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REENTRY RISKS Glenn recalls danger he faced in '62 flight
By Ray Henry, Globe Correspondent, 2/4/2003
Glenn said the outside of the capsule was glowing hot during the reentry, and he began to perspire in the increasing heat. The gravity forces increased about eight times what is normal on earth, pinning Glenn's body against his seat. From behind, he could hear the sound of metal twisting, breaking, and tearing away. The whole capsule was lurching. ''Back in those days, it was so new. We used to have ghoulish little jokes about how many of us would be around at the end of Project Mercury,'' Glenn recalled in an interview yesterday. But he survived the flight and went on to become a US senator. Although the Columbia accident on Saturday marked the first time a US crew died while returning to earth, space explorers have known for decades that landing a spaceship posed extraordinary hazards. Four Russian cosmonauts have died during reentry, and seven Americans -- including Glenn -- came perilously close even before the first shuttle was launched in 1981.
And NASA engineers long ago accurately forecast the odds of a reentry catastrophe involving the space shuttle. In 1979, they calculated that a shuttle reentering the atmosphere had a one in 100 chance of experiencing a major accident. The Columbia was the 113th shuttle flight. During reentry, an orbiting spacecraft moving thousands of miles an hour in a vacuum suddenly encounters air molecules in the upper atmosphere. The resulting friction can cause temperatures as high as 3,000-degrees Fahrenheit and severely stress metal, specialists said. Any deviations in the flight path also can cause catastrophic failure. Glenn bobbed in the Atlantic for 21 minutes before the Navy picked him up in 1962. But just one flight earlier, astronaut Virgil ''Gus'' Grissom nearly drowned on July 21, 1961, while waiting for a Navy helicopter, when explosive bolts prematurely opened the hatch of his Mercury capsule. The capsule flooded and sank three miles off the Bahamas, nearly taking Grissom down with it, he wrote in his memoirs. Then, three years before Neil Armstrong first landed on the moon, he and astronaut David Scott had to make an emergency reentry on March 16, 1966, after a thruster caused their two-man Gemini 8 spacecraft to roll violently once every second. The spinning was so furious that ground controllers feared Armstrong and Scott would lose consciousness, lose control of the craft, and never reenter. But the veteran test pilots kept their heads absolutely still to maintain consciousness and used their reentry rockets to stabilize the capsule. They made an emergency landing near Okinawa and survived. Soviet cosmonaut Vladimir Komarov was less fortunate, becoming the first cosmonaut to die during a mission when his main parachute became snagged on April 24, 1967, after reentry. He plunged to the earth and was killed on impact. Three years later, an oxygen tank explosion crippled the Apollo 13 on its way to the moon. Astronauts James Lovell Jr., John Swigart Jr., and Fred Haise Jr. aborted their planned moon landing and conserved enough oxygen and electricity to return to earth. But the danger wasn't over: flight controllers feared the explosion might have damaged the crew's heat shield and that they would meet the fate Glenn escaped. Although damage to the service module was severe, the heat shield remained intact, allowing the crew to land safely. Scientists originally estimated that there was a two-tenths of a percent chance that a serious accident could happen on an Apollo flight, said aerospace engineer Hans Mack, who investigated the Apollo 13 accident and later became deputy administrator of NASA. But fellow panel member Neil Armstrong, who made the emergency landing during Gemini 8, told Mack to discount the official statistics, saying the true accident risk was about one in 10. ''When I was a test pilot and flew the X-15, that's the rough estimate I always made. If the probability was greater than one in 10, I didn't fly,'' Mack recalled Armstrong saying. The most serious reentry accident before the Columbia disaster occurred on June 29, 1971, when the Soviet Soyuz 11 depressurized during reentry. Air rushed out of the capsule, killing cosmonauts Georgi Dobrovolsky, Vladislav Volkov, and Viktor Patsayev, who apparently made a desparate attempt to close the pressure-equalizing valve. The cramped conditions in the capsule prevented the crew from wearing spacesuits, which would have saved their lives. Despite the loss of the Columbia, Glenn was adamant yesterday that the scientific benefits of space flight, outweigh the risks. ''If you get scared off by those statistics, you shouldn't be in the program to begin with,'' he said.
This story ran on page A13 of the Boston Globe on 2/4/2003.
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© Copyright 2003 New York Times Company |
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iving backward through the atmosphere, astronaut John Glenn wondered if he was about to be vaporized as pieces of molten metal flew past the porthole of his Mercury spacecraft on Feb. 20, 1962.
