I can't speak to the cost of interceptors but the fact that this discussion doesn't consider MIRVs or decoys doesn't seem very serious (the simple 10-to-1 ratio seems to be about orbital positioning) - ThreadSky

bretdevereaux.bsky.social • 13 days ago

I can't speak to the cost of interceptors but the fact that this discussion doesn't consider MIRVs or decoys doesn't seem very serious (the simple 10-to-1 ratio seems to be about orbital positioning)

Reposted from 🇵🇸Martin “Doomsday” Pfeiffer🏳️‍🌈

LOLOLOL this math

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trudeus.gg•13 days ago

Perun JUST made a video on this topic taking this bad math down lol https://youtu.be/CpFhNXecrb4?si=ccuGG0mFrkEJ7J40

thestarhart.bsky.social•13 days ago

Defense economics PowerPoint man, my beloved...

the-un-expert.bsky.social•13 days ago

Did everybody check out PerunAU's video on this last Sunday?

fritz1776.bsky.social•13 days ago

The mention of orbital positioning seems to indicate boost-phase interception, so that entirely bypasses the MIRV/decoy problem since those can only deploy during mid course at the latest. That said 10-1 is exceedingly generous if you want 100% coverage.

fritz1776.bsky.social•13 days ago

Ok I went back to check and this is insanely optimistic. Even a best case scenario where we have no launch delay (there’d be one) and the attack is a whopping 4 liquid fuels Korean rockets (so the boost phase is much longer than it could be) you need hundreds for full coverage.

fritz1776.bsky.social•13 days ago

The paper in question, if you’re intrested. I actually understated the ratio, 100% coverage for even that minimally capable attack would take a 1.6k interceptor constellation. 2.2k with 30 seconds of decision time. And it only gets worse as our missiles become more numerous and capable.

jmkorhonen.fi•13 days ago

While (working) boost phase intercept would indeed destroy all warheads at once, MIRVs are still bad news if the system isn’t 100% effective: any “leaker” would be much more destructive.

It may also be that the numbers in the above report are optimistic: boost phases are getting shorter.

jmkorhonen.fi•13 days ago

IIRC Brilliant Pebbles assumed 6 minute boost phase and required about 10:1 ratio of interceptors in orbit/interceptors at position to hit boosting ICBMs from a given country at any one time.

But boost phases are now ~3 min and could be much shorter:

https://bsky.app/profile/jmkorhonen.fi/post/3lqetfokmvs2z

jmkorhonen.fi•13 days ago

Then we have all the other tricks like depressed trajectories and hypersonic glide vehicles, like the Russian Avangard, which at the very least complicate space based intercepts.

fritz1776.bsky.social•13 days ago

Yeah the paper I linked talks about Hwasong-15 and 18, and assumes a 260 and 145 second boost phase respectively. We can assume Chinese or Russian missiles can go even lower than that, especially if designed around the existence of such interceptors.

fritz1776.bsky.social•13 days ago

Agreed, but if you are seeking perfect defense and not merely mitigation you are going in with the assumption that your interceptors get all the missiles. MIRVs and decoys thus change nothing unless you have discourse or terminal fallbacks which assume X% of leakers.

lollerisms.bsky.social•13 days ago

Brilliant Pebbles, which this is transparently based off of, had an estimated maintenance (your interceptors unavoidably burn up in atmosphere after a few years due to orbital decay) cost of ~$30B/yr in 1963 dollars, which is uhhhhh one fuckton in 2025 dollars.

fritz1776.bsky.social•13 days ago

Launch costs are way down since then, and projected to go lower, so it might actually be (becoming) feasible, but yes the price point is still immense. You’re looking at hundreds of billions just to check the DPRK threat. Russia or China are off the table entirely even with all of NATO buying in.

lollerisms.bsky.social•13 days ago

And Brilliant Pebbles *might* have worked had we been willing to throw more money than the Apollo program at it every year. Forever.

pauljunhyuk.bsky.social•13 days ago

Also, isn’t the canning of Brilliant Pebbles and everyone who worked there what gave us SpaceX? It’s the circle of life.

derekl1963.bsky.social•13 days ago

They make the classic mistake of ignoring the 90% of the costs that aren't the control systems. (As well as the classic of assuming that throwing computing power at a problem solves everything.)

valkyrie.hacker.gf•13 days ago

$25 per kg to LEO also sounds extremely fucking made up

kotonoaware.bsky.social•13 days ago

Give or take 6000%

suddenlyagoat.bsky.social•13 days ago

That was a the proposed cost from Starship (assuming it can lift payloads 12 times what the last launch failed to insert, & assuming they can fly each stage an average of 50 times)

which is to say, wishcasting

valkyrie.hacker.gf•13 days ago

s/kg/pound/

raedwald.bsky.social•13 days ago

The Fallacy of the Last Move.

loiathal.bsky.social•13 days ago

@armscontrolwonk.bsky.social had a good podcast about the math, economics, and problems with the setup: https://www.armscontrolwonk.com/archive/1220373/brilliant-swarms/

kezme.bsky.social•13 days ago

They may be envisaging boost-phase intercept.

michael-w-busch.bsky.social•13 days ago

@nuclearanthro.bsky.social

Even just considering orbits; one would need of order 1000 interceptors in low orbit to cover every point on the planet's surface at once - or to cover one point continuously.

None of this has changed since the 1980s.

nuclearanthro.bsky.social•13 days ago

I have a cat meme about this!

From before 2017.

#NuclearCatMemes

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