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Sunday, January 28, 2007

The Apollo 1 / Challenger Disasters, January 27/28, 1967/1986

Manned space exploration has always been fraught with danger. Even though orbital flight has become fairly commonplace, it is impossible to escape the fact that going into space requires one to be strapped onto a highly explosive rocket carrying a very complicated craft whose failure would expose the crew to immediate death.

This evening, we look at two space-related accidents, both of which occurred under the auspices of the US space program, managed by the National Aeronautics and Space Administration, or NASA. They occurred on January 27th and 28th, 19 years apart. While the two accidents are not directly related, both served to make traveling into space safer for those who would follow.

On January 27th, 1967, Apollo/Saturn 204 sat on Pad 34 at Cape Kennedy in Florida. This spacecraft, which would become known to the world as Apollo 1, was to be the first manned Apollo mission. It was a Block 1 craft, meaning that it was the first generation of capsule that would carry men to the Moon. It was to launch in a little over a month and would be strictly a test flight conducted in Earth orbit. It would allow all the launch and control facilities involved in the Apollo program to hone their skills in preparation for future missions aimed at landing on the moon.

In command of AS-204 was Air Force Lieutenant Colonel Virgil "Gus" Grissom. Grissom was one of the original seven Mercury astronauts, the first Americans to orbit the Earth. He was the first American to make two journeys into space, onboard Mercury-Redstone 4 and Gemini 3.

The senior pilot position on AS-204 was held by Air Force Lieutenant Colonel Edward White. White was the first American to make a spacewalk while he was the pilot of the Gemini 4 mission. Apollo 1 was to be his second flight into space.

The pilot for the mission was Navy Lieutenant Commander Roger Chaffee, who had never flown into space. He was a latecomer to NASA compared to his two crewmates, having not joined the program until 1963. It was rumored that Chaffee had been the pilot of the U2 spy plane that first took pictures of Soviet missile facilities in Cuba in 1962, a mission which led to the Cuban Missile Crisis.

On the fateful day, the crewman of AS-204 were strapped into the Apollo capsule as they would have been for an actual launch. Small problems plagued the scheduled tests almost immediately. First, Grissom noticed a sour smell in the air entering his spacesuit. Then, an alarm sounded warning the men of high oxygen flow in the capsule. Finally, communications between the capsule and the control room became faulty. While the communications system was fixed, the crew continued to run through the checklists they would have to cover prior to an actual launch. At 6:31PM, a voice came over the radio saying, "We've got a fire in the cockpit." The transmission was only a few seconds long and ended with a short cry. Ed White attempted to open the capsule's hatch, but to do so in a hurry was impossible. To open the hatch, several bolts had to loosened and the inner section of the two-part design had to be opened inward, something that was impossible to do once the pressure inside the capsule rose so that it was greater than atmospheric pressure. It took the ground crew five minutes to get the hatch open from the outside, by which time all three astronauts were dead.

It was later determined that the three men had most likely died of smoke inhalation rather than burns and that they were all dead within 17 seconds of White's transmission. The Block 1 Apollo module contained more than 30 miles of wiring, so finding the cause of the spark that caused the fire was a daunting task. The pure oxygen atmosphere inside the craft ensured that the interior was almost completely destroyed. Eventually, it was determined that a sliver-plated copper wire running through one of the capsule's environmental control units had become stripped of its insulation and had experienced an exothermic reaction when it passed near a leaking ethylene glycol cooling line.

As a result of the AS-204 fire, several aspects of the Apollo capsule were changed. The all-oxygen atmosphere was replaced with a 40% nitrogen, 60% oxygen mixture that would slowly change to an all-oxygen environment once the module was in orbit. The main hatch was re-designed so it opened outward and could be done so in less than 10 seconds. All flammable materials were replaced. Finally, the astronauts' nylon suits were replaced with coated glass fabric ones which, while flammable, are much harder to ignite.

NASA never intended to call the fated AS-204 mission Apollo 1. However, Grissom, his crew and most of the people at the Cape began to refer to mission by that name during training. After the accident, the families of the astronauts asked that the mission be officially named Apollo 1. NASA agreed, and that is the name by which AS-204 is known today.

The US space program recovered from the Apollo 1 disaster and within 2.5 years had landed two men on the moon. Once that milestone had been achieved, public interest in space travel began to wane; as a result, NASA's budget began to see cuts. The 1970's saw Skylab and the Apollo-Soyuz mission use the last of the Apollo hardware. But on the drawing board was something revolutionary: a reusable space plane called the Space Shuttle.

The Space Shuttle Columbia first flew in April, 1981. This was the first time in nearly six years that an American had been into space. The Shuttle fleet, which originally consisted of four vehicles, met with strong criticism, but many saw it as a step in the right direction for human space flight. NASA envisioned using the Shuttles to deliver satellites into orbit, as well as parts for a space station. It would serve, essentially, as a giant cargo van. As the number of missions flown by the Shuttles increased, liftoffs garnered less and less public attention. This would all change one winter morning in 1986.

The morning of January 28, 1986 found the Space Shuttle Challenger ready to depart on another mission. On board were Michael Smith, Dick Scobee, Ronald McNair, Ellison Onizuka, Gregory Jarvis, Judith Resnik and Christa McAuliffe. McAuliffe was not an astronaut, but rather a school teacher. She had been selected from more than 11,000 applicants to be the first teacher in space.

It was cold the night before the launch, right at freezing. This was near the temperature below which NASA would not launch a shuttle. Engineers who worked for the company that built and maintained the Shuttles' solid rocket boosters, Morton Thiokol, argued that it was too cold to launch. The concern was specifically aimed at the flexible O-rings that sealed the joints on the boosters. According to them, any temperature below 53 degrees Fahrenheit could cause the O-rings not to seal properly. In the end, however, Morton Thiokol management overrode their engineers and declared the boosters safe to fly.

The next morning found much of the launch pad structure covered with ice. Engineers at Rockwell International, the main Shuttle contractor, said they could not guarantee a safe launch under current conditions. NASA engineers disagreed, but this time a compromise was reached: the launch would be postponed for one hour. Challenger was cleared to launch at 11:38AM local time.

58 seconds into Challenger's last flight, a plume of flame escaped from the starboard side solid rocket booster. Later investigation showed that this was due to one of the O-ring's inability to seal properly. This began a chain of events that, at the time, was completely unknown to the ground controllers and the Challenger crew. 73 seconds into the flight, the giant external tank underneath the shuttle disintegrated, causing the Challenger to do the same as the craft exceeding her design limits with regard to aerodynamic forces. She was 48,000 feet in the air.

The crew cabin of Challenger detached from the vehicle in one piece and continued upward, eventually reaching an altitude of 65,000 feet before beginning a free fall descent to the ocean below. It is estimated that the cabin was traveling at over 200 mph when it hit the ocean. The crew was most likely killed instantly from the impact.

January 28th was the day scheduled for President Ronald Reagan to present his State of the Union Address to Congress and the American people. Instead, he addressed the nation from the Oval Office and quoted the poem "High Flight" by John Gillespie Magee, Jr.:

"We will never forget them, nor the last time we saw them, this morning, as they prepared for their journey and waved goodbye and 'slipped the surly bonds of Earth' to 'touch the face of God.'"

The Rogers Commission, formed to investigate the disaster, concluded that the cause of the accident was indeed an O-ring on the starboard solid rocket booster. The Commission also criticized NASA "safety culture", stating that the estimates of Shuttle reliability had been grossly overstated.

The United States lost one other Shuttle, Columbia, in February, 2003 during re-entry. Three Shuttles remain in service; they are set to be retired in 2010.

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