What RPG has the best spaceship design system?

[Pomphis]

Originally Posted by Fred Brackin

Going by the standard of modern missiles (either Radar or IR) I doubt even a full Complexity 1 is needed.

But what about the comm/sensor array rating? To find and track a probably stealthed ship over at least thousands, if not tens or hundreds of thousands of miles?

In GT that led us to remote control, lightspeed timelag, terminal guidance

[Anthony]

Originally Posted by Pomphis

But what about the comm/sensor array rating? To find and track a probably stealthed ship over at least thousands, if not tens or hundreds of thousands of miles?

A ship that isn't under thrust doesn't need tracking (just extrapolate from its original vector), a ship that's under thrust isn't stealthy, and the sensor rules from GURPS Vehicles underrate small sensors and the ease of detection in space, overrate large sensors.

[Fred Brackin]

Originally Posted by Pomphis

But what about the comm/sensor array rating? To find and track a probably stealthed ship over at least thousands, if not tens or hundreds of thousands of miles?

In GT that led us to remote control, lightspeed timelag, terminal guidance

If your missile is a chemical fuel solid fuel propulsion let's call it an average of 6Gs for 1 minute. That's average-ish for such things. The shuttle SRBs with their 2 minute burns were outliers just on that basis.

So 6Gs for 1 minute gets you 2.18 miles for impact velocity and a powered envelope of 65 miles. You'll need a second stage to extend that or to maneuver for closing.

If your second stage is another solid booster with the same thrust-to-weight ratio you double impact velocity and quadruple the powered envelope for continuous thrust. If you coast between the first and second stages range is theoretically unlimited but a continuously thrusting ship may be able to outrun the missile then.

So for these only a little bit beyond current day missiles lightspeed lag is to small to be relevent.. Traveller's 6G (or more) for an hour missiles are different but even then you don't need one-on-one remote control. You only need to broadcast a running update from the launching ship's sensors. Salvos wouldn't be limited to the number of missile tubes the ship has. They'd be good for as many mssiles as you could boot out the cargo bay.

[Michael Thayne]

Originally Posted by Fred Brackin

Not true for even for chemical explosives. more framework and armor will just make more shrapnel. With nukes the difference would be barely detectable.

Originally Posted by Varyon

Honestly, the way proximity detonation works doesn't make a lot of physical sense - each fragment should do less damage, rather than just having a lower armor divisor (for a slow-moving missile, the explosion may well propel the fragments quickly enough they gain damage - but in that case the explosion would actually make the missile deal more damage on a direct impact, and that's not represented, given Spaceships assumes enough relative velocity that the impact does more damage than conventional explosives would). Additionally, seeing as once the missile explodes it can no longer navigate, it should need to be close enough to the target before exploding that point defenses should be able to target the full missile rather than the individual fragments (or, perhaps, distinct clouds thereof, if each "hit" is meant to represent multiple fragments impacting... but then simply halving the armor divisor is insufficient). If "proximity detonation" actually means releasing submunitions (smaller missiles), I don't see why this would cause a loss of armor divisor (if anything, the submunitions should be more dense, seeing as they don't need to pack a bunch of missiles into their frames)... or honestly why you'd use the carrier without releasing its submunitions.

Spaceships missiles are weird. Honestly, I wouldn't be opposed to just getting rid of them and replacing them with ones built as vehicles.

On the forums, David has said that "proximity detonation" actually involves releasing submunitions. Though I realize checking now that this isn't supported in the text of Spaceships itself.

[Anthony]

Originally Posted by Fred Brackin

If your missile is a chemical fuel solid fuel propulsion let's call it an average of 6Gs for 1 minute.

What sort of performance you want is heavily dependent on the performance of the target (6 km/s is a lot for a simple missile, though). If you're attacking targets with 0.01G sustained thrust you might kick your missile up to 2-3 km/s and then let it coast with another 1 km/s available for course correction; it takes 10,000s the target to adjust its vector by 1 km/s so you can hit at 20-30,000 km. Faster targets reduce range proportionately.

[Varyon]

Originally Posted by Michael Thayne

On the forums, David has said that "proximity detonation" actually involves releasing submunitions. Though I realize checking now that this isn't supported in the text of Spaceships itself.

I did recall some bits and pieces of that post (probably where I got the idea it may be submunitions rather than fragments and/or represent multiple impacts for each "hit"), but personally I think one big problem with that concept is that the missiles themselves don't really work like that in play. For example, he mentions that a missile without all the decoys, submunitions, etc would be trivial to intercept... yet a ramming ship doesn't have any of that going for it, and is no easier to hit than a missile of the same size (indeed, unless the pilot is using an All Out Attack, I believe a ramming ship is harder to intercept than a missile, as it can Dodge). As I said, part of me really thinks ditching the default missiles and just building them all as automated (or remote-controlled) spacecraft may be the way to go.

[Anaraxes]

Originally Posted by Fred Brackin

I've always assumed that "Can a missile hit?" was quite simple. You take the amount of Delta-V required for the missile to intercept.

Particularly when we're talking about kinetic kill missiles, engine power becomes important, not just delta-v. (Ion thruster or chemical rocket?) For damage, you want as high of a velocity as you can get; 1/2 m v^2 and all that. But high-speed missiles have trouble hitting their target because they can't bend their trajectory much in the time they have before they fly by the target once their guidance system projects a miss. They might have plenty of delta-v that would have worked if only they were moving more slowly, and thus had more time to apply that delta-v, but if the engine power (the rate at which it can apply energy to change its velocity) is finite, then time becomes important as well. If the KKV isn't constantly accelerating to maximize its damage potential, but cruising/coasting slowly enough to make sure it can intercept, then that same engine power limit will limit the damage it can do with a doctrine of trying to accelerate at the last minute before impact. And of course any power the missile is applying to correct its course on that final approach isn't available for increasing damage.

Game designers concerned about strict realism have to think about their tech assumptions as they relate to the time/distance scale of their game.

[Fred Brackin]

Originally Posted by Anaraxes

Particularly when we're talking about kinetic kill missiles, engine power becomes important, not just delta-v. (Ion thruster or chemical rocket?) F

I'll admit that I've never considered an ion thruster missile but I think I know why. You'd have to be firing at something with an even lower acceleration.

If you were firing your ion thruster missile from the outer solar system and aiming at an immobile target on an airless world that might work.

Usually though "ion thruster v. chemical rocket" isn't much of a choice.

[Varyon]

Originally Posted by Fred Brackin

I'll admit that I've never considered an ion thruster missile but I think I know why. You'd have to be firing at something with an even lower acceleration.

If you were firing your ion thruster missile from the outer solar system and aiming at an immobile target on an airless world that might work.

Usually though "ion thruster v. chemical rocket" isn't much of a choice.

In a setting where ships generally use ion thrusters, solar sails, or similar, an ion thruster missile could be workable (a missile that has invested 30% of its mass in ion thrusters is going to outperform a ship that has similarly invested only 5%), although the fact it can't do lateral shifts very well is going to make it a lot easier to intercept.

[Anthony]

Originally Posted by Anaraxes

Particularly when we're talking about kinetic kill missiles, engine power becomes important, not just delta-v. (Ion thruster or chemical rocket?) For damage, you want as high of a velocity as you can get; 1/2 m v^2 and all that. But high-speed missiles have trouble hitting their target because they can't bend their trajectory much in the time they have before they fly by the target once their guidance system projects a miss.

Most of that is specific to atmospheric missiles. You do need a certain amount of excess power to compensate for unknowns in target transverse velocity, but it's generally not very large.