NS Military Worldbuilding Thread No. 12

[Husseinarti]

RPG-7 is tied with CG for being the best small unit projector.

Depends on whether you prefer rockets or rifles I guess.

Doesn't the RPG-7 suffer from being notoriously inaccurate beyond 2-300 yards? <.<

Nah thats a bit of a myth. They are effective out to 300~ meters but after that it does get kind of weird.

[Axis Nova]

It's more like it's kinda hard to hit a moving target with a manually aimed rocket from 300m away, rather than anything particularly wrong with the RPG itself.

[TPFII]

Aren't there more modern rocket systems that use venturis to spin-stabilize the rocket? I bet that'd help with hit probability.


If it were more practical and potentially advantageous to have racial segregation in the military, would that be what's likely to happen?

[Gallia-]

Doesn't the RPG-7 suffer from being notoriously inaccurate beyond 2-300 yards? <.<

Nah thats a bit of a myth. They are effective out to 300~ meters but after that it does get kind of weird.

The only "weird" thing is that the rocket tends to move into crosswinds, rather than against them, which probably contributes to Americans' inability to hit anything with it. Naturally, the Russians would say the same about M72 LAW being "weird" because it moves against crosswinds rather than into it. This is somewhat counter-intuitive for someone who has been trained extensively to compensate for wind in one particular direction and now has to do the exact opposite I suppose.

The other reason is video games because IDK gameplay.

Aren't there more modern rocket systems that use venturis to spin-stabilize the rocket?

PG-7 is already spin stabilized, obviously. The fins are right there. I'd imagine it's the direction of canting of the stabilizing fins that makes it move into the crosswind rather than against it. Presumably M72's fins are canted in the opposite direction, and so it moves in the opposite direction.

It's as accurate as a Carl Gustav or any other recoilless projector with practice.

[New Vihenia]

For more accuracy, perhaps one should add a laser seeker and turn the PG-7 into a rolling airframe missile.

[Gallia-]

It's much easier to literally just make an entirely new rocket using an inertial guidance.

PG-7 is neither optimal as a rocket nor a guided projectile. It's too small for a substantial motor, the warhead is relatively oversized as a result, and adding anything additional would just cause it not work period. The optimal projectile is closer to a uniform chode like FGM-172, which leaves plenty of room for propellant, a good warhead, and electronics necessary.

[Desena]

It's much easier to literally just make an entirely new rocket using an inertial guidance.

PG-7 is neither optimal as a rocket nor a guided projectile. It's too small for a substantial motor, the warhead is relatively oversized as a result, and adding anything additional would just cause it not work period. The optimal projectile is closer to a uniform chode like FGM-172, which leaves plenty of room for propellant, a good warhead, and electronics necessary.

Correct, I maintain the RPG-7 is probably the best overall MANPATS ever made, but the 40mm tub, simply cannot facilitate a larger motor or guidance. If you want to go into why 20 lb MANPATS are useful, that's different, but no, even the RPG-7V2 can't do that.

You can't get accurate without expanding the diameter of the tube, so you need a big boi like the sraw.

[Desena]

Also, mostly for the utility of hitting weak-armor but highly manufactured armor like that on the T-55 and making anti-soft target projectiles for MANPATS, which the RPG-7 model excels at.

[TPFII]

PG-7 is already spin stabilized, obviously. The fins are right there. I'd imagine it's the direction of canting of the stabilizing fins that makes it move into the crosswind rather than against it. Presumably M72's fins are canted in the opposite direction, and so it moves in the opposite direction.

It's as accurate as a Carl Gustav or any other recoilless projector with practice.

It's my understanding that the "problem" is caused by the fins having to be so large to make up for being hidden behind the warhead, and the COG of the rocket being in the warhead, the crosswind uses the fins on the rear as a fulcrum to push it into the wind. I don't understand how which direction the fins turn the rocket would have an affect on it's ability to buck a crosswind - it's not like crosswinds come from a guaranteed direction. Hence, if it's spun stabilized by venturis it shouldn't have that effect, or at least it'd be greatly reduced.

