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> Legally speaking, 0, since the Outer Space Treaty forbids placing nuclear weapons and other weapons of mass destruction in orbit, and all spacefaring nations so far have signed.

Signing treaties didn't stop us from waterboarding torture.

> Even if the military kept things under wraps, I'm not so sure that stationing nukes in orbit would provide a significant advantage, as you would only be able to strike a particular target when it rotates under your orbit, which means you can hit a target only twice a day at fairly specific times, while ICBMs can be launched at any time.

The big benefit would be that a target can be wiped off the map without a giant "LOOK WE DID IT" flag immediately beforehand.

> We already track more than half a million pieces of space debris, with 20,000 of those larger than a softball ([2]), so I'd imagine a "secret" satellite wouldn't stay secret for long.

Space debris follows a predictable track once spotted and isn't deliberately constructed to be hard to find with visual/radar observation. This is a bit like saying stealth bombers are impossible because we can easily spot airliners.

>Signing treaties didn't stop us from waterboarding torture.

Isn't that because the US called waterboarding "enhanced interrogation" instead of torture, and therefore could claim that they were following the letter of the law?

In any case, the "legally speaking" was intended to mean "it can still happen, but there's probably going to be a lot of fallout if someone finds out".

>The big benefit would be that a target can be wiped off the map without a giant "LOOK WE DID IT" flag immediately beforehand.

That's an interesting point. Only way I can think of to figure out whose nuke it is is to extrapolate the reentry vehicles' trajectory backwards and see what satellites are in possible source orbits. That's not going to be very accurate, I think. Wonder if there is a better defense against that.

>Space debris follows a predictable track once spotted and isn't deliberately constructed to be hard to find with visual/radar observation. This is a bit like saying stealth bombers are impossible because we can easily spot airliners.

Good point. I had considered the possibility of stealth tech, but I guess I didn't really think that hard about what it meant until I read that analogy.

Seems much easier to smuggle nukes into a country and just have them on standby in safe houses of the enemy country's large cities. The political fallout of getting caught doing that might be huge, but back in the Cold War I could see the CIA or KGB wanting to give it a try. Even if the US or the USSR (or smaller powers like France) was caught smuggling a nuke, it would likely be kept under wraps. The political system of a country would not want people fearing possible hidden foreign nukes where they live.

This scenario might make an interesting book or movie plot, but I have never heard of one. Spy novel with nukes.

The Peacemaker is a 1990's movie with this exact plot.

It's also the name of one of the most popular revolvers in American history. [1]

I don't know what it's called but I love when something is nicknamed for the antithesis of what it's meant to do: guns/nukes -- killing people. Peacemaker? You be the judge... [2]

[1] https://en.wikipedia.org/wiki/Colt_Single_Action_Army

[2] https://en.wikipedia.org/wiki/Mutual_assured_destruction

Si vis pacem, para bellum - If you want peace, prepare for war. Roman proverb.

So far nukes have kept the great nations out of war, but the possible Black Swan event of a large nuclear exchange is a doozy.

> Even if the military kept things under wraps, I'm not so sure that stationing nukes in orbit would provide a significant advantage, as you would only be able to strike a particular target when it rotates under your orbit, which means you can hit a target only twice a day at fairly specific times, while ICBMs can be launched at any time.

What you're describing is closer to a spy camera in a geosynchronous orbit. A LEO nuke would not behave like this.

>What you're describing is closer to a spy camera in a geosynchronous orbit.

I was thinking of a polar orbit when I wrote that comment. You'll always be over the same longitude with a geosynchronous orbit, as opposed to passing over any longitude. You have more flexibility in targeting locations that are mostly below you, though.

>A LEO nuke would not behave like this.

Why not? The orbit stays the same, while the Earth rotates under it. A particular point on the Earth will rotate under the orbit 0-2 times a day, depending on inclination.

I doubt you can even hit a target directly under you from a satellite in geosynchronous orbit, at least without a fairly significant amount of effort. You can't just fire a rocket "straight down" -- if you just point at the Earth and thrust, you end up in an elongated orbit that misses the earth entirely.

...and since you have to be moving faster to hit geosynchronous orbit, you have to have a lot more ΔV to get back to the earth than if you were in a lower orbit, which means more fuel, which means more weight, which means harder to get into that orbit to start with...

Oh, and since you're still moving when you're doing that ΔV maneuver, you'll end up in a lower (and not-geosynchronous) orbit before you get all the way to the planet, so the payload would probably end up doing a few orbits on its way down anyhow (at which point, why care if you're "over the target")

> I doubt you can even hit a target directly under you from a satellite in geosynchronous orbit, at least without a fairly significant amount of effort.

> You can't just fire a rocket "straight down" -- if you just point at the Earth and thrust, you end up in an elongated orbit that misses the earth entirely.

The second sentence doesn't justify the first. You can thrust in various directions even if your intended trajectory is straight down. I surmise you would simply need to reduce orbit speed to maintain the same angular velocity the whole way down, which doesn't strike me as a computationally or physically difficult problem.

> I doubt you can even hit a target directly under you from a satellite in geosynchronous orbit, at least without a fairly significant amount of effort. You can't just fire a rocket "straight down" -- if you just point at the Earth and thrust, you end up in an elongated orbit that misses the earth entirely.

Yeah, I know pointing straight down is a horribly inefficient way to deorbit; if anything, it probably requires more delta-v than you expended getting up there in the first place. I was more thinking that with something in geosynchronous orbit, small-ish changes in whatever velocity you end up in after the deorbiting burn could result in very different targets on the ground, whereas in LEO you can't cover the same amount of ground under your orbit with the same delta-v (or at least I think; haven't actually done the numbers, if I even knew how). Still requires a heck of a lot more fuel if you just want to get from LEO to the ground, as you pointed out.

> Oh, and since you're still moving when you're doing that ΔV maneuver, you'll end up in a lower (and not-geosynchronous) orbit before you get all the way to the planet, so the payload would probably end up doing a few orbits on its way down anyhow (at which point, why care if you're "over the target")

If the deorbit burn provides enough delta-v, you can fall straight from geosynchronous altitude to Earth without being stuck doing a few orbits. And the not-geosynchronous orbit is actually what I expected. You want the Earth to rotate, since that might move the point under the geosynchronous satellite approximately under the point the nuke would reenter the atmosphere. I don't know whether an orbit with the right period exists though.