That animation shows the warhead spinning at about 250-350 RPM which seems reasonable to me.
FWIW, this Harvard University research digest gives credence (virtually in passing) to the idea that reentry vehicles are spin-stabilized, but doesn’t give specifics like rotational velocity or spin rate (as such specifics would almost certainly be deeply classified design details).
If such asymmetric forces went uncompensated, they could cause the RV to veer far off its original course. In order to prevent this, the RV is stabilized by spinning it, much as a football is spun when it is thrown.
(Bottom of page 71)
I’m pretty sure the LLM is just making up the “thousands of RPM” bit.
I’ve seen LLMs described as deciding what word should come next based on probability, as defined by the sum total of its “training”. so when it’s been feed a gazillion documents that talk about high-RPM spin stabilization for warheads - even though most of those documents are referring to projectiles fired out of guns - it may choose to write those same words in reference to nuclear warheads, for which the spin rate is likely much lower.
A bullet fired from a rifled barrel can spin at over 300,000 rpm (5 kHz), depending on the bullet’s muzzle velocity and the barrel’s twist rate.
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For example, an M4 Carbine with a twist rate of 1 in 7 inches (177.8 mm) and a muzzle velocity of 3,050 feet per second (930 m/s) will give the bullet a spin of 930 m/s / 0.1778 m = 5.2 kHz (314,000 rpm).
I think the comparison to bullets is interesting. From looking at a few sources online, it is common for rifle bullets to be be spun up to hundreds of thousands of RPMs.
I am pretty sure they don’t spin bullets faster than they need to, because that is wasting energy, so high RPMs for stability seems believable.
However, reentry bodies are larger and higher speed. I would assume that the larger size would lower the RPMs, because it is more massive (less likely to be easily deviated by atmosphere) and the materials would not likely be able to survive hundreds of thousand of RPMs. I do not know how the higher speed would affect it.
I am sure the real answer is classified, but I think someone who is smart on the subject of aerodynamics could get ballpark close.
Ideally, a bullet should fly through the air like a football, with its nose always pointed in the direction of travel as it arcs through the air. If you spin the bullet too fast, it becomes too gyroscopic and the nose of the bullet doesn’t follow the arc, and the bullet becomes much more inaccurate.
Correct. MIRVs by definition are simply unguided hurtling rocks after they are released from the bus. Which bus, and the missile that sent it, are responsible for giving each warhead the final orientation and shove in just the right direction to fall where desired. Well, desired by the sender, if usually not by the recipient. 
There was an effort to create the
But that came to mostly naught.
The closest relative to the MARV concept today is the
The warheads are not glowing. The air around the warheads is glowing. Somewhat akin to how lightning works. The air is flash-heated to incandescence by the shock of being nearly instantly shoved out of the warhead’s way.
Yes. Any solid object exceeding Mach 1 creates a sonic boom the entire time it is traveling at Mach 1+. Which in the case of a warhead means from when they first encounter the top of the atmosphere at the beginning of reentry all the way to ground impact.
But since they are traveling much faster than the speed of sound there’s no geometry where you’ll hear the noise first. Assuming a dud or inert round so we’re not interested in the explosion, you’ll see it descending, perhaps 200 miles away from you and perhaps from directly overhead coming straight down.
Once it hits the ground and stops moving the sound will get to you eventually if it isn’t dissipated in the atmosphere before it gets that far.
Striking a pinpoint target or targets with a warhead or series of MIRVed warheads fired from a hypersonic missile on a parabolic trajectory from 100+ miles high is some fancy shooting, pardner. Surely on the latest and greatest doomsday weapons, wouldn’t the descending warhead need thrusters or fins to ensure pinpoint accuracy to within the desired circle error probable/probability?
Wikipedia notes: “While the United States phased out the use of MIRVs in ICBMs in 2014 to comply with New START, Russia continues to develop new ICBM designs using the technology.”
Wikipedia also notes: "In a MIRV, the main rocket motor (or booster) pushes a “bus” (see illustration) into a free-flight suborbital ballistic flight path. After the boost phase, the bus maneuvers using small on-board rocket motors and a computerized inertial guidance system. It takes up a ballistic trajectory that will deliver a re-entry vehicle containing a warhead to a target and then releases a warhead on that trajectory. It then maneuvers to a different trajectory, releasing another warhead, and repeats the process for all warheads.
Minuteman III MIRV launch sequence: 1. The missile launches out of its silo by firing its first-stage boost motor (A). 2. About 60 seconds after launch, the first-stage drops off and the second-stage motor (B) ignites. The missile shroud (E) is ejected. 3. About 120 seconds after launch, the third-stage motor (C) ignites and separates from the second-stage. 4. About 180 seconds after launch, the third-stage thrust terminates and the post-boost vehicle (D) separates from the rocket. 5. The post-boost vehicle maneuvers itself and prepares for re-entry vehicle (RV) deployment. 6. While the post-boost vehicle backs away, the RVs, decoys, and chaff are deployed (this may occur during ascent). 7. The RVs and chaff reenter the atmosphere at high speeds and are armed in flight. 8. The nuclear warheads detonate, either as air bursts or ground bursts.
The precise technical details are closely guarded military secrets, to hinder any development of enemy counter-measures. The bus’s on-board propellant limits the distances between targets of individual warheads to perhaps a few hundred kilometers.[19] Some warheads may use small hypersonic airfoils during the descent to gain additional cross-range distance. Additionally, some buses (e.g. the British Chevaline system) can release decoys to confuse interception devices and radars, such as aluminized balloons or electronic noisemakers.
