6.4 Design Methodology
213
6.4.5 Energy Balance Analysis
Energy balance analysis could determine whether the lunar lander energy was
balanced during a specific period of time. When the power balance of the lunar
lander power was calculated, there were many factors to be considered including
illumination condition, load requirement, solar array and battery of power system,
charging and discharging efficiency and etc. The analysis process and calculation
method were basically the same as that of Earth orbit spacecraft.
In LTO, the lunar lander was powered mainly by the solar array. During orbit
changes and phases in Moon shadow, the lunar lander was powered mainly by the
battery pack. At the same time, the long-term power load of the lunar lander was small
and short-term high power loads occurred mainly in orbit changes. In addition, the
interval between orbit changes was usually several orbital periods during circumlunar
phase. For the lunar lander, a multi-turn energy balance method was suitable, which
allowed the battery of the lunar lander to be discharged at a greater depth and fully
charged in subsequent several orbital periods to achieve energy balance. Such design
could reduce the total power output of the solar array so as to reduce the area and
mass of the solar array, and make it possible to select small-capacity battery pack.
If the energy balance was achieved in one orbital period, the power output of the
solar array and the capacity of the battery should be greatly increased. At the same
time, in cruise process of circumlunar orbit, the power output of the solar array was
excessive and a great many shunting was required, which was not optimized design.
The power load of the lunar lander changed dramatically during the mission profile
and the flight process was complex including the launch [11], LTO, 100 km circular
lunar orbit, 100 km × 15 km circumlunar orbit, powered descent, initialization on
lunar surface, operation on lunar surface and lunar eclipse on orbit. The change of
external heat flux was complex during the mission profile and the temperature range
of the battery pack varied greatly, as well as occlusion of the solar array of the lunar
lander was complex during operation on lunar surface.
When energy balance of the lunar lander was calculated, comprehensive consideration should be conducted including the system power load conditions, illumination
conditions, occlusion of solar array and battery support capabilities under a wide
temperature range for each flight phases, as well as various unexpected conditions.
Due to wide range of battery operation temperature on orbit, in order to verify the
discharge capacity of the lithium-ion battery pack under different working conditions,
the same batch of single cells of the lander lithium-ion battery was verified by experiments for different discharge conditions including LOI, circumlunar orbit, powered
descent and lunar eclipse. At the same time, in order to examine the discharge capacity
of the battery pack, the flight hardware of the battery pack was tested according to
the orbital power and temperature conditions to ensure that the battery pack would
work properly on orbit.
213
6.4.5 Energy Balance Analysis
Energy balance analysis could determine whether the lunar lander energy was
balanced during a specific period of time. When the power balance of the lunar
lander power was calculated, there were many factors to be considered including
illumination condition, load requirement, solar array and battery of power system,
charging and discharging efficiency and etc. The analysis process and calculation
method were basically the same as that of Earth orbit spacecraft.
In LTO, the lunar lander was powered mainly by the solar array. During orbit
changes and phases in Moon shadow, the lunar lander was powered mainly by the
battery pack. At the same time, the long-term power load of the lunar lander was small
and short-term high power loads occurred mainly in orbit changes. In addition, the
interval between orbit changes was usually several orbital periods during circumlunar
phase. For the lunar lander, a multi-turn energy balance method was suitable, which
allowed the battery of the lunar lander to be discharged at a greater depth and fully
charged in subsequent several orbital periods to achieve energy balance. Such design
could reduce the total power output of the solar array so as to reduce the area and
mass of the solar array, and make it possible to select small-capacity battery pack.
If the energy balance was achieved in one orbital period, the power output of the
solar array and the capacity of the battery should be greatly increased. At the same
time, in cruise process of circumlunar orbit, the power output of the solar array was
excessive and a great many shunting was required, which was not optimized design.
The power load of the lunar lander changed dramatically during the mission profile
and the flight process was complex including the launch [11], LTO, 100 km circular
lunar orbit, 100 km × 15 km circumlunar orbit, powered descent, initialization on
lunar surface, operation on lunar surface and lunar eclipse on orbit. The change of
external heat flux was complex during the mission profile and the temperature range
of the battery pack varied greatly, as well as occlusion of the solar array of the lunar
lander was complex during operation on lunar surface.
When energy balance of the lunar lander was calculated, comprehensive consideration should be conducted including the system power load conditions, illumination
conditions, occlusion of solar array and battery support capabilities under a wide
temperature range for each flight phases, as well as various unexpected conditions.
Due to wide range of battery operation temperature on orbit, in order to verify the
discharge capacity of the lithium-ion battery pack under different working conditions,
the same batch of single cells of the lander lithium-ion battery was verified by experiments for different discharge conditions including LOI, circumlunar orbit, powered
descent and lunar eclipse. At the same time, in order to examine the discharge capacity
of the battery pack, the flight hardware of the battery pack was tested according to
the orbital power and temperature conditions to ensure that the battery pack would
work properly on orbit.