Saturn IB-Saturn v Instrument Unit Technical Facts

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furth er information contact:Cape Kennew: J, F. Harroun

305-784-9 783

In Houston: A . S . Cella713-NU 8-3300, ext. 371In Washington (Bethesda):E. B, Evans

SATURN IB - SATURN V INSTRUMEN

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IIThe Saturn family has sys tem litarg rocket pro-

gram s, such a s Redstone, Thor, Jupiial guidance platform can be traced from4theearlier Pershing,tone vehicles; the telemetry system evolved from a design first, and a portion of the t racking equipment was developed initially forgram. Adding the human element required new syste ms for longer

and more varied missibns and anvovei

Although the Saturn I ser ies ofi

there ar e onlyia few identical compo!Each of the labt five Saturn I vehicP

computer sim ila r to those in th


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Saturn IB

a completely new design incorporSaturn IF3 missions. The d e s i g nremain nearly identical for hot11 programs after velopment test s a r ecompleted.

The IU was designed and developed by NASA's George C. Marsh all SpaceFlight Center (MSFC). In the Saturn IB program, IU responsibility is being trans-fe rr ed gradually to IBMrs Feder al Sys ivision with ove ral l responsibilitybeginning with the fifth flight IU. Work on the fi rs t ight models is the responsi-bility of MSFC, with the actua l assembly being done in IBM1s Huntsville, Alabama,facility. Testing is performed by IBM personnel,

IBM ' s contr act calls for fabrication and assembly, complete system testing,and integration and checkout of the IU with the launch vehicle at the Kennedy SpaceCenter.

cluded in the contract a re req uirements for the computer program smissio n conditions and predicting vehicle perfo rmance, operating

automated checkout equipment on the ground, and for reducing and analyzing environ-ment and performance data during and after the flight.

SATURN IBI VEHICLE - OVERALL Vf

Thelrange of capabilities and missio ns planned fo r the Saturn IB launch14vehicle is *fleeted in the design of the navigation s ys tem s. This flexibility to me etIi1new missiop assignments requires a gene ral purpose launch vehicle digital computer


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Saturn IB - Saturn V Instrument Unit Technical Facts Page 3

(LVDC), which generates stee rin g signals under ~otr t r n internally-stored+program. Different missions can be controlled by different LVDC programs. The

vehicle engine actuators ar e controlled by a separa te flight control computer system ,including an analog computer, rate g yros, and control acc eler ome ters .

Fo r attitude control, the cu rr en t attitude of the vehicle is compared with thede sir ed attitude, which is stor ed in the LVDC's prog ram . Attitude correctionsigna ls, o r ste erin g commands, a r e the difference between the existing attitude a n dthe desired attitude.

These s teering commands ar e combined with signal control senso rsin the flight control computer system to generate the control command for the engineactuators. Gimballing the engines changes the d irection of the vehicle. During theS-IB burn , pitch and yaw control acceler omete rs provide late ral acceleration datato the flight control computer s o that stabl e flight is assured.

In guidance and control ter ms , each Saturn IB vehicle is a s epa rat e entity.Long bef ore each flight, NASA plans the missi on. Fro m this mission definition, IBM

op the mathem atical equations to be us ed by the guidance com puter and\ IBM converts thes e equations into computer pro gram s.

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Using a cbmputer complex installed a t the D M untsville, the mi s -ision is simuldted to check out the progr ams and verify that, for any foreseeable s et ofE

conditions, t* LVDC will continuously determ ine vehiole sta tus and determi ne thei

L optimum path t o its destination.


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STAGE DESCRIPTION:*kr "The IU consists of six major subsystems: struct ure, environmental control,

guidance, flight contr ol, instrumentation, and elec tricMounted on the struct~1r:ll ing inner sur fac e is the ele ctron ic equipment used

to navigate the vehicle, Inexsure environmen t and perfo rmance, and comnlunicatethese data to the ground. Supporting this equipment is an environmental controlsy st em for heat dissipation, a supply of nitrogen gas for the guidance pla tfo rm' sgas bearings, and an electrical system.

