[Spaceships] Ammo storage vs Weapon size

[Snoman314]

I decided to see how I could house rule a VLS-type system i.e. a bunch of launch tubes that cannot be reloaded in combat. Allows more missiles to be launched faster, but fewer overall before needing to get more ammo, than a reloadable tube.
The rationale being that you take out the reloading mechanisms, and then use up the storage space with extra launch mechanisms. Should allow for multiple launch tubes, but with less shots that a reloadable tube.
So I've been running some numbers with regards to the ammo space that weapons in Spaceships have, and it's thrown up a few odd results.

For example, a 16cm missile launcher (as part of a given battery) is 0.5 tons, and has 5 shots. A 16cm gun or missile shot is 1/10 of a ton. So those 5 shots come to: 0.5 tons.
Hangon! Thats 100% ammo!

Its worse: 8cm gun: 0.5 tons system mass. 50 shots @ 1/80 per shot = 0.625 tons of ammo.
Now its 125% ammo!

Larger weapons have tiny ammo fractions: a 112cm launcher is about 5.3% ammo by mass.

This has stopped me in my tracks, trying to rule how many shots a VLS variant launcher could have.

[Ulzgoroth]

Errata: important!

Specifically, some of the ammo weights. 5 16cm missiles now weigh in at 1/3 ton. Still a high ammo fraction, but not quite as problematic. The 8cm gun similarly has smaller ammo now.

[Langy]

A VLS-type system only requires mass on the ship for a system to chuck the missile out of the ship before it lights its engines or possibly enough armor so that it can survive if the missile lights off engines while inside the launch cell. You also need fire control hardware, though that's likely relatively mass-cheap and you could probably just stick the fire control bits in the missile itself if you wanted to.

I'd think that this wouldn't mass more than the missile's own mass, perhaps a little more. This winds up with launch systems that mass about 50% of the system filled with missiles massing a further 50% of the system - which likely winds up with ships that have significantly more shots available along with larger salvos.

I'm not sure tube-style missiles make any sense in a system where surface area doesn't matter. Outside of things like underwater-launched torpedoes, I'm not sure anything but a VLS-type system makes sense for missiles.


Anyways, if you extrapolate downwards from 16cm missiles, you run into the same ammo mass problem still, though I can't remember what gun diameter shows the problem. It's due to the way weapon weight scales in regards to ammo weight - it's in no way linear. Not much of a problem unless you're planning on designing SM+2 or something ships, though, and that's not supported by the system.

[Snoman314]

Ahh errata, I obviously need to do another update. as Langy says though, the problem with ammo volume at different sizes remains.

Originally Posted by Langy

I'd think that this wouldn't mass more than the missile's own mass, perhaps a little more. This winds up with launch systems that mass about 50% of the system filled with missiles massing a further 50% of the system - which likely winds up with ships that have significantly more shots available along with larger salvos.

Uhh, what?

Originally Posted by Langy

I'm not sure tube-style missiles make any sense in a system where surface area doesn't matter. Outside of things like underwater-launched torpedoes, I'm not sure anything but a VLS-type system makes sense for missiles.

I figured the benefit to a single reloadable tube system like in submarines, would be the ability to stack the reloads tighter together, allowing more shots to be stuffed into the system. The downside is you can only fire one shot at a time. the canonical launchers have a RoF of 3 missiles/minute, so I take them to be reloadable tubes for that reason.

However a VLS type system could be a good tradeoff of RoF/vs ammo capacity, and indeed RL missile destroyers etc have gone this route, replacing single shot reloadable missile launchers with VLS systems. Hence me trying to work out some useable values.

Yes, I realise that not much is required to launch a missile. I was simply using the assumption that each missile's launch control/ejection hardware plus a tube/cradle for each missile to be able to be spat out from the hull, would take up a small, but measurable amount of mass.

However, when you look at the larger systems, lets say a 64cm launcher, then the system consists of 90% mass taken up with a single launch tube and reloading system, and 10% mass to store 100 missiles.
Converting this to a VLS system is troublesome, when I try to figure in the existing space used to fire a single missile.

[Snoman314]

I suppose I could just arbitrarily say that VLS's have half the number of shots.

EDIT: I don't know, that just doesn't feel crunchy enough. Does anyone have any suggestions?

[Langy]

Uhh, what?

What I was saying was that you can actually fit more missiles into a VLS-type system than you can a launch tube system for the same mass. If you want to figure out how many missiles you can fit in a VLS system, take the mass of the system (0.5 tons for SM+4, 1.5 tons for SM+5, 5 tons for SM+6, etc) and divide it by two. That's how much mass you have available for actual missiles.

Even that is likely overstating the mass requirements. You could probably get away with just using the mass capacity of a Hangar system - a VLS cell doesn't require a number of things that an actual hangar does, but it does need some mechanism for getting the missile out of the ship unless you're willing to fire off the main engine inside the cell.

