[xoa]

A few small corrections:

>Also, it's impossible to hide a satellite in space. Every nation with a space program tracks every orbiting object that's even remotely big enough to be a functional artificial satellite. There are no "stealth" satellites, mostly because you can't hide a launch...

This isn't entirely true. First, satellites absolutely and do maneuver after launch, so they are not limited purely by the orbit they launch into. That is of course limited by how much propellant they carry onboard, but it is done (and for spy sats particularly). Second and more generally, for any object in space it's impossible to have persistent [0] omnidirectional stealth across all bands (due to thermodynamics). However, it's very much possible to have single band stealth (a shape that is radar stealth for example) as well as unidirectional multiband stealth, and because space is so big often that may be enough for a given scenario. For spy satellites in HEO they may as well be presenting a single side all the time to any Earth-based observers, and while some nations could react to that by launching tracking sats even farther the vast majority of actors (anyone on the level of ground-based amateur astronomers for sure) lack that capability. Transmission out can use the same idea, in space P2P laser links are generally invisible out of path, so a stealth sat could stealthily have comms to a non-stealth relay even further out.

As a practical matter right now it seems extremely doubtful any serious such systems are in place due to the huge hit on mission-effective mass which gets worse at distance, though it wouldn't be surprising if there have been some experiments at least. But with launch systems like Starship and enormously more mass to throw at problems, we may well see a certain number of much more serious stealth spy platforms eventually.

----

0: In principle one could achieve perfect EM stealth temporarily by carrying onboard empty volume, a heat and a cold source (like a whole lot of liquid helium/nitrogen) then running as a closed system performing thermodynamic work averaging those out. Could run for some fixed period of time until the useful differential was exhausted and only be observable by interaction with mass in space or gravity. But who knows if that'll ever actually get utilized, since the unidirectional concept can be extended by an advanced space faring organization too. One can keep going farther and farther away from a target and compensate with a larger aperture with enough space capacity. If we imagine some aliens or something with an Earth observing stealth platform out in the Oort cloud say, it could be a kilometer across and very hot on the extrasolar facing side yet still damn near impossible for us to notice. Or of course someone could hide in the thermal noise of other sources. Interesting to speculate about from a hard scifi perspective anyway.

[SkittyDog]

> This isn't entirely true.

Yes, my original statement is entirely true. You're offering a poorly sketched basket of theoretical ideas, none of which change the reality that no nation has EVER attempted to add low-observability features to it's military satellites... Mostly because none of the ideas you sketched would actually work, in practice, to effectively hide a functional satellite.

Talking about manuvering propellant is completely beside the point... The US, Russia, and China are all perfectly capable of tracking manuverable spacecraft and satellites, and we all do so 24/7/365.

Think about this, for a minute... Ever since the deployment of nuclear-capable ICBMs (~1961), space has been THE primary delivery avenue for the single biggest existential threat (thermonuclear war) to the most paranoid and technologically advanced nations on earth. Space is where you get nuked from! We have all invested MASSIVE resources into making sure we can detect and track literally anything in space, because it is the single most important battlefield in human history.

If effective low-observability spacecraft were a real thing, don't you think that at some point in the last 60 years, one of these nations would have deployed such a weapon... or addressed the concept in an arms control treaty... Or even discussed it publicly?

If you find some credible examples of anybody discussing low-observability ICBMs, I'd gladly walk this back. But I'm pretty confident that you're not going to be able to.

[LargoLasskhyfv]

Uhm... [1] https://nsarchive2.gwu.edu/NSAEBB/NSAEBB143/index.htm ?

Also [2] https://en.wikipedia.org/wiki/Misty_(satellite)

[xoa]

>Yes, my original statement is entirely true. You're offering a poorly sketched basket of theoretical ideas

No, it is not. I'm not offering theory, I'm offering physics.

>none of which change the reality that no nation has EVER attempted to add low-observability features to it's military satellites

That you've never heard reports of projects like "Misty" (by the US NRO) is nice, but doesn't inspire much confidence in your statements either.

>Mostly because none of the ideas you sketched would actually work, in practice, to effectively hide a functional satellite.

Of course they would. This isn't, well, rocket science. We know how to make radar stealth shapes. Same math would work in space, in fact even more easily since there is no need to worry about aerodynamics nor necessarily stealth except in one direction. Lowering optical observability isn't even just a military thing, SpaceX themselves are literally doing it with Starlink, the subject of this subthread! They've been doing that to reduce albedo so as to cause less disruption for Earth-based astronomy. As I said, I certainly don't know if any major efforts have been made at serious thermal stealth, but not because it's some complex idea but merely due to tradeoffs in mass. Starship will allow launching 100-150 tons to LEO though with much larger fairings (last reported diameter I saw was 9m). As with all sorts of other things that will offer, the military will certainly be able to contemplate spending mass and volume on things that wouldn't have been worth the tradeoff before.

>The US, Russia, and China are all perfectly capable of tracking manuverable spacecraft and satellites, and we all do so 24/7/365.

Sure, the same way they can track maneuverable aircraft... so long as they aren't stealthed.

>Ever since the deployment of nuclear-capable ICBMs (~1961),space has been THE primary delivery avenue for the single biggest existential threat (thermonuclear war) to the most paranoid and technologically advanced nations on earth. Space is where you get nuked from!

You've gone entirely off topic and also seem pretty confused here. It's right there in the name: ICBM, the "B" is "ballistic", not "orbital". Orbital nukes are in fact specifically banned by treaty as too disruptive. ICBMs and SLBMs follow a ballistic trajectory. They're not space-based. There has been significant support for not making orbit a battlefield, due to rightful concerns about things like Kessler syndrome. Part of MAD and monitoring that has indeed been rocket launch monitoring satellites as well as ground based stations, but none of that has anything to do with spy sats. Monitoring sats have zero need to be stealthy, just to cover the whole planet at once. If either ICBMs are detected being launched or suddenly all your monitoring satellites get taken out, well conclusions can be drawn. In fact part of the core part of MAD is specifically to forego things which could be destabilizing by increasing odds a first strike could work.

>If effective low-observability spacecraft were a real thing, don't you think that at some point in the last 60 years, one of these nations would have deployed such a weapon... or addressed the concept in an arms control treaty... Or even discussed it publicly?

Um, nope? Not at all? As I said, while there have been experiments I don't think they are that much of a thing yet because there wasn't much need nor the mass budget for it. Up until modern times not that many countries/organizations could in fact track all the spy sats, and anyway the far more important interest was simply having lots and lots of them. Why put budget into fewer stealthy ones vs more and more better ones? But as the barriers to observation and tracking have fallen, and as mass/vol budgets go up, the time may indeed come when stealth will get renewed focus beyond existing experiments.

Again, when theorizing about future things that haven't necessarily been done yet, necessarily it's important to consider the physics of it. The physics here though are pretty straight forward frankly.

>If you find some credible examples of anybody discussing low-observability ICBMs

I remain completely mystified how you jumped from "a satellite in space" to "ICBM" if you have the slightest clue about what any of this stuff is. ICBMs aren't satellites, cannot be stealthed, and have zero need to be stealthed either. The only thing they need is decoys and that indeed has been done and is part of the reason (along with destabilization) serious strategic missile defense (against a peer opponent, not merely a rogue state handful) is considered infeasible. Stealth satellites would be about intelligence or perhaps fallback CnC or comms.