[empedocles]

I always enjoy hearing Tory Bruno talk tech.

The key missing information here seems to be how many of these satellites would be required to have constant coverage of likely trajectories. This depends on the distance at which the laser remains effective. There would be no atmospheric scattering, but beam collimation is never perfect. It also depends on how fast the satellite can fire a new shot, as any warhead will be surrounded by decoys and other penetration aids. If this requires a large number of satellites, I am very sceptical. While Starlink has shown the possibility of creating large constellations, these sats would surely be much larger and more expensive. Really, Starlink makes me think something like BRILLIANT PEBBLES (https://en.wikipedia.org/wiki/Brilliant_Pebbles) would be a more reasonable alternative.

Also, could an adversary surround the warhead with absorbent chaff as a countermeasure? Or simply an ablative shield, the warhead needs one anyway to get through the atmosphere.

Still, a very interesting read from a very interesting CEO.

[MilStdJunkie]

Yeah, me too. Bruno, although ex-LM and ULA, is one of those "born-dirt-poor-but-obsessed-with-rockets" kind of CEOs that seem to be hard to find these days. That's one of the great differentiators between now and the days of the S1C; you'd have a hard time finding finance executives doing technical steering in 1967. Which, I mean, fair point, as far as I'm concerned, but I might be a wee bit biased.

From a layman's perspective, it seems like maybe DEWs should be looking at disrupting the extraordinarily delicate aerodynamics/hydrodynamics/plasmadynamics(?) of maneuvering Mach 5+ targets in atmosphere. Why do I say that? Well, if these things get consistent asymmetry in any part of their forward shock they'll spin themselves into bits, that's one. You can't shield the air with ablatives, that's second. Also, third, the sheath might be part of the communication/guidance system, so disrupting that it is good. Finally - somewhat related to second - tuning DEWs to interact with a plasma has TONS of possibilities, which helps to mitigate DEW's many many weaknesses over longer ranges. For the most part, I think DEWs will be short range wunderwaffen - particularly on the defensive end - but there's going to be niche cases.

[dsr_]

Referenced: cost of firing a laser is $1 of gasoline run through a generator. That's roughly a liter.

Let's say raw energy content is 32MJ/L, and we have gasoline=>electricity losses of 50% and laser efficiency of 30%, so we expect a little more than 5MJ per shot.

If you can hit a 2m target moving at 5Km/s through 1000Km of space and atmosphere with 5MJ, how much energy can you put on a 1m target moving at 7m/s at a range of 500Km?

The difficulty in killing people from space will be targeting, and the limited availability of fuel and oxidator in space.

[AstralStorm]

Even more so, limited availability of cooling. Overheated laser melts rather than firing, so it will likely need active cooling droplet heatsink for fast refire in case it does miss or enemy fires more than one missile, and that's a limited resource.

[pdonis]

So basically the system from the movie Real Genius?

[ShadowBanThis01]

Exactly what I think of, every time.

Now off to make some popcorn...

[arijun]

> limited availability of fuel and oxidator in space

And don’t forget—-you have to fly up Tory Bruno each time to fire it.

But as a platform for assassination, it doesn’t seem so far fetched. The two main things I can think of that would make it difficult would be the much higher attenuation and scattering from the atmosphere, and the need for a different (telescope based?) target acquisition method.

[jjtheblunt]

would the atmosphere along the beam path vaporize in short order at those power levels, so scattering/attenuation is temporary for a fixed beam?

[nine_k]

If it does so, the resulting plasma will very actively absorb the laser pulse's energy.

Your best bet is not interacting with the atmosphere in any way, and merely adjusting for refraction.

[akiselev]

Maybe, maybe not; self focusing [1] is an active area of research. Optics is one area where secret projects have been shown to be way ahead of what is publicly available [2] so I wouldn't be surprised if they've figured out some scifi way of making orbital lasers more effective.

