5.3 Thermal Technical Characteristics
155
between internal structure and instrument of the lunar lander was heat conduction and radiation, where there was no atmospheric convection heat transfer on the
ground which would cause difficulty for heat exchange. But it was suitable to achieve
excellent heat insulation performance of multilayer insulation components.
The adverse effects such as surface evaporation, cold welding, and non-uniform
temperature on the surface brought by space high vacuum environment should be
paid careful attention to in the solution and material selection.
2) Low temperature
Except Sun, Earth, Moon and other planets, the space faced by the lunar lander
is equivalent to an absolute black body with a temperature of 4 K, and the space
radiation is about 10
−5 W/m
2 outside the Earth’s atmosphere and on lunar surface
[14, 15]. Because other stars are too far away, the heat fluxes received by the lunar
lander were from solar radiant heat flow, Earth radiation and its reflection heat flow,
lunar surface radiation and its reflection heat flow.
During operation on lunar surface, the energy reflection between the lunar lander
and lunar surface should be considered. In other phases, due to the relatively small
size of the lunar lander, it was generally believed that the heat radiated from the lunar
lander surface was totally absorbed by the space.
3) Solar radiation
Solar radiation is the major heat source for the lunar lander. Due to the fact that the
distance between Earth and Moon is small relative to the distance between Sun and
Earth, the distance between Sun and Earth together with the distance between Sun
and Moon is equal to one Astronomical Unit. Therefore, the solar radiation intensity
for the lunar lander was the same as that of the Earth orbit spacecraft during all flight
phases, i.e., one solar constant (S, the mean value is 1367 W/m
2 ) at average distance
between Sun and Earth. The solar constant was corrected according to the change
of distance between Sun and Earth in different seasons, the maximum was about
1414 W/m
2 for the winter solstice (Perihelion) and the minimum was 1322 W/m
2
for the summer solstice (Aphelion).
The spectral distribution of solar radiation is shown in Fig. 5.2, which is basically
consistent with the absolute blackbody radiation spectrum of 5760 K [14].
4) Lunar Albedo
Part of the solar radiation received by the Moon is absorbed, and the other part is
reflected. The part that is reflected off is called the reflection heat flow. According to
observations on the Earth, the reflectivity of solar radiation on lunar surface is related
to local chemical and mineral composition, particle size, and material density, which
could be referred to Chap. 2 for specific values.
For the lunar lander who orbits the Earth sometime, the Earth’s reflection heat flow
shall be considered during thermal analysis. Earth’s reflection heat flux varies with
the earth’s surface morphology, seasons, geographic latitudes, and orbital inclination.
The factors are complex. However, due to high altitude and fast velocity of the lunar
155
between internal structure and instrument of the lunar lander was heat conduction and radiation, where there was no atmospheric convection heat transfer on the
ground which would cause difficulty for heat exchange. But it was suitable to achieve
excellent heat insulation performance of multilayer insulation components.
The adverse effects such as surface evaporation, cold welding, and non-uniform
temperature on the surface brought by space high vacuum environment should be
paid careful attention to in the solution and material selection.
2) Low temperature
Except Sun, Earth, Moon and other planets, the space faced by the lunar lander
is equivalent to an absolute black body with a temperature of 4 K, and the space
radiation is about 10
−5 W/m
2 outside the Earth’s atmosphere and on lunar surface
[14, 15]. Because other stars are too far away, the heat fluxes received by the lunar
lander were from solar radiant heat flow, Earth radiation and its reflection heat flow,
lunar surface radiation and its reflection heat flow.
During operation on lunar surface, the energy reflection between the lunar lander
and lunar surface should be considered. In other phases, due to the relatively small
size of the lunar lander, it was generally believed that the heat radiated from the lunar
lander surface was totally absorbed by the space.
3) Solar radiation
Solar radiation is the major heat source for the lunar lander. Due to the fact that the
distance between Earth and Moon is small relative to the distance between Sun and
Earth, the distance between Sun and Earth together with the distance between Sun
and Moon is equal to one Astronomical Unit. Therefore, the solar radiation intensity
for the lunar lander was the same as that of the Earth orbit spacecraft during all flight
phases, i.e., one solar constant (S, the mean value is 1367 W/m
2 ) at average distance
between Sun and Earth. The solar constant was corrected according to the change
of distance between Sun and Earth in different seasons, the maximum was about
1414 W/m
2 for the winter solstice (Perihelion) and the minimum was 1322 W/m
2
for the summer solstice (Aphelion).
The spectral distribution of solar radiation is shown in Fig. 5.2, which is basically
consistent with the absolute blackbody radiation spectrum of 5760 K [14].
4) Lunar Albedo
Part of the solar radiation received by the Moon is absorbed, and the other part is
reflected. The part that is reflected off is called the reflection heat flow. According to
observations on the Earth, the reflectivity of solar radiation on lunar surface is related
to local chemical and mineral composition, particle size, and material density, which
could be referred to Chap. 2 for specific values.
For the lunar lander who orbits the Earth sometime, the Earth’s reflection heat flow
shall be considered during thermal analysis. Earth’s reflection heat flux varies with
the earth’s surface morphology, seasons, geographic latitudes, and orbital inclination.
The factors are complex. However, due to high altitude and fast velocity of the lunar