The space armament treaty says: no nuclear, biological or laser weapons in space. but kinetics...

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.

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.
- at least close enough
  To whose standards exactly? Dick Cheney's?
- 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.
- no, not really, it still gives you multiple km spread
- Someone (veritasium?) Already did an episode on this and concluded even at like 500 feet up from ground, without an active guidance system, it's up to luck to hit within a reasonable distance, IIRC.
this ignoring the tiny little issue of overheating during reentry
- Well that's why one of the proposed materials is tungsten, the problem with that being that tungsten is a bit heavy.
- Way too many variables to accurately fire an inert projectile through that much atmosphere without being guided at least part of the way.
And how are you going to even deorbit the things?

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.

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).
- 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.
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.
And friction would cost some work both way
- Yes but it's a 30 ft tungsten telephone pole. With that mass on size, there is minimal air resistance and free fall as it falls perpendicular
US air force put an unmanned craft into orbit for 12+ months with a large enough payload to test this.
They did it last year or year before?
- TheX-37B? They definitely didn’t test that for this. The capacity weight is 227 kg.
Gravity is your friend. It's more when it's in orbit that you should be careful.
- Gravity is not your friend. Getting stuff into LEO is still expensive af. A kinetic projectile dropped from space might have the same energy as a nuke, but it's still going to be a lot more expensive. Additionally, you don't have options on how that energy is released. It's going into the ground and that's that. A nuke (or any other explosive device for that matter) on the other hand can be detonated at a chosen altitude, or as a bunker buster if that's what you want.
  The heavier the object, the more it's going to take to push it out of that orbit. If your weapon system is in LEO, you can realistically only drop a rod on a small envelope along the future trajectory of the weapon system. Polar orbits would have the best coverage, but fly over a target outside of polar regions only twice a day. In order to get a wider range of firing solutions, the projectile needs considerable deltaV for orbital changes. And again, gravity fucks you over here because deep within Earth's gravity well, changing the orbit of a massive tungsten rod takes a lot of fuel. Higher up these deltaV costs wouldn't be as prohibitive and you'd have more options for using the weapon, but that would increase the time from launch to impact into the regieme of hours, way too slow for anything.
  The best solution would be to have a huge amount of rods in different orbits (akin to the spacejunk that is Starlink) to maximize the chances of at least one being able to fire on a target at any given place at any given time, but because those rods are still heavy af, such a plan is completely unfeasable.
  Rods from gods will never happen, at least not around Earth.
- It is simple conservation of energy. All the energy that creates the impact, must come from somewhere. A huge metal rod that lies on the ground is not going to cause any harm, aside from stubbing toes maybe.
  Leaving small height differences between the rockets launch site and the final impact site aside, the energy comes either from the rocket that brings it into space, or from propellent that the metal rod uses when launched on its target (it being a missile itself). So you end up at minimum with a rocket to transfer the whole thing into orbit, that is loaded with fuel with the same energy as the energy at the impact site. Given the rocket fuel problem, it is much more fuel, as you also need to carry the fuel for the later stages of the transport rocket up too. Then you also need additional energy for the friciton and to steer the metal rod into its designated target.
  Either way you end up either having to assemble the weapon in space, or having a rocket fly into space with enough fuel to release more energy than the weapon could release on impact. So in terms of the claim of force akin to a nuclear weapon, you also need fuel with enough energy like a nuclear weapon.
  Gravity does not help at all. You cannot "imbue" an object in an energy field with more energy, than you spend on changing its position gainst the field.

There has actually been multiple occasions were Russia was caught trying to break that treaty, kind of interesting to think about. The question is if Russia does actually mobilize an orbital nuclear weapon someday like an advanced Sarmat or some kind of space bomber, will the nations of the world act in unison or watch in silence?

Have fun with that existential dread while I work on my laundry.

They are super far from having that kind of money. Anyways the US would know early enough to stop it.
- True I bet the Russian Oligarchs would secretly siphon that project's funds in moments, just like they did to the Russian Navy.

