Blast It

I should've realized that you can't necessarily fit all the explosive inside the grenade. 30 grams of ONC has a volume of 14,563.11 cubic millimeters, whereas the "based on shotgun slug" grenade-design I was using only has a volume of 5,282.41 cubic millimeters—the HEDP round would need to be 2.76 times the volume of the slug. The 20.71 grams of ONC for the air-burst one, meanwhile, has a volume of 10,053.4 cubic millimeters, a volume 1.9 times that of the slug.

All is not lost; a polymer-cased grenade is presumably much less dense than a slug. (I find, incidentally, that the slug in question, given its mass and volume, has roughly the density of thulium, 9.33 g/cm3. It's also the density of the molybdenum-alloy "mandrels" used for piercing stainless steel tubes, so, maybe they're made of that, for improved armor-piercing characteristics?) If we wanted to make the HEDP round work the same, it just has to be 62.83 millimeters long, or about as long as a modern 3" shotgun shell (remember, shotgun shells' actual length is about half an inch shorter than their listed length); the air-burst round has to be 43.25 millimeters long, or about as long as a 2.25" shell.

One thing this probably means is that, while they can load tubular magazines with any combination of shot, slugs, and grenades they feel like, they have to load box magazines with all the same thing. (Actually if the 1.75" Aguila "minishell" is any indication, they may have to load their tube-magazines with all one thing too, or else have some mechanism to vary the "size" of the motion in the feed mechanism. Apparently the minishells have feeding problems in many guns.)

Les armes à feu spéculatives 3

Thoughts on SFional guns.
  • Recently had occasion to design my setting's .50 BMG equivalent. .50 BMG is actually exactly 13 millimeters, I don't know where that "12.7×99mm NATO" business comes from. The bullets are typically a full 60 millimeters long. Now, to move a 49-gram bullet at 860 m/s requires 14.515 grams of nitrocellulose propellant, so it'd take 6.096 grams of octanitrocubane. 6.096 grams of ONC (density 2.06 g/cm3) has a volume of 2959.369 cubic millimeters.

    Going with the base-area of the .50 BMG, which has a case-diameter of 20.4 millimeters, resulted in a somewhat gawky final product (the propellant "casing" went less than halfway up the bullet). So instead we're gonna go with the shoulder diameter, 18.1 millimeters. Now we just say that the cylindrical volume of a cylinder of that base-area, height undefined, minus the volume of the bullet, equals the volume of the propellant. Then we add the volume of the bullet and propellant, divide by the case area, and get a height for the "casing" (actually the propellant) of 42.45 millimeters. The "casing" sticks out 2.55 millimeters around the bullet (and out from behind it), and goes 39.9 millimeters up the side.

    Hence, I guess, my Peacekeepers' sniper-round is "13×43". With an overall length of 62.55 millimeters, and a total cartridge-weight of 55.1 grams, it's a lot lighter than a round of .50 BMG, which weighs 116.8 grams. That means that your sniper can carry a lot more ammo—over twice as much. Currently, .50 BMG snipers usually carry 50-100 rounds, which weighs 5.84-11.68 kilos; 100 rounds of the caseless only weighs 5.51 kilos.
  • Apparently, I was wrong, octanitrocubane would not smell like camphor. It's in the same family of explosives as RDX and HMX; the former is what's in C4. Commercial C4 has "odorizing", "taggant" additives put in to make bombs made of the stuff harder to hide (I don't think the military bothers)—the main "taggant" in the US is apparently very noticeable to dogs, I don't know how noticeable humans find it. But apparently, on its own, it smells "bituminous", i.e. tarry. Personally I like that smell, like fresh asphalt, but I'm apparently in a minority on that one.

    Also, I must be more careful about specifying it's denatured octanitrocubane. ONC, see, is a high explosive; firearm propellants are low explosives—they deflagrate (burn) rather than detonating (kablooie). But, when Heckler and Koch were making the G11's caseless ammo, they (in order to solve "cooking off" issues) used a propellant consisting mostly of RDX, denatured so it would burn slowly enough to propel ammunition—and not explode in the user's hand. (The reason they went with RDX is it's harder to ignite than nitrocellulose is, hence it solved the "cooking off" problem caused by no longer having the ejection of spent casings for a heat-sink.)
  • Recalculating, I find I can, in fact, have my 12-gauge round be caseless. Went with twenty pellets of #3 buckshot, the same as was used in the M576 buckshot-grenade for the old M79 grenade launcher—which isn't really a grenade, it's literally a shotgun shell you shoot from a grenade launcher. But I decided to make the pellets out of the same tungsten alloy as those found in the QBS-09; taking their diameter of 5.3 millimeters and their mass of 1.4 grams, we get a density of 17.96 g/cm3, which makes #3 buckshot (diameter 6.4 millimeters) weigh 2.465 grams—twenty of them mass 49.3038 grams. I'll come back to that.

