Re: Pentagon to Shoot down Spy Sat

Rand Simberg wrote:
On Tue, 26 Feb 2008 12:56:59 +1100, in a place far, far away, Sylvia
Else <sylvia@xxxxxxxxxxxxxxxxxxx> made the phosphor on my monitor glow
in such a way as to indicate that:

Certainly the fragments will tend to have lower densities (in the sense you defined) then the original. But it doesn't appear to require a large change in energy (as a proportion of the total kinetic + potential) for the resulting orbit to be mostly outside any significant atmosphere.
Only for half an orbit.
It's an ellipse with one focus at the centre of the Earth. Where do you get half an orbit from?
From the fact that if its apogee is increased very much at all, the
vast likelihood is that its perigee has been decreased as well, which
means that it lies within the atmosphere, if not within the earth
itself. Thus it will enter half an orbit after apogee.
So most of the material that gains energy will re-enter at its next perigee, which is either almost immediately, or one orbit later, depending on the change in momentum vector. But that's only most.

In this case "most" = "all" to first approximation.
The closer the change in momentum vector is to being in same direction as the original velocity, the more orbits the material can survive before re-entering.

See above.

So I'll accept that most of the material won't become a long term threat, but some of it can.

"Some" = "to first order, none."

Just don't complain when you get hit by second order debris.

Sylvia.
.

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