On February 8, 1965, Armstrong and Elliot See were announced as the backup crew for Gemini 5, with Armstrong as commander, supporting the prime crew of Gordon Cooper and Pete Conrad. The mission's purpose was to practice space rendezvous and to develop procedures and equipment for a seven-day flight, all of which would be required for a mission to the Moon. With two other flights (Gemini 3 and Gemini 4) in preparation, six crews were competing for simulator time, so Gemini5 was postponed. It finally lifted off on August 21. Armstrong and See watched the launch at Cape Kennedy, then flew to the Manned Spacecraft Center (MSC) in Houston. The mission was generally successful, despite a problem with the fuel cells that prevented a rendezvous. Cooper and Conrad practiced a "phantom rendezvous", carrying out the maneuver without a target.