M A N - T O - T H E - M O O N A N D R E T U R N MISSION U T I L I Z I N G L U N A R - S U R F A C E R E N D E Z V O U S1
John G . S m a l l ^ and W . J. D o w n h o w e r ^ Jet P r o p u l s i o n L a b o r a t o r y
C a l i f o r n i a Institute of T e c h n o l o g y P a s a d e n a , C a l i f .
A B S T R A C T
T h i s p a p e r e x a m i n e s the p r o b l e m s of p l a c i n g a man on the moon at an e a r l y date and s u g g e s t s the lunar r e n d e z v o u s technique as one p o s s i b l e s o l u t i o n . It e x a m i n e s in d e t a i l the m i s s i o n p r o c e d u r e s of: e s c a p e f r o m E a r t h , t r a n s i t to the moon, lunar landing, s u r f a c e o p e r a t i o n s , lunar launch and i n j e c t i o n , r e t u r n t r a n s i t to E a r t h , r e - e n t r y into the E a r t h ' s a t m o s p h e r e , r e c o v e r y of the r e - e n t r y body, support and p r o - t e c t i o n of human c r e w m e m b e r s throughout a l l p h a s e s , and abort c a p a b i l i t y f o r the manned p o r t i o n of the S y s t e m . B e c a u s e of the c o m p l e x i t y of this m i s s i o n , each m o d u l e i s e x a m i n e d s e p a r a t e l y . C r i t i c a l a r e a s a r e i d e n t i f i e d and o p e r - ational s e q u e n c e s a r e outlined s e p a r a t e l y .
P r e s e n t e d at the A R S L u n a r M i s s i o n s M e e t i n g , C l e v e - land, Ohio, July 17-19, 1962.
^ T h i s p a p e r p r e s e n t s the r e s u l t s of one phase of r e s e a r c h c a r r i e d out at the Jet P r o p u l s i o n L a b o r a t o r y , C a l i f o r n i a I n s t i - tute of T e c h n o l o g y , under C o n t r a c t N o . N A S 7-100, s p o n s o r e d by the N a t i o n a l A e r o n a u t i c s and Space A d m i n i s t r a t i o n . T h i s p a p e r i s an u n c l a s s i f i e d e x c e r p t of T e c h n i c a l M e m o r a n d u m N o . 3 3 - 5 3 .
2
Section Chief, S y s t e m s D e s i g n S e c t i o n
^ S u p e r v i s o r , D e s i g n Study G r o u p , S y s t e m s D i v i s i o n
J . G . SMALL A N D W . J . DOWNHOWER
I N T R O D U C T I O N
T h e e a r l y a c c o m p l i s h m e n t of the manned lunar landing and r e t u r n m i s s i o n has been chosen as a p r i m a r y g o a l of the s p a c e e x p l o r a t i o n p r o g r a m of the N a t i o n a l A e r o n a u t i c s and Space A d m i n i s t r a t i o n ( N A S A ) . T h i s p a p e r p r e s e n t s the r e s u l t s of a study p e r f o r m e d by the Jet P r o p u l s i o n L a b o r a t o r y ( J P L ) on the use of a l u n a r - s u r f a c e r e n d e z v o u s technique f o r m i s s i o n a c c o m p l i s h m e n t .
T h e l u n a r - s u r f a c e r e n d e z v o u s technique was chosen f o r d e t a i l e d study b e c a u s e it o f f e r s s e v e r a l inherent a d v a n - t a g e s , both in t e r m s of e a r l y and r e l i a b l e m i s s i o n a c c o m p l i s h - ment and in future g r o w t h p o t e n t i a l . A d v a n t a g e s which apply to e a r l y and r e l i a b l e m i s s i o n a c c o m p l i s h m e n t include:
1) U s e of a natural b o d y - - t h a t i s , the moon, which maintains i t s e l f , as a s p a c e station o r a s s e m b l y a r e a . W e i g h t l e s s n e s s p r o b l e m s a r e a v o i d e d , a n d known lunar c o n d i - tions m a y b e used as d e s i g n c r i t e r i a .
2) M i s s i o n a c c o m p l i s h m e n t by m e a n s of l u n a r - s u r f a c e r e n d e z v o u s , as do other r e n d e z v o u s and a s s e m b l y techniques, o f f e r s f l e x i b i l i t y in adjusting m i s s i o n r e q u i r e - m e n t s to fluctuations in p a y l o a d r e q u i r e m e n t s and v e h i c l e c a p a b i l i t y by m e a n s of adding a v e h i c l e to the m i s s i o n s e q u e n c e . T h u s , the c r i t i c a l dependence of future m i s s i o n c a p a b i l i t y o n . d e c i s i o n s r e l a t i n g to launching v e h i c l e d e s i g n and d e v e l o p m e n t i s r e d u c e d .
3) A b i l i t y to s t a r t p a r a l l e l e f f o r t s on a l l s y s t e m e l e - ments now, without dependence on the c a p a b i l i t y of injecting l a r g e w e i g h t s into E a r t h - o r b i t o r e s c a p e t r a j e c t o r i e s .
4) T h e automatic lunar a s s e m b l y and checkout o p e r - ations m a y be s i m u l a t e d on E a r t h .
5) R a p i d r e l i a b i l i t y buildup and subsequent m a n - r a t i n g of the s y s t e m e l e m e n t s is a c c o m p l i s h e d by unmanned p r o p u l s i o n rounds which s t o c k - p i l e m a t e r i a l s on the moon b e f o r e the manned p o r t i o n of the m i s s i o n i s c a r r i e d out. T h e p r o p u l s i o n and manned p a y l o a d s u t i l i z e i d e n t i c a l e i s - l u n a r t r a n s i t , lunar landing, and lunar takeoff s y s t e m s .
6) T h e manned p o r t i o n of the m i s s i o n need not b e c o m m i t t e d until a c h e c k e d - o u t r e t u r n s y s t e m is a v a i l a b l e on the M o o n .
7) P r e v i o u s l y landed s p a c e c r a f t can p r o v i d e a p p r o a c h guidance b e a c o n s and T V m o n i t o r s f o r the lunar m a n n e d - landing s e q u e n c e . T h e s e aids p r o v i d e s a f e t y m a r g i n s in the final m a n n e d - l a n d i n g s e q u e n c e which a r e c o m p a r a b l e to those in use by E a r t h a i r c r a f t .
In t e r m s of g r o w t h p o t e n t i a l , the l u n a r - s u r f a c e r e n d e z - vous c o n c e p t is a t t r a c t i v e b e c a u s e it o f f e r s e a r l y d e v e l o p m e n t of techniques r e q u i r e d by advanced m i s s i o n s . E x t e n s i v e manned lunar e x p l o r a t i o n and the e s t a b l i s h m e n t of a lunar b a s e o r s c i e n t i f i c station r e q u i r e the a b i l i t y to p e r f o r m lunar - s u r f a c e o p e r a t i o n s , including the r e n d e z v o u s of p a y l o a d s on the Moon and the c o n s t r u c t i o n and maintenance of l o n g - l i f e t i m e lunar f a c i l i t i e s .
T h e study r e s u l t s include the f o l l o w i n g i t e m s :
1) D e v e l o p m e n t of a s y s t e m concept f o r the manned l u n a r - l a n d i n g and r e t u r n m i s s i o n by means of l u n a r - s u r f a c e r e n d e z v o u s .
2) F u n c t i o n a l d e s c r i p t i o n s and w e i g h t e s t i m a t e s f o r s y s t e m e l e m e n t s b a s e d on m i s s i o n a c c o m p l i s h m e n t u t i l i z i n g a Saturn launching v e h i c l e with an e s t i m a t e d 30, 000-lb lunar injection c a p a b i l i t y .
3) A n o p e r a t i o n a l s e q u e n c e f o r the m i s s i o n .
4) S y s t e m v a r i a t i o n s f o r a t h r e e - m a n m i s s i o n and a m i n i m u m o n e - m a n m i s s i o n .
5) E x a m i n a t i o n of the f e a s i b i l i t y of two c r i t i c a l m i s - sion functions; that i s , the l u n a r - l a n d i n g a c c u r a c y and the l u n a r - s u r f a c e o p e r a t i o n s .
6) A r e v i e w of the p r o g r a m l e a d i n g up to the manned l u n a r - l a n d i n g ?.nd r e t u r n m i s s i o n .
J . G . SMALL AND W . J . DOWNHOWER
T h e f o l l o w i n g ground r u l e s and m i s s i o n - d e s i g n c r i t e r i a h a v e g o v e r n e d the study e f f o r t :
1) M i s s i o n a c c o m p l i s h m e n t as soon as p o s s i b l e . 2) M a x i m u m r e l i a b i l i t y f o r a l l manned s y s t e m s and o p e r a t i o n s .
