 |
|
News: Shuttle’s Tiles Seattle Times - Dallas Morning News February 03, 2003 Source: http://seattletimes.nwsource.com/html/nationworld/134627234_tiles03.html Monday, February 03, 2003, 12:00 a.m. Pacific Shuttle tiles have history of troubles By Katie Fairbank The Dallas Morning News DALLAS — The tiles that protect the space shuttle from searing heat are all that stands between safety and disaster for the flight crew re-entering the atmosphere as a hurtling fireball. The heat-resistant bricks, which deflect temperatures high enough to melt steel, have long been a controversial part of the shuttle program. Now, they are the leading theory into the inquiry in the Columbia disaster and the deaths of all seven of its crew. Moments before it disintegrated, the Columbia had a sudden and unexpected 60-degree rise in temperature, according to sensors in the middle-left side of the fuselage, shuttle-program manager Ron Dittemore told a news conference yesterday. Sensors elsewhere in the craft's left side also recorded rapidly rising heat. While the information is preliminary, it suggests that some of the heat-protection tiles were missing or damaged, Dittemore said. Investigators started looking at the tiles almost as soon as things went wrong for the Columbia. That's because a piece of foam insulation peeled off a fuel tank and hit the heat-resistors on the left wing during blastoff. Although the incident was dismissed as insignificant at the time, it is now being considered as a possible catalyst for the disintegration upon the shuttle's re-entry. The tiles have been a worry to the shuttle program since its earliest days. In 1979, when the Columbia was transported on the back of a modified 747, it shed 40 percent of its tiles. That sent engineers on a two-year search for a bonding agent that would hold. "The tiles were of concern from the absolute beginning," said Alcestis "Cooky" Oberg, who writes about space and science, including two books about the space shuttle. "They were a totally new property, and they had to be manufactured for this purpose. "They were concerned because you had to glue these onto the shuttle. They were very labor-intensive. All of them have to work, and especially the ones along the nose and the leading edge and the tail." Early on, many tiles went missing during a flight. Even now that still occurs. "That's not uncommon on shuttle missions where debris or ice have nicked the thermal protection," said Curt Brown, who flew six space-shuttle missions before retiring from NASA two years ago. "It's not on every flight, but it's not uncommon." Problems with adhesion also have continued. Two years ago, the Aerospace Safety Advisory Panel noted that improperly installed tiles were a problem the agency had to fix. The tiles themselves are 95 percent air and 5 percent silica glass, which is made from sand. The tiles are easily dented — even a raindrop could crack one when the shuttle is traveling at high speed. Because of their fragility, they are inclined to chip or break often. "If you were to ... ping it with your fingernail, it would feel like a very fine ceramic," said Kari Fluegel, spokeswoman for Manufacturer United Space Alliance, which makes the tiles. The tiles are fired into bricklike shapes and covered with a black silica glass coating. They then are bonded individually onto the aircraft. It takes hundreds of people to inspect and repair the 30,000 thermal tiles on the shuttles between each flight. When working properly, the tiles block heat entirely, said Claude Canizares, a professor of physics at the Massachusetts Institute of Technology in Cambridge, Mass. "You can put your hand on one side and a blow torch on the other and you don't feel anything," he said. "It's like the ultimate trivet to your dining-room table." Now, NASA is considering whether the fragility of the tiles contributed to the Columbia disaster, but the agency cautions that it's early in the investigation. "As we gather more evidence, certainly the evidence may take us in another direction," Dittemore said. Information from Knight Ridder Newspapers is included in this report. Copyright © 2002 The Seattle Times Company |
|
|
|
 |
|
|