ESA Document - Emits - ESA

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Figure 4-39: Power required to maintain temperature
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 288 of 422
The insulating system is assumed to provide an equivalent thermal conductivity of 0.13W/m 2 /K
(15 cm of foam). Therefore, maintaining over one sol an internal wall above dew point (14C for
75% humidity, mean sink –60C + 20C margin accounting to heat losses through inertia) would
require a power density of 11.3W/m 2 .
Two systems are proposed:
• a network of heaters homogeneously distributed on the internal shell corresponding to a
installed power of 728W (assuming the SHM as a cylinder 3.6 x 5.7 m length). Two
equivalent circuits (main and redundant) are foreseen, each piloted by a control unit. For
safety, each circuit will be equipped with over temperature thermostats to protect against
a failed-on heater switch.
• a network of coils / heat pipes mounted on the internal shell to transfer / homogenize the
rejected heat from main loop (about 2.7 kW)
A strategy for heater power saving can be implemented with a pre-heating before the night
(using the higher activity dissipation during the day through the fluid heat storage capability).
Local PCM (where worst heat leaks are located) can also efficiently complete the system. An
optimised heat management could request little electrical power to maintain the requirements.
For safety reasons, however, a certain provision of installed power shall be designed (about
728W). No particular trade-off has been done on the landing location assuming no specific
landing (polar site or winter period with high latitude).
4.3.4.3.5 Overview