Mercury-Redstone 1

Mercury-Redstone 1 (MR-1) was the first Mercury-Redstone unmanned flight test in the Mercury program and the first attempt to launch a Mercury spacecraft with the Mercury-Redstone launch vehicle. Intended to be an unmanned sub-orbital flight, it was launched on November 21, 1960 from Cape Canaveral, Florida. The launch failed in a peculiar fashion which has been referred to as the "four-inch flight".

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 did not have a living passenger, this would not pose a safety problem, and it would prevent a faulty abort signal from prematurely ending the flight.