The Apollo 1 mission — formally AS-204 — was scheduled to be the first crewed flight of the new Apollo Command and Service Module spacecraft, with launch planned for 21 February 1967 from Launch Complex 34 at Cape Kennedy. The crew were the Mercury and Gemini veteran Virgil “Gus” Grissom (40, command pilot), the Gemini IV spacewalker Ed White (36, senior pilot), and the rookie astronaut Roger Chaffee (31, pilot).

The 27 January 1967 test — a “plugs-out” test in which the spacecraft was on internal power and disconnected from ground systems — was a rehearsal of the full launch countdown without actual launch. The Saturn IB launch vehicle below the Apollo Command and Service Module was not fuelled. The test was classified as non-hazardous. There were no firefighters or medical personnel positioned at the pad.

The cabin atmosphere for the test was 100 percent oxygen at 16.7 psi (approximately 115 kPa). The slightly-above-sea-level pressure was used during ground tests to simulate the small positive pressure differential the cabin would maintain in space. Pure oxygen at that pressure has very different combustion properties from normal air — many materials that resist combustion in ordinary atmosphere burn explosively in pure oxygen.

The cabin contained substantial quantities of nylon webbing, Velcro fasteners, paper checklists, and polyurethane foam padding. All were standard spacecraft outfitting. The combination of pure oxygen at elevated pressure with the available fuel load was, in retrospect, an extreme fire risk. Pre-1967 NASA pure-oxygen fire risk assessments had not adequately considered the combined load.

The countdown problems

The countdown ran approximately five hours into the planned full mission profile by approximately 6:00 p.m. on 27 January 1967. The crew were strapped into their couches in launch position. Multiple intermittent communications problems with the spacecraft-to-ground audio link had been frustrating Grissom for most of the afternoon. He had said over the audio loop a few minutes before the fire, audibly exasperated: “How are we going to get to the moon if we can’t talk between two or three buildings?”

At 6:30:54 p.m. local time the cabin voltage telemetry showed a brief spike — probably a short circuit in worn wiring beneath Grissom’s couch on the cabin floor. The exact source has never been definitively identified.

At 6:31:04 p.m. the spacecraft instrumentation registered a fire warning. Chaffee reportedly said over the open audio loop, “Fire!” or “We’ve got a fire in the cockpit” — the audio is unclear and has been transcribed differently in different sources.

The fire spread across the cabin floor and the right-hand wall within approximately two seconds. The internal pressure rose rapidly as the fire consumed oxygen and produced gaseous combustion products. By approximately 6:31:14 p.m. — 10 seconds after the initial fire warning — the internal pressure had exceeded the cabin’s outward-pressure structural limit. The cabin ruptured at a structural weak point on the lower right hull.

The cabin rupture is the moment at which the substantially pressurised internal atmosphere blew out into the white-room (the platform-level workspace at the launch tower). The rupture sprayed flame and combustion gases across the white-room platform and forced the launch-tower workers backwards. The Apollo Command Module hatch — which would have needed about 90 seconds to remove in normal conditions — could not be approached for approximately 5 minutes after the rupture because of the heat and smoke.

The crew were dead by the time the hatch was reached.

The hatch

The Apollo 1 hatch was an inward-opening three-part assembly. The inner door (the “boost protective cover” / “BPC”) was lifted off and stowed; the middle pressure hatch was unlatched from inside, lifted, and stowed; the outer hatch could then be opened by the ground crew. The full sequence required about 90 seconds with the crew working from inside. The hatch had no provision for emergency egress under the conditions that obtained at 6:31 p.m. on 27 January 1967.

The inward-opening hatch design had been a deliberate post-Mercury choice. Grissom’s previous Mercury Liberty Bell 7 capsule had used an outward-explosive-bolt hatch that had blown prematurely after splashdown in 1961, sinking the capsule and almost drowning Grissom. The Apollo design team had specified a non-explosive inward-opening hatch substantially to prevent that failure mode. The 1967 fire produced exactly the opposite failure: the inward-opening hatch could not be opened against the internal pressure spike.

The post-Apollo-1 redesign — introduced for Apollo 7 (October 1968) and used for the remainder of the Apollo programme and the Space Shuttle — was an outward-opening unified hatch with a single-handle release. The redesigned hatch could be opened in approximately 3 seconds from inside or 10 seconds from outside.

Cause of death

The cabin autopsy by the Apollo 204 Review Board attributed the three deaths to asphyxiation from carbon monoxide and combustion product inhalation, not to thermal burns. The three astronauts were found in roughly their launch positions: Grissom on the left, with his suit melted to the seat where contact had occurred; White in the centre, with his hands raised toward the hatch in an attempt to reach the release handle that he had not had time to grasp; Chaffee on the right, still strapped into his couch with his hands in the lap position.

The pressure-suit visors were closed and the umbilical oxygen lines were intact. The pressure suits had protected the crew from severe burns; they had not protected them from the carbon monoxide. The conventional reconstruction is that the three lost consciousness within 15-17 seconds of the fire start.

The Review Board

The Apollo 204 Review Board, chaired by NASA’s deputy administrator Floyd Thompson, reported on 5 April 1967 — nine weeks after the fire. The report identified the proximate cause (spark from frayed wiring), the contributing causes (the pure-oxygen-at-elevated-pressure atmosphere, the substantial flammable-material loading of the cabin, the inadequate fire-suppression provisions, the substantial wiring quality-control failures at the spacecraft prime contractor North American Aviation), and the systemic causes (the schedule pressure from the Kennedy 1961 commitment to a lunar landing by the end of the decade, which had produced corner-cutting in safety review).

The Senate’s investigating subcommittee, chaired by Senator Walter Mondale, conducted parallel hearings through spring 1967. North American Aviation lost its position as the lead Apollo prime contractor in autumn 1967 to Boeing on the CSM and Service Module work that remained.

The Apollo programme was suspended for 21 months. The next crewed Apollo flight — Apollo 7 — launched on 11 October 1968 with the redesigned hatch, a 60-percent-nitrogen-40-percent-oxygen ground atmosphere (switching to pure oxygen only at altitude where the absolute pressure was substantially lower), and reduced cabin flammable-material loading.

The Apollo 11 lunar landing took place on 20 July 1969 — 29 months after the Apollo 1 fire and 5 months before the Kennedy decade-end deadline.

Launch Complex 34

Launch Complex 34 was used for two more Saturn IB launches (Apollo 7 and the unmanned Saturn IB AS-205) and then decommissioned in 1969. The launch tower was demolished in the 1970s; the concrete launch pedestal still stands.

The pedestal carries two plaques. The larger one, installed in 1968, reads:

Launch Complex 34. Friday, 27 January 1967. 1831 hours. Dedicated to the living memory of the crew of the Apollo 1. They gave their lives in service to their country in the ongoing exploration of humankind’s final frontier. Remember them not for how they died but for those ideals for which they lived.

The smaller plaque, installed later by an unidentified visitor and now removed by NASA but informally re-placed by visitors at intervals, reads simply: Ad astra per aspera — through hardship to the stars.

The site is open to the public.