They did not have a docking ring. Would have had to transfer via space walk.
Foam that damaged tiles was re-formulated to eliminate freon.
------------------------------------------------------------------------Posted on Tue, Feb. 04, 2003
FOAM HAS PLAGUED NASA FOR 5 YEARS
By Curtis Morgan, Manny Garcia and Ronnie Greene
Knight Ridder
MIAMI - NASA engineers have known for at least five years that insulating foam could peel off the space shuttle's external fuel tanks and damage the vital heat-protecting tiles that the space agency says were the likely ``root cause'' of Saturday's shuttle disaster.
The Jan. 16 launch wasn't the first time that Columbia's fragile tiles were pummeled by chunks of foam. It happened on the spacecraft's first launch, and again, more severely, in 1997.
NASA and other researchers have been studying the problem of foam ``shedding'' from the shuttle's giant external fuel tanks for years, but the space agency's managers never considered the problem a serious threat to flight safety before Saturday's catastrophe.
The shuttle's towering tanks are covered with sprayed-on insulation that's designed to keep their super-cooled nitrogen and oxygen fuels at the necessary temperature.
Engineers typically find some damage to the orbiter's 24,000 ceramic tiles after missions, averaging about 40 ``hits.'' The tiles lining the craft's belly can withstand searing 2,300-degree heat during re-entry, but they are relatively fragile and easily damaged by flying debris or by ice chunks that form on the fuel tanks.
1997 flight had 308 hits
NASA engineers who examined Columbia after a 1997 flight found 308 hits, according to a Dec. 23, 1997, report by NASA engineer Greg Katnik, a mechanical systems engineer at the Kennedy Space Center at Cape Canaveral, Fla., whose team is responsible for the shuttle's external fuel tank, thermal protection shielding and other critical systems.
An investigation traced much of the damage to a ``massive material loss on the side of the external tank,'' Katnik wrote in an article in ``Space Team Online'' that was reprinted on a space-related Web site.
Katnik called the damage ``significant'' -- 132 hits were larger than an inch in diameter, and some slashes were as long as 15 inches. More critically, some penetrated three- quarters of the way into the two-inch deep tiles, close to the orbiter's aluminum skin, which can burn at only 350 degrees.
In all, more than 100 tiles had to be replaced.
``Foam cause damage to a ceramic tile?!,'' Katnik wrote. ``That seems unlikely, however, 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.''
Investigators are now examining the issue as they try to understand why Columbia disintegrated more than 200,000 feet over Texas, killing all seven astronauts aboard.
During the Jan. 16 launch, cameras recorded a fragment of insulating foam from an external fuel tank nicking Columbia's left wing. NASA staff and experts studied the event but concluded that it did not threaten the lives of the astronauts aboard Columbia.
Yet with the shuttle just minutes from Florida, the orbiter exploded.
While NASA stressed that it has not reached any definitive conclusions, the agency now says that nearly three pounds of hurtling insulation may have shattered the protective tiles.
``We're making the assumption that the external tank was the root cause of the accident,'' said Ron Dittemore, the shuttle's program manager.
Environmental issue
In his 1997 report, Katnik noted that the 1997 mission, STS-87, was the first to use a new method of ``foaming'' the tanks, one designed to address NASA's goal of using environmentally friendly products. The shift came as the U.S. Environmental Protection Agency was ordering many industries to phase out the use of Freon, an aerosol propellant linked to ozone depletion and global warming.
As recently as last September, a retired engineering manager for Lockheed Martin, the contractor that assembles the tanks, told a conference in New Orleans that developing a new foam to meet environmental standards had ``been much more difficult than anticipated.''
The retired Lockheed engineer, who helped design the thermal protection system, said the switch from a foam based on Freon -- also known as CFC-11 -- has ``resulted in unanticipated program impacts, such as foam loss during flight.''
In fact, he noted, the hits to Columbia on that 1997 mission, the same one Katnik studied, forced NASA to replace nearly 11 times more damaged tiles than it had after a previous mission that had used Freon-based foam.
Lockheed spokesman Harry Wadsworth said Monday that the company was referring questions to NASA. ``I cannot talk about any past problems with foam or the history of foam,'' he said. ``We're not talking about the investigation.''
Despite the concerns, NASA has never described the foam problem as a potential catastrophic threat, but considered it enough of an issue to warrant a series of tests.
In 1999, the Southwest Research Institute, a non-profit laboratory in San Antonio, Texas, fired insulating foam fragments from a compressed-gas gun into thermal tiles and recorded the results with digital cameras. After the Columbia crash, NASA asked the institute not to release those results. The space agency also has tested the foam in wind tunnels and aboard a research jet. |
