Results of the DoD/ERDA (now Department of Energy) Space Power Study completed in October 1977 are presented. The major new thrust of Air Force Advanced Technology Plans center on the development of military solar power systems which will extend capabilities to the 10 - 50 KW sub e power range for new classes of missions while maintaining technology applicability to the 0.5 - 10 KW sub e present mission class. The status of FY78 efforts for Project 682J (Air Force Space Power Advanced Development Program) are reported. Project 682J is divided into the following tasks: (1) high efficiency solar panel; (2) nickel-hydrogen battery; (3) gallium arsenide solar concentrator hardness study; and (4) new-start nuclear dynamic power system applications/integration study

Barthelemy, R. R.

Mahefkey, E. T.

Massie, L. D.

English

NASA Technical Reports Server

MILITARY NEEDS FOR ORBITAL POWER 
L. D. Massie, R. R. Bartheleqy and E. T. Mahefkey 
Air Force Aero Propulsion Laboratory 
Wright-Patterson AFB 
SUMMARY 
Results of the DOD/ERDA (now Department of Energy) Space Power Study 
completed in October 1977 
future DOD space missions. Consequently, the major new thrusts of Air Force 
Advanced Technology Plans center on the development of military solar power 
systems which will extend capabilities to the 10-50 KWe power range for new 
classes of missions while maintaining technology applicability to the .5 
to 10 We present mission class. 
systems level, and integrated power system level efforts. These efforts 
will emphasize performance, reliability, autonomy and survivability. 
show a trend toward higher power levels for 
Plans call for technology level, sub- 
INTRODUCTION 
The objective of the Air Force Space Power Advanced Development Program 
(Project 6825) is to develop and demonstrate space power system technology 
to meet increasing power needs of Air Force Satellites in the post-1978 time 
period. 
Past 6825 efforts which have successfully transitioned to operational 
applications include the Flexible Rolled-up Solar Array (FRUSA), Hardened 
Array Solar Power System (HASPS), and the 2 KWe Long Life Battery (LLB). 
The 1.5 KWe FRUSA was successfully flown on Space Test Program Vehicle 71-2. 
The HASPS has been selected for meeting the 7.3 KWe prime power requirement 
of the SIRE (Space Infrared Experiment) ~80-2 mission. The 2 We LLB effort 
provided the baseline technology from which the 14.3 watt- hrs/Kg 
(6.5 watt hrs/Lb) FLTSATCOM battery evolved. 
The present FY78 efforts in Project 682J include the multiple phase 
Task 682504 High Efficiency Solar Panel (HESP) , Task 682505 Nickel-Hydrogen 
Battery (Ni/H2), a recently completed Task 682~06 Gallium Arsenide Solar 
Concentrator Hardness Study (Concentrator) and a February 1978 Task 682507 
new-start Nuclear Dynamic Power System Applications/Integration Study. 
In view of findings and conclusions of the DOD/ERDA Space Power Study 
Report, the Technology Program Plan for Space Power Advanced Development 
was recently modified to address the projected trend toward higher power 
levels and an enhanced threat environment for military satellites. The new 
planning initiatives include a Task 682508 High Voltage High Power (HVHP) 
93 
https://ntrs.nasa.gov/search.jsp?R=19790001956 2020-03-22T02:27:05+00:00Z
System; Task 682509 High Energy Density Rechargeable Battery (HEDRB) ; Task 
682~10 Fault Tolerant Power System (FTPS); Task 682~11 Thermal Energy 
Storage Subsystem (TESS) and Task 682512 Cascaded Solar Cell Development 
Program. 
STATUS OF PRESENT EFFORTS 
Task 682J04.- HESP Phase I has been completed with the demonstration of 
silicon solar cells having efficiencies of 14 percent. 
been initiated with the objective of demonstrating 16 percent efficient 
silicon cells and improved experimental quantities of 16 percent efficient 
gallium arsenide cells. Under HESP Phase 11, recent silicon and radiation- 
hardened gallium arsenide developmental cells delivered to AFAPL have 
demonstrated efficiencies as high as 15.5 and 17 percent respectively. 
Radiation resistance of gallium arsenide cells has been improved to the point 
where some cells are superior to high output silicon cells at 1-MeV electron 
fluence levels as high as 5 x 1015 e/cm2 as shown in Figure 1. 
Figure 2, temperature coefficients of gallium arsenide cells are clearly 
superior to those of silicon, making gallium arsenide cells attractive for 
Concentrating Photovoltaic Power System Concepts. Gallium arsenide cells 
have favorable vslues of solar absorptance (a = .78) as compared to silicon 
(a = .85, smooth surface cells; a = .94, textured surface cells). Both HESP 
textured silicon cells and gallium arsenide cells being flown as experiments 
on the NTS-I1 (Navigation Technology Satellite) are performing well after 
more than 223 days in orbit. Both cell types are to be included in the 
