Reliability Concepts in Rocket Power Controls Design

T h e p r inc ipa l power con t ro l p r o b l e m s in a l iqu id p rope l l a n t rocke t a re p r o p e l l a n t i gn i t i on , r egu l a t i on d u r i n g t h e t h r u s t increase t o r a t e d t h r u s t , m a l f u n c t i o n de t ec t i on d u r ing t h e s t a r t i n g t r a n s i e n t , t h r u s t con t ro l (if r equ i r ed ) , a n d m i x t u r e r a t io or p r o p e l l a n t u t i l i z a t i o n con t ro l . T h e d e sign of a rocke t power con t ro l s y s t e m m u s t be cons idered a n insepa rab le p a r t of t h e genera l eng ine s y s t e m design if a n o p t i m u m con t ro l sys t em is t o r e su l t . M a x i m u m eng ine rel iabi l i ty can be achieved only by a con t ro l sy s t em hav ing func t i ona l s impl ic i ty as a r e su l t of rea l c o m p a t i bi l i ty of t h e ma jo r eng ine c o m p o n e n t s a n d t h e use of all i n h e r e n t se l f -control l ing e l e m e n t s in t h e s y s t e m . T h e e l i m i n a t i o n of " s e r v i c e " sys t ems , w h e t h e r e lectr ical , p n e u m a t i c , or h y d r a u l i c , in favor of d i rec t a c t u a t i o n a n d seq u e n c i n g f rom bas ic eng ine p a r a m e t e r s is r e c o m m e n d e d as a n a p p r o a c h to bas ic re l iabi l i ty . O t h e r app roaches t o rel iabi l i ty t h r o u g h s impl ic i ty a re t h e use of m e c h a n i c a l i n t e r c o n n e c t i o n of valves for a c t u a t i o n , t h e r m a l i so la t ion t o avoid h e a t e r e l e m e n t s , a n d , in t h e case of miss i le e n gines , t h e loca t ion of m a l f u n c t i o n a n d sequence m o n i t o r ing e q u i p m e n t in t h e g r o u n d con t ro l console r a t h e r t h a n t h e eng ine .