A Case Study in NASA-DoD - The Black Vault

Table B-I
POWER SYSTEM COMPARISONS
Characteristic
lAE (32) STPSS (2) "'(6)
Voltage level 28 t4 V de at bus 28 ±5 V dc at bus 28 ±7 V dc m
±2% to experiments optional 28 V ±0.5 V
to experiments (±1.82)
Array
Average power during
i
No array on base module
illumination 133 W a 1200 W max
Average power over
low-altitude orbit 68 W a 500-600 W nominal 1200 W max, bus rating n
Material N/P silicon N/P silicon
Resistance 1 to 3 ohm-cm 2 ohm-cm
Size of solar cells 2 x 2 x 0.03 cm 2 x 4 - 0.036 cm
Efficiency 11% - 10%
Cover glass thickness 6 mils 6 mils
Total dimensions
of array Each panel consists of Each panel consists of
2 strings x 82 cells 2 strings of 96 cells
in series x 5 in
in series by 3 in
parallel x 6 panels on parallel (50 W/panel-EOL
each of two non-sun- max) up to 24 panels
tracking paddles
Total area of array 23.2 sq ft 6 sq ft/panel
Array power/ft 2 EOL 10.3 W/ft 2 8.3 W/ft 2
Total weight of array
and support structure 19.6 lb 132 lb
Spacecraft power consumption,
excluding
c
experiments - 50 to 80 W c 92-197 W J 350 W
Power available for
experiments 40 to 50 Wd - 400 W nominal 850 W max
Kind of battery NiCd NiCd NiCd
Battery rating 10 Ah 3 - 20 Ahk 2 x 20 Ah baseline or up
to 3 - 20 Ah or 1 to 3
50 Ah °
Battery coefficient,
Ah/lb 0.49 0.38 0.40
Number of batteries 1 3 1 to 3
Depth of discharge e 14% (BOL); 25% 25% low earth orbit; 50 %P
16.6% (EOL)f synchronous orbit
Power available
during eclipse g 46 Whr 420 Whr 280 Whr for 2 - 20 Ah
battery or 1050 Whr for
3 x 50 Ah battery q
Weight of battery,
power conditioning
and distribution 51.1 lb 253.) lb 334 lb q
Battery charging
method Across both solar Separate control for One power regulating unit
arrays in parallel each battery for all batteriesr
h
Dissipation of
excess power "Shunt resistors ' "Shunt modules" Peak power tracker, s excess
power is left on the array,
there is a 2 to 5C rise in
array temperature