A premature engine shutdown caused this U.S. practice Moon mission fall back to the launch pad and explode.
This mission was designed to rehearse a complete Centaur upper stage burn in support of the Surveyor lunar lander program. On a nominal mission, the Centaur would boost its payload on a direct ascent trajectory to the Moon.
On this test flight, NASA planned to deliver the payload, a non-functional dynamic model known as SD-1, into an orbit of 104 x 575,780 miles (167 x 926,625 kilometers) that simulated a lunar transfer trajectory.
During the actual launch, less than 2 seconds after liftoff, a faulty valve that incorrectly closed caused both Atlas main engines to shut down. As a result, the booster fell back onto the pad and exploded.
Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.