3) D e m o n s t r a t i o n of s y s t e m p e r f o r m a n c e and r e l i - a b i l i t y b e f o r e man i s included in the s y s t e m .
4) C o m p a t i b i l i t y of s y s t e m e l e m e n t s ( b o o s t e r , s p a c e - c r a f t , ground f a c i l i t i e s , and a c o m p l e t e m o n i t o r i n g s c h e m e ) as to s c h e d u l e s , p r o b l e m a r e a s , etc.
5) Human f a c t o r s and manned s u p p o r t - s y s t e m d e v e l - opment and r e - e n t r y t e c h n o l o g y p r o g r a m to be c a r r i e d out in n e a r - E a r t h s p a c e b e f o r e the manned lunar m i s s i o n is p e r - f o r m e d .
6) D e v e l o p m e n t of m a n ' s c a p a b i l i t i e s in both the s p a c e and lunar e n v i r o n m e n t i s a m a j o r p r o g r a m g o a l . T h e s y s t e m must b e c a p a b l e of c o m p l e t e l y automatic o p e r a t i o n and must p r o v i d e o v e r r i d e c a p a b i l i t y when d e s i r a b l e , i n o r d e r that man w i l l h a v e m a x i m u m f l e x i b i l i t y in adapting his tasks to the situation in which he finds h i m s e l f .
MISSION C O N C E P T
In c o n s i d e r i n g the s y s t e m r e q u i r e d to p e r f o r m a m i s - sion as c o m p l e x as the manned lunar landing and r e t u r n , it i s b e s t , w h e r e p o s s i b l e , to d i v i d e the s y s t e m into a finite n u m - b e r of p a r t s and e x a m i n e the t e c h n i c a l f e a s i b i l i t y and state of the art f o r each p a r t o r m o d u l e ( F i g . 1). T h i s study approach a l l o w s the c o n c e n t r a t i o n of the a p p r o p r i a t e s k i l l s on each p r o b - l e m and p e r m i t s e a r l y i d e n t i f i c a t i o n of the c r i t i c a l o r pacing p o r t i o n s of the s y s t e m . A n o v e r a l l m i s s i o n concept, which p e r m i t s m i s s i o n a c c o m p l i s h m e n t and a v o i d s as many p r o b l e m a r e a s as is p o s s i b l e , m a y then be d e v e l o p e d by c o n s i d e r i n g the s e v e r a l s y s t e m m o d u l e s .
T h e m o d u l e s of the s y s t e m m a y b e defined e i t h e r by function o r by any other a p p r o p r i a t e c r i t e r i a as long as the
r e l a t i o n s h i p , o r i n t e r f a c e , b e t w e e n m o d u l e s i s kept as s i m p l e as p o s s i b l e . If the v a r i o u s i n t e r f a c e s b e t w e e n m o d u l e s within the s y s t e m b e c o m e c o m p l e x and difficult to d e f i n e , the a d v a n - t a g e s of the m o d u l a r a p p r o a c h a r e l o s t and s y s t e m i n t e g r a t i o n b e c o m e s the p a c i n g i t e m of the p r o j e c t .
A n a p p r o p r i a t e set of m o d u l e s f o r the manned lunar landing and r e t u r n s y s t e m m a y be chosen by i d e n t i f y i n g the functions r e q u i r e d by the m i s s i o n . T h e b r o a d functional r e q u i r e m e n t s f o r s u c c e s s f u l m i s s i o n a c c o m p l i s h m e n t a r e as f o l l o w s : 1) e s c a p e f r o m E a r t h ; 2) t r a n s i t to the m o o n ; 3) lunar landing; 4) l u n a r - s u r f a c e o p e r a t i o n s ; 5) lunar launch and i n j e c t i o n ; 6) r e t u r n t r a n s i t to E a r t h ; 7) r e - e n t r y into the E a r t h ' s a t m o s p h e r e ; 8) r e c o v e r y of the r e - e n t r y body; 9) support and p r o t e c t i o n of human c r e w m e m b e r s throughout a l l phases of the m i s s i o n ; 10) a b o r t c a p a b i l i t y f o r the manned p o r t i o n of the s y s t e m .
G r o u p i n g of r e l a t e d functions r e s u l t s in the f o l l o w i n g set of g r o s s s y s t e m e l e m e n t s : 1) c o m m a n d m o d u l e ( r e - e n t r y b o d y ) ; 2) m i s s i o n m o d u l e ; 3) t r a n s i t , landing, and r e t u r n m o d u l e ; 4) E a r t h i n j e c t i o n s y s t e m (launching v e h i c l e s and r e n d e z v o u s and a s s e m b l y t e c h n i q u e s ) .
T h e c h a r a c t e r i s t i c s of each m o d u l e a r e d i s c u s s e d in the f o l l o w i n g p a r a g r a p h s .
M o d u l e C h a r a c t e r i s t i c s
C o m m a n d m o d u l e . T h i s m o d u l e includes human c r e w and support and p r o t e c t i o n f o r the c r e w . B e c a u s e of the abort r e q u i r e m e n t , the unit must a l s o b e the r e - e n t r y body. T h i s m o d u l e must contain l i f e support f o r a t i m e p e r i o d sufficient to c o v e r both n o r m a l and a b o r t m o d e s . F o o d and o t h e r sup- p l i e s f o r extended lunar o p e r a t i o n s m a y be s t o r e d in o t h e r p a r t s of the s y s t e m . T h e p r i m a r y i t e m s affecting the d e s i g n of this m o d u l e a r e human f a c t o r s and r e - e n t r y c o n d i t i o n s .
M i s s i o n m o d u l e . T h i s p a c k a g e p r o v i d e s additional human supplies f o r extended m i s s i o n l i f e t i m e ( f o o d , e t c . ) and the i n s t r u m e n t s and equipment r e q u i r e d b y the p a r t i c u l a r m i s - sion. T h e unit m a y be e n v i r o n m e n t a l l y c o n t r o l l e d in o r d e r to p r o v i d e additional o p e r a t i n g a r e a f o r the c r e w .
J. G. SMALL AND W . J. DOWNHOWER
T r a n s i t , landing, and r e t u r n m o d u l e (the b u s ) . T h i s unit is a t r a n s p o r t a t i o n s p a c e c r a f t c a p a b l e of p e r f o r m i n g the f o l l o w i n g functions: 1) t r a n s p o r t a t i o n of a p a y l o a d f r o m n e a r - E a r t h injection to the v i c i n i t y of the Moon (including m i d - c o u r s e c o r r e c t i o n s ) ; 2) p r e c i s e soft landing of the p a y l o a d on the lunar s u r f a c e (including h o v e r i n g and t r a n s l a t i o n c a p a b i l - i t i e s ) ; 3) launch of the E a r t h - r e t u r n s y s t e m f r o m the lunar s u r f a c e ; 4) t r a n s p o r t a t i o n of a p a y l o a d f r o m the v i c i n i t y of the Moon to the s e l e c t e d E a r t h r e - e n t r y c o r r i d o r (including m i d c o u r s e c o r r e c t i o n s and t e r m i n a l m a n e u v e r ) .
A l l of the s p a c e c r a f t s u b s y s t e m s (such as attitude c o n - t r o l , p o w e r supply, p r o p u l s i o n , landing s t r u c t u r e , e t c . ) r e q u i r e d to a c h i e v e these functions a r e included in this bus m o d u l e and a r e distinct f r o m the p a y l o a d ; that i s , the bus can p e r f o r m its m i s s i o n , r e g a r d l e s s of the p a y l o a d , f o r any p a y - l o a d m e e t i n g the g r o s s r e s t r i c t i o n of w e i g h t , v o l u m e , shape, c e n t e r of g r a v i t y , l o c a t i o n , e t c . T h e guidance s y s t e m
e m p l o y e d by the bus would include an o v e r r i d e m o d e in o r d e r that d i r e c t i o n of the final landing s e q u e n c e could be a c c o m - p l i s h e d e i t h e r by an E a r t h - c o m m a n d link o r b y the c r e w . T h e bus a l s o p r o v i d e s c e r t a i n support functions to the p a y l o a d in the f o r m of p o w e r supply, c o m m u n i c a t i o n s c a p a b i l i t y , and a v a i l a b l e f i e l d s of v i e w .
E a r t h i n j e c t i o n s y s t e m . T h e launching v e h i c l e
r e q u i r e d to p e r f o r m the manned l u n a r - l a n d i n g and r e t u r n m i s - sion i s dependent on t w o f a c t o r s : 1) the weight of the s e v e r a l m i s s i o n e l e m e n t s ; 2) the e n e r g y m a n a g e m e n t s c h e m e
e m p l o y e d . T h e s e v e r a l a l t e r n a t e a p p r o a c h e s f o r the m i s s i o n of i n t e r e s t i n c l u d e :
1) D i r e c t launch of the c o m p l e t e m i s s i o n s y s t e m by a N o v a - c l a s s b o o s t e r .