[1] https://en.wikipedia.org/wiki/Self-focusing

[2] https://en.wikipedia.org/wiki/2012_National_Reconnaissance_O...

[ikekkdcjkfke]

What about a huge sun lens in space to concentrate the sun rays

[brucethemoose2]

Brilliant Pebbles seems way more practical today than 1987. Lots of exotic 80s autonomous systems are now commercial and mundane, and launch costs are plummeting.

Sending up a space laser seems particilarly absurd when one could send up 100(?) drone interceptors for the same cost with less R&D, especially when a drone constellation is far more resilient against anti satellite weapons.

[empedocles]

I agree, though the cost of an exoatmospheric kill vehicle https://en.wikipedia.org/wiki/Exoatmospheric_Kill_Vehicle is probably high.

And one way to avoid this is the other part of the hypersonic renaissance, which is the ability to dip down into the atmosphere.

[ShadowBanThis01]

Not to mention that this simply moves the initial conflict to space, where adversaries can deploy DE satellites to destroy ours... and THEN launch missiles.

It's incredible that 40 years after Reagan and the "Star Wars" defense plan, we finally have entities doing what seemed obvious even to high-schoolers at the time: just make the missiles zig-zag.

[ryan_j_naughton]

what seems obvious is still very difficult. Zig-zagging at hypersonic speeds creates insane G forces on the projectile.

[ShadowBanThis01]

But you only have to nudge it a little to make the "bullet hitting a bullet" untenable, especially if you do it after countermeasures are launched.

[LorenPechtel]

Zig-zagging burns energy. Staying in the atmosphere burns energy. Even without burning up energy on maneuvering missiles are mostly fuel--and the tyranny of the rocket equation applies. (Note that this is not a problem for terminal maneuvering--the missile can trade it's velocity for maneuvering at that point while only incurring the penalty of bringing along the control surfaces.)

[dabluecaboose]

> There would be no atmospheric scattering

Kind of by definition if something is -sonic then it's in the atmosphere. There would be less scattering but there would definitely be some on the target end.

[arijun]

The article said ICBMs were hypersonic, and those certainly spend a lot of time outside of the atmosphere.

The gliders seem to spend the entirety of their trip in the upper atmosphere, though.

[dabluecaboose]

Reentry does kind of by definition enter the hypersonic regime, but it's somewhat unintuitive to the layperson since Mach 5 is much slower at those very low pressures, and it's an entirely different beast than flying at Mach 5 in-atmosphere proper

[askvictor]

> could an adversary surround the warhead with absorbent chaff as a countermeasure

That would require a constant stream of chaff (it would get left behind pretty quickly without any thrust), and would need to be shot out in the opposite direction of travel (lowering the missile speed the entire time), and require the chaff and its launch mechanism to be part of the payload (increasing weight).

[nitwit005]

Wealthy nations will probably keep pace with defenses. Poor nations will probably just bypass them.

The easiest way for North Korea to nuke Tokyo is to just put the bomb on a legitimate seeming boat, and sail it over.

[TMWNN]

No! This is as much a conceptual mistake as "interceptor costs 10X as much as the missile it is designed to destroy, so antimissile defense is foolhardy" without taking into account the value of what the missile can destroy.

Maybe the boat will get through; maybe it won't. The ship might be intercepted before it reaches the target. Or security personnel with geiger counters can find it on the dock. And so on. From North Korea's perspective (or the USSR's during the Cold War, or Russia or China now), the uncertainty of the success of such an attack makes it very, very risky to actually deploy, except maybe in a situation where you're already losing the war (and in that scenario, the odds of a successful detection by the target are obviously that much higher).

A ballistic missile, by contrast, cannot be stopped except with great, great difficulty. That's why North Korea has built missiles for its nukes, and not a fleet of cargo ships and fishing boats.

[nitwit005]

Ships are not currently inspected at sea, and it's impractical to do so. The cargo is in giant stacks, and you need a dock to unload it for inspection.

Finding it at the dock is completely useless. You can set the nuke off while still at sea and still destroy half a city.

