Cold conditioning system
NASA's Space Launch System (SLS) is the biggest, most capable rocket ever built for human exploration. As with every rocket program, the heavy lifting starts on the ground, where development and qualification motors are thoroughly tested before first flight. SLS development followed a five-test protocol that began in 2009, and culminated with the final, successful qualification test of the QM-2 last year. This final test included 82 qualification objectives. Among the most important of these was the evaluation of solid rocket motor performance at its low temperature range of 40 °F, ±2 °F.
Orbital ATK chose Aggreko to provide the cold conditioning system to reduce propellant mean bulk temperature (PMBT) from its initial 73 °F down to a test-ready PMBT of 40 °F. The 12-foot-diameter, 154-foot-long, five-segment rocket was housed in Orbital ATK's T-97 test facility in Promontory, UT. This freestanding, movable enclosure was built on an electrically driven rail system.
Aggreko helped Orbital ATK design a temporary, portable solution for temperature control and power generation. At the heart of the system were two 200-ton, low-temperature mechanical chillers, and two pumps used to deliver a 50% propylene glycol solution to the air handling units (AHUs). Three sets of two 120-ton AHUs circulated cold air to the enclosure. The tandem arrangement allowed one AHU to deliver chilled air while the other operated in defrost mode. An additional AHU dehumidified and cooled outside air to maintain positive pressure in the enclosure. Behind it all was a temporary power system designed for two purposes. The first was to power the distribution panel for the chillers and pumps. The second was to provide backup power for three three-phase, 480-VAC power stanchions for the AHUs. Aggreko provided two containerized 500-kW generators and cabling to meet these requirements.
Once the systems and personnel were in place, the conditioning started at 80 days prior to test. The required PMBT was achieved in approximately 64 days. Ultimately, the motor and propellant were successfully delivered for the test at 40 °F, within the specified temperature range.
QM-2 was the final ground test before Exploration Mission 1 — the first planned flight of the SLS scheduled for late 2018. The test provided critical data that demonstrated nozzle, ballistics, and other design performance parameters met requirements at the design temperature of 40 °F. The QM-1 test, as well as the design motor tests, also employed Aggreko temperature and power generation systems.
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