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4 Structure and Mechanism Technology of Lunar Lander
In the design of lunar lander structure, the following aspects should be considered:
(1) Lightweight structure. Lightweight is the eternal theme of spacecraft design,
especially for deep space probes such as lunar lander. Due to the constraints
of the launch vehicle, the mass of the lunar lander is strictly limited, while the
structural mass accounts for a large proportion of the dry mass of lunar lander.
(2) The design of structural configuration of lunar lander must focus on the installation of large fuel tanks, large engines, and the lower center of gravity requirements of soft-landing. The lunar lander needs to carry a large amount of propellant in order to change orbit and descend. The propellant mass of lunar lander
is a large proportion of the mass and usually is about 2/3 of the launch mass.
Therefore, large fuel tanks need to be installed. A large engine is necessary for
powered descent. In order to ensure stability after soft-landing, it is more important to lower the center of gravity of lunar lander. Therefore, a flat structure
shall be used for lunar lander.
(3) The lunar lander structure is subjected to a landing impact load. The lunar
lander has a certain speed (kinetic energy) before landing. The energy shall be
absorbed instantly when the landing cushion mechanism collides with lunar
surface, which will cause a large landing impact load upon lunar lander. The
landing impact load is transferred to the structure by the landing cushion mechanism. For a typical landing gear type of landing cushion mechanism, the landing
impact load is a concentrated load, and the force transfer path of the landing
impact load may be completely different from the transfer path of the launch
load (the launch load is transferred to the structure by the docking surface of
the launch vehicle, but there was also the same design for the force transfer
path, such as the Apollo series spacecraft). It requires that the structure of the
lunar lander is totally different from traditional spacecraft and spaceship.
(4) The structure is subjected to a landing impact load after experiencing high
temperature and low temperature environment. While landing, the lunar lander
structure has experienced a harsh temperature environment during flight,
and the temperature level of the structure at landing is higher. Therefore,
special attention shall be paid to bearing capacity on a special temperature
environment.
4.2.2 Mechanism Features of Lunar Lander
Different mechanisms are often needed to achieve different specific functional
requirements on lunar lander. The types of mechanisms are up to specific mission
requirements of the lunar lander. The typical lunar lander mechanisms include landing
cushion mechanism, solar panel mechanism, antenna pointing mechanism, and mechanism for separation and deployment of the lunar rover. The type and approach
of lunar lander mechanism is not only up to the mission characteristics of lunar
lander, but also closely related to the general configuration of lunar lander, technical
specification, environment on lunar surface and other factors.
4 Structure and Mechanism Technology of Lunar Lander
In the design of lunar lander structure, the following aspects should be considered:
(1) Lightweight structure. Lightweight is the eternal theme of spacecraft design,
especially for deep space probes such as lunar lander. Due to the constraints
of the launch vehicle, the mass of the lunar lander is strictly limited, while the
structural mass accounts for a large proportion of the dry mass of lunar lander.
(2) The design of structural configuration of lunar lander must focus on the installation of large fuel tanks, large engines, and the lower center of gravity requirements of soft-landing. The lunar lander needs to carry a large amount of propellant in order to change orbit and descend. The propellant mass of lunar lander
is a large proportion of the mass and usually is about 2/3 of the launch mass.
Therefore, large fuel tanks need to be installed. A large engine is necessary for
powered descent. In order to ensure stability after soft-landing, it is more important to lower the center of gravity of lunar lander. Therefore, a flat structure
shall be used for lunar lander.
(3) The lunar lander structure is subjected to a landing impact load. The lunar
lander has a certain speed (kinetic energy) before landing. The energy shall be
absorbed instantly when the landing cushion mechanism collides with lunar
surface, which will cause a large landing impact load upon lunar lander. The
landing impact load is transferred to the structure by the landing cushion mechanism. For a typical landing gear type of landing cushion mechanism, the landing
impact load is a concentrated load, and the force transfer path of the landing
impact load may be completely different from the transfer path of the launch
load (the launch load is transferred to the structure by the docking surface of
the launch vehicle, but there was also the same design for the force transfer
path, such as the Apollo series spacecraft). It requires that the structure of the
lunar lander is totally different from traditional spacecraft and spaceship.
(4) The structure is subjected to a landing impact load after experiencing high
temperature and low temperature environment. While landing, the lunar lander
structure has experienced a harsh temperature environment during flight,
and the temperature level of the structure at landing is higher. Therefore,
special attention shall be paid to bearing capacity on a special temperature
environment.
4.2.2 Mechanism Features of Lunar Lander
Different mechanisms are often needed to achieve different specific functional
requirements on lunar lander. The types of mechanisms are up to specific mission
requirements of the lunar lander. The typical lunar lander mechanisms include landing
cushion mechanism, solar panel mechanism, antenna pointing mechanism, and mechanism for separation and deployment of the lunar rover. The type and approach
of lunar lander mechanism is not only up to the mission characteristics of lunar
lander, but also closely related to the general configuration of lunar lander, technical
specification, environment on lunar surface and other factors.