11.5 Design of Landing Gear Mechanism
387
In order to output landing signal at touchdown, there was triggering switch in the
bottom surface of the footpad. There could be several triggering switches because
the touchdown attitude of the footpad was uncertain on complex landing surface.
The landing signal could be output when any of these switches was on. In order to
avoid wrong touchdown signals, logical judgment of landing signal was necessary.
5) Lubrication design. The joint surfaces of the landing gear were exposed to a
high level of vacuum for the lunar lander on orbit. The vacuum might induce
phenomenon of cold welding on joint surfaces, which might cause friction
increment or unstable mechanical movement, even failure of the mechanism
movement. To reduce probability of above malfunction, proper lubrication on
the joint surfaces of landing gear mechanism was necessary.
After all factors were considered, such as environment experienced by the landing
gear from launch to touchdown on lunar surface, load, requirement of lifetime, characteristics of mechanism movement, and compatibility of materials and the lubricant,
generally solid lubricant MoS 2 was sprayed or sputtered to joint surfaces of landing
gear mechanism.
6) Thermal design. The temperature of all parts of the landing gear mechanism
was controlled in specific range to ensure normal operation by thermal design.
The focus of thermal design included install position of pyrotechnical devices,
important joints and load-bearing parts [9].
For anticipated extreme temperature under high and low temperature environment,
different units of low temperature and high temperature multi-layer insulation were
wrapped over the parts, which were fastened by nylon buckles, temperature resistant
wires and silicon rubber. Additional insulation on the side adjacent to the engine was
necessary to avoid thermal effects of the engine plume during flight.
There should be ground connection on parts with the multi-layer insulation to
release static electricity.
The temperature sensors were necessary to monitor real time temperature during
flight and evaluate effectiveness of thermal control.
3. Simulation of Landing Dynamics
Because of special lunar surface environment, it was very difficult to establish precise
model of landing impact dynamics, which involved mechanical properties of lunar
soil, landing gear mechanism and landing impact process. Analysis and verification
if landing impact dynamics were a complex and systematic task, which played an
important role in research and development of landing gear mechanism [10].
The common procedure of analysis and verification of landing dynamics is shown
in Fig. 11.16.
(1) The landing dynamic simulation model for landing gear mechanism should be
established, which was a parametric model for simulation of landing dynamics
under random conditions and different lunar surface.
387
In order to output landing signal at touchdown, there was triggering switch in the
bottom surface of the footpad. There could be several triggering switches because
the touchdown attitude of the footpad was uncertain on complex landing surface.
The landing signal could be output when any of these switches was on. In order to
avoid wrong touchdown signals, logical judgment of landing signal was necessary.
5) Lubrication design. The joint surfaces of the landing gear were exposed to a
high level of vacuum for the lunar lander on orbit. The vacuum might induce
phenomenon of cold welding on joint surfaces, which might cause friction
increment or unstable mechanical movement, even failure of the mechanism
movement. To reduce probability of above malfunction, proper lubrication on
the joint surfaces of landing gear mechanism was necessary.
After all factors were considered, such as environment experienced by the landing
gear from launch to touchdown on lunar surface, load, requirement of lifetime, characteristics of mechanism movement, and compatibility of materials and the lubricant,
generally solid lubricant MoS 2 was sprayed or sputtered to joint surfaces of landing
gear mechanism.
6) Thermal design. The temperature of all parts of the landing gear mechanism
was controlled in specific range to ensure normal operation by thermal design.
The focus of thermal design included install position of pyrotechnical devices,
important joints and load-bearing parts [9].
For anticipated extreme temperature under high and low temperature environment,
different units of low temperature and high temperature multi-layer insulation were
wrapped over the parts, which were fastened by nylon buckles, temperature resistant
wires and silicon rubber. Additional insulation on the side adjacent to the engine was
necessary to avoid thermal effects of the engine plume during flight.
There should be ground connection on parts with the multi-layer insulation to
release static electricity.
The temperature sensors were necessary to monitor real time temperature during
flight and evaluate effectiveness of thermal control.
3. Simulation of Landing Dynamics
Because of special lunar surface environment, it was very difficult to establish precise
model of landing impact dynamics, which involved mechanical properties of lunar
soil, landing gear mechanism and landing impact process. Analysis and verification
if landing impact dynamics were a complex and systematic task, which played an
important role in research and development of landing gear mechanism [10].
The common procedure of analysis and verification of landing dynamics is shown
in Fig. 11.16.
(1) The landing dynamic simulation model for landing gear mechanism should be
established, which was a parametric model for simulation of landing dynamics
under random conditions and different lunar surface.