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Old 02-13-2016, 04:02 PM   #1
Marasmusine
 
Join Date: Feb 2005
Location: Doncaster, UK
Default [Spaceships] Some Missile Options

Hello, I've been converting the Sulaco (from Aliens) to GURPS with the help of the Colonial Marines Technical Manual. It's primary attack is a battery of 8 ASAT missiles. These are large caliber two-stage missiles. Maybe there's an option for bigger missiles in a supplement I don't have, but here's what I've come up with.

A missile launcher can be rated for higher caliber missiles, but this reduces its ammunition.
1 step, 1/2 ammunition (rounded down)
2 steps, 1/3 ammunition
3 steps, 1/5 ammunition
4 steps, 1/8 ammunition

For example, a SM +8 missile launcher in a major battery that fires 48 cm missiles (two steps up) carries 6 of those missiles (instead of 20 x 32 cm).

I worked out these divisors by getting the total tonnage of missiles for each SM, then dividing this by the weight of the larger missile, then finding the overall best-fit fraction.

Next, the two-stage missiles. This is the same as a multi-stage ship, so I know they have 3 times the mass (so the missile launcher has 1/3 the capacity).

Using ericbsmith's spreadsheet, the Sulaco is SM +11.5, so a major missile battery normally gives me 85 x 60 cm missiles. So the above modifiers gives me a battery of 9 x 88 cm two-stage missiles (near enough to 8 of them)

What I'd like to work out is the actual effect of a two-stage missile in the spaceship combat rules. I know it has more dV. What do you think?
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Old 02-13-2016, 04:29 PM   #2
RyanW
 
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Default Re: [Spaceships] Some Missile Options

I think a multistage missile is already assumed. By the rules, to get a larger missile, you use a larger weapon battery (spinal>major>medium>secondary>tertiary).
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Old 02-13-2016, 07:57 PM   #3
chandley
 
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Default Re: [Spaceships] Some Missile Options

Quote:
Originally Posted by Marasmusine View Post

What I'd like to work out is the actual effect of a two-stage missile in the spaceship combat rules. I know it has more dV. What do you think?
You could potentially end up with a higher minimum velocity, depending on how you built the boost stage and bus stage. Remember to give it enough accel to burn through its deltaV in your expected engagement range (usually Extreme for missiles, but you might make a multistage go even farther out, becoming more of a THS AKV than a spaceships missile).
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Old 02-14-2016, 02:59 AM   #4
Marasmusine
 
Join Date: Feb 2005
Location: Doncaster, UK
Default Re: [Spaceships] Some Missile Options

Quote:
Originally Posted by RyanW View Post
I think a multistage missile is already assumed. By the rules, to get a larger missile, you use a larger weapon battery (spinal>major>medium>secondary>tertiary).
This is one module (so not spinal) that is filled with eight big missiles. ASAT missiles are designed to be launched from the surface of a planet. A real-world TL 7 example: the ASM-135 ASAT (50 cm caliber) was to be launched by a F-15 Tomcat (SM +5). A SM +5 spinal mount gives us 7 x 24 cm. Using my modifier above, we get 1 x 48 cm.

I'm also thinking of the Interceptor from UFO. The only armament is one big missile!
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Old 02-14-2016, 03:29 AM   #5
Marasmusine
 
Join Date: Feb 2005
Location: Doncaster, UK
Default Re: [Spaceships] Some Missile Options

Yeah, thinking about it, I'll dispense with the multi-stage thing.

For those interested I've worked out the divisor for a 5-step increase in caliber as 1/15.

I'll use the four-step increase for the Sulaco, giving it 10 x 120 cm (fudging it down to 8).
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