[Spaceships] Are spaceships unrealistically cheap?

[Michael Thayne]

Now I'm curious if we can actually model missiles with scaled-down SS rules. There are going to be issues with e.g. the fact if the jump in delta-V between 28cm and 32cm is due to more stages, damage should temporarily plateau due to a smaller warhead, but let's see how close we can get.

A 24cm missile, as a spaceship, would a 2dHP impactor, because it does 6dx6 damage and collision damage is 6d x 3 x dHP. It weights 1/4 of a ton loaded into the battery. That's approximately SM+1, which ought to have 5 dHP. So the impactor should have an SM 2 levels lower than the missile loaded into the battery.

If the warhead is itself a single SM+1 system, then at TL7-8 a single-stage design has sixteen fuel tanks (plus two engines, the warhead, and a control room), for 4.8 mps delta-V, below the Spaceships 3 performance. But a TL9+ HEDM design needs 2.5 engines for 5G acceleration, so it has 15.5 fuel tanks, and 13.95 delta-V—better than the stats given in Spaceships 3!

If the warhead + control systems are a full upper stage (six systems), instead we have 11.5 fuel tanks for an HEDM missile with 5G acceleration, which together give 8.05 mps delta-V. Packing 2 mps delta-V into the upper stage, however, only requires devoting about a third of the upper stage to engines / fuel.

So not sure spaceships missiles can quite be built with spaceships itself, but it feels like we're within the realm of "generous rounding" here. The vast cost mark-up is hard to justify. The lower stage of our HEDM missile is only going to cost around $10k per ton of complete missile, so unless warheads are very expensive or the markup for a slightly more compact design is 100x, the numbers just don't work.

(Actually, I'd never done the price math explicitly before, it looks worse than I'd thought.)

[malloyd]

Originally Posted by Michael Thayne

For fighters, I won't do a full build, but it only takes one jet engine to get 1G of acceleration, and the heavier fighters in Pyramid #3/53 are only ~30 tons (SM+5 on the Spaceships scale). An SM+5 jet engine is $300K, compared to the multi-million dollar price tag for the fighters in Pyramid.

Here in the real world the expensive part of military vehicles is never the engine, and rarely the weapons, it's the electronics. An engine being 10% of the cost actually seems completely reasonable to me. It's certainly possible Spaceships underprices the electronics though.

So Spaceships understates the price by at least a factor of three.

If it actually hits to within a factor of 3, that's essentially a perfect match. Prices of stuff does after all vary by a factor of two all the time (sold at 100% markup, or 50% off) in reality, so no game price can possible be more "accurate" than that. But if it bothers you as a GM, you can always raise the price.

[Michael Thayne]

Originally Posted by malloyd

Here in the real world the expensive part of military vehicles is never the engine, and rarely the weapons, it's the electronics. An engine being 10% of the cost actually seems completely reasonable to me. It's certainly possible Spaceships underprices the electronics though.

It works out to the engine being more like 3% of the cost.

Underpricing of electronics would explain a lot, though. In Spaceships the control room costs a fifth of what the engine does, and pricey electronics like tactical arrays and defensive ECM have the same per-system cost as a jet engine.

If it actually hits to within a factor of 3, that's essentially a perfect match. Prices of stuff does after all vary by a factor of two all the time (sold at 100% markup, or 50% off) in reality, so no game price can possible be more "accurate" than that. But if it bothers you as a GM, you can always raise the price.

Being within a factor of 3 of real-world prices is fine. Being within a factor of 3 of canonical game prices of extremely similar items seams like more of a problem. At that point you may as well be using abstract wealth with x10 bands.

[Michael Thayne]

Big caveat for missiles: they have positive sAcc, which requires giving a ship positive Hnd if you want to match that kind of performance, and that's nigh impossible in space (as opposed to atmosphere) with < 10G thrust.

[vicky_molokh]

Originally Posted by Michael Thayne

Big caveat for missiles: they have positive sAcc, which requires giving a ship positive Hnd if you want to match that kind of performance, and that's nigh impossible in space (as opposed to atmosphere) with < 10G thrust.

Wouldn't that be more a matter of the targeting system's Piloting (Missile) skill level?

[Michael Thayne]

Originally Posted by vicky_molokh

Wouldn't that be more a matter of the targeting system's Piloting (Missile) skill level?

I don't think so. Ramming spacecraft use piloting skill even if they're autonomous drones launched from a carrier. Skill of carrier's crew has nothing to do with it AFAICT. Missiles use skill of gunner on launching craft.

This is a pretty big deal at high TLs. At TL 10, 32cm+ missiles have sAcc +3, which under the rapid fire rules is as good as firing x8 as many missiles when you're trying to overwhelm point defense.

[Tyneras]

There's also a significant price difference between cutting edge weapons technology produced in small lots and mature mass manufactured technology. Unless stated otherwise I generally assume most technology presented in GURPS has the mature technology price tag.

[sayke]

Just increase the price by a factor of 3, and control rooms/sensors/arrays etc by a factor of 10. Done.

But remember: You can basically do whatever you want.

[vicky_molokh]

Originally Posted by Michael Thayne

I don't think so. Ramming spacecraft use piloting skill even if they're autonomous drones launched from a carrier. Skill of carrier's crew has nothing to do with it AFAICT. Missiles use skill of gunner on launching craft.

This is a pretty big deal at high TLs. At TL 10, 32cm+ missiles have sAcc +3, which under the rapid fire rules is as good as firing x8 as many missiles when you're trying to overwhelm point defense.

What I mean is that sAcc of homing missiles may include the abstraction of the competence of onboard electronics. SS is a rather abstract system.

[Michael Thayne]

Originally Posted by vicky_molokh

What I mean is that sAcc of homing missiles may include the abstraction of the competence of onboard electronics. SS is a rather abstract system.

Spaceships is very abstract but the abstractions work very differently such that they're hard to compare. AFAICT Spaceships missiles don't use the guided/homing rules used in normal combat, so good missile sAcc and a high Artillery (Guided Missile) skill for the launching ship "stack" in a way that good drone AI Piloting skill fails to stack with any skills of characters on your carrier. This gives missiles an important edge that can't remotely be replicated with the rules for building spacecraft, and arguably justifies the higher price from a game-balance perspective if not from an in-story perspective.