8.5 Testing and Verification of Propulsion Subsystem
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ground hot firing was an irreplaceable test using real propellant to fire instead of
simulant to simulate (also known as cold test).
Basic concept for subsystem ground hot firing was that the configuration of propulsion subsystem (layout, pipeline orientation, interface, parameters, propellant load,
gas tank pressure and etc.) was quite the same as that of flight hardware, and the
orbit/attitude control engines were short nozzle version to adapt ground test without
changing internal process of engines. The test procedures and conditions would simulate operation characteristics during different flight phases. The combustion chamber
pressure of orbit/attitude control engines was measured to acquire static thrust or
pulse impulse. The tank expulsion efficiency, system mixture ratio and equilibrium
expulsion of parallel tanks could be evaluated by weighting residue propellant after
test. Generally the parameters measurement and control procedures of test were
simulated by ground test facility, otherwise the TT&C and control subsystem of the
lunar lander could be applied. Test articles were installed and fixed on ground test
facility. For subsystem reliability test, before test the test articles should also pass
vibration test under propellant loading (actual loading simulant) to evaluate structural
reliability during launch.
Because of complexity, challenge and new technology for propulsion subsystem
of the lunar lander, there were usually 2 or 3 subsystem hot firing tests during different
phases when the lunar lander was developed. For propulsion subsystem of manned
the lunar lander, 1 or 2 additional test should be conducted to adequately validate
function, performance, reliability, safety of the subsystem. For example, because
the propulsion subsystem the Chang’E-3 lunar lander was totally new with great
challenges in new technology, requirements and complexity, three hot firing test
had been conducted in phases A(concept design), B/C(design and fabrication) and
D(system AIT) respectively to examine and verify the subsystem operation.
8.5.2 Throttling Engine Test
The Throttling orbit control engine was the most critical component of the propulsion
subsystem of the lunar lander. It served for orbit control in different flight phases,
especially in powered descent. In case of ignition failure, flameout or shutdown
failure, it would lead to mission failure. Because the throttling engine with large
throttling ability, high performance and reliability was new to China space industry,
it was necessary to be verified fully by ground test and high altitude simulation test.
For example, a great many tests for performance, margin, reliability and lifetime
were conducted for the 7500 N throttling engine of propulsion subsystem of the
Chang’E-3 lunar lander as follows.
1. Test Deviated from Normal Conditions
Input pressure (1.6~1.9 MPa) and mixture ratio (1.6~1.7) were deviated from nominal
values (1.7 MPa for input pressure and 1.65 for mixed ratio) in 7500 N engine test.
Thrust was deviated up to 9000 N and down to 1200 N respectively and mixture ratio
297
ground hot firing was an irreplaceable test using real propellant to fire instead of
simulant to simulate (also known as cold test).
Basic concept for subsystem ground hot firing was that the configuration of propulsion subsystem (layout, pipeline orientation, interface, parameters, propellant load,
gas tank pressure and etc.) was quite the same as that of flight hardware, and the
orbit/attitude control engines were short nozzle version to adapt ground test without
changing internal process of engines. The test procedures and conditions would simulate operation characteristics during different flight phases. The combustion chamber
pressure of orbit/attitude control engines was measured to acquire static thrust or
pulse impulse. The tank expulsion efficiency, system mixture ratio and equilibrium
expulsion of parallel tanks could be evaluated by weighting residue propellant after
test. Generally the parameters measurement and control procedures of test were
simulated by ground test facility, otherwise the TT&C and control subsystem of the
lunar lander could be applied. Test articles were installed and fixed on ground test
facility. For subsystem reliability test, before test the test articles should also pass
vibration test under propellant loading (actual loading simulant) to evaluate structural
reliability during launch.
Because of complexity, challenge and new technology for propulsion subsystem
of the lunar lander, there were usually 2 or 3 subsystem hot firing tests during different
phases when the lunar lander was developed. For propulsion subsystem of manned
the lunar lander, 1 or 2 additional test should be conducted to adequately validate
function, performance, reliability, safety of the subsystem. For example, because
the propulsion subsystem the Chang’E-3 lunar lander was totally new with great
challenges in new technology, requirements and complexity, three hot firing test
had been conducted in phases A(concept design), B/C(design and fabrication) and
D(system AIT) respectively to examine and verify the subsystem operation.
8.5.2 Throttling Engine Test
The Throttling orbit control engine was the most critical component of the propulsion
subsystem of the lunar lander. It served for orbit control in different flight phases,
especially in powered descent. In case of ignition failure, flameout or shutdown
failure, it would lead to mission failure. Because the throttling engine with large
throttling ability, high performance and reliability was new to China space industry,
it was necessary to be verified fully by ground test and high altitude simulation test.
For example, a great many tests for performance, margin, reliability and lifetime
were conducted for the 7500 N throttling engine of propulsion subsystem of the
Chang’E-3 lunar lander as follows.
1. Test Deviated from Normal Conditions
Input pressure (1.6~1.9 MPa) and mixture ratio (1.6~1.7) were deviated from nominal
values (1.7 MPa for input pressure and 1.65 for mixed ratio) in 7500 N engine test.
Thrust was deviated up to 9000 N and down to 1200 N respectively and mixture ratio