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[Cryxis, Prince of Doom]

Ok, I have a question about something that I am using in a story that I am writing.

The story is based about 150 years after a great war that disassembles society into nomadic/tribal groups and leaves most of the cities and population dense areas piles of rubble or abandoned.

The question is, after a kinetic rod impacts does it collapse and become a large lump of material or does it stay a solid rod sticking out of the crater it makes or does it just bury itself deep in the ground leaving everything else around destroyed with a crater with a hole in it? Or better what does the impact of a kinetic rod look like after the dust has settled? ((Currently going with a tungsten carbide rod, I will include size if necessary, not sure if it scales or if bigger rod makes a different impact (as in what happens with the rod and crater) than smaller rod))

[Rolepgeek]

I'm a bit curious, though, what even is your "objective" time?  Rest time?  I was under the impression that one of the big things about relativity is that there is no such thing as a universal referential frame, since there's no such thing as a universal rest frame; motion is always measured with respect to some external referent.  The only thing there is is a subjective frame as perceived by the, in this case, individual traveling at relativistic speeds.  The closest you can get is some inertial reference frame.

So, here's what I've never understood. Because light always goes the same speed, couldn't you use something going ~C slower than the speed of light as your reference frame? Couldn't you measure it via that, since you can have things going at near light speed in opposite directions, and have something that perceives them each as being stationary, or whatever? I don't know if I'm making sense.

Ok, I have a question about something that I am using in a story that I am writing.

The story is based about 150 years after a great war that disassembles society into nomadic/tribal groups and leaves most of the cities and population dense areas piles of rubble or abandoned.

The question is, after a kinetic rod impacts does it collapse and become a large lump of material or does it stay a solid rod sticking out of the crater it makes or does it just bury itself deep in the ground leaving everything else around destroyed with a crater with a hole in it? Or better what does the impact of a kinetic rod look like after the dust has settled? ((Currently going with a tungsten carbide rod, I will include size if necessary, not sure if it scales or if bigger rod makes a different impact (as in what happens with the rod and crater) than smaller rod))

Same thing as if you blew it up with an actual nuclear device. It basically disintegrates on impact. Crater looks like any other crater, with a rather higher amount of tungsten and carbon below the dust.

[Cryxis, Prince of Doom]

So no remnants of the buildings or the rods in the immediate area of the impact, severe damage to the buildings close enough to receive the brunt of the shockwave, and rubble/minor damage to buildings outside of that?

[Rolepgeek]

More or less, yeah. Immediate area of impact is unlikely to have one stone standing upon another, or even existing, with the size of that area dependent on the size of the rods. It's just too much energy hitting for anything right there to survive.

[Culise]

That said, it depends on the size of your rods.  The 2003 incarnation of Rods from God was "only" 11.5 tons of TNT; for comparison, this puts each single rod at just under two Grand Slams from World War 2, or one rather light tactical nuclear bomb.  Getting hit by Grand Slams would do a number on the target, but it wouldn't vaporize much beyond the immediate area; you'd probably end up with at least some slag and shrapnel from the rod, though it might not be recognizable to a Neolithic society.  On the high end, the older conceptions by Pournelle and other sci-fi authors envisioned higher velocities and masses, and thus much higher yields; I believe the upper scale for these could easily result in what Rolepgeek described.  One major thing to note with Rods from God is that they are designed for penetration; a lot of that force is going to be going in a very specific direction, rather than spread out like a surface-blast nuke.  I mostly mention this to hedge various bets; if you're talking about a not-too-distant future war that has completely knocked society back to the Neolithic, you're likely talking about something closer to Pournelle than the Air Force report. 

So, here's what I've never understood. Because light always goes the same speed, couldn't you use something going ~C slower than the speed of light as your reference frame? Couldn't you measure it via that, since you can have things going at near light speed in opposite directions, and have something that perceives them each as being stationary, or whatever? I don't know if I'm making sense.