forthcoming DIABLO HAWK underground nuclear test. 
HESP Phase I1 has 
As shown in 
Task 682505,- In the area of rechargeable batteries, Ni/H2 cell design 
has been completed and the initial group of twenty-six (26) test cells 
are being manufactured for evaluation. In addition NASA Marshall Space 
Flight Center has provided funds for two Ni/H2 cells for independent test 
and evaluation. Twenty-four (24) cells will be built in the spring of 1978 
for an Industry Dispersal Program under which independent industry tests 
will be conducted. The Naval Research Laboratory has expressed interest in 
utilizing the Air Force developed Ni/H2 cells on NTS-I11 scheduled for 
launch in 1981. 
Force and Navy pertaining to the NTS-I11 cells is anticipated during the 
second quarter of 1978. 
eight, 35-ampere-hour cells would be required for meeting NTS-I11 require- 
ments. 
performance battery, integrated, and utilized as the NTS-I11 energy storage 
subsystem. 
already been conducted on a SAMSO Special Projects Vehicle. The advanced 
development program Ni/H2 cells currently being fabricated 
to be vastly superior to these early vintage cells already flown in space 
in terms of cycle life, depth of discharge and energy density, 
is a schematic of the 50-ampere-hr Ni/H2 cell design. 
photograph of the 21-cell Ni/H2 battery flown on the SAMSO/SP Vehicle. Table 
I is a preliminary weight breakdown for a 1.15-KW-Hr Ni/H;2 Battery based upon 
Negotiation of a Memorandum of Agreement between the Air 
It is presently estimated that a total of forty- 
Sixteen of the forty-eight cells would be assembled into a high 
A successful orbital test of early vintage Ni/H2 cells ha5 
are expected 
Figure 3 
Figure 4 is a 
94 
a Hughes Aircraft Company conceptual design. 
Task 682~06.- A gallium arsenide cell concentrating photovoltaic concept 
recently studied under a Contract with Rockwell International is considered 
to be a promising technology option for advanced laser threat hardness. The 
concept utilizes Cassegrainian optics in conjunction with a Winston collector 
to focus sunlight on a single high efficiency gallium arsenide cell at a con- 
centration ratio of about 500' to 1. Cell operating temperature is maintained 
at approximately 12OoC by an integral, distributed heat pipe radiator. 
final study report (AFAPL-TR-78-30) pertaining to this concept will be 
distributed in June 1978. 
The 
Task 682~07.- The recently initiated Nuclear Dynamic Power System Appli- 
cations/Integration Study will provide the analysis, design, and spaceflight 
integration considerations needed to assure a successful space demonstration 
of a 1.3-KWe radioisotope-fueled dynamic power system. An important part of 
this study will deal with analyzing future special purpose Air Force missions 
which will benefit from this technology. In addition, the program will 
provide for (a) analysis of requirements for integration and orbital 
operations, (b) evaluation of nuclear and laser hardness, and (c) develop 
preparatory information needed for the assessment of safety and environmental 
impacts. The overall program is to assure Air Force a2plicability of the DOE 
Nuclear Dynamic Power System Technology. 
FUTURE PLANS - APPROVED PROGRAM 
Future space power advanced development plans, within the approved 
(a) Gallium Arsenide Solar Panel work which is directed toward panel 
program, are primarily extensions of present efforts and include the follow- 
ing: 
design, fabrication and spaceflight qualification; (b) HESP Phases I11 and IV 
which are for advanced cell production demonstration, flight experiment 
design, experiment spaceflight qualification and orbital. flight test; (c) 
completion of single-cell Ni/H2 efforts through orbital flight test and 
implementation of a Common Pressure Vessel Ni/H2 program; (d) implementation 
of a Concentrating Photovoltaic Power System hardware build and evaluation 
effort; and (e) completion of the Nuclear Power Supply Study in support of 
space payload AFAPL 601 - Nuclear Dynamic Power System Flight Experiment. 
Figure 5 is a Milestone Chart which encompasses present efforts and 
future plans within the approved program. The chart shows anticipated 
technology advances and when they are expected to occur, based upon present 
budget allocations. 
cell assemblies are.expected in 1980. 
through a 20,000-cell flight test is expected by 1983. Conclusive demon- 
stration of single-cell Ni/H2 batteries through flight test on NTS-3 should 
occur in 1981. Flight test of a Ihclear Dynamic Power System is scheduled 
for 1983. 
For example, 16 percent efficient space-qualified s o l a r  
Demonstration of advanced solar cells 
95 
Overal l  results of t hese  e f f o r t s ,  compared t o  conventional technology, 
w i l l  double t h e  end-of-l ife power per  u n i t  area of s o l a r  a r r ays ,  more than  
double t h e  useable  energy dens i ty  of spacec ra f t  energy s torage  subsystems, 
