On March 24, 1961, NASA's Mercury Redstone rocket launched on its last uncrewed flight before it started sending astronauts into space. [‘On This Day in Space’ Video Series on Space.com](https://www.space.com/39251-on-this-day-in-space.html)

The mission was known as the Mercury Redstone Booster Development flight, and it wasn't originally planned as part of the Mercury Program. The previous Mercury Redstone flight carried a chimpanzee named Ham into space. Ham made it back alive, but the rocket had several issues during the flight. So, NASA made some changes to the design and tested it one more time to make sure it was safe enough for human astronauts. The Mercury Redstone rocket lifted off from Cape Canaveral and traveled more than 300 miles downrange before splashing into the Atlantic Ocean. The mission was deemed a success and cleared the way for Al Shepard's historic first flight to space.