NASA Says It's 'Certain' Of Cause In Columbia Tragedy

More than a year after the space shuttle Columbia disintegrated 60,000 feet above Texas and Louisiana, NASA now says it knows "for certain" what caused the accident. Fixing that problem, along with one recently discovered, means NASA will delay the next shuttle launch until at least March, 2005.

What Happened

In a scenario rarely modeled before Columbia -- and exhaustively simulated since -- NASA's associate administrator for space flight, Bill Readdy, says air or nitrogen, liquified by the cryogenics that super-cooled the external tank, seeped into tiny cracks in the foam. As the spacecraft rose into the Florida skies on January 16th, 2003, that liquified air returned to a gaseous state and expanded. A chunk of insulating foam the size of a suitcase departed the tank. It didn't just slide off, as NASA thought it did based on past experience. The pressure of the expanding gas between the tank and the insulation blew it off "with considerable force."

The foam then did something that blatantly defied the design of the huge, orange external fuel tank. Instead of slipping away from the orbiter, it slammed into Columbia's left wing with enough force to punch a hole in it. It was that puncture which allowed super-heated gasses to breach the shuttle's heat shielding and led to Columbia's destruction on February 1st, 2003. The tragedy claimed the lives of all seven astronauts on board.

A New Problem

As they go over the remaining three space shuttles with all but a microscope, NASA has discovered a much newer problem: the rudder speed brake assembly on Discovery. Minor corrosion was found on the rudder actuators.

In addition, a gear installed when a backup assembly was last rebuilt had been installed backwards. Now, NASA is removing the actuators on Discovery, Atlantis and Endeavour.

Delays

Atlantis had been scheduled to initiate the shuttles' return to flight sometime between September and November. But now that NASA has decided to redesign the external fuel tanks and pull the speed brake assemblies, that deadline just didn't seem realistic.

"We said, 'Stop. Let's go ahead and extend the schedule, and let's figure out what the right way is to go about" meeting the recommendations of the Columbia accident investigators, NASA Administrator Sean O'Keefe said. "We're not going to be driven by the calendar. This is going to be a milestone-driven event."

Solutions

Readdy (right) said the fuel tank redesign would incorporate a new method of applying insulating foam, one that would hopefully eliminate air pockets between the tank and the insulation. Hopefully, that will help fix the problem that led to Columbia's fiery demise.

NASA last month decided to change the fundamental mission of the remaining shuttle fleet, devoting it entirely to completion of the International Space Station. It'll work like this: One shuttle will fly to the station. It will be completely inspected during the flight and while docked at the station. Another shuttle will be standing by in case a problem is found in orbit. While it won't necessarily be on the launch pad, Readdy says it will be ready to go within 90 days of a launch decision. That's typically how long the station's food and atmosphere can last with the usual crew of three and up to seven shuttle astronauts on board. In an extreme situation, Readdy says, a rescue shuttle could fly in as little as 35 days.

That would mark the first time since Skylab that NASA kept a spacecraft at the ready for rescue missions.

The solution wouldn't have worked in Columbia's case. America's oldest flying shuttle was too heavy to make it to the space station. It lacked the necessary fuel. But the newer shuttles are all capable of an ISS rendezvous.

Inspection work on Discovery is moving along more quickly than on its sister ships. Because of that, NASA has decided to make it the spacecraft which will initiate the return to flight on STS-114. Atlantis had been on deck before that decision was made. It will now serve as the backup spacecraft for the first Discovery mission, more than a year from now.

FMI: www.nasa.gov