Date: 28 Dec 96 14:20:09 From: firstname.lastname@example.org (Robert J. Niland) Organization: SuperNet Inc. +1.303.296.8202 Denver Colorado References: 1
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Mark E. Ingram (email@example.com) wrote: > Granted that the chances of a significanly-sized meteor hitting an > aircraft are infintesimally small, does anybody here have any idea how > large such an object would have to be to penetrate a 747's center-section, > and serve as an ignition source? If, for the sake of argument, it is > proposed that a one-inch object were capable of doing this, then would it > also be possible that the entry damage caused by such a penetration would > be obscured by ancillary damage (and/or missing wreckage)? Estimates place meteoroid velocities, at airline altitudes, at subsonic, perhaps as slow as 200 mph. Guesstimates suggest that a fatal TWA800 rock would have to be at least baseball size, and more likely grapefruit or larger size. > Has this possibility already been totally discounted by the NTSB? I don't know that NTSB ever made a statement about it. I recall the FBI saying something about it being "mathematically possible" but extremely unlikely. The main problem with the meteor theory is that there are meteor-strike scenarios that are substantially more likely, but haven't been reported. To forestall another round of discussion, here's a summary from earlier this year. ____________________________________________________________________________ > It was a meteor... Mini-FAQ: rev 21 Nov 96 Of the "it came from outer space" theories on TWA800, the meteoroid theory is the only one that is even tenuously viable. The rest (#1-5) can be ruled out: 1. Speculative natural astronomical phenomena, such as a "soliton beam from a subspace nova implosion" can be ruled out on epistemological grounds (i.e. what is it we are trying to know here?). Anyone proposing such a theory has probably mistaken this discussion for a Star Trek episode. Unlike ST, in real life we don't make up physics to suit the weekly plot. 2. Space alien activity can also be ruled out on epistemological grounds. Anyone wishing to advocate an alien theory needs to demonstrate that space aliens exist, that they are hanging around Earth, that they have the capability to shoot down airliners with minimal residue, and that they would be likely to do so. They may use TWA800 evidence to support the proof. Keep in mind that they are using TWA800 to support their alien theory, not the other way 'round. 3. Earth-sourced space weapons (tests or mis-fires) can be ruled out on rational grounds. Although such weapons are possible, there's no indication that any capable of hitting an airliner are currently deployed. Further, the only countries who presently have the technological capability would be exceedingly unlikely to test it on a US flag aircraft. Such an attack would be more than adequate motivation for the US to revive its moribund ASAT programs (an outcome those countries would not desire), if not cause outright military reprisals. If rogue states like Iraq get their own space programs, then we'll have a different situation. 4. Re-entering Earth-source space junk can be ruled out. The U.S. Space Command, known as SPACECOM, tracks all orbiting junk big enough (which is pretty small) to show up on radar (so that the Space Shuttle and other LEO traffic can avoid it). Most tracked re-entering junk burns up well above airline altitudes. Those rare objects that start out big enough to reach the ground are well publicized, and their return predicted plus or minus a few days. Anything large enough to down a 747 would be well known. You could probably get insurance from Lloyds of London (a'la Skylab). 5. Comets and other highly luminous natural space objects can be ruled out. There's an active network of comet-watchers who would have predicted the fall and given the object a name. Being, it is thought, much less dense than rock, and probably made of frozen gases and liquids, comets would also have to initially be disproportionately larger than candidate meteors in order to still be threat at 13,000 ft. 6. That leaves space objects that are non-luminous prior to entry in the atmosphere (meteors). Let's examine the hypothesis in terms of relative target risk. * It is conceivable for a meteoroid to down an airliner. It takes a fairly large one to survive entry and have enough mass at terminal velocity. It also has to hit a vulnerable spot. Most burn up well above airline altitudes. Those that survive are much smaller than they were in space, have ceased glowing, have no luminous tail, have slowed to terminal velocity (estimates place this at 200+ mph) and are falling at a steep vertical angle. I think we can safely rule out bolides (exploding meteors) as well. Most explode well above air-lanes. Any with enough residual energy after the explosion, or which didn't explode until 13,000 feet, would have caused other effects in the region. There would probably be seismological reports. So our theory leaves us with simple a simple kinetic collision of a hot falling space rock and a mostly-aluminum flying machine. * Meteorites of various sizes frequently hit the earth's surface. Most land in the ocean (water being the largest target) and go unnoticed. The next largest group land on unoccupied land or ice sheet, and are also unnoticed. The point is that bigger and/or more numerous targets get hit more often than smaller and less numerous targets. When waiting for a "first time" event, a larger target class is more likely to be hit first before a smaller class (not certain, of course, just more likely). This is why no one was surprised that the first observed comet-planet strike was on Jupiter and not on Earth. Jupiter is a bigger target (both in cross-section and gravity-well). * Before an aircraft in flight was hit, one would statistically expect a parked aircraft to be hit by a comparable meteorite, since parked a/c greatly outnumber a/c in flight (by perhaps 100:1). Parked a/c, as a class, present a much larger target area to the incoming meteoroid flux, and thus are more likely to be hit first and more often. If we had regular reports of parked a/c being hit, we would be worried about those aloft. No such strikes have yet been reported, although I doubt the USAF is routinely checking the Davis-Monthan boneyard for meteor holes :-). * Before a parked a/c was hit, one would expect a moving surface vehicle to be hit, since moving surface vehicles (cars, trucks, buses, trains) greatly outnumber parked a/c. This outnumbering could easily be 100:1, or 10,000:1 over a/c in flight. No moving vehicle strikes have yet been reported. * Before a moving vehicle was hit, one would expect a parked vehicle to be hit, since they greatly outnumber moving vehicles, by 100:1 or so (now 1,000,000:1 vs a/c in flight). There has been a report of one parked vehicle being struck by a meteorite, and that rock was toward the small end of the size needed to down an a/c in flight. * Before a parked vehicle was hit, one would expect a structure (house, business, etc) to be hit, since the square footage of roofs exceeds that of parked vehicles. There has been a report of one house strike. * Before a structure was hit, one would expect many hits in farm fields and other observed terrain, and indeed such reports are common, at dozens per decade. The reported strikes seem to fit the estimated rate and distribution of meteoroids. The rate of strikes on various objects is proportional to their exposed area and exposure time. The meteoriod flux rate is low enough, and the target-size-risk for an airliner in flight is small enough, that an incident is seriously unlikely, although not impossible. There are more likely strike scenarios, and they haven't happened yet. The net odds of TWA800-vs-meteor are microscopic enough that no investigator need take any steps to "rule out" a meteoroid. The mechanical failure and sabotage theories on the whole are substantially more likely bets. On the other hand, if an otherwise unexplained grapefruit-size entry hole is found in the top of the reconstructed fuselage, then we would indeed have some physical evidence that would require consideration of the meteor theory, however low the numerical odds. I personally have no theory on TWA800. Regards, 1001-A East Harmony Road Bob Niland Suite 503 Internet: firstname.lastname@example.org Fort Collins Unless otherwise specifically stated, Colorado 80525 USA expressing personal opinions and NOT speaking for any employer, client or Internet Service Provider.