AD-769 930

AN EXPERIMENTAL STUDY OF ATTENUATIONOF SHOCK WAVES IN AIRCRAFT FUEL TANKS

John R. Breuninger, Jr.

Air Force Institute of TechnologyWright-Patterson Air Force Base., Ohio

June 1973

DISTRIBUTED BY:

National Technical Information ServiceU. S. DEPARTMENT OF COMMERCE5285 Port Royal Road, Springfield Va. 22151

Best Available Copy

IN I III' C.Lgy I YN~ k~.4. A I I A

* \± i L-~ Pt to mion AF 11, Ohio

An~ljI.~ .d of Attt~nuativon of .13hock W.,%vav in~ Atiro rali fue). T.i~nkil

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NAM~NAL TECHNICALA. ý,vod) for pul-A.± release; dia.t~ribution i nnlimit. hd. INFORMATION SERVICE

UI S D*Pwt4M#nt 1.f C~nM4(C*

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Thn fR~,or pmrtiaiilv f'ull, aircrai'11 fuol tank is ponvtrated hy a h i g"e½C.l;7 lr~(~'~ i.'ea per~:m.~knoiyn wa hydrnwilic ram cf*.eci,, creatncd b,; t: io'the pro!icctAiet-hour the .flidi of'ten cauties n,;tusvo damage tu) the tank.

'Ti.4 Ltuiy WA,., 42ol-ldOktfud to con[t.inuoh (Žx~xOVJUmr11taI inv(estjtirzton c' the att~urxua.;ionof t;,iv hvdaulic mm of'fect t~hrourh addi~tion of a 1-a t~o a 1Toi.-._foam 1m,. XtUre.

* Tiho -vests were condiucted u''"je'- two fy.Ytmo of' pr/rjee :Iia ( iri. stc, zhode

* rld 0.50 cailhaov or~dvaJ. px'ojoc'lof.e) which we-e dfx'od int.0 a tea~t fulnh. -The tankW-i ffl£iicd fir9t, with watoir and then a water/Pneumr~cei mixttwc. Pour prossuretrwirlducerI3 were locacstnd in the back- wail, of the t.;tm. ~m~n 'two prossure traun.ducer!1-*'nru locat.'ed insidei th,, tan~k to wtr-ýure, the press8uve pu) je.. . -I

he inititti preasure pulue calwed by the p'oaiaotiitv movi~nr: through the wre~tr01Iore wwý measured during the f'tirqt seri.oa of' teats. Psin. ntrdcin in

011. pri-:esuve 1.'a noted duini'.ir thti necond usarieu in -whfiih the vmw,~r/PnF~matcoelZatuiix vi.w t's 0Used. Yt. was al'iso fCound that. x proj1ectli m.~novingr th rough the ti uidl(,renites a cavity in ito wolko. Whtln- tte CalVity co Ls~,a prosatre wave J..3 gen-emstod. The cavity created. bv the p~asnxe, of' the tbronjph the I'jtiiA was

* ...I'a~l a. nd t~hI pres).mure wF.(tVp pene'ated byr it;] nollaif)'c. w-As.iifiiOr' whienr eoinpnezed-to the initia). pretisuro wavo. How'-vter, l.ýho p-esomirk" .Ž 've c ref,-.t by .tbhe 'ollpe

ef hu -ity behind thp ogivat pvojoc t.1ice wall apU ~ti ~r ~aniom ueathC- .illitiJ~. pftl ~ . wi~ve. It appteara f.Ntt this s vet-nd pro~quxice *wata'p mI~vA, t) a mnajor,coi' rihdiNor t,- n1'Atsivo~ f'uel tank damkmxýQ. I)utrIng iVe ~Iwcwd seies of testts (wAter/

1'2l~e~Irxid.xtui'e) , thin pretssure wavo wntas i~nifiuncatly 1'cduQ'nd.

* ~ 1473 .StC,~ti..1w

I' 711111 1;. 7 1 ;LH;J C*~Ilythva'.1 c Rami E. ffec

Alrcvaft F~uel Tanks

"Ia"1fca o

AVPTTY.4'TIY)TOM OF SHfOCK WAVESITT ATPCRA4~r X'IJEL TAWKS

GA,4C7--3 John~ R. Btveiziinprr, rCaptain U."VI

Approved. for pu'blic re1.ea.qe- distribution unlimiited.

AN MYJ 'V-ffNTAJJ STUDY OF AVIT1ATION

OF SHC1. WAVES IN AMhCRAFT FUET TANKS..

Pre~cnted to.t-' Faculty of the School. of Engineerdngof the '.r Force Institute of Technology

Air Univer3ity

In. ;rtial Fulfillmpent of theReni r eroents .for the Degree of

Master of Science

by

cohn R. 1Preuninger Jr., BS3ttain USAP

Gr&(-;!ate Astronautical- EngineerinigJune.1973

Approved for 1, ýlic release- disitributi~on unlimited.

/. Preface

/This report represents a continuation of experimental studlvs

of/the thdraulic ram effect ,and its effect on airoraft fuel cell

-i . svrvivability. I hope that the information contained in this report

11 lead to further research and development in the area of fuel cell

.urvivability.

/ I wish to thank many individuals without whose support this/'research would not have been possible.

S/ Specifically, I want to thank Dri. Peter J. Torvik, my thesis

44" I advisor; Major James Wade of the Survivability Division of the Air

Force Flight Dynamics Laboratory; Mr. L. Gilbert and the Survi',a- "

bility Test Group of the Air Force Flight Dynamics Laboratory; and

i / Dr. Bernard Lavery of the Du Pont Corporation who supplied the Pneumacel

and furnished information concerning it.

I also wish t;o thank Mr. Charles Anderson, Mr. Raymond Settles,

and SSgt. Karl Aune for the many hours thty spent helping me find and

fabricate equipment and conduct the tests.

And most of all I wish to thank my wife, Mary Elizabeth, who

spent many hours reading rough drafts and running our home while I

was doing this work.

John R. Breuniuger Jr.

- ?

. " . ". . .

~"Pre ace

/Ihis'report rep~res~nts a continuatioki of,-experirie~ntal studica

of (the hydraulic ram~effect, andlits effect on',aircraft fuel cell

suravivability. I op that the information , contained in this report

w,11l lead to further research and development in the area of fut~el cell

survivability.

I wish to thank many individuals without-whose 3upport this

*research would not have been possible.

Specifically, I want to thank Dr. Peter J. To'rvik, my thesis

advisor; Major JamesWade of the Survivability Division of the Air

Force Flight Dynamics Laboratory; Mr. L. Gilbert and the Surviva-

bility Tt~st Group of the Air Force Flight Dynamics Laboratory; anxd

Dr. Bernard Lavery of the Du Pont Corporation who supplied the Pneurpacel

and furnished informa~tion concerning it.

I aJlso wish to thank Mr. Charles Andernon, Mr. Raymond Settlen,

and SSgt. Karl Aune for the many hours tht-y spent helping me find and

::Lft'icatc equipment and conduct the tests.

PTi~ most of all I wich to t~hank my erife, Matry Flizabeth, who

r~n hours rcading rough drafts and running our home while I

wao doing this work.

John R. Breuni-tger, Jr.

Contents

i Preface . .. .. .. .... . . .. . ... Hi

"List of Tables . . .......... . .. . . . . . . iv

Li"ct of Figures . . . . . . . . . . . . . . . . . v

Abstract . . . . . . . . . . . . . . vii

I Introduction !

