Science and Space

space and astronomy articles.

Discovery and danger of debris

Nasa is investigating two cases of apparent debris seen falling from the space shuttle Discovery as it blasted off for Earth orbit. In one case, a heat shield tile seems to have been affected on the underside of the shuttle. The tip of the shuttle’s external fuel tank also hit a bird as it launched from Kennedy Space Center on Tuesday.

John Shannon, STS-114 mission operations representative, pointed out video frames apparently showing a piece of heat shield tile breaking off from the underside of the shuttle. This has left a one-and-a-half inch white spot near the nose landing gear doors. Mr Shannon said it could simply be that part of the black covering on the orbiter’s underside was damaged exposing the heat shield tile. But he added that it was equally possible the tile itself had been dented or sheared.

Experts cannot yet determine its size, but it did not appear to hit the shuttle.

The shuttle program has lived with damage from debris from the very first flight, in 1981; in 113 missions the orbiters have been hit by debris some 15,000 times, mostly on liftoff. The National Aeronautics and Space Administration replaces about 100 insulating tiles after every flight and repairs many more than that.

Now, though, it will be far easier to spot such damage while the shuttle is still in orbit. NASA can detect a crack of just two-hundredths of an inch, the width of two business cards pressed together. On the leading edge of the orbiter’s wing, such a crack could admit dangerous amounts of superheated gas during re-entry. A similar crack elsewhere might not.

It was a large hole in the left wing’s leading edge, caused by impact with a 1.67-pound piece of insulating foam during the launching, that led to the Columbia disaster.

NASA’s efforts to create a repair kit for tile and leading-edge panels have not been successful. Techniques will be tested during a spacewalk in coming days, but they are not ready for an actual repair, and the Discovery astronauts have said they would not want to trust any patchwork on a return to Earth.

Another option, the "safe haven" plan, would involve abandoning the $2 billion shuttle and having the astronauts wait in the space station for a rescue mission. For that to work, another shuttle would have to be launched within a few weeks. That is theoretically possible but carries risks of its own: the chance, for example, that the orbiting astronauts would run out of food, water or oxygen before the mission could be mounted.

posted by: kyawoo at 01:41 | link | comments |
space shuttle

Comments: