this post was submitted on 14 Nov 2023
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427
The space armament treaty says: no nuclear, biological or laser weapons in space. but kinetics... (sh.itjust.works)
submitted 11 months ago by [email protected] to c/[email protected]
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[–] [email protected] 57 points 11 months ago (15 children)

The rods from God's idea is insane and won't work.

We had this back when the Russians announced they were going to drop conventional ordinance from space, and everyone pointed out that they would be lucky to hit the right continent, let alone Ukraine. In order to make this actually work, you would have to have an active aiming system. Which you know, is a missile.

[–] [email protected] 19 points 11 months ago* (last edited 11 months ago) (7 children)

The launch platform can aim it and use math to account for gravity, the atmosphere and all that jazz to hit the target at least close enough. Just like we already do to safely crash/burn up space debris.

[–] [email protected] 20 points 11 months ago (1 children)

at least close enough

To whose standards exactly? Dick Cheney's?

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[–] [email protected] 12 points 11 months ago

No, they can't. The atmosphere is an unknown state, different temperatures, different densities, different wind directions, none of which can be known ahead of time. That's why weather forecasting is always approximate. You get a percentage chance that it'll rain. You don't get a definite time stamp with 100% accuracy.

We cannot predict atmospheric disturbances to the level necessary to make this a practical system. When they burn up space debris they do it "somewhere over the middle bit of the Atlantic" That's about the level of definition you get. It's not accurate at all.

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[–] [email protected] 43 points 11 months ago (14 children)

From a purely physical point of view, is that realistic?

If all of its energy is kinetic, it means that the energy must result from it's potential energy+any fuel it is propelled with. Ignoring air-friction and terminal velocity for free falling objects, that means that still the energy of a nuclear weapon is required to bring this thing up into space, or stored as fuel for its propulsion.

So unless the projectile is assembled in space, any rocket bringing it into space will contain at least the energy of a nuclear warhead. Gotta be a very nervous launch, knowing that any failure will result in a fire with the energy of a nuke.

[–] Brainsploosh 43 points 11 months ago (1 children)

A lot of the energy comes from orbital speeds.

The Hypervelocity Rod Bundles project proposed 6,1x0,3 m tungsten rods, weighing about 8200 kg, impacting at about 3000 m/s, meaning about 42 GJ of energy per projectile [wikipedia].

The weakest recorded nuke, the Davy Crocket Tactical Nuclear Weapon, is estimated at about twice that (84 GJ), and the largest, Tsar Bomba, at about 3 000 000x the yield (210 PJ).

[–] pennomi 35 points 11 months ago (2 children)

That’s their point, how do you get such a heavy thing to orbital speed without spending all that energy? You can’t unless you build it from materials harvested in space.

[–] Brainsploosh 29 points 11 months ago* (last edited 11 months ago) (6 children)

Oh, I apologise, I suffered some curse of knowledge there, the answer is time.

A blast is a release of energy over a short time, the whole point of building weapons is to store and handle energy in safe amounts over time.

Global electric energy consumption is about 200 PJ a day, approximately the same as the Tsar Bomba, but there's no risk for a huge explosion neither when you incinerate trash or turn off the AC.

Because time.

Although we could explode a nuke and propel things ballistically, it turns out it's a lot easier to use rockets. A rocket, although carrying frightening amounts of fuel and exploding spectacularly when it fires wrong, has several safeguards to not expend all that fuel at once. And also gives the opportunity to correct course along the way.

Now imagine that the same amount of energy has been expended many many many times over the course of the space era, and almost any mass in orbit has serious potential for damage.

For example, the MIR was 130 tons, orbiting at about 7,8 km/s, for a kinetic energy of 4 TJ, and another 235 GJ of potential energy. Totalling about a tenth of Little Boy that levelled Hiroshima.

Edit: Specifying and correcting the global energy consumption.

[–] pennomi 13 points 11 months ago (2 children)

Right, and tungsten rods are dangerous because they don’t slow down and burn up in the atmosphere like most spacecraft do (like you said, spreading out that energy over time and space). As long as you can deorbit them accurately, they are devastating since they convert the entire orbital potential energy into surface kinetic energy all at once. (Oddly, orbital potential energy and surface kinetic energy are the same thing, just from different points of reference.)

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[–] [email protected] 12 points 11 months ago (1 children)

One of the things that's stuck with me during my time on Lemmy is someone remarking that the only difference between a battery and a bomb is how controlled the release of energy is. Having seen what happens when you puncture a LiPo battery, I believe it 😰

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[–] [email protected] 8 points 11 months ago (2 children)

Wait this can't be right or I am missing something. Are you saying that the Tsar Bomba released 10 PetaJoule of energy more than our current world uses in a year?

[–] TAYRN 16 points 11 months ago* (last edited 11 months ago) (1 children)

It's.... definitely not right. Most estimates I found from a quick Google search put global energy consumption at a bit under 600,000 PJ per year, so even if they meant to say daily energy consumption or something they'd still be off by an order of magnitude.

