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Are they? Without GPS? How I wonder? Because the US will disable GPS for everyone but their own forces in a heartbeat in the event of war. And China / Russia

Are they? Without GPS? How I wonder? Because the US will disable GPS for everyone but their own forces in a heartbeat in the event of war. And China / Russia might be able to knock out US GPS pretty quickly - but all of that is very untested, moreover, the US may have a way to put up a bunch more satellites quickly. Systems today have become really, really dependant on technologies that may not be available in a time of war. It may very well could be that if the US has their act together they could shut down an advanced opponent pretty quickly without having to do much at all. I'm actually pretty curious as to how advanced guidance systems would work in 2018 without GPS like technologies, not just in 'known tech' but behind the scenes, all the secret stuff. It's hard because in some ways we could expect them to be way, way ahead with some things, but in others, they might be blindingly incompetent, for example, maybe the US really doesn't have a plan for rapidly popping up new GPS satellites in the event the Chinese knock some down.

mikeash 8y ago
Inertial guidance can be quite accurate when you only have 30 minutes to build up errors. Land-based missiles know exactly where they're starting from. Submarine-based missiles not so much, but they are given targets which don't need as much accuracy.
dotancohen 8y ago
> the US may have a way to put up a bunch more satellites quickly. That would require a stockpile of both satellites and launchers. I've never heard of a stockpile of GPS satellites, and they take years to build. But even assuming that there are a few at the ready, what will launch them? I'm hard-pressed to think of many orbital solid rockets, and those that do come to mind (such as Shavit) are way too harsh to launch an atomic clock, not to mention not having the payload capacity to MEO. The liquids are gentler, but are far from launch-ready and much more constrained for launch locations and orbital inclinations.

mikeash 8y ago

Inertial guidance can be quite accurate when you only have 30 minutes to build up errors. Land-based missiles know exactly where they're starting from. Submarine-based missiles not so much, but they are given targets which don't need as much accuracy.

dotancohen 8y ago

> the US may have a way to put up a bunch more satellites quickly. That would require a stockpile of both satellites and launchers. I've never heard of a stockpile of GPS satellites, and they take years to build. But even assuming that there are a few at the ready, what will launch them? I'm hard-pressed to think of many orbital solid rockets, and those that do come to mind (such as Shavit) are way too harsh to launch an atomic clock, not to mention not having the payload capacity to MEO. The liquids are gentler, but are far from launch-ready and much more constrained for launch locations and orbital inclinations.