ESA Document - Emits - ESA

s
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 170 of 422
Redundancies at different level can be foreseen to cope with diverse contingency situations,
depending on the criticality of the failure and required reaction time.
The thermal control design shall be capable of operating nominally after a single failure at any
point of the TCS architecture. To do so, the safest and standard approach is to have primary and
secondary loops fully redundant (in cold redundancy). An alternative to a full and cold
redundancy is a possible local reconfiguration (local bypass from nominal to redundant) if
adequately completed by redundancy at unit level. Such an approach could eventually lead to a
complementary system up to a certain level as long as each can guarantee a nominal mode. This
flexibility could prevent a degraded/survival mode after a second failure. Redundancy at unit
level for critical units (pumps for example) and adequate provision of spare for maintenance are
foreseen depending on the redundancy level.
habitat
logistic
MAV ERC
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water loop
logistic
liquid
two phase loop
inhabited section
Control
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Heat rej ection
system
Figure 3-32: Thermal bus (primary and secondary loop)
The choice of a distributed or a centralized thermal control system depends on the system
architecture and on the location/distribution of the dissipating elements. A distributed TCS offers
thermal hardware simplicity (local thermal control) at the expense of a heavier configuration at
system level. The requirements of modularity and flexibility do not call for a distributed
architecture but for a centralized system completed by a judicious use of local thermal
configuration where advantageous. A modular system is therefore proposed with parallel
primary loops to pick up and convey the loads toward a central thermal bus.
3.3.3.4.2 Acquisition system
Its function is to remove locally a certain quantity of energy (heat) and the technology of the
acquisition is adapted to the type of elements to control:
• high dissipative components are mounted on cold plates
• medium to low dissipative components are controlled via forced convection and mounted
on baseplates thermally connected to the structure (hull or platform)
• integrated systems (within racks) are controlled via dedicated fluid loops (gas or liquid)
• air is sucked in by fans and canalized in a heat exchanger (air/liquid) and dehumidifying
system.