15.3 Requirement
493
control of navigation sensors, coordination of control and propulsion subsystem
in powered descent phase, it was necessary to test and verify the process of powered
descent on the ground. However, it was almost impossible to verify the whole process
of powered descent from 15 km to soft landing under current technical conditions,
and it was also unnecessary. In the powered descent phase, the key activities such
as deceleration, terrain identification, obstacle avoidance, hovering and shutdown
should be completed by the lunar lander. With consideration of the limitation of
cost, development schedule and ground simulation methodology, it was necessary
to conduct the ground test for the hovering, the obstacle avoidance and the slow
descending so as to verify the whole process of powered descent.
2. Landing Impact Test
After the powered descent, the lunar lander will be landed softly on lunar surface.
During the final soft landing, the lunar lander would experience the landing impact
load environment, as well as the instruments which would be operated on lunar
surface (scientific payload, the lunar rover). During the soft landing, the lunar lander
was affected by factors such as landing mass, landing velocity, landing attitude,
lunar terrain topography, mechanical characteristics of landing surface and landing
cushion characteristics of landing gears, and etc. And the force transfer path of the
lunar lander during landing impact was that the landing impact load was transferred
to the main structure connection through the landing gear, and then extended to the
structural plates, and then to onboard instruments. Both the force transfer path and
the load characteristics were different from the load environment during launch.
In order to examine the impact resistance of the main structure of the lunar lander
during soft landing, and acquire the impact response of the key parts and the key
instrument connection of the lunar lander, the landing impact process should be tested
on the ground.
3. Landing Stability Test
The most important task of the lunar lander was to complete lunar soft landing.
Whether the lunar lander could be landed on lunar surface with anticipated attitude
and direction would determine the mission success. The landing stability of the lunar
lander was affected by factors such as landing mass, landing velocity, landing attitude,
lunar terrain topography, mechanical characteristics of landing surface and landing
cushion characteristics of landing gears. In order to implement successful lunar soft
landing, the landing stability should be verified on the ground, so as to examine the
impact of the initial conditions on landing stability of the lunar lander.
4. Test of Engine Thrust Pulsation Effect on GNC Sensor
When the large liquid rocket engine is firing, there will be thrust pulsation which
is determined by its inherent combustion characteristics and generally the thrust
pulsation can be controlled within 3% of average thrust. The bipropellant liquid rocket
engine (7500 N throttling engine for the Chang’E-3) was generally used for Lunar
Orbit Insertion and deceleration during powered descent. In the powered descent,
493
control of navigation sensors, coordination of control and propulsion subsystem
in powered descent phase, it was necessary to test and verify the process of powered
descent on the ground. However, it was almost impossible to verify the whole process
of powered descent from 15 km to soft landing under current technical conditions,
and it was also unnecessary. In the powered descent phase, the key activities such
as deceleration, terrain identification, obstacle avoidance, hovering and shutdown
should be completed by the lunar lander. With consideration of the limitation of
cost, development schedule and ground simulation methodology, it was necessary
to conduct the ground test for the hovering, the obstacle avoidance and the slow
descending so as to verify the whole process of powered descent.
2. Landing Impact Test
After the powered descent, the lunar lander will be landed softly on lunar surface.
During the final soft landing, the lunar lander would experience the landing impact
load environment, as well as the instruments which would be operated on lunar
surface (scientific payload, the lunar rover). During the soft landing, the lunar lander
was affected by factors such as landing mass, landing velocity, landing attitude,
lunar terrain topography, mechanical characteristics of landing surface and landing
cushion characteristics of landing gears, and etc. And the force transfer path of the
lunar lander during landing impact was that the landing impact load was transferred
to the main structure connection through the landing gear, and then extended to the
structural plates, and then to onboard instruments. Both the force transfer path and
the load characteristics were different from the load environment during launch.
In order to examine the impact resistance of the main structure of the lunar lander
during soft landing, and acquire the impact response of the key parts and the key
instrument connection of the lunar lander, the landing impact process should be tested
on the ground.
3. Landing Stability Test
The most important task of the lunar lander was to complete lunar soft landing.
Whether the lunar lander could be landed on lunar surface with anticipated attitude
and direction would determine the mission success. The landing stability of the lunar
lander was affected by factors such as landing mass, landing velocity, landing attitude,
lunar terrain topography, mechanical characteristics of landing surface and landing
cushion characteristics of landing gears. In order to implement successful lunar soft
landing, the landing stability should be verified on the ground, so as to examine the
impact of the initial conditions on landing stability of the lunar lander.
4. Test of Engine Thrust Pulsation Effect on GNC Sensor
When the large liquid rocket engine is firing, there will be thrust pulsation which
is determined by its inherent combustion characteristics and generally the thrust
pulsation can be controlled within 3% of average thrust. The bipropellant liquid rocket
engine (7500 N throttling engine for the Chang’E-3) was generally used for Lunar
Orbit Insertion and deceleration during powered descent. In the powered descent,