Mercury-Redstone 1

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. 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 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 and landed about 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. 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." ==Causes of the failure==

Investigation revealed that the Redstone's engine shutdown was caused by two of its electrical cables separating in the wrong order. The control cable was supposed to separate first, followed by the power cable. However, for this launch, the control cable was longer than expected—it was one designed for the military PGM-11 Redstone missile rather than the shorter cable designed for Mercury-Redstone. This control cable had been clamped to compensate for its greater length, but when the vehicle lifted off, the clamping did not work as planned and the control cable separation was delayed, eventually occurring about 29 milliseconds after the power cable had separated. During this brief interval, the lack of electrical grounding caused a substantial current to flow through an electrical relay which was supposed to trigger normal engine cutoff at the end of powered flight. This relay tripped, causing the Redstone to shut off its engine and send a normal cutoff signal to the capsule. Under normal circumstances, when the capsule received this signal during a flight, it would do two things: it would jettison its escape rocket, which was no longer of any use, and after the escape rocket had flown clear, fire the explosive bolts holding the capsule to the booster, for separation. In the case of MR-1, the capsule did jettison the escape rocket as it was designed to, but the separation sequence did not occur. The capsule was designed to suspend this separation until the vehicle's acceleration had almost ceased, so that the capsule would not be hit by a still-accelerating launch vehicle. This would happen when the capsule's acceleration sensors detected an acceleration approaching 0 g, which it would normally experience after the Redstone had shut down and was entering free fall. However, in MR-1, the Redstone was not in free fall but rather sitting supported on the ground. Thus the capsule sensors detected the effect of their own supported weight, which they read as a constant acceleration of 1 g. Because of this apparent acceleration, capsule separation was disabled. The jettison of the escape rocket activated the capsule's parachute recovery system. Since the altitude was below , this system was triggered by its atmospheric pressure sensors and followed its usual sequence, with the drogue parachute deploying first, followed by the main parachute. But because the main parachute was not supporting the capsule's weight, the parachute system did not detect any load on this chute, so it acted as if the chute had failed and deployed the reserve parachute. == Aftermath ==

The Redstone had suffered some minor damage from falling back on the pad, but it could still be used after refurbishment, so it was returned to Marshall Space Flight Center in Huntsville, Alabama, and was held in reserve. A new test flight was scheduled, Mercury-Redstone 1A (MR-1A), which would use a new Mercury-Redstone rocket, numbered MR-3. MR-1's Mercury spacecraft, #2, was undamaged, so it was reused for MR-1A, together with the escape rocket from spacecraft #8 and the antenna fairing from spacecraft #10. To prevent a failure like MR-1's from recurring, subsequent Mercury-Redstones added a grounding strap about long to electrically connect the rocket to the launch pad. This strap was designed to separate from the rocket well after all other electrical connections to the ground had been severed. MR-1 was never used for another flight after its return to Huntsville. It was eventually put on display at the Space Orientation Center of Marshall Space Flight Center. ==Current location==

Mercury spacecraft #2, used in both the MR-1 and MR-1A flights, was displayed at the NASA Ames Exploration Center, Moffett Federal Airfield, near Mountain View, California. As of July 13, 2022, it is now on display at the Cradle of Aviation Museum in Garden City, New York. Other Mercury-Redstone rockets are on display at the U.S. Space & Rocket Center in Huntsville and elsewhere. ==Images==

File:Mg-KSC-61C-181.jpg|Fueling MR-1 in preparation for launch File:Mercury-Redstone 1 launch attempt S63-02651.jpg|MR-1 at the moment of ignition File:Project Mercury-Capsule 2 GPN-2000-000382.jpg|Mercury spacecraft #2 in an unfinished state at Lewis Hangar in 1959 File:Mercury Spacecraft at NASA Ames.JPG|Spacecraft #2, used on both the MR-1 and MR-1A flights, on display at NASA Ames Exploration Center File:Mercury MR1-3.jpg|alt=|Mercury-Redstone 1 at the Cradle of Aviation Museum ==Notes==