300
8 Propulsion Technology of Lunar Lander
applied with different inverse pressure drop, and then the change of diaphragm
perimeter was measured: Under 0.2 MPa, the perimeter was almost not changed;
Under 0.2~0.25 MPa, the perimeter was slightly changed; Under 0.8 MPa, the
perimeter was significantly enlarged, but no burst leaking happened. Another tank
filled with oxidizer to simulate long term storage from propellant filling to launch (no
more than 10 days) with endurance of saturated pressure (maximally no more than
0.2 MPa). After 10 days of storage with 0.2 MPa, if it was examined to be normal, the
pressure was enhanced to 0.3 MPa for 10 days. Finally, the tank conducted expulsion
test normally. The pressure drop, expulsion efficiency and overturn times of metal
diaphragm satisfied the requirements.
8.5.4 Long-Term Pressure-Bearing Storage Test of Gas Tank
Gas tank of propulsion subsystem for the lunar lander was used to store pressurized
gas for propellant expulsion. Because of mass constraints, gas tank of high pressure,
light weight and composite wrapped structure was widely used. Besides leak test,
vibration, shock, thermal vacuum, thermal circle, fatigue and burst pressure tests,
in terms of ground storage time after gas filling and operation time in orbit, it was
also necessary to validate long term pressure-bearing capability and reliability. For
example, composite wrapped gas tanks (aluminum inner) with 1.5 of safety factor,
35 MPa of working pressure, 100 L of volume and T1000 wrapping materials was
applied in propulsion subsystem of the Chang’E-3 lunar lander. In order to simulate
storage process from filling to launch, one gas tank was used to store helium for
41 days with 35 MPa pressure. During the storage process, 6 helium leakage rate
detection were conducted totally with satisfactory results. Long term pressure bearing
capability and reliability were fully verified.
8.5.5 Propellant Filling Test
Propellant filling for the lunar lander was the most critical process in launch
campaign. Because of toxicity of propellant, it couldn’t be verified with real propellant when the flight hardware was developed, examined and tested. Therefore, during
the process of development, special propellant filling test was usually conducted to
assess the consistency and correctness of filling, parameters, safety, ground equipment and etc. For example, evacuation and synchronous equilibrium filling for the
two tanks of same propellant was applied for propulsion subsystem of the Chang’E3 lunar lander. Because there would be NO out of MON-1 oxidizer during vacuum
filling, it was necessary to monitor and control filling temperature, pressure, speed
and etc. Therefore, special propellant filling tests of propulsion subsystem with
different conditions such as different propellant temperatures and filling pressures
were conducted to formulate appropriate filling technical solution in launch site.
8 Propulsion Technology of Lunar Lander
applied with different inverse pressure drop, and then the change of diaphragm
perimeter was measured: Under 0.2 MPa, the perimeter was almost not changed;
Under 0.2~0.25 MPa, the perimeter was slightly changed; Under 0.8 MPa, the
perimeter was significantly enlarged, but no burst leaking happened. Another tank
filled with oxidizer to simulate long term storage from propellant filling to launch (no
more than 10 days) with endurance of saturated pressure (maximally no more than
0.2 MPa). After 10 days of storage with 0.2 MPa, if it was examined to be normal, the
pressure was enhanced to 0.3 MPa for 10 days. Finally, the tank conducted expulsion
test normally. The pressure drop, expulsion efficiency and overturn times of metal
diaphragm satisfied the requirements.
8.5.4 Long-Term Pressure-Bearing Storage Test of Gas Tank
Gas tank of propulsion subsystem for the lunar lander was used to store pressurized
gas for propellant expulsion. Because of mass constraints, gas tank of high pressure,
light weight and composite wrapped structure was widely used. Besides leak test,
vibration, shock, thermal vacuum, thermal circle, fatigue and burst pressure tests,
in terms of ground storage time after gas filling and operation time in orbit, it was
also necessary to validate long term pressure-bearing capability and reliability. For
example, composite wrapped gas tanks (aluminum inner) with 1.5 of safety factor,
35 MPa of working pressure, 100 L of volume and T1000 wrapping materials was
applied in propulsion subsystem of the Chang’E-3 lunar lander. In order to simulate
storage process from filling to launch, one gas tank was used to store helium for
41 days with 35 MPa pressure. During the storage process, 6 helium leakage rate
detection were conducted totally with satisfactory results. Long term pressure bearing
capability and reliability were fully verified.
8.5.5 Propellant Filling Test
Propellant filling for the lunar lander was the most critical process in launch
campaign. Because of toxicity of propellant, it couldn’t be verified with real propellant when the flight hardware was developed, examined and tested. Therefore, during
the process of development, special propellant filling test was usually conducted to
assess the consistency and correctness of filling, parameters, safety, ground equipment and etc. For example, evacuation and synchronous equilibrium filling for the
two tanks of same propellant was applied for propulsion subsystem of the Chang’E3 lunar lander. Because there would be NO out of MON-1 oxidizer during vacuum
filling, it was necessary to monitor and control filling temperature, pressure, speed
and etc. Therefore, special propellant filling tests of propulsion subsystem with
different conditions such as different propellant temperatures and filling pressures
were conducted to formulate appropriate filling technical solution in launch site.