The requirements for improved solar power system technology for DOD satellites are reported. It is shown that the technology is required in several areas including solar cells, array blanket technology, energy storage and power system operation, and regulation and control. It is further shown that as the missions become more critical to defence, military aspects such as survivability, hardening, and eventually defence must be addressed

Wise, J. F.

English

NASA Technical Reports Server

SOLAR POWER R&D FOR AIR FORCE SPACE REQUIREMENTS 
Joseph F. Wise 
AF Wright Aeronautical Laboratories 
Wright-Patterson AFB, Ohio 
INTRODUCTION 
The requirements f o r  improved so lar  power system technology f o r  DOD 
s a t e l l i t e s  have been s t a t e d  i n  several  s tudies  and conference papers ( r e f .  1). 
These summarize requirements up t o  lOOKW by t h e  year 2000 plus  need t o  g rea t ly  
reduce t h e  power system weight and improve l i fe t ime.  
several  areas including s o l a r  c e l l s ,  a r ray  blanket technology, energy storage 
and power system operation, regulat ion and control .  
more c r i t i c a l  t o  Defense, we must a l so  address m i l i t a r y  aspects such as 
surv ivabi l i ty ,  hardening and eventually,  defense. 
Technology i s  required i n  
A s  t h e  missions become 
REQUIRENENTS 
The mission areas requir ing power system technology advances are shown 
i n  Figure 1. The t r a d i t i o n a l  ro l e s  of communication, survei l lance and naviga- 
t i o n  w i l l  continue and new r o l e s  are assigned i n  areas of weapons. The 
t r a d i t i o n a l  missions, however, w i l l  require  more power as follows. Comunica- 
t i o n s  w i l l  increase i n  volume as  t h e  mi l i t a ry  increase r e l i ance  on s a t e l l i t e  
systems. 
communicate with smaller ground u n i t s .  Surveil lance missions power require- 
ments increase i n  order t o  de tec t  a i r c r a f t ,  ground forces  and naval u n i t s  i n  
both grea te r  d e t a i l  and t o  handle more t r a f f i c .  
expanded c a p a b i l i t i e s  a r e  space based radar and deep space survei l lance 
missions using inf ra red  detect ion.  Some of these  missions also w i l l  operate i n  
very high rad ia t ion  l e v e l s  i n  intermediate a l t i t u d e  o r b i t s  and w i l l  require  
hardening t o  a va r i e ty  of weapon e f f e c t s  such as nuclear and laser. Figure 2 
shows a project ion of these  requirements. 
W e  w i l l  a l so  need more power t o  counter jamming t h r e a t s  and a l so  
Early candidates f o r  these  
TECHNOLOGY PROGRAM 
The A i r  Force solarpower system technology developments can be  divided 
i n t o  th ree  areas:  s o l a r  c e l l  development, hardening technology, and power 
system development. I w i l l  b r i e f l y  discuss  these  th ree  areas:  
A s  you are all aware, we have been working on three basic  so la r  c e l l  
t h r u s t s ,  s i l i c o n ,  gallium arsenide and multibandgap technology. The s i l i c o n  
work, summarized i n  Figure 3, i s  aimed a t  increasing t h e  end of l i f e  e f f ic iency  
as w e l l  as reducing weight, hardening t o  laser weapon e f f e c t s ,  and reducing 
po ten t i a l  cos ts .  Main t h r u s t s  at present are t h e  v e r i t i c a l  junct ion so la r  c e l l  
and t h e  development of t h e  cold crucible  CZ techniques f o r  growing high pu r i ty  
s t a r t i n g  material at reduced costs .  Both the  Space Division and NASA Lewis a re  
j o i n t l y  supporting t h i s  technology program. The main object ives  are high 
5 
https://ntrs.nasa.gov/search.jsp?R=19810009011 2020-03-21T08:58:28+00:00Z
ef f ic iency ,  17% BOL and m a x i m u m  EOL power system, a f t e r  5 ~ 1 0 ~ ~ / c m ~  1MEV elec- 
t r o n  equivalent dose t o  provide technology f o r  t h e  mid a l t i t u d e  o r b i t  missions. 
The G a A s  program, shown i n  Figure 4,  which L t  Masloski w i l l  l a te r  discuss ,  
addresses higher eff ic iency,  demonstration of f l i g h t  readiness and developnent 
of lower cost  t echnica l  approaches using web technology and growth on lower 
cos t  subs t ra tes .  
The multibandgap c e l l  technology addresses demonstration of concept 
f e a s i b i l i t y  and i s  aiming f o r  22 t o  25% ef f ic iency  with an AlGaAs/GaAs mono- 
l y t h i c  c e l l  approach. 
chemical vapor deposit ion.  
We are a l s o  in t e re s t ed  i n  t h e  p o s s i b i l i t y  of bandgap t a i l o r i n g  t o  optimize t h e  
s ing le  junct ion so la r  c e l l  i n  hopes of reaching b e t t e r  than 20% eff ic iency.  
The area of so l a r  power.,system hardening t o  laser r ad ia t ion  e f f e c t s  i s  b r i e f l y  
summarized i n  Figure 5. 
