1967: Gus Grissom, Ed White and Roger Chaffee are killed on the launch pad when a flash fire engulfs their command module during testing for the first Apollo-Saturn mission. They are the first U.S. astronauts to die in a spacecraft.

The command module, built by North American Aviation, was the prototype for those that would eventually accompany the lunar landers to the moon. Designated CM-012 by NASA, the module was a lot larger than those flown during the Mercury and Gemini programs, and was the first designed for the Saturn 1B booster.

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NASA: 50 Years of Towering AchievementEven before tragedy struck, the command module was criticized for a number of potentially hazardous design flaws, including the use of a more combustible, 100 percent oxygen atmosphere in the cockpit, an escape hatch that opened inward instead of outward, faulty wiring and plumbing, and the presence of flammable material.

Regarding the cabin atmosphere and hatch configuration, it was a case of NASA overruling the recommendations of the North American designers. North American proposed using a 60-40 oxygen-nitrogen mixture. But because of fears over decompression sickness, and because pure oxygen had been used successfully in earlier space programs, NASA insisted on it being used again.

NASA also dinged the suggestion that the hatch open outward and carry explosive bolts in case of an emergency, mainly because a hatch failure in the Mercury program's Liberty Bell 7 capsule had nearly killed Gus Grissom in 1961.

So CM-012 was completed as ordered and delivered to Cape Canaveral.

The three astronauts knew they were looking at a potential death trap. Not long before he died, Grissom plucked a lemon from a tree at his house and told his wife, "I'm going to hang it on that spacecraft."

The test on Jan. 27 was a "plugs-out" launch simulation designed to see if the Apollo spacecraft could operate on internal power only. It was considered a non-hazardous test.

Several problems delayed the beginning of the test until evening.

Once the test was underway, Grissom, Ed White and Roger Chaffee were strapped into their seats when a voltage fluctuation occurred. Grissom was heard shouting "Fire!" and White followed immediately with "We've got a fire in the cockpit."

It was all over within 30 seconds, perhaps the longest half-minute in NASA's history. Pandemonium broke out as the capsule filled with flames and toxic smoke, and Chaffee could be heard yelling, "Let's get out! We've got a bad fire! We're burning up!"

Screaming was heard before the communications cut out. The command module ruptured. The three astronauts lost consciousness and died of smoke inhalation within 15 to 30 seconds after their suits failed, the official report estimated.

Rescuers were prevented by the flames, and by toxic fumes — their gas masks were faulty — from opening the hatch for a full five minutes, and in any case the idea of rescue was futile.

The bodies had severe third-degree burns, and the flames were so intense that the space suits of Grissom and White were fused together. After six hours of investigation, it took 90 minutes to remove the charred bodies from the melted spacesuits and nylon material from the module interior.

Investigators determined that the cabin pressure at the time of the fire would have prevented the hatch from being opened, even if White, the astronaut charged with operating the hatch in an emergency, had been able to reach it. Although the exact cause of the fire has never been determined, a review board concluded that the combustible material inside the module almost certainly contributed to its severity.

As a result of the tragedy, the Apollo command module underwent a thorough redesign.

Grissom and Chaffee are buried at Arlington National Cemetery. White is buried at the U.S. Military Academy at West Point.

Source: NASA, Wikipedia

Photo: Virgil I. "Gus" Grissom, Edward H. White II and Roger B. Chaffee/NASA

An earlier version of this article appeared on Wired.com Jan. 27, 2009.

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