The purpose of this paper i s t o r e p o r t r e c e n t r e s u l t s of an in-house conceptual study t o e v a l u a t e t h e performance p o t e n t i a l and research needs of a i rbreathing hypersonic m i s s i l e s . An alkylated-borane (noncryogenic) f u e l e d , dual-mode, ramjet/scranijet propulsion system s t r u c t u r e d w i t h a Rene'41 i n l e t and a carbon-carbon combustor was assumed along w i t t l a Lockalloy heat sink f u s e l a g e s t r u c t u r e a n d b e r y llium wings and control s u r f a c e s . Performance f o r an air-launched b a s e l i n e m i s s i l e w i t h a 961 pound s t a gi n g weight containing a 100 pound payload i n d i c a t e d e x c e l l e n t long range c r u i s e , moderate a c c e l e r a t i o n and high maneuverability p o t e n t i a l . For example: a t Mach 6 c r u i s e conditions (103,000 f t . ) , c r u i s e range exceeded 700 n.m.; horizontal a c c e l e r a t i o n s of 9 g ' s a r e o b t a i n a b l e f o r Mach numbers froni 4 t o 7 a t 30,000 f e e t ; approximately 40 g thrust-equal-drag turns a r e achievable w i t h t h e b a s e l i n e concept a t f l i g h t dynamic pressures of 10,000 psf ( M = 6 , 40,000 f t . ) . ranges of t h e o r d e r of 2500 nautical miles f o r payloads of 300 pounds can be achieved with moderate s i z e n.,issile c a r r y weights (9000 l b s , ) . Aerodynami c heatina analvses i n d i c a t e t h a t unprotected heat-A s i z i n g study i n d i c a t e s t h a t Mach 6 c r u i s e t o a s s e s s t h e p o t e n t i a l of t h e technology being developed i n Langley's hypersonic R&T programs f o r a p p l i c a t i o n s t o a i r b r e a t h i n g m i s s i l e s and t o ident i f y p o t e n t i a l a r e a s f o r f u r t h e r research. The i n t e n t was t o d e f i n e a concept f o r an a i r -b r e a t hing hypersonic l i f t i n g m i s s i l e and t o determine p o t e n t i a l performance and s c a l i n g r e l a t i o n s h i p s . To s p e c i f y weight and deterinine t h e magnitude of t h e technological o b s t a c l e s , i t was necessary t o d e f i n e a t l e a s t one s t r u c t u r a l approach f o r eng i n e s , a i r f r a m e , and radomes, and t o a s s e s s ihermos t r u c t u r a l l i m i t a t i o n s . Ooeratino Mach numbers from 4 t o 9 were i n v e s t i g a t e d . Concepts w i t h ranqes from 20 t o 3500 nautical miles and payloads from 70 t o 500 pounds were s t u d i e d . Symbois A a r e a A' area a t shock p o s i t i o n C s p e c i f i c heat modulus of e l a s t i c i t y ultiiiiate t e n s i l e s t r e n g t h P ET F t u sink s t r u c t u r e s -w i t h i n t e r n a l i n s u l a t i o n a r e f e a s ib l e f o r ranges of several hundred miles. For ranges of several thousands of miles a multiwall r a d i a t i o n s h i e l d ( I n c o n e l f t i t a n i u m ) was s e l e c t e d f o r protect i o n of t h e i n t e r n a l l y i n s u l a t e d heat sink s t r u c t u r e . Research areas in propulsion, propulsion i n t eg r a t i o n , c o n f i...