temperature capab i l i t y  of a l l  a r ray  components by use of welded interconnects,  
i n t eg ra l  coverglass and high temperature adhesive, and (2 )  minimize energy 
absorption using r e f l e c t i o n  and f i l t e r i n g  or avoidance. Most e f f o r t s  i n  t h e  
pas t  dealt with s i l i c o n  c e l l  technology but  as t h e  GaAs c e l l  technology 
matures, we need t o  harden it a lso .  Therefore, t h e  advanced c e l l  vu lne rab i l i t y  
and hardening, i n t e g r a l  covers and high temperature contact axeas address both 
G a A s  and s i l i con .  W e  are a l s o  re-evaluating concentration concepts as a means 
t o  increase system hardness. Most schemes t o  da te  involve a reduction i n  
e f f ic iency  and increased weight t o  achieve hardness. 
Growth methods include both l i q u i d  phase epi taxy and 
D r  Rahi l ly  w i l l  d iscuss  t h i s  area i n  a later paper. 
This  a rea  dea ls  with two t h r u s t s  - (1) increase t h e  
Power system technology i s  under development and planned by both t h e  A i r  
Force and NASA. 
programs shown i n  Figure 6 are i n  being o r  planned. 
elopment program i s  bas i ca l ly  t o  define t h e  technology needed t o  achieve power 
system weight and l i f e  goals and t h e  AD program scheduled f o r  FY 81 i s  t o  
develop t h e  component technology needed f o r  these  advanced systems. 
opments needed a re  l ightweight hardened blanket technology, using t h i n  c e l l s  
and subs t ra tes ,  high temperature technology i n  covers, adhesives and in t e r -  
connections, e t c .  Much use  can be made of some ea r ly  NASAtechnology, espec- 
i a l l y  t h e  t h i n  c e l l  work. 
o r b i t s  including between 400NMI and 10,000NMT. 
Lockheed programs t o  date  t o  requi re  withstanding 4.8 x 1016cm2/electron 
equivalent and maximize EOL ef f ic iency .  A t  these dose l eve l s ,  approaches such 
as annealing (GaAs  and S i )  should be invest igated.  
w i l l  be done as pa r t  of our basic  inves t iga t ions  s tud ies  with such individuals  
as D r .  Drevinski and Henry D'Angeles of RADC and i n  c lose  cooperation with t h e  
various NASA centers .  
management, energy s torage and waste heat u t i l i z a t i o n  and r e j ec t ion  are a l s o  
planned foT development i n  t h i s  program. Component technology development i s  
planned f o r  t h e  next 5 years with a f l i g h t  type program after t h a t .  
To achieve t h e  capab i l i t y  needed i n  t h e  l a te  80 's  t o  2000, t h e  
The e a r l y  exploratory dev- 
Key devel- 
Newer satell i tes a re  planned over a wide spectrum of 
These have been shown i n  t h e  
Ef fo r t s  along these  l i n e s  
Power system work i n  areas of regulat ion,  control ,  
SUMMARY 
The next two decades w i l l  see an evolution i n  satell i te usage t o  support 
more c r i t i c a l  m i l i t a r y  missions which w i l l  require  higher end of l i f e  
eff ic iency,  lower weight and volume, autonomous operation and hardening t o  a 
va r i e ty  of po ten t i a l  t h r e a t s .  W e  have i n  being, programs t o  provide f o r  t h i s  
6 
improved technology. 
standpoint a re  shown i n  Figure 7. Many technology improvements a re  needed t o  
achieve these goals and they are  further complicated by hardening requirements. 
It i s  hoped t h a t  t he  r e su l t s  of the three day meeting w i l l  assist us i n  
developing and demonstrating technology needed i n  the  next two decades. 
The goals of these technology programs from a system 
REFERENCES 
1. 
IECEC, 18-22 August 1980. 
E. Tom Mahefkey, Future Space Power - The DOD Perspective, CP# 809016, 15th 
Military Space System Functions 
SPACE MISSION AREAS 
PR I NC I PAL 
INTELLIGEKE COLLECTION & TREATY MONITORIN( 
STRATEGIC FORCE MANAGEMENT 
o THEATER & NAVAL FORCE MANAGEMENT 
ACTIVE DEFENSE 
- OF FRIENDLY SPACE ASSETS 
- AGAINST SPACE-BASED THREAT 
- AGAINST TERRESTRIAL THREAT 7 
SUP PORT . SPACE LOGISTICS 
o SATELLITE CONTROL 
o PASSIVE DEFENSE 
3 
SPACE SYSTEM FUWTIONS - TIME PERIOD 
OBSERVATION - NOW 
COMMUNICATIONS 
INFO RELAY - NOW 
e CMDlCOMROL 
NAVl  GATlON - NOW 
WEAPONRY - FUTURE? 
. CURRENT SPACE SYSTEMS CAN BE REGARDED AS c31 SYSTEMS 
SPACE WEAPONRY WILL FORCE NEW COMMITMENTS & PERCEPTIONS 
FIGURE 1 
7 
100 
2 
1 
0.1 
Power R e q u i r e ~ e ~ s  
1980 - 2000 
FIGURE 2 
SILIC9N CELL PROGRAMS 
-- UNIT TITLE I FY 80 I FY .$l I FY 82 j FY 83 I FY 84 I FY 85 1 
iSILICON CELL OPT I !I1 ZAT I ON 
I N  l l ~ ~ l l S l  I VAI M T  I OW 
ANA1 Y S I S  
FIGURE 3 
8 
I I I -V PROGR/?PlS 
',!ORK UNIT T ITLE I FY 80 I FY 81 I FY 82 I FY 83 I FY (34 I FY 85 1 
_--. 
t1ESP-GAAs-PHASE 2 
GAAS PANEL 
GAAS SHEET DEVELOPF.1ENT 
LO!/ C X T  GAAS CELLS 
MJLT IR4idDGAD 
I'lU LT I B.?WDGAP 
CASCADE CELL 
(RI). 
(RTI) 
ADV, DEV, 
I 
 
