing container, fo rm blocks and

vacuum packaging were necessary for stor age of the parachute packs to e nsure a proper

fit of the parachute pack during installat ion on the spac ecra ft.

12



The high-density parachute-packing equipment and the procedures developed and

refined throughout the program allowed fo r maximum us e of the available stowage

volume on the spacecraft . Although minor packing damage (smal l cu ts and burns) isstill present, it is reduced to a level no longer considered to be a hazard o r problem

to the parachutes.

Fo rwa rd -Hea t - Sh ie ld Recon tac t

During the recovery sequence fo r spacecraft 009 (Apollo-Saturn (AS) 201), a data-acquisition ca me ra mounted in the CM disclosed a potentially hazardous condition thatcould have had an adver se effect on successful operation of the parachute recovery sys -

tem. Immediately following the jet tison of the forward heat shield, the cover separated

from the vehicle and then returned toward the upper deck at a relatively high rate.Further aerodynamic studies revealed that the forward heat shield jettison sy stem did

not provide sufficient energy to thrust the heat shield through the st rong re ve rs e flow

present in the wake of a stable CM. To ensure separation of the forward heat shield,

a conventional pilot-parachute mortar assembly w a s mounted in the apex of the cover,

oriented to fire straight up from the vehicle, and initiated by the sam e signal thatinitiated thruster firing of the forward heat shield. This modification w a s never tested

in the Block I BP aerial drop tests (they were already completed), but w a s tested in ase r ies of ground fir ing s and was incorporated successful ly on each of the remaining

Block I spacecraft.

Because of the Block I recontact problem, consideration w a s given to the possi-

bility that this condition existed on the Block II vehicle. Analysis indicated that recon-

tact would not occur because of a 30-percent reduction in the weight of the forward heat

shield and because of an incr ease in thruster output; they combined to provide a separa-tion velocity of 45 fps as compared to the Block I value of 24 fps. However, during the

final BP a eri al drop test in the orig inal Block 11ELS qualification program, onboard

cameras revealed that the same condition previously encountered on the Block I AS 201flight was again present i n the Block II system.

The Block I1 forward heat shield w a s captured in the wake of the vehicle, and the

re ve rs e flow, which w a s stronger than anticipated, forced it back toward the parachute

compartment. Because this condition represented a serious hazard to the ELS, appro-

pria te corr ecti ve action was again taken through the addition of a Block 11 forward-heat-

shield-separation-augmentation parachute system (fig. 8).

Because this condition was observed on the final qualification drop test for theoriginal Block II system, and because no unmanned Block 11flights were scheduled,concern was focused on a method to demonstrate the fix. This problem w a s resolved

when the Increased Capability ELS prog ram provided a means of evaluating +heper-formance of the forward-heat-shield- separation- augmentation system during total-system aerial drop tests.

13



CO NCLUDI NG REMARKS

The performance of the ELS during many rigorous tests, and the performance of

each component of the ELS during the spacecraft flights proved that the progr am objec-

tives had been met. A parachute-recovery system was provided that sa tisfied the mis-

sion requirements , was compatible with the physical charac te ri st ics of the vehicle, andhad a high degree of reliability. The increasingly sev er e demands placed on the ELS

in te rm s of recovery weight, limited stowage volume, and a wide range of initial con-

ditions we re met and resolved without undue impact on the ove ral l Apollo Progr am .

Lyndon B. Johnson Space Cente r

National Aeronaut ics and Space Administration

Houston, Texas, July 2, 1973914-11-00-00-72

15



A P P E N D I X A

DESCRI PT I O N OF ELS COMPONENTS

The basic sys tem concept of the ELS changed little throughout the program fromthat described in the original statement of work. However, the individual components

of the sys tem underwent numerous changes as the program progressed through the

Block I and 11phases. The following is a brief description of the major components of

the Block I, Block 11, and Increased Capability Block II ELS.

BLOCK I ELS

The original parachute sys tem consisted of a single, mortar-deployed, 13. 7-foot-diameter, 25 " conical-ribbon drogue parachute which w a s attached to the CM in the

- Z quadrant of the forward compartment by a 56.75-foot fabric riser and three mortar-deployed, 10-foot-diameter , ingslot-type pilot parachutes, used to extract and deployth re e 88.1-foot-diameter ringsail main parachutes. The main parachutes were joined

at a confluence fitting 62 inches above the CM. This fitting w as attached to the C M by

four harnes s legs that suspended the spacecraft f rom points located at the top of theforward-compartment gussets. Originally, a main-parachute disconnect w a s to becontained in this confluence fitting.

Problems such as vehicle weight increase, main-parachute inflation anomalies,

and r i se r abrasion resulted in many modifications to components of the Block I ELS.The Block I system flown on the first Apollo spacecraft is illustrated in figure A-1.This sy st em used two mortar-deployed drogue parachutes, attached by steel- cable

ris ers to a single disconnect fitting. Three mortar-deployed pilot parachutes extracted

Figure A-1. - Block I ELS nstallation.

A-



the three main parachutes that were connected by fabr ic ri se rs to a sing le confluence

fitting.

mounted, main- parachute disconnects.

Two harnes s legs extended from the confluence fitting down to two upper-deck-

Drogue-Parachu te Sys tems

The drogue parachu te, a 13.7-foot-diameter conical ribbon type, was activelyreefed to 39.3 percent of its nominal diameter by redundant reefing lines with two

8-second reefing cutt er s pe r line. This parachute is illu stra ted in figure A-2. The

drogue-parachute mortar assembly is illustra ted in figure A-3. An electri c cu rre nt

first initiates burning of pyrotechnics in the pre ss ure cartridges. Expanding gase s

then flow from the breech assembly through a re str ict or and into the drogue morta r

tube. As the gas pre ss ure inc rea ses in the tube, the sabot assembly, acting as apiston, ejects the drogue-parachute pack assembly into the ai rst rea m. The inertia in

the system, and the airloads, cause the drogue parachute to be extracted from the

deployment bag; the steel-cable portion of the riser, contained in a polyurethane foam

ring, breaks out of the foamed ring and uncoils. The parachute then goes through an o r i a l inflation process.

-

Deployment bag,

t t m-d ro g u e p a ra c h u te

Nomina l d iameter: 13.7 ft

No. o l g o r e s ; 16Co n s t ru c te d p o ro s i t y: 23 p e r c e n t

Re e l in g d u ra t io n : 8 ec

Drag area reefed: 41 ft 2Drag area d is reefed: 68 $Su r f a c e a re a: 146 t12

1~

Figu re A-2. - Block I drogue parachute.

-Cover

Ring, foamed rise;-

/

\-s R e s t r i c t o r

P r e s s u r e c a r t r id g e

Figure A-3. - Block I drogue-parachutemort ar assembly.

A- 2



Pilo t- P a rachUte System

The pilot parachute, which extract s and deploys the main parachute, is illustrated

in figure A-4. This was a 7.2-foot-diameter ringslot design permanently attached to

the main parachute and main-parachute deployment bag. The pilot-parachute mo rt ar ,

pack assembly , and rel ated components are illust rated in figure A-5. As with the

drogue sy st em , the pilot parachute was deployed through the action of expanding gas in

the morta r tube. The pilot parachute then

provided the force required to rel eas e the

main-parachute retention sys tem and ex-

tr ac t the main-parachute pack from the CM .

P a r a c h u t e t yp e r i n g s l o t

N o m i n a l d i a m e t e r 7 2 flN o of g o r e s 17C o n s t r u c t e d p o r o s i t y 22 p e r c e n t

@ r a ga r e a 24 4 ft2

Figure A-4. - Block I pilot parachute.

R ing , f oamed r ise r- \\ -h

Pack assembly

Sabot assembly

B r e e c h

1 J assembly

% p i l o t p r e s s u r e

car t r idge

Figure A-5. - Block I pilot-parachute

mortar assembly.

Mai n- P a rachu te Sy s te m

The main-parachute system consisted of the three main parachutes, thr ee main-parachute retention assemblies, a main-parachute harness assembly, and two main-.

parachute .attachment fittings. The Block I main parachute was an 83.5-foot-diameter

ringsa il design, actively reefed to 9.5 percent of it s nominal diamete r by redundant

reefing lines with thre e 8-second reefing cut ter s per line. The final Block I main para-

chute is illustrated i n figure A-6 DR = diameter reefed). The main parachute w a s

packed in a deployment bag reta ined on the u p p e r deck of the CMagainstthea irlock w a l lby the main-parachute retention-flaps assembly (fig. A - 7 ) . Force exer ted by the pilot

A- 3



125

-

0 b

Deployment bag,main parachute

7.25 Ib I 1 -

29.25 I

1

No. of gores: 68

Calculated total porosity: 12 percentReefing: 7 . 9 R DR (9 .5 percent midgore)

Reefing duration: 8 ec

Drag area reefed: 353 ftZ

Drag area disreefd: 4MxJ ft2

Center flap?--I

Figure A-7. - Block I main-parachute

retention ass embly.

parachute relea sed a chain lace securing the

retention-assembly cen ter panel to the two

side flaps and to the upper flap. Release of

the chain lace allowed the c enter flap to open

outward and rele ase the main-parachute pack.

A s the pilot parachute lifted the main-

parachute pack away from the vehicle, the

main parachute was extracted fro m the de-

ployment bag in an o rderly manner beginning

with the connector links, followed by the

suspension line s, and finally by the canopy.

Figure A-6. Block I main parachute.

M a i n P a rac hUte Ha rne ss Assembly

Two har ness l egs and a confluence fitting constituted the main-parachute ha rn es sassembly. The harness assembly ser ved as a bridge between the th ree main-parachute

risers and the harness-attachment fittings.of the vehicle. The main-parachute harnes sassembly is illustrated i n figure A-8.

A- 4



Riser to main-oarachute nM a i n P a r a chU t e A t t ach m e nt F i t t i ngv/ack, +Z ay

Riser to main-

parachute pack,

Figure A-8. - Block I main-parachuteharn ess assembly.

Disconnect

pressureartridgeA\

vehicle

harness

Figure A-9. Block I main-parachute

attachment and disconnect fitting.

The two main-parachute attachmentfittings we re located on the upper deck of

the C M at the base of longerons 3 and 4.Each of the two fitt ings was capable of with-

standing the total opening loads generated

by the th re e main parachu tes. A main-

parachute-harness disconnect wasincorpo-rated into each of these attachment fittings.

This unit included a pyrotechnic pr es sur ecartr idge which, when initiated, drove asharp blade into the har nes s retaining pin,

severing that leg of the harness and releas-ing it fr om the vehicle. The main-parachute

attachment fitting and har nes s disconnectar e illustra ted in figure A-9. As a safety

feature , the two disconnects received their

current from two separate electrical

sources ; thus, an inadvertent prem atur e

signal would disconnect only one leg of th e

harn ess , and the main parachu tes would

remain attached to the C M through the otherleg.

R e e f in g C u t t e r s

The 8-second reefing-line cutters

used in the Block I drogue and main para-

chutes we re identical and interchangeable.

The reefing cut ters were used to se ver the

reefing line, which limited the inflated di-

amet er of the parachute for a predeter-

mined time, thus reducing the parachute

opening loads.

The reefing cutte rs (fig. A-10) were

contained i n cutt er pockets sewed to thesk irt of the parachute. A lanyard was then

attached fr om the reefing-cutter she ar pinto a suspension line on the parachute. Ten-

sion in the suspension line caused the lan-

yard to extrac t the cutter shear pin, cockingand rel eas ing the cutter firing pin. The

firing pin then st ruck and detonated apri mer that ignited an 8-second pyrotechnictime-delay element in the cutt er. At the

A- 5



r M o u n t i n g ing

Time-delay compound(three to four pressings)

Expansion chamber

Figure A- 10. - Reefing-line cut ter .

end of the time-delay burn, a pyrotechnic

charge ignited and caused a cutter blade to

sever the reefing line. This same type of

reefing-line cutter was also used to releasethe V H F recovery antennas and the flashing

light, allowing them to deploy 8 seconds

after the main parachutes we re deployed.

BLOCK I I ELS

Changes made to the spacecraft upper

deck between Blocks I and I1 necessitated

modification of ce rt ai n components of the

ELS. The docking tunnel w a s shortened

and the tunnel wa l l w as tapered, significant-

ly altering the shape of the main-parachute

stowage compar tment. A single flowerpot

parachute attachment fitting was incorpor-ated to replace the drogue-parachute attachment fitting and the two main-parachutk

deck- mounted attachment fittings. The ELS components affected by these changes in-cluded: (1) the main-parachute deployment bag and retention system, (2 ) the main-

parachute r is er assembly, (3 ) the drogue-parachute cable- riser assembly, and (4) thepilot-parachute mortar tube and breech assembly.