Backgrouad 1Purpose and Scope 3

II. Experimental Apparatus.. ............. .

Target Materials ••••............ SApparatus, . . . . . S

Instrumentation 11

III. Experimental Procedres ..... . • • • . , • • 13

IV. Results and Discussion . 16

Results . . . . .. . . . .. . . . . .. . 16Discussion . . . . . . . 20

S~~Series 1 .......... 20

Series 2 . . . . . . . . . . 26General . . . . . . . . . . . . . .... . • 28

V. Conclusions and Recommendations . . . . . . . . . . 31

Conclusions . . . . . .* v 0 0 # . 31Recommendations ..... .... ........ 31

Bibliography • . . .. 32

Appendix A: Pneumacei 33

Apendi% B: Blow Out s,. .. .. u.•• 35

Appendix C: Oscilloscope Pietures • . . • • . . • 38

Vit .a . . . .. . . . . . . . . . .-. * . . . . . 62

(:,

.)iii

GA;V~C/7I3-3

Lis of TAWb es

Table Page

ITabul~ated Results ofSer~ies 1 . . . . . . . . . 18

II Tabulated Results of Series 2. 9 ... 21

III Computed and Actual Pressures during

Blow Out.Plug Test . . . . . ... 36

iv

GAAIC/7)-3

List of Figurei

t"Figure Page

1 General Apparatus Layout .............. 6

2 Transducer and Blow Out Plug Arrangement ....... 91-

3 Blow Out Plug (Side View). .1.......... .a 0

4 Scope Pictures, Series 1, Part 1, Shot 8 ....... 17

5 Impact Pressure Versus Velocity (Series 1,Spherical ProJectiles Only). ... 9...9..... 23

6 Ogival Projectile in Test Tank . . . . . . . . . . . . /4

7 Ogival Projectile in Test Tank. . . . ........ 24

i i:" 8 Ogival Projectile in Test Tank ........... 25

9 Ogival Projectile in Test Tank . ... . .. . . . 25

10 Impact Pressure Versus Velocity (Series 2,Sphcrical ProJectiles) 27

"11 Cavity Created by Of'ival Projectile . . . . . . . . , 29

12 Collase of Csvity Created by Ogival Projectile . . . 29

13 Pneumacel . . . . . . . . . 34

14 Cross-section Photomicrograph (magnified 4000 times)

Sof Pnumael . . . . . . . . . . . ........ 34

15 Scope Pictures, Series I, Part 1, Shot I . . .39

16 Scope Pictures, Series 1, Part I, Shot 3 . . . .• . 40

17 Scope Pictures, Series 1, Part 1, Shot 5.. , . . . . 41

18 Scope Pictures, Series 1, Part , Slhot 6 . . . . . . . 42

19 Scope Pictures, Series 1, Part I, Shot 7 • . • . . . 43

- - . 20 Scope Pictures, Series 1, Part 1, 3hot 8 . . . . . .. 44

21 Scope Pictures, Serie• 1, Part 1, Shot 10 . . . . . . 45

* v.-

-G•./v,/73-.3 -

Lint of Fipures

22 Scope Pictures, Seritos 1, Part 1, Shot ii . . . 46

23 Scope Pictures, Series 1, Part 1, Shot 12 .. . . 47

24• Scope Pictures, Series 1, Part 1, Shot 13 . .. .. .. 48

25 Scope Pictures, Series 1, Part 2, Shot 14 . ..... 49

26 Scope Pictures, Series 1, Part 2, Shot 15 . . . 49

27 Scope Pictures, Series 1, Part 2, Shot 16 . . . 51

28 Scope Pictures, Series 2, Part 2, Shot 1A ...... 52

29 Scope Pictures, Series 2, Part 1, Shot IA . . ... 53

30 Scope Pictures, Series 2, Part 1, Shot 3A . .. . 54

31 Scope Pictures, Series 2, Part 1, Shot 4A . . . . . 5

32 Scope Pictures, Series 2, Part 1, Shot 5A . . ... 56

33 Scope Pictures, Series 2, Part 2, Shot 6A . . ... 57

34 Scope Pictures, Series 2, Part 2, Shot 7A . . ... 58

35 Scope Pictures, Series 2, Part 2, Shot 8A . . ... 59

36 Scope Pictures, Series 2, Part 2, Shot 9A . . . 60

37 Scope Pictures, Series 2, Part 2, Shot 10A . . ... 61

V.1

.A/MC/73-3

Abstract

When a full, or partially full, aircraft fuel tank is penetrated

by a high velocity projectile, a phenomenon known as hydraulic ram

effect, created by the passage of the projectile through the fluid,

often causes massive damage to the tank. This study was conducted to

continue experimentil investigation of the attenuation of the hydraulic

ram effect throurh addition of a gas to a fuel-foam mi.-.ture.

The tests were conducted using two types of projectile (-4 in.

steel spheres and 0.50 caliber ugival projectiles) which wore fired

into a test tank. The tank was filled first with water and then a

water/Pnoumacel mixture. Pour pressure transducers were located in

the hack wall of the tank and two pressure transducers were located

inside the tank to mea'nurc the preswure pulses.

The isitial pressure rulsu caused by the projectLle movi.ng throu h

the water alone was measured during the first series of' toots. A

significant r(,duction in this pressure wan notcd durinp the second

norLie: ir which the water/Pneumacel mixture wans used. It was also f lund

that a projectile m.Aing through the fluid creates a eavity in its vk (e.

Whe•n thu cavity orA .apsne, a pressure wave Is generated. The cavity

created by the pý..em'e of the spheres through the fluid wan small anfd

the pressure wave generated by Its co)lapsc wan insignificant when com-

pared to the initial prnururo wave, However, tht. presaurc wave created

by the collapse of the cavity behind the ogivrAi 1projectile wita approxi-

mAtely the came marnitud' as the iriOt.)Al rx-uro ave... It appearn that

this second pVesnure wave mny be a ,ijotn contributor to pnqmive 1'l

tarn< daiApo. DurinF th, nfirund aeri.3 cl" tento (water/iPneunmcol mixture),

thin prenaure wave wan nricnificantly redjced.

vii

I ~~~~~ ~ ~ ~ ~-i t _WX ,-hli I -1:Iý1 I

AN FXPFiRTVM!M'VAL 3'"UDY OF~

VAPPPNTJATTON1 OF' StIOCK WIAVESTN AIMCRAP'T FUR)", TANKS

I. Tntroduotion

ackround

In recent years, a great deal of work has been accomplished in

the area of aircrafM'. 4fuel tank (or fuel cell) survrivability. Reticu-

lated polyurethane foamt has been developed And pulaced in fuel cells

to reduce the possibiliity of fire or explosion if the empty, or

partially ctnpty, fuel. cell ir, strucK, with an incendiary bullet.

Self-sealing bladders ha~ve also beeni developed to seal a amall fuel

cell rupture.

Hovinver, during duvelopr4int. a'nd testing~ of theac fuel cell.

survivability devici.n itt wns dPi~coverevi th~ttL a full, ornerl

Lfull, fuel cell was a~uaceptible-t niaove damavge wht; 1 otruck by a

high velocity projectile. . caliber (,i.o., 0.1 o efI or)

prvjectil.es cauaicd such wxtcoiirvQ damage) th~at the self- nealing fuel.

cell bladders we~re unable to ova~l the rupturo.

Such a massivc failure can lead to niot~deaiu of' airerift~

kill. F'utl utarvzitica it' a m.in tank in r~untured, fir'e or eocordary

exploeion within the aircraft, or d-amage to* critical tn±rcra~ft eyoteme~

are a.ll. poissible if a oeverei futil cell ruptw-m is present.

Hydraulin Prun Frfcct. Thu phonomono~n whieh cwx~t'uo t.hiti reru~aiva

rupture of the f'uel cell its the hytivitulio rant efrtut. The~ hvd rdaUi.Lc

ram effect is actually a oc'iosa of events which are relatc- and, in

actual oocurrance, overla~p oach okiicv. S;tabrA nk fl [rlj .sow (IR! 6),

the NJorthrop Corporati~on (Ref 5), ind~ *clristow (flef 2) aprue that thure

I

-• -"• W•'*=*" ' -' .,• " '-' " i.. . . '. *'. ' .. .. , - ' ? .. . ".'- , . . ~ ¶ .. .. • . 1 V U• . ... . . .. .. , .t •

""re 5 blnlic eventr, : (i, icic olhock wav, 1ai r i Lokid by thu ,Im-Ajoatllc

initially penetratJngi tho t'xonL wall of Wto fuel a•ill, (?) thu contil-

UoUt.I generation Of n ')i'CroturI' fitalId 4 vh* I)ro~jeottilo paLlutl*U throlugh

the fluid, (3) thu prenmurc riate cauaed by the t-ubling of the projlec-

tile, (4) the builo-up of p'-essOure on thol bllýk wall aS t%.o projeLoilo

approachos the wall, (5) the creation and collapse of a largo oavity

behind the proje. tile.

Some analytic studies of the hydraulic ram effect have been per-

formed. Seaberg and Bristow (Ref 6) analyzed the effect using simple

drag theory and energy transfer theory. While thin approach was

adequate to model the passage of the projeetile through the fluid,

it was too simple to cnmpletely describe the other interrelated effects

k of the hydraulic ram. Al .erson (Ref 1) used a bi 'st wave theory to

npproximate the peak oressure within the fluid and a rigid-plastio plate

theory to analyze th(. exit wall region of the tnik, Etowever, if MaOh

event is analyzed individually, a ,o)ssible 8ynargisti ! t'teot due to

the complex interplay of -the various hydraulic ram effects is lost.

Other studies that have been performed have used an experimental

trial-and-error approach. In most cases, understanding the hydraulic

ram effect from a macroscopic view and determinix- what could be

done to reduce the efiect were the goals of the experiments. Stepka

(Ref 7) conducted some experimonts with high velocity projectile

impacts of a water filled tank. This study was perforned during 1965

and was conducted to understand and measure the basic hydraulic ram

effect. Northrop (Ref 5) also conducted hydraulic ram studies$ but

these were accomplished to provide specific inforiation for construction

* of a fuel cell which would withstand the rain under certa.a.n conditions..