There is no mechanism for interception of such an attack at the moment.

You need a neutron detector, rather than a Geiger counter, for nuclear material detection by the way.

[slashdev]

That, plus cargo ships and fishing boats aren't pointy enough. They'll put a smile on the faces of the enemy.

[PJDK]

That might work as a first strike capability - although sailing a cargo ship from North Korea to Tokyo without garnering any interest from intelligence agencies might be more difficult than you give it credit for.

But the main thing you want nuke for is as a deterrent. Get in a fight with us and we press the button. It's hard to imagine the sneaky boat trick working when North Korea is under blockade by the entire US and Japanese navies. And even if they run the blockade they're going to have trouble getting close to Tokyo.

[nitwit005]

Past history suggests they'll get away with it extremely easily: https://en.wikipedia.org/wiki/North_Korean_abductions_of_Jap...

[aww_dang]

Maybe they use typical smuggling routes and have the whole thing buried, in a storage unit, long term parking or rented apartment?

[PeterisP]

An interesting "cheap, dirty & dangerous" mode of attack is loitering munitions from commodity FPV drones. Their capabilities have been demonstrated in current Russian invasion of Ukraine, and if any infiltrator can get in a few miles of the target, a "suicide drone" with a few pounds of explosives and shrapnel can be very difficult to defend against.

[elurg]

The US currently has a large advantage is mass-to-orbit capabilities that is set to explode once Starship comes online.

Elon needs to talk less about peace with Russia and more about deploying weapon systems. He can make enough money from it to retire on Mars.

[belter]

"Chinese scientists call for plan to destroy Elon Musk's Starlink satellites" - https://www.livescience.com/china-plans-ways-destroy-starlin...

[panick21_]

Yeah but they can't do it now and not for quite a while. And even then, what is the replacement speed. And how does it compare to how fast the US can take out China space based internet.

[cjbgkagh]

I always assumed he would end up deploying a weapons system to space. Of course he would have to pretend to be doing something else while he builds up the capability to prevent others from becoming nervous. Something silly like colonizing Mars would work, especially if he really leans in to the eccentric billionaire trope.

[MichaelZuo]

It would be impossible because even large amateur telescopes can photograph launch payload to a decent level of detail.

If the appearance doesn't match a plausible civilian satellite mission then everyone will know within hours.

[cjbgkagh]

The building of the infrastructure needs a red herring, the actual deployment need not be secret because by then it’s a done deed. Once deployed you’d want people to know, to avoid a Dr Strangelove situation. A veritable sword of Damocles.

[MichaelZuo]

I don't see how? An anti-satellite missile can be sent up to destroy the target within a few minutes of a decision.

[PeterisP]

If the launch capabilities are unbalanced (as they are!) then no, anti-satellite missiles aren't an option - at the moment noone can afford to launch an anti-satellite missile for every satellite that SpaceX can sustainably launch. Like, it was no problem to launch 1500+ satellites in 2022, but at the moment I don't see a credible capability for China or Russia to launch 1500+ anti-satellite missiles per year.

[cjbgkagh]

That kind of brinkmanship would still be attractive to a waning hegemon. I was thinking more like 250 tones worth of mini nukes which would be pretty hard to shoot down.

[jdougan]

You'd think that....but then there is Deadhand/Perimeter...

[ta988]

Oh yeah? do we have pictures of all the private and defense satellites that were launched?

[IntrepidWorm]

Certainly not, but one wouldn't need to catch every satellite launch for space weapon- one or two would be enough evidence to go public and warrant further scrutiny. There are a number of extremely savvy amateur astronomers across the world that track suspected military launches and publish their findings: https://sattrackcam.blogspot.com

[ta988]

That's a fun website thanks

[robotnikman]

iirc there are international treaties to prevent this. If those treaties get broken you will unleash some nasty weapons, like 'Rods from God'

https://en.wikipedia.org/wiki/Kinetic_bombardment