In article ,
says...

In article ,
says...

From J. Clarke:
snip

Just a reminder, GPS was originally not for targeting, it was for
positioning the launcher accurately. With three hundred 400KT warheads
close counts.


I'd be interested to know where you got that idea from. If all that
was needed was precise coordinates for launching mobile systems, you
could simply hire teams of surveyors, at little more than minimum
wage, to paint a bunch of 'X's on the ground at potential launch
sites. This is a *far cheaper* solution than a multi-billion dollar
satellite constellation, especially if you wait til the Glidden paint
buckets go on sale.

Good luck painting Xs in the middle of the ocean.

The reason why GPS was developed and implemented was very
straightforward:
Inertial Nav Systems (INS) are inherently prone to errors that can run away in a huge way. ALL THREE legs of the nuke triad depended on INS - the bombers, sub-launched and land-based missiles.

Sorry, but neither ICBMs nor manned bombers DEPEND on INS. Manned
bombers have it and use it as one of their aids to navigation, but they
don't require it to deliver the payload to the target. That's done by
radar or by visual means.

ICBMs are just that, BALLISTIC. There is no terminal guidance. Once
the engine shuts off it is going to go where it is going to go. You
seem to be conflating nuclear armed ICBMs with conventional cruise
missiles.

ICBMs absolutely do have guidance systems. If they did not, they would
never be accurate enough to deliver their payload to the target. In
fact, it was the push to miniaturize missile guidance systems that used
up quite a bit of the early supply of integrated circuits. The Apollo
CM and LEM computers were an interesting "side project" using the same
integrated circuits. I'll even supply a cite:

Special ICs produced for Minuteman missile
http://www.ti.com/corp/docs/company/...se/1960/docs/6
2-special_ics.htm

If you don't believe Texas Instruments, who made the "chips", how about
the USAF:

http://www.afhso.af.mil/shared/media...100924-024.pdf

Also, if you visit either the United States Air Force Museum in Dayton,
Ohio or the Smithsonian Air and Space Museum you can see some early
versions of the above.

Thor Guidance System
http://www.nationalmuseum.af.mil/fac...t.asp?id=13567

Titan II Info
http://www.nationalmuseum.af.mil/fac...eet.asp?id=539

Minuteman III Guidance System
http://airandspace.si.edu/collections/artifact.cfm?
object=nasm_A19770995000

Where GPS was needed was to provide an accurate launch position for the
submarine force.

This is also true, but GPS also helped with bombers, cruise missiles,
reconnaissance aircraft, ground vehicles, and even (eventually, due to
miniaturization) individual troop movements. If you want to know
position and velocity for any reason, GPS is the tool which solves that
problem.

INS's measure acceleration, so you have to go through two
integrations
to get position, and that's only after you've initialized it to an
accurate position by some other means - taken a fix. After feeding
the INS an accurate fix, errors can still go wildly out to lunch.

So what?

GPS can be used prior to terminal guidance of a missile. ICBMs can use
it during their coasting phase and errors can be corrected.

Inertial Navigation for Guided Missile Systems
http://www.jhuapl.edu/techdigest/TD/td2804/Bezick.pdf

So even if GPS was conceived as a solution to the problem of determining
the position of a submarine prior to missile launch, its use has
expanded greatly in the decades which have followed.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer