Spike Jones [firstname.lastname@example.org] wrote:
>> I'm not sure, but don't you get EM shielding during atmospheric
>> reentry due to the plasma screen?
>yes. this is a major shortcoming of gps guided exoatmospheric
>devices. at typical reentry velocities you have only a very few
>(typically 3) seconds to reacquire gps and react.
Why would this be a problem? At least for the shuttle and other shallow reentry vehicles the shielding only occurs below it; the shuttle is now in continuous contact with the ground via the TDRS sattelites using the upper antennae. I guess that a much steeper re-entry might block out signals from above as well.
Of course the fundamental flaw of all GPS-guided weaponry is GPS-faking or GPS-jamming. Relying on external signals to tell you your position is always risky.