The general arrangemen t of the Block I1 ELS nstall ed on the upper deck is de-

picted in figure A- l l . The Block I1 installation used the available volume in the forward

compartment more efficiently than did the Block I sys tem. The incorporation of the

flowerpot parachute attachment fitting elim-

inated the large, bulky, two-leg, main-

parachute harness ass embly and theconfluence fitting and provided for much

better stowage of both the main- and drogue-

parachute rise rs .

-Sea recovery

Main -Parachute Deployment Bag

and Retention System

The main-parachute deployment bag

w a s generally reconfigured to fit the shapeof the Block I1 stowage compartment . The

net re sult was a Block I1 bag that wassh ort er and wider than the Block I configura-

incorporation of a side-opening bag instead

of the Block I bottom-opening deployment

bag.

LUprighting bags tion. This change in shape result ed in theunder main parachutes(three places)

arachute Parachute

mortar

Figure A-11. - Block I1 ELS genera l

arrangement.

A- 6



Two- Stage Main Pa rachUte Reef ing

The significant difference between the

original Block II main parachute and the In-

creased capability Block II main parachute

was the incorporation of two-stage reefing.

The two-stage reefing system, illustratedin figure A- 13, reduced the peak opening

loads generated by each of the main para-

chutes . The incorporation of the additional

reefing stage reduced the initial drag areapresent at high-dynamic pressures and then

allowed the parachute to inflate to a larger

intermediate drag area before inflating to

a full-open condition. The fi rs t- and

second-stage disreefings were timed to oc-cur as the dynamic pre ss ure decreased tonear-minimum levels. These times were

established at 6 and 10 seconds afte r initialparachute deployment, or 6 and 10 seconds

after line stretch.

The two-stage reefing sys tem incor-

porated dual reefing rings mounted on the

sk ir t of the parachute canopy. The reefing-

cutter mounting provisions and midgore

reefing concept remained essentially un-

changed from the Blocks I and II configura-

tions. Redundant reefing lines were used

for the first stage because analys is showed

that bypassing thi s stage of inflation couldgenerate loads that would destroy the para-

chute. This redundancy was not needed fo r

the second stage; therefore, only a single

reefing line w a s incorporated.

A typical reefing-line installation ata first-stage cutter position is illustrated

in figure A-14. The first-stage reefing

lines are threaded through the lower holes

of the reefing rings. One of these lines

pa ss es through the 6-second cutter in the

conventional manner; the other line by-passes this cutter and passes through iden-

tical 6-second cutters located on other

gore s. The second-stage reefing line isrouted through the upper holes of the reef -

ing rings, bypassing the 6-second cutters

and passing through 10-second cut te rs

mounted in the same manner on other

gores.

Reefin

l ine B Reefing

cutterReefing cutter Reefing

line A

First stage Second stage

Line A- Shorter length (264 in . )

6-second cutters

Lon yr length 1780 in. )

10-second cutters

Line B

Suspension cutterlineI[

Full open

Figure A- 13.- Main-parachute

two-stage reefing.

Stage U reefing line-

Figure A- 14. Reefing-line installation

for two-stage reefing.

A -9



Although single-stage reefing of parachutes has become a rath er common practi cefor reducing opening loads, the us e of two-stage reefing was virtually untried before itsincorporation in the Block 11 system. This s ystem proved to be effective and reliablein reducing the parachute opening load below what otherwise would have been encoun-

te re d because of the increas ed weight of the CM. The final Block 11 main-parachute

configuration is illustra ted i n figure A- 15.

De p lo y me n t b a g,

m a i n p a r a c h u t e

43.5 i n . 4 TI-

Mal n

p a r a c h u t e

138.5 Ib

L in k a s s e mb ly 1 .3 2 Ib

I I I I

No m in a l d ia me te r : 8 3 .5 ft

N o . o f g o r e s : 68Ca lc u la te d to ta l p o ro s i ty : 1 2 p e rc e n t

Re e f in g

F i r s t s t a g e 7.0 f t DR1 (8 .4 p e rc e n t m id g o re )

Se c o n d s ta g e 2 0 .7 f t DR2 2 4 .8 p e rc e n t m i d p i

F i rs t s ta g e 2 8 5 ft

Se c o n d s ta g e 1080 f12Full o w n : 4200 112

Dra g a re a (a v e ra g e )

Figure A- 15. - Final Block II main

parachute.

Reefing-C tter Modification

The time inte rvals of 6 seconds f or thefirs t stage and 4 additional seconds fo r the

second stage were selected for the reefing

of the main parachute. Because the relia-bility of the mechanical functions of the

8-second reefing cut te rs was amply demon-

st ra ted on the Blocks I and 11 systems, only

the burning ra tes of the pyrotechnic delay

elements wer e modified.

Because two different time-delay reef -ing cutt er s were used in each of the main

parachutes and because both had an identi-

ca l physical appearance , the possibility of

inadvertent interchange of the cu tt er s

existed. To minimize this possibility, ablack oxide was applied to the body of the

6-second fir st-stage reefing cutter s, which,

in turn, were installed in olive-drab cutt erpockets of the parachute. The 10-second

reefing cut ter s retained the untreated

finish and were used in natural-coloredcotton-duck cut ter pockets on the parachu tes .

D rogue-P a rachu e Modifications

The drogue-parachute design fo r theIncreased Capability ELS is a 16. 5-foot-

diameter, 25" conical-ribbon parachute

illustra ted in figure A- 16. Except for the

increa se in size and subsequent drag area,geometric differences in the canopy fr om the original Block I1 design wer e minimal.

A comparative summary of the orig inal Block 11 and the Inc reased Capability Block I1drogue-parachute design is presented i n table A-I.

Several significant departures f rom Block I1 construction methods wer e used toreduce weight, to minimize volume requiremen ts, and to improve ce rta in design fea-

tu re s of the parachute. A substantial saving of weight and volume was accomplished

by using continuous horizontal-ribbon const ruction in much of the canopy. The us e of

A- 10



Deployment bag,

drogue parachute

Nominal diameter: 16.5 fl

No. of gores: 20Constructed porosity 22 percent

Reefed duration: 10 secDrag area reefed: 65 ft2

continuous ribbons with a single-lap s plice

eliminated the added mate ri al previously

required to make multiple-gore s plice s.

A second significant depar ture fro m

the original Block I1 configuration was theincorporation of an integrated suspension-

line/r iser design, with an extension of the

suspension lines forming the riser. The

elimination of the suspension- line- to- ri se r

connection and the use of multiple s tr an ds

of bra ided cord instead of the webbing riserused in the Block 11 construction allowed aweight saving of approximately 1 .5 pounds.

The 16.5-foot-diameter drogue par a-

chutes were reefed at 4 2 . 8 percent of their

nominal diameter fo r 10 seconds. The

10-second reefing cu tte r used i n the drogueparachutes was identica l to the reefing cut-

ter used in the main-parachute second-stage

reefing system.

Figure A- 16. - Final Block 11 drogue

parachute.

TABLE A-I. - COMPARATIVE CHARACTERISTICS OF ORIGINAL AND FINAL

BLOCK 11 DROGUE PARACHUTES

Drogue-parachute characteristics

Nominal diameter , ft . . . . . . . . .

Gores, number . . . . . . . . . . .

Drag area, sq ft . . . . . . . . . . .

Total porosity, percent . . . . . . .*

Gore construction . . . . . . . . . . .

R ise r m a te r i a l . . . . . . . . . . . . .

Suspension-line material . . . . . . .Rated strength, lb . . . . . . . . .

Maximum design-li mit load, l b . . . .

Parachute-assembly weight, lb . . . .

Block I1

13.7

16

68

23

Spliced horizontals

Dacron webbing

Nylon cord1500

12 600

25.4

Increased Capability Block I1

16.

20

114

22.4

Continuous horizontals

Continuation of suspension lines

Nylon cord2 00

17 200

37.4

A - 1 1



L

were modifications to strengthen the pilotparachute. The parachute (fig. A - 19) w a smodified to incr eas e the strength specifica-

tion of the suspension lines from 400 to

600 pounds, and was changed fr om amultiple-ply-webbing riser to the integrated

suspension-line and riser configurationsim ila r to that used on the drogue para-

chute. The multiple-ply-webbing riser de-sign was unsatisfactory because of

susceptibility to improper manufacturing.

In secu ring the plies of webbing, uneven

gathering of a single ply of webbing often

occurred. This condition was difficult to

detect by visual inspection and resulted i n

uneven load distribution between the plies

of webbing. Because of this condition,

the ri se r assembly failed to satisfy the

strength requirements. The design

changes incorporated into the pilot-

parachute suspension lines and riser re-

solved this deficiency.

5

-

-Deployment bag,pilot parachute

.33 Ib

Steel riser1 ".I in: ,I>

1.47 Ib 111 in.I I T

Parachute ty pe ringslotNominal diameter: 7.2 itNo. of gores: 12

Constructed porosity 22 percentDrag area: 24.4 ft2

Figure A- 19. - Final Block 11pilotparachute.

BIock I Forwa rd -Hea t - Sh e ld - Se p a rat io n -Au g m e n t a t i o n Sy s te m

The incorporation of a forward-heat-shield-separation-augmentation parachutesys tem in the Block 11 heat shield was somewhat more complex than the sa me modifica-

tion to the Block I system. The conical shape of the Block I forward heat shield allowed

fo r installa tion of the parachute mor tar assembly directly under the apex of the cover.

With the Block II docking provisions, the forward heat shield assume d the shape of afrustum that required the separation-augmentation mortar assembly to be install ed on

the inner wall of the heat shield. This installation was further complicated by the re-

quirement to delay the morta r fi ring until

the forward heat shield had sufficiently sep-

arated from the CM to allow the parachute

pack assembly to be ejected through the

docking tunnel opening in the heat shield

without impacting the top of the docking tun-

ne1 (fig. A - 20) . This requirement was met

by incorporating a time-delay firing circuit,

activated by lanyards attached to the for-

ward heat shield. The firing curr ent w a stransmitted from the C M to the forward-heat- shield mo rta r pyrotechnic initiator s

through a n umbilical which was deployed

fr om the heat shield as it separated from

the C M . Because the morta r w a s mounted

on the inne r wall of the heat shield, the in-stallation of a ramp above the m orta r was

necess ary to deflect the parachute pack s o

that it would pass through the docking tun-

ne1 opening in the heat shield.

Mortar

car

Figure A - 2 0 . - Block 11 forward-heat-shield morta r installation.

A-1 3



The parachute used w a s a convention-

al Apollo 7.2-foot-diameter ringslo t para-

chute identical to that used to extrac t the

main parachutes. To reduce the loads,

the parachute incorporated fixed o r perma-

nent reefing to reduce its effective drag

area . Because of volume limitat ion in the

CM forward compartment, the convention-

al cylindrically- shaped pilot m or ta r could

not be used. By relocating cer tai n equip-

ment in the forward compartment, it waspossible to install the elliptically shaped

forward-heat- shield mortar assembly

illustrated in figure A-21. The Block II

forward- heat- shield- separation-

augmentation syst em was successfully dem-

onstrat ed during the Increased CapabilityBlock I1 test program.

A- 14

Cover7ing, foamed riser-

L rifice

Pressure cartridge (two each, not shown)

Breech

Figure A-21. - Block I1 forward-heat-

shield mort ar assembly.

LL



presc ribed levels of performance, the failure was formally reported, and a thorough

analysis was performed to determine the exact cause and the necessa ry correc tive

action.

The laboratory qualification te st s performed on the various components of the

Block I ELS are summarized in table B-I. Laboratory testing on the original Block I1sys tem was centered mainly around the changes made between Blocks I and 11. This

testing included the redes igned main-parachute deployment bag, the main-parachutesteel-cable riser, and the redesigned pilot-parachute mor tar .

TABLE B-I. - SUMMARY OF BLOCK I LABORATORY TESTING

Component

Textile materials

Suspension-line connector links

Pilot steel-cable riser

Drogue steel-cable riser

Main-parachute harness

Vehicle harness-attachment fitting

Main- parachute ri se r

Main-parachute retention assembly

Reefing-line cutters

Pilot- mortar assembly

Drogue-mortar assembly

Main-parachute disconnect assembly

B-2

~

Test conditions

Tem peratu re and vacuum

Structural

Structural and abrasion



Structural


Humidity, acceleration, vibration, thermal

vacuum, high tempera u r e

Humidity, acce lera tion, t hermal vacuum, drop,

high temperature, low temperature, physical

strength

Humidity, vibration, t hermal vacuum, high

temperature, low temperature

Humidity, vibration, thermal vacuum, high

temperature, low temperature

Humidity, vibration, thermal vacuum, high

temper ature, low temperature, immer sion



During the original Block II program, emphasis w a s placed on ground testing to

thoroughly evaluate the changes made fr om the Block I design. These ground te st s

were used extensively to obtain comparative performance data on several main-parachute-deployment-bag configurations being considered. The ground-tes t approachconsiderably reduced the number of required ae ri al drop tes ts and reduced the program

cost.

