That was considered. I think it's appendix 13 of the report. There are several reasons it was rejected. The most important is that the breakup sequence definitely began in the CWFT and proceeded from there (there are a number of ways to determine the sequence, metallurgy, sooting, etc. and they all agree).
OK, so why didn't a piece of space debris, say, penetrate the CWFT and set off the fuel-air explosion that overpressured the carry-through and broke the plane up? Because there's no hole. The structure was almost all recovered, and the bits that were not recovered, the inner and or outer skin between them and the great outdoors was recovered. (Actually the "missing" bits were probably among the fragmentary wreckage recovered, but couldn't be ID's with certainty and put into place. We are talking a max of a pound or so in sub-one-ounce fragments here and there). And none of those missing tank fragments can be gotten to in a straight line from outside the aircraft, except by going through skin and/or structure that evidences no hole.
SO... Imagine you have a helium balloon inside a shoebox that is taped shut. You come home from school and you open the box and the ballon is popped. You think your brother did it with his bb gun. But there is no hole in the box, and no hole in the balloon that resembles that made by a BB gun. Your brother didn't do it -- at least, not that way.
If you have followed me so far, you see that your space debris theory can't be responsible. ANd by the same reasoning, neither can missile fragmentation. (There are no signs of missile blast or fragmentation, or of a bomb, on the wreckage. Anywhere. And yes, these things leave definite signatures and NTSB metallurgists can spot them almost with their eyes closed). There was no question on Clipper 103. There isn't on TWA 800 either.
Here are a couple experiments that most TWA 800 refuseniks either don't know about, or don't understand:
Those tests were conducted by Cal Tech's Explosion Dynamics Laboratory (more members of the great conspiracy! Egads how will Jamie Gorelick rub them out now that they know too much? But I digress). Some of the conspiratroids latch onto the fact that these tests did not use Jet A, but they don't understand that the tests could not be conducted at 13,800 feet. The substitute fuel was selected because its properties at the test altitude in California duplicated the properties of Jet A at 13,800. It is very hard to get this across to someone who thinks that Boyle's Law is a cop show on TV....
d.o.l.
Criminal Number 18F
So the boloid came in one of the wndows.