Since realistically VLS cells should scale linearlly with missile mass and not the scaling given in the book for normal missile tubes (which also should scale linearlly with missile mass, as far as I can tell, and I can't figure out why they don't), you wind up with a lot more missiles of the same size (or bigger!) available in a dedicated VLS system than in a missile tube with reloads system and you can use all of them at once.

For an example of this, look at the difference between the Olivery Hazard Perry-class frigates and the Arleigh Burke-class destroyers. The Perry's had a single 40-round missile magazine for a single missile launcher firing 1500-pound missiles. The Burke's have ninety vertical launch system cells, each one firing a single 3000-pound missile, and the Burke's are only twice the displacement of the Perry's. They have more and bigger other weapons, as well.

So, for an SM+7 ship with a single Major Battery of missile tubes with reloads, you've got a single missile tube firing 28cm missiles with 15 reloads. A 28cm missile is 1/2 of a ton. If you instead switch to a VLS system, at worst you can fit 15 VLS cells (15 tons of capacity * 0.5 tons of missiles/tons of capacity * 1/0.5 tons/missile) each with a 28cm missile ready to fire. If you instead assume that you the mass requirements are the same as a Hangar bay instead of taking a full 100% of missile mass for the launch cells, you can fit 20 VLS cells of 28cm missiles in that same Major Battery.

[Snoman314]

Originally Posted by Langy

What I was saying was that you can actually fit more missiles into a VLS-type system than you can a launch tube system for the same mass. If you want to figure out how many missiles you can fit in a VLS system, take the mass of the system (0.5 tons for SM+4, 1.5 tons for SM+5, 5 tons for SM+6, etc) and divide it by two. That's how much mass you have available for actual missiles.

Even that is likely overstating the mass requirements. You could probably get away with just using the mass capacity of a Hangar system - a VLS cell doesn't require a number of things that an actual hangar does, but it does need some mechanism for getting the missile out of the ship unless you're willing to fire off the main engine inside the cell.

Since realistically VLS cells should scale linearlly with missile mass and not the scaling given in the book for normal missile tubes (which also should scale linearlly with missile mass, as far as I can tell, and I can't figure out why they don't), you wind up with a lot more missiles of the same size (or bigger!) available in a dedicated VLS system than in a missile tube with reloads system and you can use all of them at once.

For an example of this, look at the difference between the Olivery Hazard Perry-class frigates and the Arleigh Burke-class destroyers. The Perry's had a single 40-round missile magazine for a single missile launcher firing 1500-pound missiles. The Burke's have ninety vertical launch system cells, each one firing a single 3000-pound missile, and the Burke's are only twice the displacement of the Perry's. They have more and bigger other weapons, as well.

So, for an SM+7 ship with a single Major Battery of missile tubes with reloads, you've got a single missile tube firing 28cm missiles with 15 reloads. A 28cm missile is 1/2 of a ton. If you instead switch to a VLS system, at worst you can fit 15 VLS cells (15 tons of capacity * 0.5 tons of missiles/tons of capacity * 1/0.5 tons/missile) each with a 28cm missile ready to fire. If you instead assume that you the mass requirements are the same as a Hangar bay instead of taking a full 100% of missile mass for the launch cells, you can fit 20 VLS cells of 28cm missiles in that same Major Battery.

Ahh I see, but unfortunately, that would mean that if this was how I was to make my VLS's, there would be no reason to use the normal systems.
Your numbers make sense logically, but don't balance well the current system.

EDIT: I'm going to have another look at this, but busy right now.

[Langy]

I agree, but that's fine, because, as I said, there's very little to no reason to use the normal system.

You can still use it if you want a ridiculous number of reloads, of course - with that same SM+7 major battery, you could have a 30 shot VLS in two major batteries or you could have a single launch tube and 45 reloads in one major battery and one cargo hold. It's not particularly useful, but you can still do it. It's also easier to reload than a VLS.

Why would you want to balance it in regards to the normal, non-VLS method, anyways? Non-VLS missiles suck in comparison to VLS missiles in real life, which is why the US Navy stopped using. The only thing better than a VLS system is a hardpoint, where the missile is on the outside of the ship and doesn't even need a seperate launching mechanism. It'll be an exposed system, but it'll also be able to carry twice as many missiles as a VLS system.

[Ulzgoroth]

Note that hanger bays do have a limited launch rate, which scales as surface area.

An SM+15 hangar launching 5000 tons of missiles per minute puts you in a very good position compared to the 120 ton/minute launch rate that a SM+15 major battery can pull off, though... (Not that there's any reason I can come up with to want to launch 112cm missiles.)

[Langy]

There's no mass-based reason hangars need to scale in that fashion. It makes sense for larger ships, but not so much when your 'hangar' is only ten meters deep.

In other words: When using them for a VLS type system, you should be fine with just saying they can all fire at once, regardless of the total tonnage involved.