Weapon design - how much can you lighten an artillery barrel?

[Anthony]

Originally Posted by malloyd

Presumably by the ratio of the tensile strengths per unit weight.

Well, tensile strength, heat capacity, hardness, shock resistance, etc. Not to mention other problems -- for example, the graphene mentioned before is flammable, which would be unfortunate if you wanted to fire the gun more than once.

[Nereidalbel]

Originally Posted by Anthony

Well, tensile strength, heat capacity, hardness, shock resistance, etc. Not to mention other problems -- for example, the graphene mentioned before is flammable, which would be unfortunate if you wanted to fire the gun more than once.

And yet, graphene nanosheets actually reduce the flammability of other composites.

[Peter Knutsen]

Originally Posted by Anthony

The big problem is that there isn't much you can do to make the ammunition lighter (and if you only want a small ammunition capacity, just use a missile launcher).

I'm under the impression that missile-type ammunition is much more expensive than grenade-type ammunition.

[doulos05]

Originally Posted by Peter Knutsen

I'm under the impression that missile-type ammunition is much more expensive than grenade-type ammunition.

It is, but lightness was the stated objective, not cheapness. And a missile launcher certainly has the possibility to be much lighter than tube artillery because you can impart energy well after the round leaves the tube. If tube weight is a significant issue, you could use a simple starter motor to propel it clear and have a super-light tube (a la every man-portable anti-tank or air defense missile known to man).

That said, I can't see that being the case because while you can save tons of weight on the tube, your round weight goes up considerably.

[Anthony]

Originally Posted by Peter Knutsen

I'm under the impression that missile-type ammunition is much more expensive than grenade-type ammunition.

It's more expensive per round, but the launcher is much lighter and cheaper, so if you only want a small number of shots, it tends to be a better option.

Originally Posted by doulos05

That said, I can't see that being the case because while you can save tons of weight on the tube, your round weight goes up considerably.

Not really. Recoilless rifle ammo is already pretty heavy because of the needs of being recoilless. The BGM-71 TOW has a pretty similar ratio of warhead weight to launch weight, and has a substantially lighter launcher.

[BraselC5048]

Originally Posted by doulos05

Assuming a wet-water navy model, it would be very odd to have fewer escorts than you have capital ships. That's for 2 reasons. 1) Escorts are meant to maintain separation between the capital ships and the enemy. In order to do that, you have to spread a web of escorts out in all directions from the capital ships. 2) You use escorts of missions smaller than capital ship missions. You don't need to send a battleship to escort a merchant convey to protect it against pirates. You probably don't need to send a battleship to "show the flag" at a planet that's threatening to rebel. You use destroyers and frigates (maybe cruisers) for that.

You're right about that. I never established how many ships are in a fleet screen, but it doesn't really vary with the number of battleships in the fleet. There's scouting to consider too. Some of those ships will be cruisers, to provide more firepower to back things up. Likely 200 destroyers. Frigates suffer badly from being at the bottom of the food chain, and aren't really intended to fight military vessels. I suppose you could use them in a fleet screen to make up numbers, same with scouting, but their main work is fighting those annoying corsairs, which a frigate can easily beat. Cruisers are intended for independent operations, and have significantly more staying power than a destroyer or frigate, having multiple drives so they aren't crippled by a lucky hit.

(humm, perhaps see what a design for a destroyer using multiple drives would look like? The penalties for going to a greater number of smaller drives at the high end is massive, easily 50% plus in tonnage. On the other hand, the jump drive is liner with power up to exactly the point of what a destroyer has, so it might be next to no penalty at all for those. Would make a ship much better suited for independent operations.)

(Destroyers are twice the size of frigates, with about 2.5 times the firepower and thicker armor, and a typical cruiser is 2.5 times the size of a destroyer, with 3.5 times the firepower, and armor that's thicker still. Point defense also goes up with size, so size and firepower differences tend to get magnified. A frigate lacks heavy lasers and will do almost no damage to a cruiser, since it will get very few missiles through, if any at all, while a cruiser will get nearly all of them through, having 5 times the amount of point defense.)

Originally Posted by doulos05

Wait, so are these mounted on the ships or held in the armory to loan out to marine detachments requiring additional firepower?



But if they're deployed from the ship armory, you might have a higher loss rate because you could lose one dirtside. Though I'll grant you that it wouldn't be much more.

From the ship's armory, although it doesn't have a dedicated one, rather it's in the storerooms with the rest of the gear (still 75% weapons, though). I haven't actually used them in a landing party yet, but I have used them twice firing out the airlock into the enemy ship's airlock built-in MG position (pirate), or through the blasted out doors of an oversized cargo airlock to knock out MG positions in the cargo bay, in both cases prior to boarding. The HE round is a full power 105mm shell, the AP round is intended to punch through an unarmored bulkhead before exploding (no armor divisor instead of .5, but less destructive power), and the HEAT round is for use against tanks on a planet (may/may not go through starship armor, depending on thickness, but pointless effects on the the other side, so don't bother.

