A Case Study in NASA-DoD - The Black Vault

-118-
NOTES TO TABLE B-i
From Refs. 31 and 32:
aThis is the average power produced by the stationary array during
illumination. At an optimal sun angle, a maximum of 238 W can be produced.
Assuming a low earth orbit illumination interval of approximately
60 min, the solar array power output is 7952 Wmin corresponding
to 7952/60, or 133 W. Average power available for the orbit is 68 W,
which can be derived in the following way:
7952 W , min
7952 W 42.9 in 68 W
59.1 min + 0.75
where 59.1 min is the period of illumination and 42.9 min is the period
of occultation during low earth orbit. The factor of 0.75 is the
derived overall battery efficiency.
bBased on maximum array output of 238 W.
CThe HCMM vehicle, excluding experiments, uses 59 W during a data
pass. The SAGE vehicle uses 47 W to 79 W for the portions of the mission
discussed in the text. The remainder of the power produced during
illumination is used for battery charging.
dFifty watts could be available for an appreciable fraction of the
orbit, but the orbital average power that could be made available for
experiments and telemetry of the experimental data is no more than 40 W.
This assumes 68 W orbital average available: 12 W for attitude, 12 W
for power subsystems, and 4 W for housekeeping telemetry.
eDepth of discharge is given for the low orbit case, which is the
higher stress one because of the high frequency of occultation. Depth
of discharge for synchronous orbit can be as high as 62 percent.
fDuring prelaunch, launch, and completion of the acquisition phase,
the depth of battery discharge reaches 61.5 percent (Ref. 31, pp. 1-26).
This is a one-time condition. The AEK requires only an 8 Ah battery,
but a space-qualified 10 Ah battery was readily available. It proved
to be more practical to incorporate the standard battery rather than
to redesign the battery and charging circuits. Thus, the lower depth
of discharge values (0.14 or 0.166 rather than 0.25 as on STPSS and MNS)
reflect overdesign, not high risk, on STPSS or MMS designs.
gcalculated using depth of discharge for low earth orbit.
hIn shunt loads, based on battery Ah and temperature monitors.
From Ref. 1:
i Reference 1 (p. 6-1) lists a total nominal orbital average system
power of 500 W to 600 W, with 400 W for experiments. Page 3-5 of the
same report discusses using up to 24 panels, which would provide 1200 W
in the three-axis-stabilized configuration with sun-tracking arrays.
In the spin-stabilized configuration, however, the solar arrays are