2) Launch of s y s t e m e l e m e n t s by a Saturn b o o s t e r , with s y s t e m a s s e m b l y b e i n g p e r f o r m e d a ) in E a r t h o r b i t , b ) in lunar o r b i t , c ) on the lunar s u r f a c e , o r d) v a r i o u s c o m b i n - ations of a ) , b ) , and c ) .
S e l e c t e d M i s s i o n C o n c e p t
T h e p a r t i c u l a r m i s s i o n c o n c e p t d i s c u s s e d in d e t a i l in the f o l l o w i n g p a g e s and i l l u s t r a t e d by T a b l e 1 and F i g . 2 would r e q u i r e the a c c o m p l i s h m e n t of the i n i t i a l manned lunar m i s s i o n with a Saturn-launched r e t u r n s p a c e c r a f t a s s e m b l e d on the lunar s u r f a c e . It was a s s u m e d that a Saturn-launched s p a c e c r a f t could s o f t - l a n d a p p r o x i m a t e l y 10, 000 l b on the lunar s u r f a c e . P r e v i o u s S u r v e y o r o r R a n g e r s p a c e c r a f t would
e s t a b l i s h the landing s i t e and p r o v i d e h o m i n g b e a c o n s , T V m o n i t o r i n g equipment, e t c . A n u m b e r of methods f o r r e f u e l - ing on the lunar s u r f a c e m a y b e e n v i s i o n e d .
One p o s s i b l e concept f o l l o w s : T h r e e 10, 000-lb r e f u e l - ing s p a c e c r a f t would be landed at points a p p r o x i m a t e l y e q u a l l y s p a c e d around, and within 45 ft of, a s p a c e c r a f t c o m p r i s e d of a bus and unmanned c o m m a n d m o d u l e s u i t a b l e f o r r e t u r n i n g t h r e e m e n to E a r t h . S o l i d - p r o p u l s i o n units would be t r a n s - f e r r e d f r o m the r e f u e l i n g s p a c e c r a f t to the c e n t r a l l y l o c a t e d r e t u r n s p a c e c r a f t by m e a n s of s p e c i a l l y d e s i g n e d t r a n s f e r t r a c k s . T h e a s s e m b l y o p e r a t i o n would be m o n i t o r e d by T V , and the a s s e m b l e d v e h i c l e would be c h e c k e d out b e f o r e s e n d - ing a man f r o m E a r t h to the a r e a v i a a s e c o n d s p a c e c r a f t c o m - p o s e d of a bus and c o m m a n d m o d u l e .
T h e lunar c o m p l e x s o e s t a b l i s h e d would be c a p a b l e of maintaining i t s e l f in the lunar e n v i r o n m e n t . T h e c r e w would p e r f o r m any r e q u i r e d lunar m i s s i o n functions upon landing and would than t r a n s f e r to the waiting r e t u r n v e h i c l e and r e t u r n to E a r t h . If, f o r any r e a s o n , the c r e w should d e t e r m i n e that the p r e v i o u s l y landed and a s s e m b l e d s p a c e c r a f t should not be used for the r e t u r n f l i g h t , the automatic r e f u e l i n g equipment could be used to r e t r a n s f e r the p r o p u l s i o n units to the s p a c e c r a f t in which the c r e w a r r i v e d ; this s p a c e c r a f t would then be used f o r the r e t u r n to E a r t h . T h e t h r e e s o l i d - p r o p e l l a n t r o c k e t s used for launch f r o m the lunar s u r f a c e a r e i d e n t i c a l with the r e t r o r o c k e t s used f o r each v e h i c l e in landing on the M o o n . T h e s e r e t r o r o c k e t s a r e j e t t i s o n e d at s o m e d i s t a n c e f r o m the a s s e m - bly s i t e during the v e r n i e r d e s c e n t and touchdown m a n e u v e r . T h r u s t - v e c t o r c o n t r o l and p r o p u l s i o n f o r the v e r n i e r d e s c e n t and touchdown i s supplied b y t h r o t t l a b l e l i q u i d v e r n i e r m o t o r s . A l a r g e amount of the t e c h n o l o g y d e v e l o p e d f o r S u r v e y o r would be u t i l i z e d in this c o n c e p t f o r the manned lunar landing. T h e
J. G. SMALL AND W . J. DOWNHOWER
r e t u r n - v e h i c l e w e i g h t would be a p p r o x i m a t e l y 29, 800 lb at lunar takeoff, 10, 7 00 lb at lunar i n j e c t i o n , 10, 000 lb as E a r t h i s approached, and 5300 lb at E a r t h e n t r y .
T h e Saturn would be used throughout f o r the E a r t h - based launching v e h i c l e . A m i n i m u m of f i v e s u c c e s s f u l launches would be r e q u i r e d f o r the b a s i c m i s s i o n . T h e actual number r e q u i r e d to a c c o m p l i s h the m i s s i o n would be a d i r e c t function of the s u c c e s s r a t e of the f i r i n g s and a s s e m b l y o p e r - ations on the lunar s u r f a c e ; h o w e v e r , any f a i l u r e b e f o r e the manned landing would not affect the s u c c e s s of the manned lunar landing s e q u e n c e . I d e n t i c a l t r a n s i t , landing, and r e t u r n m o d u l e s would be used in a l l launches and landings;
only the p a y l o a d s would d i f f e r - - t h a t i s , c o m m a n d m o d u l e s o r r e t u r n p r o p u l s i o n .
T h e a b o r t c a p a b i l i t i e s p r o v i d e d by this m i s s i o n c o n - cept a r e f o r the r e t u r n of the manned c o m m a n d m o d u l e to E a r t h f o r as l a r g e a p o r t i o n of the m i s s i o n as i s p o s s i b l e . A s e p a r a b l e abort r o c k e t s y s t e m would p e r f o r m the abort func- tion during the a t m o s p h e r i c p o r t i o n of the flight and would function in the event of a c a t a s t r o p h i c f a i l u r e of the b o o s t e r v e h i c l e . A penalty of 250 lb to the i n j e c t e d p a y l o a d would o c c u r in maintaining this c a p a b i l i t y up to j e t t i s o n i n g of the unit ( p r i o r to i n j e c t i o n ) . In the event that the m i s s i o n w e r e to be a b o r t e d after the j e t t i s o n i n g and p r i o r to the lunar t e r m i n a l phase, the lunar r e t r o - p r o p u l s i o n and v e r n i e r - p r o p u l s i o n units would be u t i l i z e d to a b o r t .
D e t a i l e d d e s c r i p t i o n s of the s y s t e m e l e m e n t s and the m i s s i o n s t e p s a r e g i v e n in subsequent p a r a g r a p h s .
P R O G R A M A S P E C T S
A b r i e f e x a m i n a t i o n of the lunar e x p l o r a t i o n p r o g r a m l e a d i n g up to the manned l u n a r - l a n d i n g and r e t u r n m i s s i o n , and e v e n t u a l l y to the e s t a b l i s h m e n t of a lunar b a s e o r s c i e n - tific o b s e r v a t o r y , has been included in the p r e s e n t study. T h e i n t e r r e l a t i o n s h i p of the v a r i o u s d e v e l o p m e n t s and e v e n t s l e a d - ing up to the a c c o m p l i s h m e n t of the manned l u n a r - l a n d i n g and r e t u r n m i s s i o n m a y be d e m o n s t r a t e d by e x a m i n i n g the m i s s i o n r e q u i r e m e n t s . G r o s s r e q u i r e m e n t s f o r the c a p a b i l i t y to p e r - f o r m the manned l u n a r - l a n d i n g and r e t u r n m i s s i o n a r e :
1) D e t e r m i n a t i o n of the data r e q u i r e d f o r s y s t e m d e s i g n . T h e p r i m a r y a r e a of i n t e r e s t i s the definition of the s e v e r a l e n v i r o n m e n t s - - e i s - l u n a r , lunar, and r e - e n t r y - - i n which the s y s t e m must o p e r a t e and p r o v i d e p r o t e c t i o n and support f o r the human c r e w . S e v e r a l e x p e r i m e n t a l p r o g r a m s a r e r e q u i r e d to obtain such data.
2) D e t e r m i n a t i o n and d e v e l o p m e n t of the techniques r e q u i r e d f o r m i s s i o n a c c o m p l i s h m e n t . T h e p r i m a r y a r e a s of t e c h n o l o g y r e q u i r e d by the manned l u n a r - l a n d i n g and r e t u r n m i s s i o n a r e : a ) launching v e h i c l e and e n e r g y - m a n a g e m e n t t e c h n o l o g y ( i n c l u d i n g r e n d e z v o u s t e c h n i q u e s ) , b ) s p a c e -
t r a n s i t t e c h n o l o g y , c ) v a c u u m - l a n d i n g t e c h n o l o g y , d ) human f a c t o r s and manned s u p p o r t - s y s t e m t e c h n o l o g y , e ) r e - e n t r y and r e c o v e r y t e c h n o l o g y .