[Gallia-]

M72 LAW has the same basic layout, and likely weight distribution, as PG-7 and doesn't turn into crosswinds.

It's not a serious problem or anything, it just means that you have to account for the opposite effect of wind on the projectile. Neither M72 or PG-7 (or, for that matter, FFV551, which is rifling spin stabilized as opposed to fins) are terribly good at hitting targets past 300 meters, obviously, because I posted their Ph curves on the last page. Clearly, the issue is a lack of guidance on part of the projectile rather than anything inherent to their peculiar designs, since all three weapons have roughly equal Ph curves. PG-7 is actually more accurate at range than most of its competitors, with the possible exception of something like Folgore I guess.

Spin stabilizing with canted exhaust is a bit stupid, since you're just trading forward velocity for rotation, and all the projectors that do this might simply equal something like a CG or RPG-7. Fins are plainly the better solution, as evidenced by the fact that a minority of rocket projectors use canted exhausts, and those that do aren't appreciably more accurate at range than already existing weapons. And of course, by the time the most well known of those canted exhaust rockets appears, you already have a much better weapon also hanging around that completely nullifies it.

[TPFII]

The invention of disposable purpose-specific missile systems doesn't obsolete multipurpose and reusable rocket systems. Since the venturis would only need to initiate a spin it could be integrated into the booster, so I doubt it would be any less space-efficient than having to sacrifice space for the rocket motor like a folding fin assembly.

[Gallia-]

A "venturi" stabilized rocket would hit a moving tank about 20-25% of the time at a range of 300 meters. This is literally no better than anything else, except you have to make it, and it's easier to buy an RPG-7 or a Carl Gustaf. Lol. OTOH a guided missile will hit it 100% the time, unless it's physically stopped by an APS or the tank moves under or behind an obstacle. Making the round unguided doesn't solve this problem.

A spinning rocket motor might work if you're making a LAW in like 1960 or something, but the time for that sort of thing was a literal lifetime ago, so it doesn't really make sense for a modern weapon.

An inertially guided rocket is cheaper and far more effective. You can make the rocket motor smaller and the warhead bigger, for a given forward velocity, which makes the launcher lighter. Since it's a guided missile it doesn't need any sort of motor exhaust diversion to stabilize, you have fins instead that flip out and let it follow a path designated to the target by tracking the tank for a couple seconds. The only thing better for ensuring a hit on a target might be the very rare hypervelocity LAW OTOH those have a dead space of about 200-500 meters unless you like singeing your eyebrows.

Diverting the motor only makes sense if you can't somehow incorporate fins into the projectile such as very small caliber or short length weapons like grenades, nor make it spin stabilized through rifling, like a 40mm launcher. A rifle grenade, for example, which is the only place I'm aware of where they were actually used.

[TPFII]

And? IMHO, the primary appeal of the RPG-7 and similar systems is that they're not limited to HEAT rockets, and the ability to be reloaded is a fairly substantial benefit in and off itself. It's pretty silly to use a top-attack HEAT missile to thread through a window 73m out.

[Gallia-]

IMHO, the primary appeal of the RPG-7 and similar systems is that they're not limited to HEAT rockets, and the ability to be reloaded is a fairly substantial benefit in and off itself.

The primary appeal is that they're still cheap, there's lots of them floating around, and (most importantly) no one big has dropped money on replacements for them. When you're talking about using existing stockpiles of ordnance and weapons, rather than new manufacture classes of weapons, the former will win until someone bites the bullet and gets the latter. The fact that people are trying to make things like RPG and CG into shitty guided missiles proves the point, though.

There's no reason you can't make a reloadable guided missile. In fact, there's no reason it could be cheap, either.

