Re: NTSB announcement regarding flight 800

Date:         28 Dec 96 14:20:09 
From:         rjn@csn.net (Robert J. Niland)
Organization: SuperNet Inc. +1.303.296.8202 Denver Colorado
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Mark E. Ingram (markt@mickey.mo-net.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:  rjn@sni.net                              Fort Collins
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