3) D e v e l o p m e n t of the actual s y s t e m h a r d w a r e , both flight h a r d w a r e and g r o u n d - s u p p o r t h a r d w a r e and f a c i l i t i e s .
In o r d e r to fulfill t h e s e r e q u i r e m e n t s , the e l e m e n t s of the s e v e r a l N A S A s p a c e e x p l o r a t i o n p r o g r a m s w i l l be u t i l i z e d . F i g u r e s 3 through 8 show the g r o w t h in e n v i r o n m e n t definition and d e v e l o p m e n t of t e c h n o l o g y . T h e h a r d w a r e d e v e l o p m e n t schedule f o r the actual m i s s i o n i s shown in P a r t I of this s e c - tion.
S Y S T E M E L E M E N T S ; T H R E E - M A N L U N A R - L A N D I N G MISSION
T h e t h r e e - m a n l u n a r - l a n d i n g m i s s i o n contains the s y s - t e m e l e m e n t s l i s t e d b e l o w , in addition to the Saturn launching v e h i c l e s . T h e s p a c e c r a f t must contain the s p a c e c r a f t bus m o d u l e and m a y contain v a r i o u s o t h e r m o d u l e s : 1) c o m m a n d m o d u l e , 2) s p a c e c r a f t bus m o d u l e , 3) e n v i r o n m e n t a l c o n t r o l support c a p s u l e , 4 ) m i s s i o n m o d u l e , 5) p r o p u l s i o n m o d u l e . F i g u r e 2 i s a d i a g r a m s h o w i n g the r e l a t i o n s h i p of the v a r i o u s s y s t e m e l e m e n t s .
C o m m a n d M o d u l e ( M a n n e d C a p s u l e )
T h i s m o d u l e has the f o l l o w i n g functions: l i f e support;
m i s s i o n p a r a m e t e r d i s p l a y s f o r c r e w ; p r o v i d e s f o r manned p a r t i c i p a t i o n in the flight and evaluation of m a n ' s c a p a b i l i t y in
J . G . SMALL AND W . J . DOWNHOWER
s p a c e ; c o u p l e s man with the c o m m u n i c a t i o n s y s t e m ; p r o v i d e s E a r t h entry, landing, and r e c o v e r y c a p a b i l i t y ; and, to a m a j o r extent, p a r t i c i p a t e s in the abort m o d e s of o p e r a t i o n .
T h e m o d u l e p r e s e n t e d h e r e i s d e r i v e d f r o m the A p o l l o Industry Study C a p s u l e s , c o n s i d e r i n g the f o l l o w i n g m o d i f i c a - tions to m e e t the lunar r e n d e z v o u s m i s s i o n concept:
T h e b a s i c s p a c e - a b o r t and l u n a r - r e t u r n unit i s c o m - p o s e d of the c o m m a n d m o d u l e and the bus. T h e r e f o r e , a l l l i f e - s u p p o r t s y s t e m s must be on t h e s e m o d u l e s with the m a j o r p o r t i o n on the c o m m a n d m o d u l e .
N o r a d i a t i o n p r o t e c t i o n other than that a f f o r d e d by the s t r u c t u r e and the equipment has been s p e c i f i c a l l y included in the c o m m a n d m o d u l e . H o w e v e r , the m i s s i o n w e i g h t s u m - m a r i e s ( T a b l e s 2 through 8) show a w e i g h t c o n t i n g e n c y a l l o w - ance of a p p r o x i m a t e l y 7 50 l b . T h i s weight m i g h t be used to p r o v i d e r a d i a t i o n s h i e l d i n g in a r e a s w h e r e the c o m m a n d m o d - ule s t r u c t u r e is insufficient f o r human p r o t e c t i o n . A d e c i s i o n in this a r e a depends on further definition of the r a d i a t i o n s h i e l d i n g r e q u i r e m e n t s and on the actual d e s i g n of the c o m - mand m o d u l e . In the event that r a d i a t i o n data obtained in the future indicate a h e a v y s h i e l d i n g r e q u i r e m e n t , the m i s s i o n m a y be m o d i f i e d to include a h e a v i e r c o m m a n d m o d u l e and additional r e f u e l i n g p a y l o a d s .
P r i m a r y i t e m s affecting c o m m a n d - m o d u l e d e s i g n a r e : 1) e n t r y and r e c o v e r y m i s s i o n ; 2) s p a c e e n v i r o n m e n t , includ- ing r a d i a t i o n and m e t e o r i t e p r o t e c t i o n , and w e i g h t l e s s n e s s ; 3) r e q u i r e d l i f e t i m e , including n o r m a l o p e r a t i o n s and abort m o d e s ; 4) methods of manned p a r t i c i p a t i o n in the m i s s i o n and study of m a n ' s c a p a b i l i t y ; 5) n u m b e r in c r e w ; 6) p r o v i s i o n f o r use in o t h e r m i s s i o n s ; t r a i n i n g , E a r t h - o r b i t a l f l i g h t s , d i r e c t use in manned E a r t h r e n d e z v o u s , e t c .
S p a c e c r a f t Bus M o d u l e
T h e s p a c e c r a f t bus p e r f o r m s the e i s - l u n a r t r a n s i t , lunar landing, lunar launch, and r e t u r n p o r t i o n s of the m i s - s i o n . T h e techniques p e r f o r m e d by the bus s y s t e m d e s c r i b e d in this study a r e c l o s e l y r e l a t e d to those of the R a n g e r and S u r v e y o r s p a c e c r a f t s y s t e m s . C e r t a i n additional functions
have been included which a r e d i r e c t l y r e l a t e d to the m i s s i o n of i n t e r e s t . In p a r t i c u l a r , the c a p a b i l i t y f o r extended h o v e r and t r a n s l a t i o n m o d e s and the a b i l i t y to land at a s p e c i f i c point on the lunar s u r f a c e a r e included in the p r o p o s e d bus s y s t e m . W e i g h t a l l o w a n c e s include p r o v i s i o n s f o r redundancy in a p p r o - p r i a t e p o r t i o n s of the s y s t e m . T h e bus s y s t e m r e c o m m e n d e d h e r e i s e s s e n t i a l l y that r e q u i r e d f o r the t r a n s p o r t a t i o n and landing of the P r o s p e c t o r s c i e n t i f i c p a c k a g e s .
T h e bus m o d u l e d e s c r i b e d in the w e i g h t s u m m a r y f o r the t h r e e - m a n l u n a r - l a n d i n g m i s s i o n ( T a b l e 4) i s b a s e d on a n o m i n a l Saturn i n j e c t i o n c a p a b i l i t y of 30, 000 l b . T h e l u n a r - landing and takeoff p r o p u l s i o n w e i g h t s a r e those f o r s t o r a b l e s o l i d - r o c k e t s y s t e m s ( ISp ~ 300 s e c ) ; this r e s u l t s in the capa- b i l i t y of s o f t - l a n d i n g a p p r o x i m a t e l y o n e - t h i r d of the weight i n j e c t e d to the Moon and of launching t o w a r d the E a r t h a p p r o x - i m a t e l y o n e - t h i r d of the g r o s s lunar takeoff w e i g h t . I d e n t i c a l p r o p u l s i o n units a r e used f o r both lunar landing and takeoff s e q u e n c e s . It i s b e l i e v e d that this a p p r o a c h to the lunar p r o - pulsion units ( i . e . , m o d e r a t e p e r f o r m a n c e r e q u i r e m e n t s and m a x i m u m r e l i a b i l i t y buildup by h e a v y u s e - r a t e of the unit) p r o v i d e s the b e s t solution t o the p r o b l e m of the l a c k of a b o r t c a p a b i l i t y during the lunar-launching phase of the manned m i s s i o n .
A s the p e r f o r m a n c e of the Saturn launching v e h i c l e i s not f i r m at this t i m e , this study includes an e x a m i n a t i o n of weight v a r i a t i o n s in the s p a c e c r a f t bus and final landed lunar p a y l o a d as a function of i n j e c t i o n w e i g h t . T h e e x p e c t e d bus and lunar p a y l o a d w e i g h t s f o r a r a n g e of i n j e c t i o n w e i g h t s c o v e r i n g v e h i c l e c a p a b i l i t i e s f r o m 10, 000 to 45, 000 lb a r e shown in T a b l e 8 of the w e i g h t s u m m a r y T a b l e s .
