Space Station Escape Options Include Shuttle, Pod

Richard A. Lovett
for National Geographic News
June 15, 2007
Astronauts on the International Space Station are scrambling to fix a computer that has taken down critical systems necessary to generate oxygen and maintain the station's orientation with respect to the sun.

Though NASA officials and outside observers are confident that the problem can be fixed, it raises the question of how exactly the aging station could be evacuated in the case of an emergency (pictures: space survival.)

How could the crew get home?

Option 1: Evacuation by Space Shuttle

The space station currently has ten people aboard, seven from Atlantis plus the station's three temporary residents.

But "everyone on the station now could get on it and come down, if they needed to," said Roger Launius, chair of the Division of Space History at the National Air and Space Museum in Washington, D.C.

Currently Atlantis's thrusters are keeping the station in a stable orbit, but the shuttle has only enough fuel for a few more days.

Option 2: Escape Pod

Space station astronauts arrive and depart via three-person Russian Soyuz spacecraft. One of these remains at the station at all times, specifically as an escape pod.

Since there are only three astronauts on the space station at any given time, all three could evacuate via a Soyuz craft, even without a visiting space shuttle.

Not an Option: Unmanned Cargo Ship

Unmanned Russian space freighters carry everything from food to fuel to newspapers to the station. But they do not provide a way home.

They aren't designed for reentry. Instead, they are filled with garbage, jettisoned, and burn up in the Earth's atmosphere.

Plenty of Time

If an evacuation were needed, there would probably be plenty of time to do it in an orderly manner, maximizing the chances that the station could be reoccupied later on, Launius said.

Assuming enough systems are working so that the station's alignment can be maintained from Earth, he said, "there's no reason to believe they couldn't just shut it down in an orderly manner."

Then, hopefully, "it's simply a question of going back up and reactivating the systems," he said.

Something similar had to be done in 1973, he added, when the original Skylab was first occupied.

Before going aboard, he said, the crew had to deploy a sunshade to deflect the sun, then get the power systems up and running so they could turn on the air conditioning and go aboard.

(See a gallery of the best pictures taken from the International Space Station.)

The Problem at Hand

This week's computer failure occurred when crewmembers of NASA's space shuttle Atlantis were installing a new truss designed to boost the station's solar power capability by 20 kilowatts.

The problem appears to be a software glitch, which repeatedly set off fire alarms and caused the computer to continuously reboot mode.

The computer is necessary to operate the station's maneuvering thrusters, which help keep it in proper alignment with the sun. That's necessary both for solar power generation and to keep critical components from overheating under the strong glare of outer-space sunlight.

"We've got a plan to go work the problem," NASA Associate Administrator William H. Gerstenmaier said yesterday at a news briefing in Houston. "I don't consider this critical."

Everyone who's ever upgraded a computer knows what that can entail, added Launius of the National Air and Space Museum.

"I've done that with my own computer. I put in a peripheral and suddenly there's a power surge and the whole thing's dead. You simply have to fix it. It can be done."

Not the First Time

It's not the first time the space station has had problems.

In 2005 a failure in the oxygen-generating equipment, combined with delayed space shuttle launches due to Hurricane Katrina, caused a crimp in supplies.

And in 2004 supply shortages in the wake of the Columbia shuttle disaster led the Russians to make contingency plans for an emergency evacuation of the station's crew.

Both problems were solved by supply shipments via unmanned Russian capsules.

But the new problem has to be solved before Atlantis goes home, the Los Angeles Times reported.

The station has a 56-day reserve supply of oxygen. But the crashed computer controls the station's attitude-control thrusters, which assist the station's sometimes quirky gyroscopes in keeping it properly aligned.

So long as Atlantis is there, the shuttle's thruster's can take over this duty.

But even with those time constraints, the chances of abandoning the station, Gerstenmaier told the Los Angeles Times, are "extremely remote."

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