I'm not sure if I quite understand.  Are you asking if there can be a single frame of reference in which two objects going in opposite directions can both be simultaneously "stationary," or are you asking if there can be two inertial frames of reference with an apparent velocity of approximately c between them?  The former is one I'm having difficulty picturing.  As for the latter, actually, I believe it is possible, though I'm no physicist.  In fact, there are galaxies moving away from us at apparent velocities greater than the speed of light.  This is mostly because inertial frames of reference get a bit wonky when you need to take the expansion of the universe into account; neither galaxy is moving, per se, but rather, the space between them is physically being stretched at tremendous rates.  In other words, inertial frames of reference (that is, non-accelerating, gravitationally flat) are no longer valid approximations on intergalactic scales.  If this feels slightly familiar, it's because from the Alcubierre drive to the warp drive, the distortion of space-time is one of the big ways in which hypothetical FTL has been suggested to operate.  That said, you can't really move an object to approximately lightspeed without that pesky Lorentz factor driving the energy costs up, and accelerating reference frames are non-inertial. 

((By the bye, the reason we can see these galaxies in spite of the fact that they're outpacing the light they send out is only because the rate of expansion of the universe is increasing at an accelerating rate.  As they weren't always moving away from us at such a tremendous relative velocity, we can still see the light they put out when they were moving STL.))

[mainiac]

"Honor" is the resistance to the gun in early Japan, because it invalidated the skills of a whole noble class. It also got tossed out the window due to pragmatism.

Japan didn't resist the guns early on.  As soon as they were exposed to them Japanese warlords eagerly adopted the new weapons, encouraged arms industries in their own domains and developed sophisticated indigenous tactics and manufacturing techniques.  Ironically given all the crappy Japanese military techniques that are treated as amazing, Japanese musket tactics were in fact ahead of their time.

In the 1600s, the Tokugawa shogunate correctly understood that guns were a threat to their power and imposed punitive gun control measures.  He was the last in a long line of rebellions that had used guns to equip large peasant armies and upset the old power structure.  By imposing strict gun controls, he was solidifying the social structure with him at the top.  When the peace broke down 200 years later, everyone immediately started using guns again without hesitation.  The firearm ban wasn't about "honor", it was practicality.  It's a lot easier to bribe a small warrior caste if they cant easily arm a hundred thousand peasants with guns and start a rebellion.  And for the nobles there is something to be said about a law that keeps you alive after watching your father and grandfather die in fifty years of civil war.

And this is one of the reason why weapon predictions are so hard to make (especially about the future).  Even if you can guess what will be technologically possible, you also need to guess who wants to fight who.  If the government has a vested interest in making standing armies hard to form, you can have well understood military technologies go away like Japanese muskets.

As an interesting analogy, my pet theory for star wars is this explains why the tie fighters are so crappy.  Anakin was a star fighter pilot who rebelled and he knew how dangerous star fighters are in the hands of a rebel.  Vader and the emperor didn't want to make it easy for their military to turn on them.  It's easier to keep track of thousands of star destroyer commanders then millions of fighter pilots.  So the empire intentionally discouraged the development of good starfighter designs.  Instead they had the tie fighter, something that can kill even the best pilots and lacks warp drive and landing gear so it is forced to stay with it's star destroyer.

[Rolepgeek]

Well, what I was trying to say is that if you have one object going ~C in direction +X, and another going ~C in direction -X, then if you have something in between them that sees them as both moving about the same speed away from itself, at X=0, then couldn't that establish a stationary reference frame? Something stationary with respect to the speed of light in any given direction, so to speak?

Or with spatial expansion? Find the region of space everything is expanding away from, and establish that as the center of the universe.

Speaking of which, spatial expansion is sorta like the flat energy of what we think of as empty space spreading out to fill it's surroundings, right? Or thereabouts? Would it therefore be conceivable for different universes with different mass totals to operate somewhat like stars in how they form and live and die? Like, if ours had been a bit smaller, than Einstein would have been right in the first place, there wouldn't have been quite enough force in the Big Bang for the universe to stretch beyond whatever limit exists, and it would have eventually contracted inwards again? Or is it the opposite, that we don't have enough mass for gravity to pull us back in before the critical point at which things were too far apart and it simply falls outwards again? Almost like a bubble or water droplet hitting a surface, and either smashing out, or almost 'bouncing' back into a drop again.

[Culise]

Well, what I was trying to say is that if you have one object going ~C in direction +X, and another going ~C in direction -X, then if you have something in between them that sees them as both moving about the same speed away from itself, at X=0, then couldn't that establish a stationary reference frame? Something stationary with respect to the speed of light in any given direction, so to speak?

Or with spatial expansion? Find the region of space everything is expanding away from, and establish that as the center of the universe.