    Decided to make the propellant straight nitrocellulose, not denatured ONC, for this one: we want the propellant to take up room. The loading tables for a 49-gram load say it takes 2.0088 grams of powder; that, in nitrocellulose (density 1.40 g/cm3) has a volume of 1434.857 cubic millimeters. Now, the closest you can pack spheres still results in wasted space—the maximum efficiency of packing equal spheres is 74.048%. Twenty pellets of #3 buck has a volume of 2745.166 cubic millimeters; in effect, though, it has a volume of 3707.279 cubic millimeters, wasting 962.113 cubic millimeters. We just have to fill that in, though, with our propellant. The remaining 472.744 cubic millimeters? We divide that up among the twenty pellets, solve the resulting volume for its radius, and come up with a coating .17 millimeters thick. Interestingly, #3 buckshot with that coating exactly comes to the edge of a 20-millimeter diameter circle when you pack it hexagonally, as if this arrangement were fore-ordained.

    You stack your twenty pellets in one layer of seven, one layer of three, one layer of seven, one layer of three. I checked, it fits. This arrangement results in a round 24.29 millimeters long, and, again, 20 millimeters in diameter; the remaining volume around the pellets and propellant is presumably filled up by some kind of flammable filler—"liquid wadding"?—to make up the rest of the cylinder. (I envision it being a clear, resinous-looking substance, I'm not sure why except that it'd look awesome.)
  • Now, it turns out I miscalculated before, on the number of rounds a shotgun can hold; shotgun-shell lengths are apparently the length of the casing before being crimped down (or after firing), and are about half an inch longer than the actual length of the round. So 2.75" shells are really 2.25 inches long; a QBS-09's magazine is 28.575 centimeters long, the Benelli M4 and Remington 870's magazines are 40.005 centimeters, and the Mossberg 590's magazine is 45.72 centimeters. That means the QBS-09 can hold eleven rounds (nearly twelve—its 24th-century equivalent probably the full dozen) of our caseless 12-gauge round, the Benelli and Remington can hold sixteen, and the Mossberg can hold eighteen (nearly nineteen—the full nineteen, again assuming a generous future).
  • A shotgun slug with a weight of 49 grams isn't all that unusual, though that's kinda a big one (1.75 ounce). But it requires the same amount of nitrocellulose the buckshot does; with this one, we can go with ONC. I find a typical 12-gauge slug is about 17.65 millimeters in diameter and 21.59 millimeters long. That requires (2.0088/2.38=)843.696 milligrams of ONC, which has a volume of 409.561 cubic millimeters. Treating the slug as a cylinder, we find that the denatured-ONC propellant "casing" sticks out from it 1.175 millimeters, and goes 16.94 millimeters up the side of the slug. That brings its total length to 22.765 millimeters, meaning it pretty much fills out shotgun magazines the same way its buckshot counterpart does (you could carry one extra in a Benelli, Remington, or Mossberg).

    Presumably the shotgun grenades would have the same mass as the slug, and the same amount of propellant. There's basically no easily available information on the 20 mm kind, but I find that an "air burst" 40 mm grenade contains 32 grams of OCTOL (air-burst seems to be the main thing the OICW would've been used for—same seems to go for the less-experimental, or at least less canceled, Daewoo K11 and Chinese ZH-05). Now, ONC (not denatured this time) is six-elevenths more effective than OCTOL, so to get the same explosive yield requires only 20.71 grams; the rest is the casing and fuze. The armor-piercing type of 40 millimeter grenade requires 45 grams of Composition A; ONC is 48.75% more efficient than Composition A, meaning it'd take a full 30 grams to make an AP grenade (presumably they can miniaturize the fuze and make an ultra-light casing, it's the 24th freaking century).
  • Do you remember my coil vulcans? They use the "gatling" mechanism to reduce wear on the coils. Well, it occurred to me, the likely ammunition for that gun, whether vehicle-mounted or carried by powered-armor troopers, is something like the Raufoss Mk. 211 High Explosive Incendiary Armor Piercing round, which uses a steel core and a tiny amount of RDX to accomplish, in a .50 BMG round, effects you usually need 20 mm to achieve. Of course, being a coil-gun round, some of it's going to be different—it'd probably have at least a small amount of exposed iron, for instance (maybe a "driving band" like on artillery shells?).

