6.4 Design Methodology
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6.4.4 Analysis of Space Environmental Effects
The power system of the lunar lander should pass various special environments
including Earth’s orbit, LTO, circumlunar orbit and lunar surface [9].
1. Analysis of Space Radiation Effect
For the power supply system, the effects of space radiation included two aspects.
On the one hand, the solar array installed outside the module directly exposed to the
space environment. On the other hand, the power supply control device and battery
packs installed in the module were affect too.
(1) External equipment
There were two main effects on solar arrays. One was the total dose effect of ionization, and the other was displacement damage. The major result was the degradation
of the electrical performance of solar cells, which was reflected in the drop of voltage
and current. The germanium-doped cover glass on triple-junction gallium arsenide
solar cell (GaInP2/GaAs/Ge) was used to reduce the impact of radiation effects. In
design of solar cell circuit, the power loss should be considered to ensure that the
lunar lander load requirement was met at the end of life.
(2) Internal equipment
The structural materials of the power controller and the battery pack were made
of aluminum, and the non-plastic-sealed components such as resistors, capacitors,
operational amplifiers, diodes, bipolar transistors, and relays were all insensitive to
radiation. The major components sensitive to radiation were mono-stable integrated
circuits. The major consideration was the design of total dose effect protection and
single event latch-up protection in the design of radiation-resistance of the power
system.
2. Analysis of Space Thermal Environment Impact
The solar array was installed outside the module, while the lithium-ion battery packs
and power controller were in the module. The temperature outside the module was
affected by lunar surface environment [10], and the temperature range might be
relatively large as −180 °C ~+120 °C. The internal temperature of the module was
managed by the thermal control system to ensure the normal operation temperature
of the power controller and the battery.
(1) Solar array
Extremely high and low temperature environments might increase the risk of
damaging the material of the solar array including single cell, cover glass, backsheet
glue, wires, and solar cell array solder joints. The components and parts of the solar
arrays such as wire-to-connectors, wires, isolation diodes, and grounding resistor
should be verified by pertinent specific tests. The forward conduction performance
and reverse cut-off performance of the diode, and the electrical performance of the
triple-junction gallium arsenide solar cell should be verified by high-low temperature
cycling test and low-temperature storage test in air.
211
6.4.4 Analysis of Space Environmental Effects
The power system of the lunar lander should pass various special environments
including Earth’s orbit, LTO, circumlunar orbit and lunar surface [9].
1. Analysis of Space Radiation Effect
For the power supply system, the effects of space radiation included two aspects.
On the one hand, the solar array installed outside the module directly exposed to the
space environment. On the other hand, the power supply control device and battery
packs installed in the module were affect too.
(1) External equipment
There were two main effects on solar arrays. One was the total dose effect of ionization, and the other was displacement damage. The major result was the degradation
of the electrical performance of solar cells, which was reflected in the drop of voltage
and current. The germanium-doped cover glass on triple-junction gallium arsenide
solar cell (GaInP2/GaAs/Ge) was used to reduce the impact of radiation effects. In
design of solar cell circuit, the power loss should be considered to ensure that the
lunar lander load requirement was met at the end of life.
(2) Internal equipment
The structural materials of the power controller and the battery pack were made
of aluminum, and the non-plastic-sealed components such as resistors, capacitors,
operational amplifiers, diodes, bipolar transistors, and relays were all insensitive to
radiation. The major components sensitive to radiation were mono-stable integrated
circuits. The major consideration was the design of total dose effect protection and
single event latch-up protection in the design of radiation-resistance of the power
system.
2. Analysis of Space Thermal Environment Impact
The solar array was installed outside the module, while the lithium-ion battery packs
and power controller were in the module. The temperature outside the module was
affected by lunar surface environment [10], and the temperature range might be
relatively large as −180 °C ~+120 °C. The internal temperature of the module was
managed by the thermal control system to ensure the normal operation temperature
of the power controller and the battery.
(1) Solar array
Extremely high and low temperature environments might increase the risk of
damaging the material of the solar array including single cell, cover glass, backsheet
glue, wires, and solar cell array solder joints. The components and parts of the solar
arrays such as wire-to-connectors, wires, isolation diodes, and grounding resistor
should be verified by pertinent specific tests. The forward conduction performance
and reverse cut-off performance of the diode, and the electrical performance of the
triple-junction gallium arsenide solar cell should be verified by high-low temperature
cycling test and low-temperature storage test in air.