Text size

Seventeen years after the Challenger tragedy, NASA has taken another blow, which may have devastating consequences for American and international space programs.

It is, of course, hard at this point to determine what caused the Space Shuttle Columbia to disintegrate. NASA's investigators may have difficulties later on as well, because much of the shuttle was burned and other parts were deformed when they hit the ground.

Based on the timing and position of the explosion - namely, the point of entry from outer space into the atmosphere, which is the most dangerous point on the return - two scenarios are most likely. The shuttle moves from space - where there is no resistance or friction - into the atmosphere, where resistance and friction are massive, thereby causing extreme heating. At this point, the temperature of the shuttle reaches 1,200 degrees, even preventing radio transmissions.

To keep the shuttle from incinerating, it is covered with ceramic tiles that absorb the heat and keep the spacecraft safe. It is possible that many tiles had fallen off either before or as the shuttle entered the atmosphere.

Another scenario is that the shuttle was simply too old. Columbia, the first shuttle to fly into earth's orbit in 1981, was the oldest shuttle still in use. Several experts have cautioned against using such an old shuttle due to metal fatigue. As the shuttle entered the atmosphere, one of its parts may have failed, causing terminal damage to the entire spacecraft.

A less likely possibility is that the accident was caused by human error, namely, that the astronauts themselves had mistakenly taken the shuttle off the planned course, which was arranged to assure a seamless entry into the atmosphere.

The shuttle disintegrated more than 60 kilometers above earth during the time when there is no communication with the spacecraft due to its high temperature. Communication, which was to renew shortly after, was never resumed, which will probably make it even harder to find the reason for the disaster, since the astronauts had no time to report any problem.

The disaster may have serious implications on the U.S. space program and might even halt future manned launches. In any case, all space shuttles will be grounded for a long time until the causes for the Columbia's disintegration are ascertained.

Yesterday's tragedy will also affect the international space station, which involves several countries along with the United States. Since the U.S. space shuttles were intended to bring astronauts and equipment to and from the station, NASA will have to find another solution.