[Spaceships] Don't die with smartbombs: using SS4 X-ray laser warheads

[Ulzgoroth]

Spaceships 4 gives us nuke-pumped X-ray laser standoff warheads for missiles. But these aren't Honor Harrington's X-ray lasers...

The warhead generates a number of short-ranged laser strikes. But each one is quite low-powered. Even assuming that the numbers given are in dDamage, the 10d(5) beams pose very little threat to any well-protected ship over SM+10. So bombing a superdreadnought with these laser heads is right out.

So instead, use them on targets that can be impressed by 35 points of damage: fighters. A single hit will badly damage even the hardiest of SM+6 heavy fighters, and the shotgun design can provide multiple strikes from one warhead. The standoff range of the lasers is moderate, but matches that of most fighter-borne particle beams.

This is a useful option for any unit wanting to engage fighter swarms at a standoff range, where KK warheads may be exposed to unacceptable amounts of point defense. But for fighter craft it offers another possibility, especially when mated to the missile-tube launched bomb option. A single 16cm launcher can house up to 15 X-ray laser bombs. Such a bomb fired into space and detonated immediately provides a direct multi-beam attack far more powerful than any that the ship could mount directly, capable of striking in any direction. One 202k bomb is likely to cripple or kill an enemy fighter instantly out to 300 miles, and doesn't even require missile-operation skills as it is fired with Gunner (beam). (Being a missile-based weapon, it may also be eligible for a low -1 per target spread fire penalty.)

[Kenny]

This weapon would also make a good capital ship anti-fighter defence weapon.

[Langy]

At TL10, bomb pumped X-Ray lasers can actually be quite dangerous compared with normal missiles - bomb pumped lasers don't get hit by point defense, unless I'm not reading it right. And the (5) armor divisor means that 10d damage is capable of penetrating up to an SM+13 ship's hull, assuming it isn't hardened and has only one layer of nanocomposite armor. Even if it's hardened, it can penetrate up to an SM+12 ship with one layer of nanocomp. If a ship has multiple layers, SM+10 or 11 becomes impervious, of course. But it's important to note that the bomb-pumped lasers aren't strictly for smaller targets.

I do wish they did more damage, though, and were capable anti-capital ship weapons in their own right. Maybe instead of increasing the number of lasing rods, making the bomb bigger could increase the nuclear charge, resulting in an increase in damage - though I have to admit that I don't know if that would work. I certainly like to think so - it would let you have 16cm anti-fighter pumped lasers doing 10d(5) and, say, 56cm anti-capital pumped lasers doing 100d(5) or so.

[Ulzgoroth]

Originally Posted by Langy

At TL10, bomb pumped X-Ray lasers can actually be quite dangerous compared with normal missiles - bomb pumped lasers don't get hit by point defense, unless I'm not reading it right. And the (5) armor divisor means that 10d damage is capable of penetrating up to an SM+13 ship's hull, assuming it isn't hardened and has only one layer of nanocomposite armor. Even if it's hardened, it can penetrate up to an SM+12 ship with one layer of nanocomp. If a ship has multiple layers, SM+10 or 11 becomes impervious, of course. But it's important to note that the bomb-pumped lasers aren't strictly for smaller targets.

They certainly should bypass last-ditch point defense. If using tactical combat you can and probably should fire on them before they reach their 300 mile effective attack range.

Unhardened armor on warships is almost totally unbelievable at TL10, unless hardened armor is for some reason not available in the setting. If you really have to cut costs you can use low-TL armor, but harden it. And the thin-skinned SM+12 ship will only take a couple damage per strike, though you could put it through the death of a thousand cuts with enough warheads.

"well-protected" means 'definitely at least two hardened layers' in my book. YMMV, and certainly against more lightly protected craft the laser heads can be effective.

Originally Posted by Langy

I do wish they did more damage, though, and were capable anti-capital ship weapons in their own right. Maybe instead of increasing the number of lasing rods, making the bomb bigger could increase the nuclear charge, resulting in an increase in damage - though I have to admit that I don't know if that would work. I certainly like to think so - it would let you have 16cm anti-fighter pumped lasers doing 10d(5) and, say, 56cm anti-capital pumped lasers doing 100d(5) or so.

Anti-capital heavy X-ray heads would be nice to have numbers for, definitely. Especially if they're technically sound.

[jacobmuller]

Increasing damage with calibre I like.
How would you scale damage?

1: Treat offical damage as RoFx(10^2), figure new damage as SQRT(official/8)? eg 16 to 32cm become 10 to 14d damage, 64cm becomes 20d, 96cm 25d...

2: scale it in line with standard warhead damage? 32cm = 20d, 64cm = 40d, 96cm = 60d...

3: use the nuke scaling? 20-32cm become 20d, 40-48cm 100d, 56-96cm 200d...

[Langy]

I'd generally scale it the same way beam weapons are scaled - six increases in SM for one ten-fold increase in destructive power. This is, of course, assuming that there's no increase in the number of lasing rods, so RoF would be held constant. Going the nuke way would mean scaling up 10-fold damage increase for every five SMs it goes up, and scaling up based on conventional warhead damage makes very, very little sense when you consider how conventional warhead damage is calculated in the first place.

[jacobmuller]

Would that come out roughly as: 16cm 10d; 20cm 15d; 24cm 20d; 28cm 30d; 32cm 50d; 40cm 70d, etc. (96cm 500d)?

[Langy]

Beam weapon progression tables actually go 10, 15, 20, 30, 40, 60, 100 (unless they've been Errata'd?). But yeah, that's more or less right.

[cmdicely]

Originally Posted by jacobmuller

Increasing damage with calibre I like.
How would you scale damage?

Here's the way I see it:

Damage of beam weapons in GURPS Spaceships usually scales with the cube root of the energy of the attack. Making some reasonable assumptions, the total energy of the laser attacks should scale with the cube of the diameter of the missile (bomb, shell, etc.). So if --as is already the case in SS4 -- the number of beams scales linearly with the diameter, then the energy per beam should scale with the square of the diameter and, consequently, the damage per beam should scale with the 2/3 power of the diameter.

Roughly, keeping 16cm warheads doing 10d(5) per beam with a range, that gives a damage of 11d(5) for 20cm, 12d(5) for 24cm, 14d(5) for 28cm, 16d(5) for 32cm, 18d(5)for 40cm, 20d(5) for 48cm, 22d(5) for 56cm, 25d(5) for 64cm, 28d(5) for 80cm, 32d(5) for 96cm, and 36d(5) for 112cm.

16cm - 56cm warheads will have a beam range of 300/1000mi
64cm and larger warheads will have a beam range of 700/2000mi

[Langy]

If the beam damage goes up with the cube root of the energy of the attack, and a 25 megaton warhead nuke provides 10 times the energy of a 25 kiloton nuke, it follows that a 96cm x-ray laser warhead (25 megaton nuke, following the progression for normal nukes) would do ten times the damage of a 16cm x-ray laser warhead (25 kiloton nuke, following the progression for normal nukes). That is, it would do 100d(5) damage. That's ten SM steps per full 10x increase in damage.