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

Magic The Gathering has a lot to answer for.
It has a special exemption as long as it's not used on a Yom Tov

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.

That's why the eventual strategy would be to build them in space with minerals from the asteroid belt.
- That would involve building a factory in space. If we're capable of doing that, creating a kinetic OWP with which to bombard the earth would be small ambition.
Also the tungsten oxides produced in high velocity impacts are potentially worse than fallout.
Gotta mine them in space, but there's still a whole host of other issues with the idea including aiming them, having enough stations to deploy them anywhere on the planet in a reasonable amount of time, and the other non-radioactive problems that result from throwing a fuckton of tungsten at terminal velocity into something.
lol "the United States state."
- Yes. The United States of America is, itself a federated state that also represents the fifty states. It's why we have a state department and a Secretary of State in the White House.
There was a YouTube video with, I think action lab, where they tested this weapon on a smaller scale with sand castles.
The experiment failed overall because of the difficulty of aiming the payload and anticipating the correalis effect
- Veritasium I think.
- I remember that this was one of the factors that weirded up the whole cold war. ICBMs are hard to aim, though in the US we were able to find a workable solution. (A Polaris could drop a retarded-descent pizza into my driveway and then conveniently dispose of itself in the nearby unused lot.)
  Soviet missiles were not so accurate, so they just build bunches of them hoping to hit their targets through sheer redundancy. (This became dinner talk at Cal-Tech in the eighties since SDI was expected to be able to intercept the entire Soviet nuclear arsenal, including bunches of decoys) So their redundancy was used by General Electric to promote the missile gap, as justification why we needed to buy more GE nukes to close the difference.
  This is why, I'm pretty sure, we don't really need to be too afraid of DPRK going madman with their handful of nukes. So far we've seen the Kims lob ICBMs into the pacific, but they haven't shown they could hit a given continent, let alone someplace important, and the US knows from its own experience that ICBM math is hard.
Ah yes, we would do that, definately haven't already started... no, of course not.
- It's well within the character of the US federal government and the armed forces to go forward with an OWP platform program right now, even despite the risks and ethics concerns, sadly.

It is a pretty great book, although it's a shame that Heinlein spent so much of his time being a douchey libertarian warhawk.
This idea was expanded upon in The Expanse series as well, with the added benefit of using small asteroids and pushing then into highly elliptical orbits designed to hit Earth at random times anywhere from a few weeks to several years later so your Inner System opponents have to spend a huge chunk of their resources watching for them without knowing if/when any other rocks will hit.
- It's funny, because tracking big rocks months/years in advance is what we currently do really well, and iirc we update all trajectories of all known objects orbiting earth at least every 11 days, and the main problem is figuring out which is which when they are maneuverable, not where they are going.
  There's currently about 750 000 things being tracked in earth orbit. The total number of asteroids is about twice that, so without upgrades we can still refresh each object every month, and with active space flight I'd guess that would be done much much more often.
  Although, doing the math, enough Epstein drives (guesstimating tens) on a smaller asteroid could yield up to 1 m/s² acceleration, meaning an asteroid could traverse the distance from asteroid belt to earth in about a week.
- The expeditionary force series expanded that further with guided asteroids accelerated to near light speed orbiting the galaxy.
- KSR did something similar in 2312 where multiple small asteroids were programmed to impact at the same point same time which had the effect of a larger impact thanks to kinetics but undetectable due to being small objects of various origins that would have looked random even if detected
TANSTAAFL

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.