Speaking of which, spatial expansion is sorta like the flat energy of what we think of as empty space spreading out to fill it's surroundings, right? Or thereabouts? Would it therefore be conceivable for different universes with different mass totals to operate somewhat like stars in how they form and live and die? Like, if ours had been a bit smaller, than Einstein would have been right in the first place, there wouldn't have been quite enough force in the Big Bang for the universe to stretch beyond whatever limit exists, and it would have eventually contracted inwards again? Or is it the opposite, that we don't have enough mass for gravity to pull us back in before the critical point at which things were too far apart and it simply falls outwards again? Almost like a bubble or water droplet hitting a surface, and either smashing out, or almost 'bouncing' back into a drop again.

Well, in the first case, you can do that without requiring objects to be moving at c.  The catch, however, is that it makes no difference whether you measure from this inertial reference frame or any other inertial reference frame; the math comes out the same.  Moreover, this reference frame isn't and cannot be stationary with respect to all inertial reference frames either, which can be trivially seen from how we defined it originally; with respect to the reference frames attached to either of our relativistic objects, it's also going to be receding at approximately c as well.  We could certainly define a reference frame at such for the sake of convenience, though, and there certainly is quite a bit of convenience in defining some external stationary observation frame for the purpose of determining relativistic effects.  We define such frames for reference all the time; for instance, driving down the some city road would be an interesting adventure if we defined our car's velocity with respect to Jupiter or the Sun instead of the road underneath our tires. 

In the second case, I think you're subtly misunderstanding the expansion of the universe.  It's likely due to the vernacular of the Big Bang being perceived as this sort of burst out from a single point, but it's actually that space is expanding everywhere at every point.  In fact, one of the consequences of this is that galaxy redshifts are proportional to distance from us here on Earth; that is, galaxies further away from us are moving faster, which implies that if such a "center" exists, it's wherever the observer is located.  The metric expansion of space has been established to be intrinsic, and will thus exhibit a similar "apparent center" effect no matter where the observer is located, whether it's here in the Milky Way, in Andromeda, or far off in Abell 1835 IR1916. 

I won't touch the last point at this particular moment, though, mostly because it's quite late here.  Sorry. 

[Amperzand]

So no remnants of the buildings or the rods in the immediate area of the impact, severe damage to the buildings close enough to receive the brunt of the shockwave, and rubble/minor damage to buildings outside of that?

It's really important to note that with K-rods, unless you're basically just dropping rocks as a WMD, they're intended as precision anti-fortification weapons. The version we considered actually building was basically a tungsten telephone pole, and while it "only" had the energy of ~11 tons of TNT, all that energy was put into a contact patch like a foot across. It isn't explosive energy, it's kinetic. A bullet, not a bomb. You'll get some shockwave effects, but mostly it just punches a really deep hole in almost anything you could put in the way. Definitely not going to be anything recognizable after impact, because tungsten likes to shatter when it hits things, so it'd likely become dust with this kind of force.

Just slowing a big rock down slightly to drop it on somebody is a little more along the lines of a bomb, with the penetration it can achieve being secondary to the "Splash". A really big explosion, basically. You'd even have a mushroom cloud, if the impact was small enough not to just look like an expanding circle from orbit.

[Insanegame27]

New thingy: In a story I'm writing, the protagonist ends up running from a squad of special forces who manage to keep catching up only to lose him. This unit of special forces is designed for insertion and survival anywhere on the planet, from tundra to deserts to mountains, and the thing I'm trying to design would be standard and lightweight across all scenarios.


Currently the Specialist Hazardous Insertion and Termination (the oh SHIT suit) suit consists of three plates of lightweight and strong metal plates as armor (one on each side of chest and one protecting the gut) stitched between two layers of kevlar. Two icepicks are hooked into a belt, replacing knives in the loadout. Around the waist is a belt with a rappel harness built-in and two rappel cords stored in a pouch on the belt. The collar of the suit has metal plates in a way that is intended to stop shrapnel (or anything else) from decapitating the wearer, with a hardened clear plastic faceplate (similar to riot troopers). The suit is nearly a full-body suit, except a helmet needs to be worn and the gloves and boots are not parts of the suit. Webbing and holsters and the like can be put over the suit if need be.
The standard loadout for these soldiers are a machine pistol and an SMG, both with suppressors. Various grenades are used and are one of the few variations these soldiers have. If they need to sleep but are needed elsewhere, they sleep in the suit on the chopper. You need to piss... that's not a function of the suit, get your mate to cover you while you do your business.


