A mathematical reconstruction
Air crash computer models are the mathematical representation of a craft, strung together from a mass of data, equations and computations designed to mimic its movement or behavior as it flies. Three-dimensional models include a graphical display that translates the numbers into an animation of the vehicle under scrutiny, a useful tool for investigators hoping to see how a plane - or shuttle - was flying before it crashed.
"A crash is like a puzzle," said Michael Poole, a managing partner with the flight safety software company FlightScape. Poole is a former member of the Transportation Safety Board of Canada whose FlightScape animation software is used by the NTSB, among others, to reconstruct airplane accidents. "You have to take all of this data and put it together. When you finally get it, it's like everything fits."
In the case of Columbia, investigators have a number of data sources to tap to generate a model. First, there's the shuttle itself, which relayed flight information sensor readings from all over the ship to ground controllers during its reentry. Ground-based radar and global positioning systems also kept close track of the shuttle's progress, with visual photos and videos offering another view to the craft's descent. Even the shuttle pieces that search teams dig up eventually help shape computer-generated Columbia mockup.
"Investigators can take all the pieces where they land and back them up into the sky in a trajectory analysis," Poole said. "It's not simple, but it can help determine the sequence of a vehicle break-up."
Since the location of debris is crucial to backtracking its fall from the shuttle, investigators have urged those who find any wreckage to leave it undisturbed.
Only some of the answers
Poole warned that while computer modeling can provide a good look at aircraft in its final minutes, there are some limitations to the technology.
"A computer model is not going to tell you why the shuttle disintegrated," he said. "It can tell you how the ship behaved though, which still useful in determining the cause of a [break-up]."
As an example, investigators studying the crash of Swissair Flight 111 in September of 1998 were able to use modeling to track a fire in the cockpit that caused the accident. However the model could not identify exactly why the fire started.
Columbia investigators could develop a group of scenarios that describe how the shuttle may have been destroyed, and then take measures in the future to prevent any of them from happening.
"Human nature wants to be able to identify the exact reason for this [break-up]," Poole said. "But if NASA can narrow it down to five scenarios for the [break-up], then they should just fix all five. That's safety."
Challenger
NASA has had only one other accident resulting in the loss of a space shuttle. On Jan. 28, 1986, the launch of the Challenger shuttle turned disastrous when it exploded just minutes after launch, also killing the seven astronauts it carried.
Investigations into the accident eventually pointed to a faulty O-ring in one of the shuttle's solid rocket boosters as the cause, but only after a painstaking process of debris recovery and analysis similar to that underway with Columbia.
"Most of the modeling comes up after you find the debris," said Ed O'Connor, who as an Air Force Colonel led the search and recovery for Challenger's remains.
O'Connor told SPACE.com that most of the Challenger investigation relied on visual recordings and radar analysis, not computer modeling, of the accident to determine what caused the shuttle explosion. Since Challenger exploded on launch, much of the debris rained down upon the Atlantic Ocean and was recovered and then sent to a hangar to be studied.
The Columbia Reconstruction Team, a NASA group trying to physically bring as much of the recovered orbiter together as possible, is doing the same thing now at Kennedy Space Center's Reusable Launch Vehicle Hangar.
"It's a lot easier working on low altitude break-ups though," O' Conner said, adding that Columbia investigators have a challenge in locating shuttle debris that fell from much higher - an altitude of about 200,000 feet - than the Challenger explosion.
The computing age
The basic computing behind air crash computer modeling hasn't changed since the Challenger accident, but the equipment has. Today's computers vastly outstrip their 1986 counterparts in performance and price, which allows computer modelers to work cheaper during an investigation. Flight analysis software designers use $2,000 computers today that run models much better than the $75,000 versions they used two decades ago, Poole said.
More powerful processors allow investigators to model potential crash scenarios quicker too.
"In those days, a lot of what we did was with hand calculators," O' Conner said of the 1986 Challenger investigation. "We really didn't have access to computer modeling on a timely basis."
But most of the software's advances have occurred in the realm of graphics, largely due to the demands of entertainment and video game markets. Real-time cockpit readouts and representations of aircraft, complete with moving surfaces and blinking lights, can paint a life-like view of a plane or its demise, blurring the line between known facts and fiction.
"In the mid-1980s, computer models of air crashes were purposely made to look like models," Poole said. "The plane then was a square blip on the screen. But now, you can render the whole plane, and some people even put in weather. I'd prefer the square blip, because you need to stay as objective as you can in an investigation."
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