RS-25 engine which was used during five Space Shuttle missions backs in style. NASA started planned firing tests of flight engines for SLS.
Space Launch System, new NASA rocket for manned missions, will inherit something from last truly outstanding NASA project. It was the propulsion - first reusable rocket engine in history - Aerojet Rocketdyne RS-25. Engine entered service as propulsion of Space Shuttles in 1981 and remained (of course with upgrades and different changes in construction) as propulsion of Space Shuttles until their retirement in 2011. One of most important advantages of RS-25 became reliability what was probably one of reasons for picking RS-25 as future propulsion of SLS. According to Garry Lyles, chief engineer for the Space Launch System:
"During the 30-year run of the Space Shuttle Program, the RS-25 achieved very high demonstrated reliability,"
Of course to meet NASA demands engine would be modernized. It will be equipped in new computer control unit, propellant composition was modified and some parts were made with different materials (also with 3D printing technology). In 2015 NASA started tests of partially modified engines and planned to continue burning tests in 2016. On 10 March 2016 on the A-1 Test Stand at Stennis Space Center engineers started to test flight engines. These engines are remaining from Space Shuttle program and were actually used during STS missions. They will be used in first missions of Space Launch System, including maiden flight in 2018. This moment is very important for NASA and Stennis team. Engines are tested with 109% thrust level; also trials with new computer control unit will be started. For 2017 tests of four RS-25, flight engines for first mission of SLS, is planned, so experience with present tests will be very useful. It seems that new time in NASA, time of SLS, is really getting closer.