It was the first Apollo mission, the one that would lay the groundwork for the eventual first manned mission to the moon. And it ended in tragedy for NASA and for the astronauts involved. on Friday, NASA opened an exhibit at their facilities in Cape Canaveral, Fla., 50 years to the day that the Apollo 1 caught fire to remember the event.

The exhibit featured the hatch from the burned spacecraft that had been concealed from the public’s view ever since that fateful day: Jan. 27, 1967. That burned hatch sealed the fates of Gus Grissom, Ed White and Roger Chaffee.

The launch was supposed to happen Feb. 21. It was during a launch rehearsal at Cape Kennedy Air Force Station Launch Complex 34 that a cabin fire broke out, killing all three crew members and destroying the Command Modules. The spacecraft was supposed to be the first manned lunar landing, although it would take a number of spacecraft before NASA finally achieved successed with Apollo 11.

An investigation into the fire determined that it was an electrical fire that spread quickly due to combustible nylon material, the high pressure and the pure oxygen in the cabin. The astronauts couldn’t be reached because of the plug door hatch that was sealed due to the high internal pressure inside.

Apollo flights were suspended for 20 months as investigators assessed the hazards in the Command Module. The first successful manned Apollo mission wouldn’t happen until October 1968 on Apollo 7.

NASA said about the incident: “On January 27, 1967, tragedy struck the Apollo program when a flash fire occurred in command module 012 during a launch pad test of the Apollo/Saturn space vehicle being prepared for the first piloted flight, the AS-204 mission. Three astronauts, Lt. Col. Virgil I. Grissom, a veteran of Mercury and Gemini missions; Lt. Col. Edward H. White, the astronaut who had performed the first United States extravehicular activity during the Gemini program; and Roger B. Chaffee, an astronaut preparing for his first space flight, died in this tragic accident.

“A seven-member board, under the direction of the NASA Langley Research Center Director, Dr. Floyd L. Thompson, conducted a comprehensive investigation to pinpoint the cause of the fire. The final report, completed in April 1967 was subsequently submitted to the NASA Administrator. The report presented the results of the investigation and made specific recommendations that led to major design and engineering modifications, and revisions to test planning, test discipline, manufacturing processes and procedures, and quality control. With these changes, the overall safety of the command and service module and the lunar module was increased substantially. The AS-204 mission was redesignated Apollo I in honor of the crew.”