In addition, they used pyrotechnic cartridges for rapid starting and the gas generators and pumps were mounted on each booster engine instead of being placed in the central thrust section.

This setup was designed for ease of service and engine swapping in the field, while the Atlas D's simpler configuration was considered preferable for space launches.

Atlas 6F performed acceptably until after booster jettison when a hydraulic failure caused loss of sustainer thrust.

The capsule separated and splashed down near Ascension Island in the South Atlantic, however the tracking beacon failed to operate and recovery crews could not locate it.

[3] So far, the Atlas F test program had gone well and nobody was prepared for the upcoming disaster on April 9, 1962 when Missile 11F exploded only one second after liftoff from LC-11.

Examination of recovered missile parts found that some sort of explosion or detonation in the sustainer turbopump had occurred.

The investigation team concluded that a slight delay opening the HS valve in the sustainer engine had occurred; the turbopump was spinning at its maximum speed of 10,000 RPM which resulted in excessive stress on it.

The pitch sequence was executed properly, but the lack of the roll program prevented the missile from attaining the correct trajectory and it was blown up by Range Safety 67 seconds into the launch.

[5] The next test launch took place from the now-repaired LC-11 at the Cape two days later and all subsequent R&D flights went without a hitch except for 13F on November 14 which experienced a thrust section fire beginning at T+18 seconds.

The flight of 52F on March 24 ended in an abrupt explosion 90 seconds after launch and the minimal instrumentation onboard was insufficient to provide any explanation.

Tracking camera film showed that the missile was on the proper flight path and no other obvious indications of trouble were visible.

An ABRES test from LC-11 at Cape Canaveral on October 28 using Missile 136F failed when the sustainer engine lost hydraulic pressure at staging and tumbled.

The B-1 engine experienced a stuck main fuel valve and did not start, once again the missile fell over and exploded on impact with the ground.

GD/A issued a service bulletin to all Atlas silo crews to make sure missiles were properly checked and free of hypergol residue.

[7] A glob of gelled LOX and kerosene fell into the flame pit at ignition, exploded, and damaged the Atlas's sustainer engine.

The launch vehicle continued to operate for over two minutes, but the sustainer and verniers eventually shut down and the range safety destruct command was issued at T+303 seconds.

Since the LOX gel explosion also damaged wiring in the base of the booster, the telemetry system lost power and no data was returned during launch, making it difficult to determine the exact cause of the engine failure.

The failure was caused by a seal jostled loose by the rapid-fire pyrotechnic cartridge ignition system used in the Atlas E/F missiles, flooding the B-1 turbopump with fuel and slowing down its rotation speed, cutting thrust levels in the engine to 80% and considerably reducing booster velocity and fuel consumption.

However, for simplicity reasons, the NOAA satellite had no electrical interface with the Atlas, which caused it to fire its posigrade rockets at a pre-set time.