E n v i r o n m e n t a l C o n t r o l Support C a p s u l e ( E . C . S . P a c k a g e ) T h i s m o d u l e i s c a l l e d out s e p a r a t e l y in o r d e r to empha- s i z e the m i s s i o n c o n c e p t , and the unit m a y o r m a y not be a p h y s i c a l l y s e p a r a b l e i t e m f r o m the c o m m a n d m o d u l e .
It i s e v i d e n t f r o m the A p o l l o studies and f r o m the lunar a s s e m b l y m i s s i o n concept that s o m e units of the r e q u i r e d l i f e support a r e e s s e n t i a l f o r the s p a c e m o d e of o p e r a t i o n but not e s s e n t i a l to the e n t r y function. In the A p o l l o s t u d i e s , t h e s e
J . G . SMALL A N D W . J . DOWNHOWER
i t e m s a r e , in g e n e r a l , i n t e g r a t e d into the m i s s i o n m o d u l e s , but, f o r the lunar a s s e m b l y c o n c e p t , they must attach to the bus o r c o m m a n d m o d u l e . Functions c o v e r e d a r e : 1) p a r t s of the l i f e - s u p p o r t s y s t e m s e x t e r n a l to the l i f e - s u p p o r t p r e s s u r e v e s s e l ( i . e. , r a d i a t o r f o r t h e r m a l - c o n t r o l s y s t e m ) ; 2) r e d u n - dancy r e q u i r e d f o r s p a c e o p e r a t i o n s but not f o r e n t r y and r e c o v e r y ( i . e. , s p a r e a t m o s p h e r e - c o n t r o l s y s t e m as r e q u i r e d ) 3) p r o v i s i o n of added l i f e - s u p p o r t c a p a c i t y f o r m i s s i o n m o d - ule ( i . e. , additional g a s - c h a r g e s t o r a g e ) ; 4) augmentation of b a s i c bus functions ( i . e. , p o w e r f o r l i f e - s u p p o r t o p e r a t i o n s ) . M i s s i o n M o d u l e
T h e concept p r o p o s e d h e r e p r e s e n t s the m i s s i o n m o d - ule as an e a s i l y i n t e r c h a n g e a b l e unit with a m i n i m u m i n t e r f a c e with the r e s t of the s y s t e m . T h e m a j o r point of i n t e r e s t i s that it can be attached as a habitable w o r k a r e a , but it does not contain e l e m e n t s of the l i f e - s u p p o r t s y s t e m ; r a t h e r , the outputs of the l i f e - s u p p o r t s y s t e m a r e supplied to it through the i n t e r f a c e .
T h e s p e c i f i c m o d u l e p r o p o s e d h e r e i s c a r r i e d on the manned E a r t h - m o o n t r a n s i t . It p r o v i d e s t h r e e m a j o r functions:
1) a habitable a r e a of v o l u m e equal to that of the c o m m a n d m o d u l e during the E a r t h - l u n a r t r a n s i t and the landed o p e r a - tions; 2) a b a s e f o r E a r t h - l u n a r t r a n s i t and landed manned s c i e n c e o p e r a t i o n s ; 3) a b a s e f o r the manned p a r t s of the lunar o p e r a t i o n s and p r e p a r a t i o n f o r the r e t u r n t r a n s i t .
T h e m o d u l e i s not r e t u r n e d under the p r e s e n t s c h e m e but is left intact on the lunar s u r f a c e . It can be r e a d i l y adapted as an e l e m e n t of a p e r m a n e n t lunar b a s e , if such i s planned f o r the future. It s e e m s e v i d e n t that this d i s p o s i t i o n of the m o d u l e contributes m o r e to the o v e r a l l a i m s of the p r o - g r a m than the a l t e r n a t i v e of including it in the r e t u r n p a c k a g e . T h e weight a l l o c a t i o n i s adequate f o r future a l t e r n a t e m o d u l e s . E x a m p l e s a r e : 1) a l l o r p a r t o f a manned r o v i n g v e h i c l e and 2) an equipment p a c k a g e f o r landed s c i e n c e o p e r - ations o r lunar b a s e c o n s t r u c t i o n .
P r o p u l s i o n M o d u l e
T h e p r o p u l s i o n m o d u l e i s one of the-two p a y l o a d s c a r r i e d to the lunar s u r f a c e by the bus. T h e m o d u l e c o n s i s t s of a p o r t i o n of the r e t u r n p r o p u l s i o n , the a p p r o p r i a t e a u t o m a - tic r e f u e l i n g equipment and r e f u e l i n g m o n i t o r i n g equipment, the e n v i r o n m e n t a l c o n t r o l equipment r e q u i r e d to s t o r e the p r o - pulsion p r o p e r l y , and a p p r o p r i a t e i n s t r u m e n t a t i o n to m o n i t o r the condition of the r e t u r n p r o p u l s i o n .
S Y S T E M E L E M E N T S ; M I N I M U M O N E - M A N L U N A R - L A N D I N G MISSION
F o r c o m p a r i s o n with the t h r e e - m a n m i s s i o n , a o n e - man m i s s i o n has b e e n studied under the s a m e g e n e r a l ground r u l e s , including the use of the Saturn-launching v e h i c l e . A n attempt i s m a d e h e r e to d e v e l o p a m i n i m u m c o n c e p t in t e r m s of p a y l o a d r e q u i r e m e n t which can s t i l l s a t i s f y the b r o a d a i m s of the i n i t i a l lunar landing e f f o r t . T h e m i s s i o n c o n c e p t is i l l u s t r a t e d by T a b l e 9 and F i g . 2. W e i g h t s u m m a r i e s f o r the m i n i m u m o n e - m a n m i s s i o n a r e g i v e n in T a b l e s 4 and 10 through 14.
T h e s y s t e m e l e m e n t s f o r the o n e - m a n l u n a r - l a n d i n g m i s s i o n a r e as f o l l o w s : 1) c o m m a n d m o d u l e , 2) s p a c e c r a f t bus m o d u l e , 3) e n v i r o n m e n t a l c o n t r o l support c a p s u l e , 4 ) m i s s i o n m o d u l e , 5) p r o p u l s i o n m o d u l e .
T h e functional a s p e c t s of these e l e m e n t s a r e , in g e n - e r a l , the s a m e as f o r the t h r e e - m a n m i s s i o n . T h e c o m m a n d m o d u l e w e i g h t is s c a l e d in such a w a y that the total habitable v o l u m e f o r the s i n g l e occupant i s a p p r o x i m a t e l y equal to that a s s i g n e d to each man in the m o r e a m b i t i o u s m i s s i o n (about 340 ft^ p e r man, including v o l u m e o c c u p i e d by i n t e r n a l e q u i p - m e n t ) . In this c a s e , the c o m m a n d m o d u l e and the bus f o r m the b a s i c manned t r a n s i t unit both to and f r o m the m o o n . T Y P I C A L O P E R A T I O N A L S E Q U E N C E
In o r d e r to i n s u r e the e a r l y a c c o m p l i s h m e n t of the manned lunar m i s s i o n , m a x i m u m u t i l i z a t i o n must be m a d e of the techniques and o p e r a t i o n s which h a v e been d e v e l o p e d on p r e c e d i n g lunar m i s s i o n s . T h e o p e r a t i o n a l s e q u e n c e p r e s e n t e d
J. G. SMALL AND W . J. DOWNHOWER
h e r e ( T a b l e 15) m a k e s use of the s p a c e c r a f t t e c h n o l o g y which has been o r i s being e v o l v e d f r o m the R a n g e r , S u r v e y o r , and P r o s p e c t o r m i s s i o n s . T h e r e q u i r e m e n t to p l a c e s e v e r a l s p a c e c r a f t at a g i v e n s i t e on the lunar s u r f a c e can be c o n s i d - e r e d as an e x t e n s i o n of the S u r v e y o r guidance and p r o p u l s i o n s y s t e m s . F o r m a x i m u m r e l i a b i l i t y , the functioning of the v a r i o u s s p a c e c r a f t s u b s y s t e m s w i l l be e s t a b l i s h e d p r i o r to use on the manned m i s s i o n .
In addition to m a x i m u m u t i l i z a t i o n of the p r e c e d i n g lunar s p a c e c r a f t t e c h n o l o g y , it is planned that S u r v e y o r s w h o s e p a y l o a d s a r e m o d i f i e d f o r the p u r p o s e w i l l b e used in d i r e c t support of the manned m i s s i o n . T h e o p e r a t i o n a l s e q u e n c e should be c o n s i d e r e d t y p i c a l of one which would d e s c r i b e the m i s s i o n . V a r i a t i o n s a c c o r d i n g to the s e v e r a l payloads which the bus a c c o m m o d a t e s a r e i n d i c a t e d in the v e r n i e r ( t e r m i n a l ) phase of the lunar d e s c e n t .
