Encyclopedia Astronautica
1964.05.31 - Gemini orbit attitude and maneuver system thrust chamber assembly designs frozen.


Gemini Program Office (GPO), encouraged by several highly successful tests, reported that all orbit attitude and maneuver system thrust chamber assembly (TCA) designs had been frozen. A 25-pound TCA tested to the 578-second mission duty cycle was still performing within specification requirements after more than 2100 seconds with a maximum skin temperature of 375 degrees F.

An 85-pound TCA accumulated 3050 seconds of mission duty cycle operation with skin temperatures no higher than 320 degrees F. Maximum allowable for either TCA was 600 degrees F. Two tests of the 100-pound TCA were equally successful. The first was terminated after 757 seconds of mission duty cycle operation with a maximum skin temperature of 230 to 250 degrees F. The second ended when fuel was exhausted after 1950 seconds of mission duty cycle operation with a maximum skin temperature of 600 degrees F. GPO attributed the success of these tests to proper injector screening techniques and reorienting the ablation material laminates from vertical to the motor housing (90 degrees) to approximately parallel (6 degrees), both GPO suggestions, and to the boundary-layer cooling technique suggested by Rocketdyne. In May, Rocketdyne released to production the design for the long-duration TCAs. Installation of the new long-life TCAs was planned for spacecraft No. 5, to include the 100-pound aft-firing thrusters and all 25-pound thrusters. A full complement of long-life TCAs was planned for spacecraft No. 6.

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