One of those Orbiting Calamities to avoid

The Space Shuttle Atlantis STS-125 blasts off from Cape Canaveral, ...
(AFP/Getty images)

Second NASA shuttle poised for bold space rescue

WASHINGTON (AFP) – It would be the most audacious rescue in space flight history. Alongside NASA's mission to repair the Hubble telescope, the US space agency is preparing a second intrepid shuttle mission it hopes never to launch.

NASA has sent its Atlantis space craft hurtling toward the aging Hubble, on a daring final task that has forced it to devise a rescue operation worthy of a blockbuster movie plot.

If the Hubble trip turns from scheduled service to orbiting calamity, there will be no escape to the relative safety of the International Space Station, so NASA plans to send a second shuttle -- the Endeavour -- and a four-strong crew blasting off to save their Atlantis colleagues.

In this scenario, Endeavour -- primed to go with just three-days notice on a launch pad at the Kennedy Space Center in Cape Canaveral, Florida -- races to catch up with Atlantis and recover its stranded crew of seven astronauts.

NASA fears in a powerless shuttle, astronauts would only last for 25 days before they ran out of air, and so, if difficulty strikes the two vessels would rendezvous at an altitude of some 600 kilometers (372 miles) above the Earth.

After parking their payload bays face to face, like a robotic yoga display, Endeavour would delicately maneuver its 50-foot (15-meter) robotic arm to secure the spacecraft together.

Over the course of two days, with Endeavour astronauts stringing a line between the two shuttles, the Atlantis crew would have to spacewalk from their weakened ship to safety.

Such a scenario, however outlandish, has been planned extensively, insists the National Aeronautics and Space Administration.

"It's safety first, as ever," said NASA spokesman William Jeffs at Houston's Johnson Space Center in Texas.

Since NASA's 2003 disaster that saw the shuttle Columbia disintegrate as it re-entered Earth's atmosphere, killing all seven crew members, the agency has worked on elaborate rescue contingencies.

But all shuttle flights since then have been to the ISS -- a secure enough haven where crew members would be able to await passage home.

The daunting journey to the 11-ton Hubble carries considerably more risk of being hit by space debris or micrometeorites than a flight to the ISS, because the telescope orbits at almost twice the height of the ISS.

That is much closer to the largest galactic trash fields that threaten all space visits.

After analysis, NASA said the risk of catastrophic damage arising from space debris around Hubble to be about a 1-in-229 chance.

And beside space junk, numerous liftoff dangers could still await Atlantis, including thermal tiles on the outer skin being damaged at launch.

Astronauts will make a safety assessment of their vessel before heading to Hubble in the coming days, after which NASA may deem re-entry too risky.

Endeavour Commander Christopher Ferguson said he and his crew were ready to tackle a rescue if called upon.

"I feel as confident about our ability to pull this off, if need be, as I would any other mission," he told CNN television.

It is the first time a rescue shuttle has been on standby on the launch pad, with its crew idling at the ready.

Ferguson said he understands how every hour can be key, when colleagues are running out of air to breath.

"Consumables like food and oxygen would run out quickly. So the reason we've gotten this crew trained and spooled up and ready to go on literally a moment's notice is because they (the Atlantis crew) have no place comfortable to go stay for a long period of time," he said.

Atlantis Commander Scott Altman told the network that knowing there is a second shuttle ready to take their emergency call gives him and his crew confidence for the journey.

"Even in the worst-possible imaginable case, we can stay up there and last until somebody comes up and gets us," Altman said. "So it feels like we have all our bases covered."

In the event of an abandoned ship, Atlantis would be given self-destruct instructions, to ensure it would not fall back to Earth in a populous area.

NASA, said Jeffs, would direct it into landing maneuvers to crash somewhere in the Pacific Ocean.

In 10 days, Endeavour will step down from its poised alert, assuming Atlantis returns to Earth safely.

Afterwards, the shuttle will trundle steadily from launch pad 39B to 39A, for its own mission to the ISS in mid-June.