NASA readies for another test of SLS’s core propulsion system
NASA is preparing to conduct a full-duration static test fire of one of its RS-25 engines on Thursday, August 18, four of which will comprise the propulsion system in the agency’s Space Launch System (SLS) heavy-lift rocket. Previously known as the Space Shuttle Main Engine (SSME), the uprated engine will initially provide up to 109% of its original design thrust in early iterations of SLS, with a goal of eventually being rated for 111%.
When the engines were used on the Space Shuttle, they were rated for nominal use at 104.5%, though could be throttled up to 109% in the event of an abort scenario. However, doing so ran the risk of significant degradation of engine components, perhaps to the point of making it not cost-effective to refurbish the engine. That’s not a concern with SLS, though, as the core stage will not be recovered after use.
In order to consistently run the engine at the higher performance levels, Aerojet Rocketdyne – the manufacturer of the SSME/RS-25 engine – needed to upgrade the engine controller. The now-mothballed J-2X engine, also manufactured by Aerojet Rocketdyne, provided the perfect platform from which to develop the engine control module for the RS-25. Numerous development test firings have validated the new controller, as well as other changes to the engine, and NASA now moves forward with running the flight engines through mission-like static fire tests in preparation for the maiden launch of SLS, scheduled for the latter half of 2018.