ESA Document - Emits - ESA

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HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 175 of 422
radiator from spacecraft). The independence and flexibility in terms of heat rejection for any
spacecraft attitude, gained by mounting a cylindrical radiator may not justify its mass penalty.
Using a dedicated and inhabited area for a particular type of logistic (tanks, pumps, machinery)
will ease the thermal control architecture and globally decrease the power and mass budget.
• Possible decrease of this compartment temperature (10C to 20C lower than the habited
module) if pressurisation is done with an inert gas,
• Will improve the performance of the thermal accommodation of stored cryogenics fluids
• Easier integration of a biphasic system possibly using different working fluids (less
restrictions on the safety).
Maintenance visits, if necessary, should be possible and not raise excessive constraints (use of
portable oxygen supply). An adequate redundancy of these internal units will be foreseen to
minimise interventions.
Figure 3-34: Secondary loop and radiators
There are different ways to control a fluid loop radiator:
• bypass regulation controlling the flow of the coolant and reducing the heat extracted
from the fluid; a minimum heat must be available to prevent freezing.
• regenerative regulation that controls the temperature at the inlet of the radiator via a
bypass valve that diverts the flow to the heat exchanger as a function of the radiator
outlet temperature (advantage: the fluid differential is small => low heat load is required
to prevent freezing; and almost constant mass flow can be maintained)
• mechanical or electrically actuated systems (louvres, pointing motorization, electroemissive
devices) that control the radiator view to space and/or limits the radiative
exchange to it.
Design selection
A restricted area dedicated to thermally sensible logistic is implemented. This zone will host a
biphasic system, retained as the secondary loop. This will include:
• biphasic heat exchangers, connected to the primary bus (water loop),
• biphasic cold plates for high-to-medium dissipative logistic,