2

O t,0t n I )',, Wtoil p1t'u V~ fol 'thAi Pok) Inatity t of. hydptii10

I.Tlai in19? OlaU (iar ~))O thUnpit to, obtbiii oomo\t~tt hAain OckUIiil~iy

on t~he hytir&%ilia ram arortýn. Ile oonTtltUiAtgd axpurimaintttl teitm in whish a

hylraulia rAm woot ýPeietod by firing --I incQh aphoim W~~db~i~t at hMah

(2700 Vt~ per cootakti) v.Xaloty into~ 4 ;: tut't waitor-illod ttik. The

proat&kir f'ield pnrtr od by the p~anaamii of Wie ahron throup.1 tho M~ter veto

1106ivd Thtoo havi" obt~iitad a knon lAtA b~aaOW~k tteptad to ttan-l

the wate~r. The roatulte weo'o 01MWting and Curttw :, touting ',ae ruooomonde4.

ýj~oThe urpone oir thia atudy v! a to further Invoea&tiak the

at~tavnt~ioti of t~he hydraulic rawu tiffot by usa of it k~w qutntity' of~ gan

ba4lla as piNAj(ottloa3 to oliitn~tfat any vlnVition I.n data due tu the piadhle

tum~bling of' an ogivalt, ~ All pvt)8as~ra roaid'lug were iroN~ off1 center-

line .locationa boa~iuie A Tph,,ri~oAl W)1tok vtao ituoutted.

As a projenotiJle mo'tos throxugh a tlttido it contitrually, ataeriateo a

presuennaroteld. It has been cjonjio't~urod that au tho projuei~le approaches

the back wall, this field mfia tý biiild up, oauving a high~ preaeurs juat

prior to Impact. I0or this reaon$~n pr'essure readingu in the pronant st~udy

were taken at the back wall ae clpse as possible to the im~pact paini,* Aloo,

a presbure wavcs genera~ted by the collapoe of the oavity ar'eated by the

Passage of the projectile through the tluitt, im~pacts take 'ftont o&nd rear

walls which have been~ weakonod by the parisage of the Orojectile through thxp~

tank. It is expooted thnt this pressure wave m~ay be a majvr contributor 1to tank wall. failure, Therefore, gages were also placed ±h the tan]K

interior an olose to canterline as poesoiblei in order to mea~tsre %11- jpress}ure genorater4 by the cavity collapse,

orujo)(sIdt.1si wmfrounaf A twok tillyd vkt41 witot' W~ oat-4lh A Idat bAvo 1*n

t~o oaqmoa~ dAtA witid ypxovi %un rvoulto. Th.o voki~nd %%ied4 vottr/fo, mixt~iro

to ALt~onuIAte§ WlJw hyduU ~lvk Ofmt Witr tua hurv uAad both apur±Qxhl

and oftv4l projotie,

AJU addit-t~uwd oi'otnmni wan cari'4ud okit du~n t~hQ ira aerie* ot

* ~ ~ ~ ote.nn Four blcmouIt~ p).~4~n were ))1AQ0c in~ tho I'*r wall) an At"WU b~aWere

* ma~de to detamiinw thoy vloity wit~i whio±h tkmae p~iug,% warea *aoated, It. was

fti~qe QoultI bu muetauz'ed t~ivomr~h ifrovmomiu uxul~ngo. CaIlcu&-atnu for

* ~thLa oxcahartge anti bej found inl Appendix 0.

'Nti4ns it w yiulisdo aut whkalk fortmvd it b~a.Ulno bth r.t opra

vd~t tot d&AA prsrvioun axorin~di'nto And tl oi ivaku~tLon of the hoo

attenuAtion of t~ht miixture.

Thu tarptt vatrial uded in tho sooonvd trloo of touto %ae a

watarifteuamool tiiAura, )nouinaaal ia a rmuJti-fibor, W~ron naterial.

oQaoXNuially prwdma*4 by the Du Pont Com~~ww &* uarpet paiddins. Pneuuaiol.

w~s *oalootod by Ol~atk (Rott d.8 urina hia expori'msint in vhook 4%tenu-

Ation beeauc.. it ia an open fiber wat~arial WhichQj OQn~tAina a controlled

aw of nau. ftnowuA1aIAtoI i nkit INrt~oiau'lary r rvotvwntad O'or usao in

tNoI -a11n, lPor one v*'aoavo potr'ulcurn ProdueLa vd11 dlatolvia the bond-

ing~ agent wu~it~ to hold t~he Pne~1naoel tagethejr. ror another, Pneumaoel

redtioad the ulaw1tbla voltumo of the teakt~ tAnk by IN~, oompred %At~h a tivik

r,)dkuoUiz of 7,1 fo~r r~I'MCAulted pol yra*hane fl ro-rotarzdent foam. Tn-

formtiatoi goonoorning. t~he phys1ical properties of PneumacaOl. o8.1 bo fo~uld

in Ajppendix A.

The experiment wA6 conduoted in Ithe Air Vorce Flight Dyrnaaiiice

L~aooratory (AliPVDL,)# Ouvi larw8e Nuwiber 1. ZIn ordor to establi sh. A ae

line against wh~ah praviou4 *xpqerimantal data aould be oompared, the

initial shots in eaoh of the two series .(water &alone at a tarvtt

ftaterial And water/Priewmaoel. &a a target material) were oonduoted

using J, in, steel balls as proje-atlUeav The final. shots Ur eaoh aezries

were, oonduoted usingi standard 0.%0 caliber ogival projeatiless+ Figure I

shows the general layout of' the ,principal. cotpobnente of the teat

(9apparatual (1) the gun mount,,(2) the projeotile velocity mneasuri±ng

system, (3) the .-080ý1U6osoPe tiggering system,'(4) the t~argetil

'(5) thea plug velocity moaaurin$ -systems,

ILI

Tnr

/11U.

& 4

OAAIC/7>.3-

Tho aun used in the initial shots of each, series was a emooth-bqrep

Q* -clier tea t barrel atteaohd too a Pr'aikford niont. The test

barrel was 9%t~ in*# lous and tht autual bore was 0.502 in, in diameters

The projectiles were stAndard J in. stainless a-teol ball. bearings

All bea~ring* were 0. k97 in, ini diameter and weighed 1239.1 araina.

The gun uned in the final shotb of each series was a rifled.-bore$

0,50-caliber, test barrel mounto4d on a Prwnkford mount; The tsbt

ba'rrel was 314 in. long and the actual bore wat 0. 502 in. An diamter*~.

The projectiles wor, standard 0.50 caliber ball. rounds. A 0,50 ca1±bor

ball round io actually an ogival projeotile constructed of soft steel1

with a brass Jacket., Each p~rojdatile weighed 699.8 grains.

The saanu breech oad bolt were used with both barroX~s. The breechIwas screwed into the aft ead'of the barrel and the bol1t vas attached

to the aft end of the breech. The bolt had a solenoid-actiVatod firing

pin which could only be triggered from the control room. The cartridge

was.'attAched to-tho bolt and the aseembly was then attached''to the,

breach. In order t6 prevent accidental discharge of the gun~while

personnel remained in the, tunnel, three switches-had to be Activated

before the gun would fire. The f~irat owitch was',on the bolt'and was

tumred from the safe to the-armed position after thei bolt had'been

pla ed in th~e ýbreacih. +h eo~ond, switch wa 3.oaot ou side 'the ne

etanc and was aaoti.atid by the'last anui leaving the tunnel, h

switch also6 activated warnainglights by the tunnel-entranceo -and in -the

*control room -The third Switch WAS 1Qc'Ated in the control rooit ands,

v hen :actiVated, colospd'the circuit,-and fired the guM.

+Between the muzzle of 'the gun. and. the tArget were two velocity

S( screens, exaotly.2. feet opart. -The. screens were#. Oon~stxkt~d- 0. paper

7

xi,!sncriiosscd with -a oontinuoue- horWv~ntal -strip ofnitallici pyint.ý

*The strip was- Inq wide and- thtý ao)pa~ation between ejaoh 'atxrp 7was,

*in. Theu paper, was mounted b~etwolen 2 plates Mhd a, 90 volt D.C.-

charge wias.'apiplied. across the pl~ates through the. strip on the pap)er.

When the P~rj.;cti~e passed through the. papr thairdiiit was brke

and a trig'geriig -pulse was genex'ateoI. The. scre ens were coo~meoted to

VBeckmwn timrsoe and the elapsed 'time betweep 'suacesstve pritjectil,.+

impacts iwas nieasured.

