Salvage Fuzing and Orbital Nuclear Weapons

A short Nukesletter this fair Friday evening. I’m on my way back to D.C. from Philadelphia after participating in a very interesting table-top exercise set around a scenario incorporating the alleged Russian space-based co-orbital nuclear capability that we first learned of in 2024 from the Biden administration following congressional leaks. The exercise was put together by the good folks at the Foreign Policy Research Institute and I’ll avoid scooping their own write-up of the game (which will come in due course). The game was also held under the Chatham House rule, so I won’t say anything else here about who else participated.¹ Personally, I was quite pleased to see this exercise; I’ve been very interested in gaming out various crisis scenarios involving possible deployment, signaling, and employment modalities of such a weapon. I really think, in particular, that commercial space firms leveraging low Earth orbit need to take the growing risk of nuclear use seriously.

Frame from a 70mm film of the Starfish Prime Nuclear test.

What I want to comment on here is a very narrow, technical point that I came to learn wasn’t widely understood or appreciated by many space and nuclear folks present at the game, which is the notion of salvage fuzing applications in a space-based co-orbital nuclear weapon system.

First, some definitions. “Fuzing” (or a fuze/fuse) refers to the subsystem on any explosive device, including a nuclear weapon, that defines the conditions under which it detonates. There are many types of nuclear weapons fuzes and I won’t go over all of them here. Some representative fuzing mechanisms involve altitude, atmospheric pressure, impact, time, or proximity to a defined target. A fuze works by initiating a firing signal at the precisely right time to kickstart intended effects (including the series of physical phenomena necessary within a physics package to cause a nuclear detonation).

A “salvage” fuze, as its name implies, is implemented to ensure maximize the probability that weapons system exhibits its effects as designed under—let’s say—sub-optimal conditions. These conditions normally include the premature disablement or destruction of a weapon en route to its target. The most traditional context in which one would come across salvage fuzing is in the context of discussions around terminal missile defense. To defeat such systems, one can implement salvage fuzing such that a reentry vehicle (RV) with said fuze can probably successfully detonate if an adversary intercepts the RV in the terminal stages of flight (or, back in the day, if an adversary’s nuke-tipped interceptor nuked your incoming nuke²). In such a scenario, the height-of-burst is likely still sub-optimal for whatever targeting effect was desired, but you still “salvage” a nuclear detonation out of the RV over your adversary’s territory. This is a pretty serious problem for terminal missile defense!

In the context of today’s war game, there was some discussion on my team (Russia) about whether the United States would attempt to use some terrestrial anti-missile capability as a latent direct-ascent anti-satellite weapon and kinetically destroy nuclear-capable anti-satellite weapons in low Earth orbit. I believe it is extremely plausible that Russia would reasonably implement salvage fuzing on such a weapon (so much so that I would argue it is irresponsible to proceed as if Russia has not implemented salvage fuzing). As a consequence, the United States would have to consider that kinetic attacks in space intended to destroy a co-orbital nuclear ASAT could cause a detonation, with all of the ensuing undesirable, indiscriminate effects in space that follow.

Salvage fuzing doesn’t necessarily need to have some of the obvious downsides that you might think of. For instance, a boost-phase RUD over your own national territory won’t activate such a fuze because salvage fuzes can be set to only activate after a certain set of in-flight conditions have been met (such as acceleration, in the case of terminal-phase ICBM RVs, or flight-stage separation, or a combination thereof).

There are some arguments against my suggestion that Russia has, with a very high probability, implemented salvage fuzing in its design for such a weapon. The biggest one, I think, is the possibility of simple orbital collisions causing an undesired nuclear detonation. Things in space sometimes collide—a problem that is growing worse! There’s a trade-off here: is a greater risk of on-orbit collision causing an undesired nuclear detonation worth running to deter undesired deliberate American counter-action against such a weapon in a scenario where it has been deployed? I don’t know. There is presumably some flexibility in activating a salvage fuze, including post-launch, but once activated, it is probably not feasible to remotely disable such a fuze. The easiest way to deal with such a problem is just to not loft such a weapon arbitrarily in peacetime, which I think is unlikely to be the favored Russian concept of operation for this system anyway.³

It is my view that it would be extremely unlikely for any country contemplating the deployment of a space-based co-orbital nuclear warhead to not implement salvage fuzing as a means of deterring on-orbit kinetic attacks on such a weapon. Given how much still remains classified about the exact nature of salvage fuzing for contemporary nuclear weapons, there’s ambiguity around this, but I figure it’s worth reasoning about this in the context of our current era of space nukes.

That’s all for today. I head back to Korea next week; looking forward to running into readers there!

Extras

I had a fun chat with Frontlines & Backrooms earlier in the week about the new nuclear age, some of my work on nuclear strategy, proliferation, North Korea, damage limitation, and more. You can listen below!

Ankit Panda | Managed Armageddon (Frontlines & Backrooms)