Apollo 9 was a full-throttle test of most of the systems that would be needed to land on the Moon. The crew, spacecraft, and systems passed with flying colors.

The crew for this third manned mission to leave the surface of the Earth were Gemini veteran Commander Jim McDivitt (left, center), Gemini veteran and Command Module Pilot Dave Scott (left, left), and Lunar Module Pilot Rusty Schweickart (left, right). They were quite possibly the most well trained of any Apollo crew, logging more than 1,800 hours of mission-specific training.

The original launch date was February 28, but when all three astronauts came down with colds, NASA postponed the launch. Blastoff was on March 3, 1969. The crew spent 10 days in low Earth orbit, performing all manner of tests: of docking and undocking maneuvers, of the engines of the lunar module, of navigation systems, of backpack life support systems. They even threw in a spacewalk, with Schweickart notching 37 minutes of extravehicular activity (EVA).

One of the tests was for one of the crew to climb from one spacecraft to the other. In the all-important rehearsals for the worst case scenario, scientists wanted to be confident that the astronauts could do such a thing if the command module and lunar module wouldn't come together while orbiting the Moon. Schweikart was ill again on the day of the EVA, and so his spacewalk was more of a space-stand and missed out the test of the Portable Life Support System backpack.

For the first time, the crew assigned nicknames to the main modules. The command module they called Gumdrop because it looked like one of the iconic sweets when wrapped up before launch. Spider, the name of the lunar module, was more evident because that craft looked very much like one of Earth's many arachnids.

A big highlight for the crew was on the fifth day of the 10-day mission. McDivitt and Schweikart climbed into Spider and flew the lunar module more than 100 miles away from Gumdrop. In a rehearsal for what astronauts who had walked on the Moon would later do, the lunar module crew then enticed their spacecraft to "rise" again, and they docked safely with Scott in the command module. (This was the second docking test done; the first was while the lunar module was still attached to the remaining stages of the Saturn rocket that launched the spacecraft.)

Their tests finished and 152 orbits completed, the crew returned safety to Earth, splashing down in the Atlantic Ocean on March 13.

Apollo 9 was full of successful tests and gave NASA confidence to build on those successes by testing the maneuvers and systems not only in low Earth orbit but 252,000 miles away, in a flight path around the Moon. The stage was set for Apollo 10.