L A N D I N G G U I D A N C E A C C U R A C Y
T w o g u i d a n c e - a c c u r a c y f i g u r e s a r e of i n t e r e s t f o r lunar m i s s i o n s : 1) the p r o x i m i t y with which a p a y l o a d can be d e l i v e r e d to a g i v e n point on the s u r f a c e ; 2) the a c c u r a c y with which it can be d e t e r m i n e d w h e r e the p a y l o a d has been d e l i v - e r e d . T h e a c c u r a c y r e q u i r e d is s t r o n g l y dependent upon the m i s s i o n to be p e r f o r m e d .
F o r the R a n g e r m i s s i o n s , it is sufficient to land within 100 km (30") of a n o m i n a l i m p a c t l o c a t i o n . T h e landing point must be known, h o w e v e r , to within 3 5 km b e c a u s e the payload r e t r o m o t o r must b e a l i g n e d within 1° of the approach v e l o c i t y v e c t o r . T h e f i r s t r e q u i r e m e n t i s m e t by p e r f o r m i n g a s i n g l e r a d i o - c o m m a n d e d t r a j e c t o r y - c o r r e c t i o n m a n e u v e r about 16 hr after i n j e c t i o n . T h e o r b i t d e t e r m i n a t i o n i s b a s e d upon a n g l e and r a n g e - r a t e ( D o o p l e r ) data f r o m the D e e p Space I n s t r u - mentation F a c i l i t y ( D S I F ) s t a t i o n s .
T h e e a r l y S u r v e y o r m i s s i o n s w i l l r e q u i r e s i m i l a r accu- r a c y . It i s e x p e c t e d that landing a c c u r a c y of 7 5 km (3σ) w i l l be a c h i e v e d , a s s u m i n g that a s i n g l e m i d c o u r s e c o r r e c t i o n i s p e r f o r m e d as d e s c r i b e d a b o v e . A s e c o n d m i d c o u r s e c o r r e c - tion m a d e a p p r o x i m a t e l y 24 hr after the f i r s t c o r r e c t i o n could further r e d u c e the e r r o r in l a n d i n g ; h o w e v e r , g r e a t e r p r e c i s i o n
in o r b i t d e t e r m i n a t i o n would be r e q u i r e d to m a k e a s i g n i f i c a n t c o r r e c t i o n .
It i s d e s i r a b l e that l a t e r S u r v e y o r p a y l o a d s include r a n g i n g e q u i p m e n t . T h e use of r a n g e data f o r t r a j e c t o r y c a l - culations w o u l d p e r m i t a s e c o n d guidance c o r r e c t i o n to a c h i e v e 1 0 - k m a c c u r a c y . F i g u r e 9 shows the r e d u c t i o n in i m p a c t e r r o r w i t h s u c c e s s i v e guidance c o r r e c t i o n s , a s s u m i n g r a n g i n g i s used.
F o r the lunar s u r f a c e r e n d e z v o u s m i s s i o n s , i t a p p e a r s d e s i r a b l e to d e l i v e r a p a y l o a d to within a few m e t e r s ( o r l e s s ) of a s p e c i f i e d point on the lunar s u r f a c e r e l a t i v e to an a l r e a d y e x i s t i n g p a y l o a d o r e q u i p m e n t . Guidance to this a c c u r a c y w o u l d r e q u i r e " h o m i n g " techniques to r e m o v e the n o m i n a l 10- k m landing d i s p e r s i o n .
F o r a S u r v e y o r - t y p e landing, it a p p e a r s m o s t e f f i c i e n t to i n i t i a t e " h o m i n g " when the v e r n i e r descent i s begun, f o l l o w - ing m a i n r e t r o burnout (at about 8 - k m a l t i t u d e ) . D u r i n g a n o r m a l v e r n i e r descent, the s p a c e c r a f t i s under the c o n t r o l of v a r i a b l e - t h r u s t e n g i n e s w h i c h a r e t h r o t t l e d to p r o v i d e the p r o p e r d e c e l e r a t i o n r a t e s . Both v e r t i c a l and h o r i z o n t a l v e l - o c i t y a r e s e n s e d with a D o p p l e r r a d a r . T h e s p a c e c r a f t i s t i p p e d o f f - t h e - v e r t i c a l in o r d e r to r e m o v e h o r i z o n t a l v e l o c i t y w h i c h e x i s t s f o l l o w i n g m a i n r e t r o burnout. When " h o m i n g " i s p e r f o r m e d , the s a m e technique i s u s e d to t r a n s l a t e t o w a r d the l u n a r - b a s e d b e a c o n .
A v a r i e t y of equipment i s a v a i l a b l e to d e t e r m i n e r a n g e and b e a r i n g to a p r e v i o u s l y landed b e a c o n . C o m m e r c i a l a i r - l i n e r s use d i r e c t i o n - f i n d i n g and d i s t a n c e - m e a s u r i n g d e v i c e s to a c c u r a c i e s of a f e w d e g r e e s and of the o r d e r of a k i l o m e t e r . T h e use of a t r a n s p o n d e r w i l l p r o v i d e r a n g e to 50 m .
If g r e a t e r a c c u r a c y i s r e q u i r e d , other techniques can be u s e d . P r e c i s e " h o m i n g " can be p e r f o r m e d w i t h v a r i o u s e l e c t r o n i c and o p t i c a l d e v i c e s to c e n t i m e t e r a c c u r a c y . It i s a l s o r e a s o n a b l e to c o n s i d e r E a r t h - b a s e d t e l e v i s i o n m o n i t o r i n g and c o n t r o l during the final h o v e r and descent p h a s e .
In o r d e r to p r o v i d e sufficient h o v e r i n g c a p a b i l i t y to r e m o v e a 10-km landing e r r o r , a p p r o x i m a t e l y 8% of the landed
J . G . SMALL AND W . J . DOWNHOWER
payload would b e r e q u i r e d f o r additional v e r n i e r p r o p e l l a n t , a s s u m i n g an ISp of 300 s e c . F o r a S u r v e y o r , this would c o r - r e s p o n d to about 60 l b of p a y l o a d , and the r e q u i r e m e n t v a r i e s d i r e c t l y with the landed w e i g h t . T h e total w e i g h t of e l e c t r o n i c g e a r r e q u i r e d on b o a r d the s p a c e c r a f t i s l e s s than 40 lb and is e s s e n t i a l l y independent of the s i z e of the landed v e h i c l e .
A n u m b e r of m e t h o d s a r e p o s s i b l e to r e d u c e the v e r - n i e r p r o p e l l a n t p e n a l t y d e s c r i b e d a b o v e . F o r e x a m p l e , t i m - ing of the t e r m i n a l s e q u e n c e could be changed in o r d e r to o p t i - m i z e the u t i l i z a t i o n of v e r n i e r p r o p e l l a n t . T h i s would i n v o l v e ignition at a s o m e w h a t h i g h e r altitude and the r e m o v a l of a s m a l l e r v e l o c i t y i n c r e m e n t with the main r e t r o m o t o r and a l a r g e r i n c r e m e n t with the v e r n i e r e n g i n e s . A s y s t e m s a n a l y - s i s would have to be p e r f o r m e d in o r d e r to d e t e r m i n e the o p t i - mum p a r a m e t e r s , but c e r t a i n l y a s i g n i f i c a n t p a r t of the v e r n i e r - p r o p u l s i o n penalty would be e l i m i n a t e d . F i g u r e 10 shows the r e d u c t i o n in landing e r r o r which i s a c h i e v e d with both of t h e s e m e t h o d s .
In c o n c l u s i o n , it a p p e a r s that " h o m i n g " to the r e q u i r e d p r e c i s i o n is e a s i l y a c c o m p l i s h e d . T h e fuel and w e i g h t a l l o w - ances d e s c r i b e d a r e e x t r e m e l y c o n s e r v a t i v e , and y e t , they a r e s m a l l enough that the " h o m i n g " technique can be r e a d i l y d e m o n s t r a t e d with a S u r v e y o r s p a c e c r a f t .
L U N A R R E F U E L I N G O P E R A T I O N S
T h e r e f u e l i n g o p e r a t i o n can be m e c h a n i z e d in one of s e v e r a l w a y s . A g r e a t amount of t e c h n o l o g y as w e l l as m a n y o f f - t h e - s h e l f c o m p o n e n t s e x i s t today which a r e a p p l i c a b l e to this t y p e of o p e r a t i o n . In g e n e r a l , the o p e r a t i o n i n v o l v e s t r a n s f e r r i n g p r o p e l l a n t f r o m the r e f u e l i n g s p a c e c r a f t to the r e t u r n s p a c e c r a f t , which can be a c c o m p l i s h e d b y e f f e c t i n g the t r a n s f e r e i t h e r a b o v e the s u r f a c e o r on the s u r f a c e .