Following the decision to modify the Block I1 ELS to increase its capability to re -

cover the heavier CM, the establishment of ground-test requ irement s was necessary.

Because each component of the ELS had been qualified previously fo r u se on manned

spacecraft, the extent to which ret es t was necessary w a s governed str ictly by the na-

tu re and the extent of individual component redesign. Fo r example, modificationswere made to the reefing cutte rs to var y the delay time fro m 8 to 6 and 1 0 seconds.

This change affected only the pyrotechnic time-delay e lement in the cu tter , not the

stru ctur e o r actuating mechanism. Therefore, the redesign reefing cutt ers were sub-

jected only to the mission-environmental tes t conditions that could influence the pe r-formance of the time-delay element, that is , accele ration, high and low temperature ,

and high humidity.

Those components requiring major redesign, such as the drogue-parachute

mortar assembly, were subjected to extensive laboratory tests. In such cases, the

verification of the structural adequacy, performance characteristics, and overall re-liability of the redesigned components over a wide range of miss ion conditions was

necessary. Much of this laborato ry work had to be accomplished before integrat ion of

the part icular components into the aerial drop tests.

AERIAL DROP TESTS

The aerial drop tes ts were conducted at the A i r Forcernavy Joint Parachute TestFacility , El Centro, California. This facility was ideally equipped for Apollo-type drop

testing because it provided a fully instrumental tes t range, an onsite shop, and adminis-

trat ive office space. Sources for data acquisition included ground- to-a ir and air- to-a ir

photographic coverage, ground cine- theodolite track ing stations, and a telemetry

ground station. In addition, the El Centro test facility provided many of the drop air-cr af t and the test-vehicle ground-handling equipment. A ll BP vehicle drop tests were

made from a modified C-133A air cr aft provided by NASA and manned by cont ractorpersonnel.

Th re e basic types of vehicles used in th e aeri al drop te sts included an instru-

mented cylindrical test vehicle (ICTV), a parachute tes t vehicle (PTV), and the boiler-

plate (BP) test vehicles. Often re fe rre d to as a bomb-drop vehicle, the ICTV w a ssimple in concept, rugged in construction, and low in cost (fig. B-1). The ICTV was

used on tests where the CM int erf ace was not a consideration and where it providedsimplicity; minimizing test-preparation time. These vehicles were usually equipped

for tel eme try and m5aa rd photographic dzita acquisition.

B- 3



Figure B-1. - Instrumented cylindrical test vehicle.

Well suited for testing at the total-system level, the PTV w a s designed to simu-

late the major features of the spacecraft upper deck (fig. B-2). Below the deck level,

the PTV was a simple cone shape of sturdy construction to eliminate impact damage.Because the total drag area of the PTV was much less than that of a CM, this vehicle

was well suited for conducting system-level tests at dynamic p re ss ur e conditions above

the limits for spacecraft.

B-4



Figure B-2. - Parachute test vehicle.

The BP test vehicle was the most elaborate spacecraft- representative tes t vehicle

used in the parachute drop tests (fig. B-3). The test accurately simulated the CMweight, the center of gravity, and the geometric profile. In addition to testing the totalparachute recovery system, the tes t could incorporate the forward-heat-shield jettison.A l l the various components interfacing with the ELS (location aids, vehicle-uprightingbags, and other spacecraft components) that could affect, or be affected by, the para-chutes were installed on the BP. The BP was the fi rs t vehicle in which t h e spacecraft-

configuration ELS sequence controller performed the system-sequencing functions.Instrumentation in the BP w a s similar to that used on the PTV, consisting primari ly of

telemetry and onboard cameras.

B-



Figure B- 3. - Boilerplate test vehicle.

BLOCK I DEVELOPMENTAL D R O P TESTS

During the Blocks I and 11programs, the aerial drop tests were classified as beingeither developmental te s ts o r qualification tests. Developmental tests were furthergrouped into individual test series according to specific test objectives.

The aeria1,drop tests made during t h e Block I developmental program a r e illus-

trated in figure B-4. During the first year of the Block I developmental effort, manysingle- main-parachute ICTV drop tests were made to evaluate various main-parachute

design concepts. In 1963, much of the developmental testing consisted of multiple



e r i e s1964

F M A M J J A S O N D J

1

3

6

7

13

17

18

24

26

28

29

40

41

44

46

48

50

1% 5

F M A MSe r ie s o b je c t i v e s

P r e l i m i n a r y d e v e l o p m e n t a l tests , o n e

Developmenta l tests, o n e m a i n p a r a c h u t e

Developmenta l tests, o n e m a i n p a r a c h u t e

Developmenta l tests, t h r e e m a i n c l u s te r

Developmenta l tests , t h r e e m a i n c l u s t e r

D r o g u e tests, o n e a n d two p a r a c h u t e s

D r o g u e tests, o n e p a r a c h u t e

D r o g u e tests, o n e a n d two p a r a c h u t e s

M o d i f i e d m a i n p a r a c h u t e i n c l u s t e r s

Sy s te m test

M a i n - p a r a c h u t e d e s i g n - v e r i f i c a t io n tests

M a i n - p a r a c h u t e i m p r o v em e n t tests

M a i n - p a r a c h u t e i m p r o ve m e n t tests

M a i n - p a r a c h u t e i m p r o v e m e n t t e s t s

M a i n - p a r a c h u t e s t r e n g t h v e r i f i c a t i o n

D r o g u e - p a r a c h u t e d e s i g n v e r i f i c a t i o n

B P to ta l -s y s te m d e v e lo p me n ta l tests

m a i n p a r a c h u t e

1%2

J A S O N D

T

m

m nmm

V

1963

J F M A M J J A S O N D

T T ? W

W

v v

v v

v v v

V

W l

AA A

V

v v .v

M A A &

T lCTV

v P N

A B P testv e h i c l e

7

T T T W

T T 7

T T T T T

T T T T T V T T

m

v v v c

A A A A

T T

7 0

Figure B-4. - Block I developmental drop-test summary.

parachute (clu ster) te st s and the higher-level system tes ts. During these tests , the

main-parachute-cluster interfe rence problems became a concern. Severa l two-main-

parachute ICTV drop tests were conducted during the first 6 months of 1964 to evaluatethe main-parachute modifications incorporated to improve clust er inflation. Following

a limited se ri es of total-system verification tests, the Block I developmental drop test

w a s concluded early in 1965 with drop te st s to demonstrate the ultimate s trength capa-

bility of the drogue- and main-parachute designs.

A s the time approachdd for the qualification ae ri al drop tes ts to begin to supportthe spacecra ft flights, certain qualifiable configuration components apparently were

not going to be available f o r the initial tests. Problems encountered during the lat ter

pa rt of the developmental prog ram required that so me late changes be made to certa in

components; time was insufficient to incorporate all these changes in the initial sys tem-

qualification drop test s. Although a basic rule fo r qualification testing states that items

subject to qualification be of the spacecraf t configuration, compelling schedules neces-

sitated initiation of total-system testing with certain it ems that were not yet in a quali-

fiable configuration. These it em s included the drogue and pilot mor ta r cart ridges,the main-parachute disconnect and cartridge, and the reefing-line cutters . The use of

thes e in teri m components was permitted on the basis of similar ity to final design andon the fact that the flight items wer e to be subjected to labora tory qualification tes ts.

The plan w a s to phase the final-design components into the qualification drop -test

program at the earlies t date.

B- 7



BLOCK I SYSTEM-QUAL1 F IC AT IO N DROP TEST

From May 6, 1965, to February 24, 1966, 12 aer ial drop tests wer e made tocomplete qualification of the Block I ELS and to rate the system suitable for manned

flights. A summary of this progr am is presented in table B-11.

T A B L E E-II. - SUMMARY OF BLOCK QUALIFIC ATION DR OP TEST S

60-1 1 5-6-65 1 N o r m a l e n t r )

6 2 -1 1 6-3-65 /“E1 i ude

b 6 2 -3 8-5-65 P a d a b o r t

6 2 -2 I 8-19-65 IMediuni -

a l t i t u d ea b o r t

62-3A I 9 - 2 3 - 6 5 I P a d a b o r t

‘62-4 [ 1 0 -8 -6 5 INo rm al en t ry

a l t i t u d ea b o r t

a l t i t u d e

62 -9 1 2-24-66 lkiigh-

a l t i t u d ea b o r t ( o n ed r o g u e )

a D y n a m i c p r e s s u r e . b T e s t 62-3 p r o g r a m e r p a r a c h u t e fa i l ed t o d i s c o n n e c t . ‘ T e s t 6 2 -4 f a i l e d t o m e e t r e q u i f e d t e s t c o n d i t i o n s

The drop-tes t conditions we re established to demonstrate the system under asmany operational flight conditions as possible. The following te st conditions were

selec ted for the qualification drop tests.

1. Normal-entry simulations - three tests

2. High-altitude-abort simulation - two tests

3. Medium-altitude-abort simulations - two tests

4. Pad-abort simulations - tw o tes t s

5. High-altitude-abort simulat ion with one drogue parachute - one tes t

Although 10 te st s were planned in th is series, 1 2 te st s we re actually conducted because

of fai lu re on two occasions to achieve the des ired test conditions.

B-



In these tests , the se rvi ce ceiling of the C-133 drop-test aircraft (30 000-feet

maximum alti tude) and other limitat ions would not allow complete duplication of theoperational flight modes. Fo r example, i n an operational normal entry o r high-altitude

abor t, the drogue parachutes would normally be deployed by c los ure of the high-altitude

baroswitches at approximately 24 000 feet. In a drop- tes t simulation of these opera-

tional modes, the BP test vehicle w a s released at 30 000 feet. To allow fo r a minimum

auxiliary-brake parachute- stabilization interval and some- inite free-fall interval to

achieve the requi red dynamic pr es su re condition, drogue-parachute deployment (initi-ated by an auxiliary events controller) had to be delayed to altitudes moderately below

the normal 24 000-foot level. A s a result, two compromises were made in the total

per formance of the ELS, ha t is, recovery was not initiated by the sequence-controller

baro metr ic switches, and the normal drogue-parachute operating interval w a s reduced

from a normal 50 to 55 seconds to approximately 25 seconds. The first compromise

w a s reconciled by monitoring the sequence control lers for prope r c los ure of the baro-

metr ic switches, thus acquiring evidence of sat isfactory performance. Analysis

showed that the lack of the full drogue interva l would not have a significant effect on

the t es t conditions at the ti me of main-parachute deployment because the re would be

no substantial improvement in vehicle dynamic stability a fte r the 25-second test inter-

val. Secondly, the sho rte r drogue interval represented a more demanding condition

pertaining to total-system operation than t ha t which would be experienced in a compara-ble spacecraft operation.

Although desir ed dynamic pr es su re and vehicle attitude could be programed intothe tests, a representat ive flight-path angle could not be achieved. Also, the marginal

stabili ty of the BP vehicle s made the acquisition of desi red initial a ttitudes and C Mdynamics at the end of long free-fall int erval s very difficult. A t the end of the free-

fall interval, these test limitations generally resulted in vehicle dynamics more s eve rethan those predicted for an actual mission. Because the test conditions were morese ve re than those the spacecra ft would experience, the tests were judged as a satisfac-

tory demonstration of the sys tems capabilities.

W i t h the exception of a minor modification in the main-parachute retention sys-tem incorporated in the last four tes ts, the remaining six qualification drop tests wereconducted with the fina l Block I ELS configuration.

BLOCK I DEVELOPMENTAL DROP TESTS

The major changes fr om the Block I to the Block 11ELS concerned the redesigned

main-parachute deployment bag and retention system, the stee l-cable main-parachute

riser, the flowerpot parachute-attachment fitting, and the modified pilot-parachute

mor ta r. The Block 11 developmental drop-test progr am w a s oriented to demonstrate

that the se modifications did not degrade t h e strength o r the performance of the sys temin any way.

The developmental drop-test progr am was originally planned as a se ri es of thre e,single, main-parachute PTV tes ts. However, during the second test of the serie s, astrength deficiency was found in the main-parachute canopy, and three inte rim testswere conducted to demonstrate the adequacy of the f i x to the main parachute before

conducting the final test of the developmental test se ri es .