A single sareen was mounted 2,in. in firont of the' target. "Thae

pulse generated -by the projectile 'passin' thog this a cre en was ue

'to trigger the sweep of the oscilloscopes.N

* .The target was a rectanuar tank 24 'in. - high, 30 in. wide, and

24 in. deep. The topO, bottom, and sides were in. steel plates,

kreno~rooe wt bnso 2 steel angle iron. The front plate

AI was remo~vable auid -was made of'- in. 2024 alurninum. The.,plate. was held to

the tank with 'eighteen 1 in. "CI clamps., Zinc 6hroimate was. used .as, a

sealant, between. the plate and the tink. At 4 in. diamneter hole iiae out

in the centerý of the plate anhd a .1 *in. wide circular collar was' used

to hold an .8 niil sheet of plastic-over the opening. Ilight. sheet metal

spreWs at aohed the collar t19 . thei plate and~ a bead of4fte zichrcniAtde*ý

aipo, used.t sea3 th collar" to the pate

The back plate -was also: removable. and was made of;

*aluminum.. this plate-was held. to the tainli byt~t- n '

clMps. Zinc,,ohrtmat6 was al.so uoda. as a eadfl bettween the-p.t n

* te tnk.A 6in, square hole was. oait in the oonter -of te 4~~~t

aMd an; 8 in. qukepat of in,., 202.4 a1.uitr~um I ou to. the

(bao1k plAtt. Si~teben+ in. bolts ýWdZ'O usd attac tho suar to M~1

'8C

IT .1 -" - . 'T - '

bao plate Geea Eleotro T!sealant_ was sed to. seal the sau~are.

to the bdok plate. m'g~ shows .'the'. tra~ksuc an' k. ow-6u't plug.

arrni~rne-ocn teBin. square plate.

~ iiIii .sgeQblow ou t plugs

gage 4 -gge -Pressure

W~m----~ transducers

gage 6.

Pigure 2Transducer~ and B1i out Plu Au*.agmn

9 rtane'n

I'-, ~ :Ai

_ K . ,-4 ~~~gf' ~ - , . . F'~~' . .~ . -

Four ,conical blow.-out plugs were placed in the square plate, 450

to either side of the vertical centerline, and 2.82 in. from the

center of the 8 in.. square plate. The plugs were constructed of 2024

aluminum and were truncated cones. The conical taper of each plug was

30-', the.top surface was •- in. in. diameter.. Each was 2 in .. lng and2 w 4

weighed 405 grains. They were sealed and held.in place against the

static water pressure by 0-395 tpe aircraft grease. Figure 3 shows.a

side view of the plugs.

scale • 2" 1i"

N.•

-NN

Ift gre 3

Blow Out Plug (Side View)

-10|

(:I'• lO-

, bac. .a.i___

S ..... .. ;.... . .. ._ L .. .4 .. .. ... .iL , ' .. . . . .... •... . .• .. . ..(e. . ......t....... ..io. . . . ...).

,'r .,p. • rw. . . , ,r' .. . ... .. 0 ..

t Four Kistler 20.AW pressure transducers were mounted on the

vertical and horizontal centerlines, 2 in. from the center of the

plate. They were threaded into the plate and the pressure sensing

faces of the transducers were flush with the inside wall of the

r square plate. This arrangement was chosen so that at least 2 gages

would be close to the projectile impact point.

Two other Kistler 202A1 pressure transducers were. mounted insideI, 1the tank by - in. aluminum tubing and fittings. Both gages were2

mounted so that the pressure sensing face of the gage was. pointed 1800

to the path of the projectile and on the horizontal, centerline.

These gages were on opposite sides of the vertical centerline, 6 in.

from the projectile path and 12 in. forward of the 8 in. square plate,

i.e., at 12 in. from the surface of entry. These gages were used

to record the collapse of the cavity generated by tlie passing

projectile.

Two velocity screens were mounted behind the tank. These screens

were exactly 2 feet apart and the forward screen was 5 in. from the

back face of the 8 in. square plate. These screens were used to

measure the velocity of the blow-out plugs.A1o0 o1o.o ,,A wooden catch tank, 8 -ft. lon,3 f.wdad12ft

deep, lined with a plastic sheet, was used to catch the water spilled

when the target tank was ruptured by the projectile.

Instrumentation

Kistler 202A1 pressure transducers connected with microdot

coaxial cables to Kistler Model 504D dual mode amplifiers were used

S" 11

to measure the pressure. The back plate was drilled and tapped and the

transducers were threaded into the plate. The two transducers inside

the tank were mounted in an adapter used by AF Flight Dnuawics Lab-

oratory for Kistler gages.

All pressure data was displayed on three Tektronix 5103 N/D12

dual beam oscilloscopes. Two pressure readings were displayed on each

scope. The scopes were triggered by a screen mounted 2 in. in

front of the tank and a single sweep was used. The data was recorded

using Polaroid type 47 high-speed film.

The signals generated by the passing projectiles on the front

and rear velocity screens were recorded on two Beckman model 7360A

universal timers. The passage of a projectile through the first

velocity screen started the timer and the passage through the second

screen stopped the timer. The readings were in microseconds and were

then converted to feet per second.

1

( III. Ftperimental Procedures

Forty four shots were fired during the experiment. The first

18 shots were fired to establish a cartridge loading procedure and to

Iestablish a powder charge versus projectile velocity curve. The • in.

steel balls were loaded in a modified 0.50 caliber cartridge in the

following !nanner:

I) the primer charge was attached to the cartridge.

2) the powder for the desired projectile velocity was weighed

and poured into the cartridge.

3) two strips of teflon tape,-L in. wide and 2 in. long,

were placed over the end of the cartridge, the second strip perpen-

dicular to the first.

S) the ! in. steel ball was placed on th'e tape and then ramned

• . Into place snugly agpin,_t thoe powder char e..-

Using this technique, the teflon tape kept the ball snugly in place

and also acted as wadding to prevent gas flov-by as the bali moved

out of the cartridge and down the gun barrel.

The first 3erieo of 16 test shots wan conducted using water an

the target material. The projectile used for the first 13 shotl was

thel in. steel ball. The initial velocity wan 1000 feet per second.

Succeeding velocities were incrementally increased to a maximum of

3091 feet per second. During these shots, the recording equipment

was tuned and the refurbishing procedures between shots were established.

The last 3 shots of the first series were conducted using standard

0.50 caliber projectiles. 1he muzzle velocity was 2720+ 50 feet pei-

ascond.

13

GA/Yvi73-3

The second series consisted of £O shots which were fired into

a water/Pneumcel mixture. The projectile used in the first 5 shots

was the in. steel hinll. All shots were conductea using a ful

powder charge which resulted in a projectile velocity of 2790.I_0 feet

per second. The next 5 shots were conducted using the standard 0.50

caliber projectile. Again a full powder charge was used which resulted

in a projectile velocity of 2613+±75 feet per second.

The procedure for each shot was as follows:

1) the cartridge was loaded for the velocity required.

2) the instrumentation was turned on to warm up.

3) the four blow-out plugs were put in place as required.

11) the plastic sheet covering the impact point was replaced.

5) the tank was filled with wa•ter.

6) the front, rear, and triggering velocity screens were

put in place and the circuit to each turned on.

7) one at a time the circuit to each of the five velocity

screens (2 in front, 2 in the rear, i triggering) was broken to

insure that the screerv3 were functioning properly.

8) the three oscilloscopes were s-t on single sweep delay.

9) the Polaroid cameras were attached to each oscilloscope.

t10) the Beckman timers were reset to zero.

11) the cartridge was placed in the remote firing bolt, which

was then secured to the breach of the test pui.

14

.~ ~ ~ ~ ~ ~ . ... ..

GA/.VC/73-3

12) the switch on the bolt was twitched from oafc to a r.

13) the tunnel was evacuated and the safety switch wab

activated.

14) the shutters of the three cameras were opeccd.

15) the firing switch was activated.

16) following the shot, the safety switch was turned off,

the remote firing bolt was switched from arm to safe, and the bolt

was removed from tile gmu breech.

17) the Polaroid pictures were marked as to Lhot number and

scope, and the velocity data from the front and rear screens was noted.

18) during the iihots with the Pneumaccul, the proJectili1

passage through the Pneunacel left a 1 i. in. hole which wan repacked

with Pneurnacel to the sane density a8 the orirfiial material. Two inch

,quares of lPneunacel w•re cut, placed in tihe hole, and punhed into

place

I

S (+

=.5

Se __i_ t'V -

.2 ,:-, ~Sixteen test shots wore conducted during aeri•c• 1 (wat.r' 0!nZ•), . "

-' No data from shots numbered 2, and 9 were obtained bucausa of fAulty

triggering of the oscilloscopes. The datrx for the 13 Suoconefl

shots were displayed on throe dual beam oeoillonoopes and wero

recorded on Polaroid photographs as shown in Pigure 4. The truaes

run from left to right. Positive pressure in read below the zero

reference line. The time reference is from t4he patsage of the pro- Hjectile through the velocity screen located 2 in. in front of the tank

entry point. At a muzzle velocity of 2700 ft/sec, the time botween

passage of the projectile through the velocity screen and target impact

is 0.061 mil..iseconds. One large division on the Polaroid photograph

is equal to 1 cm. The Polavoid photographs for the 13 successful

shots in series I are uhown in Figures 15-27 in Appendix C.

