Mercury-Redstone 1 (MR-1) was the first Mercury-Redstone uncrewed flight test in Project Mercury and the first attempt to launch a Mercury spacecraft with the Mercury-Redstone Launch Vehicle. Intended to be an uncrewed sub-orbital spaceflight, it was launched on November 21, 1960 from Cape Canaveral Air Force Station, Florida. The launch failed in an abnormal fashion: immediately after the Mercury-Redstone rocket started to move, it shut itself down and settled back on the pad, after which the capsule jettisoned its escape rocket and deployed its recovery parachutes. The failure has been referred to as the four-inch flight, for the approximate distance traveled by the launch vehicle. Investigators later found that an electrical connector disconnected in the wrong order, causing the rocket to think the flight had ended and shut down its engine.
Test background and launch failure The purpose of the MR-1 flight was to qualify the Mercury spacecraft and the Mercury-Redstone launch vehicle for the sub-orbital Mercury mission. It would also qualify the spacecraft's automated flight control and recovery systems, as well as the launch, tracking, and recovery operations on the ground. The flight would also test the Mercury-Redstone's automatic inflight abort sensing system, which would be operating in open-loop mode. This meant that the abort sensing system could report a condition requiring an abort, but it would be unable to actually trigger an abort itself. Since the flight was uncrewed, this would not pose a safety problem, and it would prevent a faulty abort signal from prematurely ending the flight. The test used Mercury spacecraft #2 together with Redstone MR-1; its launch location was Cape Canaveral Air Force Station's Launch Complex 5. An early launch attempt on November 7 was canceled due to last-minute problems with the capsule, so launching was rescheduled for November 21. On that day, following a normal countdown, the Mercury-Redstone's engine ignited on schedule at 9:00 a.m. Eastern Standard Time (14:00 GMT). However, the engine shut down immediately after lift-off from the launch pad. The rocket only rose about 4 inches (10 cm) before settling back onto the pad. Alarms were immediately sounded at LC-5, but the rocket did not explode. Instead it merely sat in place on the launch pad, after which an unusual sequence of events happened. Immediately after the Redstone's engine shut down, the Mercury capsule's escape rocket jettisoned itself, leaving the capsule attached to the Redstone booster. The escape rocket rose to an altitude of 4,000 feet (1,200 m) and landed about 400 yards (370 m) away. Three seconds after the escape rocket fired, the capsule deployed its drogue parachute; it then deployed the main and reserve parachutes, ejecting the radio antenna fairing in the process. In the end, all that had been launched was the escape rocket. However, the fully fueled and powered-up Redstone was now sitting on LC-5 with nothing securing it to the pad. Various other dangers existed as well, such as the capsule's retrorocket package and the range safety destruct charges. Furthermore, the capsule's main and reserve parachutes were hanging down the side of the rocket, threatening to tip it over if they caught enough wind; this did not occur, however, as the weather conditions were favorable. Amid the panicked atmosphere in the control room, the launch team was unable to come up with quick and viable options to rectify the situation. Flight director Chris Kraft rejected several unsafe interventions, including using a rifle to shoot holes in the booster's propellant tanks to depressurize them. He eventually took the advice of one of the test engineers to simply wait out the battery discharge and let the oxidizer boil off. This early test failure and subsequent panic led Kraft to declare "That is the first rule of flight control. If you don't know what to do, don't do anything." Technicians therefore waited until the next morning, when the flight batteries in the rocket and capsule had drained and the Redstone's liquid oxygen had boiled off, before they could work on the rocket and render it safe.
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