B-9



BL OCK I I Q U A L1 F I C A T I O N D R O P TESTS

T e s tn u mb er

1 3 - 4

7 3 -1

73-3

7 3 - 5

From October 19, 1966, to January 17, 1967, a series of four total-system

aerial drop te st s was conducted using the BP-6 vehicle, modified to the Block 11 con-

figuration. This se ri es of tests (table B-111) completed qualification on what was then

believed to be the final ELS. Before entering this test ser ies , a basic ground rule was

established stating that only qualified o r qualifiable parachute system components andinstallation speci ficat ions would be used in the test series . Thi s policy was maintained

throughout the tes t se rie s; in contr ast to the Block I test series, no configuration

changes were made to the ha rdware during the Block 11 qualification drop-test program.

~~

P i l o t m o r t a r f i r earach u t e d i s con n ect Drogu e mort ar f i reR e c o v e r y Forward-

Simulat ion weight , ~~~~~d Alt itude, qa, Tim e, Alt itude, qa, Tim e, Alt itude, qa, Time ,ste

Ib jet t ison It x IO3 lb/ft2 It x IO 3 lb /f t2 It x l o 3 lb/ft2

10-19-66 High-alt itude 1 1 000 N o 2 6 . 8 3 7 . 6 2 4 . 7 2 2 . 5 1 1 4 . 8 3 6 . 4 10.8 50. 7 5 . 6abort

12-1-66 Pad abort with 11 78 5 Yes 8 . 9 4 6 . 4 7 3 . 0 8 8. 5 5 8 .8 7 4 . 8 7 . 9 6 8 . 4 7 6 . 8short drogueinterval

_ _12- 20- 66 M ed iu m- al t i t u d e 1 1 78 5 Yes 1 9 . 2 4 6. 7 4 9 . 7 1 8. 7 5 3 . 2 5 1 . 5 4 . 4 4 9 . 7 1 0 1 . 8

abort withextendedd rogu einterval

1- 17- 67 Normal en t ry 1 1 7 8 5 Y e s 2 5 . 0 70 .1 29 . 5 2 4 . 4 7 6 . 7 3 1 . 3 1 0 . 6 51 . 6 8 0 . 4

TABLE E-111. - SUMMARY OF BLOCK I1 QUALIFICATION DROP TES TS

'Dyn amic p res s u re .

A second basic difference between the Blocks I and I1 test program s was anattempt in Block 11 to eliminate the off-limit and over tes t conditions preva lent in the

Block I series. Two of the Block I tests had to be repeated, and other tes ts were

difficult to rationalize as fully valid because of their severity. In the Block I effort,

long free -fall periods, used to obtain high dynamic pr es su re s, often result ed in a very

unstable vehicle and higher- than-desired dynamic pr es su re s. In the Block 11 effort,

smalle r programer parachutes were used; they remained attached to the vehicle andremained operative until attaining the des ired test conditions and attaining the initiation

of the recovery sequence. Thi s technique permitted control over the attitude of the

vehicle and over body ra te s to the point where the ELS unctions began. This techniqueresul ted in near-nominal and some times below-nominal conditions fo r ce rta in flight

modes; however, the te st s we re far mor e repres entati ve of spacecraft conditions than

were many of the Block I tests.

B- 10



The Block II qualification drop t es ts were also cha ract erized by two added opera-

tional simulations not demonstrated i n Block I. The first simulation involved an ear lymanual main-parachute deployment whereby the crew elects to override the automatic

sequence. This operation results i n a short drogue-parachute interva l. The second

simulation concerned the main-parachute inhibit mode whereby the crew elects to delay

automat ic main-parachute deployment and to extend the drogue interval. This tech-

nique could be used to avoid drifting back to a land landing in the event of a near-pad

abort.

1967

One aspec t of the Block II qualification drop tests, which might be considered asbeing off -limit, concerned test-vehicle recovery weight. Although the specifica tions

still reflected a maximum vehicle weight of 11 000 pounds at the ti me of the tests, the

proj ected weight for Block II spacecraft had risen to 11 785 pounds. The thr ee final

tests were conducted with the vehicle at this increased weight.

1968

The resu lts obtained fro m the Block I1 qualification drop tes ts demonstrated the

capability of the Block I1 ELS to land the CM safely under the conditions stipulated in

the specifications.

IN C RE A SE D C A P A B I L l T Y B LO C K I DEVELOPMENTAL DROP TESTS

The a er ia l drop te st s conducted in support of the Increased Capability Block 11prog ram began on July 10, 1967, and continued unt il July 17, 1968, when the finalparachute drop test w a s completed at El Centro, California. The developmental and

design-verification tests were established as five series, identified as 80, 81, 82, 83,and 84 (fig. B-5). The individual tests in each se ri es were identified by dash numbers

(80-1, 80-2, et cetera). A 99 ser ies w a s lat er added to augment the drogue-parachutetest.

__

Series

~

80

81

a2

a3

84

w-Reefing evaluation, single

parachute

Reefing evaluation, iwo-parachute cluster

Main-parachute strengthverification

Main-parachute clustertest, missed second-stage ree fing (one ofthree parachutes)

Total-system test, twodrogues, two and threemain parachutes

Drogue-parachute strengthverification, two-para-

chute cluster

T T T T T T T

T T T T

Y T

T ICN

v PN

Y T

Vv T T T

I

T T T T T T T

T T T T

Y T

v v

Figure B- 5. - Increased Capability Block II developmental drop-test summary.

B-11



The 80 and 81 se ri es we re quite simil ar in that both were a imed at developing

the two-stage main-parachute reefing system. The 80 se ri es was single main-parachu te tests; on the other hand, the 81 se ri es used cl ust er s of two main parachutes.

In the 80 seri es, Seven single parachute tes ts were conducted with the pri mary objec-

tiv es being to confirm the effective canopy drag areas and load estimates, to determine

f i l l rate s, to establish the time interval for the reefed stages, and to dete rmine the

second-stage reefing-line load. Four 81 series cluster tests were conducted to evalu-ate staged reefing with a clust er of two parachutes, representing the design condition,

to establish reefed load sharing, to dete rmine quantitatively the effect of nonsynchro-nous deployment and disreef , and to obtain fur the r verification of selected reefing

parameters.

Using single main parachutes and the ICTV, the 82 se ri es were verification tes ts

of canopy strength. This ser ie s consisted of four tes ts conducted to demonstrat e the

ultimate load-carrying capability of the main parachu te in the first- stage reefed con-

dition, the second-stage reefed condition, and the full-open condition.

The 83 and 84 series were simil ar because both were combined drogue and clus-tere d main-parachute te st s using the PTV. The 83 se ri es was planned primarily asdevelopmental type t es ts to est ablish drogue reefing para me te rs and t o obtain additional

performance data on main-parachute clu ste rs . The planned 84 series w a s to have beenconducted with final spacecraft-configuration hardware and w a s to have included drogue-

parachu te ultimate-strength verification tes ts. Because of delays in the te st schedule,the unavailability of spacecraft-configuration hardware, and'the close s imil arity

between the objectives of the 83 and 84 ser ie s , only one of the 83-ser ies te st s was

actually conducted to demonstrate the effect of a miss ed second-stage reefing in one of

a cluster of three main parachutes. The test res ults supported an analysis showing

that the total axial load generated by a single main parachute (in a three-parachuteclus te r) would not exceed the s tru ctu ral capability of the parachute i f it prematurely

disreefed from, o r bypassed, the second-stage reefing.

The 83 and 84 se ri es were followed by the 99 se ri es of supplementary drogue-

parachute-strength verification tests, which included one test to demonstrate drogue-parachu te deployment at an alti tude of 40 000 feet. This test simulated a condition

wherein the astronauts would initiate an ea rly drogue-parachute deployment to stabiliz e

the CM.

IN C RE AS ED C A P A B I L I T Y B L O C K I I Q U A L I F I C A T I O N T E S T S

On April 4, 1968, the first of a se ri es of seven qualification aerial drop tes ts

was conducted on the final configuration of the ELS. This series was completed onJuly 3, 1968, approximately 1 year after for mal approval of the ELS ncreas ed capa-

bility program and 3 months before the first flight of the syst em on a manned Apollospacecraft.

During the qualification tes ts, each test ed component was identical to the space-

cr af t production design with one minor exception. During the th ree final tests, strain-

gage link assemblies were incorporated in the main-parachute ri se r to obtain parachuteload data under simulated operational conditions of the spacecraft.

B- 12



The Increased Capability Block 11 qualification program consisted of the following

tests (table B-IV).

85-6

85-5

1. Two pad-abort simula tions were conducted; one test demonstrated t h e by-

2. The second test conditions pertained to high-altitude-abort simula tions with-

passed drogue condition. One test included jettison of the forward heat shield.

out the forward heat shield. Both te st s used only one drogue parachute, and one te st

used only two main parachutes.

5-14-68 Pad abort 1 3 0 0 0 No _ _ _ - _ _ _ _ _ _ _ _ 1 0 . 2 9 2 . 3 3 . 0

(drogueby pa s s )

6-6-68 Hig ha l t i tude 1 3 000 Y e s 2 9 .0 4 2 .7 1 5 .0 1 9 .6 170. 5 36 . 5 4 .2 6 3 .5 8 4 . 8

abort (one

3. The th ird test conditions concerned three normal- entry simulations, all

incorporating jettison of the forward heat shield. Two of these tests demonstrated

single-drogue parachute conditions; one of these te st s demonstra ted the syst em with

a 1 3 500-pound vehicle recovery weight. The apex-forward at titude of the vehicle,

required to achieve the desi red test conditions, prevented the use of the forward-heat-

shield sys tem during thr ee of the tests.

dr o g ue )

The drop tests made during the qualification series were dispersed as widely as

possible over the potential operational envelopes for the drogue and main parachutes(figs. B-6(a) and B-6(b)). Included in figure B-6 ar e the test conditions at which the

drogue and main parachutes have been demonstrated during the total system-level (BP

vehicle) tests. Limitations imposed by t h e drop air cr aft preven ted drogue-parachute

deployments at the higher altitudes; however, the high-dynamic-pressure conditions

were w e l l demonstrated. For each of the qualification te st s, the conditions obtained

were very clo se to des ire d values , and no discrepancies of sufficient magnitude wereencountered to invalidate the test o r to prevent fulfilling the tes t objectives.

1 85-4 1 6 - l i - 68

On the basi s of the performance of the parachute sys tem during each of the

qualification drop test s, and on successfu l completion of l aborato ry qualification atthe component and lower-assembly level, the Increased Capability Block II ELS w a s

verified fo r use on manned Apollo spacec raft.

2 5 , f i I 1 9 .6 2 9 .1 2 4 .9 9 2 .5 3 0 .9 4 .3 6 5 .1 9 6 . 5

I I I I I IN o r n i a i e n t r y

(o ne dr o me )

T A B L E B-IV. - SUMMARY OF INCREASED CAPABILITY BLOCK I1 QUALIFICATION DROP TESTS

85-7 7-3-68 Hig ha l t i tude 1 3 OOO N o 28.9 42. 0 20.1 22. 5 149. 5 3 5 .4 4 .4 6 3 .3 9 1 .6

abort (onedr o g ue a ndtwo ma ins )

a D w a r n i e p r e s s u r e .

B-13



40000

r 30000-

u

c-

20000-

10000 -

' 0 o BP test points/ Normal entrym , " and hiah-

High-altitude abort

~

,1 .2 . 3 . 4 .5 .6 .7Mach number

.2 . 3 . 440 .1

Mach number

(a) Drogue parachute. (b) Main parachute.

Figure B-6. - Deployment envelope.

B- 4



MSC-05805

APPENDIX c

APOLLO 15 MISSION

MAIN PARACHUTE F A I L m

Anomaly Report No. 1

PREPARED BY

Mission Evaluation Team

APPROVED BY

James A. McDivitt

Colonel, USAFApollo Spacecraft Program

NATIONAt AERONAUTICS AND SPACE ADMINISTFNTION

MANNED SPACECRAFT CENTER

HOUSTON, TEXAS

December 1971

c-1



M A I N PARACHUTE FAILURE

The th re e main parach utes of t h e Apollo 15 spacecraft deployed and

in f l a t ed p roper ly at approximately 1 0 000 feet, al ti tu de . Films show t ha t

a l l three parachutes disreefed and opened fully i n th e proper sequence.