Doors and corners, kid.
Other recommended book series for scifi physics:
Expeditionary Force
Bobiverse

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

You could spin and release it, effectively tossing it out of orbit like a catapult.
- Then you end up with the same problem

Inyalowda love rocks, so let's give dem sum, sasa ke
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
- i'm not sure that drag even matters that hard, you need big sectoral density and a way to prevent tumbling
  https://en.wikipedia.org/wiki/Impact_depth
  Meteorite: As may be concluded from the air pressure, the atmosphere's material is equivalent to about 10 m of water. Since ice has about the same density as water, an ice cube from space travelling at 15 km/s or so must have a length of 10 m to reach the surface of the earth at high speed. A smaller ice cube will be slowed to terminal velocity. A larger ice cube may also be slowed, however, as long as it comes in at a very low angle and thus has to pierce through a lot of atmosphere. An iron meteorite with a length of 1.3 m would punch through the atmosphere; a smaller one would be slowed by the air and fall at terminal velocity to the ground.
  talking about tungsten we're looking at minimum 50cm long darts, however this ignores atmospheric erosion
- If it was going fast enough wouldn't it just blow through that before it had a chance to fall apart too much?

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

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

Science fiction always challenges my suspension of disbelief is when people land on planets to skirmish with conventional weapons instead of, say, throw a big heavy aerodynamic solid rock from space.

In the Expanse series Earth and Mars are at war. They can easily throw rocks and totally destroy the other side. Not just beat them in a war, like totally wipe them out. But Mars knows if they start throwing rocks all bets are off and Earth will wipe them out. Just as Earth knows the same, if they wipe out Mars, Mars will make sure the Earth is destroyed.
It's an analogy of the current situation we have with nuclear weapons. During the Cold War Russia made sure they could wipe out the US if the US ever tried a first strike and the US made sure they could wipe out Russia if they ever tried something. The Mutually Assured Destruction (MAD) prevented anyone from taking the first step. These days the playing field is a bit more complex, but the same principles hold for now.
Of course in the Expanse there is a third party with nothing to lose that at one point employs such a weapon of mass destruction. But let's just hope that part isn't a mirror for reality.
- I see you've skipped the most advanced detection and targeting systems connected to a network of orbital railguns, and the fact all of that is constantly pointed at Mars in case they launch stealth nukes. Inarocks are not a valid war strategy, and only extreme levels of preparation and corruption allowed a few chunks to hit Earth.
You can make good reasons or at least plausible ones. 40k has planetary shields. There could be a civil war so neither side might want to destroy the surfaces of each planet and civilians. Battletech has spaceship tech being rare and irreplacable, and there are treaties limiting orbital and nuclear bombardment.
Sometimes the most realistic route just isnt fun though so i can usually look past the contrivances.
Good sci-fi usually treats this on par with using nuclear weapons (which it kinda is?). In Babylon 5, mass drivers are banned by intergalactic treaty, and when one race uses them anyway it literally bombs their victims back into the stone age, and it's treated as a horrifying event --one of the character's defining moments in the show is just him looking on silently in horror.
- Kinetic drives are mass drivers. Unless you use some kind of teleportation or space warping for travel, every ship is a weapon of mass destruction. Every old boat is a surprise WMD, every craft a viable nuke with zero preparation.

Neil Tyson said this is entirely impractical.

Neil Tyson needs to shut the fuck up and stop cockblocking me from having based weapons
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?
- 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.
- "Why would anyone use a gun when you can just use a hand-held explosive?"
Pop scientists routinely mis-represent facts to make warfare seem unappealing and lame, this is due their 'sense of morality' (read: crying baby noises).
For example, Carl Sagan warned that operation desert storm would cause a (non)nuclear winter and mass famine in Asia.
- Tbh, that's fair enough.

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.

I mean, launch costs are going down over time. It might make much more sense to put many warheads up with a reusable system like falcon (_{3000$/kg) than it does to maintain a fleet of necessarily single-use systems like minuiteman (7,000,000$/}300kg = 23,300$/kg). You might well be able to put four warheads (with an equal mass of de-orbiting propellent into orbit - ~1.7 km/s given solid fuel) for the same cost as one ICBM.

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.

For another take on Kinetic impactors try The moon is a Harsh Mistress or as they call them. Tossing rocks down the gravity well.

