Four RS-25 engines will power the core stage of NASA’s Space Launch System (SLS), which will carry humans deeper into space than ever before. The RS-25 engine is a modified space shuttle main engine, which powered 135 missions into low-Earth orbit from 1981 to 2011. Remaining space shuttle main engines are being upgraded to provide the additional thrust needed for the SLS vehicle. Credit: NASA #nasa #RS25 #engines #testing #slsfiredup #sls #engineering #technology #rocketscience