Tabulation of the projectile velocity, back vall impact time,

peak pressure at the back wall, and. peak pressure generated by the

cavity collapse for .series I is shown in Table I. The back wall Inpaot

time was obtained from the Polaroid scope pictures. The traces show

an increasing positive pressure followed by a series of positive and

negative pressure spikos around the zero pressure reference line. ,I-t

was assumed that the return of the trace to the zero reference line

and tCe positive/negative spikes were e'ised by the projeotile impaot.-

ing the back -all causing the gages in the wall to "ring." The impact

16

(A/MC/f '3 I

; '"' •',.ShotS8

P.. ........ . . .i .*,

I', do"eiI-. 4...'

Gavls 3 A 4, 0.5 msec/cn

100 psi/cm

Gages 6 &6 6,.5SRsct

£ . 100 psi/cnm

Projectile velocity-.2296 fps

Figure 4Scope pi~cture) Seriels 1, Parv 1, Shot 8

171

4

bkbliti fteml ort Qt 8.'to L

~&U -

=0 $. 40 4 Y 40 N ND

'p 00 DATA

Nj 70 ' D 44D NO AM 40 N4* NO UATAJ

5* 1391 1.6 50 ND NO sD NO

6* 1406 3. e. ti "k N 50 ND DD

I, L '/37 2,.5 AV) NI) 100 W4) N)

8"2.2 20 ND 1•qO N) AD

S9* VO DATA

10* 2739 1.9 20 20 VD 190 ND ND

11* 292• 8 1.7 VD uD LID 170 ND 140)

12," 2928 1.7 QD fn ND 120 ND! 140

13* 3091 i, 30 20 ND 150 WD 130

14,4* 2770 0.7 520 '120 630 630 1O 630.154* 2691 0.7 ND ND ND M70 590 590

16** 2680 O.8 QD 1D li t OO 800 a!)

*1/2 in., soherical Drojeatt-ile

S0. %O ca.llbez ogival, vrojectile

ND No data on that, gage

A8

~j ms wasWe as th triomal trviid the S'Oart oti MOA %mot~* 't) $f

Point wb*er Utie tmobepin to rstumin~b the sew~ rotemme~to 3w

flh. Ampaut 1WJjiw tar' the *p e.+ica1 proQeo~t' ls 4or"Ate as ve)foatit

tvnersaea, Romwtw r the 1woat time fto this 4vat pwnseatilov to.

approxita~tely tho itue tor tho apbotAn1 pmjot~e*b Wad aiI t the

mwUI v2lao*týy. its og#Lval. prQjeatUos ha th* SAW e~io~

dimator as the sph*ri±aa1 pmjeoiati.ea but they' ta'e 51 times *A

MILOS (am %h'ie timen thea k1inetia enetg at the uam* Ve).ooiy),

IT the caLvaJ. proectile* didc not t~imble, the 1ax#er kivi~tia 4netrp

andt momentum of the agivRl Wroiwbile coupled1 witih Aai equive2Lnt

&FIAg for both pxvjeatiles would. reault in laee deaeomlrtion tar' the~

agivAl projeatila atnd~ a vaoQutquot lower buak wal i. mpAct tlima.

How~eve, as is ahown later, the oeg±val projeotile do~es tumbleo pre..

aenting A ).argr Area to tha tMid. k~soaupe t~hia inv*oran in~ aroa

r~eaulta ini an ±VkoreaLO in dracr, the iinp at i4rno shouLd be hig rz than

It I-st unlene the tmnbling does not~ oacur until the proj eatle is

almosat t~arowmh the tank. An ie indl.oateci in the suboequent Dihscuusion

section, this is the Coas. Peak prossure Wx the f'luid at the baok

.4wall wan takan ftromr th* Polaroid. picttv -of at Sv .eei3f 4 5, anid 6.

iiio tim sol 810is v"ry~ eaati,(0.5 mseo/ota) so that the prtsburj -build

up on~ t~he Mack w4l1 oould be saexa. The poak; pmasure itan~e ýY' 1*

oawJ~ty collapse wAs taken from bbs Polaroid piaturto of gaa I and 2.

fte tlew acale for these gages was large~r than thAt fox, gages 1-6 iii

order to inoure the reooorditi of thoe cavity:.oollapea, ftwtaver, ..the.

(w . 19

U-mo oo*40. Wie OU1% *a&1y O$ tifeeom.Th at pe w Iv. *1 "

Ctue ta Ie 0440ine "4eOQUI (n t ~~1t o ) Veox ini NVAc assi~witht~ he ym pmoum avo Ahe %&*it wall

Iod' 140t~ Shes wer aoruamted dmii4W milrioa 2 (water/Pneweo~o).

The Polaroidi p)hataxnp4he tar the 10 aPhq%, ame Almw ift Pini ,es.28-0)

In Appen~ia 0, Tift ation at the Projectile Poloat VoloattyO biaqk

1411 lmRaot ttmo, Vak pr.essu', In %he t1ul1 At. the back wall,. &M

peak pt~assu #,onoratad by tho oavibtv oo11apse tor utritrls 2 is shown

In TAbl, 11,

3e~igea y The firat 13 ahots of aeries I wore condu.cted moizag

Sin. steel apherea am projectile. Proectile velocity was pro-.

'eorvusvly inracraned frorn 1000 ft/aeo to ')01.1 ftt/ue, A gx-Aph of'the

pNak proeeairo 0 the wall vertiua pro)jectile vetlocity in ahown in

Figure V.iTe 10 eihots 6rn which data were eaunesoeaully oolleoted

ehow an inoreaoo in peak pressure at the back w~1l &0 Veltoity in-

oreasess, a reduction~ in the back wall impact tittbo, and an alm~ost con-

stant cavity collapie prosoure. Aa can be neon from Figure 5,a fair

qorr6la'bou -eX1itsa: bbW491% tho ,peakpressumv& a~t the.-back vll 4t)

we~pe*nta4.l d~ata~ obtained' bý, Clark. (Ref ),Tho d fereace *rk O&ta

right be' due tU the fact that the gages in Ws~t btudy w4ere iMountad in~

tho back wall (i.e.', 2 ft. fromt the0 impaot Point) and wore onliy 2 in.,

from oenterline, The gatg. uaset byr Clai* from vhloh the 4'L_ in 1"ihurv

20

* AtI

Sho lm~~ag$ Y~k b14e Tarik IokWalVoloo.Lty WAll agoT~~ IT Gý,

L* 25 1.6 .0 0 .0 0.0 00. 0.0

20* 2750 1. 5 6.0 0o0 0.0 00 00 06.0

2A 750 1.6 0.0 0.0 0.0 0.0 0.0 0 .0O~

40, Z ~7 SO 1.5 0.0 0.0 W) 0,0 0.0 0

5M* 2030 la4 O0 0.0 0.0 0.0 0.0

6A** 268 L0 0.0 0.0 1D 0, .0 0.0 ý 00

7A'N* 266o 0,9 0.0 0.0 0.0 0.

SA** 2645 1.0 20 10 4D 44 0.0 0.0

94* 2$3., L2 30 30 vD 0. 0 0.0

*1/2 ini sthe~loa3. tDreoiA.ele..

* '*,0. 50 cagibor 100, ectile

No, odataon th#+ga-ge

21

GA/MC/73-3

was obtained was 8.7 in. from centerline but was only 9 in. from the

impact point. If the spherical projectile had moved with a constant

velocity through the tank, at an impact velocity of 1000 ft/sec,

back wall impact should have occurred at 2.0 msec. In fact, back

wall impact occurred at 5.8 msec for an impact velocity of 1000

ft/sec. Thus, the npherical projectile slowed appreciatively during

its passage through the tank, and a pressure gage located near the

impact point should read a higher pressure than one farther aiay.

This is also verified by Clark's data. The pressure reading from the

gages located even closer to the impact point are higher than the

gage used for comparative purposes. This gage w-s selected because

it was the closest to the back wall. However, as can be seen on

Figure 5, the pressure generated by the c.v!tv coliapse is indenendent

of velocity. It might be assumed that since the pressure at the back

wall increases with velocity and the pressure generated by the collanse

of the cavity remains consatit at a much lowerL value, the damage

causing mechanismi is, the initial, pressu'e wave. In the case of

spherical projectiles :thi~is- the case. The separation of the flowcaused by the passage of the sphere throu;h the fluid is minial" and

the cavity which is created by this separation is small. Thus, the

collapse of this cavity creates a:wea, pressure field.

The second set of. shots in series 1, a total of three, was con-

ducted using 0.50 caliber ogival projectiles. The projectiles had

about 5.5 times the mass of the steel balls. For the same impact

(222

ix7 T

-1* -. I Xi4, A 14

Utt- ... .~ .i .. .i1 ~ .J K .. ..

M E 1 1, 171, __

I' x i TI''4.,7.