The spacecraft and i t s parachutes were obscured by clouds a t about 7000f ee t a l t i t u d e .

one of t he th re e main parachutes was def la ted as shown i n f ig ur e 1. The

spacecraft and parachute system descended i n t h i s configurat ion t o water

land ing. The t h r e e para chute s were disconnected and one of t h e good main

parachutes was, recovered. The fa i lu re occurred abruptly. A t about the

a l t i t ude and t i m e of th e fa i l u r e , the forward heat sh ie l d w a s i n close

proximity t o th e s pacecraft and th e re act ion contr ol system prope l lan t

dep le t ion f i r ing w a s about completed. An inspect ion of the recovered

parachute showed one of t h e s i x r i se r l inks had a broken stud and three

other s had cracks. The inv es tig ati on of t h e f a i l u r e w a s , therefore , fo -

cused on th e rea ct ion contr ol system propel lant de plet ion f i r in g, th e

forward heat sh i e ld , and the fa i l ed l i n k s .

Upon emerging from t h e clouds a t about 6000 f e e t a l t i t u d e ,

DESCRIPTION AND SYSTEM OPERATION

The e ar th landi ng system dec ele rat es and s t a b i l i z e s t he command mod-

ule t o safe condi tions f o r landing. The l a n d i n p sequence i s i n i t i a t e d a t

a nominal alti tude of 24 000 fe et wi th je t t i s on i ng of the forward heat

sh ie ld . Immediately a f t e r se par ati on of t he heat s hi el d from th e command

module, a 7.2-foot-diameter para chute is mortar-deployed from th e forward

heat shiel d . This parachute prevents i n i t i a l recontact between the heat

sh i e ld and t h e command module.

Two 16.5-foot diameter con ical ribbon-type drogue parachut es ar e mor-

tar-deployed 1 .6 seconds a f t e r forward heat s hi el d je t t is on . The drogue

parachutes are deployed i n a reefed condition and, 10 seconds la ter , in -

f l a t e t o th e f’ully open configuration. The drogue parachutes ar e rel ea sed

from the command module a t an al t i tu de of about 11 000 f e e t . A t drogue

parachute disconnect, t hr ee 7.2-foot diameter r i n r - s l o t pi lo t parachutes

ar e mortar-deployed. The p i l o t parachutes provide th e force necessar y t o

re le as e th e main parachute re ten tio n system and p u l l the main parachute

pack assemblies from the upper deck. A s the mair, parachute packs are

pu ll ed away from the command module, t he parachute.. a re e xt ra c te d from

t h e i r deployment bags. Each main parachute in f l a t e s through two re ef in g

stag es t o th e f’ully open configuration. The th re e m a i n parachute assem-

b l i e s ( f i g . 2) de ce le ra te t he command module t o th e f i n a l descent veloci ty .

Each main parachute canopy consists of twelve rings of s a i l s with

each r ing d iv ided in to 68 gores, The canopy terminates in 68 suspension

c-3



F ig t i re 1 - Spacecraf t descet id ing wi t h one main parachute fa i le d

c-4



7a b r i c r i s e r

Stee l cab le r i se r

Ma in parachute

cznopy

l i n k

se r

F a b r i c r i s e r

F igure 2 . - Parachute system c onf igu rat ion.

c-5



l ines which are a t ta c h ed by s i x s t e e l co nn ec to r l i n k s t o s i x i n d i v i d u a l

l e g s of a f a b r i c r i s e r . The s i x l e g s of t h e f a b r i c r i s e r c ov er ge i n t o

a s in g l e l e g w hich c onne ct s t o t h e e nd o f a s t e e l c ab l e r i s e r . The t h r e e

s t e e l c a bl e r i s e r s of t he p a r a c hu t e s yst em cove rge a nd a t t a c h t o t he com-

mand module through t h e par ach ute attachment and disc onn ect assembly.

DISCUSS1ON

A d i s cu s s io n of t h e a n a l y s i s , t e s t s , c o n c l u si o n s, a n d c o r r e c t i v e

a c ti o n s a r e c on ta in ed i n t h i s r e p o r t . A l l t im es shown i n t h i s r e po r t

ar e elap sed time from range zero . Range zero i s t h e n e a re s t i n t e g r a l

second pr ior t o l i f t - o f f .

FLIGHT DATA

Per t i nen t da t a and th e sequence of events a r e shown i n f i gu re 3 .

The d a ta showed no abnormal con di t ions o r events p r i o r t o th e fa i l u re .

About 3 .5 seconds be fo re th e f a i lu re , th e rea c t i on con t ro l sys tem man-

i f o l d p re s su r e a b r u p t ly i n c r e a s e d t o a new l e ve l , i nd i c a t i ng t h e r egu l a -

t o r had c losed because a l l t h e o x i d i z e r w a s expe l led from th e ta nk s . The

fuel , however , w a s s t i l l be ing e xpe l l e d a nd was c a l c u l a t e d t o have bee n

deple ted about 4.7 se co nd s a f t e r t h e o x i d i z e r d e p l e t i o n .

on a determinat io n of about 7 pounds of f u e l remaining a t oz id ize r deple -

t i o n .

purge was i n i t i a t e d by th e crew.

u n t i l some t ime a f t e r th e purge . )

f i g u r e 3 by th e abrupt dec rease i n sys tem pre ssu re .

T h i s w a s based

About 8 seconds a f t e r t h e f a i l u r e , t h e r e a c t i o n c o n t r o l s ys te m

(The crew w a s unaw are of t he f a i l u r e

The t ime of t h e purge i s i n d i c a t e d i n

The forces ac t i ng upon th e space c ra f t at t h e t ime t h e pa r ac hu t e

f a i l e d were determin ed from body-mounted acc ele rom ete r da t a . The force

vector change a t t h e p a r ac h ut e a t t a c h p o i n t w a s :

T hi s r e s u l t a n t v e c t o r l o c a t e s t h e f a i l e d p a r ac h u te as shown in f i g-

The computed force vector w a s su bs ta nt ia te d by body-mounted r a t ere 4 .gyro da ta .

PHOTOGRAPHIC DATA

Figure 5 shows th e sp ace cra ft and lower par ach ute system when t he

s pa c e c r a f t was r e l a t i v e l y c lo s e t o l a nd ing . The f o l low ing obs e r va t i ons

r e s u l t e d f rom s tudy of t h i s f i g u r e and o th e r pho tog r a ph i c d a t a .

C -6



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F i g u r e 4. - Parachute locat ion a t t ime of fa i lu re

c-9



a. A p pa re nt ly t h r e e o f t h e s i x l e gs o f t h e f a b r i c r i se r were t a k i n g

t h e l oad .

b .

c .

There w a s no significant canopy damage observed.

About two- third s of t h e suspensi on l i ne s appeared t o be miss ing .

CREW OBSERVATIONS

The Command Module P i l o t , wh ile lo oki ng thro ugh t h e lef t- ha nd rende z-

vous window, wi tness ed th e j e t t i s on in g o f t h e h e at s h i e l d and t h e deploy-

ment of t he drogue par achu tes; both fun ct ion s appeared nominal. A f e wseconds a f t e r drogue parac hute r e l ea se , t h e Command Module P i l o t observed

t h e deployment of t h e main parachutes i n t h e r ee fed cond i t i on . The para-

chutes maintained t h e r e e f e d c o n d i t i o n , a f t e r w hich d i s r ee f i n g occu r red ,

and a l l three pa rachu t e s i n f l a t ed no rm a ll y.

crewmen were performing var ious cockpi t t as ks which inc lud ed t h e r e a c t i o n

c o n t r o l s ys te m d e p l e t i o n f i r i n g . After t h e complet ion of the f i r i n g , t he

Command Module P i l o t o bs er ve d t h a t t h e pa rachu te had f a i l e d . A t t h e samet ime , he not ic ed t h e normal brown oxi diz er c loud from t h e purge.

func t ions th rough l anding were nominal except tha t t h e l and i ng w a s harder

than normal .

Fo l l ow i ng t h i s even t , t h e

Other

RECOVERY FORCES OBSERVATIONS

T he p i l o t s and c o p i l o t s o f t h r e e of the recove ry he l i co pt er s (Swim 2 ,

Photo, and Relay) observed t h e sp ac ecr aft between main pa rach ute opening

and land ing. The lo ca t io ns of t h e recovery forces at t h e t i m e of t h e anom-

a l y are shown i n f igure 6 .show that the anomaly occurred a t approximately 6000 feet and t h a t t h e

forward heat s h i e l d w a s f a l l i n g i n c l os e p ro xi mi ty t o t h e s p a c e c r a f t , b u t

s l i g h t l y o ut of plane from th e observer ' s v i ewpoin t .

observed t h e brown ish c loud and pu f fs of wh ite smoke which normally o ccu r

dur ing t h e r ea c t i on con t ro l sy st em pu rge.

The observat ions of t h e three he l i cop t e r c r ew s

The he l i cop t e r c r ew s

The swimmers succ es s f u l l y r ecove red one o f t h e main parachutes and

t h e forward heat sh i e l d , a l t hough t h e forward hea t sh ie ld parachute wassubsequen t l y l o s t du r i ng t h e recovery opera t ions . An exper i enced para-

ch u t i s t who w a s a member of the recovery team s t a t e d t h a t t he forward

heat s h i e l d parachu te appeared t o be i n good condi t ion, with n o t e a r s i n

t h e canopy nor broken shroud l i n e s .

c-11



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c-12



RECOVERED PARACHUTE INSPECTION

The rec ove red main para chu te which had not fa i l t ?d w a s i nspec ted and

t h e r e s u l t s o f t h e i n s p e c t i o n w er e:

a. Nine consecu t ive suspe nsion l i ne s were cut approx imately 1.9 feet .above t h e r i s e r / su s pens i on - l i ne connec to r l i nk . A dd i t i on a l l y , some 2 5

f e e t of l i n e w a s m i ss ing f rom each .o f t he cu t su spensi on l i n e s .

were cu t by N a@ swimmers t o f r e e th e parachute from the command module. )

(L ines

b . Gore 11 of pane l 9 had a t ea r approximately 12 inches by 1 2 i n -

ches which di d not appea r t o have been caused by s t r e s s o r f r i c t i o n b u r n -

i n g , but probably occurred dur ing r e t r i e v a l .

c . Gore 55 o f p a n e l 5 had an 8-inch ho r i z on ta l t e a r which a l so ap-

p e a re d t o be . t h e r e s u l t of r e t r i e v a l o r p o s t f l i g h t h a n d l in g op e r a ti o n s

r a t h e r t h a n t h a t o f f l i g h t d amage,

d. There were numerous small (1/ 16 -i nch t o 1 / hc i nch ) ho l e s . i n t h e

canopy. (These were probably caused by po s t f l ig h t handl ing . )

e . The p i l o t pa rachu t e and r i s e r were i n e x c e l l e n t c o n d i t i o n , a n d

t h e main para ch ute deployment bag had on ly minimal (no rma l) damage.

f . The canopy w a s s t a i n e d w i t h o i l and grease.

g . A broken r i s e r / su s pens i on - l i ne connec to r l i n k w a s found a f t e r

the pro tec t ive Dacron boot i e had been removed ( f ig . 7 ) .

h . Evidence of high tempe rature was noted on the Dacron r i s e r pro-

t e c t i v e c ov er ( f i g . 8) and th e Dacron connec tor l i n k boo t i e .

FORWARD HEAT SHIELD INSPECTION

The ov er a l l appearance of th e forward hea t s h i e l d was c o n s i s t e n t

w i t h t h a t of t h e forw ard hea t s h i e l d s p rev i ous l y r ecove red . The heat

s h i e l d w a s examined for evidence of for eign mate r i a l and none w a s f’Jund.

The fo l lo wing sp ec i f i c po i n t s were no ted :

a . The l ea d in g edge s e a l was not damaged.

b . Parachute cab le r i s e r marks were pres en t on th e ou t s i de of the

forward hea t sh ie ld . These marks occurred as a r e s u l t o f t h e normal fc r -

ward he at s h ie ld parac hute deployment.

c-13



C-15



Forward Heat Shield

T r a j e c t o r y a n a l y s i s . - A t r a j e c t o r y a n al y si s was performed us ing s i m -

u l a t i o n s t o d e te rm in e i f t h e f or wa rd he a t s h i e ld c ould have c o n t a c t e d t h e

main pa ra ch ut es . The sim ulat ion s were based on t h e point-mass equ atio ns

of motion, which used t h e known mass and aerodynamic c ha ra c t e r i s t i c s of

t he f o r w a r d he a t s h i e ld an d sp ac ec ra f t parachute sys tems and t h e measureddownrange and crossrange winds.

