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May 11, 2009

Endeavour Standing By

As I noted last September, this shuttle mission is considered the most dangerous to date. The chance of impact from orbital debris was then estimated at 1 in 185 for the 350-mile altitude orbit. Since September, the debris danger has been somewhat reduced to 1 in 229 compared to 1 in 330 for the 200-mile-high space station orbit.

But foam falling during launch remains the primary danger. Damage to the wings from foam falling off the external fuel tank caused the destruction of the Space Shuttle Columbia in 2003. Though new processing methods limit the amount of debris hits during launch, the risk remains at about 1 in 80. Shuttle Program Manager John Shannon told reporters last fall that historically, the risk of a catastrophic failure is closer to 1 in 60.

If an orbital inspection (to be performed on the day after launch) reveals damage to critical areas on Atlantis, the space station is not available as a safe haven. Some students asked me why they can’t just descend to the station’s altitude. The problem is that the station is at a different inclination (angle) to the Earth’s equator than Hubble. It is as if Hubble is going around on the outer lane of a racetrack, and the station is on an inner lane that goes above and then below the Hubble track. To “cross over” from one to the other requires a tremendous amount of energy—more than the space shuttle has available.

Therefore, if damage is found, the Atlantis crew will power down the vehicle and wait for the Space Shuttle Endeavour (STS-400), to launch and provide a ride home. Endeavour is waiting on launch pad 39B, but it would not launch from there. That launch pad is already being converted for use by the new Ares booster. So if Endeavor is needed, it will be moved and then launched from 39A as soon as May 18 (if Atlantis launches May 11).

The STS-400 crew will be commanded by Chris Ferguson and include pilot Eric Boe and mission specialists Shane Kimbrough and Steve Bowen. The two shuttles would then perform an unprecedented rendezvous in space. Endeavour would approach to within (robotic) arn’s reach of Atlantis, grapple it, and hang on with the two payload bays facing each other. Two days of dramatic spacewalks would get everyone transferred across. A good summary of the mission by Chris Gebhardt.

However, the Hubble repair mission with its five choreographed spacewalks is plenty dramatic without a rescue. So fingers are crossed and prayers offered that STS-400 will be unnecessary.
Remember launch is scheduled for 2:01 Eastern/1:01 Central. The next day will be inspection, and if they are given the all clear, Hubble capture is anticipated on Wednesday just before noon Eastern time.

You can watch the press conferences on NASA TV, or "tune in" to online coverage. Fellow fans of Miles O’Brien, formerly of CNN; Marc Carreau, formerly of the Houston Chronicle; and Craig Covault, formerly of Aviation Week, will be happy to know that all three will be covering the flight for Spaceflight Now in an interactive format. You can follow them on Twitter—and don’t forget to follow NSS on Twitter, too!

To the stars,

Marianne Dyson
NSS Advisor

Former NASA Flight Controller;

Posted by m_dyson at May 11, 2009 12:18 AM



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