The most powerful weapons on earth already are immune to jamming. ICBMs use celestial navigation (pictures of the stars) to course-correct, which is a form of navigation you cannot jam.
Our ICBMs have no update mechanism at all. Once they're out of the silo, they're completely on their own.
Or am I over-interpreting the name?
Contrast hypervelocity weapons, which -- contrary to the name -- don't really go faster but they can maneuver in the atmosphere at that speed.
In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation, the variation being the difference between where the missile is, and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GEA. However, the missile must also know where it was.
The missile guidance computer scenario works as follows. Because a variation has modified some of the information the missile has obtained, it is not sure just where it is. However, it is sure where it isn't, within reason, and it knows where it was. It now subtracts where it should be from where it wasn't, or vice-versa, and by differentiating this from the algebraic sum of where it shouldn't be, and where it was, it is able to obtain the deviation and its variation, which is called error.
https://web.archive.org/web/20050514035446/http://www.afmiss...
All fission weapons are not necessarily also fusion weapons. But probably most are nowadays.
Most of the cost in a nuclear weapon is in the primary. It only makes sense to build pure fission weapons when you want very low-powered nukes for close range tactical use; the DoD has determined that don't see enough use for them to justify the upkeep of specific weapons.
And I would doubt image recognition for ground features would make it that accurate, too. Before reentry, you’re very high and fast and reentry isn’t that predictable to get you accurate enough to hit a house. And during reentry, you’re not going to see anything though plasma. And after reentry, you probably don’t have enough time and control authority to still guide into a specific house.
ICBM guidance is very different from cruise missiles.
Hypersonic glide ICBMs have been successfully tested by China, and are under development in the US, so it's entirely possible to maneuver, and optionally guide them in the terminal, though perhaps not advisable on a jammable channel, except perhaps as an anti-radiation weapon.
https://thebulletin.org/2017/03/how-us-nuclear-force-moderni...
So you could say the use would be increased certainty your enemies command and control and other bunkers would be destroyed increasing the odds of “winning” whatever happens afterwards.
…you know, for defense
At this point though, couldn’t you just blow up your own country and thus accelerate warming so much as to doom the rest of humanity in a dozen years? I might have read the wrong article on that though so don’t quote me.
Nine Billion Names of God