60K views · 1.2K reactions | At 3:40 pm ET, we'll fire up one of the four RS-25 engines for NASA's Space Launch System, our rocket built for deep-space missions to the Moon and Mars. Today's test features an RS-25 flight controller set for use on an actual mission, engine components made with innovative manufacturing, and plenty of  and . Watch: https://www.nasa.gov/live | NASA - National Aeronautics and Space Administration | Facebook