Despite a vast list of achievements and honors, Aldrin says he still regrets not getting the opportunity to perform one specific experiment in space, which the 84-year-old revealed in a reddit AMA
After joining the space program in 1963, Aldrin pioneered training techniques underwater to prepare for the for the Gemini missions, which preceded the Apollo missions. "I became the first astronaut to train underwater in neutral buoyancy," he said.
Aldrin was training to use something similar to the jetpack that George Clooney's character used in the movie "Gravity," to move around outside the spacecraft. But the jetpack experiment got canned by NASA before Aldrin could test it in space.
On the Gemini mission in space, on my doctoral thesis at MIT, those techniques were used by Gemini, Apollo and even the space shuttle. But I was very disappointed when it looked like I wouldn't even have a chance to fly in the two-man Gemini program! I was not scheduled to be anything other than the back up crew. A tragedy changed that, and I was a backup pilot on Gemini 9, and then I would be on the primary crew for Gemini 12, the final mission. The #1 air force experiment was on Gemini 9 and 12, but its use was unsuccessful on Gemini 9, and so I became the first astronaut to train underwater in neutral buoyancy. I had been a scuba diver 10 years earlier, and knew that training underwater would be very very effective, and I felt very confident of carrying out the difficult procedures to be able to free-maneuver outside the spacecraft with the equipment (this is what George Clooney's character was doing with the jetpack in Gravity) - unfortunately NASA cancelled that experiment.
Hopefully some of that disappointment was quelled when a few years later, on July 21, 1969, when Aldrin made history by becoming the second person to walk on the surface of moon, following commander Neil Armstrong.
After planting his boots on the moon and looking around the lunar landscape, Aldrin said the first words that came to mind were "magnificent desolation."