As NASA and independent investigators close in on the root cause of the Columbia disaster, one question lingers in the minds of many armchair analysts: What, if anything, could have been done to save the crew if engineers had known early on that the orbiter had a non-survivable breach in the leading edge of its left wing?
The answer, according to a detailed NASA analysis obtained by CBS News Space Consultant Bill Harwood, is that Columbia was doomed from the moment the wing was damaged, most likely during ascent, and that nothing could have been done to reduce the stress of re-entry enough to save the ship and its seven astronauts.
This does not imply that NASA wouldn't have tried. However, given the severity of the leading edge breach investigators now know was present at the start of Columbia's descent, there simply were no Apollo 13-class engineering rabbits to pull out of the hat.
"I have wracked my brains over this," LeRoy Cain, the entry flight director for mission STS-107, said in an interview. "There just was no way we were getting that vehicle back. If we'd gone and taken some pictures and done whatever else anybody could think of, it wouldn't have changed the outcome for Columbia."
NASA's oldest space shuttle was launched Jan. 16 on a planned 16-day science mission. Eighty-one seconds after liftoff, a large piece of foam insulation broke away from the ship's external fuel tank and hit the left wing's leading edge at some 450 mph.
While an independent investigation into the disaster is not yet complete, many engineers believe the foam impact, possibly in combination with other factors, damaged one of the wing's reinforced carbon composite panels, providing a path for super-heated air to enter the wing during re-entry Feb. 1.
In the wake of the resulting catastrophe, Cain was charged with carrying out an "entry options" review to determine what might have been possible to reduce re-entry temperature extremes, or loads. The study will be presented to shuttle program management next week.
Diverting Columbia to the international space station was never an option because the two spacecraft were in different orbital planes and the shuttle did not carry nearly enough fuel to make such a rendezvous.
Cain's review did not address the possibility of launching an emergency shuttle rescue mission. But engineers say they do not believe it would have been possible to get the next shuttle in the launch sequence — Atlantis — into orbit before Columbia's crew ran out of carbon dioxide-scrubbing lithium hydroxide.
Three options were evaluated in Cain's review but the best results were achieved in the third, most extreme scenario, one that assumed the astronauts dumped everything possible overboard to reduce the shuttle's weight to an absolute minimum while keeping barely enough fuel and other supplies on board to ensure a survivable landing.
As it turned out, that was the only viable option.
It is not a scenario flight controllers would ever actually implement in its entirety. It is fraught with extreme risk and major unknowns, risks that might well outweigh the threat posed by a damaged thermal protection system.
But the goal of the entry options review was to assess what might be possible, in theory, regardless of likely operational constraints.
The scenario assumed the astronauts, staging at least two emergency spacewalks, could dump 31,321 pounds of equipment and supplies overboard, including Columbia's pressurized Spacehab research module (18,071 pounds), a pallet of experiments in the cargo bay known as Freestar (4,428 pounds) and unneeded crew equipment (4,663 pounds). Another 4,159 pounds of consumables — propellants, hydrogen, oxygen, water, hydraulic power system fuel — also would have to be dumped or used up.
The scenario, called Scenario 3, requires numerous flight rule violations and would leave the shuttle at "absolute minimums in critical systems" with no de-orbit wave-off opportunities and only a minimal ability to cope with additional failures. But it did reduce the maximum temperatures associated with re-entry.
"When we messed around enough with the weight, we started to see some reductions, getting some thermal relief in a generic sense, which makes sense," Cain said. "If we bring the altitude down before we de-orbit, we're reducing the energy, if we get a bunch of weight off then we're reducing the energy. All that weight translates into energy dissipation we have to do during entry.
The study examined heating at three representative points on the orbiter leading edge and under belly. In an important caveat, all the scenarios assumed there was no damage to the shuttle's thermal protection system (TPS) because there are no computer models capable of accurately predicting how even minor damage might affect heating.
"One of the major, significant caveats to the whole thing is we did this for a nominal TPS," Cain said. "If I have exposed structure, then even getting rid of 32,000 pounds isn't going to save the day for me."
Even if the crew also oriented the shuttle so that the belly of the craft was in shadow for more than two full days prior to entry, "cold soaking" the thermal protection system and lowering its temperature by 65 degrees, the outcome would have been the same, occurring 37 seconds later.
During Columbia's flight, engineers concluded the foam impact during launch was not a "safety of flight" issue. As such, NASA managers did not request any spy satellite imagery to provide additional insight. Whether that was a good decision or not, the management team had no conclusive evidence that Columbia faced a serious threat.
But to have accomplished the extreme measures listed in Scenario 3, planning would have had to begin almost immediately, meaning NASA managers would have needed convincing proof a safety of flight issue did, in fact, exist, within a day or two of launch.
"There are certainly things that I can dream up where if you had some situation in flight that really put us in a bad situation, we're going to brainstorm and think of anything we can and at some point you've got to pick an option and go with it because you're running out of time," Cain said. "But for this case, I can't really imagine (that scenario)."
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