Public hearings

On Thursday, March 6, a key feature of the Gehman Board's strategy for gathering information will kick off with the first public hearing.

Though the details of the hearing have yet to be announced, including who the first set of witnesses will be, the Board has said the inaugural hearing will be hosted by the University of Houston in Clear Lake, Texas. The university is located close by to NASA's Johnson Space Center here.

The hearing itself, according to Gehman, will be in divided into two parts.

"The first part will be to hear from witnesses that we call to essentially read matters into the record," Gehman said. "That is, if there are substantive or factual matters that have come before the board and we want to publicly disclose them as the process goes on, we'll do that in a public forum under the process of a public hearing."

The second part of the hearing will involve seeking theories about what happened to Columbia and why.

"We will invite experts who are not associated with any U.S. government program, who have theories or hypotheses, who have written to us or provided papers or research documents, to come and express to us their opinions," Gehman said.

Though the board has vouched for the credibility of experts, it's not yet clear who those people will be or how they will be selected.

Additional public hearings are expected during the coming weeks, with two hearings per week tentatively scheduled. In addition to Houston, hearings could be held in locations such as Florida, California and Washington, D.C.

Just the facts

While news this past week centered on engineer's e-mails discussing worst-case scenarios for dealing with Columbia's landing gear, the electronic conversations offered nothing new in terms of determining the cause of the tragedy.

The same can be said of Friday's release of the videotape that showed four of Columbia's seven astronauts working their way through re-entry. While somber viewing to those aware of what followed, the tape itself offered no new insight into the tragedy.

Twenty-eight days after the destruction of Columbia, the following facts are known:

About 81 seconds after launch on Jan. 16, material believed to be foam insulation fell from the shuttle's external tank and struck Columbia's left wing in at least two, possibly three locations.

The event was captured on film and became the subject of intense analysis during the two week duration of the mission, ending with the conclusion that although Columbia's skin might become damaged, there were no concerns about losing the vehicle or crew.

The best ideas

Again, no one knows yet exactly what happened or why, and the board has cautioned the public and the news media not to get too focused on any one theory.

"We're entering this with no assumptions," said Air Force Brig. Gen. Duane Deal, a CAIB member. "We're not assuming anything is broken. And we're not assuming everything is solid, 100 percent. Our duty is to examine everything objectively," That said, the easiest theory to believe is that the foam insulation damage to Columbia's left wing was more severe than predicted, allowing a hole to open up either along the leading edge of the wing or underneath near the main landing gear door."

Another candidate is that random orbital debris struck the left wing -- perhaps initiating the debris that was seen floating away from the shuttle. In the same way, a hole in the left wing allowed the re-entry heat inside and doomed the shuttle.

There has been some talk that Columbia's left wing flew differently than other wings in the shuttle fleet because it had a rougher exterior, which at hypersonic speeds makes a difference in the way heat builds up. It's possible that fact combined with potential damage to the tiles led to disaster.

A more exotic theory is that some kind of electrical discharge damaged the composite material that makes up the leading edge of the wing, again creating a hole through which hot gas gets inside and rips apart the wing from the inside.

Board members have also said that in addition to finding a single cause of the accident, it's possible there are contributing causes as well, not necessarily technical in nature.

Decision-making processes, management policies, organizational issues and other non-engineering-related possibilities will be looked at and could be cited.

"It's well known that accidents in complex systems often involve a chain of events. It's not often one single thing that caused the whole accident,"  said board member Scott Hubbard.

Return to flight

Depending on what the Gehman Board determines are the causes and contributing causes of the accident, NASA could be in a position to return flying in a matter of just a few months -- or it could be a lot longer.

Two key questions need to be answered:

• What kind of technical changes need to be made to the shuttle before the problem is fixed?

• What kind of operational changes need to be made to the shuttle program before officials will approve a return to flight?

This is the wild card in building a return to flight plan and several possibilities present themselves.

For example, it could be that the Gehman Board -- or perhaps members of Congress -- will dictate that NASA cannot resume flights unless the space agency has a foolproof way to inspect for tile damage in orbit and repair any tiles that could threaten the mission.

While technically not impossible, it would require development of new hardware that could take months to produce and some extra amount of time to train the astronauts.

It also could require that every future shuttle mission must go to the International Space Station (ISS) where such an inspection could easily be made.

At present, except for a planned mission to service the Hubble Space Telescope, all shuttle missions are destined for the ISS.

Nevertheless, even using the station's robot arm in concert with the shuttle's arm, there still are some areas of the shuttle's belly it might be tough to reach with a tile repair crew.

At the extreme end of possibilities, NASA could be tasked with never launching a shuttle unless another shuttle was stacked and ready to fly a rescue mission.

Such a requirement would nearly strangle the program. However, depending on how much risk the nation is willing to accept as expressed by its leaders, the idea is technically possible.

But for now, such wild concepts are not on the board's agenda.

"It's far too early to begin thinking about those types of things," Gehman told SPACE.com. "That would really be getting ahead of the game."