A Case Study in NASA-DoD - The Black Vault

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sunlight. These surfaces include the backside of the solar array, the
louver radiator surface (AEM), the thermal control trim radiator, the
shunt dissipater panel, solar array and antenna appendages, and the
S-band antenna.
Radiators for dissipating heat generated inside the spacecraft
are used on both the AEM and the STPSS. In the case of the STPSS
(which has no louvers) the control of component temperatures within
the spacecraft is achieved with a combination of radiators, second
surface mirrors, and thermostatically controlled heaters. On the AEM,
component temperature control is achieved with louvers and thermalcontrol
trim radiators. The baseline design radiator for the AEM
spacecraft radiator is sized to satisfy the HCMM mission requirements
and is painted white. The radiator's properties can be adjusted by
paint stripes to attain the desired trim.
Since most of the elements of the AEM thermal control subsystem
have been flight-proven on previously designed Boeing spacecraft, they
should be considered at least state of the art if not off-the-shelf.
The same holds true for the TRW-proposed STPSS design.
COMPARATIVE EVALUATION OF THE STPSS AND MMS SPACECRAFT
To date, contracts have not been awarded for the design, development,
or production of either the MMS or the STPSS. Consequently, the
information available for making a comparative evaluation of the MMS
and STPSS is less detailed than for the AEM-STPSS evaluation. However,
based on the information from GSFC, Aerospace Corporation, and TRW,
thermal control subsystem concepts are sufficiently well defined that
a reasonable comparative technical evaluation can be made.
The same two differences between the AEM and STPSS are indicated
for the STPSS and MMS (Table G-1). The MMS spacecraft uses two louvers
on each of three modules: power module, ACS module, and the C&DH module.
As previously stated, the STPSS relies on radiators, second surface
mirrors, and thermostatically controlled heaters for maintaining the
spacecraft structure and components within specified temperature limits.
Louvers are generally considered to be more expensive than heaters.
However, personal contact with a thermal control system engineer at