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5 Thermal Control Technology of Lunar Lander
Generally, the attitude of the lunar lander was solar oriented during LTO and
circumlunar phase. In LTO, the external heat flow was a stable solar radiation heat
flow, while it was periodic alternation of solar radiation, lunar infrared radiation and
reflected heat flow in circumlunar phase. After the lunar lander was landed on lunar
surface, the solar radiation, lunar infrared radiation and reflected heat flow varied
with solar elevation. However, due to long lunar daytime (approximate 14 days), the
change rate of solar elevation was relatively small (average 0.5°/h on lunar equator
and about 0.3°/h at 45° latitude). Therefore, it could be assumed that the temperature
of the lunar lander could reach balance at each time. Because the time of LOI and
landing process was shorter (from several minutes to about ten minutes), the external
heat flow was transient.
The simulation method of external heat flow should be the methods suitable for
transient conditions such as solar simulator and contact type method after comprehensive consideration of current status of simulation technology of external heat flow,
variation of external heat flow of the lunar lander and determination of test conditions (focuses are verification in circumlunar phase, landing process and operation
on lunar surface). According to actual external heat flow of different surfaces of the
lunar lander, infrared heaters (infrared lamp array or far infrared cage) could be used
to simulate the external heat flux on the surface of small change, but the simulation method of external heat flux should be optimized according to actual working
conditions to minimize error.
The infrared radiation heat flow might also be the largest on the surfaces of the
lunar lander toward Sun on lunar surface. The combination of two external heat flow
caused a large external heat flow above 1200 W/m
2 on some surfaces of the lunar
lander. When infrared heaters (infrared lamp array or far infrared cage) were used
to simulate external heat flow on such surfaces, the proportion of those simulators’
area was large. When the temperature was low, the temperature would be higher
because external heat flow was large than actual condition. In order to solve this
problem, simulators with different area ratios could be used to simulate external heat
flow before and after landing respectively, or a mobile infrared heater could be used
which was removed at low temperature conditions.
4. Test Conditions
The mission profile of the lunar lander was complex. The different launch windows
would also cause great change of environment conditions. Uncertainty of landing
attitude resulted in numerous theoretical combinations of landing conditions on lunar
surface. Therefore, it was not feasible to simulate all of actual conditions of the lunar
lander in ground tests and only a limited number of typical conditions could be
selected for testing. The typical test conditions for thermal balance tests of the lunar
lander are as follows:
(1) The high temperature condition and low temperature condition should cover
the whole process of the mission, i.e., the highest temperature condition and
the lowest temperature condition should cover all phases of the mission. Since
lunar dust during landing and after landing might have great effect on thermal
5 Thermal Control Technology of Lunar Lander
Generally, the attitude of the lunar lander was solar oriented during LTO and
circumlunar phase. In LTO, the external heat flow was a stable solar radiation heat
flow, while it was periodic alternation of solar radiation, lunar infrared radiation and
reflected heat flow in circumlunar phase. After the lunar lander was landed on lunar
surface, the solar radiation, lunar infrared radiation and reflected heat flow varied
with solar elevation. However, due to long lunar daytime (approximate 14 days), the
change rate of solar elevation was relatively small (average 0.5°/h on lunar equator
and about 0.3°/h at 45° latitude). Therefore, it could be assumed that the temperature
of the lunar lander could reach balance at each time. Because the time of LOI and
landing process was shorter (from several minutes to about ten minutes), the external
heat flow was transient.
The simulation method of external heat flow should be the methods suitable for
transient conditions such as solar simulator and contact type method after comprehensive consideration of current status of simulation technology of external heat flow,
variation of external heat flow of the lunar lander and determination of test conditions (focuses are verification in circumlunar phase, landing process and operation
on lunar surface). According to actual external heat flow of different surfaces of the
lunar lander, infrared heaters (infrared lamp array or far infrared cage) could be used
to simulate the external heat flux on the surface of small change, but the simulation method of external heat flux should be optimized according to actual working
conditions to minimize error.
The infrared radiation heat flow might also be the largest on the surfaces of the
lunar lander toward Sun on lunar surface. The combination of two external heat flow
caused a large external heat flow above 1200 W/m
2 on some surfaces of the lunar
lander. When infrared heaters (infrared lamp array or far infrared cage) were used
to simulate external heat flow on such surfaces, the proportion of those simulators’
area was large. When the temperature was low, the temperature would be higher
because external heat flow was large than actual condition. In order to solve this
problem, simulators with different area ratios could be used to simulate external heat
flow before and after landing respectively, or a mobile infrared heater could be used
which was removed at low temperature conditions.
4. Test Conditions
The mission profile of the lunar lander was complex. The different launch windows
would also cause great change of environment conditions. Uncertainty of landing
attitude resulted in numerous theoretical combinations of landing conditions on lunar
surface. Therefore, it was not feasible to simulate all of actual conditions of the lunar
lander in ground tests and only a limited number of typical conditions could be
selected for testing. The typical test conditions for thermal balance tests of the lunar
lander are as follows:
(1) The high temperature condition and low temperature condition should cover
the whole process of the mission, i.e., the highest temperature condition and
the lowest temperature condition should cover all phases of the mission. Since
lunar dust during landing and after landing might have great effect on thermal