These soldiers are designed to be able to be tactically inserted and fight literally anywhere without changing the loadout beyond restocking ammunition enroute. As an example, in the story they go from pursuing the protagonist in the desert, to storming a nuclear submarine nearby, and then hunting the protagonist in a skyscraper (one team cutting off rooftop escape, one team cutting off ground-access and eight teams searching the skyscraper for him. The only thing they change in their loadout is one of them accidentally replaces a frag with a HE grenade. The chopper (or other method of transport) will have stocks of everything on board. Lost your icepicks on the mission? The chopper has some there. Faceplate got wrecked? New ones on the chopper. Broken gun? Another identical one's on the chopper. You get the idea.


The thing is, I have no idea what stuff these suits will need to do all that stuff. Hypothetically, after the skyscraper situation they'll need to go storm a terrorist cell in the jungle someplace or hijack a plane. The most common insertion methods use a helicopter to get them in place, but the government (and thus the military) do use other forms of transport and insertion such as APC and wingsuiting from a plane (straight onto another plane in the story).


The soldiers ARE human however and do get time off work for family stuff and are paid and are liable to all those human faults. Most of the time there won't even be a single mission per day, it takes a lot of fecal matter hitting the fan to get one of these specialist teams inserted and when they go from one mission straight into another then it means that it is shittageddon out there.

[Tack]

That's pretty cool. Sucks that you're making these hard-as-hell stormtroopers in order to be the protagonist's bitch, but eh.

If the base armour was all coloured neutral grey then I guess you could get away with pulling camo webbing over the top.
If you were going to do a different camo of webbing for each different climate, then I'd expect you'd have all of the necessary survival tools for that climate in the webbing to begin with.

So I guess it'd either be one long-range VTOL with a bunch of different webbings and kits in it, or handy little color-coded choppers depending on where a specific squad is scrambling to.

Other than that, I got nothin'.

[Parsely]

-snip-

Plastic faceplate? Why? Obviously these guys are counter terror or something. Why even bother with something like that when you plan to be facing enemies armed with firearms? Soldiers in medieval times who were equipped with full helms had metal visors (you know, made of something that can actually protect their face if someone swings something at you) and it's not unheard of for even those soldiers to take the risk of fighting without them in order to have increased visual awareness. If your visors are made of plastic in a world full of guns, I suspect soldiers forced to take them along would either throw them away or fight with them raised anyways.

Suppressors are patently NOT something you just take all the time as a rule. They are a calculated choice based on the requirements of the mission. You can't just say they take this and that weapon all the time because real tactical units today don't do that. They pick their weapons based on what they anticipate. What advantage could there possibly be to forcing these men who are meant to be deployed anywhere to be totally inflexible in the equipment they use?

And ice picks...? Just no. It has none of the uses of a knife. Not only can a knife be used for things other than stabbing people, a knife can inflict more effective stabbing wounds because the blade is so wide. I get the strong sense that this is just a rule of cool thing and not a choice that actually has a coherent idea behind it.

Attachable neck plates are a thing in Marine Interceptor body armor (center) and AFAIK hardly anyone in combat uses them because the hard plates dig into your throat if you try to look straight down. If you're engaged in hand to hand, an enemy who you're wrestling with that deliberately pulls or pushes down on your head he can literally choke you out with your own armor. Unlike the ice pick this is actually something real soldiers are known to wear (though I haven't read any accounts of troops IN COMBAT who preferred to wear them) so don't consider this as strong an objection as the other points I've brought up.

[Tack]

I always assumed they were counter-knife stuff. Hence the plastic and the thin armor which wouldn't stop a proper bullet anyway.

Plus if you make them reflective then that has psychological bonuses, as well as a rule of cool thing, or a 'oh god i'm killing real people' reveal.

[Insanegame27]

That's pretty cool. Sucks that you're making these hard-as-hell stormtroopers in order to be the protagonist's bitch, but eh.


If the base armour was all coloured neutral grey then I guess you could get away with pulling camo webbing over the top.
If you were going to do a different camo of webbing for each different climate, then I'd expect you'd have all of the necessary survival tools for that climate in the webbing to begin with.


So I guess it'd either be one long-range VTOL with a bunch of different webbings and kits in it, or handy little color-coded choppers depending on where a specific squad is scrambling to.


Other than that, I got nothin'.

