[SPACESHIPS] So, missile performance...

[cmdicely]

Trying to select technology for a space game I'm trying to piece together, I noticed that the performance of super missiles in SPACESHIPS 3 seem low for, well, a game in which super torch drives exist. So this got me playing around with trying to find a way to set stats for missiles to assure that the tech assumptions for missiles (and, particularly, missile drive thrust and endurance) are in line with those being used for spaceships more generally. So I came up with this sketch for designing missiles that extrapolates the SPACESHIPS rules for ship design that enables freeform missile design, and also keeps them consistent with ship drives. I thought I'd share it in case others could get some use out of it. There are a couple of other notable impacts with it -- standard missiles lose quite a bit of ΔV, but also become cheaper.

A normal missile consists of:

• payload (warhead, guidance, etc.; equivalent to a bomb), 30% of mass equivalent to 6 systems
• engines
  • at TL7-8, standard missiles use 10% mass in chemical rockets
  • at TL9+, standard missiles use 15% mass in HEDM rockets
• fuel (for standard missiles, 55-60% of mass) equivalent to 12 systems

So:

• a TL7-8 standard missile has 6G acceleration, 2.52mps ΔV
• a TL9 standard missile has 6G acceleration, 7.7mps ΔV

Alternate missiles

TL9^ NSR missile

• standard payload
• engine, 15% mass in Nuclear Saltwater Rocket
• fuel, 55% water reaction mass
• 6G acceleration, 38.5mps ΔV

TL10^+ Fusion Torch missile

• standard payload
• engine, 20% mass in high-thrust fusion torch engines
• fuel, 50% water
• performance
  • at TL10^, 12G acceleration, 35mps ΔV
  • at TL11^, 12G acceleration, 105mps ΔV
  • at TL12^, 12G acceleration, 350mps ΔV

TL11^+ Super Fusion Torch missile

• standard payload
• engine, 20% mass in high thrust Super Fusion Torch engines
• fuel, 50% water
• performance: 1200G acceleration, 1050mps ΔV

TL10^+ Antimatter Plasma Torch missile

• standard payload
• engine, 20% mass in high-thrust AM Plasma Torch engines
• fuel, 50% AM-boosted water
• performance
  • at TL10^, 24G acceleration, 336mps ΔV
  • at TL11^, 24G acceleration, 1008mps ΔV

TL11^ Super Antimatter Plasma Torch missile

• standard payload
• engine, 20% mass in high-thrust super antimatter plasma torch missile
• fuel, 50% antimatter-boosted water
• performance: 2400G acceleration, 840mps ΔV

Missile cost:

The cost of a standard missile payload is equal to a cost of a bomb in the standard rules: 100K per ton of payload mass, or $30K per ton of missile mass. So, a 32cm (1 ton) missile with a standard payload has a payload cost of $30K/ton ⨯ 1 ton = $30K.

Engine cost is equal to missile mass times the cost of an SM +6 engine module times engine mass fraction divided by 5 tons. E.g., a 32cm (1 ton) standard TL7-8 missile has an egine cost of 1 ton ⨯ $200K ⨯ 0.1 / 5 tons = $4K.

The fuel cost of a missile is equal to the mass of the missile times the cost of a ton of fuel times the mass fraction of the fuel. E.g., a 32cm (1 ton) standard TL7-8 missile has a fuel cost of 1 ton ⨯ $800/ton ⨯ 0.6 = $480.

So, a 32cm TL7 standard missile costs $30K + $4K + $480, or about $35K.

Alternate Payloads and Control System:

The normal missile payload system (a bomb or sensor probe) is 30% of the mass of the missile and includes a control system, but missiles with alternative payloads need a separate control system, massing 5% of the missile mass with a cost of $100K per ton.

One common alternate payload is a bus missile; in addition to the control system, this includes some number of identical smaller missiles (possibly only one, in which case it is more of a multi-stage missile than a bus missile), which are deployed from the larger missile -- a salvo of identical bus missiles is replaced on the map with a single salvo of all the submunitions when they are deployed. This technique allows larger missile frames to be used for longer range missiles, though (unlike the standard SPACESHIPS 3 stats) larger missiles with standard payloads are not larger than otherwise-similar smaller payloads.