    Average troops equipped with lifting exosuits could use it with a tripod, maybe, though I don't know of anyone who's used the GAU-19 (chambered in .50 BMG) that way—and the Soviet Yak-B machinegun is only used on the Hind. You would need powered-armor troopers to use the thing without a tripod; the recoil of the GAU-19 is 2.2 kilonewtons at 1,300 rounds per minute, but goes down to 1.7 at 1,000 rds/min and up to 2.8 at 2,000. It takes about 2.7 kilonewtons to knock over a 113-kilo man (a basketball player, specifically, in what's basically a horse-stance); therefore, it takes only 1.7 kilonewtons to knock over a 70-kilo man in the same posture (not that you stand like that while shooting a machinegun). Presumably for handheld, or even mere tripod applications, you'd keep the rate of fire at 1,000 rds/min.

    A thousand Raufoss-equivalent rounds would weigh 43 kilos; each link of a disintegrating belt weighs about 2 grams, a thousand of which is another 2 kilos, bringing the total to an even 45. The GAU-19/B weighs 48 kilos, so you really want that power-lifting exosuit—which may also be necessary to using the thing by hand, I wouldn't be surprised if the reason nobody uses .50 BMG tripod guns now is the sheer difficulty of pointing the thing. (By going with titanium instead of steel, the links could weigh as little as 1.1 kilos; and if we use polymer like the LSAT—which you may have to, with caseless—1,000 links weighs only 500 grams.)
  • One thing I realized, since my setting's "assault rifle" is chambered in something that approximates .30-06: they don't need much special equipment to be a "designated marksman". So, in my setting, there is no DMR; they just attach a bipod and scope to the standard assault rifle via its accessory-rail.

    Since it's a bullpup AK-type assault rifle, I guess it looks like the Polish Jantar carbine (prototype/demonstrator). Or, even more, like the Kalashnikov Concern AS-1 and AS-2, of which there seems to be, more or less, one image on the whole internet. (Your guess is as good as mine why they're green.)

    While I'm at it, the bullpup ARs my USMC uses, are basically like this, the K&M Arms modernized Bushmaster.
  • The main underbarrel grenade-launcher used in my setting is also a shotgun, like a cross between the M26 Modular Accessory Shotgun System and the M576 buckshot grenade in reverse.

    It occurred to me that my Peacekeepers would classify all their shotguns as grenade-launchers—because it's no longer the least bit remarkable that they can be used for 20 millimeter grenades. It's not that uncommon to classify things oddly, in militaries; several Russian shotguns are designated as carbines, and not all of them have rifled barrels like the KS-23. Or how about the US's pathological aversion to the words "light tank"?

    I'm not sure how prevalent 40 millimeter grenades are, for my Peacekeepers, though zledo use their equivalent here and there. I suppose the humans probably prefer the 20 millimeter ones for the high end of "small arms", and use the 40 millimeter grenades for their equivalent of the Mk. 19 grenade machinegun (and its successors).


Sierra Foxtrot 6

SF thoughts.
  • Turns out I was apparently overestimating the collective mass of the human species. Our average mass, including children, is 50 kilograms. Since a hefty proportion of our population is not full-grown, we actually mass more like 350 billion kilos. The Earth, for comparison, masses 6 septillion kilos. (Or, humanity as a whole masses 350 teragrams, but the Earth masses 6 yottagrams...meaning the Earth is 17,142,857,100 times the mass of all of humanity.)

    Remember that next time a Watermelon Green waxes overwrought about this "tiny" planet. Also, the mass of the Earth's atmosphere is 5 quintillion kilos, i.e. 5 zettagrams. That's relevant not only to discussions of climate, but also (and in my estimation more importantly) to discussions of whether terraforming by any society that we'd recognize as ours (and still recognize as such when it finishes) is good science fiction or rank nonsense.
  • There are two shows on Syfy right now that involve space-travel—I know, I'm scared too. One, Killjoys, is fair-to-middlin'; the other, Dark Matter, is (so far) genuinely good.

