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8 Propulsion Technology of Lunar Lander
8.4.4 Electronics Design of Propulsion Subsystem
Propulsion subsystem electronics which converted different types of control
commands to drive propulsion valve and collected telemetry downlink data of
different types of status parameters, was a “key node” between spacecraft control
subsystems (GNC, power supply, telecommunication) and propulsion subsystem, and
was generally integrated in the control unit. Because of the importance of control unit,
dual or triple redundancy design could ensure reliable operation. The control unit
of propulsion subsystem was designed for power control of different instruments,
DC/DC secondary power conversion, valve (including solenoid and latch valve)
drive control, stepping motor control for throttleable engine, sensor data collection
and processing, autonomous on/off control of thermal heater, autonomous failure
detection and switch control, internal status monitoring for control unit, telemetry
communication and etc. Generally the relay was used to control on/off switch of
instruments. CMOS was widely used to control on/off switch of valve and heater. Hbridge inverter based on intelligent chip was used to control stepping motor. RS-422
asynchronous serial interface or 1553 bus interface was used to implement command
communication. For pressure, displacement and contact switch, voltage output is
0~5 V. For temperature sensor, branch voltage circuit was used. For example, the
control unit of the Chang’E-3 lunar lander propulsion applied A/B branch with cold
redundancy design based on 80C32 as the central unit, one of which could conduct
all control functions of propulsion subsystem. The stepping motor was controlled by
chopping constant current control mode based on H-bridge driver chip LMD18200T
with RS-422 asynchronous serial command interface. Two subdivision in step angle
could enhance operation resolution and stability of the stepping motor.
8.4.5 AIT Design of Propulsion Subsystem
1. Configuration Design
Configuration design of the lunar lander propulsion subsystem was closely related
to configuration design of the lunar lander system. On the basis of the lunar lander
configuration and synthesis of component position & pipeline layout, the principle
of propulsion subsystem configuration was symmetry, easy to assembly, convenient
for test, modular and integration. Analysis of past the lunar lander configuration
showed that truss or plate structure was generally used with 4 tanks horizontally, an
orbit control engine in the center, gas tanks outside of the lunar lander or between the
tanks, attitude control thrusters outside the lunar lander, and other parts inside such as
valves, pipelines, electronic unit, cable and etc. For example, it was cross-like plate
structure with 4 propellant tanks symmetrically located between cross-like plates, an
orbit control engine in the center, 2 gas tanks hung outside lander, 28 attitude control
thrusters outside of the lunar lander respectively at upper, middle and bottom, tanks
fixed by flanges and rods in propulsion subsystem of the Chang’E-3 lunar lander.
8 Propulsion Technology of Lunar Lander
8.4.4 Electronics Design of Propulsion Subsystem
Propulsion subsystem electronics which converted different types of control
commands to drive propulsion valve and collected telemetry downlink data of
different types of status parameters, was a “key node” between spacecraft control
subsystems (GNC, power supply, telecommunication) and propulsion subsystem, and
was generally integrated in the control unit. Because of the importance of control unit,
dual or triple redundancy design could ensure reliable operation. The control unit
of propulsion subsystem was designed for power control of different instruments,
DC/DC secondary power conversion, valve (including solenoid and latch valve)
drive control, stepping motor control for throttleable engine, sensor data collection
and processing, autonomous on/off control of thermal heater, autonomous failure
detection and switch control, internal status monitoring for control unit, telemetry
communication and etc. Generally the relay was used to control on/off switch of
instruments. CMOS was widely used to control on/off switch of valve and heater. Hbridge inverter based on intelligent chip was used to control stepping motor. RS-422
asynchronous serial interface or 1553 bus interface was used to implement command
communication. For pressure, displacement and contact switch, voltage output is
0~5 V. For temperature sensor, branch voltage circuit was used. For example, the
control unit of the Chang’E-3 lunar lander propulsion applied A/B branch with cold
redundancy design based on 80C32 as the central unit, one of which could conduct
all control functions of propulsion subsystem. The stepping motor was controlled by
chopping constant current control mode based on H-bridge driver chip LMD18200T
with RS-422 asynchronous serial command interface. Two subdivision in step angle
could enhance operation resolution and stability of the stepping motor.
8.4.5 AIT Design of Propulsion Subsystem
1. Configuration Design
Configuration design of the lunar lander propulsion subsystem was closely related
to configuration design of the lunar lander system. On the basis of the lunar lander
configuration and synthesis of component position & pipeline layout, the principle
of propulsion subsystem configuration was symmetry, easy to assembly, convenient
for test, modular and integration. Analysis of past the lunar lander configuration
showed that truss or plate structure was generally used with 4 tanks horizontally, an
orbit control engine in the center, gas tanks outside of the lunar lander or between the
tanks, attitude control thrusters outside the lunar lander, and other parts inside such as
valves, pipelines, electronic unit, cable and etc. For example, it was cross-like plate
structure with 4 propellant tanks symmetrically located between cross-like plates, an
orbit control engine in the center, 2 gas tanks hung outside lander, 28 attitude control
thrusters outside of the lunar lander respectively at upper, middle and bottom, tanks
fixed by flanges and rods in propulsion subsystem of the Chang’E-3 lunar lander.