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CEC

suT I1 spacecraft structure s are simple, rugged, low-cost st

can be easily changed to adapt to new components. They were designewas not a problem.

ration tested over a very sh ort time span with minimal stress analysis sine0th are constructed from riveted aluminum and ma

semimonocoque- type stru ctur es. Simple, low- cost, easfistruct ures may be used more of

fut ure when lower launch cost vehicles comeinto full use . The design eoion, fabri cation and handling, and shock and vibration testing of

res such as the SERT

tures are the subje ct of this repbrt.

ion is the second Space Ele ctr ic Rocket Test.

ective w a s to endurance test a mercury boital test which demonstrated the ability of ion thrus

rat ion of the SERT I1 satellite is shown in figureend facing the ea rth and th e Agena rocket - sol ar a rr ay end away from tGravity-gradient stabilization is achieved by locating all the heavy mass esthe satellite. The satellite was launched into a 1000-kilometer (cir cul ar orbit. The orbit was calculated s o that t he or bi t plane of nodes woat a rate approximately equal to the earths motion around the sun. Thus, tarra ys will face the sun for almost the entir e mission. (The SEscrib ed in detail in ref. 1.)

tage with the spacecraft-spacecraft suppor

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Spacecraft- _

_,--Cei~ter of mass

Station6.2 Bm(245.00 in.)0.5334 m(21.51 in . ) 8

A +0.5334 m I. 575 cm(21.0 i n . ) i n . ) 5.1 4045 m(202.38 in.)Ion thruster-- I \..--Thrust vectorEarth CD-10991-32

Figure 1. - SERT I1 satellite.

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eture w a s re

3

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1.4859 m d i a m(58.5 in. 1 m

C o n t a m i n a t i o n '+) , - I o n t h r u s t e r90 " Ie x p e r i m e n t -

\,(

Space

-O D (-Z)

CD-10992-32( -Y)Figure 2 . - Top view of spacecraft .

,Gas-supply lateral-(+y) 00 //' s u p p o r t s t r u tI /

,-Gas supply/'Gas-supp ly -s ide l oad-

r C o m p o n e n t// s u p p o r t t r a y

S u n s id e0" (-Z)

270"(-Y)

CD 10993-32

t i g u r e 5 . - b p a c e c r a n ro p w a y .

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270"( -Y)

Figure 4. - Spacecraft bottom tr ay.

CD-10994-32

ures were no

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(tZ)80"- -0" (-Z)

270"(-Y) C 0-10995-32

Figu re 5. - Spacecraft support unit top tray.

1.4986 m dia m(59.0 in.)

(tZ)80"-

I270"(-Y)

(y) ,,-Damping strut90"

.O" (-Z)

CD-10996-32

Figure 6. - Spacecraft support unit bottom tray .

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T A B L E I. - STANDARD AGENA CLAMSHELLSHROUD DYNAMIC E N V E L O P E

V e h i c l e s t a t i o n D y n a m i c e n v el o pe d i a m e t e rZ - Z axis R e m a i n d e r of

c i r c u m f e r e n c em i n . m

she spacecraft was desi

tion of 7 . 5 g ' s , combined wi m acceleration of 4.8 g 's .

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T A B L E 11. - A S S U M E D S P A C E C R A F T D E S I G N MASSESS t e m

T h r u s t e r s y s t e m 1T h r u s t e r s y s t e m 2Backup a t t i tude cont r o lP o w e r c o n d it i o ne r 1P o w e r c o n d i ti o n e r 2T r a y

s y s t e m

S t r u c t u r e

26

: en te r4411887735-----

Loca t ion of c e n t e r of m a s sS ta t ion

T o t a l d e s i g n l o ad

in20200

262620

D e s i g nload

34.0234.024 6 . 2 7

8.168.16

2 0 . 8 720.87

7.26

6 7 . 5 9283. 5

l b7575

1021 8184616

14952 5

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s

res were

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stiffeners as in

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(a ) Bottom view.

(b) Ba y 8 side.F i g u r e 7. - S p a c e cr a ft s t r u c t u r e .

