"At this point, we're just trying to get it out to the public to not touch or tamper with this debris in any manner,'' said police spokesman Greg Sowell of the east Texan city of Nacogdoches on the afternoon of 1 February, "due to the possibility of toxic substances being on the debris.'' A city of some 30,000 inhabitants, located a few hundred kilometres northeast of Houston, Nacogdoches suffered the brunt of falling fragments from Columbia that day. Dentist Jeff Hancock, for example, was shocked when a metal bracket crashed through the ceiling of his office . . .
Elsewhere in Texas, Gary Hunziker in Plano, just north of Dallas, described his astonishment as he saw "two bright objects'' - obviously fragments of debris - flying separately on either side of the fast-moving Columbia. Still other eyewitnesses heard loud explosions that were variously likened to rolling thunder, sonic booms or "a car crashing into my house'' while others imagined that the United States was under imminent attack from terrorists or UFOs. It is perhaps one of the greatest miracles of that horrific day, however, that no one on the ground was killed or seriously injured.
Circumstances could have been very different. During the subsequent investigation, it was determined that had Columbia begun to disintegrate barely a minute earlier, three times as many people could have been exposed to falling debris. Unfortunately, NASA's options for avoiding populated areas in the event of a catastrophe during re-entry were, and still are, limited. To accomplish a landing in Florida requires one of two flightpaths: one carries the Shuttle over California and across the United States' heavily populated heartland, the other traverses Central America, close to the Yucatan Peninsula, and over the Gulf of Mexico.
Even diverting Columbia to Edwards Air Force Base in California would not have been inherently 'safer' in terms of people on the ground. Although most of the re-entry flightpath would have been conducted over the Pacific Ocean, an Edwards touchdown would have still required Husband to risk crossing heavily populated Los Angeles. In addition to concerns of public safety, questions also arose in the weeks after the disaster of what - if anything - could have been done to lessen the immense atmospheric heating on the Shuttle itself during re-entry. The answer: virtually nothing.
Had NASA known at an early stage in the 16-day mission that Columbia's left wing was fatally crippled and she would not survive the return to Earth, the only remotely viable option was to send Anderson and Brown on emergency spacewalks to remove all unnecessary hardware from the payload bay - including the Spacehab module and FREESTAR pallet - and dump them overboard. This would reduce the re-entry weight by around 15,000 kg, which would slightly lower heating stress during re-entry, but the vehicle itself weighed 90,000 kg and releasing the payload would not be nearly enough to prevent a catastrophic breakup.
Moreover, that work would require at least two lengthy excursions. Several NASA managers also doubted that Anderson and Brown could have safely got into a position over Columbia's payload bay wall to 'see' the wing damage, let alone do anything about it. ''Just the nature of them trying to position themselves in space underneath the vehicle'', said Dittemore, ''could cause more damage than we were trying to fix.'' However, when interviewed by the CAIB during the investigation, veteran spacewalker and six-time Shuttle flier Story Musgrave disagreed. ''It's not difficult and not dangerous. There is zero risk involved. It's a 15-minute walk. Another thing that's important is you've involved the people whose lives matter. You've involved them in the process of how you come home. There's a particular moral element to that.''
A 'rescue' flight by another Shuttle was considered a risky option, although many within NASA deemed it irresponsible to send another crew aloft when the malfunction that had doomed STS-107 was still not understood. Even as late as March 2003, Ron Dittemore and others doubted that a mere chunk of foam could possibly have been responsible for the disaster. Columbia's sister ship Atlantis was, on 1 February, almost ready to move to the launch pad for a scheduled International Space Station visit four weeks later. Could her flight have been radically changed at the last minute to rescue Husband's crew?
Technically, yes, but only on the assumption that the implications of the damaged left wing had been identified as early as the fourth day of the STS-107 mission. If that had happened, Atlantis might have been hurriedly readied for launch as early as 9 February with a skeleton crew of four - Commander Eileen Collins, Pilot Jim Kelly and Mission Specialists Soichi Noguchi and Steve Robinson - to rendezvous with Columbia and transfer spacesuits and carbon dioxide-scrubbing lithium hydroxide canisters from ship to ship in what would likely be an operation taking several days.
Fortunately, the extended-duration nature of STS-107 meant that the EDO pallet was housed in Columbia's payload bay; this would have enabled Husband's crew to remain comfortably aloft until 5 February, but if they conserved their consumables, shut down the science payload and reduced their movements they could have survived another 10 days. ''You just power down to give yourself more time,'' former astronaut Blaine Hammond has observed. ''You power down the orbiter to minimum levels and conserve as much as you can and you can stay up there 30 days with the minimum systems needed to keep the orbiter alive.''
Hammond also addressed fears that, without fully understanding what caused the initial damage to Columbia, the 'rescue' mission might itself suffer a similar fate. ''Then you've got to ask yourself how the shortcuts affect the safety of that flight,'' he said. ''You'd have to get a crew, but you'd have no shortage of volunteers to go up, but you're putting those guys at risk and putting another orbiter at risk by short-cutting all of the normal checks and inspections. To save seven lives, I think that's certainly a good trade-off, [but] you're putting a lot on the line.''
Sadly, such a rescue flight never came to pass, which former astronaut Mark Brown saw as a lost opportunity of Apollo 13-style proportions. ''I think it potentially could have been NASA's finest hour,'' the STS-28 veteran said. ''We could have made a heroic effort to try to bring the crew back.'' Nonetheless, some satisfaction arose from Laurel Clark's unfinished videotape that showed a crew living their dream and not realising until the final seconds that they were in mortal danger. It could have been a much more protracted and lingering end, according to space analyst Jim Oberg.