    Killjoys' problem is its bad worldbuilding, basically. You wouldn't be mining in person in that kind of setting, certainly not for yttrium—yttrium being one of those metals it's a lot easier to get from asteroids, when you have the option, and putting boots on an asteroid is a waste of money. Likewise you wouldn't be harvesting crops with migrant farm-workers, certainly not outdoors (indoor farming is a lot more efficient, both in terms of land-use and in terms of crop yield—you grow the crops under magenta light).

    We haven't seen as much of Dark Matter's worldbuilding, but that's a good thing: they reveal their setting gradually, and the characters' amnesia justifies their being as in-the-dark as we are. Dark Matter also has a much more likable cast of characters and a more livable setting, since, unlike Killjoys, it's not composed entirely of bad dystopia clichés (piled up without regard for whether they make a lick of sense).
  • I wonder if people are going to think that the fact zledo call the space-fold drive "the light-speed bridge" is a Transformers reference, i.e. to the space-bridges. It's not; I had been only very casually a fan of Transformers when I decided that's what they call it (if "those are kinda cool but I can name exactly three of them" counts as even "very casual" fandom).

    No, actually, zledo calling their FTL "light-speed bridge" is a reference to Hilaire Belloc's essay "On Bridges". Specifically, to this part:
    A bridge is a violation of the will of nature and a challenge. "You desired me not to cross," says man to the River God, "but I will." And he does so: not easily. The god had never objected to him that he should swim and wet himself. Nay, when he was swimming the god could drown him at will, but to bridge the stream, nay, to insult it, to leap over it, that was man all over; in a way he knows ... that all that he dreads is his inferior, for only that which he reveres and loves can properly claim his allegiance. Nor does he in the long run pay that allegiance save to holiness, or in a lesser way to valour and to worth.
    In the same way, the zledo regard their FTL drives as "a violation of the will of nature and a challenge", except that they don't have the concept of "nature" in our sense of "happens on its own". But they do regard the FTL tech as a defiance of mere brute creation, something proper to man.
  • Another show that's out this season is Humans, or rather HUM∀NS (which I prefer to pronounce "Hum-for-all-n̩s"). It's kinda...not good. Actually it's terrible. The thing is a bunch of paint-by-numbers Transhumanist clichés, and none of the characters except William Hurt's (because he's never bad no matter what he's in) is worth a damn. Neither of the parents of the main family seems to mind, or even think it notable, that their kids will not so much as get up to answer a phone; later, when the dad leaves the room so his wife can talk to their daughter, the wife leaves too!

    And, seriously, you can't just skim the Wikipedia article on Transhumanism, throw the appropriate buzzwords into your dialogue, and call it a day. Give us an actually original take on the idea of AI, or don't waste the money on a show about it. Of course, this show doesn't actually waste any money on anything, because it is set, in all regards, in the contemporary UK. It's apparently set in 2046, i.e. 31 years in the future, but all their material culture looks just like that now. Because nothing will change in 31 years—everything we have now looks exactly as it did in 1984, right?

    Also, come on, 2046? You think we'll have androids that can pass for humans in good light by then, or anyone actually wanting to use them for anything except a novelty? We might just maybe kinda sorta have some specialized applications of robots in some very few things; we might make much more use of automation in countries where the demographic collapse has been particularly harsh. But nobody who understands the problems with the TinmanTypist trope should expect much of that to involve androids, and nobody who plays many video games should be particularly sanguine about the reliability of any androids we do use. (I'll leave to one side the absurdity of anyone making self-aware androids—ever, let alone in 31 years.)
  • Supposedly, a tiger can hear a human heartbeat from twenty to thirty meters away. Now, if tigers' ears are as much better than human ears as cats' ears are—five times as good—then that's probably not right, given you can't hear a heartbeat from four to six meters away, but there is more to the story than brute acuity. Cats, and tigers, being solitary predators, are much better at picking certain sounds out from ambient noise.