-R 4

lw.. t..x

'-H A4 '7k 4I *)

tU~~hL f~ ~~Y ~ ";c ~i4a 5pl l-h: L tt t'm i$

NI 4t-f

.1 M

04.Pre.iiwi.f4ire7"". jpVA : i

V~.cttepa ressure. at. the.& '11 was abo~ut four times t4th-

~ek1.~~ssr gnratedb the steel ballR moving, -throuh the fluid.

$,Aowe~er.,ý th&.t prensuro. gen'or d~yA ,cl~s f~e vti

virteý byg ed.~pt biM vdý

Arg.cAvit rwa ted beaue as the projectile i~e hog

thefli it trbet:prep0cnti~ng a lrrsrfear to the- fluid.

The. tuiabling of the projectile can be seen in Figures 69 These

stills were obtained from a high speed filmh taken byý, the, Air Porce

F1litht Dynamics Laboratory (AFFPDL):on 3 June 190 Th ilm W~astaken

during a test con~ducted by -ArPfL in which 0.50 caliber. ogival pro-.

jectiles were shot into a 2 ft test cube filled with water. The pro-..

Ijedotile impacti velocity was 2686%ft/sec and it impacted the tank

p~zpendictular to the front face. In Iigure-6, the projectile is 1 -ft.

into the tank. FPigure 7 sh .ows the projectile approximately 141 in.into the taink' and just begi~nning to tumble.

vig'ure 6t Ogival -Projectile ini F'i~ur 7v Ogival Projectile in.-Test Tarik Test Tank

- - ~241 ~

* OGA4I /73-3

65fron

As can be sLeen in Figure 8, the projectilJ.&is 15 in. into the tank ..nd

..has now tumbl ed 9V,-,: Note the large cavity be-hind the, proj~odtile.

Figure 9 shows-that the proj cctile i s.; now 17 T, . juto --te- taink b~u

that it is" still rotated 900.. The cavity has grown larger still,..

Figure ~ ~ ~ ~ ~ ~ ~~ .8, OgvlPoetl i iue9 gv rjciei

Tes Tan Tes Tank.

wh igure Projecivle tromctled in olonofthniner 9,ot cvlPojductied in

the projectile failed to tumble. In that cane, the cavity which was

created was very1 small (Ref 9).

Thus it was assumed that the projectile tumbled during the second

set of shots in series 1., and that this tumbling created the la*'geý

cavity,. the collapse of which was recorded on gages-1 and 2.

Visual observations of the target during impact by the 0.50 caliber

ogival. projectiles showed that the plastic covering the 3 in. impact

hole was blown out and water was blown out of the hole with sufficient

foree to spray it 12-15 zreat, up the tunnel. No such effect was noted

( during the tests using in. spheres as projoctiles.,

25

GAA4/73-3.

,Serie, 2. The first set of 5 shots in series 2 (water/Pneumacel) were

conducted using . in. steel spheres as projectiles. Because the higher

peak. pressures were recor~ded during part 1 of series 1 only at the

higher velocities, all 5 shots were conducted at nominal muzzle veloci-

ties of 2700 ft/see. Higher pressures were desired during series 2 sothat any possible attenuation effects of Pneumacel might be observed.

A comparison of tbh, peak pressures during this test and the peak

pressures obtained by Clark (Ref 3) is showa in Pigure 10. There was

no measurable pressure field generated by the coliap6e_ of the cavity.

Because the only difference between the first sets of series iand

series 2 was the inclusion of Pneumacel in the test tank, either

the Pneumacel prevented the formation of the cavity or completely

attenuated the pressure field generated by the cavity.

The next set of 5 shots in series 2 was conducted using 0.50

caliber ogival projectiles fired at full muzzle velocity (2650 ft/sec

nominally). There was no pressure measured at the back wall prior to

the time the projectile impacted the back wall. And while there was

a pressure field generated by the cavity co±lapae, it was only 20-30

psi, compared with 500 psi without the PneumaceJ. present.

During set 2 of series 1, the cavity collapse pressure blew out

the plastic covering of the impact hole., In the experiments with a

Preumacel filled tank, the plastic remained intact except for the

hole made by the projectile entering the tank and there was no water

blown up the tunnel. These observations are taken as further con-

firmation of the fact that the Pneumacel significantly reduced the

hydraulic ram effect.

26

1, • .

GA/M, /3-3

.. .. .. ... .

Cl :-

H~ -

......................................... V. . . .. .. .

CLa.

-r - 4

II Hq H o ocPrssr (,si

3I~a4-H0 27

• • 0GA,-`M/73-3 .

( 'General. Most of the analytical work performed on the hydraulic ram

effect, Seaberg and Bristow (Ref 6) and Alverson (Ref 1) for example,

has focused on the pressure wave generated by the projectile moving

through the fluid. This was assumed to be the major contributor to

massive fuel cell failures. Alverson (Ref l.) analyzed the hydraulic

-I. ram phenomenon by examining the kinetic energy of the projectiles.

Shape was unimportant. The higher the kinetic energy of the projectil

is, the higher the energy transferred to the fluid ana the greater the

damage to the tank. As a result, experiments have been conducted

using high-velocity spherical projectiles. Spheres do not tumble as

they pass through the fluid so the flight path can be fairly accur-

ately estimated. A pressure-wave was generated by the sphere passing

through the fluid and the experimental data and the analytical results,

such as those obtained by Clark (Ref 3), were in agreement. The

cavity created behind the sphere was small and the preosure wave

generated by the collapse of the cavity was sienificantly umailur

than the original wave. Thus the second wave was neglected when fuel

cell damage was analyzed. However, the tests conducted during this

experiment showed tl',t the pressure generated by the collapse of the

cavity was approiximately of the same magnitude as the first pressure

wave generated by the projectile. The cavity collapse is also highly

directional along the path of the projectile. As can be seen in

Figures II and 12, the cavity folloviing the projectile collapses not

oray inward but also along the projectile line-of-flight in the

direction the projectile moved.

28

" ) The results of this test suggest that when a full tank is struckI o by a high-velocity ooival projectile, the followinrW sequence of

events takes place. The projectile passes through the tank creating

two "small" holes; one on entry and one on exit. As the projectile

moves through the tank it creates a large initial pressure wave in

front of the projectile. This wave strikes the rear wall, but the

wall can withstand the pressure because it is still intact. A- the

projectile moves through the flaid, it also creates a cavity behind

the projectile. This cavity expands and then collapses, generating

a pressure wave as large as the initial pre!;sure wave. However, by

this time the projectile has Pased through the rear w,.1l. There is

a flaw in the wall and It is at this flaw that the cavity collapse

( pressure field is directed. And this is the , at which thn mss irva

daniage is done to the t,1nk. This sequence sutie.ots a ,oi',lo of areas

II

Figure 1.1, Cavity Created P4,ure 12, Collnpee of Cavity

by Ogival Projectile Creited by 01ival ProjeeUle

29

OA,/MC/ - 3

Sin which t.uture work could ba porfoi'mod. '11o oival projeotlos uwod

in this study did not twtble until they were Appftrxi,|atoly W ,qy through

the tank (I ft. from inmpaot point). Since projacoLe tumblin. io

'I; important to massive fuel cell damage, it would be danirabl, to hayve

the projectile tumble an soon an posuible, An 1nveittiOn of the alse,

shape, and anglo of impact for various projectiles and the Offeet oý

these variables on the initiation of tumbl~in could lead to doevelopusnt

of projectiles with a higher.kill rate than thobe preaently used. A140,

because tumbling is a factor, fuel cell geometry could play cm important 14

role in reducing massive damage. If a cartAin dlstAnco is required for

a projtvctile to begin ttunbling once it impaots a tank, fuel tanks could

be designed such that this critical diatanoe eculd never be obtained

by a. projectile.

"".

W ' .. . "_.,,

Is While t~he dat 1ar WOt 'p4 tt Wa. liftttdý It oostninm OU.er18

%~*ea t*~ W eQ f i'ir# andi *ztu~nds Qtat work thro~Al1 the use o agt a

2, A ermall OMIU~b of pgav IV% a N44ol-aw okit*Wr t~g4t$.oantly

roducen the po~kpreour mavuv*4 At %he bauck wa1. miniam4$ b the

paaS~e of the prajoati10 th)'ai4~h the fud

ý.. A anudi amount of' jau i~n A~ j\iul--foam mtxtum .r 1n'o either nduioea

Vie eaW, of' the aavittq aore.ot.' by, the pi&awi at' tho vmjeat&1ui thxaU~hKh lio redtioen :thopep urv :: 'wrate4 tby the ca1Jap1Uo of the

*"foat ,'a ineff'.ot~ve lboootise lttlo It 11' y eAv.t~y caiipoo provur'e le

n~enorm ted,

5. ho pr'eanur'e rtiolc oveated by' the collapseofa the cavity

Qreatsd by the P408eago of tht ok~iVAl projeotile tlwu'guh thq fluid Is the

mAjot' cause of massiVe full. tI'M ca]ll damuige.