I remember how in the book people show up to the announced site to watch it like tourists, and of course they get atomized. Same idea appears in Independence Day. I always thought “that would never happen, people aren’t that stupid”, but the pandemic changed my mind on that front.
- People were picnicking at the first battle of the american civil war, pretty sure a couple died.
  Never underestimate human stupidity.
- I mean in Indepedence day they wanted to "welcome" the aliens. What you're talking about is akin to driving towards where a nuke is about to drop i.e. only for the suicidal
Or try the Expanse!
Heinlein comes off a bit fascist these days but that’s me.
- His books are often (mostly?) social and governmental thought experiments. You'll find a vast range of ideas if you read all his stuff.
- Care to elaborate that unfounded opinion?

Mollari disgust level: Rising.

There was one in the G.I Joe movie.

Glad I wasn't the only one who thought this when I read the headline! It ended pretty badly for London if I remember right.

I'm gonna leave this here. Excellent video by Veritasium, looking at the practicality and plausibility of "rods from god"

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

2003 United States Air Force proposal

A system described in the 2003 United States Air Force report called Hypervelocity Rod Bundles[10] was that of 20-foot-long (6.1 m), 1-foot-diameter (0.30 m) tungsten rods that are satellite-controlled and have global strike capability, with impact speeds of Mach 10.[11][12][13]

The bomb would naturally contain large kinetic energy because it moves at orbital velocities, around 8 kilometres per second (26,000 ft/s; 8,000 m/s; Mach 24) in orbit and 3 kilometres per second (9,800 ft/s; 3,000 m/s; Mach 8.8) at impact. As the rod reenters Earth's atmosphere it would lose most of its velocity, but the remaining energy would cause considerable damage. Some systems are quoted as having the yield of a small tactical nuclear bomb.[13] These designs are envisioned as a bunker buster.[12][14] As the name suggests, the 'bunker buster' is powerful enough to destroy a nuclear bunker. With 6–8 satellites on a given orbit, a target could be hit within 12–15 minutes from any given time, less than half the time taken by an ICBM and without the launch warning. Such a system could also be equipped with sensors to detect incoming anti-ballistic missile-type threats and relatively light protective measures to use against them (e.g. Hit-To-Kill Missiles or megawatt-class chemical laser). The time between deorbit and impact would only be a few minutes, and depending on the orbits and positions in the orbits, the system would have a worldwide range. There would be no need to deploy missiles, aircraft, or other vehicles.

In the case of the system mentioned in the 2003 Air Force report above, a 6.1 by 0.3 metres (20 ft × 1 ft) tungsten cylinder impacting at Mach 10 (11,200 ft/s; 3,400 m/s) has kinetic energy equivalent to approximately 11.5 tons of TNT (48 GJ).[15] The mass of such a cylinder is itself greater than 9 short tons (8.2 t), so the practical applications of such a system are limited to those situations where its other characteristics provide a clear and decisive advantage—a conventional bomb/warhead of similar weight to the tungsten rod, delivered by conventional means, provides similar destructive capability and is far more practical and cost-effective.[16][17][18]

The highly elongated shape and high mass of the projectiles are intended to enhance sectional density (and therefore minimize kinetic energy loss due to air friction) and maximize penetration of hard or buried targets. The larger device is expected to be quite effective at penetrating deeply buried bunkers and other command and control targets.[19]

The weapon would be very hard to defend against. It has a very high closing velocity and a small radar cross-section. The launch is difficult to detect. Any infrared launch signature occurs in orbit, at no fixed position. The infrared launch signature also has a much smaller magnitude compared to a ballistic missile launch. The system would also have to cope with atmospheric heating from re-entry, which could melt non-tungsten components of the weapon.[20]

The phrase "rods from God" is also used to describe the same concept.[21] An Air Force report called them "hypervelocity rod bundles".[2]

It cannot hit with the force of a nuclear weapon, but it can be powerful