and make new power technology opt ions such as Concentrating Photovol ta ic  
and Nuclear Dynamic Power Systems ava i l ab le  f o r  s p e c i a l  purpose DOD 
s a t e l l i t e  app l i ca t ions .  
RESULTS OF DOD/ERDA SPACE POWER STUDY 
A DOD/ERDA Space Power Study w a s  conducted during t h e  per iod  from 
February 1976 t o  May 1977. 
of t h i s  s tudy w a s  i s sued  i n  October 1977. The ob jec t ives  of  t h e  s tudy were 
t o  i d e n t i f y  f u t u r e  DOD space power requirements and recommend appropr ia te  
nuclear  and non-nuclear technology development programs needed t o  ensure 
t h a t  f u t u r e  power requirements can be m e t .  Study p a r t i c i p a n t s  included 
SAMSO, AFAPL, ERDA ( D O E ) ,  LASL, and indus t ry .  Study t a s k s  included 
( a )  future requirements through t h e  year  2000, ( b )  nuc lear  and non-nuclear 
technology p ro jec t ions  through t h e  year  2000, ( c )  matching power systems 
and requirements,  ( d )  spacecraf t  po in t  designs f o r  one navigat ion sa te l l i t e  
and two surveillance satel l i tes ,  and ( e )  recommendations. 
A prel iminary r epor t  summarizing t h e  results 
Results of  t h e  s tudy i n d i c a t e  t h a t  t h e  major i ty  of f u t u r e  s i n g l e  space- 
c r a f t  power requirements w i l l  be  i n  the  .5 t o  1 0  KWe power range. 
t h e  s tudy  a l s o  i d e n t i f i e d  a s i g n i f i c a n t  number of  p o t e n t i a l  missions with 
power requirements i n  t h e  10  t o  100 KWe range and beyond as shown i n  Figure 6 .  
Most of  t h e  high power requirements tend t o  be i n  the  su rve i l l ance ,  space 
defense systems, ECM r e s i s t a n t  communications, and of fens ive  systems areas. 
Requirements ex is t  f o r  e l e c t r i c a l ,  thermal,  and pulse  power wi th  some 
p o t e n t i a l  missions r equ i r ing  a combination of a l l  t h r e e  power forms. 
However, 
Table I1 presen t s  t h e  genera l  f ind ings  of t h e  s tudy dea l ing  wi th  
matching of  power systems t o  mission power requirements.  The approved 
model and extended mission model scenar ios  cover t h e  .5 t o  100 KWe and 
beyond power regime. 
choice i n  t h e  .5 t o  5 KWe range. Within t h i s  range t h e r e  a r e  s p e c i a l  
purpose i so tope  appl ica t ions  f o r  missions where p rec i se  a t t i t u d e  con t ro l  and 
s t a b i l i z a t i o n ,  extreme hardness,  and maneuvering c a p a b i l i t i e s  are needed. 
I n  t h e  5 t o  25 KWe range, s o l a r  a r r ay /ba t t e ry  power systems a r e  t h e  f i r s t  
choice.  There are no i so tope  app l i ca t ions  i n  t h i s  range because of t h e  
high c o s t  of t h e  rad io iso tope  fuel .  
o r  a r e a c t o r ,  i f  it were ava i l ab le ,  could fu l f i l l  needs i n  t h e  25 t o  50 KWe 
range. 
beyond 50 KWe;with s o l a r  a r r ay /ba t t e ry  systems being f e a s i b l e  i n  t h i s  
range 
Solar  a r r ay /ba t t e ry  power systems a r e  t h e  number one 
E i t h e r  s o l a r  a r r ay /ba t t e ry  power systems 
A r e a c t o r  would be t h e  number one choice f o r  power requirements 
96 
FUTURE PLANS-LABORATORY RECOMMENDED PROGRAM 
Future poten t ia l  mission requirements as i d e n t i f i e d  i n  the  DOD/ERDA 
Space Power Study have been factored i n t o  fu ture  technology program planning 
f o r  space power advanced development. The Technology Program Plan w a s  
recent ly  revised t o  r e f l e c t  need f o r  t h e  following new i n i t i a t i v e s :  
Task 682508 - High Voltage High Power System 
Task 682509 - High Energy Density Rechargeable Battery 
Task 682510 - Fault  Tolerant Power System 
Task 682511 - Thermal Energy Storage Subsystem 
Task 682512 - Cascaded Solar Cells 
Task 6 8 2 ~ 0 8  i s  t o  develop a s t rong technology base f o r  a DOD Power Module 
(10 t o  50 KWe) with a counter-measures capabi l i ty;  Task 682509 w i l l  develop 
a rechargeable electrochemical b a t t e r y  capable of 66 w a t t -  hrs/Kg (30 w a t t  - 
hrs/Lb) f o r  low ear th  o r b i t  ( L E O )  and 110 w a t t  -hrs/Kg (50 w a t t  -hrs/Lb) 
f o r  geostationary (GEO) o r b i t  appl icat ions;  Task 682510 w i l l  demonstrate 
an autonomous power system where a l l  elements of the  system are  control led 
by l o c a l  microprocessors i n  conjunction with a power system microcomputer; 
Task 682511 w i l l  develop a 110 watt-hr/Kg (50 wat t -hr /Lb)  thermal energy 
storage subsystem f o r  Vuilleumier (VM) cryocoolers f o r  survei l lance 
applications;  Task 682512 w i l l  develop 25-35 percent e f f i c i e n t  monolithic 
cascaded multiple bandgap so lar  c e l l s .  
Anticipated r e s u l t s  of the  AFAPL Research and Exploratory Development 
Programs during t h e  next 2 t o  5 years were considered i n  developing the 
