A programme forced to stop and rebuild
The fire on 27 January 1967 ended the first planned crewed Apollo flight before it began. The immediate result was a halt in crewed Apollo flights that lasted until Apollo 7 carried its crew into Earth orbit on 11 October 1968, about 20 months later. The Gemini programme had finished in November 1966, so the United States made no crewed spaceflights in 1967, and the Soviet Union made only one, ending with the loss of Vladimir Komarov in April.
The delay was not simply a pause. It was a period of redesign, retesting and reorganisation that changed the programme, and it is the main reason that the spacecraft which later flew to the Moon was much safer than the one that sat on Pad 34.
Block I and Block II
The spacecraft involved in the fire was an early version, known as Block I. It was intended for Earth-orbit tests and was not designed to go to the Moon. A later version, Block II, was already in development and was meant to be the lunar-capable spacecraft, with provision for docking with the lunar module.
After the fire NASA decided that crewed flights would wait for a spacecraft that incorporated the lessons of the investigation. In practice this meant that the Block II design, with major changes, became the standard. The spacecraft that flew crews from Apollo 7 onward was a Block II command module, heavily modified from the original plan. A few remaining Block I spacecraft were used only for uncrewed test flights.
The new hatch
The most visible change was the hatch. The earlier design used an inner hatch that opened inward and had to be released by a sequence of manual operations, with a separate outer cover. The new design replaced these with a single hatch that opened outward, was held by a latch mechanism that could be released quickly, and could be operated from inside or outside. It was also designed so that the pressure inside the cabin would help to hold it closed during normal flight, while still allowing it to be opened rapidly in an emergency. Engineers aimed for an opening time of roughly ten seconds or less, rather than the minute or more needed before.
The final design was tested extensively. The point of the redesign was not to promise that no fire could ever occur, but to ensure that a crew had a realistic chance of leaving the spacecraft quickly if one did.
Materials, wiring and the cabin atmosphere
The second major area was flammability. Engineers went through the cabin and replaced or covered combustible items. Nylon and other easily ignited fabrics were replaced by fire-resistant materials, including glass-fibre cloth with a protective coating. Velcro and similar items were reduced and, where they had to stay, were placed so that a fire could not spread easily. Wiring was rerouted, shielded and protected, and plumbing that carried flammable coolant was redesigned.
The cabin atmosphere was changed in procedure. On the launch pad the cabin would contain a mixture of oxygen and nitrogen rather than pure oxygen at high pressure. In orbit the spacecraft would operate on pure oxygen at a much lower pressure, about a third of normal air pressure, and the mixture would be converted to oxygen alone gradually after launch. This approach kept the weight and simplicity of a single-gas system in space while avoiding the most dangerous condition, which was a pressurised pure oxygen cabin on the ground.
Alongside the hardware, NASA also tightened its test procedures, firefighting arrangements and quality control, and made changes to how it worked with its contractors. The company that built the command module, North American Aviation, and NASA’s own managers faced hard questions in congressional hearings. George Low took over management of the Apollo spacecraft programme office in spring 1967, and he is often credited with driving the redesign forward.
Flights that rebuilt confidence
Meanwhile the programme continued with uncrewed flights. The first Saturn V test, Apollo 4, flew in November 1967 and demonstrated both the giant rocket and the command module’s heat shield. Further uncrewed flights followed in 1968, including a lunar module test and a second Saturn V flight that suffered problems, before NASA felt confident enough to put a crew on board. Apollo 7, commanded by Wally Schirra with Donn Eisele and Walt Cunningham, spent nearly 11 days in orbit in October 1968 and tested the new command module thoroughly.
The effect on the Moon schedule
The redesign cost time, but the larger consequence was that it forced the programme to take the remaining steps in a careful order. Apollo 8 flew around the Moon in December 1968, and later missions tested the lunar module in Earth orbit and then in lunar orbit before the landing of Apollo 11 in July 1969. The decade deadline was met with a few months to spare, though it had looked uncertain for much of 1967.
It is hard to be sure how the programme would have gone without the fire. Many who worked on Apollo later argued that the delay, painful as it was, produced a better spacecraft, and that the discovery of hidden hazards on the ground was preferable to finding them far from Earth.