Designed by Rocketdyne, the J2 rocket engine was first developed in the early 1950s and eventually installed on the second and third stages of the Saturn V launch vehicle. The J2 engine used hypergolic propellants (cryogenic liquid hydrogen and liquid oxygen) and produced approximately 230,000 pounds of thrust. A cluster of five J2 engines on the second stage of the launch vehicle took over from the stage one’s F1 engines after launch, propelling the Apollo spacecraft into the upper atmosphere. From there, the third stage’s single J2 booster pushed the craft into orbit. The third stage’s J2 fired again before being jettisoned to push the Apollo spacecraft towards the Moon.