43K views · 1.5K reactions | Don’t miss this ! In less than an hour, we will fire up one of four RS-25 engines that will thrust our NASA's Space Launch System rocket to deep space destinations like the Moon and Mars at a speed of 17,500 mph — that’s 73 times faster than an Indy 500 race car! What's an RS-25? Watch and find out: https://go.nasa.gov/2IJzrP8 | NASA - National Aeronautics and Space Administration | Facebook