In the early 1960s, NASA decided it needed landers on the Moon for a more detailed analysis of the lunar surface, including examining the rocks and taking more detailed pictures to identify potential landing sites for the future Apollo landings, than were possible from spacecraft in lunar orbit.
The spacecraft developed for this mission was Surveyor, a small triangular lander with three legs at the points of the body. The whole craft weighed 340 kilograms, but the spacecraft structure itself was only 27 kilograms. Sixty percent of the mass of Surveyor was a large solid motor, which did most of the work to slow the spacecraft down for lunar landing. A concern at the time was that the lunar surface would turn out to be like sand, causing a heavier lander to sink. Surveyor measured the force of the surface pushing back upon landing, which confirmed that the lunar surface could support a heavy lander.
The rocket for Surveyor was the new Atlas-Centaur, which was also being tested. Yes, NASA was testing both a rocket and a spacecraft at the same time. Two test flights of the rocket carrying Surveyor mockups failed. The second test flight with a Surveyor, which was the fifth Atlas-Centaur overall, failed only a few moments into launch when a bad valve accidentally shut down the rocket’s booster engines, causing it to fall back down onto the launch pad and explode. No one was injured, but the launch complex was badly damaged, and it took engineers a year to repair it.
Centaur was the first upper stage to use liquid oxygen and liquid hydrogen, two very cold and temperamental propellants which have a habit of escaping their tanks. These propellants are commonly used today without much issue but not without blowing up a few rockets on the way. The insulation needed to keep the cryogenic fuel cold had a habit of falling off before intended, causing the rocket to literally rip in half before exploding. Four out of five test flights were unsuccessful because of problems ranging from engine underperformance to design flaws. Thanks to the persistence of NASA engineers, those pesky performance problems were solved. The Centaur flies today on Atlas’ distant cousin Atlas V with a nearly flawless record.
The sixth test flight finally succeeded in placing a Surveyor mockup in exactly the right trajectory for a lunar landing, had it completed a midcourse correction. This cleared the combination for an operational mission: Surveyor 1.
Despite all of these previous failures – you know, rockets crumpling in half or colliding into the launch pad – the Atlas-Centaur and the first-ever real Surveyor spacecraft performed flawlessly, becoming the first spacecraft to do a true soft landing on the moon in May 1966. Unfortunately, that luck would not extend to the Surveyor 2 mission.
Surveyor 2 launched on September 20, 1966, at 12:32 UTC on an Atlas-Centaur rocket from LC-36A at Cape Canaveral. Launch and translunar injection were nominal, confirming the problems with Centaur were finally resolved. Unfortunately, during a midcourse correction burn, one of the three landing engines failed to ignite for an unknown reason and the spacecraft went into a spin.
NASA engineers tried 39 times to get the engine to ignite but were unsuccessful. Still spinning, Surveyor 2 started up its engines for the final landing burn. The onboard computer tried to stop the spin but was unsuccessful. Two days after launch, Surveyor 2 impacted the moon southeast of Copernicus Crater. Communications ceased shortly after the landing burn began.
Fortunately, later Surveyor missions 3, 5, 6, and 7 successfully landed on the Moon and returned loads of information about its surface. Thanks to the flights of the Surveyor program and the data gathered, all attempted Apollo landings were successful.