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6 Power Technology of Lunar Lander
6.3.3 Mission Characteristics and Analysis
There were three special features of power system of the lunar lander including flight
profile and illumination, power supply requirement, lightweight and miniaturization
requirements [7].
1. Flight Profile and Illumination
The flight profile had a great impact on the power system including the time from
launch to deployment and orientation to the Sun of the solar array, time and attitude
of orbit changes, operation modes of spacecraft platform and load in all flight phase,
and etc. The flight orbit would affect the time of illumination and in shadow, which
would determine the scale of the solar array and the battery pack. The flight attitude
would affect incident angle of sunlight on the solar array and blocked area of the
solar array by the spacecraft. All above factors would affect power output of the solar
array.
Before landed on lunar surface, the lunar lander would pass flight phases such as
launch, LTO, orbit changes on circumlunar orbit and powered descent. During such
phases, the power load varied greatly. The long-term load was the platform load with
low power. But the transient load was very large such as powered descent when the
main engine was firing frequently. Therefore, the adjusting capability of the power
system should be sufficient to ensure stable and reliable power supply of the lunar
lander [6].
After the lunar lander was landed on lunar surface, the battery packs would be
heavily involved in charging and discharging according to operation modes. During
lunar night without illumination, the energy requirement of the lunar lander could
not be supported by the battery packs. It was necessary to power off all instruments
before lunar night and power on autonomously to recover to normal operation mode
when the lunar day was coming.
The illumination of the lunar lander on lunar surface was very complex. For
example, the illumination is repeated with a period of 29.53 days on the Sinus Iridum
(45.6°N, 18.2°W). In one lunar daytime, the local solar elevation/azimuth angle is
shown in Fig. 6.1.
2. Power Supply Requirements
(1) Power supply requirement on different status. Because the lunar lander was
on different status in different flight phases, the power requirement for
different status were different. For example, there was a need for charging
and discharging between the lander and the rover of the Chang’E-3. The joint
power supply control strategy and special control circuit should be designed
to ensure the reliability and margin of power supply in different phases.
(2) Power requirement for different phases of the mission. The lunar lander would
pass different flight phases such as launch, LTO, orbit change, circumlunar
orbit, powered descent, initialization and operation on lunar surface with
different operation modes. The power supply requirement for each phase were
quite different. Therefore, specific design was necessary.
6 Power Technology of Lunar Lander
6.3.3 Mission Characteristics and Analysis
There were three special features of power system of the lunar lander including flight
profile and illumination, power supply requirement, lightweight and miniaturization
requirements [7].
1. Flight Profile and Illumination
The flight profile had a great impact on the power system including the time from
launch to deployment and orientation to the Sun of the solar array, time and attitude
of orbit changes, operation modes of spacecraft platform and load in all flight phase,
and etc. The flight orbit would affect the time of illumination and in shadow, which
would determine the scale of the solar array and the battery pack. The flight attitude
would affect incident angle of sunlight on the solar array and blocked area of the
solar array by the spacecraft. All above factors would affect power output of the solar
array.
Before landed on lunar surface, the lunar lander would pass flight phases such as
launch, LTO, orbit changes on circumlunar orbit and powered descent. During such
phases, the power load varied greatly. The long-term load was the platform load with
low power. But the transient load was very large such as powered descent when the
main engine was firing frequently. Therefore, the adjusting capability of the power
system should be sufficient to ensure stable and reliable power supply of the lunar
lander [6].
After the lunar lander was landed on lunar surface, the battery packs would be
heavily involved in charging and discharging according to operation modes. During
lunar night without illumination, the energy requirement of the lunar lander could
not be supported by the battery packs. It was necessary to power off all instruments
before lunar night and power on autonomously to recover to normal operation mode
when the lunar day was coming.
The illumination of the lunar lander on lunar surface was very complex. For
example, the illumination is repeated with a period of 29.53 days on the Sinus Iridum
(45.6°N, 18.2°W). In one lunar daytime, the local solar elevation/azimuth angle is
shown in Fig. 6.1.
2. Power Supply Requirements
(1) Power supply requirement on different status. Because the lunar lander was
on different status in different flight phases, the power requirement for
different status were different. For example, there was a need for charging
and discharging between the lander and the rover of the Chang’E-3. The joint
power supply control strategy and special control circuit should be designed
to ensure the reliability and margin of power supply in different phases.
(2) Power requirement for different phases of the mission. The lunar lander would
pass different flight phases such as launch, LTO, orbit change, circumlunar
orbit, powered descent, initialization and operation on lunar surface with
different operation modes. The power supply requirement for each phase were
quite different. Therefore, specific design was necessary.