W h e t h e r l i q u i d o r s o l i d p r o p e l l a n t s a r e used, s i m i l a r techniques a r e a p p l i c a b l e . H o w e v e r , s o l i d p r o p e l l a n t s a r e p r e s e n t e d h e r e .
A b o v e - t h e - S u r f a c e T r a n s p o r t
One of a n u m b e r of suitable a b o v e - t h e - s u r f a c e s y s t e m s i s d e s c r i b e d to i l l u s t r a t e that r e m o t e o p e r a t i o n s , such as a s s e m b l i n g o r r e f u e l i n g a r e t u r n s p a c e c r a f t on the lunar s u r - f a c e , a r e f e a s i b l e ( s e e T a b l e s 16 and 1 7 ) . T h e o p e r a t i o n i n v o l v e s t r a n s f e r r i n g a s o l i d - p r o p e l l a n t r o c k e t f r o m the r e f u e l - ing s p a c e c r a f t to the r e t u r n s p a c e c r a f t . T h i s t y p e of t r a n s - p o r t would i n v o l v e m e c h a n i s m s such as an o v e r h e a d e x t e n d - a b l e b o o m , o r a c a b l e w a y , along which a t r o l l e y t r a v e l s , c a r r y i n g the r o c k e t m o t o r . T h e r e t u r n s p a c e c r a f t would be l o c a t e d at a m a x i m u m d i s t a n c e of 42 ft f r o m the r e f u e l i n g s p a c e c r a f t and within an azimuth a n g l e of a p p r o x i m a t e l y 3 0 ° .
T r a n s p o r t m e c h a n i z a t i o n . F i g u r e 11 shows a g e n e r a l a r r a n g e m e n t of the r e t u r n s p a c e c r a f t with r e s p e c t to the
r e f u e l i n g s p a c e c r a f t in which the r e f u e l i n g v e h i c l e s a r e s p a c e d about the c e n t r a l l y l o c a t e d r e t u r n s p a c e c r a f t . T h e t r a n s f e r m e c h a n i s m would c o n s i s t of a c a r r i a g e which r o t a t e s in a z i - muth, an e x t e n d a b l e b o o m which i s adjustable in e l e v a t i o n , and a t r o l l e y which t r a n s p o r t s the r o c k e t m o t o r along the b o o m to the r e t u r n s p a c e c r a f t .
T h e r o c k e t - m o t o r mount on the r e t u r n s p a c e c r a f t would g r a s p the r o c k e t and a u t o m a t i c a l l y a l i g n the thrust a x i s . Connection of the i g n i t e r to the i g n i t e r c i r c u i t , as w e l l as checkout of the i g n i t e r c i r c u i t , a l s o would be a u t o m a t i c . T h e t r o l l e y would be d i s c o n n e c t e d f r o m the r o c k e t m o t o r , and it and the b o o m would r e t u r n to t h e i r o r i g i n a l p o s i t i o n s .
T V s y s t e m s . A p r e v i o u s l y p l a c e d m o d i f i e d S u r v e y o r s p a c e c r a f t with a T V c a m e r a would p r o v i d e s u r v e i l l a n c e of the t e r r a i n as w e l l as m o n i t o r i n g of landing of the r e t u r n and the r e f u e l i n g s p a c e c r a f t . In addition, it would m o n i t o r v a r i - ous r e f u e l i n g s p a c e c r a f t functions, such as c a r r i a g e o r i e n t a - tion, b o o m e x t e n s i o n , t r o l l e y t r a v e l , e t c A n additional T V c a m e r a on each of the b o o m s would s e r v e to a l i g n the b o o m with r e s p e c t to the vehicle as well as m o n i t o r b o o m e x t e n s i o n and rocket-motor emplacement.
Commands. It is estimated that a p p r o x i m a t e l y t h i r t y c o m m a n d s would b e r e q u i r e d to orient and extend the b o o m and to r e f u e l the r e t u r n s p a c e c r a f t . F o r reasons of s i m p l i c i t y ,
J . G . SMALL AND W . J . DOWNHOWER
t h e r e would be no p r o p o r t i o n a l c o m m a n d s ; a l l c o m m a n d s would be of the o n - o f f t y p e .
T e l e m e t r y . In the i n t e r e s t of s i m p l i f i c a t i o n , the m a j o r i t y of the o p e r a t i o n s a s s o c i a t e d with r e f u e l i n g would be m o n i t o r e d by T V . C e r t a i n o p e r a t i o n s such as latching and unlatching, which cannot b e m o n i t o r e d e a s i l y with T V , would be m o n i t o r e d b y t e l e m e t r y using a p p r o p r i a t e t r a n s d u c e r s and t r a n s m i t t i n g i n s t r u m e n t a t i o n .
A d v a n t a g e s . T h i s s y s t e m , by b r i d g i n g such o b s t a c l e s as c r e v i c e s and b o u l d e r s , would p e r f o r m the t r a n s p o r t func- tion independently of l o c a l d i s t u r b a n c e s and d i s c o n t i n u i t i e s in the lunar s u r f a c e b e t w e e n the r e f u e l i n g s p a c e c r a f t and the r e t u r n s p a c e c r a f t . In addition, the use of this s y s t e m would not r e q u i r e equipment o t h e r than that a l r e a d y b e i n g c a r r i e d on the r e f u e l i n g p a y l o a d .
D i s a d v a n t a g e s . T h e landing a c c u r a c y of each unit would h a v e to be contained within f a i r l y n a r r o w l i m i t s b e c a u s e of the f i x e d d i s t a n c e that a b o o m o r c a b l e w a y can b e e x t e n d e d . A l s o , it i s a s i n g l e - p u r p o s e unit with l i m i t e d usefulness f o r
o t h e r lunar manipulating o p e r a t i o n s . O n - t h e - S u r f a c e T r a n s p o r t
O n - t h e - s u r f a c e t r a n s p o r t would r e q u i r e the use of a r o v i n g t r a n s p o r t v e h i c l e with a m e c h a n i c a l a r m o r s i m i l a r manipulating d e v i c e . T h e o p e r a t i o n would i n v o l v e the use of s e v e r a l r e f u e l i n g p a y l o a d s , the t r a n s p o r t v e h i c l e , and the r e t u r n s p a c e c r a f t v e h i c l e . In the d i s c u s s i o n which f o l l o w s , a p o s s i b l e a p p r o a c h to a s s e m b l y by m e a n s of a r o v i n g v e h i c l e is g i v e n . M a n y o t h e r t y p e s of m e c h a n i z a t i o n a r e p o s s i b l e .
T h e r e f u e l i n g p a y l o a d s could b e l o c a t e d at any d i s t a n c e f r o m the r e t u r n s p a c e c r a f t . T h e d i s t a n c e would be l i m i t e d by the r o v i n g v e h i c l eT s a v a i l a b l e p o w e r and the v i e w i n g r a n g e of the T V c a m e r a . F i g u r e 12 shows the t r a n s p o r t v e h i c l e with r e s p e c t to the r e t u r n and r e f u e l i n g s p a c e c r a f t .
T r a n s p o r t v e h i c l e . T h e t r a n s p o r t v e h i c l e would b e a r e m o t e l y c o n t r o l l e d , b a t t e r y - o p e r a t e d v e h i c l e , equipped with a manipulating a r m s i m i l a r to those d e v e l o p e d by i n d u s t r y f o r
the U . S . A t o m i c E n e r g y C o m m i s s i o n and f o r g e n e r a l i n d u s t r i a l u s e . A n automatic latching d e v i c e mounted at the end of the a r m would be p o s i t i o n e d in the v i c i n i t y of the r o c k e t m o t o r when the t r a n s p o r t v e h i c l e has r e a c h e d the r e f u e l i n g p a y l o a d . A s e l f - c e n t e r i n g d e v i c e having a conic f o r m would guide the latching d e v i c e s onto the c o u p l e r on the r o c k e t m o t o r . T h e r o c k e t m o t o r would be unlatched and l i f t e d c l e a r of the r e f u e l - ing s p a c e c r a f t and t r a n s p o r t e d o v e r the s u r f a c e to the r e t u r n s p a c e c r a f t ; h e r e , the r o c k e t - m o t o r mount would g r a s p the r o c k e t and a u t o m a t i c a l l y a l i g n the thrust a x i s . Connection of the i g n i t e r to the i g n i t e r c i r c u i t , as w e l l as checkout of the i g n i t e r c i r c u i t , would be a u t o m a t i c .
