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6 Power Technology of Lunar Lander
6.2 Status of Power Supply Technology Development
The United States and the former the Soviet Union had implemented many lunar
soft-landing exploration missions. Based on the analysis of lunar landing missions
in different countries, the combination of “solar array + battery” was the option
in the power system design for most of these missions except fuel battery in early
Apollo missions. Solar array converted light energy into electricity to power the
probes, while excess energy was converted into chemical energy for storage and
the chemical energy was converted into electrical power for joint power supply if
necessary.
In terms of space solar cells, there were several types such as silicon (Si)
cells, single-junction gallium arsenide (GaAs/Ge) cells, and triple junction gallium
arsenide (GaInP/GaAs/Ge) cells [2]. Up to date, silicon solar cell was the most
popular one. Along with development of fundamental technologies, the photoelectric conversion efficiency of solar cell has been gradually increased from 14% (silicon
solar cell) to 30% (triple junction gallium arsenide cells). With successful research &
development and space applications of gallium arsenide solar cell, gallium arsenide
solar cell with higher photoelectric conversion efficiency will be gradually applied
in the future.
There were several types of battery such as nickel-cadmium (Ni/Cd) battery,
nickel-hydroxide (Ni/H2) battery and lithium-ion (Li-ion) battery [3]. The specific
energy of the battery had been gradually increased from 50 W•h/kg (nickel-cadmium
battery) to 150 W•h/kg (lithium-ion battery), while the specific energy of hydrogennickel battery was in between. Lithium-ion battery had the advantages of high specific
energy, low heat consumption, and low self-discharge [4]. Now lithium-ion battery
had been gradually applied to deep space exploration.
The Surveyor series missions were robotic the lunar landers launched by the
United States. There were total 7 missions launched, of which 5 were successful.
The spacecraft buses of these 7 the lunar landers were exactly the same, whose
power system was a combination of solar array and zinc-silver battery with one fully
adjustable main bus and one unregulated main bus. The area of solar panels was
0.83 m
2 , and power output was 81 W. The battery pack connected by 14 units could
output power 3375Wh.
Euro2000 was a lunar landing exploration mission planned by Europe. It consisted
of the lunar lander and a circumlunar spacecraft. It was originally planned to be
landed on lunar south pole. The power system also used a combination of solar
cell and battery. The solar array of the lunar lander consisted of a fixed plate and a
deployable plate. The area of fixed plate was 2.5 m
2 , and the area of deployable plate
was 2.0 m
2 . The solar cells were GaAs solar cells with power density of 207 W/m
2 .
In addition, there was also a group of 16 kg NiH 2 battery packs with a specific energy
of 60 W•h/kg which could provide 300 W power supply.
Apollo manned spacecraft consisted of service module, command module and
lunar module. After launched, the spacecraft was inserted into LTO. When the
spacecraft approached the Moon, the lunar module was separated. The operation
6 Power Technology of Lunar Lander
6.2 Status of Power Supply Technology Development
The United States and the former the Soviet Union had implemented many lunar
soft-landing exploration missions. Based on the analysis of lunar landing missions
in different countries, the combination of “solar array + battery” was the option
in the power system design for most of these missions except fuel battery in early
Apollo missions. Solar array converted light energy into electricity to power the
probes, while excess energy was converted into chemical energy for storage and
the chemical energy was converted into electrical power for joint power supply if
necessary.
In terms of space solar cells, there were several types such as silicon (Si)
cells, single-junction gallium arsenide (GaAs/Ge) cells, and triple junction gallium
arsenide (GaInP/GaAs/Ge) cells [2]. Up to date, silicon solar cell was the most
popular one. Along with development of fundamental technologies, the photoelectric conversion efficiency of solar cell has been gradually increased from 14% (silicon
solar cell) to 30% (triple junction gallium arsenide cells). With successful research &
development and space applications of gallium arsenide solar cell, gallium arsenide
solar cell with higher photoelectric conversion efficiency will be gradually applied
in the future.
There were several types of battery such as nickel-cadmium (Ni/Cd) battery,
nickel-hydroxide (Ni/H2) battery and lithium-ion (Li-ion) battery [3]. The specific
energy of the battery had been gradually increased from 50 W•h/kg (nickel-cadmium
battery) to 150 W•h/kg (lithium-ion battery), while the specific energy of hydrogennickel battery was in between. Lithium-ion battery had the advantages of high specific
energy, low heat consumption, and low self-discharge [4]. Now lithium-ion battery
had been gradually applied to deep space exploration.
The Surveyor series missions were robotic the lunar landers launched by the
United States. There were total 7 missions launched, of which 5 were successful.
The spacecraft buses of these 7 the lunar landers were exactly the same, whose
power system was a combination of solar array and zinc-silver battery with one fully
adjustable main bus and one unregulated main bus. The area of solar panels was
0.83 m
2 , and power output was 81 W. The battery pack connected by 14 units could
output power 3375Wh.
Euro2000 was a lunar landing exploration mission planned by Europe. It consisted
of the lunar lander and a circumlunar spacecraft. It was originally planned to be
landed on lunar south pole. The power system also used a combination of solar
cell and battery. The solar array of the lunar lander consisted of a fixed plate and a
deployable plate. The area of fixed plate was 2.5 m
2 , and the area of deployable plate
was 2.0 m
2 . The solar cells were GaAs solar cells with power density of 207 W/m
2 .
In addition, there was also a group of 16 kg NiH 2 battery packs with a specific energy
of 60 W•h/kg which could provide 300 W power supply.
Apollo manned spacecraft consisted of service module, command module and
lunar module. After launched, the spacecraft was inserted into LTO. When the
spacecraft approached the Moon, the lunar module was separated. The operation