Absolutely No Concern For Entry

A week and a half into the mission, the Red Team members - Husband, Chawla, Clark and Ramon - had the opportunity to speak to the three-man crew of the International Space Station. By that time, Expedition Six Commander Ken Bowersox and Flight Engineers Nikolai Budarin and Don Pettit were entering their tenth week in orbit and, as far as they knew, would be returning to Earth in mid-March on STS-114. At the time of the ship-to-ship radio call, the station was flying over eastern Ukraine as Columbia soared high over northern Brazil.

''Columbia, this is Alpha,'' radioed Bowersox, identifying himself by the station's official callsign.

''Hey Alpha, this is Columbia, how you doing over there?'' replied Husband.

''We're doing great. We're so glad to see you guys made it into orbit,'' said Bowersox.

''We're glad to be here too,'' came Husband's answer. ''We're really excited to be able to talk to you guys, one space lab to another big old space lab on that beautiful station of yours.''

''I tell you, it's certainly an amazing place to live and to work,'' Pettit added. The conversation lasted a matter of minutes before the crews bade each other farewell and drifted out of radio contact. The following morning - 28 January - they both united with thousands of people on Earth in remembering the victims of the Challenger accident 17 years earlier. As Husband spoke of his crew's profound sadness at the loss of those seven brave lives, he could hardly have imagined that he,

McCool, Brown, Chawla, Anderson, Clark and Ramon would join their ranks in barely four days' time . . .

Two years later, everyone knows the root cause for Columbia's loss on 1 February 2003 and although the STS-107 crew were unaware that their ship was irreparably damaged, concerns had already been raised on the ground. Video footage taken during their climb to orbit on 16 January had clearly shown a briefcase-sized chunk of foam falling from the External Tank about 81 seconds after launch and impacting somewhere on Columbia's left wing. Debris of this kind had, however, been falling from tanks on virtually every mission since 1981 and few NASA managers were overly worried.

Nevertheless, the media had already latched on to the foam strike, to such an extent that an email was sent to Husband a week into the mission to advise him of what had occurred, lest he be caught off-guard if asked about it during a space-to-ground press conference. The email informed him of the strike and assured him that, after painstaking analysis by experts on the ground, any damage to the wing was expected to be superficial and there was ''absolutely no concern for entry''.

Rick Husband thanked the sender of the email, Flight Director Steve Stich, and pressed on with his mission.

LAST DAY

On 30 January, as the science crew wrapped up the final few experiments in the Spacehab module, a quick peek was taken under its floor to make sure that the balky dehumidifier would not leak during re-entry. No moisture was found. The following day, the entire crew shut down FREESTAR and the module and Husband, McCool and Chawla tested Columbia's steering thrusters, hydraulics and other systems that would be needed during their descent towards a Florida touchdown.

After lauding the success of the mission, Entry Flight Director Leroy Cain -whose words from Mission Control would become almost as famous as Apollo 13's ''Houston, we have a problem'' over the following days - announced that the STS-107 crew would return to Earth on 1 February. Weather conditions at KSC were predicted to be excellent and ''this [entry] will be a very good visual sighting for folks, particularly on the West Coast, as well as in [the] mid-Arizona, New Mexico area. It should be a pretty spectacular event for folks that have never seen a Shuttle sighting, particularly at night.''

It was, indeed, going to be a spectacular sight, although not as Cain had intended, and certainly not a sight that anyone watching would want to see again. For the seven astronauts, however, as they readied their ship for landing and packed away their equipment, the mood was one of jubilation at a job well done. ''Science-wise, this flight's been absolutely fantastic,'' said Anderson. ''I think a lot of our experiments have exceeded our expectations by one hundred percent. We've seen things we never expected to see.''

Early on 1 February, the crew donned their orange pressure suits and took their seats for the hour-long glide to Earth. On the flight deck were Husband, McCool,

Chawla and Clark; the others would occupy seats on Columbia's locker-studded middeck. Although Chawla was the flight engineer, responsible for helping the Commander and Pilot monitor the systems, it was Clark's job to assist her. Ironically, Clark's words to an interviewer shortly before launch give an unsettling insight into the increasingly desperate situation in the cockpit as the crew realised they were in deep trouble.