It just wouldn't look anything like an RPG-7. Or a Carl Gustaf. These classes of weapons (unguided projectors) are being rendered obsolete as guided missiles become small enough, and cheap enough, to be carried in large quantities. There's no reason to have a heavy metal tube if you're firing guided missiles. The rocket takes the firing chamber with it, so you can save mass and carry more ammo. The Carl Gustaf is a heavy weapon, and so is the RPG-7 in reality, because they're both built to contain gunpowder explosions for their initial projectile launches. RPG-7 is a bit lighter because it's two stage but that's it. Something built more like Javelin can be a lot smaller than either. RPG-29, which is is substantially smaller in caliber and capability than FGM-148 (105mm vs 127mm), already weighs almost as much as the latter. Imagine how much a 127mm RPG-29 would weigh. Judging by the jump from RPG-27 (a 105mm disposable) to RPG-28 (a 125mm disposable), probably close to 30 kilograms ready-to-fire, or about the size of a Breda Folgore.

What's the difference between an RPG-7 team with a backpack of six PG-7VLs versus a Rafael Mini-Spike team with six Mini-Spikes? The answer is the Mini Spike team can probably kill two to three times more machine guns and snipers than the PG-7 team for approximately the same mass and bulk, and manpower consumption, so it's obviously cheaper.

We already have relatively cheap inertially guided weapons like Spike-SR that can easily replace something old and unguided like M72 LAW, LAW 80 or MATADOR. In fact, they often have in some smaller militaries, that are more capable of eating costs of new weapons because they have less of an argument to use stockpiled ordnance (namely that they have no stockpiles to draw from).

They'll probably stick around for a few more decades of course, and maybe longer in extremely poor militaries or countries, but modern armies will eventually replace them with new weapons which are cheaper and better.

Small but relatively well-funded armies like Singapore, Israel, and (arguably) the UK are sort of at the inflection point of replacing unguided projectors and disposables with smaller quantities of guided weapons, because it's cheaper to shoot one and be done, rather than sit behind some sandbags and spend four or five times as long (maybe a minute) lobbing two or three shells of comparable size for the same effect. You've made your single Carl Gustaf team into something akin to two or three Carl Gustaf teams by buying a rocket that costs $50,000 instead of a 84mm shell that costs $2,500. Congratulations, you've saved money.

[Axis Nova]

The RPG-7 is a classical example of 'good enough'. It won't penetrate modern main battle tanks head on, but the again neither will most other light anti armor systems. It's still plenty good against lighter vehicles and has found some success as a support weapon as well.

Also, y'know, statistically, it hasn't performed any worse than the M72 LAW, it's closest competitor.

[Gallia-]

If you shoot a rocket and miss the rest of the squad decimatios you with soap bars in socks I guess.

[Miku the Based]

Try aiming a 30 pound tube with a laser in it at a 40 inch target 300 yards away. It's mainly that problem.
The next problem is this, 10 mph full value wind at 300 yards moves a 308 2 moa or 6 inches, a slow moving explosive projectile under the same conditions move 14 MOA which is 42 inches. Would miss the target if aim dead center, a target double the size would barely hit which is most Humvees. That's just a 10 mile full value wind.
Slap it to a mount (on a vehicle or something) and give it guided properties and it will increase the effective range dramatically.

[Triplebaconation]

TPFII isn't taking all aerodynamic forces into account. Getting rid of the fins would most likely increase susceptibility to crosswinds.

The obvious way to simply improve RPG hit probability is to increase velocity.

[Gallia-]

He also forgets canted exhaust reduces forward velocity, regardless if separate motors (parasitic mass) or actually diverted.

MBT-LAW has the best aspects: high speed and guidance.

Folgore is second best: high speed. Twice as fast as PG-7, which is already quite zippy.

[Miku the Based]

Just checked the stats MBT-law is three times as slow and Folgore is three times faster.

[Triplebaconation]

Wikipedia

[TPFII]

TPFII isn't taking all aerodynamic forces into account. Getting rid of the fins would most likely increase susceptibility to crosswinds.

