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13 Metrology Technology of Lunar Lander
The automated gas fill and vent technology was applied for safe, stable and reliable
fill and vent of tracer gas in leak test of the propulsion subsystem. Because pressure in
the leak test of the Chang’E-3 lunar lander propulsion subsystem was high, the safety
and reliability of gas fill and vent equipment should be very high. The equipment
should effectively control the gas fill and vent rate by automatic control of the opening
of proportional valve, while the efficiency of gas fill and vent should be appropriate.
Based on the principle and experience of manual gas fill and vent, and the test data
of simulated products, the control parameters of proportional valve were set up. The
automated gas fill and vent system effectively implemented gas fill and vent with the
accuracy of fill and vent rate 0.01 MPa/min. At the same time, the volume of helium
gas used for the Chang’E-3 lunar lander was large. In order to save resource, the
automated gas fill and vent system should be able to recycle helium gas [11]. Up to
date, the automated gas fill and vent system could achieve recovery of 80% helium.
The basic principle of non-vacuum accumulation leak test technology by helium
Mass Spectrometer is as follows. At first, the propulsion subsystem of the lunar
lander to be tested was filled with helium and the pressure should be same as on
orbit. Through effective single point leak test technology, the leakage rate of single
point should meet the designed requirement. Then the lunar lander would be put into
non-vacuum container (collection room or leak test container) and sealed. With the
helium Mass Spectrometer leak detector, the concentration of helium in the container
would be examined. After stand still for 24 h, the change of helium concentration in
the container would be examined. For the calibration of leak test system, a definite
quantitative of gas should be filled into the container to examine the change of helium
concentration in the container.
The leak test results should be compared with the calibration data to calculate the
leak and leakage rate of the tested propulsion subsystem of the lunar lander.
The automated total leak detector was the core to complete the total leakage rate
test, which was a new developed automated leakage rate detector based on sampler
of laser micro hole and standard Mass Spectrometer leak detector for total leak rate
test of spacecraft. The sampler based on laser micro hole was the key to automation
of the leak detector, which consisted of valve, micro hole in fixed size, standard gas
solenoid valve and sample gas solenoid valve. The leak test port was in the middle of
the valve. The upper part of the main path was connected with the leak test port and
there was a micro hole. The sampling port channels that were connected with the leak
test part were respectively connected to standard gas solenoid valve and sample gas
solenoid valve. On both sides of the valve, there were one input port and one output
port for both of standard gas solenoid valve and sample gas solenoid valve. They
were integrated into one channel and connected to the corresponding standard gas
solenoid valve and sample gas solenoid valve. Compared with original technology,
the leak detector could implement the switch between the standard gas and the sample
gas during the total leak test by solenoid valve, and the flow limitation by micro hole
in fixed size, so as to avoid the randomness caused by human operation. The air
clear valve was added between the standard gas solenoid valve and the sample gas
solenoid valve to solve the issue of tailing phenomenon in multi-channel gas mass
13 Metrology Technology of Lunar Lander
The automated gas fill and vent technology was applied for safe, stable and reliable
fill and vent of tracer gas in leak test of the propulsion subsystem. Because pressure in
the leak test of the Chang’E-3 lunar lander propulsion subsystem was high, the safety
and reliability of gas fill and vent equipment should be very high. The equipment
should effectively control the gas fill and vent rate by automatic control of the opening
of proportional valve, while the efficiency of gas fill and vent should be appropriate.
Based on the principle and experience of manual gas fill and vent, and the test data
of simulated products, the control parameters of proportional valve were set up. The
automated gas fill and vent system effectively implemented gas fill and vent with the
accuracy of fill and vent rate 0.01 MPa/min. At the same time, the volume of helium
gas used for the Chang’E-3 lunar lander was large. In order to save resource, the
automated gas fill and vent system should be able to recycle helium gas [11]. Up to
date, the automated gas fill and vent system could achieve recovery of 80% helium.
The basic principle of non-vacuum accumulation leak test technology by helium
Mass Spectrometer is as follows. At first, the propulsion subsystem of the lunar
lander to be tested was filled with helium and the pressure should be same as on
orbit. Through effective single point leak test technology, the leakage rate of single
point should meet the designed requirement. Then the lunar lander would be put into
non-vacuum container (collection room or leak test container) and sealed. With the
helium Mass Spectrometer leak detector, the concentration of helium in the container
would be examined. After stand still for 24 h, the change of helium concentration in
the container would be examined. For the calibration of leak test system, a definite
quantitative of gas should be filled into the container to examine the change of helium
concentration in the container.
The leak test results should be compared with the calibration data to calculate the
leak and leakage rate of the tested propulsion subsystem of the lunar lander.
The automated total leak detector was the core to complete the total leakage rate
test, which was a new developed automated leakage rate detector based on sampler
of laser micro hole and standard Mass Spectrometer leak detector for total leak rate
test of spacecraft. The sampler based on laser micro hole was the key to automation
of the leak detector, which consisted of valve, micro hole in fixed size, standard gas
solenoid valve and sample gas solenoid valve. The leak test port was in the middle of
the valve. The upper part of the main path was connected with the leak test port and
there was a micro hole. The sampling port channels that were connected with the leak
test part were respectively connected to standard gas solenoid valve and sample gas
solenoid valve. On both sides of the valve, there were one input port and one output
port for both of standard gas solenoid valve and sample gas solenoid valve. They
were integrated into one channel and connected to the corresponding standard gas
solenoid valve and sample gas solenoid valve. Compared with original technology,
the leak detector could implement the switch between the standard gas and the sample
gas during the total leak test by solenoid valve, and the flow limitation by micro hole
in fixed size, so as to avoid the randomness caused by human operation. The air
clear valve was added between the standard gas solenoid valve and the sample gas
solenoid valve to solve the issue of tailing phenomenon in multi-channel gas mass