by John Tedesco
EXPRESS-NEWS STAFF WRITER
THE COLUMBIA CATASTROPHE
All content (c) San Antonio Express-News
HOUSTON — A week after fiery debris streaked across a clear Texas sky miles above Earth, answers to what caused the shuttle Columbia disaster seem just as distant and out of reach.
Thousands of pieces of debris have been recovered and reams of data have been examined, yet few clues have emerged.
NASA is embarking on a tedious phase in its investigation in an attempt to pursue every lead, every theory that possibly could explain why seven astronauts perished.
One premise — that a chunk of orange insulation foam broke from the shuttle’s external tank during liftoff and damaged thermal tiles that protect the left wing — continues to baffle investigators.
A NASA camera filmed the foam’s impact during the Jan. 16 launch. Engineers estimated the debris was 20 inches long but posed little risk.
As the Columbia began its descent Feb. 1, hurtling through the upper reaches of the atmosphere 18 times faster than the speed of sound, sensors aboard the left wing began to record heat spikes. Some of the sensors, for reasons still unclear, shut down altogether.
Critical sensors were located in the left wheel well, and one was positioned in the fuselage above the wing.
Meanwhile, the Columbia’s steering thrusters kicked in, trying to compensate for unusual drag on the left wing.
In the last radio transmission from Columbia, flight commander Rick Husband calmly acknowledged sensor readings in the left tires had been lost. Then came static and silence.
NASA officials said it would be premature to link the impact of foam debris at the start of the mission to wing problems at the mission’s tragic end.
“Be cautious about drawing conclusions,” said Ron Dittemore, NASA’s shuttle program manager.
Other theories include some unknown event, a structural failure in the shuttle or a collision with space junk.
Defense Department radar shows an object or material coming off the Columbia one day after launch, NASA confirmed Saturday. The significance of the imagery isn’t known, a spokesman said.
Investigators are looking at the inflight schedule to determine whether the debris might have come from a routine dump of waste water or other supplies.
The material appeared to leave the shuttle at a rate of about 5 meters per second, according to CBS News.
While the source of a possible collision was unknown, what’s clear is how NASA has grappled for years with the ceramic tiles, which can deflect tremendous amounts of heat but also are delicate and difficult to replace.
“Our greatest concern with tiles is damage,” Bob Speece, a member of NASA’s debris team, wrote Aug. 10, 1999.
Speece recounted how the shuttle Atlantis sustained “much tile damage” from debris during a 1988 mission. A metal antenna cover was burned during re-entry.
“The tile system protects critical areas on the shuttle such that if a ‘burn-through’ occurs, the results could be catastrophic,” Speece wrote.
Studies backed him up.
“Since the first flight, the orbiter has always been exposed to external debris damage,” concluded a December 1990 report by researchers at Stanford and Carnegie-Mellon universities.
From 1981 to 1990, the number of hits on shuttle missions varied radically, ranging from just a handful to 250. Most of the debris came from insulation foam that covered the external tank, the study determined.
Researchers identified tiles that protected crucial parts of the shuttle, such as the wheel wells. The failure of those tiles was more likely to jeopardize a mission.
The study also found damaged tiles were a costly hindrance — time constraints between missions pushed the limits of staffers who had to re-apply new tiles, one by one, to the shuttle’s underbelly.
Foam is sprayed on the large external tank to insulate 540,000 gallons of frigid fuel and prevent ice from forming on the metal surface.
In 1997, Freon was removed from the foam mixture to make it more environmentally friendly. That same year, the Columbia suffered an alarming number of debris hits, according to a report by Gregory N. Katnik, a shuttle technical manager.
Katnik wrote that the Columbia’s tiles suffered 308 hits during the mission, nearly eight times the typical 40 hits. Foam was determined to be the primary suspect.
Although it’s a light substance, Katnik wrote, “when that foam is combined with a flight velocity between speeds of Mach 2 to Mach 4, it becomes a projectile with incredible damage potential.”
According to the shuttle program’s 1999 annual report, NASA installed a camera on the shuttle to document foam debris and its impact. Officials said the foam now is poked with holes before liftoff to allow venting to occur, which has diminished the number of projectiles.
With NASA concentrating on other possible causes, some experts say the agency should focus more intently on the possibility that lightweight foam ultimately was responsible for bringing down a multiton spacecraft.
They questioned NASA’s assumptions, particularly that ice wasn’t lodged in the debris when it struck the Columbia.
Paul Czysz, a former professor of aerospace engineering at St. Louis University, pointed out how the metal shell of the external tank stores fuel hundreds of degrees below freezing.
If a small amount of moisture had seeped into the foam and froze, the added weight could create a dangerous projectile.
Even if ice wasn’t present, the piece of foam that struck the Columbia’s wing was believed to be especially large — bigger than other pieces that hit shuttles in the past.
“If that foam was heading at me at 800 miles an hour, I’d duck,” Czysz said.
NASA officials said their engineers have viewed footage of the foam’s impact after the launch and, as the Columbia orbited the earth, they determined from the video and past experience that the shuttle sustained no serious damage.
But the belief was based on limited information, NASA acknowledged. The camera with the best angle of the shuttle launch was out of focus. And on Saturday, the Washington Post reported that Boeing Co. engineers had conducted their own analysis during the mission.
They found NASA’s conclusion about the foam was drawn from uncertainties. No one knew for sure whether ice was imbedded in the debris, nor did anyone know if the leading edge of the wing was struck — a scenario that could prove to be a serious safety risk.
The result of NASA’s investigation could decide the fate of the grounded space shuttle fleet and the future of an agency that some say has lost direction.
The thrilling days of trying to land a man on the moon occurred more than three decades ago. There are no presidential mandates to explore new frontiers, only costly launches into low orbit.
The shuttle was intended to be the pinnacle of efficient space flight. But the vision of frequent, cheap launches never materialized, and NASA now grapples with rising costs of the aging machines.
A 2001 annual report by the Aerospace Safety Advisory Panel found NASA has enacted excellent safeguards, but added that funds intended for long-term safety concerns were being used instead for normal operations.
On April 18, 2002, the former chairman of the safety panel testified at a congressional hearing that trends in the shuttle program were troubling.
“In all my years of involvement, I have never been as worried for space shuttle safety as I am right now,” Richard Blomberg testified on Capital Hill.
“All of my instincts suggest that the current approach is planting the seeds for future danger,” he added.
jtedesco @ express-news.net