Heh. You kinda just need to go try it sometime, many of your beliefs are quite wrong.
Broadband RF noise is exceedingly easy to produce in signal levels high enough to jam just about anything. From afar.
All the stuff about environmentally produced noise is silly. A good rainstorm can wipe out GPS reception just as easily as NDB. VOR actually stands a slightly better chance of working in naturally produced RF noise. The power levels, distances, and band, as well as the modulation type, all picked for flying in clouds and storms.
GPS receivers today are awesome in the low levels of signal needed to be recoverable, but you're going to lose a couple of weaker birds when you penetrate precipitation. That's why there's so darn many satellites in the cluster.
And of course, if you consider the Sun natural, it can produce flares that can only harm GPS and rarely harm VOR or NDB reception. (Oceanic reception of NDB being an exception. A good flare can jack up the ionosphere enough that NDB long-range reception is wiped out.)
Thunderstorms also produce lighting which can affect all three, in brief bursts. Considering that lighting is just the world's largest known broadband spark-gap transmitter.
They're ALL a lot more fragile than you realize. But your bias toward space based Nav being stronger against various forms of interference, really doesn't hold water.
I ain't trying to be a know it all. I've just chased a lot of interference sources. One particular bad electrical transformer on top of a Downtown Denver building wiped out 121.5 as a useful frequency around here for weeks until a crew of eight of us went out one Friday night and hunted it down for fun.
Confusing as hell to find, since all the gear would point toward Downtown until you'd drive into the steel and glass canyons and watch it bounce all over the darn place, off those buildings. We hunted for hours. We were all sick of hearing it on monitor receivers. FCC didn't do it, FAA cared even less. A bunch of geeks with DF gear fixed the problem on a Friday night. It took until 1AM so we never got the usual Mexican dinner we usually treated ourselves to with friends when we did big noise hunts.
Find the IF frequency of any receiver on board an aircraft and I can build ya a guaranteed jammer that'd completely take it out, in a circuit barely bigger than a postage stamp. The battery would be bigger. The distance-squared rule for power levels, rules the day. Attacking the IF of a reciver if you're close to it, instead of multiplying up to the real receiver frequency makes the job even easier.
There's no magic bullet in GPS. It's RF based and susceptible to the same kinds noise sources as the others. Only the frequency is different. No big deal to multiply up and make noise up there as easily as down low or in the middle.
Just take all the static wicks off the airplane and fly through a nice heavy dry snowstorm. They'll all be affected. I guarantee it.
