A continuous-wave CO2 laser has been selected as a source of heat for testing the thermal response of carbon-cloth phenolic like that used as insulating material in a reusable solid-fuel rocket motor (RSRM). The particular thermal response of interest, observed during operation of an RSRM, is pocketing. By suitable adjustment of the size and power of the laser beam, the rate of heating can be made nearly identical to that in the RSRM nozzle during operation.
The use of the laser as the source of heat in such testing is accompanied by the use of optical means to measure the surface temperatures of specimens. The surface-temperature measurements make it possible to construct better mathematical models and develop better understanding of the thermal response of the material under test. Moreover, unlike the environment in a test motor during operation, the environment in the vicinity of a laser-heated specimen is not dominated by hot chemicals in high concentrations; as a result, additional instrumentation that cannot be used in tests in an operating rocket engine can be used in laser-heating tests.
This work was done by Timothy N. Johnson and Edward C. Mathias of Thiokol Corp. for Marshall Space Flight Center. MFS-31272