5.4 Design Methodology
163
5.4 Design Methodology
5.4.1 Principles of Thermal Design
The thermal design of the lunar lander was based on the characteristics and requirements of the mission, as well as the internal and external heat load and typical flight
events experienced by the lunar lander in different phases. Various thermal control
measures were used to organize the heat exchange process inside and outside the
lunar lander. And it could ensure that the temperature of all instruments and structures satisfies the requirements during the entire lifetime of the lunar lander. Besides,
it was also necessary to minimize the need for resources such as mass and power.
The main design principles of thermal control subsystem for the lunar lander were
as follows:
(1) Insulation among different modules to minimize mutual influence. The concept
of “modular design” was applied where thermal insulation was designed for
each module. As for the instruments that were no longer used after landing,
the temperature should satisfy the requirements only before landing. While for
the instruments working on lunar surface, it should satisfy the requirements of
high temperature during the lunar daytime. The introduction of heat from RHU
could make sure that the storage requirement during lunar night are satisfied.
(2) Favorable surface orientation for heat dissipation. After landing, the heat dissipation surface of the lunar lander was oriented to zenith in order to minimize
the effect of the high temperature of lunar surface on the heat dissipation capability. In addition, the configuration of heat dissipation surface, heat pipe and
two-phase fluid loops should be able to adapt to the possible tilt of the lunar
lander after landing. They could operate well even if the maximum tilt attitude
occurs.
(3) Insulation of thermal coupling between exposed parts and main body. Except
for the necessary radiation surface, the outer surface of the lunar lander was
covered with multilayer insulation component. And the exposed components
such as TT&C antenna and mechanisms were connected to main body with
insulation material. Such design could minimize the effect of environmental
changes on temperature of internal instruments.
(4) New approach for harsh environmental issues. The use of variable conductivity
heat pipes (VCHP), two-phase fluid loops and isotope heat sources (RHU)
could satisfy the heat dissipation requirement for internal instruments during
LTO, circumlunar and lunar daytime on lunar surface. In the lunar night, VCHP
was shut off and two-phase fluid loop transfer the heat of RHU into relative
modules to keep warm for survival requirement. In design of VCHP and twophase fluid loop, the ground gravity (1 g), lunar gravity (1/6 g) on lunar surface
and effect of micro-gravity during LTO and circumlunar phases should be
considered to make sure normal operation in microgravity conditions and make
use of lunar gravity to improve performance.
163
5.4 Design Methodology
5.4.1 Principles of Thermal Design
The thermal design of the lunar lander was based on the characteristics and requirements of the mission, as well as the internal and external heat load and typical flight
events experienced by the lunar lander in different phases. Various thermal control
measures were used to organize the heat exchange process inside and outside the
lunar lander. And it could ensure that the temperature of all instruments and structures satisfies the requirements during the entire lifetime of the lunar lander. Besides,
it was also necessary to minimize the need for resources such as mass and power.
The main design principles of thermal control subsystem for the lunar lander were
as follows:
(1) Insulation among different modules to minimize mutual influence. The concept
of “modular design” was applied where thermal insulation was designed for
each module. As for the instruments that were no longer used after landing,
the temperature should satisfy the requirements only before landing. While for
the instruments working on lunar surface, it should satisfy the requirements of
high temperature during the lunar daytime. The introduction of heat from RHU
could make sure that the storage requirement during lunar night are satisfied.
(2) Favorable surface orientation for heat dissipation. After landing, the heat dissipation surface of the lunar lander was oriented to zenith in order to minimize
the effect of the high temperature of lunar surface on the heat dissipation capability. In addition, the configuration of heat dissipation surface, heat pipe and
two-phase fluid loops should be able to adapt to the possible tilt of the lunar
lander after landing. They could operate well even if the maximum tilt attitude
occurs.
(3) Insulation of thermal coupling between exposed parts and main body. Except
for the necessary radiation surface, the outer surface of the lunar lander was
covered with multilayer insulation component. And the exposed components
such as TT&C antenna and mechanisms were connected to main body with
insulation material. Such design could minimize the effect of environmental
changes on temperature of internal instruments.
(4) New approach for harsh environmental issues. The use of variable conductivity
heat pipes (VCHP), two-phase fluid loops and isotope heat sources (RHU)
could satisfy the heat dissipation requirement for internal instruments during
LTO, circumlunar and lunar daytime on lunar surface. In the lunar night, VCHP
was shut off and two-phase fluid loop transfer the heat of RHU into relative
modules to keep warm for survival requirement. In design of VCHP and twophase fluid loop, the ground gravity (1 g), lunar gravity (1/6 g) on lunar surface
and effect of micro-gravity during LTO and circumlunar phases should be
considered to make sure normal operation in microgravity conditions and make
use of lunar gravity to improve performance.