Post by Chicago Astronomer - Astro Joe on Jul 27, 2004 3:30:55 GMT -6
The following account is deemed a rather graphic accounting for the last moments of the Shuttle Columbia. If you are easily disturbed, I recommend that you go on to something else. But it is part of the tragedy, hopefully never to be repeated again.
As we investigate the reasoning of the STS-107 breakup, we cannot ignore the horrible fate of the crew. Here is an account of the final moments of not only the Columbia, but the Challenger crew.
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Was Columbia in reentry LOS at the time of breakup?
No. Both voice communication and data telemetry were still being received right up to the breakup of Columbia. Unlike previous manned programs - Mercury, Gemini and Apollo, as well as the Russian Soyuz vehicles - the Shuttle does not have a loss-of-signal phase during reentry. The reason is actually pretty simple.
First off, understand that the blackout period is caused by a sheath of ionized air, formed during the high-heating, high-deceleration phase of re-entry, through which radio waves cannot penetrate. This is what every manned flight from Mercury thru Apollo experienced, and provided much of the suspense and drama during the reentry phase of John Glenn's Friendship 7 Mercury flight. Even the Shuttle experienced the same effect during its early flights.
The communications loss due to the blackout period was resolved after the second Tracking Data and Relay Satellite (TDRS) was placed in orbit. The reason is that the ionization sheath is open at the trailing end behind the Shuttle, providing a hole through which communication with the shuttle can be maintained with the favorably positioned TDRS. This second TDRS also allows communication during the other portions of entry that did not exist prior to its placement in 1988 - a period roughly from the time of the de-orbit OMS burn to an altitude of 200,000 feet for a landing at Edwards Air Force Base, barring passes over ground sites.
So, with two functioning TDRS satellites in operation, communications with the Shuttle can be maintained throughout the entire reentry phase of the mission.
What happened to the crew when Columbia broke up?
Actually, it's better to speculate on the fate of the crew cabin, and then decide for yourself what probably happened to the crew.
Once the cabin tore loose from the rest of the fuselage and all electrical power was lost, the cabin was probably hammered, buffeted and braked by atmospheric drag as it continued its re-entry. The cabin would have been heated by the surrounding shock-induced plasma, and as G-forces built up the integrity of the heat-weakened aluminum infrastructure would have been compromised and the cabin would eventually collapse in on itself. Some fragmentation would have no doubt taken place, and pieces would have broken loose and fallen behind and below the cabin's path as they slowed down quicker in the atmospheric drag.
This speculation is based on some of the findings of the investigation into the loss of Challenger in 1986. As with Columbia, the initial impressions on the fate of the Challenger crew was that they had perished instantly when the shuttle came apart a minute after launch. However, when the crew cabin was found relatively intact a few months later did it become apparent that the cabin had in fact separated cleanly from the fuselage, continued on a parabolic arc to an altitude of ~65,000 feet, and then fell back to impact in the Atlantic Ocean with a force of 200 G’s. Even then, the cabin was still relatively intact despite hitting the surface of the ocean with that degree of force.
When the cabin broke loose from the rest of Challenger, it became separated from all electrical and life support resources. Save for a few seconds of air in the lines, very shortly after separation the crew would have been without any life support. Upon recovery it was found that the state of some life-support equipment indicated that at least some of the crew had survived the initial breakup were able to activate their safety equipment. Three of the four Personal Egress Air Packs (PEAP) located behind each seat on the Shuttle had in fact been activated. However, because the crew were not wearing any sort of pressure suits, the PEAPs would not have provided the required amount of breathable air necessary to retain consciousness at the altitudes the cabin reached. The team of coroners and medical specialists that performed the autopsies of the remains concluded that that the crew were soon all unconscious shortly after the cabin began its final arc of transit, and were most likely not killed until the impact with the ocean, two minutes after the External Tank exploded.
It should be noted that since the loss of Challenger, many of the contingency plans were revised extensively. As a result, Columbia’s crew were equipped with better survival gear, including pressure suits and personal parachutes. Assuming they were conscious of the emergency, the Columbia crew would have closed their visors when cabin pressure was lost, which would have automatically pressurized the suits. At that point, the only thing the crew would have needed to do would have been to wait until the cabin fell below 15,000', blow the escape hatch, extend the egress pole, slide out and away from the orbiter down the pole, and parachute to safety. This is how the procedure works in theory, and provided the cabin stayed relatively intact until 15,000'. Since this did not happen, it can be assumed that the cabin was compromised in such a way that the crew had no opportunity to attempt any sort of egress.
In Hemphill, searchers found what are believed to be human remains, and what appeared to be gauges and other Columbia components in a farmer's field on 2/10/03. Although no details were given on the human remains, over 100 pieces of debris ranging from gauges to switches and other components, many of which still had the wires attached to them. Remains that a hospital employee identified as charred torso, thigh bone and skull on a rural road near other unspecified debris in Hemphill, east of Nacogdoches. Remains identified as a charred human leg on a farm in Sabine County, about 50 miles (80 km) east of Nacogdoches