STRUCTURE:The structure section is 2 1 . 7 feet in diame ter and thr ee feet high. Assembled

vehicle, it becomes a load-bearing part which supports both the compo-nents within the IU and the weight of the spacecraft.

It is manufactured in three 120-degree segments of thin-wall aluminum alloyded over a c or e of aluminum honeyco inch thick o r a s thick. An aluminum alloy channel ring, e top and bottom edge

I of each segment, provides the sur face for mating the IU, the S-IVB stage, and thekets on the insid the

e environmental nts not requiring


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The segments ar e a l ignc r l ;rnd joinner and outer surf ace of c :~ch oint.

A spring-loaded umhilicnl door in the st ruc tur e provides a mea ns f or serv iceconnections between the IU a n d ground support equipment. A la rg er ac ce ss door. boltedin place, permits pc rs nn ~~ clo cntcr the IU following its mating to the launch vehicle

Despite its s iz e anti the st re ss es that must be withstood during launch, the/ complete str uc tu re, pr ln r to eqolpment installation, weighs a little over 500 pounds.

ENVIRONMENTAL CONTROL:The cold plates of the enviro nmental control sys tem provide a m eans of

mounting and cooling the complex electro nic componentsstage, both on the launcl~ing ad and during flight.

eri ods of operation in a typical Saturn IB missi on, coupled withYI

ace , req uir e special provisions for heat tran sfe r and dissipation.\!A c $ 4 ~s (1 6 in each stage) abso rb heal from the electronic components.d The heat i s conducted through the smooth sur fac e of the cold plates to a coolant mix-aI tu re much like antifreeze---GO?: methanol, 40's water , Cooling is a function of the

+d . 'contact ar ea Between the component and the cold pla te. Since the I,VDC, the launchvehicle data ddapter (LVDA) flight contr ol computer, and the ST-124M inertialguidance pla tfo rm generate the mo st heat, the coolant actually pa ss es through these

ii components ibstead of ex trac ting the heat via conduction.


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Saturn IB - Saturn V Instrument Unit Technical Facts Page G/f -~LJI ; I?A w;bj&hii&

/ In the vacuum of s pa ce, the war med coolant, af ter leaving-the cold pla tes,"*. - *% ii1 is routed through a device called a sublimatbr. Water, from a res er vo ir in the IUii( is supplied to the sublinlator where i t i s exposed through a porous plate to the low

tem per atu re and pr es su re of outer space. The water freez es, blocking the pore s inthe plate. The heat from the coolant, tra nsf err ed to the plate, is abso rbed by the ice,

\converting it dir ectly into water vapor (a proc ess called sublimation).

This system is self-regulating: A sen sor constantly monitors the temperatu re.If the coolant requ ires chilling, this s ens or controls a valve which div erts varying

through the sublirnator/heat exchanger. If no cooling is required

e environmental control system provides a supply of

/ pressurized gaseous nitrogen to one side of the diaphragm in the coolant and water9 es er vo ir s, sin ce in the weightless perio d of flight, without som e form of artif icia lpr es su re , these liquids would dispe rse into droplets. Gaseous nitrogen also is pro -

bearings of the ST-124M platform. A pump to ci rcu late the coolant,ry valves and tubing to control its flow, complete the equipment of the

environmental control sy s em .

GUIDANCE AgD FLIGHT CONTROLIJThe IU'$ guidance and flight control sy ste ms con trol the flight of the Saturn IBito meet missi$n require ments . Completely self-contained, these system s mea sur egacc eler atio n apd vehicle attitude, deter mine velocity and position and the ir e ffe ct on


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the mission, calculate and issue control commands to ine actuators to place thevehicle in a desi red position. The major yste m are: an inertialplatform, n digita l guidance computer , an analog flight Zontrol computer, a dataadapter, control rat e gyros and control acceleromete rs,

Pr io r to liftoff, ia~aneh aram ete rs a r e fed into the LVDC. About five sec on dsbefore liftoff, the inert ial guadance platform and the LVDC a r e released f ro m groundcontrol. Previously aligned to the launch azimuth, the guidance platform senses andnieasures the vehicle's acceleration and attitude as the vehicle ascends into theatmosphere, and i t sends these: measurements to the LVDC via its interface, the

The LVDG integrates these rr~easurementswith t nce launch to determineelative to st art ing point and destin

de correction signals in order fovelocity and altitude for its mission.