revised Technology Program Plan f o r  Advanced Development. 
Figure 7 i s  a Milestone chart  which per ta ins  t o  the laboratory- 
recommended new i n i t i a t i v e  program plans.  The chart  shows the expected 
technology advances and when they are  expected t o  occur i f  the programs 
are  approved and budgeted. Overall r e s u l t s  of these e f f o r t s ,  compared t o  
conventional technology, would t r i p l e  t h e  end-of-life power per u n i t  
area of s o l a r  arrays;  more than quadruple the  useable energy densi ty  
of spacecraft  energy storage subsystems; and provide non-nuclear, autonomous, 
survivable power system options t o  f u l f i l l  p o t e n t i a l  high power advanced 
mission needs. Figure 8 shows t h e  overa l l  A i r  Force pas t ,  present ,  and 
fu ture  advanced development program response t o  Space Power Technology. 
Implementation of t h e  various tasks  under the  project  r e s u l t s  i n  technology 
options which a r e  mission enhancing and mission enabling. Examples of 
mission enhancing tasks  a r e  the  N i / H 2  Battery and s o l a r  c e l l  eff ic iency 
improvements which t r a n s i t i o n  d i r e c t l y  t o  system appl icat ion upon 
qual i f ica t ion  and production demonstration. 
System (HASPS) i s  an example of a mission enabling task  i n  t h a t  t h e  
f e a s i b i l i t y  of the  SIRE ~ 8 0 - 2  mission would be questionable without the 
HASPS technology option. Also, the  recommended H W  task i s  mission enabling; 
t h a t  i s ,  unless the  technology i s  developed, c e r t a i n  future  high power 
missions cannot be undertaken. 
The Hardened Array Solar Power 
97 
CONCLUDING REMARKS 
a. 
range is valid, based upon the probable needs for advanced surveillance, 
ECM resistant communications, space-based radar, and space defense missions. 
The trend toward military space power requirements in the 10 - 100 KWe 
b. Performance enhancements in solar  cell efficiency and battery energy 
density and lifetime are of major importance to spacecraft designers. 
e .  Design to performance, survivability and reliability/autonomy 
mandates are important military satellite power system requirements. 
d. Advanced solar arrays and batteries will continue to be the predominant 
power system choice for future Air Force satellites in the foreseeable 
future. Nuclear power system options should be maintained for specialized 
missions requiring very high levels of hardness and orbit predictability. 
98 
REFERENCES 
1. 
2. 
3. 
4. 
5. 
6 .  
7. 
8. 
AFAPL-TR-77-36 - "High Efficiency Solar  Panel (HESP)"; Spectrolab, Inc . , 
JdY 1977. 
AFAPL-TR-77-80 - "GaAs Concentrator Photovoltaic Power System Feasibility 
Investigation"; Hughes Aircraft Company, December 1977. 
AFAPL-TR-78-30 - "Gallium Arsenide Solar Concentrator Hardness Study"; 
Rockwell International Corporation, March 1978. 
AFAPL-TR-76-100 - "Investigation of GaAs Solar Cell Potential Performance 
and Cost"; AF Aero Propulsion Laboratory, February 1977. 
AFAPL-TR-77-90 - "Failure Mechanisms in Nickel-Hydrogen Cells"; Hughes 
Aircraft Company, December 1977. 
AFAPL-TR-77-89 - "Nickel-Hydrogen Battery Advanced Development Program"; 
Hughes Aircraft Company, December 1977. 
Personal Communications with Lt Cecil R. Stuerke, AFAPL/POE-2, WPAFB, OH 
45433. Air Force ;"oca1 point for GaAs Solar Cell advanced development, 
Personal Communications with M r .  Don R. Warnock, AFAPL/POE-1, WPAFB, OH 
45433. 
development. 
Air Force focal point for Nickel-Hydrogen Cell advanced 
99 
24 
24 
48 
24 
TABLE I - 50 AMPERE HOUR N I / H ~  BATTERY WEIGHT ESTINATE 
lIEcl !ma 
(KG) (LBs) 
CELLS Fd 1,29 30,96 68,25 
THERMAL SHUHTS 61 ,027 ,65 1,43 
HEAT PIPES 61 ,052 2,50 5,51 
RADIATORS a ,086 2,06 4,511 
BATTERY CELL HDW, 1,27 2.80 
5.45 12,Ol ELECTRICAL 8 PROTECTIVE -- 
* ** 42,89 94,55 
USEABLE ENERGY DENSITY = C Vc Nc DQR = 26,s WATT e HRS (l2,2 ~ T T  * &SI 
W KG LB 
* 
** 
NOMINAL CELL VOLTAGE = 1,2 VOLTS 
DEPTH OF DISCHARGE = 80% 
TABLE I 1  - MATCHING POWER SYSTEMS TO MISSION REQUIREMENTS 
SCENAR I o : ,5 - 100 KW, 8 EEYONJI POWER RANGE 
0 SOLAR # 1 IN THE ,5  - 5 KW, RANGE; SPECIAL PURPOSE ISOTOPE 
APPLICATIONS IN THIS RANGE 
0 SOLAR # 1 IN THE 5 - 25 KH, RANGE; No ISOTOPE APPLICATIONS 
IN THIS RANGE 
0 25 - 50 KW, - EITHER SOLAR OR REACTOR (IF AVAILABLE) IN 
THIS RANGE 
0 IF AVAILABLE, REACTOR 8 1 IN THE 50 - 100 WE RANGE (AND BEYOND); 
SOLAR FEASIBLE 
100 
I I 1 1  I I I I I  I I I I I I I I ~  I I I I f l l l l  I I I 1 1 1 1 1  
E 100- - 
FIGURE 1. IMPROVED RADIATION TOLERANCE 
OF RECENT GaAs SOLAR CELLS 
I I I 1 1 1 1 1 1  I I I 1 1 1 1 1 1  I I I 1 1 1 , 1 1  I I I I l l l L  
FIGURE 2. TEMPERATURE SENSITIVITY OF GaAs AND Si SOLAR CELLS 
101 
m m 
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Is: a, a, 
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om 
V
4
 
