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5 Thermal Control Technology of Lunar Lander
The lifetime of Chinese Chang’E-3 lunar lander was one year, when the probe
would go through about 13 lunar day/night circles. The Chang’E-3 lunar lander took
use of Variable Conductance Heat Pipes (VCHPs) to transfer the electronics waste
heat to the radiators toward space on the top of the lunar lander during the lunar
day, and VCHPs could be “shut off” during the lunar night. The lunar lander was
equipped with Radioisotope Heat Units (RHUs) to produce heat energy, which was
translated into the electronic cabins by Gravity Driven ammonia two-phase fluid
loops, to maintain survival temperature during the lunar night. A new type of heat
shield was used to protect the lander structure from the high temperature environment
of the descent engine during landing.
5.3 Thermal Technical Characteristics
5.3.1 Design Constraints
In order to keep equipment working normally in orbit and on lunar surface, the lunar
lander must adapt to and even take advantage of the different environmental factors to
control the heat exchange between the internal equipment and the external environments. Compared with the earth orbit spacecraft and circumlunar spacecraft, besides
similar environment such as the space vacuum, the background heat sink, the heat
input and the microgravity, the lunar lander would go through unique environments
such as the lunar surface heat radiation, the extreme low temperature at lunar night,
the lunar surface gravity except and lunar dust.
Besides the natural environments, special constraints of lunar soft-landing
including the high temperature and the plume impingement of the descent engine,
and the uncertain orientation of the lunar lander before landing on moon should be
adapted by design of thermal control subsystem.
1. Natural Environmental Constraints
1) Space vacuum
After the lunar lander was more than 100 km away from the Earth, the space pressure
was gradually reduced to less than 10
−2 Pa, about 10
−6 Pa at 500 km, 10
−10 Pa at
2500 km, and less than 10
−11 Pa beyond 3000 km. The atmosphere on lunar surface
is very thin where the atmospheric density is about 14 orders of magnitude smaller
than that of the Earth, and the pressure is about 10
−6 Pa to 10
−10 Pa [13]. Therefore,
the lunar lander usually worked under high vacuum conditions. The pressure on lunar
surface is basically the same as the Earth orbit with a height of 500 km to 2500 km. The
material deflation and the thermal insulation performance of multilayer insulations
that should be considered in thermal design were the same as that of an Earth orbit
spacecraft.
The only heat exchange between the lunar lander and external environment under
vacuum conditions was radiation. For non-hermetic structures, the heat exchange
5 Thermal Control Technology of Lunar Lander
The lifetime of Chinese Chang’E-3 lunar lander was one year, when the probe
would go through about 13 lunar day/night circles. The Chang’E-3 lunar lander took
use of Variable Conductance Heat Pipes (VCHPs) to transfer the electronics waste
heat to the radiators toward space on the top of the lunar lander during the lunar
day, and VCHPs could be “shut off” during the lunar night. The lunar lander was
equipped with Radioisotope Heat Units (RHUs) to produce heat energy, which was
translated into the electronic cabins by Gravity Driven ammonia two-phase fluid
loops, to maintain survival temperature during the lunar night. A new type of heat
shield was used to protect the lander structure from the high temperature environment
of the descent engine during landing.
5.3 Thermal Technical Characteristics
5.3.1 Design Constraints
In order to keep equipment working normally in orbit and on lunar surface, the lunar
lander must adapt to and even take advantage of the different environmental factors to
control the heat exchange between the internal equipment and the external environments. Compared with the earth orbit spacecraft and circumlunar spacecraft, besides
similar environment such as the space vacuum, the background heat sink, the heat
input and the microgravity, the lunar lander would go through unique environments
such as the lunar surface heat radiation, the extreme low temperature at lunar night,
the lunar surface gravity except and lunar dust.
Besides the natural environments, special constraints of lunar soft-landing
including the high temperature and the plume impingement of the descent engine,
and the uncertain orientation of the lunar lander before landing on moon should be
adapted by design of thermal control subsystem.
1. Natural Environmental Constraints
1) Space vacuum
After the lunar lander was more than 100 km away from the Earth, the space pressure
was gradually reduced to less than 10
−2 Pa, about 10
−6 Pa at 500 km, 10
−10 Pa at
2500 km, and less than 10
−11 Pa beyond 3000 km. The atmosphere on lunar surface
is very thin where the atmospheric density is about 14 orders of magnitude smaller
than that of the Earth, and the pressure is about 10
−6 Pa to 10
−10 Pa [13]. Therefore,
the lunar lander usually worked under high vacuum conditions. The pressure on lunar
surface is basically the same as the Earth orbit with a height of 500 km to 2500 km. The
material deflation and the thermal insulation performance of multilayer insulations
that should be considered in thermal design were the same as that of an Earth orbit
spacecraft.
The only heat exchange between the lunar lander and external environment under
vacuum conditions was radiation. For non-hermetic structures, the heat exchange