The base armor would be dark grey digital camo.
I think you misunderstand me on this point. All the equipment is the same no matter what mission. Hence you bring icepicks and miniature SCUBA gear to the desert and you bring the related desert gear on a diving mission. Obviously these things have restrictions, you're not going deep sea diving in these things, that stuff is for the dedicated marine units.

-snip-

Plastic faceplate? Why? Obviously these guys are counter terror or something. Why even bother with something like that when you plan to be facing enemies armed with firearms? Soldiers in medieval times who were equipped with full helms had metal visors (you know, made of something that can actually protect their face if someone swings something at you) and it's not unheard of for even those soldiers to take the risk of fighting without them in order to have increased visual awareness. If your visors are made of plastic in a world full of guns, I suspect soldiers forced to take them along would either throw them away or fight with them raised anyways.


Suppressors are patently NOT something you just take all the time as a rule. They are a calculated choice based on the requirements of the mission. You can't just say they take this and that weapon all the time because real tactical units today don't do that. They pick their weapons based on what they anticipate. What advantage could there possibly be to forcing these men who are meant to be deployed anywhere to be totally inflexible in the equipment they use?


And ice picks...? Just no. It has none of the uses of a knife. Not only can a knife be used for things other than stabbing people, a knife can inflict more effective stabbing wounds because the blade is so wide. I get the strong sense that this is just a rule of cool thing and not a choice that actually has a coherent idea behind it.


Attachable neck plates are a thing in Marine Interceptor body armor (center) and AFAIK hardly anyone in combat uses them because the hard plates dig into your throat if you try to look straight down. If you're engaged in hand to hand, an enemy who you're wrestling with that deliberately pulls or pushes down on your head he can literally choke you out with your own armor. Unlike the ice pick this is actually something real soldiers are known to wear (though I haven't read any accounts of troops IN COMBAT who preferred to wear them) so don't consider this as strong an objection as the other points I've brought up.

For the plastic faceplate, remember this is modern reinforced plastic (even slightly sci-fi in how it is reinforced) not cheap crappy stuff. Your allusion between these and medieval visor helmets isn't really... suitable. The faceplates are designed to be a happy medium between protection and visibility (it doesn't really restrict the soldier's field of view much in the story), whereas medieval visors were mainly for protection and thus limited visibility. In addition, the faceplate is part of the suit, not a helmet. There are no attachable neck plates in front because the faceplate is thicker here and does the same purpose without the choking hazard mentioned in your last paragraph. The armor in the collar of the suit is in the collar, ie the bits that stick up around the sides and back of the neck.


RE: Suppressors: The soldiers have to be able to react to any situation or change in mission dynamics at any given moment. In a loud op where stealth doesn't matter, yeah sure your point is valid. But what if you don't know whether or not your next mission is going to be loud or stealth? What if you start loud then realise that you need some people to stealthily be somewhere else? Taking suppressors along is an overall plus for what little they weigh.


RE: Icepicks: It was a little bit influenced by rule-of-cool, but only a little. A knife has it's uses, but so does an icepick. An icepick has a smaller contact area, which means more penetration, not to mention the force amplification the handle gives (as a lever). An icepick can be used in more situations other than just climbing ice mountains; it can be used as a grapple, for example. Good luck trying to grapple onto something with a knife. Imagine a soldier skidding towards the edge of a roof, pulling out an icepick and hooking it around a railing, last second. Good luck doing that with a knife. I'm not saying knives are worse than icepicks in hand-to-hand combat, but in close-quarters, a pistol is just as effective as a knife. The icepicks are more for utility purposes. I know knives have utility purposes of their own, such as carving stuff. Yes when it comes down to it, a knife is a more effective weapon than an icepick, but icepicks aren't totally useless, and these soldiers pack two of them. The choice had a coherent idea behind it in that they have a pistol which can be used equally as effective as a knife if it comes down to it.


I summed up your issue with neckplates in paragraph #1.

I always assumed they were counter-knife stuff. Hence the plastic and the thin armor which wouldn't stop a proper bullet anyway.

Plus if you make them reflective then that has psychological bonuses, as well as a rule of cool thing, or a 'oh god i'm killing real people' reveal.

Yes and no. They wouldn't stop a .50 cal bullet, but they may just be able to save you from shrapnel from a frag grenade or maybe a glancing 9mm bullet.
I never planned on making them reflective; would ruin stealth.

[TheBiggerFish]

Maybe one icepick, one knife?