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7 Guidance, Navigation and Control Technology …
10. Orbit Control Engine
The Orbit Control Engine was actuator of the lunar lander for orbit maneuver and
powered descent. The engine was a 7500 N throttling engine, which could provide
continuously throttling thrust through flow adjustment, so that the engine had less
influence on the tremble of the lunar lander and it was much easier to design the
guidance law when the engine thrust was throttling. The Orbit Control Engine was
installed on the −X side of the lunar lander, and the direction of thrust vector pointed
to the +X direction of the lunar lander’s mechanical coordinate system.
11. Attitude Control Thrusters
The attitude control thrusters were actuators for attitude control of the lunar lander.
Due to the resource constraints of the lunar lander, the configuration of the attitude control thrusters should not only ensure the implementation of attitude control
function, but also be simplified as much as possible.
The design principles of attitude control thruster configuration included:
(1) The 10 N thrusters were in the form of a force couple to reduce the effect
of attitude control during circumlunar orbit phase on the accuracy of orbit
determination at the 15 km perilune.
(2) The 150 N thrusters should increase the attitude control capability as much as
possible to resist the impact of Y, Z axis disturbance torque.
(3) Because the 150 N thrusters should achieve not only attitude control during
orbit maneuver, but also the orbit control of the obstacle avoidance and the
horizontal translation during the slow descending, the 150 N thrusters should
be backed up as much as possible to ensure landing safety.
Based on above three considerations, the final thruster configuration was finally
determined, where 12 × 10 N thrusters were configured to A and B branches, and
16 × 150 N thrusters were configured to C and D branches.
Thrusters Configuration of Chang’E-3 the lunar lander is shown in Fig. 7.8.
7.4.4 Software Design [7]
Recently the application of computer systems in spacecraft had become more and
more widespread along with development of aerospace industry and computer technology in China. Due to complexity of navigation, guidance and control algorithms,
GNC subsystem was one of the subsystems that prefer application of computer
systems.
With the continuous improvement of computer hardware performance and quality,
the requirement for computer software was getting higher and higher. The size of
GNC subsystem software was getting larger and larger and the complexity was
getting higher and higher. The code of the GNC subsystem application software had
exceeded 20,000 lines.
7 Guidance, Navigation and Control Technology …
10. Orbit Control Engine
The Orbit Control Engine was actuator of the lunar lander for orbit maneuver and
powered descent. The engine was a 7500 N throttling engine, which could provide
continuously throttling thrust through flow adjustment, so that the engine had less
influence on the tremble of the lunar lander and it was much easier to design the
guidance law when the engine thrust was throttling. The Orbit Control Engine was
installed on the −X side of the lunar lander, and the direction of thrust vector pointed
to the +X direction of the lunar lander’s mechanical coordinate system.
11. Attitude Control Thrusters
The attitude control thrusters were actuators for attitude control of the lunar lander.
Due to the resource constraints of the lunar lander, the configuration of the attitude control thrusters should not only ensure the implementation of attitude control
function, but also be simplified as much as possible.
The design principles of attitude control thruster configuration included:
(1) The 10 N thrusters were in the form of a force couple to reduce the effect
of attitude control during circumlunar orbit phase on the accuracy of orbit
determination at the 15 km perilune.
(2) The 150 N thrusters should increase the attitude control capability as much as
possible to resist the impact of Y, Z axis disturbance torque.
(3) Because the 150 N thrusters should achieve not only attitude control during
orbit maneuver, but also the orbit control of the obstacle avoidance and the
horizontal translation during the slow descending, the 150 N thrusters should
be backed up as much as possible to ensure landing safety.
Based on above three considerations, the final thruster configuration was finally
determined, where 12 × 10 N thrusters were configured to A and B branches, and
16 × 150 N thrusters were configured to C and D branches.
Thrusters Configuration of Chang’E-3 the lunar lander is shown in Fig. 7.8.
7.4.4 Software Design [7]
Recently the application of computer systems in spacecraft had become more and
more widespread along with development of aerospace industry and computer technology in China. Due to complexity of navigation, guidance and control algorithms,
GNC subsystem was one of the subsystems that prefer application of computer
systems.
With the continuous improvement of computer hardware performance and quality,
the requirement for computer software was getting higher and higher. The size of
GNC subsystem software was getting larger and larger and the complexity was
getting higher and higher. The code of the GNC subsystem application software had
exceeded 20,000 lines.