Mercury-Atlas 1

The mission was to conduct a suborbital test flight and reentry of the spacecraft. The capsule carried live separation rockets, but dummy retrorockets. Several other systems were not installed, including the cabin pressurization system and the astronaut couch. A number of Mercury engineers had voiced their objection to the launch because the weather would prevent observation of the flight. Some witnesses claimed to have heard an explosion, but this could not be verified. The capsule continued transmitting until it impacted the ocean, approximately 6 miles (9.7 km) downrange. Salvage brought the capsule, Atlas booster engines and LOX vent valve to the surface from the ocean floor. The engines showed no sign of damage except some deformation from impact with the ocean, but the vent valve and a still-attached segment of piping had noticeable fatigue cracks.

Investigation

Telemetry indicated that the Atlas functioned normally up to T+58 seconds and there was no sign of any problems up to that point, when a severe axial disturbance was detected. Approximately one second later, the pressure difference between the RP-1 and LOX tanks dropped to zero followed by loss of engine thrust and telemetry and the appearance of multiple objects on radar. Capsule data indicated violent movements following the loss of booster telemetry, but the Mercury otherwise continued functioning normally until impact with the ocean at around 220 seconds after launch. The automatic abort system appeared to have functioned correctly and issued a shutdown command to the Atlas's engines the moment that it detected an abnormal situation. The parachute system did not deploy because the abort had taken place too early in the launch. Unlike R&D Atlas D missiles, Atlas 50D was not carrying a large complement of telemetry probes; only 50 measurements were taken on this flight. The Atlas appeared to be on a steady flight path when telemetry was lost at T+60 seconds, but the last 1.2 seconds of telemetry data was questionable due to open circuits in the booster following the disturbance. The capsule gyroscope data suggested that the stack had pitched over as much as 10°. There had been two separate disturbances. The first one, at T+58.5 seconds, had caused the instant loss of telemetry measurements in the forward part of the booster. The second disturbance occurred at T+59.4 seconds, following the Abort Sensing and Implementation System (ASIS)-generated engine cutoff. The propulsion system did not appear to be affected by the initial event.