FIGURE 4 
H,?!?DE?I  NG PRCIFRAY!S 
W R K  UfiIT T ITLE I FY 80 I FY 81 i FY 82 J FY33 1 FY 84 J FY 85 t 
ESB OPT IN IZ4TI cli4 
HIGH TEMP. ADHESIVES t 1 
I 
VUL/HA,BDEtl I NG ADV , CELL 1 
HIGH TEMP. CONTACT 
I1ETALL I ZAT I ON 
'IULTI -THREAT HARDENIflG 
FIGURE 5 
9 
SYSTEMS PROGRAMS 
- \KIRK (INIT TITLE I FY 60 I FY 81 1 FY 82 1 FY 83 I N84 FY85 1 
HI VOLTAGE HARDEN, 
POWER SYS, 
H I  VOLTAGE H I  PONE!? 
SYSTEM 
EXPLORATORY C OM CENT RAT OR 
STUDY 
CONCENTRATOR CELL/PAMEL 
' DEVEL, 
SPACECRAFT POYER 
PROCESS 1116 
I- -- 
FIGURE 6 
SOLAR POWER SYSTEMS 
HEDRB 50 WHR/b GEO 
NCH 2 15 WHR/LB 6EO 
1970 1980 1990 2000 
70 
50 
30 
10 
FIGURE 7 
10 


Solar power R and D for Air Force space requirements

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