Gemini 3 was the first crewed mission in (National Aeronautics and Space Administration) NASA's Gemini program. On March 23, 1965, astronauts Gus Grissom and John Young flew three low Earth orbits in their spacecraft, which they nicknamed Molly Brown. This was the ninth crewed US spaceflight (including two X-15 flights over 100 kilometers), and the 17th world human spaceflight including eight Soviet flights. It was also the final crewed flight controlled from Cape Kennedy Air Force Station in Florida before mission control functions were shifted to a new control center located at the newly opened Manned Spacecraft Center in Houston, Texas.

The mission's primary goal was to test the new, maneuverable Gemini spacecraft. In space, the crew fired thrusters to change the shape of their orbit, shift their orbital plane slightly, and drop to a lower altitude. Other firsts were achieved on Gemini 3: two people flew aboard an American spacecraft (the Soviet Union launched a three-person crew on Voskhod 1 in 1964 and a two-person crew just a few days earlier on Voskhod 2, upstaging the two-person Gemini and three-person Apollo programs), and the first crewed reentry where the spacecraft was able to produce lift to change its touchdown point.

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