T V s y s t e m s . T w o T V s y s t e m s w i l l be used: one s y s - t e m would p r o v i d e g e n e r a l s u r v e i l l a n c e of the t e r r a i n , as w e l l as m o n i t o r i n g of the landing of the r e f u e l i n g , t r a n s p o r t , and r e t u r n p a y l o a d s . In addition, this s y s t e m would m o n i t o r the r e f u e l i n g o p e r a t i o n s and a l s o v i e w the a r e a in the d i r e c t i o n of t r a n s p o r t v e h i c l e t r a v e l in o r d e r to a v o i d o b s t r u c t i o n s and o t h e r s u r f a c e d i s c o n t i n u i t i e s . T h i s c a m e r a would be l o c a t e d on a p r e v i o u s l y p l a c e d m o d i f i e d S u r v e y o r s p a c e c r a f t .
A n additional T V c a m e r a mounted on the a r m would g i v e c l o s e - u p s u r v e i l l a n c e of the t r a n s p o r t o p e r a t i o n s , such as r o c k e t - m o t o r a c q u i s i t i o n and e m p l a c e m e n t . It a l s o would s e r v e to m o n i t o r the d i r e c t i o n of v e h i c l e t r a v e l .
C o m m a n d s . I n s o f a r as p o s s i b l e , E a r t h c o m m a n d s would be held to a m i n i m u m . D i r e c t i o n of t r a v e l would b e c o n t r o l l e d by the use of suitable b e a c o n s l o c a t e d on both the r e f u e l i n g and r e t u r n s p a c e c r a f t . P r o v i s i o n would be m a d e f o r the use of o v e r r i d i n g E a r t h c o m m a n d s if, b e c a u s e of a m a l - function in the c o n t r o l s y s t e m , it should b e c o m e n e c e s s a r y to c o n t r o l the v e h i c l e by ground c o m m a n d . F o r s i m p l i c i t y , t h e r e would be no p r o p o r t i o n a l E a r t h c o m m a n d s ; a l l c o m m a n d s would be of the o n - o f f t y p e .
T e l e m e t r y . T e l e m e t r y would b e s i m i l a r in concept to that d e s c r i b e d f o r the " a b o v e - t h e - s u r f a c e " t r a n s p o r t m e c h a n - i s m .
A d v a n t a g e s . T h e r e q u i r e d landing a c c u r a c y would have c o n s i d e r a b l e latitude as the d i s t a n c e b e t w e e n the r e f u e l i n g
J . G . SMALL AND W . J . DOWNHOWER
p a y l o a d s and r e t u r n s p a c e c r a f t would be l i m i t e d only b y the c a p a c i t y of the r o v i n g v e h i c l e to t r a v e l on the lunar s u r f a c e and by the v i e w i n g r a n g e of the T V c a m e r a s . In addition, it could b e c o m e a g e n e r a l - p u r p o s e unit which could p e r f o r m such other lunar o p e r a t i o n s as r e m o t e a s s e m b l y of s t r u c t u r e s and t r a n s p o r t a t i o n of s c i e n t i f i c m i s s i o n p a c k a g e s .
D i s a d v a n t a g e s . C e r t a i n l u n a r - s u r f a c e o b s t r u c t i o n s and d i s c o n t i n u i t i e s , such as c r e v i c e s and b o u l d e r s , could i m p a i r its m o b i l i t y . One additional p a y l o a d would be r e q u i r e d in addition to the r e f u e l i n g and r e t u r n s p a c e c r a f t p a y l o a d s . T h i s additional p a y l o a d must function p r o p e r l y and maintain i t s e l f f o r the duration of the r e f u e l i n g o p e r a t i o n .
MISSION S C H E D U L E
T h e p a c i n g i t e m f o r m i s s i o n a c c o m p l i s h m e n t i s launch- ing v e h i c l e d e v e l o p m e n t and launching r a t e . T h e m a j o r e l e - m e n t s of the s p a c e c r a f t s y s t e m (manned c a p s u l e , s p a c e c r a f t bus, and p r o p u l s i o n p a y l o a d ) r e q u i r e 3 to 3 - 1 / 2 y e a r s of d e s i g n and d e v e l o p m e n t t i m e , with the e x a c t t i m e b e i n g a func- tion of the p r o c e d u r e s f o l l o w e d in s e l e c t i n g c o n t r a c t o r s and a w a r d i n g c o n t r a c t s .
T h i s schedule does not a l l o w f o r a full unmanned s y s - t e m t e s t (lunar a s s e m b l y and r e t u r n of the c o m p l e t e s y s t e m ) . If such a f u l l - s c a l e t e s t i s d e s i r e d , the number of f i r i n g s r e q u i r e d f o r the t h r e e - m a n m i s s i o n i n c r e a s e s to 15, and the d i r e c t p r o g r a m c o s t would i n c r e a s e p r o p o r t i o n a t e l y .
E x a m i n a t i o n of the landing p e r f o r m a n c e of the t r a n s i t , landing, and r e t u r n s p a c e c r a f t i n d i c a t e s that it would be p o s - s i b l e (by using the p a y l o a d c a p a b i l i t y of this s p a c e c r a f t to c a r r y r e t u r n p r o p u l s i o n ) to r e t u r n this s p a c e c r a f t f r o m the lunar s u r f a c e to the n e a r v i c i n i t y of E a r t h . Such a m i s s i o n could d e m o n s t r a t e the lunar takeoff g u i d a n c e , r e t u r n m i d - c o u r s e g u i d a n c e , and t e r m i n a l m a n e u v e r guidance in p r e p a r a - tion f o r the manned m i s s i o n .
C O S T A N D F U N D I N G R E Q U I R E M E N T S
T h e total c o s t of the p r o g r a m f o r the t h r e e - m a n l u n a r - landing m i s s i o n i s 2. 5 b i l l i o n d o l l a r s . T h i s amount includes
the c o s t of the R a n g e r and S u r v e y o r p r o j e c t s , launch v e h i c l e s , s p a c e c r a f t , c a p s u l e s , p r o p e l l a n t , lunar c o m p l e x , T V m o n i t o r - ing of the m i s s i o n , and D S I F o p e r a t i o n s . T h e amount i s b a s e d on a total of eight Saturn f i r i n g s and a s s u m e s a 50% f a i l u r e r a t e in the f i r s t s i x f i r i n g s .
The total c o s t f o r the m i n i m u m o n e - m a n l u n a r - l a n d i n g m i s s i o n i s 2. 1 b i l l i o n d o l l a r s . T h i s amount includes the i t e m s l i s t e d a b o v e f o r the t h r e e - m a n m i s s i o n and i s b a s e d on a total of s i x Saturn f i r i n g s with a 50% f a i l u r e r a t e in the f i r s t four f i r i n g s . T h e c o s t of the two Saturn launch f a c i l i t i e s i s not included.
Table 1 Three-man mission operational plan Step Spacecraft Booster Mission 1 Ranger and/or Surveyor Atlas-Agena Select landing site and gather knowledge on the site. 2 Surveyor Atlas-Centaur Establish radio "homing"beacon on-site. Establish visual monitoring capability on-site. 3 Bus + propulsion payload Saturn Cache return propulsion on lunar surface (minimum of 3 firings). 4 Bus + command module Saturn Cache return S/C for crew on lunar surface. Cache (unmanned) vernier propellant for return transit maneuver + E.S.C. package + into entry corridor, vernier propellant unit 5 ---- _____ Automatic fueling of return S/C (Step 4) with propul- sion modules landed (Step 3). Complete system checkout. 6 Bus + command module Saturn Carry three-man crew to lunar cache. (manned) + E. C. S. pack- age + mission module 7 ---- _____ Checkout of return S/C established in Step 5 in prep- aration for return to Earth. (Note: In case the system established in Step 5 is not O.K., the crew may replace selected subsystem or have return propulsion transferred to their own landed S/C for return.) 8 Bus + command module Lunar- Lunar launch, return transit and re-entry, and (manned) + E.C.S. assembled recovery of crew, package + extra return vernier propellant unit system J. G. SMALL AND W. J. DOWNHOWER
Table 2 Over-all weight summary for three-man mission Spacecraft Weight, lb At Weight A _ Prior to Completion ~, . T „MV. Prior to In Description lb f * At Main of ^ain Touch- Lunar Lunar In ection Near_Eartn At Total Llftoff Section RetrQ RetrQ down Payload TaReoff from Vicinity Re-entry 1. Propulsion S/C 10,364 30,000 30,000 29,774 10,966 10,364 7, «84 (3 S/C required, no abort propul- sion required) 2. Command module, 10,364 30,000 30,000 29,774 10,966 10,364 7,884 S/C, unmanned3' b (1 required, no abort propulsion required) 3. Command module, 10,114 30,000 29,750 29,524 10, 716 10, 114 7,638 ·"· "·· "·· S/C manned0 (1 required, abort propulsion required) 4. Return S/C, manned 10,114 .... .... 29,750 10,716 10,114 5,268 (1 required) aNo crew results in 540 lb weight reduction. ^Excess vernier propulsion to be used for return maneuver to desired re-entry corridor. cAbort propulsion-weight penalty at injection = 250 lb.
