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Space debris shifts space station plans

space station

The International Space Station in orbit (Image: NASA)

The US space agency is transforming both its space shuttle program and the International Space Station, to deal with space debris from sources such as US missile defence systems.

The new plans are revealed in a report, called Implementation Plan for International Space Station Continuing Flight, just released by NASA this week.

Keenly aware of how deadly debris impacts can be - the Columbia shuttle was destroyed due to wing damage from a piece of foam insulation that fell off the fuel tank during launch - NASA, for example, is stepping up inspections of, and installing more protective shielding on, the orbital outpost.

In addition, the agency is taking a more proactive role in preventing debris from crossing the space station's orbit, program manager Bill Gerstenmaier said during a teleconference with reporters this week.

For example, the agency requested a test of a space tether launched on an expendable rocket, to be staged at a lower orbit, so that if the tether broke, the pieces would not eventually wind up a threat to the station.

NASA is also taking a serious look at the US military's planned Missile Defense Systems program and plans to add its comments to the draft Environmental Impact Statement, currently under review.

"There are some satellites and some upper-stages [rockets] that break up in low-Earth orbit and then that debris cloud could come across the orbital plane of the station," Gerstenmaier said.

"We're looking at the launches to see if there is anything that we ought to be doing."

Other changes under way are directly tied to shuttle operations, such as setting up the station to serve as an emergency shelter in case a shuttle is too damaged to safely return to Earth.

Columbia was destroyed during its high-speed descent into the atmosphere for landing, as hot gases blasted into the ship's damaged wing. Seven astronauts died in the accident.

The new NASA report also addresses impacts of the shuttle's planned retirement in 2010.

Station program managers, for example, are revamping plans to return broken equipment to Earth for refurbishment and reflight.

In future, big station components, such as the gyroscopes, are likely to be packed aboard used cargo ships and dispatched with the trash to be incinerated in Earth's atmosphere.

This week engineers continued to troubleshoot a problem with a computerised circuit breaker that cut off power to one of the space station's three operating gyroscopes, massive spinning balls that allow operators to position the station without tapping into the limited supply of fuel for thruster burns.

Managers have decided not to replace the problem breaker for now and keep the station operating with two gyroscopes. A fourth device failed in June 2002.

The shuttle Discovery crew, which is scheduled to visit the station in May during the first mission since the February 2003 Columbia accident, will be bringing with them a replacement gyroscope.

NASA is considering having the crew replace the breaker during one of three spacewalks planned during the flight.