'Shese attitude corr ect ion signals, ra te gyro outputs, and control acce leromet er out-puts a r e sen t to the analog flight control computer. Based on the data received fro m

e gyros and accelerometers, the flight control computer issues theactual control conn~~~~rnds.

Each mission ha s at le as t thick phases: atmospheric powered flight; boost periodafter initial ehtry into space, and the coasting period.

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vehicle a re grea tes t during atmospheric boost because of the impactr e on the vehicle1s sur face s, During this portion of the flight,

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Saturn LB - Saturn V Instrument Unit 8the guidance and flight control system s a r e concerned primar ily with vehicle integrity,and so it is programmed to sust ain an attitude to minimize vehicle loading.

After f i r st stage separation the prograiixs ara'd&sf.gned to optimize the path the"4, *

vehicle takes to achieve the desired mission.During this phase of powered flight, guidance is accomplished by a s er ie s of

repe tit ive computations. Approximately once every two seconds during flight, theguidance computer dete rmines vehicle position, vehicle conditions required at the endof powered flight (velocity, attitude, etc.), and gene rates the attitude cor rect ion signalsnecessary to accomplisli the desi red end result . This is known amode, o r "closed loop guidance. "

Twenty-five times a second, attitude correction signals a r e generated by the mostrec ent solution of the guidance problem. The LVDC , hrough the LVDA, sends thesesignals to the flight control computer where control commands ar e generated to st ee rthe vehicle along the desi red flight path.

To ens ure reliability, crit ical circuit s in the LVDC and LVDA a re provided intripl icate. Each of 3 identical circ uits produces an output which is then "vatedl'upon. In cade of an er ro r in these outputs, the majority rul es so that a randomfailure is iguored. In addition, the computer memory is duplexed, so that i f an err oris found in one port ion of the memory, the output is obtained from the other memory,

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and then the ,cor rect information read back into both memories to cor rec t the er ro r.6

01 To ensurd the accuracy of the position data originating in the inert ial equipment,I

glts bearing4 a r e provided for the gyros and pendulums of the ST-124M ine rt ia l

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Saturn IB - Saturn V Instrument Unit Page 9

guidance platform t o redu ce friction in these-components to a minimum. The beari ngsI e 'r"' * i

are 'Yloatedflon a thin film of dry, pressurized nitrogenxsupplied at a controlled pres -su re , tem peratu re, and flow rate from reserv oir s in the IU.

In addition to the guidance computations, other functions a r e performed by theLVDC, an d it s input/output device, the LVDA. During pre-la unch , they conduct te stpr og ra ms ; during launch phase they dire ct the sequencing of events via the IBM-developed switch s ele cto r (one in each stage ), such a s engine ignition and cut-off,stage se parati ons, and check to se e that the vehicle is performing normally. Duringea rth orbit , they determine attitude control, conduct tes ts, and control the transmis-sion of data.

INSTRUMENTATION:P 1 Measuring se ns or s, o r transduce rs, a re located throughout the vehicle to

0 onitor the vehicle environment and sy st em st performance. Approximately 300 suchi easurements a r e made by various sen sor s, Acoustic transducers monitor soundlevels, res ist or o r therm istor transducers monitor temperature environments;\ pre ss ure s ar e measured by Bourdon-tube o r bellows transducers; force-balance,o r piezoelectric accelgrometers me asure force levels a t critical points, and flow

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me te rs de termine r at es of liquid flow.I

iSignal c$nditioning modules modify the se v ariou s tr ans duc er outputs to af voltage. The different types of data requir e different mode s of


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Saturn PB - Saturn V Instrument Unit

transmis sion, and the telemetry porti bandfrequency modulation, frequency -modulated frequency fio8ulation and pulse-code-modulated frequency modulation.