The s imula t ions and analys is showed tha t , at approximately 150 sec-

onds a f t e r t h e 2 4 000- foot a l t i t u d e had been reached , t he spa cec ra f t and

forward hea t sh ie ld were a t t h e same a l t i t u de o f a bou t 5700 f e e t w i th amiss das tance of approximate ly 150 f e e t . This co r r e l a t e s wi th observa-

t i o n s of t h e r ec o ve ry p e rs o n ne l . F u r t h e r , t h e a n a l y s i s i n d i c a t e s t h a t ,

at l and ing , th e spa cec ra f t and t h e forward hea t sh ie ld were about 850 fee ta pa r t . Th i s a g r e es w i th t h e e s t im a te d s e pa r a t i on d i s t a nc e o f 900 fee t on

t h e w a t e r.

Since t h e wind d a t a were measured se ve ra l minutes befo re la nd in g,

some dev ia ti on s were expect ed. A w ind p r o f i l e w i th in t h e e xpe c te d de v i-

a t i o n of t 2 kn ot s w a s c ons t r uc t e d t o de te rm ine i f c on t ac t betwe en t h e

forwar d he at s h i e l d and command module para chu te system was p o s s i b l e .

Based on the wind p r o f i l e t r a j e c t o r y s i m u l a t i o n s , t h e f o rw ar d h e a t

s h i e ld c ou ld have c on t a ct e d t he s pa c e c r a f t pa r a c hu t e s ys te m a t an a l t i t u d e

nea r 6000 f e e t . The i na c c u r a c i e s i n t h e m easu red da ta and t h e s im u la t i o ns

a r e s u c h t h a t i t c an no t be c o n cl u si v el y s t a t e d t h a t t h e c o n t a c t d i d o r

d i d not occur . I t can o nl y b e s t a t e d t h a t , i n a l l p r o b a b i l i t y , t h e m i s s

d i s t a n c e w a s s m a l l .

Pho tog r a ph i c a na lys i s . - A c los e e xa mina ti on o f t h e t e l e v i s i on r e c o r d

of s pa c e c r a f t de s c e n t on t he main pa ra chu te s e s t a b l i s he s t h a t t h e fo rw a rd

h e a t s h i e l d w a s below t h e space c ra f t at t h e t im e o f t h e f a i l u r e . S p e ci f -

i c a l l y , t h e f orw ard h e at s h i e l d i s seen below th e spac ec ra f t i n frame 588( f i g . 9 ) a t 295:09:11:3, approximately 2 seconds before the anomaly occur-

red . By c o r r e l a t i o n w i th frame 775, which shows th e par achu te and forw ard

he a t s h i e ld i n t h e s ame fram e at 295:09:17.5, and by di r e c t measurement

o f t h e s e pa r a t i o n d i s t a nc e be tw ee n t h e two ob je ct s and measurement of t h e

known pa r a c hu t e d im e ns ions, t h e ve r t i c a l s e pa r a t i on d i s t a nc e s betwe en t h e

forward he a t sh ie ld and t h e space c ra f t were 580 fe e t fo r f rame 588 and

1020 f e e t for f rame 775.

The p o s i t i o n o f t h e f orw ar d h e a t s h i e l d r e l a t i v e t o t h e g u id an ce -

a nd- na v iga t i on - e s t im a te d t r a j e c to r y i s shown i n f i g u re 10. By extrap o-

l a t i n g t h e f orw ar d h e a t s h i e l d t r a j e c t o r y , t h e f or wa rd h e a t s h i e l d would

h av e i n t e r c e p t e d t h e s p a c e c r a f t a t 295:09:03. This is 10.5 seconds be-

f o r e t h e s p a c e c r a f t da t a in d i ca te t h e anomaly occur red .

C-17



Television frame 588

295:09:11.3 elapsed time

A H ( 1 0 2 0 ft.) = 580 f t

A H = 580 f t

Dir ect measurement4.04 inches

01Tele visi on frame 7 7 5

295:09:17.5 elapsed t ime

A H = 5 7 4 (60/33) f t = 1042 f t

or 5 7 4 (140/80) f t = 1004 f t

A H = 1020 f t

80 u n i t s - z l 4 0 t

k r

I .74 uni ts

(Dire ct measurement - 7 . 1 1 i n . )

1020 - 5 8 0 f t / sec

17.5 - 11 .3

A V = 7 1 t/sec

F i g u r e 9.- Television frame and t ra jec tory analys is .

C-18



0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

U 0 9 N 03 d 0 9

9 9 In m d U d m

i j ' apnwiv

c-19



Assessm ent o f p ro ba b i l i t y o f fo rva rd hea t s h i e l d con t ac t i ng s p a s -

c r a f t . - An assessment of th e pr ob ab i l i ty of t h e forward hea t sh ie ld con-

t a c t i n g t h e s p a c e cr a f t w a s made t o de te rm ine t h e haza rd a s s oc i a t ed w i t h

con t ac t .

winds as a f u n c t i o n o f a l t i t u d e , wind v e l o c i t y , and d i r e c t i o n wer e us ed

as a b a s is f o r t h e s t ud y .

o f t h e spacec ra f t and forw ard hea t sh i e l d i n a p l a n a r ( 2 dimens iona l )

ana lys i s which y ie l de d the f requency of occu r rence o f sp ec i f i c va l ues Of

range se par at io n between th e two bodies a t i n t e r c e p t a l t i t u d e . Range

sepa ra t i on va l ues o f l e s s t han 100 f e e t between t h e two ve hi cl es were

cons i de red con t ac t . The cum ul a ti ve p r ob ab i l i t y o f con t ac t i s 0.093 per-

cen t . T h i s ana l y s i s cons i de red no t r a j ec t o ry d i spe r s i ons . Subsequent

r ef in em en t o f t h e p l a n a r a n a l y s i s t o i n c l u d e e f f e c t s of l a t e r a l d i sp e r-

s i o n (d ue t o t h e m od er ate l i f t o f t h e f or wa rd h e a t s h i e l d s y s te m a nd t h e

space craf t on the drogue parach ute) p rov ided a method which i s much l e s s

s e n s i t i v e t o v a r ia t io n i n i n i t i a l c o nd it io ns , p r i nc i p a ll y i n f l i g h t p at h

a n g l e. The r e f i n e d a n a l y s i s a l s o y i e l d s a c o n t a ct p r o b a b i l i t y o f a bo u t

0 . 1 p e r c e nt .

Actual wind data i n t h e form of frequency of occ urren ce of

Wind dath were a p p li e d t o n om inal t r a j e c t o r i e s

The wind d a ta a r e bas ed on measurements du rin g th e month of August

o v er a 1 3 - y e a r p e r i o d f o r an area nea r t he A po l l o 15 re co ve ry zone. Wind

frequenc ies were conce nt ra t ed in the eas t -no r the as t and wes t-southwes t d i -

re ct io ns . These winds , and winds +22-1/2 degre es from ea st -n or th ea st and

west -southwest, were used t o provid e a conse rva t i ve p l an a r wind p r o f i l e

which permi t t ed the ana lys i s .

The winds were used t o nodu late po in t mass, z e r o r l i f t n o m i n a l t r a c

j e c t o r i e s of t h e f or wa rd h e a t s h i e l d and s p a c e c r a f t . C h a r a c t e r i s t i c s of

t h e t r a j e c t o r i e s a r e shown i n t a b l e I .

Forward hea t sh iel d/p ar ac hu te su spens ion system impact t e s t s . - Dropt e s t s were conducted t o de t e rm i ne t he na t u re and ex ten t o f th e damage t o

t h e m a i n pa rachut e su spensi on l i n e s and f ab r i c r i s e r s when impacted by a

forward hea t sh ie ld a t s i mu l at e d f l i g h t c o n d i t i o n s . I n t e s t s o f t h e p a r -

ach ute components, th e r i s e r s and as so c ia t ed l i n e s were mounted a t t h e

f l i g h t a n g l e (38 d eg re es f rom v e r t i c a l ) , w i t h t h e l i n e s c o r r e c t l y f a nn ed

and pre- tens ioned ( f i g . 11). I n t h e s us pe ns io n l i n e t e s t , t h e f or wa rd

hea t shield impacted 5 f e e t above t he connec to r l i n k s , s t r i k i n g a l l 22

of t he l i n e s u sed , b reak ing fou r , and damaging 10 o t h e r s ( f i g . 11). The

room-temperature vulcanizing material on t he fo rw ard hea t sh i e l d edge was

c u t a n d gouged where i t s t r u c k t h e s u s p e ns i on l i n e s .

Two r i s e r t e s t s were made. I n t h e f i r s t , t h e f or wa rd h e a t s h i e l dimpacted 1-3/4 inches above th e f ab r i c conf luence po in t , and i n the sec-

ond, the forward hea t sh ie ld impac ted near th e c en te r o f t he 42- inch

r i s e r l e g s .

damaging the r i se rs .

on t he l ead i ng edge o f t he forw ard hea t sh i e l d was gouged ( f i g . 12).

In bot h c a se s , t h e fo rward hea t sh i e l d bounced o f f w i t hou t

However , t h e room-temperature vu lca niz ing mate r i a l

c-20



TABLE I . - COMMAND MODULE/FORWARD HEAT SHIELD TRAJECTORY PARAMETERS

I n i t i a l Cond it ions

Forward heat sh i e ld je t t i s onA l t i t u d e , ft . . . . . . . . . . 23 300

Fligh t path angle, deg . . . . . . -73 1

124Dynamic pressure, l b / f t . . . . .Spacecraft weight, lb . . . . . . . 12 810

Forward Heat Shield

Weight, l b . . . . . . . . . . . . 310

2Drag area, CDS

.ft . . . . . . . . 27.75

L i f t co e f f i c i en t , CL . . . . . . . 0

Spacecraft

Drag area, CDS (Nominal hi st or y f o r tw odr ogu e/

three-main-parachute operation 1

L i f t co e f f i c i en t , CL . . . . . . . 0

Alti tude of i n i t i a t i o n of main

parachute deployment, ft . , , 10 700

Forward Heat Shield In terce p t

Al t i tude , ft , , , , . , , 6 415

T i m e from forward hea t shie ld

j e t t i s o n . sec . . . . . . . . . . 135.2

-755No-wind range se pa ra ti on , f t . , . .

Spac ecr aft downrange of forward he at sh ie ld .

c- 21



4 orward heat shield leading edge

Broken and damaged lines

7 0 f t /sec

Two risers Impact point

Figure 11 - Results of forward heat shield/suspensio n system impact test.

c-22



F igu re 12.- orward heat sh iel d damage.

I lcan z ing

C-23



These t e s t s showed t ha t t h e forward hea t sh ie ld c on tac t in g <ne para-

chute could damage some o f t h e s u s pe n si o n l i n e s , but would probably not

cause a l o s s of r i s e r l e g s .

Forward heat shield/command module impact t e s t s . - Using the suspen-

s io n l i n e / r i s e r t e s t s e t u p , two ad di t io na l d rop t e s t s w i t h t he fo rw ard

hea t s h i e l d im pact ing t h e spacec ra f t were pe rform ed . I n t h e f i r s t t e s t ,

t h e forward hea t sh i e l d i m pac ted t h e spacec r a f t uppe r deck i n t h e minusY and minus Z bays , c aus ing ve ry l i g h t su r f ace damage t o t h e s pac ec ra f t ,

bu t s eve re damage t o t h e forw ard hea t sh i e l d . I n t h e s econd t e s t , t h e

forward heat s h i e l d i m pa ct ed t h e s p a c e c r a f t n e a r t h e h a t c h , b r e a k in g t h e

outer hatch window and gouging the a b l a t o r .

w a s severly damaged.

A ga in , t he fo rw ard hea t sh i e l d

Based on the impact t e s t s and an a ly s is , t h e worst-case damage which

could be expected would occu r i f th e forward hea t sh ie ld I .mpacted the

crew compartment he at s h i e l d window.

t h e heat s h i e l d window and in ne r window would be brok en.

There i s a p o s s i b i l t t y t h a t b o th

Forward heat shield/parachute canopy t e s t . - A t e s t i n w hich a f o r -

To simulate t h e i n -

ward hea t sh ie ld was dropped onto a pa rachu t e was performed t o assess t h e

damage which might r e s u l t t o th e para chu te canopy.

f l a t ed main parach ute , a 95-fOOt diameter poly ethy lene bal lo on w a s i n -

f l a t e d t o 0 .2 -in ch o f water ( th e dynamic p ress ure dur ing steady-state de-

sc en t ) w i t h t he pa rachu t e p l aced ove r t h e ba l l oon and t he su spensi on l i ne s

wei ghte d. By us in g a gu ide cab l e , t h e fo rw ard hea t sh i e l d w a s g u id e d t o

impact t h e parac hut e canopy. The i mpac t p roduced cu t t i n g , t e a r i n g , and

burn-type damage. One p a r a c h u t e r a d i a l seam w a s broken , ano ther w a s c u t ,

and s ix s a i l s were damaged. I f t h i s ty pe of damage had been experi enc ed

i n f l i g h t , t he pa rachu t e p robab ly would have r em ained i n f l a t ed p rov i d i ng

a near-nominal d rag e f f e c t .