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1

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P

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to the spac ecraft in bays 2 and 6 (see figs. 2 , 3, anU) are mounted to the bay 4 thermal radi ator plat

spacecraft lower ring (see figs. 3 and 10) tank and valve and regulator as se m

y of the spacecraft. The two nozzle assemblies are rnouface at bays 4 and 8. The tank and the valve and re

ruster dynamic loa s to the Y-Y axis cross

, Exterior machined magnesium channel

Figure 10. - Spacecraft and spacecraft support unit mounting.

rac ket s which attach to the cr os s beams of t he spacecra ft. Triey int erfere nce) antenna and contamination exper iment s are mo

earn and outer ring on the fa ce of th e spacecraf t. All otheretron ics boxes are mounted to the upper and lower bay 8 i n s t ~ ~ e n t

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is mounted in bays 2 , 4 , 6 , and 8 o r thethe odd-numbered bays 1, 3, 5, and 7.d on figures 5 and 6 . A l l electronic and electrical bIs)are mounte

gururation of tfor any instrument tra y. The battery sel ect e

s there fore located on the sun side of torced, bay 8 back cross-beam w al l .

e lower bay 2 instrument tra y reexceed the ra the r low tape r ec order qualif

e recorders, the lowere coupling w a s accomplished by tying turmounted with a Lorddy system has a lower

anufacturing eovibration enviro

ration environment qualificationcification requirements.

necess ary to vibration isolat 's in orde r to meetby bolting the gyros to a box beam assem bly and

_ _ -CMG trunion

+ t i T + +

,r Spacecraft su p p r tunit structural we b

CD-10997-32Figure 11 -Control moment gyro (CMG) cross-beam assembly.

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1

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T A B L E III. - Q U A L I F I C A T I O N TESTS(a)S i n u s o i d a l s w e e p f r e q u e n c y q u a l i fi c a t i o n t e s t a

A c c e l e r a t i o n S w e e pr a t e ,

o c t a v e s / m i n2 . 02 . 01.02 . 02 . 02 .02 .0

b(b ) R a n d o m n o i s e v i b r a t i o n q u a l i f i c a ti o n testF r e q u e n c y ra n g e , A c c e l e r a t i o n l e v e l , S p e c t r a l d e n s i t y ,

H Z g's r m s g 2 / H z

a s w e e p t i m e f o r 5 t o 2000 HZ, 4 . 3 m i n .bAlong each of t h e X , Y , an d Z axes; d u r a t i o n , 4 . 5 m i n / a x e s ;o v e r a l l l e v e l , 1 0 . 2 g ' s r m s .

C L Sof s pacecr aft str uc tu ra l design is in reality the roblem of packaging

riments s o that they will survive the launch vironment to fu nc ti o ~m. This is the philosophy used in evolving the SE

acecraft w a s designed within the weight, si ze , t hermal , and economicions set forth at the program outset. This can be done fo r any S/C stblem is considered as a systemcraft experiments and systems.

blem involving mechanical in-ring initial design

ication complexities versus the possible benefits of a minimum-weighte considered in view of t he proposed launch vehic

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a minimum-weigpayload us ing the ps than the cost fo r orbiting the sa me stur e strong but serials. A reasonable safety f actor CQal materials crime launch vehicle, such as a rockepermit another experiment to

(3) If a mo re expensive rocket would be required w er e the s p(4 ) If a less costly vehic le could be used i f the struct ural wei

trimmedacecraft is proposed, all sys tem s should come under t

tiny as proposed in the preceding paragraph. F o r instance,control, heat pipes should not be used i f solid conduction can be found to

at an acceptable w e i incre ase. Electronics should by heavy but simuble and tr ip le redundancy should be practiced in cr it ic

inexpensive to fab ricat e i f the weiproblem. The purpose of these st ep s is not to produ

space craft but to us e weight margins s o as to i ncrease spacecraft ren the S spacecraft was first proposed, many of these ideas

y on a payload-to-orbit basis but mainly as a ready package that coulracti ce. This was desir able and possible because the launch vehiperform t he SE T I1 mission. The second st ag e with its so la r a r rays atlaunched successfully on Febr ua ry 2, 1970. Indications are thatthe launch environment undamaged. hus, the choiceof general

was to become a large pa rt of th e orbiting vehicle. The SE

s , and construction techniques was validated fo r the SERT I1 structures.esearch Center,

Cleveland, Ohio, March 5, 1971,National Aeronautics and Space Administration,

704- 13.

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6. ; Gursk, Guy S. ;acecraft and Mission. NASA

sion Capabili

nvironmental Test Specification fo r Spacecraf t and Componentsictat ed by Atlas-Agena, Thor-Agena, o r

or-Agena Vehicles. Specification S- 320-A- 1, NASA God

.: Analysis and Design of Flight Vehicle Struct ures. Tri-State

NASA-Langley, 1971- 2 E-6 175

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