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Each type of information is routed t o the app ropriate tele metr y equipment bythe measuri ng distrib utor s. For maximum utilization of the tran smi ssio n equipment,multiplexing is employed on most telemetry channels. Measurements from differentse nso rs a re transmitted to eart h. The information transmitted over any channel is ase ri es of meas urements made at different points within the vehicle, so that a la rgeamount of data can be s en t with a minimum of co mmu ni~ ati on quipment.

To furth er inc rea se the amount of data which can be handled, the LVDC-.

sequences the transmis sion of certain measurem ents. For instance, during ret ro-frocket firing, when flame interfer es with telemetry +ransmissions, signals a re auto-

matically recorded on tape and transmitted late r.

eking sys tem s a r e used to determine vehicle position and the datato provide traj ecto ry information. Transpon ders in the IU increase

curacy of the ground-based tracking syst em s, Puls es of radio-transmitted by the ground stations interroga te the vehicle in flight.

I .The airborne1 ransponder answ ers with a pulse, o r ser i es of pulses, frequency-or-time-displackd fro m the incoming pulse to minimize interference. The ground station


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Saturn IB - aturn V Instrument Unit Technical Facts Page 11-vOne C-band transponder is used to t~ i' ck ing ndependent of vehicle

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attitu de along with a sing le AZUSA transp onder. The C -b ad tracking system pro-vides orbi tal tracking data for both real time and post flight trajec tory ana lysis. TheAZUSA sys tem provides re al time tracking data for range safety impact predictions,and for post-flight trajectory analysis.

A radio command link is used to communica te with the LVDC from theground. Examples of mes sag es include: updating data from the LVDC; commands

to per for m the updating, commands to per form tes ts, special subroutines; a com-mand to telemeter certain sectors of the computer memory; and a command to relayto the ground a partic ular add res s in the computer memo ry. Message s can be addedo r deleted as necessary.

ELECTRICAL:Ele ctr ica l power during pre-launch is furnished from ground so urc es through

) the IU umbi lical connection. At approximately 20 to 30 seconds pr io r to lift-off, a/ signa l from the Launch Control Ce nter tran sf ers power to four 28-volt alkaline silve r-t zinc batteri es in the IU. Each batte ry has a capacity of 350 ampere hour s. IU power

1 < < . eis designed for F. 8 hours of mission life. Loads a r e partially distributed ove r thefour batteries 4 qualize the battery drain, and to provide a redundant power sour ce

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Fto the componerits in the event of bat tery fai lur e.iTwo specla1 power supplies ar e provided: The 5-volt ma st er m easu ringI

Svoltage supply cionverts the 28 Vdc main supply to a highly-regulated 5 volts dc to be

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used a s a r efer ence and supply voltage for t ponents of the mea sur ing sy st em ;the 56-volt power supply provi des the regu lated 56-volt dc requi red f or operation ofthe guidance and control s ys te m' s ST-124M iner tial guidance plat form.

The switch selec tor s in each vehicle st age provide a me ans of controllingthe sequencing of events taking place in that sta ge. Each sele ctor can issue up to112 different 28 volt commands to the various elec trica l circui ts in the Saturn. Theguidance system's LVDC and 1,VDA control these , selecting the appropriate circ uitsa s the miss ion progr esses .

The emergency detection equipment monitors thrus t f or both powered s tage s,guidance computer status, angular attack rates, attitude error, and angfe of attack.It dete cts abnor mal conditions affecting the safety of the cre w. Where tim e i sinsufficient for the crew to re act , the automatic abort will be used. If the crew canre ac t, the eme rgency detection system will provide an indication, "manual abort, lwhich the crew ca n use i f deemed nec essary.

ASSEMBLY OPERATIONS:Assembly of an IU4 begins with the arri val of thr ee curved stru ctu ral segments

aa t IBM's Huntsville, Alabama, facility.

iThe three: segments---each weighing approximately 175 pounds---are placed on1a cir cul ar assembly fixture and arranged f or alignment and splicing. Following this,

prote ctiv e rin g8 a r e bolted to the top and bottom of the assemb ly to stiffen the struc-tu re s o that i t can be moved about without disturbing the alignment. Holes ar e cutthrough the st ruc tur e to mount vehicle antennas.


