Risk to space station from debris is 1-in-5

June 27, 1994|By New York Times News Service

Dead satellites, shattered rocket stages and thousands of other pieces of man-made space junk speeding around Earth could destroy a planned international space station, and engineers are struggling to reduce the danger.

NASA estimates the chance that debris could smash through the shield of the space station, an orbital outpost for the world's astronauts, at 1-in-5 during its construction and expected 10-year life. That probability means that if there were five such stations, one would be expected to be hit.

While the station is to have redundant gear to maximize safety, and interior hatches to let astronauts seal themselves off from shattered areas that lose air, the overall risk of a catastrophe that would result in death or destruction of the craft is still estimated at roughly 1 chance in 10 over the same time.

NASA officials say they are confident that the risk of penetration can be reduced, perhaps to 1 chance in 10, making the risk of catastrophe about 1 chance in 20. Although the design already calls for much shielding, more may be added, they say. Such a remedy would add cost and weight to an already heavily laden project, they concede.

"We'll do whatever is necessary to get adequate safety," NASA Administrator Daniel S. Goldin said in an interview.

But Mr. Goldin also said danger and death were inevitable in space exploration.

"We'll never be able to guarantee total safety," he said. "We could have loss of life with the shuttle, and the station as well. If you want to guarantee no loss of life, it's better not to go into space."

Still, a station designer, who spoke on the condition of anonymity, said the bureaucracy was playing down the problem and courting disaster.

"The traditional design philosophy says the mission catastrophic risk should not exceed a few percent," the designer said. "Now, they've got it in the range of 10 percent. That violates due diligence. If you're working in an uncertain environment, your bias should be on the side of safety."

Bigger than a football field at 361 feet in length and 290 feet in width, the station would have a six-member international crew to study Earth, the heavens and human reactions to weightlessness in preparation for lengthy voyages to Mars and beyond.

The United States, Europe, Japan and Canada are longtime partners in the project, and Russia joined recently. The outpost would cost American taxpayers $43 billion, including $11 billion already spent on design studies.

Eighty-five launchings of gear and people will be needed to assemble and outfit the station. Assembly flights are scheduled to begin in late 1997 and end in 2002, after which the completed outpost is to be used for a decade or more.

The recent addition of the Russians to the plan is an important foreign policy initiative of the Clinton administration. It is intended to symbolize a new era of East-West accord and to engage Moscow in constructive space work in return for ending practices that upset Washington, like exporting advanced rocket gear to developing countries.

The plan faces a potentially close vote on the House floor this week. Some members fear that Russia's economic woes may jeopardize the project, while others see Russian participation as a way to help reduce the odds of political upheaval in Russia.

The amount of junk in orbit near Earth is rising at a rate of 2 percent to 5 percent a year, experts say.

The American military has found about 7,000 objects in orbit ranging from the size of a school bus to the size of a baseball, and it tracks all of them from the ground with radar. Smaller objects cannot easily be tracked.

Experts estimate that there are perhaps 150,000 objects circling Earth that could penetrate the space station. Because of the enormous speeds of everything in orbit, a tiny flake of metal can pack the punch of a hand grenade.

In general, the collision risks for orbiting stations are high because of their large size and long stay in space.

The shuttles are much smaller, going up for days instead of years, but they have nonetheless been moved on four occasions to dodge debris and have been hit by some objects that dug tiny craters.

For any single shuttle flight, NASA estimates the overall risk of catastrophic failure at about 1 in 78 missions. In contrast, the Air Transport Association estimates that a single airline flight has 1 chance in two million of ending in fatalities.

The space station program, begun by President Ronald Reagan in 1984, has tended to play down the threat from debris, partly because costs would rise if heavy shielding was chosen as the remedy.

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