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5 Thermal Control Technology of Lunar Lander
to achieve vacuum condition with lower cost. The wind tunnel heating method could
simulate the temperature response of the actual operation of the engine, but the test
system was complicated and it was difficult to maintain vacuum condition near the
test article. Furthermore, the duration of test was limited and the cost was high.
After various factors were considered comprehensively, it was more reasonable and
feasible to use a high-power quartz lamp or other similar electric heating source to
simulate the high temperature boundary of the engine.
The heat flux obtained on the surface of heat shield (second type boundary condition) could be simulated in the heat insulation performance test. Because the high
temperature of the engine resulted in rapid temperature raise of the heat shield surface
and the temperature was stable during the engine firing, as well as the main objective
of the test was to examine the overall thermal insulation properties of heat shield,
it was also possible to simulate the surface temperature of heat shield (first type
boundary condition). For the quartz lamp heating method, because the response
time was slower than the wind tunnel, it was suitable for simulating the temperature
response process of heat shield surface. In addition, the temperature measurement
was simpler and more accurate than measurement of high temperature heat flux.
Based on the above analysis, it was more feasible to simulate the surface temperature condition of heat shield in the vacuum performance test with quartz lamp
heating.
3. Status of Test Article and Working Conditions
The composition of test article for the high-temperature heat shield should be consistent with the design status. For the parts with different composition, special test pieces
should be made separately. In order to examine the influence of joint and fastened
methods on temperature, special test pieces should be manufactured for testing.
The joint status and fastened method should be consistent with the design status.
High-temperature heat shield was generally symmetrically configured to the engine.
Therefore, the surface temperature conditions were uniform. At the same time, the
lateral heat transfer of heat shield was poor and the edge effect was not obvious.
So, the temperature distribution and temperature response in the thickness direction
could be accurately obtained with a mall area. The specific size of the test articles
should be determined according to the size of effective heating area of quartz lamp,
so as to avoid the accuracy of test results affected by non-uniform heat flux.
In order to obtain temperature distribution in the thickness direction, a plurality
of temperature measurement points should be arranged in the thickness direction,
wherein a temperature measurement point should be arranged on the surface facing
the heat source for controlling the test temperature. The temperature sensor should
adapt to the highest temperature during the test, and in order to reduce the heat
leakage, the temperature sensor with wire of small diameter should be chosen generally. After the quartz lamp works, the temperature of the test piece would rise rapidly,
and the sampling frequency of temperature measurement system should be higher
than 1 Hz.
In order to simulate the pressure on orbit, the test system should be placed in space
environment simulator (as shown in Fig. 5.18). Before the test, in order to empty the
5 Thermal Control Technology of Lunar Lander
to achieve vacuum condition with lower cost. The wind tunnel heating method could
simulate the temperature response of the actual operation of the engine, but the test
system was complicated and it was difficult to maintain vacuum condition near the
test article. Furthermore, the duration of test was limited and the cost was high.
After various factors were considered comprehensively, it was more reasonable and
feasible to use a high-power quartz lamp or other similar electric heating source to
simulate the high temperature boundary of the engine.
The heat flux obtained on the surface of heat shield (second type boundary condition) could be simulated in the heat insulation performance test. Because the high
temperature of the engine resulted in rapid temperature raise of the heat shield surface
and the temperature was stable during the engine firing, as well as the main objective
of the test was to examine the overall thermal insulation properties of heat shield,
it was also possible to simulate the surface temperature of heat shield (first type
boundary condition). For the quartz lamp heating method, because the response
time was slower than the wind tunnel, it was suitable for simulating the temperature
response process of heat shield surface. In addition, the temperature measurement
was simpler and more accurate than measurement of high temperature heat flux.
Based on the above analysis, it was more feasible to simulate the surface temperature condition of heat shield in the vacuum performance test with quartz lamp
heating.
3. Status of Test Article and Working Conditions
The composition of test article for the high-temperature heat shield should be consistent with the design status. For the parts with different composition, special test pieces
should be made separately. In order to examine the influence of joint and fastened
methods on temperature, special test pieces should be manufactured for testing.
The joint status and fastened method should be consistent with the design status.
High-temperature heat shield was generally symmetrically configured to the engine.
Therefore, the surface temperature conditions were uniform. At the same time, the
lateral heat transfer of heat shield was poor and the edge effect was not obvious.
So, the temperature distribution and temperature response in the thickness direction
could be accurately obtained with a mall area. The specific size of the test articles
should be determined according to the size of effective heating area of quartz lamp,
so as to avoid the accuracy of test results affected by non-uniform heat flux.
In order to obtain temperature distribution in the thickness direction, a plurality
of temperature measurement points should be arranged in the thickness direction,
wherein a temperature measurement point should be arranged on the surface facing
the heat source for controlling the test temperature. The temperature sensor should
adapt to the highest temperature during the test, and in order to reduce the heat
leakage, the temperature sensor with wire of small diameter should be chosen generally. After the quartz lamp works, the temperature of the test piece would rise rapidly,
and the sampling frequency of temperature measurement system should be higher
than 1 Hz.
In order to simulate the pressure on orbit, the test system should be placed in space
environment simulator (as shown in Fig. 5.18). Before the test, in order to empty the