47 years ago today, Apollo 1 died, along with her crew: Gus Grissom, Ed White, and Roger Chaffee. It was to be the first launch of the Apollo Program, and the 3 crew members were doing a test on the pad. The mission was a low Earth orbital test, the first with the complex Apollo command module.

On January 27th, 1967, the crew were doing a “plugs out” test, where they tested that the command module would work without being connected to umbilicals and cables. The cabin interior was pressurized with a pure oxygen atmosphere, at a pressure slightly higher than outside air pressure. There was a voltage spike at 6:30 am, and shortly afterwards Chaffee exclaimed “Hey!”, and “I’ve got a fire in the cockpit!”. 17 seconds later, the transmission ceased as the command module ruptured.

There were multiple places where there could have been an ignition source, but later tests showed that the astronauts in nylon pressure suits, reclining on nylon flight seats and moving around normally could have generated enough electrical charge that touching the metal control panels would cause a spark.

The pressurized, pure oxygen atmosphere also contributed to the fire. Many materials become highly flammable in these circumstances. There were about 70 pounds of nonmetallic flammable material in the cockpit.

Further, the hatch was designed to not open if the cabin was at higher than atmospheric pressure. So the crew was unable to open the hatch without venting the extra pressure first, and the vent controls were near where the fire started.

While the mission never happened, and at the time the spacecraft was called AS-204, the designation was changed to Apollo 1: first manned Apollo Saturn flight – failed on ground test.