The SCOTS attitude control system

Abstract

RCA As tro-Electronics d i v i s i o n r P r i n c e t o n , N . J . 08563-0800The RCA S h u t t l e Subsystem (SCOTS), a upper s t a g e , i n j e c t s ronous t r a n s f e r o r bCompatible O r b i t T r a n s f e r s o l i d -p r o p e l l a n t s p i n n i n g s a t e l l i t e s i n t o geosynchi t .The SCOTS minimizes weight and launch c o s t s by u s i n g a s i m p l i f i e d deplovment mechanism t h a t e j e c t s t h e SCOTS1 s p a c e c r a f t assembly from t h e S h u t t l e ' s payload bay w i t h o u t s p i n .The c o n t r o l system s p i n s up t h e assembly a f t e r deployment.Weight and c o s t a r e f u r t h e r reduced by u s i n g t h e s p a c e c r a f t ' s a t t i t u d e c o n t r o l subsystem t o c o n t r o l t h e SCOTS. The SCOTS a t t i t u d e c o n t r o l system u s e s a n i n e rt i a l r e f e r e n c e t h a t i s i n i t i a l i z e d w h i l e t h e SCOTS i s s t i l l i n t h e payload bay and u s e s a unique t e c h n i q u e t o s i m u l t a n e o u s l y c o n t r o l p r ec e s s i o n and damp n u t a t i o n . I n t r o d u c t i o n F i g u r e 1 i s a n a r t i s t ' s r e n d e r i n g o f t h e S h u t t l e Compatible O r b i t T r a n s f e r Subsystem (SCOTS). The SCOTS minimizes weight and launch c o s t s by u s i n g a s i m p l i f i e d deployment mechanism t o e j e c t t h e ~~0~~1 s p a c e c r a f t assemblv from t h e Space S h u t t l e ' s payload bay w i t h o u t s p i n . The SCOTS C o n t r o l System F u n c t i o n s Because t h e SCOTS a t t i t u d e c o n t r o l system r e s i d e s i n t h e s p a c e c r a f t and n o t i n t h e upper s t a g e , t h e SCOTS i t s e l f can b e c o n s i d e r e d a dumb s t a g e . The SCOTS a t t i t u d e c o n t r o l system h a s t h e f o l l o w i n g f u n c t i o n s : 1. C a l i b r a t e s t h e g y r o b i a s e s w h i l e t h e SCOTS/ s p a c e c r a f t assembly i s i n t h e S h u t t l e ' s payload bay 2 . A f t e r c a l i b r a t i o n and b e f o r e deployment from t h e payload bay, i n i t i a l i z e s a r e f e r e n c e q u a te r n i o n w h i l e t h e S h u t t l e p o i n t s t h e SCOTSIspacec r a f t assembly i n t h e c o r r e c t f i r i n g a t t i t u d e f o r t h e upper s t a g e 3. P r o p a g a t e s t h e i n e r t i a l r e f e r e n c e frame i n body c o o r d i n a t e s u s i n g a gyro-based a u a t e r n i o n u p d a t e a l g o r i t h m L 6 . A f t e r deployment. w i t h ' e s s e n t i a l l y z e r o momentum and o n c e t h e SCOTSIspacecraf t assembl v i s a s a f e d i s t a n c e from t h e S h u t t l e , s p i n s up t h e assembly t o 8 d e g r e e s l s e c f o r g y r o s c o p i c s t i f f n e s s d u r i n g t h e subsequent a t t i t u d e manassembly s p i n s up a f t e r deployment. Weight and e u v e r s c o s t a r e f u r t h e r reduced by u s i n g t h e spacec r a f t ' s g y r o s , t h r u s t e r s , and computer o r micro-5. R e t u r n s t h e assembly t o i t s f i r i n g a t t i t u d e p r o c e s s o ...