    Another thing they can do is pinpoint a sound to within five degrees, which comes to eight centimeters a meter off—and 2.19 meters, at the aforementioned twenty-five meters (on average) that they can hear your heartbeat from. So, basically, though a tiger can't find you by scent (there's a saying somewhere in Southeast Asia, I forget where specifically, "If the tiger had to find food by his nose, he would starve"), it can find you very quickly by its ears.
  • One of the anime out this season, Classroom Crisis, about a voc-tech high school owned by a rocket company (on Mars) that's getting restructured by its parent corporation, was all right for the first two episodes, but then it filled me with rage. You ever hear of the "leftist sucker-punch", where something ideological sneaks into a work that's mostly irrelevant to politics? (The sucker-punch is also found in right-wingers—*cough*Terry Goodkind*cough*—but it was named by a conservative, I think John Nolte.)

    Well this show had an "idiot sucker punch". The accountant working for the corporate-shark type who's restructuring them gives their factory to the space-car division, then tells them they have to use the garage where their type of rocket was invented—which has been a museum for the last several decades—instead. And they sit there and take it!

    No, sorry. What would really happen would be the rocket-engineer/teacher would turn to her and say, "I'm sorry, what level math did your degree require again? Do you understand that none of this equipment has been used in decades, and to re-attach the utilities, and then run diagnostics, repairs, and replacements on the equipment—to say nothing of the lost time becoming familiar with decades-outdated equipment and the software it runs on—will cost as much as our old facility? To say nothing of whether you can even use this garbage to make contemporary rockets."

    It's basically this Dilbert strip. The reason I call it an "idiot sucker punch" is, it's obviously driven by consideration of "what will advance the plot", rather than "what makes sense" or "what is not an expression of open contempt for our audience". That's just as bad of work as that produced by inserting ideology, although it's probably less morally reprehensible.
  • The thing (well, one of the things) people forget when they generalize from chimps and bonobos to humans, is that our last common ancestor with that genus (Pan) lived 5 million years ago.

    5 million years ago, there weren't any mammoths or mastodons. Yet. I.e., entire lineages of elephant came into being and went extinct in the time separating Homo from Pan.
  • A 12-gauge cartridge is 20 millimeters in diameter. A 12-gauge slug, of course, is 18.53 millimeters in diameter—the diameter of a sphere of pure lead that will mass 1/12 of a pound—but, for purposes of military SF, the diameter of the cartridge is more useful (not least since it's a nice round number). So, the upshot? In my setting, 12-gauge is called "20 millimeter". I think the shotgun shells won't be caseless, but made of a material that is entirely burned up and expelled when the round is fired, something like the paper cartridges you'd see in the early 19th century.

    It's apparently quite common to use 2.75-inch-long rounds in military shotguns; that seems to be, for instance, what the QBS-09 semi-automatic shotgun uses, as do the US's military-issue Benelli M4s, Mossberg 590A1s, and Remingtom 870s. I don't know that you'd need quite that much room, given you need 42% as much octanitrocubane propellant to get the same performance you get from nitrocellulose propellant, but the biggest factor in how much space a 12-gauge round requires is the nine pellets of 00 buckshot. Packing the pellets as closely as possible—in triangles, not seven-sphere hexagons—apparently means a height of 22.5 millimeters, or just under one inch. The higher-powered loads of 12-gauge 00-buck seem to use about 2.46 grams of (nitrocellulose) powder, which is 1.03 grams of ONC; given ONC's optimal density of 2.06 grams per cubic centimeter, you're looking at exactly 500 cubic millimeters, which, at a diameter of 20 millimeters, is a disc 1.59 millimeters thick. If the pellets simply sit on top of the ONC "powder", you wind up with a shot-shell with a minimum length of 24.09 millimeters. Assume another, say, 14 millimeters, of wad, to bring the whole thing to an inch and a half long—38.1 millimeters.

    The QBS-09 has a magazine with a capacity of five rounds of 2.75-inch; the Benelli M4 and Remington 870 go up to seven rounds, while the Mossberg 590 can do eight. That is to say, the QBS-09 has an effective magazine capacity of 34.925 centimeters, the Benelli M4 and Remington 870 both have an effective capacity of 48.895 centimeters, and the Mossberg 590 has a capacity of 55.88 cm. If the rounds for those shotguns were only 3.81 centimeters long, then the QBS-09 could hold nine rounds, the Benelli and Remington could hold twelve, and the Mossberg could hold fourteen.