Conclusions from forward he a t sh ie ld inv es t iga t io ns . - The forward

h e a t s h i e l d w a s not t h e cause of t h e f a i l u re o f t h e main pa rachu t e based

on two separate se t s of d a ta . F i r s t , t h e t e l e v i s i o n t a p e shows t h e f o r -

ward heat s h ie ld emerging from t h e clou ds approximately 3 seconds p r i o r

t o t he anomaly. Second, t h e r e su l t s o f t h e su spens i on l i n e and r i s e r i m -

pac t t e s t s w i t h t he fo rward hea t sh i e l d show t h a t su bs t a n t i a l damage t o

th e room-temperature vu lca niz ing mater ia l on t he l ea d i ng edge o f t he fo r -

ward hea t s h i e l d would have occurre d had the re been co nta c t . The recovered

forward hea t s h i e l d d id no t have t h i s type of damage. There w a s no evi-

dence of hea t sh i e l d con t ac t w i t h t h e pa rachu t e .

Both t h e t r a j e c t o r y a n a l y s i s and t h e t e l e v i s i o n a nd o b s e r v e r d a t a

show t h a t t he fo rward hea t sh i e l d d i d come c l o s e t o t h e space c ra f t . The

a n a l ys i s p r e d i c ts t h a t , f o r f u t u re f l i g h t s , probab i l i t y -o f -con t ac t i s l e sst han 1 i n 1000. I n a d d i ti o n , t h e t e s t s of t h e forward he a t sh ie ld impact -

in g the suspension and r i s e r l i n e s , t h e s p a c e c r a f t , a nd t h e c an op y, i n d i -

c a t e t h a t , sho uld co nt ac t occu'i- , th e re s u lt in g damage i ;ould not be c at as -

t r o p h i c . T he re fo re , Sased on t h e low p ro bab i l i t y o f con t ac t , and t h e

C- 4



and none were observ ed. This unnotched st ud w a s the n remounted i n a l i n k

assembly, torq ued t o 120 in- lb , which i s t wi c e s p e c i f i c a t i o n l e v e l , and

p l a c e d i n s e a water f o r 24 hou r s .

disassembled, and examined f o r cra cks. No cracks were found.

The l i nk s and s tud s were then a i r d r i e d ,

Eight a d d i t i o n a l s t u d s were t o r qu e d t o 200 i n - lb i n o r d e r t o simu-

Two s t ud s f a i l ed du r i ng exposure t o s ea water , t hus conf i rming

l a t e t he e f f e c t of t o l e r ance bu il dup of s t re sses a t s p e c i f i c a t i o n t o r q u e

l e v e l s .

t he po ss i b i l i t y o f gene ra t i ng sa l t-w a t er - i nduced s t r e s s co r ro s i on c rack -

in g if t h e p a r t s are within drawing l i m i t s .

Tens i l e t e s t s : Two l o t T st ud s, which had not been exposed t o S a l t

water , were placed under load as s t u ds t o a s t r e s s l e v e l o f 132 000 p s i ,

as computed fo r th e minor d i ameter of t he s tu d th r ead s . Thi s s t ress w a s

maintained fo r 200 hours i n an a i r environment. The s t r e s s w a s mainta ined

whi l e sea water w a s p l a ce d i n c o n ta c t w i th t h e s t r e s s e d t h r e a d s . Afte r

48 hours , t he sea water was a l low ed t o dry and the specimen w a s maintained

under load for an addi t iona l 24 hours .

men was examined und er 25-power ma gn if ic at io n. Both specimens were t henp u l l e d t o f a i l u r e i n t e n s i o n , a f t e r e x h i b i t i n g y i e l d i n g , at 254 000 p s i

( no rm al n otc h s t r e n g t h en i n g f o r t h i s m a t e r i a l ) . No evidence of pre-ex-

i s t i n g f l a w s or co r ro s i on was found on t he f r ac t u re su r f ace .

No cracks were found when the speci-

A t o t a l o f t en s t uds ( tw o each f rom: a pack l i f e p a ra c hu te , l o t U

th a t had not been f lown, and recovered parac hute s used on Apollo 1 0 , 1 2 ,

and 13) were l o ad e d i n t e n s i o n t o 132 000 p s i as c a l c u l a t e d f o r the minor

d i am e te r o f t h e t h read s . No f a i l u r e s o c c u rr e d i n t h e a cc um ul at ed 150

hours of a i r e xp os ur e t e s t t i m e on each specimen.

Two o th e r t e s t s were per form ed t o p r ov i d e b a s e d i n e d a t a on s t u d

f a i l u r e s .placed under a n e t s e c t i o n s t r e s s loa d of 132 000 p s i . The s t u d f a i l e d

in 30 minutes and thus v a l i da t ed t h e hydrogen embr it t l ement s c ree n ing

t e s t . The second t e s t u sed l o t R links t h a t h ad o r i g i n a l l y b ee n r e j e c t e d

due to hydrogen emb r i t t l ement . These l i nk s were t e s t e d t o 132 000 p s i

f o r 200 h o u r s w i t hou t f a i l u re , i nd i ca t i ng t ha t t h e hydrogen em b r i t t l e -

ment cha rac e r is t ics had decay ea .

An Apollo 10 s t u d was purpose ly charged wi th wdro gen and

The resu l t s o f meta l lu rg ica l examina t ions and these t e s t s suppor t

the fo l lowing conc lus ions :

1. Phys ica l ev idence fo r hydrogen- induced de layed fa i l u r e s of l o t

U and lot T s tuds does no t now ex i s t b u t , due t o the long e l aps ed t i m es ince p la t in g , hydrogen- induced f a i l u r e cannot be ru le d ou t .

2. Sea water does not induce cracks a t t h e t imes and nominal s t r e s sl eve l s expec ted , a l though gene ra l ru s t i n g of ex pose d s t e e l o cc u rs r a p i d l y .

S t re ss cor ros ion c racks can be induced by exposure t o s a l t water ats t r e s s l eve l s h i ghe r t han t hose expec t ed fo r a nominal 60 i n - l b t o rque .

C-26



3. For the f a i l e d s t u d s , t h e f l aws probably occurre d a f t e r t h e

p l a t i n g o p e r at i on .

P u l l t e s t s : A s e r i e s of connec t or l i n k pu l l t e s t s were conducted.

An Apollo l in k which had been preloa ded (n ut s tor qu ed) f o r more th an 2

The re cov ere d Apollo 1 5 c o nn e ct or l i n k w i t h t h e s e p a r a t e d s t u d w a s

f i t t e d w it h a r i s e r and suspens i on l i ne s and pu l l t e s t e d t o e va lu at e i t s

c a p a b i l i t y i n t h e t h r ee - n u t c o n f i g u r a t io n .

cou l d ca r ry l oad . T h i s l i nk w a s succes s f u l l y sub j ec t ed t o t wo com pl et e

f l i g h t l o a d c y c le s , t h e n t h e l o a d w a s i n c re a s e d t o 5000 pounds (which co r-

The l i n k h ad f a i l e d i n t hes t u d t h r e a d a nd t h e s t u d ha d a shoulder remain ing i n t he end p l a t e w h i ch

responds t o canopy ul t imate s t r e n g t h ) and s u c c e s s f u l ly h e l d f o r 2 minutes .

T hese t e s t s dem onst ra t ed t h a t t h e s t u d f a i l u re cou l d have occu r red p r i o r

s t u d s . T h is l i n k f a i l e d at 1300 pounds, a valu e below t h e opening loads

t o parachute deployment.

s i m u l a t i ng a t e n s i l e f a i l u r e of one st ud a t t h e shou l de r , o r tw o shea red

b u t h i g h e r t ha n t h e s t e a d y - s t a te l o a d s .

A f i n a l t e s t was made with one end p l a t e removed,

R e l i a b i l i t y and q u d i t y a s su r an c e r e co r ds review.- A review was made

of t h e m anufact u ri ng and i n spec t i on h i s t o r y r eco rds o f t he pa rachu t e l i nkassembly manufactured by Northrop Ventura.

North American Rockwell, Downey, California; Metal S u r f a c e s , I n c . , B e l l

Gardens , Ca li fo rn ia ; and Northrop Ventura, Thousand O a k s , C a l i f o r n i a .

Records were researched a t

The record s show th a t t he p a r t s fo r Apol lo 1 5 ( l o t Q p l a t e s , a n d

l o t U s t u d s ) an d Apollo 16 ( l o t W p l a t e s and s t ud s) were prop er ly pro-

ce s sed i n acco rdance w i t h t h e l a t e s t r ev i s i on o f t h e N ort hrop p l a t i ng

s p e c i f i c a t i o n .

One s i gn i f ic an t i t e m di sc lose d by the rev iew was t h a t l o t R s t u d s

which should have been sc rapped were accep ted and in s t a l l e d i n f l i g h t par -

achu t e s .

i n s t a l l e d i n a p a r a c hu t e t o be u se d f o r f u t u r e f l i g h t .

Lot R st ud s were 'f lown i n one parachu te on Apollo 14, and were

Parachute tow t e s t s . - A s e r i e s of ground tow t e s t s w a s conducted t o

e v a l u a t e t h e c h a r a c t e r i s t i c s of t h e i n f l a t e d p a ra c hu te arid r i s e r l oad re-sponse re su l t in g f rom sever ing one, two, and th re e r i s e r l e g s of a fully

i n f l a t e d main p a ra c hu te . I n f l a t i o n w a s obta ined by towing th e parachute

C-27



i n t o th e wind. When t h e canopy w a s f u l l y i n f l a t e d and s t a b l e , s e l e c t e d

r i s e r s were pyro tec hnica l ly severed . Ind i v idu a l riser l e g l oa d s, t o t a l

r i s e r lo ad , and photographic documenta t ion were ob ta in ed .

When one of t h e s i x r i s e r l e g s w a s seve red , t h e canopy remained fully

i n f l a t e d and , i n app roxi m at e ly 2 seconds , exh i b i t ed f u l l r i s e r load. When

two adjacent r i s e r l e g s w e r e severed , t he canopy co l l apsed but d i d con t i nuet o p ro v id e a drag fo rc e o f approx im a te l y one - th i rd t h e fu l l y i n f l a t ed V s l U e .

Three r i s e r s were s ev er ed i n t h e t h i r d t e s t ; two vere a d j ac e n t and t h e t h i r d

w a s separated from them by a good r i s e r l e g . When th e r i s e r s were sev ere d ,

t he canopy c o l l apsed , w i t h t h e po r t i on oppos i t e t h e s evered r i s e r s ho l d i ng

a i r f o r s e v e r a l se c on ds . The lo a d h i s t o r i e s f o r e ac h of t h e t h r e e t e s t s

are shown i n f ig ur e 13. The i n i t i a l loa d drop f o r th e one-, two-, and

t h r e e - r i s e r t e s t w a s 600, 1700, and 2300 l b , r e s p ec t iv e l y.

These t e s t s i nd i c a t ed t ha t t h e A po ll o main pa rachu t e w i l l remain

fu l l y in f l a t ed and prov ide normal d rag wi th one of i t s s i x r i s e r l e g s sev-

e red . When two or more adjacent r i s e r l e g s are severed, the canopy w i l l

c o l l a p s e , and l o s e a t l e a s t t w o- th i rd s o f i t s l o a d - c a r r y i n g c a p a b i l i t y .

Conclus ions f rom connector l i n k inv es t ig a t io ns .- The f a i l ed l i nk on

t h e r ec ov e re d p a ra c hu t e i m p l ie s t h e p o s s i b i l i t y o f a s imi lar occurrence

on t he f a i l ed pa rachu t e . However, t h e pa rachut e tow t e s t s i nd i c a t e t h a t

a s ing le l i nk f a i lu r e would no t have caused th e load change (approximate ly

1300 pounds) de te rmined from th e spa cecr af t da ta . Although th e l i n k fa i l -

u re i s not be l i eve d t o have caused the parachu te anomaly , a complete rec-

ords review and a m a t e r i a l s t e s t program were performed t o deter mine t h e

cause of th e f laws. The record s show th a t th e Apol lo 15 l o t l i n k s were

processed i n accordance wi th a l l requi rements . The l i n k t e s t s show ed

t h a t t h e b ro ke n l i n k can c a r r y t h e f l i g h t l o ad s ( i n t h e c a s e o f A po ll o 1 5t y p e b r e a k ) .

b r i t l em en t o r s a lt -wa t er - induced s t e s s c o r r o s i o n a t h i gher- than-expected

s t r e s s l e v e ls as t h e p o s s i b l e c au se o f t h e f a i l u r e . I n f a c t , t h e c au se

of the f l aw i s not known.