Not to disagree, but would you mind explaining which forces that I'm not taking into account? Without relevant information it's rather difficult to research the matter and gain knowledge on the subject.

canted exhaust reduces forward velocity, regardless if separate motors (parasitic mass) or actually diverted.

I've already asserted that the wasted space could be comparable in space to a folding fin assembly, so in which manner does it reduced forward velocity? I would assume that the nozzles could be placed inside the slipstream of the warhead, so I don't see it as all that different from the rocket motor utilizing a fin assembly, and the associated drag, to spin the projectile.

[Gallia-]

Just checked the stats MBT-law is three times as slow and Folgore is three times faster.

Sad!

Good thing it compensates automatically for its entire maximum flight speed of "about two seconds".

I've already asserted that the wasted space could be comparable in space to a folding fin assembly,

It wouldn't be. PG-7V has a pretty good set of fins that don't seem to do much for it.

so I don't see it as all that different from the rocket motor utilizing a fin assembly, and the associated drag, to spin the projectile.

PG-7V is not harmed by its fins in flight, they do not produce very much drag, and they are quite efficient at what they do.

Of course this is obvious by looking at how PG-7 flies: It flies into the crosswind. This means it has a higher thrust motor that substantially overcomes what little drag the fins produce. Relatively draggier projectiles, like the spin stabilized 84mm FFV551, M72 LAW's various rockets, or 140mm Brunswick RAW, will move downwind of a crosswind. They are inherently draggier projectiles, with weaker rocket motors (or none at all), thus they move against crosswinds.

(...) The net drag force (drag minus rocket thrust) will then have a component at right angles to the projectile velocity. In the absence of rocket thrust, or if drag exceeds thrust, the projectile will acquire a downwind lateral velocity and displacement; if thrust exceeds drag, the projectile will move upwind. (...)

As PG-7V moves upwind, the projectile hardly suffers from its fins, if it notices them at all. That said the only real way to reduce crosswind error is to make the projectile heavier or faster. Preferably both.

Breda Folgore achieves, being about twice as fast and twice as heavy as a PG-7V in flight, but it's also more comparable to SPG-9 than RPG-7, so it's not a terribly fair comparison. Incidentally, Folgore also uses fins.

As I said before, using rotational reaction motors to achieve spin stabilization is usually only done if you cannot fit fins onto a projectile (i.e. it is small) and cannot use a rifled barrel to stabilize it. This more or less relegates it to the realm of rifle grenades, barring some ingenious new weapon form, such as a rocket assisted PIAT or Blacker Bombard.

[Austria-Bohemia-Hungary]

Just checked the stats MBT-law is three times as slow and Folgore is three times faster.

Sad!

Good thing it compensates automatically for its entire maximum flight speed of "about two seconds".

He thinks 40 m/s is the max speed.

[Miku the Based]

Rather have a fast moving explosive projectile that would not call victim to countermeasures like the trophy system than a slow moving projectile slow enough that it's possible a tank could identify location of user from the massive backblast and respond.
My mistake, the bofors missile manage to speed up twice the speed of rpg and the Italian one I'm correct on according to wikipedia. Both have the same max range so flight time does not matter in extending max range. I can see the purpose of limiting flight range to prevent collateral damage, detonate warhead so it can't be reused. But that makes everything overly specialized and one can't hit a aircraft with that range. Rather have a fast moving multipurpose explosive projectile with limited guidance with a setting to extend the some arbitrary range like 40km to really deal with all the threats and simplify logistics. Maybe two different missiles (one for air and one for ground) for the same rifle or tube but that's it. No need to set fancy targeting parameters, just aim at least 60 MOA or less and the thing will guide the rest of the way through some sort of guidance system at the speed of a small arms rifle or something. Also inexpensive, the other two missile platforms discussed are too highly specialized to really field wide use.
Would pistol rounds or crossbows fool anti-missile countermeasure system like the trophy system into thinking it's a rocket?