Apollo 1 Anniversary: Fire That Killed Three NASA Astronauts Recalled 45 Years Later (PHOTOS)

Long before the triumphant moon landing of Apollo 11 and the heroism of Apollo 13, three astronauts died in a flash fire inside the capsule of Apollo 1 (which was originally designated Apollo 204). Jan. 27 marks the 45th anniversary of the tragedy, which threatened the entire Apollo program and brought about changes to spacecraft design.

The fire, which occurred during a simulated launch, killed Command Pilot Virgil "Gus" Grissom, Senior Pilot Edward H. White and Pilot Roger B. Chaffee. The fire's origin was never determined, but a subsequent investigation found numerous flaws in the spacecraft's design. Less than three years later, Neil Armstrong and Buzz Aldrin set foot on the moon and the Apollo program was vindicated. Today, NASA memorializes the crew along with other astronauts have died.

Keep clicking to see a slideshow featuring pictures of the crew and the spacecraft - and the aftermath of the accident.