11.5 Design of Landing Gear Mechanism
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(3) Attitude angles and angular velocities in three directions. These terms were
also generally presented in the said local coordination system and related to
touchdown stability and attenuation performance.
(4) Landing surface. It referred to the slope, depth of pit or height of rock, and
mechanical properties of lunar surface. It was closely related to touchdown
stability, and cushion performance to some extent.
(5) Maximal envelope of launch faring. It referred to radial and axial envelope. The
axial envelope was often expressed relative to a reference plane of the lunar
lander. It determined whether the landing gear mechanism should be stowed
during launch.
3. Requirements Analysis for Performance and Interface
The performance specifications of the landing gear mechanism included following
aspects [7].
(1) Mass, strength and stiffness. The mass referred to maximal acceptable mass.
Requirements of mass, strength and stiffness are one of core issues in design
process of the landing gear mechanism. The performance of stable landing
should be improved as far as possible on condition that the requirements of
mass, strength and stiffness were satisfied.
(2) Deployment and lock-up. If the landing gear mechanism should be deployed
on orbit, such requirement would be come up. It included the static torque
(force) margin, deploy time and peak of impact load in deployment process.
The method to realize hold-down, release, deploy and lock-up was determined
by such requirements.
(3) Cushion characteristics. It was core requirement of performance which
included peak response and time span of impact load, landing stability and
attitude change after landing, sometimes even cushion method and length of
the stroke.
(4) Lifetime and reliability. The requirement of lifetime generally included storage
time on ground and operation time in space. The requirement of reliability
generally referred to the degree of reliability in the mission profile under a
specific confidence.
(5) Interfaces. Interface requirement included mechanical interface, thermal interface (thermal environment) and electrical interface (including energy consumption). It was determined by these interfaces including the method and timeline
of assembly for the landing gear mechanism in AIT phase, thermal control
methods, material, type of electrical component and part, and etc.
4. Environment Analysis
Besides general ground environment, following environments should be endured by
the landing gear mechanism.
(1) Vibration. The vibration environment during launch might cause deformation
or broken of mechanism because of stress. For the landing gear mechanism,
the hold-down device should be avoided to be loosened. Moreover, the stress
concentration due to load cycling of vibration should be avoided, which might
cause deformation or rupture of parts of the landing gear mechanism.
377
(3) Attitude angles and angular velocities in three directions. These terms were
also generally presented in the said local coordination system and related to
touchdown stability and attenuation performance.
(4) Landing surface. It referred to the slope, depth of pit or height of rock, and
mechanical properties of lunar surface. It was closely related to touchdown
stability, and cushion performance to some extent.
(5) Maximal envelope of launch faring. It referred to radial and axial envelope. The
axial envelope was often expressed relative to a reference plane of the lunar
lander. It determined whether the landing gear mechanism should be stowed
during launch.
3. Requirements Analysis for Performance and Interface
The performance specifications of the landing gear mechanism included following
aspects [7].
(1) Mass, strength and stiffness. The mass referred to maximal acceptable mass.
Requirements of mass, strength and stiffness are one of core issues in design
process of the landing gear mechanism. The performance of stable landing
should be improved as far as possible on condition that the requirements of
mass, strength and stiffness were satisfied.
(2) Deployment and lock-up. If the landing gear mechanism should be deployed
on orbit, such requirement would be come up. It included the static torque
(force) margin, deploy time and peak of impact load in deployment process.
The method to realize hold-down, release, deploy and lock-up was determined
by such requirements.
(3) Cushion characteristics. It was core requirement of performance which
included peak response and time span of impact load, landing stability and
attitude change after landing, sometimes even cushion method and length of
the stroke.
(4) Lifetime and reliability. The requirement of lifetime generally included storage
time on ground and operation time in space. The requirement of reliability
generally referred to the degree of reliability in the mission profile under a
specific confidence.
(5) Interfaces. Interface requirement included mechanical interface, thermal interface (thermal environment) and electrical interface (including energy consumption). It was determined by these interfaces including the method and timeline
of assembly for the landing gear mechanism in AIT phase, thermal control
methods, material, type of electrical component and part, and etc.
4. Environment Analysis
Besides general ground environment, following environments should be endured by
the landing gear mechanism.
(1) Vibration. The vibration environment during launch might cause deformation
or broken of mechanism because of stress. For the landing gear mechanism,
the hold-down device should be avoided to be loosened. Moreover, the stress
concentration due to load cycling of vibration should be avoided, which might
cause deformation or rupture of parts of the landing gear mechanism.