The closest I can get to the number they gave is that global daily electricity consumption is a little over 200 PJ, so right on par with estimates for the Tsar Bomba.

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[–] [email protected] 13 points 11 months ago (2 children)

The mass to orbit isn't the hard part. A reusable Falcon 9 can put 18,400 kg in low Earth orbit. That should cover two rods, plus hardware to hold and deploy them.

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[–] Red_October 11 points 11 months ago

So a little bit of looking around, and some "Close enough, fuck it" math suggests that the Saturn V over the duration of it's launch emitted about the same amount of energy (190 Gigawatts over 2.5 minutes = 2.85x10e+13 joules, close to 7000 tons of TNT at 2.93E+13 joules) as 1/3 the yield of the Fat Man dropped on Nagasaki (FM = 20,000 tons of TNT = 8.36e+13 joules).

Now I'm not math inclined, so you should take all this with more salt than your doctor recommends, but if the rocket's output is comparable to 1/3 of an actual nuke, then it's not unreasonable to think that converting all of that back into kinetic energy would get you roughly 1/3 of a nuke's output, which could be said to be "the force of a nuclear weapon." It would take a launch of something Saturn V sized or bigger to put one up there, but supposedly Starship would be up to the task if it ever stops exploding itself and/or it's launch pad.

What I'm saying is, it's plausible enough for a blurb on some article.

[–] [email protected] 9 points 11 months ago (1 children)

And friction would cost some work both way

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[–] [email protected] 30 points 11 months ago (2 children)

What about the Jewish Space Lasers that MTG said started the wildfires?

[–] Wodge 29 points 11 months ago

Magic The Gathering has a lot to answer for.

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[–] rtxn 29 points 11 months ago (1 children)

If anyone wants some good sci-fi, I recommend The Expanse, both the books and the show. They make great use of kinetic impactors, especially Nemesis Games.

[–] nezbyte 12 points 11 months ago (5 children)

Doors and corners, kid.

Other recommended book series for scifi physics:

  • Expeditionary Force
  • Bobiverse
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[–] [email protected] 27 points 11 months ago (18 children)

The problem I remember is that it is expensive to get the rod up there in the first place.

Also every other nation would hate us and make jokes about the collective small penis of the US state.

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[–] [email protected] 22 points 11 months ago (2 children)

Except you can't just drop it. You need to push it out of orbit, and then push yourself back in

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[–] [email protected] 20 points 11 months ago (2 children)

Fun fact, everything with a high velocity (and a certain mass) has a lot of kinetic energy.

(Now think of space ships going light speed. You don't need photon torpedoes)

[–] [email protected] 15 points 11 months ago

Inyalowda love rocks, so let's give dem sum, sasa ke

[–] [email protected] 10 points 11 months ago (3 children)

True, but to hit things within the atmosphere it needs high mass and low drag. The ISS re-entering would have high mass but high drag, and most of it would fall apart when entering and be slowed down by drag so the energy gets spread through a long streak on the atmosphere instead of on the target

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[–] [email protected] 18 points 11 months ago (2 children)

We should just build space colonies and just drop those when needed

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[–] [email protected] 14 points 11 months ago

So no one considers moon a weapon of m.ass destruction? All it needs is a fairly good booster on the far side ...

[–] Mango 9 points 11 months ago (4 children)

Neil Tyson said this is entirely impractical.

[–] [email protected] 60 points 11 months ago

Neil Tyson needs to shut the fuck up and stop cockblocking me from having based weapons

[–] datelmd5sum 14 points 11 months ago (2 children)

I mean you have to put a nuclear amount of energy into the rods with chemical energy. Why not skip a step and just drop a big conventional explosive?

[–] [email protected] 16 points 11 months ago (2 children)

The idea is that it's too fast to ever intercept, is extremely penetrating, and you don't have to send a bomb to orbit in violation of treaty.

But all the really cool versions use rail guns and asteroid mining.

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[–] [email protected] 9 points 11 months ago (1 children)

Why in the hell would anyone bother though? First you got to launch all that mass into a stable orbit. Then you got to assemble the delivery system with the mass as it's most definitely too heavy for a single launch. Then you need fuel to deorbit the mass when you launch because things in stable orbits tend to want to stay there. Then you wait for the mass to deorbit because we couldn't afford to send enough fuel for a rapid deorbit. Also wait to launch till optimal trajectory for your target is achieved and hope that it's not too far side to side from your orbital path because that means even more fuel to deorbit. Also anyone with a halfway decent telescope sees your weapon just sitting there in orbit not to mention being assembled so now it's got a massive target painted on it at all times and is an easy casualty of first strike.

Or we could use the icbm's that are a proven tech, easier to hide though that's not foolproof, can be made mobile, much much more numerous, easier to protect from attack, much cheaper than launching tons of solid metal into orbit, and can strike anywhere on the globe within an hour.

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[–] [email protected] 8 points 11 months ago (2 children)

Once we have mastered space travel, the most dangerous weapon that will be available to almost anyone will be firing an asteroid at a planet.

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