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Saturn IB - aturn V Instrument Unit Technical Facts Page 13

Transducers to mensure temperatu d thi rm al conditioning panels a r emounted to the IU's inner skin, and a frame-like, cablc tray to ca rr y the electricalcables is installed around thc top of the structure. Components a r e mounted on thether ma l conditioning p:tnels. and the thermal conditionil~p, ys tem 's pumps , accumu-

( la tors (stor age tanks). heat exchangers, and plumbing a r e installed. A gaseous/i nitrogen supply systcxm for the ga s bearin gs of the iner tial guidance platform is

attached. Finally, ducts , tubing, and elec tric al cables complete the assembly of theIU. The assembled TCi wcighs approximately 4000 pounds.


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Saturn IB - Saturn V Instrument Unit Technical Facts Page 1.1ag ";computer con t s the te st in riccordance with 3 tes t firocedure provided on a magnetic

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nd test resul ts a r e displayed on thc operator's console and recordedon magnetic tape o r on -line pri nters . Pre-launch , launch 2nd flight opera tion s a r etested, using computer s iinul;~te d nputs to represc:it sihq als which a r e pres ent duringflight.

Electro-m agnetic compatibility (EMC) te st s arc3conducted upon completion ofsystems checkout.

After EMC tests are completed, the water and waterimethanol coolant solu-nmental control system is drai~ied, nd the gaseous nitrogen is

a i r benrln g sup111~'. Cert ain equipinent (the ST-124M iner tialthe LVDC :tnd the LVDA) is removed and packaged separ atel y for

unch si te . The asse mble d IU , with oth er components attached. i sping c ar ri er . Accelerome ters ar e mounted at sensitive points withine s tr es se s experienced during shipment. The unit is flown to the

VEHICLE INTEGRATIQN A T CAPE KENNEDY:I

Upon ar ri va l a t the Kennedy Space Center , the IU is checked to verify that1no damage ha4 occ urr ed during shipment. Mechanical alignment of the IU and plat-Itform mountin4 surfac es i s verified in the receiving ar ea .i1i


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Saturn IB - aturn V Lnst i -unl rXntUnit Technical Facts Page 15

S-IB LAUNCH COMI ' I iEXThe IU is moved to t h ~:111nchad and raised to its position on the forward

sk ir t of the S-IVB and fastct,,, ~n to lace. Components removed before shipment arereinstalled at this time. \ L , i ~ , . r and water/metl~anola r e supplied to the environmentalcontrol system from s t B t , v i c c b clu~pment n the l:~unch ower, and gaseous nitrogen issupplied to the high p~ ,c ss ur c torage spheres of the ai r bearing supply. At this tune,the IU syst ems a r e function:~lly-tested o verify operational status. Test s include"flight readiness, " "plug-in" (uml)ilicals connected), "plug-drop" (umbi1ic:ll droppedduring test to verify satisfa ctory t ran sfe r from ground to vehicle power), and, finally"countdown demonstration" (dress-rehearsal of terminal countdown terminated insimulated abo rt just pr io r to lift-off).

As the termina l launch countdown ne ar s T-10 hours, the pre-launch te stbat ter ies a r e removed, and the flight batt eries installed and connected. The serviceplatf orms and components1 handling equipment ar e removed f rom the inte rior of theIU, nd, aft er a final check to ensur e that the are a is clear, the access door is boltedin place and the IU service a rm is retracted into the gantry.

i ] As the launch countdown pr ogre sses , a beam of light from a precisely-located, [ theodolite hut on the ground pa ss es through a sma ll hole in the IU and into a windowI{

in the guidancejplatform. The light beam is reflected back to the theodolite fr om arpair of platform prism s. Each pri sm reflects a different portion of the frequency

tspec trum , andft his "color code1' is used to align the platform to its launch azimuth


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p ri o r to the flight. An acquisition light go cen ter when the$2

platform i s prop erly aligned. Computer-derived launch azimuth signals a r e thenused to r elin e the position of the platform with res pec t to a fixed ground referenoe.

With the launch azimuth est ablish ed, and the required mission parameter ssto red in the LVDC memory, th e IU is ready for flight.

Saturn IB-Saturn v Instrument Unit Technical Facts

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