Re: GPS BASICS: WAS:Re: BASICS: Property Rights

Spike Jones (
Mon, 14 Dec 1998 22:19:26 -0800

> spike wrote:
> > ...typical weapon-use reentry bodies would come in 20-40 degrees from
> > vertical and the velocity would go from around 8-10 km/sec down to
> > 3-4 km per second, experiencing 60-80 g during that phase. these are
> > not extremes, these are typical numbers. spike

> Michael Lorrey wrote:
> At what altitude is the 20 second phase at? If its at 200,000-400,000 feet, then This tells
> me that the warhead has around a minute after reentry to get its bearings and make final
> course corrections before impact. The fact that the reentry phase is shorter than I thought
> actually makes GPS guidance easier.

um, not really. its unclear exactly where the gps signals can be reacquired, but the theory suggests it is in the last 3 to 5 seconds of flight, depending on the trajectory. i may be able to dig up the equations for it if you are that interested. the notion was to make a reentry body that would do the dirty work not with explosives but by sheer kinetic energy. a body travelling at around 1100 meters per second would release the energy of an equivalent mass of exploding tnt. such a system might be great for taking out a communications tower or a radar dish, but it is your classic american weapon, as it would cost a looooot of money. spike