''[Kalpana] helps the Commander back up his systems if anything is unusual with their systems, and [I] back up the Pilot,'' she said. ''I work with Willie, monitoring the electrical power systems and hydraulic systems; I have a computer screen near my seat where I can monitor the overall health of the vehicle and pick up any problems that might be occurring early on or once we see any kind of a malfunction or anything unusual that's happening ... [although] most of the time, you don't have to do much, other than monitor the normal entry profile.''

At 1:15 pm GMT on that fateful Saturday, as the ship flew upside down and backwards 270 km above the Indian Ocean at a speed of more than 28,000 km/h, Husband fired the OMS engines in an irreversible burn to drop Columbia out of orbit and place her on course to land in Florida exactly an hour later. For the first 30 minutes of re-entry, the ship simply fell like a stone through orbital darkness towards its predetermined runway on the other side of the planet. So far, true to Clark's prediction, the crew was following a 'normal' re-entry profile.

The second half of re-entry, however, was far more interesting as compression of the steadily thickening air at hypersonic speeds produced a brilliant light show outside the flight deck windows.

''That might be some plasma now,'' McCool remarked as he glimpsed the peculiar, salmon-coloured glow that gradually replaced the pitch blackness he had become used to over the last 16 days.

''Think so, already?'' asked Clark from her seat directly behind the Pilot, as she aimed a handheld video camera through Columbia's overhead windows.

''That's some plasma,'' confirmed Husband.

''Copy, and there's some good stuff outside,'' replied Clark. ''I'm filming overhead right now.''

''Oh, it'll be obvious when the time comes,'' Husband told him. Minutes later, the glow steadily brightened and McCool told Brown, Anderson and Ramon down on the middeck that he could now see vivid orange and yellow flashes across Columbia's nose. In the chatter that followed, Husband likened what he was seeing to ''a blast furnace''. The time was 1:44 pm and the Shuttle had reached an altitude of around 120 km as it hurtled over the eastern Pacific, nine minutes from the California coastline and a continent away from its landing site in Florida.

Flying with her nose angled upwards to subject her reinforced carbon-carbon nosecap and the leading edges of her wings to the most extreme re-entry temperatures of close to 3,000 Celsius, Columbia was still dropping at more than 24 times the speed of sound as aerodynamic pressures on her steadily doubled, then tripled, then quadrupled. Aware of the intensely dangerous situation they were in, but unaware of the fact that their ship was fatally damaged, Husband's crew calmly donned their gloves, pressurised their suits and conducted communications checks. Armed with her camera, Clark planned to videotape the entire re-entry.

At 1:50 pm, with the computers still flying the vehicle, Columbia's right-hand RCS jets automatically fired to adjust the position of her nose. This was one of several manoeuvres designed to bleed off speed. Three minutes later, precisely on time, she crossed the California coastline and ground-based observers were able to watch her streaking, meteor-like, across the night sky, ''at incredible speed'', according to freelance photographer Gene Blevins. It was around this time, however, that he and colleague Bill Hartenstein saw something strange: ''a big red flare [came] from underneath the Shuttle and [was] forced downward ... something came off the Shuttle!"

A continent away, at the KSC viewing site, the crew's families, Israeli dignitaries and high-level NASA managers - including Administrator Sean O'Keefe and his new Associate Administrator for Space Flight, Bill Readdy, a former Shuttle Commander - had begun to gather on a beautiful Florida morning for the landing. STS-107 was the first of six missions planned for 2003: the others would be exclusively dedicated to assembling the International Space Station. In fact, assuming everything went as planned on those missions, the station's football-field-sized truss structure and electricity-generating solar arrays should be in place by the end of the year.

That would allow research on board the outpost to commence in earnest: the European lab, Columbus, was due to be installed in October 2004 by the STS-123 crew and the Japanese lab, Kibo, would follow over three missions a year later. Columbia was expected to have a minor, though important, role in the continuing construction work: she would carry a piece of starboard-side truss known as the 'S-5' segment into orbit in November 2003, fly the final Hubble servicing mission in April 2004 and then deliver logistics and a new crew to the station in January 2005.

All that changed abruptly a few minutes before 2:00 pm GMT on 1 February 2003 as Columbia's otherwise-normal re-entry profile began to go horribly wrong.

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