11.4 Common Cushion Methods and Their Features
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(2) The attitude of the lunar lander after landing can be adjusted. The damping
system will not be damaged by cushion process and can gradually recover. It
is suitable to missions with strict attitude requirement after landing.
(3) The cost of research and development is higher, and it is very difficult and low
reliable. The parameters such as density and coefficient of viscosity of hydraulic
medium are closely related to environment temperature. Therefore, technical
challenges such as sealing, temperature control and control of viscosity coefficient, shall be overcome before application. At the same time, the requirement
for manufacture accuracy is high, which is definitely costly.
The Surveyor lunar lander of the United States with hydraulic buffer implemented
successful soft-landing on lunar surface. The hydraulic buffer was also applied in
Apollo spacecraft. The buffer came to leakage once in Surveyor missions, but a pyro
mechanism was fired to realize a lockup for the landing gear system and ensured the
attitude of the lunar lander. Because of potential risk of hydraulic buffer, it was not
applied in the landing gear system of Apollo lunar module.
11.4.4 Tensile Deformation of Special Material
The impact energy is absorbed through tensile deformation of a slender rod made of
special material. In the process of damping, the metal rod is stretched. When the yield
strength of the material is exceeded, the metal rod has a plastic deformation. The
impact energy is transferred into plastic deformation energy. The advantages of such
method include reliable cushion process, high specific energy absorption and small
size. The material of tensile rod is generally super plastic in normal temperature,
whose specific elongation is over 50%. The conventional metal is hardly to meet the
requirement.
Such method was applied in secondary struts of the Chang’E-3 lunar lander to
absorb impact energy by tensile deformation.
11.5 Design of Landing Gear Mechanism
11.5.1 Requirements Analysis
1. Functional Requirements and Configuration Analysis
Generally, there were following function requirements for the landing gear mechanism.
(1) It could be stowed, held down, deployment and locked up. Due to limited
volume of launch fairing, the landing gear mechanism was usually stowed and
held down during launch. It would be deployed and locked up after the lunar
lander was injected into predefined orbit.
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(2) The attitude of the lunar lander after landing can be adjusted. The damping
system will not be damaged by cushion process and can gradually recover. It
is suitable to missions with strict attitude requirement after landing.
(3) The cost of research and development is higher, and it is very difficult and low
reliable. The parameters such as density and coefficient of viscosity of hydraulic
medium are closely related to environment temperature. Therefore, technical
challenges such as sealing, temperature control and control of viscosity coefficient, shall be overcome before application. At the same time, the requirement
for manufacture accuracy is high, which is definitely costly.
The Surveyor lunar lander of the United States with hydraulic buffer implemented
successful soft-landing on lunar surface. The hydraulic buffer was also applied in
Apollo spacecraft. The buffer came to leakage once in Surveyor missions, but a pyro
mechanism was fired to realize a lockup for the landing gear system and ensured the
attitude of the lunar lander. Because of potential risk of hydraulic buffer, it was not
applied in the landing gear system of Apollo lunar module.
11.4.4 Tensile Deformation of Special Material
The impact energy is absorbed through tensile deformation of a slender rod made of
special material. In the process of damping, the metal rod is stretched. When the yield
strength of the material is exceeded, the metal rod has a plastic deformation. The
impact energy is transferred into plastic deformation energy. The advantages of such
method include reliable cushion process, high specific energy absorption and small
size. The material of tensile rod is generally super plastic in normal temperature,
whose specific elongation is over 50%. The conventional metal is hardly to meet the
requirement.
Such method was applied in secondary struts of the Chang’E-3 lunar lander to
absorb impact energy by tensile deformation.
11.5 Design of Landing Gear Mechanism
11.5.1 Requirements Analysis
1. Functional Requirements and Configuration Analysis
Generally, there were following function requirements for the landing gear mechanism.
(1) It could be stowed, held down, deployment and locked up. Due to limited
volume of launch fairing, the landing gear mechanism was usually stowed and
held down during launch. It would be deployed and locked up after the lunar
lander was injected into predefined orbit.