Wednesday, November 08, 2006

Shuttle Computers Find No End to 2006

One year might as well be an eternity for NASA’s space shuttles, which – it turns out – have no automatic reset once the calendar hits Jan. 1, 2007.

“The interesting thing about the shuttle computers and the ground computers that support the shuttle is that they were never envisioned to fly through a year-end changeover,” says NASA’s shuttle chief Wayne Hale here at the agency’s Johnson Space Center. “So the shuttle computers actually keep counting and they believe that it is Day 366 instead of Day 1 of the New Year.”

While it sounds trivial, it’s actually not since the chronological misalignment would put an orbiter and its ground support out of step with navigational assets vital for a shuttle mission, Hale said. Some shuttle software fixes have been certified for use in an emergency, such as a rescue mission, but more work is needed to fly shuttles over a year end during a normal flight, he added.

That’s why NASA’s next shuttle mission, STS-116 aboard Discovery, is poised to launch during an 11-day window that opens on Dec. 7. That window could stretch to 12 days should NASA officials decide to aim for a Dec. 6 launch date since Discovery’s preflight work appears to be ahead of schedule, Hale said.

NASA is also hoping to launch Discovery as early as possible so space agency employees (many of whom have already given up countless weekends and holidays-and continue to do so-to support shuttle missions) have a chance to spend the year end holidays away from work, Hale said.

To free up workers for holiday and avoid a year-end shuttle flight, NASA must fly STS-116 – an International Space Station (ISS) construction mission – by Dec. 18 or so.

The good news is that unlike the summer months at NASA’s Kennedy Space Center in Florida, which are notorious for afternoon thunderstorms that have caused delays during the last few shuttle flights, winter weather at the spaceport is a bit more manageable, shuttle officials say.

“With the more benign weather that we have in Florida in December, we think that will be adequate to get us off,” Hale said.

Other good news: Turns out the ISS computers can and do make the switch from one year to the next. Bonus.


The Story of the Space Shuttle


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