1. UnlLY ogiva pr*ctlt iO'hou be .4,d-Jjatdin h

attAnutitrn of tho tkvdmu~iAo ra Vt

2. Te~sts shuuld be ltonduo'bed tveing thini wall.ed fuel 091154.

33. A fo~aj. should beQ deiO TdWhich will iounbifle the aho ok.

attenuation of fac t of a giis-filled fiber with \thlO flem a resi5R

(. oha~raote~istios of rýtioxtlated polyurothani foawh

CA/MC/!73-3

•;•Bi~bliography:

1. Alverson, R. et al. "Shock Effects in Fuel Cells." SRI ReportPGD-7708. Menlo Park, California: Stanford Research Institute,(January 1970).

2. Bristow, R. J. "Design of Hydraulic Ram Resistant Structure."Paper 10-11, Seattle, Washington: The Boeing Company, (1971).

3. Clark, J. W. "An Experimental Study of Attenuation of ShockWaves in Three Mixtures." M.S. Thesis, Wright-Patterson 7ir ForceBase, Ohio: Air Ferce Institute of Technology, (June 1972).

4. Lavery, B. Personal correspondence to John R. Breuninger, Jr.,(January 1973).

S. Northrop Corporation. "Analysis of Hydrodynamics of ProjectilesFired into Fuel Tanks." Technical Brief NB70-247. Hawthorne,California: Aircraft Division, Northrop Cornoration, (January 1971).

6. Seaberg, C. T. and R. Bristow. "Fuel Tank Impact." FADS-37.Seattle, Washington: The Boeing Company, (January 1967).

7. Stepka, P. S., et al. "Investigation of Characteristics ofPrcs:ure W1aves Generated in Water Filled Tanks Impacted by High-Velocity Projectiles." NASA TN D-3143, Washing-ton: NationalAeronautics and Space Adoinistration, (December 1965).

8. Torvik, P. J. and J. N. Clark. "The Reduction of Impact InducedPressures in Fuel Tanks." Unpublished Report.

9. US Air Force Flight Dynamics Laboratory. "Hydraulic Ram Study."AFFDL Project 43630109. Unpublished Report.

10. US Department of Housing and Urban Developrng'nt. "Carpet Cushion.".Materials Release No. 768. h`'ashinton: HiUD, (June 1972).

11. W'inters, D. 11. "Dynamic Response of Water to Ballistic Impact."MS Thesis, Wright-Patterson Air Force Base, Ohio: Air ForceInstitute of Technology, (June 1970),

"TFOR" 'O•"++ ++ --- + - i 1, -1 -+ . .. . .., , I" ý I

Appendix A+P-rieuma -e3.+ - ,.. " "

Pneinmacel, -shown. in Figutre 26i' is a' Dlu Pont product presently

manufactured commercially as a carpet padding. The term "pneu.•acel"

is not a trademark; it is a generic designation for materials-lmade of

permanently pressurized cellular fibers. The word."pneumacel" is.

defined as: A resilient, pneumatic, .strand, sheet, or cushion composed

of a cellular polymer structure having predominantly closed cells that

are inflated to higher than surrounding pressure with two or more

gases, one of which is essentially impermeable to the cell walls

(TRef 10).

A supply of flu Pont Pneurnacel, Lansdowne M~odel 5000, '.Tas maede

av'ailable for this study by Dr. Bernard Lavery, Christina Laboratory,

DU Poixý Corn. , Wilmnington, !)elawre, 19898. Tne folio-WinF, i~nfoxi'ation

wras also provided by Dr. Livery (Ref 4).

r4-~t Cbaracteristics

Randomly oriented, thermoplastically bondedPnevv~acel fibers.

Density: approximately 1.5 lb/cu ft.

Thickness: approxiirmately 0.475 in.

Fi*ber Characteri stics

Small, vniform, polyhedral co~(Pip, 27).

Thin, highly oricn-ted cel)wal .

Chemical nroperties: I'Dacron" P~olyester fiberinfl ated with a fluorinated hydrocarbonblwna gent.

Denity: 1pproxi~r~ibely 0.102-1 7mr/cu cim, i2% of the ý--oightis injflatent.

S+ : + ,+ ++ - + ++ ; + i] •!,++ i ;• ++3 5 • + : : .. + + i• + : y + ii

$ p

'a

-,-� � - 41 IrPW�WW�fltq

* II.

4 '1'* f1.� (I,

I' I'

I. <LI

Figure 13

Pneuuioco

'WIV'r"k"" .m\4.,,,�<

A �r'�t" a,

4;KK.,,L 4� i#t '

- tJ�Ax� t- 1 .. <'IL. �'d�

'- '

\ij, \14 ¾,

t I.

./ , �tr"�*' yra i. 1'

r1 Ii

'1 � .,Mt4'%�kiSii�ku 1 ',tI A�-�'wi� '% ,��,&i�'M'At� NflU

Figure i4* Cr9ss�se�tKV photomicrogr�ph gf Pneuinacel

( magnified 4000 times )\l.

'I' 34C 'Iv

OAAýMo/73'T

Appendix B

Bl1ow Out' Plugs

Four blow out plugs were placed in' the back wall of the target

tank in an attempt to determine if the momentum of the plugs after

being blown out could be related to the strength of the driving

force, a shock wave in this case. If a relationship could be deter-

mined, this technique could then be used in future tests. Rather than

placing expensive pressure transducers near the expected projectile

impact point with a good chance of the transducer being struck and

destroyed, the blow out plugs could be used to determine the shock

strength.

The plugs were constructed of 2024 aluminum to reduce the mass.

They were constructed in the shape of truncated cones so that if they

rolled on exit there would be no binding. T-Y- vclo'ity screens

were used to measure the plug's velocity. igh speed photography

would have been preferable to determine plug velocity, but it was

unavailable at the time due to priority mission requirementq.

Initially, the plugs were placed in the back plate and were

sealed with zinc chromate. in order to hold the plug in place, a

strip of masking tape was placed over the plug end. This procedure

was unacceptable because the seal pas voor and the tape held the plug

so firnly in place nothing was happening.

The plugs were then sealed with a fill of aircraft grease. The

grease provided a watertight seal and enough virface tension to

hold the pliugs in place z'-gainst the w.,ater st4 '.hic pressure head.

'lowever, w"en the shock hit the pl•;, it wa.ý blo'.n out ao desired.

•.,n~n the shock •~it th p£< ibw.•••

"Velocity data on the plugs w.,as obtained onLy during the last 4

shots in Series 1. The foUr velocities were: 29 fps, 82 fps, 236 fps,

187 fps. During shot 15 when the 236 fps velocity was recorded it was

later-*determined that the projectile had lodged sidewise across the

hole in the back plate in which the blow out plug had been resting.

Thus it was a little more than a shock wave that drove the plug out

of the hole.

To determine the force the following equations were used:

V2 =2 a S

and

M aP A

where V is plug velocity

S is distance plug moved while force iwts applied (3/4 in.)

M is pluv mass (405 grains)

A is surface area over which the pressure acts (l/161rsq. in.)

Using,, P =-4--p~E 3S2AS

the pressures detexi.ined for the various plug velocities were:

Table III

Computed and Actu.%l PressureDuring Plow Out Plug Test

Cor'outed ActualSho)t Nio. Voth Pro.'wre Pre.:sure__ _ __ _ __ _ __ _ _ __ _ __ _ _ ______ (psi)

13 29 60 150

282. 630

i5 236 399• 590

21509 80o

GA/Mc/7.3-3

The data appears close to the actual value in some cases and

co:pletely •rronlg in others. This i•q due to the fact that if the pro-

jectile hitoi on, or very close to, the plug it is not only the pressure

wwve that, drivc3 out the plug but also the actual i.mpant of the pro-

jcctile. This test resulted in little usable data.

If the velocity of the plugs could be detcr.irnined from high speed

photography, more accurate data should be obtain-d. A plug could be

selected on the film which was not near the imaet point and was

thi2 acceer•.ted J�i�]7 rby the nressure wave. Firther stu'dy of this

Oata g-itheri•,r, metliod sltould he accomplinhed.

37,

Appendix

Oaci11ot!601pe Ptues

Trhe. Polaroid photog~aphs of -the p~rdvsur traces. for' 4L, suoo f'U2

'tests foll~w-, n~es -15. - 7 arq foriý- series -1 (wate only) k~d~

Figure.& 28. - 37: are.,fo'r series 2 (waterApneumacel).

Alltraces ru.from left .to t'ight. Positive pre~sr sra

elwthe %er'o-re'ference line* The time reference Is-from the passage

of ~the pro'Jectile through the triggering screen located 2 in.. in front

of th e tank. One large division on a photograph is equal to 1 cm*

Gages 1 and 2 wer'e 2.ocated inside 6he tank. 'Gages 3,o 4, 5, and 6

were located in the back wal.l of the tank near the projectile impact

38-

klt, '¾ A '.

