Columbia, What Might Have Happened
See also www.antipeonage.0catch.com
A Tribute to Heroes Why We Fly It's Not Face Mountain, It's the Slag Pile 12 Miles From Face Mountain
Or go to mars.jpl.nasa.gov/mgs/msss/camera/images/01_31_01_releases/cydonia/ and download Photo M18-00606 and look at the Slag Pile. Look at the ground immediately to the east of the Slag Pile. We better find out what that is.
I was a student at the University of Washington when the Columbia first went up. At that time, I had been accepted into the engineering program and most of my schedule was in engineering classes. One of the professors apparently performed consulting work for NASA or for Rockwell, the contractor who built the Shuttles. During Columbia's first flight, he brought a prop to class. It was a slab of aluminum, about a square foot, upon which was glued a layer of insulation and a ceramic tile. We discussed the technical problems faced with trying to keep such tiles from falling off the shuttle during the ascent, when the giant Morton-Thiokol solid fuel boosters would shake the ship with extreme vibrations.
In spite of the absence of some of the tiles, the Columbia came down and safely landed at Edwards Air Force Base in California. Because of this experience with the tiles, many people believe that a massive loss of tiles is what doomed the ship. They have never solved the problem of the tiles. Every time the Columbia was launched, tiles fell off. If you wander the fields and marshes of Cape Canaveral and manage to avoid the security guards and police, you might find Columbia tiles in the grass and the reeds. This one was there since 1984, that one has been there since 1996. Because of the problems with the tiles, the newer Shuttles such as Atlantis and Endeavour are made with a different heat shield system, involving large pieces of ceramic covering large areas of the ship.
What would have happened if there was a substantial area of the ship exposed to a loss of tiles, perhaps near the wheel wells and the wire bundles leading to the sensors on the left wing, can be deduced from the design of the ship. The basic structure of the Shuttles is essentially the same as the basic structure of most aircraft built since B-17 days: 7075 aluminum alloy structural members tied together with steel fasteners. When I worked for The Boeing Company, that is part of what I worked with. The frame of the Shuttle, its body, the wings, the vertical fin, and the large hinged doors, are made of 7075 aluminum and steel fasteners. Over the frame is the aluminum skin to which the tiles are fastened. This aluminum skin is made of 1/10 inch thick sheet, chem milled down to a few hundredths of an inch away from the fastener locations to save weight. The passenger cabin up front is made of 6061 aluminum which is welded. 7075 cannot be welded, 6061 is the alloy of choice when welded seals are desired. Thus the passenger cabin can contain air at 14 psi while in space.
In the event of direct exposure to the high atmosphere between 100,000 and 400,000 feet at over 20,000 feet per second, the aluminum skin would warm up to melting temperature in only a few seconds. This heat would transfer rapidly to the structure. Aluminum and steel transfer heat rapidly. Everything attached to the aluminum structure would immediately feel the heat. Thus the reports of tires in the landing gear losing pressure, they ruptured. Temperature probes would report the increasing temperature and then go silent as either they or the wire bundles leading to them would fail.
Aluminum melts at 1,220 Fahrenheit. The structural members are like soft clay at temperatures below that. The wings and other parts would fall off when the structure was soft enough to no longer hold against the stresses and loads of re-entry. Once the parts fall off, the big gaping wounds in the ship would be exposed to the thin air moving past at over 20,000 feet per second. The heat would quickly transfer to the passenger cabin and turn it into an oven. I like to believe that the cabin ruptured exposing the astronauts to the extremely low pressure of 207,000 feet. That way they suffered as little as possible under the circumstances.
But unfortunately, I do not believe the theory that a massive loss of tiles led to the breakup of the ship is probable. Had there been such, they would have seen it, and would have known about it. (I am disturbed by the report that they sent them up without the Canadian arm. The double jointed 50 foot Canadian arm with its camera has been used to inspect for tile damage.) We would not have had the glowing reports of another successful mission. Instead it would be an Apollo 13 scenario, NASA and Russia's space agency working to bring the astronauts back alive. If they could get to the International Space Station, a re-entry need not be attempted to save the astronauts from starvation. (I am disturbed by the report that they sent them into an orbit where getting to the Space Station is difficult or impossible. A reasonable contingency to plan considering we spent the money to have it up there. Too bad the Russians could not have kept Mir in orbit, it could have served as a second emergency stop for damaged Shuttles.) Two or three of them could drop down to Kazakhstan in the Soyuz capsule. Soyuz ships and other Shuttles could rise to relieve the crew and carry parts such as replacement tiles to repair a damaged Shuttle.
What I believed happened is the kind of failure that cannot be avoided by the most careful maintenance: fatigue fracture. It may be that the peak loads experienced by the Shuttles during their flights are greater than estimated and calculated by the engineers at Rockwell. If so, then the fatigue life of each structural member is not as long as originally estimated. It is the kind of problem that would show up without warning many years later.
Metal fatigue is the mechanical and structural engineer's nightmare.
What would happen in a fatigue failure is that the metal would split. This could cause a big gaping hole in the aluminum skin attached to the split member and the tiles over it. Thus exposed to air friction at re-entry speed, the already damaged aluminum structure would experience the scenario above described.
If this is the cause of the accident, then we would have to ground the entire Shuttle fleet. Permanently.
That is why I hope this is not the problem.
I read a news report, (February 14, 2003) that the body sustained a significant rupture.