Grissom, White, and Chaffee died aboard Apollo 1 in 1967
When I was on the cusp of twelve I recall the Apollo 1 disaster whereby three astronauts were killed in a fire which sprang up quickly and asphyxiated them before they could be rescued. I recall how horrible I thought it must be to die thusly — particularly in the hyperoxgenated engulfing type blaze described in the literature.
At that time I was exceedingly "pro NASA" and it was an incident which has stayed with me from then until now.
During a launch simulation US astronauts Virgil I Grissom, Edward H White, and Roger B Chaffee perished in a fire aboard Apollo 1. I was dismayed that a cabin fire during a launch rehearsal could even happen, much less kill three of our national heros.
The result of this tragedy was that significant safety changes were made that enabled the success of the Apollo program possible.
Virgil "Gus" Grissom was a veteran astronaut, and had already participated in the Mercury and Gemini programs.
Edward "Ed" White was The first American to walk in space during the Gemini IV mission.
Roger Chaffee was A naval aviator and aeronautical engineer, making his first spaceflight.
Elements of The Apollo 1 Tragedy
The tragedy was caused during a "plugs-out" test for the planned February 21, 1967 launch.
A fire erupted in the Apollo Command Module caused by a spark from damaged wiring ignited flammable materials in the pure oxygen environment.
There was a inward-opening hatch which trapped the astronauts.