* . .*...

-.

.... ***P•h

,q .

1' . GA/MC/73- 3

* IShot. . i••• " ., ... !. I i . i .1 . . , ,•Wa ter

-y7:4 l . ,Gages 1 & msec/cm

H ,7- t - t - - -- 2 0 0 p s i/c m

}: 'Gages

3 .&.4 ., 2 nisec/cm

I . . " .;•200 psi/cm

S.

,

; . .... . .. Projectile velocity-

1000 fps,

, Figure 15

Scope picture, Series 1, Part 1, Shot 1

39 §

fl•t

,.

.

., -

.

................................................................................ 4-•'I

GA/MC! 73-3

i(.J .Shot 3Water

Gages I & 2,. 5 msec.

r20 psi,

-~2 s,., -

..i. .....Gages 5 & 4, 1 mse( ': a

IA ~ .20 ps

Projectile velocit-1700 fps

(9 Figure 16Scope picture, Series 1, Part 1, Shot 3

40

GA/t-, -3

Gages 1 & 5 msec/cm

100 psi/cm

Gae . scc

c,~~~ae 3i;u , &le I, Pa! msec/cn5

[' Se psi/c

1MW

GA/ML/73-3

Shot 6

Wa ter

Gages 1 & 2, 5 msec/cm100 psi/cm

F.

it!

Gages 3 & 4, 0.5 insec/cm

100 psi/cm

T.i

Gages 5 & 6, 0.5 msec/cm100 psi/cm

Projectile velocity-

1406 fps

Figure 18

Scope picture, Series 1, Part 1, Shot 6

2

GA/MC/73-3

F wa;Iges 1 & 2. isec/cm

"... . psi/cm

.,ges 3 & 4 .5 msec/cm

;00 psi/cm

LI,"IL

. 'l IMeA.a~~tl..4..~...L~,.... ,,a.~ . ant ,. *ges 5 & 1: ;o' DATA

rojectile :ocity-

2037

Fig, 19

Scope picture., Ser. I, Part I, Shot 7

43

CA/M(:/734~

4'44

' ',

( j

!! . ..

G4UQa, 3 0 4 moc/m

100 ps1itom

Pro~ectile velocity-

""Scop} pictwre$ Seie T r h

'45

ift m

Shot 11

"I' ' .. 2 100.p*1/rn

i

Stg~, 3Ge & 4, 0.6 insOC/em

• -;•;. : . .. . 1'00 Ps$1,cm-...

, ) Projectile velocity.

1. 2928 fps

Figure 22

Scope picture, Series 1, Part 1, Shot 11

S•46

iWII.-. .. .. . • . , -.,*~4 '..i. t* W- n - u,, ,..u._

p (W~-u,*

' ~~100 1/v

Aloet II eld

U04

Figure.in~pyc

Scope picture, Sor i e I, Part 1I Sho't 12

_ --H ....... 4>:~ -" S-h•• " • ...- t.. .1. ..3

I'.• .'

S. • 4 • II' . .'. ' ' ., ,• "'. ...

S"• " "! " " ' • . • " •W"te"r

• I"' " ' • '.!"I ' '

• i!lO psi/cm

i".

\| "" I

' ° ~ ~Projoctlell veloclty-...,

S3091 fps

Scop pitureSeigues 1, P'rt "!'Shot '

II))" A c p lue Sre ,-,Pr ,So 3•, ..

"-• . ' ,. . ' ntt ' ' .. 1m " . ' . " ",..,--..:A ,

GA/MC./ 3-3

~ ~~'I.Shot 14

t Water

.,.Ga~ges 1&2, 2 msec/cm:200 psi/cm

Gages 3 & 4, 0.5 rnsec/cm

200 psi/cm

I ~Gages 5 & 6, 0.5 rnsec/cni200 psi/cm

Proje~ctile velocity-

2770 fps

Fi(jurce 25

&ope pjctureý Serif& 1, P.3rL 2, Shot 14

4~9

GA/MC`/`73-43

Shot 15

.Water.

Gages,1 2, 5 mnsec/cm200 psi/cm

Gages 3 & 4, 0.5 msec/cm

200 psi/cm

Gages 5 & 6, 0.5 msec/cm

200 psi/cm

Projectile velocity-

2691 fps

Firjure 26

sr-pep ctre) er'e 1 P~r 1, 5 o0 1

GA/MC/73,-3

~.z,7.i.Shot 16

. water

. Gages 1 &2, 2 msec/crn

[ LP . .200 psi/cm

1 40

- 200 psi/cm

Gages 3 &6, 0.5 msec/cm

15

GA/MO/fl 5 3 .W ~ ~ ~ ~ ~ -

J7 Shot TA'

SGages 1 &24, 0. msec/cm100 psi/cm

[ -,:~'.vj¾ L,:. ~Gages 3 & 4 0.5 msdc/crn

Frjcie eoiy"260fp

fiur 28UppitueSrasZPat1ShtI

GA/.MC/`73-.3

I*... .Shot .2

"I Pxr,,eumacel

Gages 1 &42, 2 msec/cm .100 psi/cm

*Gages 3 -& 4, 0.5 msec/cm

1 .100 psi/cm

' I'. . .. .

* Gages 5"& 6, 0.5 msec/cm

S! 100 psI/cm

Projectile velocity-

S 4 2750 fps

SFigure 29

Scope picture, Series 2, Part 1, Shot 2A

53

-GA/MC/73-3

Shot 3A

Pneumacel

.Gages I & 2,.2 msec/cm:

Hi .... ... 100 psi/cm..................................................-. ,,.. ..

SI ,

"Gages 5 & 4, 0.5 msec/cm

100 psi/cm

I..54

I Gages 5 & 6, 0.5 inset/cm

11111lO ps0t/cm:M100 psI/cm

ProJectil e veloci ty-" i 2150 fps

' '4

- . t . * . . ' .. I. , .s .- .. . .

* .. •... ... ,..'- • ' I t. : .

"GA/MC/73-3

Shot 4A

Pneumacel

Gages I & 2, 2.msec/cm

.100 psi/cm

IC.V

Gages 3 & 4, 0.5 rnsec/cm100 psi/cm

Gages 5 & 6, 0.5 msec/cm

100 psi/cm

Projectile velocity-2750 fps

Figure 31

Scope picture, Series 2, Part 1, Shot 4A

55

GA/NC/73-3

[(1 .. Shot 5A

Pneumace1

Gages 1 & 2, 2 msec/cm

S. .. 100 psi/cm

Gages 3 & 4, 0.5 rnsec/cm

100 psi/cm

r. i - - -

Gages 5 & 6, 0.5 msec/cm

, 100 psI/cmII

Projectile velocity-

2830 fps

Figure 32

Scope picture, Series 2, Part 1, Shot 5A

56

GA/l-1C/73-.3

(. Shot 6APneuniacelj

Gages 1.& 2, 2 msec/lcm200 psi/cm

Gage 3, 0.5 insec/cm400 psi/cm

Gage 4, 0.5 msec/cm

200 psi/cm

1~:ziz :z71:z:I:zz:n~z7 c(qe 5, 0.5 scm

400 psi/cm

Projectile velocity-

2680 fps

Figure 33

Scope pictur-e, Series 2, Part 2, Shot 6A

57

J.I tA

GAMC/ 733

Shot, /A

200 psi/Gill

Ni P. 3, 1

I400 POhil

.0.

4.0

'Ipsij ý

'S op 1.ct 26t 7A '

rc ' ie Ie

ItI

v low/ C to

~ 99

im- il i

200 pli/cIll

400 psi/cm

6Ii j 40 0,5 ii ,c cj~'M0 psi/cm

I'~' *~' ~ ' ~ .NO psi/cml

hi Gae 6, 0,65 msec/col

26i38 fps

S I

S(io9•3 & 4, NO DATA

?:1k

Gago 5, 0.6 11SK./c11

200 psi/cm

6 1 ..} (iGage.6) 0.5 ms~c/lni

400 psi/cmK j . , ProjecLile velocity-

w 2688 fps

Scope pictura, Ser I ts 2 Pa r L, Shot IOA.! .'-'.... ~," ., . ,' '.. .. ' - '. ....

V4t t ilot .. %1%

*1P4 a1I4Io titditti St.w Pvtor biirpo Vt, Ila. re-

.Florld# in t1967 11c enturtd. tho Air Poreq in Niovornho 1067 And ra-

Calif, ftomn 1961-0. Ili JtJmfl 1971 Ito oii ia the (Thidunto Astm~iakticalWilinoring pr~upr tit tho Air ForcoI'ttt ~Tc~~~ toolv of

lPcritzent Addriess:

7I25 hfinwmod Aven~ue N.

* 62