Publication Date:
2019-07-13
Description:
In January 2013 a false ammonia leak alarm resulted in the shutdown and partial depressurization of one of the two International Space Station (ISS) External Active Thermal Control System (EATCS) loops. The depressurization resulted in a vapor bubble of 18 liters in warm parts of the stagnant loop. To repressurize the loop and regain system operation, liquid would have to be moved from the Ammonia Tank Assembly (ATA) into the loop. This resulted in the possibility of moving cold (as low as 30 C) ammonia into the waterfilled Internal Active Thermal Control System (IATCS) interface heat exchangers. Before moving forward, the freezing potential of the repressurization was evaluated through analysis - using both a Thermal Desktop SINDA/FLUINT model and hand calculations. The models yielded very different results, but both models indicated that heat exchanger freezing was not an issue. Therefore, the repressurization proceeded. The presentation describes the physical situation of the EATCS prior to repressurization and discusses the potential limits and pitfalls of the repressurization. The prerepressurization analytical models and their results are discussed. The successful repressurization is describled and the results of a postevent model assessment is detailed.
Keywords:
Spacecraft Design, Testing and Performance
Type:
JSC-CN-33216
,
Thermal & Fluids Analysis Workshop (TFAWS); Aug 03, 2015 - Aug 07, 2015; Silver Spring, MD; United States
Format:
application/pdf
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