Accuracy is crucial because doubling the accuracy decreases the needed warhead energy by a factor of four for radiation damage and by a factor of eight for blast damage. Navigation system accuracy and the available geophysical information limits the warhead target accuracy. Some writers believe [weasel words] that government-supported geophysical mapping initiatives and ocean satellite altitude systems such as Seasat may have a covert purpose to map mass concentrations and determine local gravity anomalies, in order to improve accuracies of ballistic missiles.[citation needed] Accuracy is expressed as circular error probable (CEP). This is the radius of the circle that the warhead has a 50 percent chance of falling into when aimed at the center. CEP is about 90–100 m for the Trident II and Peacekeeper missiles."
https://en.wikipedia.org/wiki/Multiple_independently_targetable_reentry_vehicle
Bullets are spun enough to give maximum stability to each design. In general, if you keep the diameter the same the length of the bullet determines it’s required rotation. The longer the bullet, the higher the twist rate. Most shooters use the bullet’s weight as the determining factor since they are listed that way and the weight increases as the length increases. But it’s length that is in the actual calculation.
(150 x Diameter squared) / Bullet Length = Twist Rate.
That would be a Manueverable Reentry Vehicle (MaRV), which @LSLGuy mentioned a couple of posts back.
If you look at that Wikipedia article, you’ll notice that no ICBM integrates any MaRV. The list shows medium-range or short-range ballistic missiles, the accuracy of which often suffers because of their mobile launchers, and one retired Russian Submarine Launched Ballistic Missile.
Incredible as it seems, modern high-accuracy ICBMs attain their highly accurate CEPs without any kind of terminal guidance or maneuver capacity.
We don’t know anything about next-generation strategic missile systems, since that would obviously be highly classified.
Not sure what you’re talking about here; they absolutely need precision if they’re being used for counterforce strikes or against hardened targets.
ISTR reading somewhere that the Minuteman III missiles of the era (I think this was a 1990s book) had a CEP (circular error probable) small enough that if one was aimed at the pitcher’s mound of Yankee Stadium, that the warhead would actually hit somewhere within the stadium. The reason is because when you’re aiming at a hardened silo, command post, or something along those lines, you DO actually have to hit pretty close in order to ensure its destruction, even with a medium yield nuke.
ICBMs/SLBMs are pretty amazing things- they launch them from somewhere, and they fly for thousands of miles, and then hit within a couple hundred meters or less of their target (Trident II CEP is about 100 meters), all without any sort of terminal guidance, and generally using solid fuel motors. That’s a pretty amazing technical, engineering, and manufacturing feat, if you ask me.
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I haven’t argued anywhere against a need for precision; it just wasn’t clear to me how that precision was to be achieved. Considering the time of flight and the distance traveled through the atmosphere, it’s amazing to learn that they can achieve such a small CEP without any guidance after being released from the bus.
Well, it depends on the target. If you’re trying to take out a hardened bunker, then you need precision for that, but if you’re trying to take out a city, or an ordinary military base, or a ball-bearing factory, then you can be anywhere within a few miles of your target. And not all missiles need to carry MIRVs: If you’ve got a target where pinpoint accuracy really is needed, you could put that warhead on a dedicated missile that does have some degree of terminal guidance.
That then depends upon your military doctrine for a nuclear attack.
Nobody is expecting to be taking out cities or ball bearing factories as part of a nuclear exchange. The war is not going to last long enough for any of that to matter.
Mutually assured destruction is a matter of assuring the opponent that they will be militarily crippled to the point that they are totally defenceless. Also many megadeaths. But they are incidental. The entire doctrine depends upon hitting the hard military targets of the opponent, rendering the opponent impotent. Any idea of a first strike capability makes this even more so. Which is why first strike is so hard. MAD does of course mean we expect the same in return. if we strike first.
A war will last maybe a few hours.
Every warhead needs to pick off a designated target with high precision. Those that don’t are just wasted effort. There just aren’t any useful big dumb targets. Blind retaliation killing civilians by the millions really serves no useful military value. It is just a threat, and as much as the niceties of the various treaties go, illegal - basically a war crime. Whereas we might like to paint the opposition as bloodthirsty criminals with no moral principles who eat babies, we might hope that we are above such things, and won’t go nuking major cities full of innocent civilians out of spite.
Military value, no.
Value, yes. As a threat. You hold a nation’s existence as hostage by being able to attack “counter-value”, as the term of art goes. (As differentiated from “counter-force”, which means degrading an adversary’s direct strategic military capabilities.)
The more precise you are, the less yield you need. The less yield you need, the smaller the weapon. The smaller the weapon, the more you can fit onto launch platforms, increasing the number of targets you can strike. You’re arguing against something that was already accomplished and has no real downside. And you’re arguing against what the designers and strategists felt needed to happen, since we put a lot of work into making the weapons more accurate.
Practically, there are no missiles like you describe. Regular ICBMs even with single warheads do not have terminal guidance - it’s quite difficult to guide something that’s falling from space at 15000 mph. Control surfaces would burn up, and I suspect there are difficulties even seeing/detecting a target in front of you when you’re compressing the air that hard. Sure, there are regular bunker busting bombs and missiles, but these are on conventional bombers or short ranged missiles that would arrive far too late to be relevant in a nuclear exchange.
You’re more or less saying that a problem we already saw the need to solve, and solved, isn’t a problem.