Originally Posted by malloyd

Presumably by the ratio of the tensile strengths per unit weight. Steel alloys are actually pretty good at that, which is after all why we use them. Some expensive steel alloys and treatment processes will get you a factor of 1.5 over more typical alloys ones, but that's probably about all you can hope for, especially under the rather harsh conditions of the interior of a gun barrel. There are alloys that *claim* to outperform the best high nickel steels but numbers are usually not forthcoming to back those claims up. Though I suppose when you have more nickel than iron, and some of them do, it's not technically steel anymore.

On a more theoretical level, for actual materials you can obtain in multi-gram quantities, you can beat steel strength to weight by a factor of 8 or 10, though the best values are for fibers, which probably mean you need to embed them in something to make them into a gun barrel. The best theoretical materials, like those carbon nanotubes or graphine sheets will claim factors of up to about 200, but I strongly doubt if anybody ever manufactures bulk samples they will be anywhere near that good. It's actually a general characteristic of materials that tiny whiskers are an order of magnitude stronger than anything you can get in bulk, simply because they are too small to have scratches or other flaws.

Thanks for the numbers. The one it's based on is 260? lbs for the barrel with a .50 cal spotting rifle. Making it .30 cal and detachable, dividing by 1.6 and fudging the numbers a little winds up with a 125 lb barrel, an 80 lb tripod, and a 25? ish lb spotting rifle to move. I don't know how portable a 125 lb object (or a 150 lb object staying fairer) is on the battlefield, compared to a 90 lb .50 cal MG. Likely a 2+ person load.

It also has an optional lightweight gun shield, made out of body armor type materials on a lightweight frame, which I discovered the hard way is not, in fact, proof against (AP?) .50 cal fire, although propping up spare hull plates behind it meant it either failed or just barely did penetrate the crew's body armor. I had fired a heavy missile with a 4 ton yield HE warhead into the (depressurized) cargo bay right after the doors were opened, but apparently the heavy MG's were set up on the side, not the middle has expected.

[scc]

If we're talking about marines on a spaceship, mortars and missile launchers are more the sort of things they'll use as support weapons, remember marines will need mobility, they won't have vehicles to tow stuff

[doulos05]

Originally Posted by scc

If we're talking about marines on a spaceship, mortars and missile launchers are more the sort of things they'll use as support weapons, remember marines will need mobility, they won't have vehicles to tow stuff

That's true. Marines are going to favor man-portable weapons and call for close air support or ortillery if things get hairy. A recoilless rifle definitely is a marine weapon... when mounted on a vehicle. But not so much when they've got to carry it by hand.

Since they're already written into your game, the easiest way to lighten them might be to use grav harnesses to counteract some of the weight.

[Langy]

Originally Posted by doulos05

That's true. Marines are going to favor man-portable weapons and call for close air support or ortillery if things get hairy. A recoilless rifle definitely is a marine weapon... when mounted on a vehicle. But not so much when they've got to carry it by hand.

Since they're already written into your game, the easiest way to lighten them might be to use grav harnesses to counteract some of the weight.

Or to make the people carrying them wear power armor, thus not lightening the actual weapon but making it man-portable anyways.

[BraselC5048]

Originally Posted by scc

If we're talking about marines on a spaceship, mortars and missile launchers are more the sort of things they'll use as support weapons, remember marines will need mobility, they won't have vehicles to tow stuff

A heavy cruiser also has 3 81mm mortars on board. They're pretty much identical to every other 81mm mortar ever made. A battleship also has a single pack howitzer on board. Since battleships don't really operate on their own, collectively they can field an artillery battery, manned by marines who never really got much training on that, and are likely not all that great at it.

Originally Posted by doulos05

That's true. Marines are going to favor man-portable weapons and call for close air support or ortillery if things get hairy. A recoilless rifle definitely is a marine weapon... when mounted on a vehicle. But not so much when they've got to carry it by hand.

Since they're already written into your game, the easiest way to lighten them might be to use grav harnesses to counteract some of the weight.

It's wroth pointing out there's two (or three) different scales and kinds of forces we're dealing with. A single cruiser can field a platoon of marines. None of the heavy support weapons have dedicated crews, rather their crewmen are drawn from the same manpower pool. They can also field maybe 100 spacers, but that robs them of the ability to fight any major battle. Any land use of the marines would likely be of very short duration, a raid or some such. They won't need extensive transportation, since normally they won't be moving far. After all, a cruiser has 5 boats which spaceships in their own right, anti-grav, capable of going from Earth to Jupiter in a few days, and 250 knots in an Earth-standard atmosphere. They're what you'd normally use to land the landing party, and as such you can pick pretty much any point on the planet you want. Battleships operate nominally in squadrons of 5, which are grouped to form fleets, although in practice it varies widely. Generally 10-20 battleships in a modest sized fleet. Each battleship has a company of marines, so a fleet can form quite a large army on short notice, but of course it will have to be disbanded and re-embared pretty quickly too.

Then there's the elements of the 2 marine divisions scattered about as garrisons. They have air support and tanks, at least a few of them. They also need chartering a cargo ship (or two) to get them to their destination. They would also have jeeps for these guns.

140 lb barrel, 80 lb tripod, heavy, perhaps a handcart to set them on for easier transport? It also dawned on me that the ammo is pretty heavy, so definitely need a handcart for that. Likely detachable wheels and trail so it packs in the storeroom better. Simple solution.