Progress towards Exploration Mission-1 continued this month with the completion of work on the four RS-25 engines that will be used to power SLS in its launch of Orion to the Lunar orbit. This milestone marks the last step before the integration of these four engines on the core stage of SLS for the "green run" testing.
In its announcement, NASA noted that: "The flight preparations for the four engines that will power NASA’s Space Launch System (SLS) on its first integrated flight with Orion are complete and the engines are assembled and ready to be joined to the deep space rocket’s core stage. All five structures that form the massive core stage for the rocket have been built including the engine section where the RS-25 engines will be attached.
"The SLS has the largest core stage ever built and includes four RS-25 engines, which previously powered NASA’s space shuttle. The RS-25 engines that are being tested and prepared for SLS were proven during the years they were responsible for propelling 135 shuttle missions, and have been upgraded for the first SLS flight. The four that will fly on Exploration Mission-1 supported a total of 21 shuttle missions.
"In total, NASA has 16 flight-proven RS-25 engines and two development engines that are being used as “workhorse” engines for testing. These engines have been used to test new controllers – the brains of the engine – which have now been installed on the flight engines. The flight engines will be attached to the core stage to prepare for green run testing – the final test for the four flight engines and the core stage that will occur before the first mission."