102 
FIGURE 4. PHOTOGRAPH OF AIR FORCE NICKELHYDROGEN BATTERY 
SPACE EXPERIMENT 
103 
682J07/NUCLEAR 
FY79 FY81 FY82 
4 
FY83 GOALS FY80 
1 
TASK/SHORT TITLE 
I 
FY78 
2 
, 1 . 16% HARDENED SOLAR 
2. 16% HARDENED SOLAR 
3 CELLS 
PANEL 
I I 13. FLT EXP.-AFAPL 501 
4. SINGLE CELL Ni-Hz 
9 WH/LB LEO I 1 6  WH/LB GEO 
15. NTS-3 FLIGHT -1. CPV Ni-Hz 
1 2  WH/LB LEO 
20 WH/LB GEO 
7. N1'-H LEO FLT. 
EXP-~FAPL 503 
8. HARDNESS STUDY 
9. SYSTEM DESIGN 
10. FLIGHT EXP. 
11. INTEGRATION STUDY 
1 I 1 
FIGURE 5. MILESTONE CHART FOR ADVANCED SPACE POWER SUPPLY TECHNOLOGY 
(SAMSO/AFAPL APPROVED) 
pTA POTENTIALLY THERMAL B W E R  
I] ELECTRICAL POWER 
I980 81 82 
IO2 n 84 
35 a 
- 
96 1996 
BEYOND 
FIGURE 6. MAXIMUM SINGLE-SPACECRAFT POWER REQUIREMENTS BY YEAR 
104 
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106 


Military needs for orbital power

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