The ava i l a b le ev idence cannot ru l e ou t e i t h er hydrogen e m-

Command Module Reaction Control System

The cormand module reaction control system w a s cons idered as a p o s s i -

b le cause of th e anomaly f o r th e f o l lowing reason s :

a.The p rope l l an t dep l e t i on f i r i n g t e rm i na t ed

3.5seconds bef ore th e

spacec rafb ra t e s gave ev idence of a major d i s tu rba nce . The excess fu e l

expul sion which fo llowed th e dep le t i on f i r i n g w a s s t i l l i n p r og r es s a t t h e

t ime of f a i l u r e .

b. The damaged parachute held a po s i t io n g ene ra l ly above th e minus

Y r o l l e n gi ne s w h il e t h e f u e l e x p u l s io n was i n p r o g r e s s.

C-28



c. Burning f u e l can cause damage t o th e r i s e r s , s u s p e n s i o n l i n e s ,

or parachute canopy.

d. Evidence of melt ing w a s found on the Dacron pr ot ec t i ve covering

of t h e f a b r i c r i s e r a nd t h e c on ne ct or l i nks on the recovered parachute

ass emb l y .

System Ope rati on. - Both command module r e a c t io n c o n t r o l sys tem s were

ac t iva ted normal ly a t 294:07:14. Both systems were used du rin g ent ry as

opposed t o prev ious miss ions where one system w a s t ur n ed o f f p r i o r t o e n t r y .

System performance dur ing th e c ont ro l l ed po r t io n of en t ry w a s n o m i n d as

ver i f i e d by pres sure and t empera ture da ta and f rom spac ecra f t rates pro-

duced by commanded eng in e f i r i n g s .

The command module re ac t i on co nt ro l system co nt ro l f i r i n g s were t e r -

minated normally a t 295 :06:44when the systems were e l e c t r i c a l l y d i s a b l e d .

A t t h i s p o i n t i n t he m i s s i on , t h e eng i nes had been f i r ed app rox i ma t el y

680 t im es and th e t o t a l f i r i n g t i m e was about 160 seconds . The pro pe l l an t

usage had been 20 pounds of f u e l and 36 pounds of o x id ize r , d iv id ed equ a l lybetween th e two systems . Pr op el la nt consumption w a s e s t a b l i s h e d by p r e s -

su re , tempe ratu re, and volume cal cu la t i on s and confirmed by t h e summation

of t he eng i ne f i r i n g t i m es . U sable p rop e l l an t r em a in i ng a t 295:06 44

p r i or t o t h e s t a r t of t h e d e p le t io n f i r i n g , w a s 30 pounds of f u e l and 53

pounds of ox idi zer i n each system f o r a t o t a l o f 60 pounds of f u e l and

106 pounds of ox id i zer . Tota l p ro pe l l an t remain ing , inc lud ing th e t rap ped

p r o p e l l a n t s , was 69 pounds of f u e l and 120 pounds o f o x i d i z e r .

The command module re ac t i on c on tr o l system de pl et io n f i r i n g w a s man-

u a l l y i n i t i a t e d a t 295:08:22.

in terconn ected by opening squ ib valve s between th e hel ium manifolds , t h e

fu el manifolds, and th e ox id iz er manifold s. The engine valves on a l l b u t

t he two p l u s p i t c h eng ines w ere a l so opened u s i ng t h e d i r e c t c o i l s . Sys-

tem p r e s su r e s i n d i c a t e d t h a t t h e d e p l e t i o n f i r i n g w a s normal wi th ox id izer

deple t ion a t 295:09:10. Fuel dep l e t ion fo l lowed 4 . 7 seconds l a t e r . T hese

t imes were confi rmed by ca lcu la t i ons us in g th e prop e l l an t remain ing p r i o r

t o th e f i r i n g , and a mixture r a t i o and pr ope l l an t f low r a t e commensurate

w i t h s t e ad y - s ta t e f i r i n g from 10 eng ines . Between th e t ime of oxid iz er de-

p l e t i o n and fu e l dep l e t i on , abou t 7 pounds of r a w f’uel were being expelled

D ur ing t h i s f i r i n g , t h e two sys tem s were

The command module r ea ct io n c on tr ol system l i n e purge op er at io n wasmanual ly in i t i a t ed a t 295:09:22. This opera t ion opened four squ ib va lves

t ha t enab led t h e he li um gas t o bypass t h e p r ope l l an t t anks and pu rge t he

re s i dua l o r t r apped p rop e l l an t s from t h e sy st em m an ifo ld l i n e s . R egu l at ed

helium p re s su re and he l ium sou rce p re s su re da t a ve r i f i e d a normal purgeope ra t i on . A t 295:09:25 and 295:09:28, co lo re d clou ds ,were se en coming

from the spa cec raf t . Th i s i s normal and i s caused by th e e xpu lsion of

unburned oxid ize r through t h e engines by t he purge ope rat i .on. Unburned

f i e 1 i s a l s o o f t e n s e en a bo ut t h i s t i m e i n t h e f orm o f a whi te c loud .

C-30



Po st f l ig h t t e s t i n g of th e command module re ac t io n c on t r o l syst em

showed i t t o be i n normal working order . Tes t in g inc lud ed leak checks

of t h e p r o p e l l a n t t a n k b l a d d e r s , engine valve leak t e s t s , e n g i n e v a l v e

s i g n a t ur e t r a c e s t o v e r i f y p r op e r opening c h a r a c t e r i s t i c s , and e l e c t r o n i c

t e s t s t o v e r if y t h e e l e c t r i c a l w i r i ng and t e rm i na l boa rd connec t ions .

Command module react ion control system fuel expulsion t e s t s . - Twot e s t s were p erf or me d t o i n v e s t i g a t e t h e p o t e n t i a l e f f e c t s of a r a w f u e l

expul s ion on th e parachutes :

The f i r s t t e s t w a s a f e a s i b i l i t y demons tr at ion t o de te rm ine i f f u e l

sprayed on th e para chute r isers and suspension l i n e s would bu rn , assuming

t h a t t h e r e c o uld b e a n i g n i t i o n s o ur c e. A simple nozzle w a s u se d t o s p r a y

r a w f u e l i n t o a 30 f’t/sec a i r st ream and onto a sam ple of t h e r i s e r and

suspens ion l ines , par t o f which was surrounded by a Dacron bo ot ie . Hot-

w i r e i g n i t i o n s ou rc es were imbedded i n t h e boo t i e and r i s e r t o simulate

an i n f l i g h t i g n i t i o n sou rce . T hese t es t s demonst ra t ed t h a t , above ce r t a i n

t h r e s h o ld f u e l c o n c e nt r at i on l e v e l s , t h e f ie1 on th e boot i es would burn i n

a wick-like manner.

due t o mel t ing of t h e ny lon material .T hi s r e s u l t e d i n r i s e r and s us pe ns io n l i n e f a i l u r e s

The second t e s t c o n s i s t e d of f i r i n g a command module reaction control

system engin e fol lowed by fu e l co l d f low ( s im u l a ted fu e l expu l s i on ) .

w a s performed t o i n v e s t i g a t e t h e e f f e c t s of cold f lowing r a w f’uel through

a hot engine.

minus-pi tch nozzle e xte nsi on were mounted ho ri zo nt al ly i n an ambient t e s tc e l l . There w a s no a t tempt t o simulate t he r e l a t i v e air ve l oc i t y sur round-

i n g a descending command module. The t e s t fi r i n g s co ns is te d o f a seriesof h o t f i r i n g s of 1 0 t o 45 seconds i n dur a t ion , each fo llowed by a 5 ~ s e c o n d

fu e l cold flow (about 0.6 pound of f’uel).

puls ion sequence produced burning outside of t he eng i ne .

vapo r , bu rn i ng fu e l d rop l e t s , and some unburned f u e l were observed during

t h es e t e s t s .

plane and unburned f’uel was sprayed up t o 10 fee t f rom the engine and then

i g n i t e d by b u rn in g d r o p l e t s .

I t

For t h e s e t e s t s , a rea c t io n co nt r o l syst em engine and a

I n e ve ry c a s e , t h e raw f u e l ex-

Burning f u e l

The f lame f r on t e x i s t ed up t o 8 f e e t from the engine e x i t

Conclusions from re ac t io n c ont ro l sys tem inves t iKat io ns . - A s a result

of these t e s t s , t h e h a z a rd o f a raw f u e l e x p u ls i o n w as demonstrated.

a d d i t i o n , s i n c e t h e f a i l e d p ar a ch u te w a s p o s i t i o n e d o ve r , th e r o l l e ng in es

f o r t h e t i m e p e ri od J u s t p r i o r t o t h e anomaly, t h e e f f e c t s no t ed i n t h e

second t e s t were, most l ik eJ y, th e cause of t h e Apollo 1 5 p a r a c h u t e f a i l u r e .

I n

CONCLUS IONS

The a n a l y s i s o f t h e d a t a and r e s u l t s o f t h e s p e c i a l t e s t s l ea d t o t h e

fol lowing conclusions:

C- 1



a . The most prob abl e caus e of t h e anomaly was - t he bu r n ing o f r a w

fu e l (monomethyl hydraz ine ) be ing exp e l led dur i ng t h e l a t t e r p o r t i o n o f

t h e d e p l et i o n f i r i n g and t h i s r e s u l t e d i n e xce ed in g t h e p a r ac h u t e- r is e r

and suspens ion- line t empera ture l i mi t s .

b. The forward hea t sh ie ld passed extremely c l os e t o t h e commandmodule durin g t h e descen t phas e; however, at t h e t i m e of t h e anomaly,

t h e h ea t s h i e l d was 700 f e e t below t h e command module.

e . Impact of th e forward hea t sh ie ld on t h e paxachute r i s e r s , SUS-

pe ns ion l i ne s , anopy, or s pa c e c r a f t w i l l not c a use c a t a s t r op h i c da m ge .

d . The f a i l u r e o f a s in g l e conne ctor l i n k w i l l not cause a m a i np a r a ch u t e t o f a i l .

e. The f law observed i n th e recove red pa rachu te connec tor l i n k prob-

a b l y o cc ur re d a f t e r t h e p l a t i n g o p e r a t i o n , an d c ou ld b e due e i t h e r t o s a l t -

water-induced stress c o r r o s i o n or hydrogen embrit t lement.

CORRECTIVE A CT I O N

C or r ec t i ve a c t i on s f o r t h e r e a c t i on c on t r o l s yst em include l a nd ing

w i th t h e pr o pe l l a n t s onboard f o r a normal l a n d i n g and b i a s i n g t h e p ro -

p e l l a n t load t o p ro v id e a s l i g h t e xce s s o f ox id i z e r . Thus, f o r t h e low-

a l t i t u d e a b o r t l a n d l an d i n g c a s e , bu rn ing t h e p r o pe l l a n t s w hi le on t h e

parachutes w i l l subj ec t t h e pa rachutes t o some accepta ble ox id iz e r damage

b u t w i l l e l i m i n a t e t h e d an ge ro us b i r n i n g f u e l c o n d i t i o n . I n a d d i t i o n ,

t h e t i m e de l a y which i n h i b i t s t h e r a p i d p r op e l l a n t dump i s being changed

from 4 2 t o 6 1 seconds.

l an t w i l l not have t o be bur ne d t h r ough t h e r e a c t i on c on t r o l s ys te m en -

g i n e s i n t h e event of a l a n d l a n d i n g .

This will pr ovide more a s s u ra nc e t h a t ' t h e p r ope l -

The de sign of t h e s us pens ion l i n e c onnec to r l i n ks has been modified

t o prec lude t h e development of high stress l e v e l s due t o to rq u e l e v e l s

and t o re du c e t h e u n c e r t a i n t y o f l o a d s due t o t o l e r a n c e b u il d up .

material has been changed t o Incon el 718 t o e l i m i n a t e t h e r eq ui re me nt f o r

p l a t i n g an d, t h e r e f o r e , t h e p o s s i b i l i t y o f h ydro gen e m b r it t le m en t .

a d d i t i o n , t h e l i n k s tud t h r e a ds a r e r o i l e d r a th e r t ha n mach ined t o im prove

m e t a l l u r g i ca l p r o p e r t i e s o f t h e m a t e r i a l , and t h e s t u d s a r e s u b j e c t e d t o

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