Had the crew known what was happening, their ambitious science mission would have been lost in its entirety, the joy of being in space would have been tarnished and if Atlantis' rescue flight had failed or been unable to reach them in time, they would have simply existed in space until their oxygen finally ran out. Within a couple of months, the eerily silent Columbia would have been gradually dragged into the atmosphere in a fireball. ''It would be visible at dawn and dusk and that would be pretty creepy,'' said Oberg, likening it to a Viking funeral.
As debris rained down from the Texan skies that February day, it might be supposed that all of the painstaking scientific research done during the STS-107 mission would have been lost forever. In most cases, it was lost, and its loss after such a highly successful flight proved devastating to many scientists whose experiments had taken years to develop. ''I hope they can salvage something,'' said biochemist Hideaki Moriyama of the University of Nebraska, who had supplied various protein samples as part of ongoing studies of HIV-AIDS, Huntington's and Parkinson's diseases. ''It took more than four years to prepare these experiments.''
Other scientists, including David Warmflash of JSC, who had been investigating bacteria cultures, regarded the loss of experiments as ''not in the same category as losing a crew''. However, in a final status report on the STS-107 research, released by NASA on 19 February 2003, it was revealed that experiments whose results were downlinked to Mission Control - primarily the combustion, materials science and fluid physics investigations - had returned between 50% and 90% of their data. Others, including the vast majority of the medical and biological experiments, whose specimens were to be analysed after Columbia's landing, were destroyed.
Except, that is, for one quite remarkable discovery.
In April 2003, searchers in a Texan field unexpectedly found a canister filled with a set of live moss and thousands of roundworms from one of the biological experiments inside the Spacehab module. The tiny, pencil-tip-sized worms, known as C. elegans, have typical lifespans of about a week and were actually the fourth or fifth generation of their forebears that were in orbit during Columbia's mission. Designed by researchers at Ohio State University and NASA's Ames Research Center in California, the experiment had been looking at new synthetic nutrients for the worms.
Another experiment of sorts that was recovered was Columbia - or, at least, debris from around 38% of her, weighing some 41,000 kg - according to Mike Leinbach, the chairman of the ship's reconstruction team at KSC. Unlike Challenger, whose shattered remains had been buried in a disused missile silo, it was decided that Columbia's fragments would be 'lent out' to qualified researchers seeking to design new hypersonic aircraft and next-generation spaceplanes. ''We're going to learn from Columbia,'' Leinbach said. ''This is the legacy we're going to leave the STS-107 crew and their families.''
The first set of debris loaned to researchers was shipped to The Aerospace Corporation of El Segundo, California, in June 2004, who conducted nondestructive tests to develop better analytical models for predicting the behaviour of composite materials during hypersonic flight. Of particular interest to the corporation's materials scientists were graphite/epoxy honeycomb skin fragments from Columbia's OMS pods and debris from her main engine and RCS helium pressurant tanks. According to researcher Gary Steckel, such information could provide insights into the kinds of wreckage most likely to survive re-entry and possibly present hazards to people or property.
"All the pieces that we have, we know where they were found,'' explained Steckel, whose group were lent the pieces for a year. "Based on the mass of those articles and their geometry, our people will do a trajectory analysis to try to figure out exactly where it was when it broke free. Once they've got that, the thermal history of the debris can be predicted. I'll be looking at what peak temperatures were seen, how much heating the debris saw and how that jibes with what other people predict.''
The first educational institution given permission to use debris from the spacecraft was Lehigh University of Pennsylvania which, in March 2005, received a loan of 50 fragments from NASA - including shards of windshield and wing pieces - as part of efforts to understand why certain components failed and how they responded under extreme hypersonic forces. Employing powerful electron and light microscopy, materials scientist Arnold Marder and his team hoped to identify "tell-tale signs of the mode of failure'' and possibly gain new insights into the design of future hypersonic spaceplanes.
For the three-man team on board the International Space Station - including former Columbia flier Ken Bowersox - the impact of losing their friends was profound. "My first reaction was pure shock,'' Bowersox told a space-to-ground news conference shortly after the disaster. "I was numb and it was hard to believe that what we were experiencing was really happening. As that reality wore on, we were able to feel some sadness.'' He added that Mission Control had reduced his schedule, along with those of his comrades Nikolai Budarin and Don Pettit, to give them time for reflection. "We've had time to grieve for our friends and that was very important. When you're up here for this long, you can't just bottle up your emotions and focus all of the time. It's important for us to acknowledge that the people on STS-107 were our friends, that we had a connection with them, and that we feel their loss, and each of us had a chance to shed some tears.'' The station crew was entering their eleventh week in orbit at the time of the disaster and was due to return to Earth on board Atlantis in mid-March 2003.
That changed abruptly on 1 February. Contingency plans had been laid before the Columbia disaster to run the station unmanned if necessary, but it was decided that bringing Bowersox's crew home and leaving it unoccupied would make it harder to cope with unexpected problems. Nonetheless, without frequent Shuttle visits, three-member crews could no longer be effectively supported and the option was taken to fly two-man 'caretaker' teams on six-month tours of duty to keep the station operational in the interim. The first caretaker crew - Russian cosmonaut Yuri Malenchenko and American astronaut Ed Lu - were sent aloft in April 2003.
In the temporary absence of the Shuttle, launching these crews to and from the orbital outpost was only possible using the Russian Soyuz spacecraft. As a result, on 6 May 2003 Bowersox and Pettit became the first NASA astronauts to return to Earth on a Russian spacecraft and land on foreign soil. They and Budarin also became the first crew to return safely to Earth in the wake of the Columbia disaster.
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