Conditional Spaceships
My approach to simplifying and streamlining Conditional Injury wasn’t posted without ulterior motive. Rather, it was because I had been looking at GURPS Spaceships and had found that CI simplifies and clarifies many things there.
The analysis isn’t particularly new (Mailanka made similar points here) but I do think the CI lens adds an interesting perspective.
Note: I’ll be talking both about spacecraft sizes and attributes relative to their size. For the former, I’ll use the standard format of SM+10 to mark a spacecraft of size modifier 10; for the latter, SM + 10 (see the spaces?) for something that takes the SM and adds 10 to it. An SM+10 spacecraft would have a value of 20, for example.
Health
If you look at the table in SS1:9, you see something beautiful: HP (well, dHP) in that table scales exactly like the SSR table does—which is exactly how Conditional Injury scales.
That means an SM+5 craft, at 200 HP, has a Robustness Threshold of 12. Every spacecraft has an RT of SM + 7. No exceptions.
Armour
Armour scales exactly the same way. Take Metallic Laminate, with its dDR of 3 for unstreamlined SM+5 spacecraft. That’s an RT of 7; accordingly, a single unstreamlined Metallic Laminate armour system for any spacecraft is an SM + 2 Armour Potential. Every “improved” armour system gives you one more Armour Potential than the one below it; streamlined reduces it by 1. That gives us the following values:
| Armour Type | Armour Potential |
|---|---|
| Ice | SM - 4 |
| Stone | SM - 3 |
| Steel | SM |
| Light Alloy | SM + 1 |
| Metallic Laminate (or Organic) | SM + 2 |
| Advanced Metallic Laminate | SM + 3 |
| Nanocomposite | SM + 4 |
| Diamondoid | SM + 5 |
| Exotic Laminate | SM + 6 |
This is modified by:
| Modified by | Modifier |
|---|---|
| Streamlined | - 1 |
| 2 Systems | + 2 |
| 3 Systems | + 3 |
| 5 Systems | + 4 |
Weapons
Similar to armour and HP, weapons also scale with SM—with one unfortunate exception.
Beam Weapons
These do scale according to SM. The weapon table at SS1:67 shows two dDam values: One for anti-particle and plasma beams, and one for everything else (but graviton beams have 1/10th the output). A major battery for an SM+10 spacecraft has a beam output of 3 GJ; that’s 6dx10 dDam2 for 18 Wound Potential. For dDam1, it’s 3dx10, for 16 Wound Potential. Graviton beams have 14 Wound Potential.
We can therefore build the following table:
| Wound Potential | |
|---|---|
| Base | SM + 6 |
| Anti-particle or plasma | + 2 |
| Graviton | - 2 |
| Medium Battery | - 1 |
| Secondary Battery | - 2 |
| Tertiary Battery | - 3 |
| Spinal Battery | + 1 |
As as example, a Graviton-beam Secondary Battery has a relative Wound Potential of SM + 2; for an SM+10 craft (with its own RT of 17), that’s Wound Potential of 12.
And here’s all of the armour reductions:
| Weapon | Armour Reduction |
|---|---|
| Heat Ray | |
| Laser | (-2) |
| Particle | (-4) |
| Plasma | (-2) |
| UV Laser | (-2) |
| Antiparticle | (-3) |
| Ghost Particle | (-inf) |
| Graviton | (-inf) |
| X-Ray Laser | (-4) |
| Conversion | (-6) |
| Disintegrator | (-inf) |
| Graser | (-6) |
Nuclear and Antimatter Warheads
These are of a fixed yield depending on their size. In space, they inflict
| Yield | Wound Potential | … with proximity detonation |
|---|---|---|
| 25 kiloton | 23 | 11 |
| 100 kiloton | 25 | 13 |
| 2.5 megaton | 29 | 17 |
| 10 megaton | 31 | 19 |
While they are all extremely dangerous (the 25 kiloton warhead inflicts more damage than an SM+15 spinal laser cannon), this is only with detonations directly in contact with the hull.
There’s also the bomb-pumped X-ray warhead from SS8:9. That does WT 13 (-4) no matter the size. It does so with RoF of diameter/2, which is always more than 8.
Kinetic Weapons
Here, we come to our one exception. Kinetic warheads scale strangely. At SM+5, a major battery fires 10cm calibre projectiles. That’s a base damage of 3dx5, so Wound Potential of 14. If we take an EM gun, base damage is doubled due to minimum velocity, and so Wound Potential is 16. Firing at another SM+5 target (with RT of 12) inflicts a Severity+4 wounds; Instantly Fatal.
At SM+10, calibre’s 24cm, for 6dx6 d-damage. That’s 17 WP (19 for an EM gun). Yet an SM+10 target has an RT of 17, so it’s “just” crippled.
At SM+15, calibre is 56cm, for 6dx14 d-damage and 19 WP (21 for an EM gun). An SM+15 target has an RT of 23, though, making these just Major Wounds.
As one can see, gun damage is SM / 2 + 12, with an additional +2 to EM guns from their higher base velocity. This doesn’t scale nicely, and it doesn’t mesh with any of the other numbers. It makes kinetic weapons essential at lower SM and useless at larger SM.
Missiles are much the same, except they get another +4 to their damage compared to gun shells.
I am unhappy with this scaling. It complicates analysis and takes away from interesting decisions. I do like the idea of just using the same scaling as for beam weapons (Pyramid 3/34 has an alternate rule called “The Square Root of Destruction”; this is essentially “The Cube Root of Destruction”). Of course, they also scale with impact velocity: Since the formula multiplies with velocity, we can still use the SSR table and just add it:
| Velocity (km/sec) | Damage Modifier |
|---|---|
| 1 | +0 |
| 1.5 | +1 |
| 2 | +2 |
| 3 | +3 |
| 5 | +4 |
| 7 | +5 |
| 10 | +6 |
| 15 | +7 |
| 20 | +8 |
| 30 | +9 |
| 50 | +10 |
| 70 | +11 |
| 100 | +12 |
If we scale the base damage as we do with beam weapons, the main question becomes what the Wound Potential is. For a laser, it’s SM + 6. For EM guns, we can expect efficencies of about 90%, compared to a laser’s maybe 25%. That’s a factor of 3.5. Let’s call it 3, for +3 to damage. But EM guns already have a muzzle velocity of 3 km/s—that’s exactly that +3. So, EM guns can simply use the same base damage as lasers have, and remember that they get +3 from impact velocity when firing from rest.
Missiles, in comparison, are bigger. They do 4 more wounding compared to guns (you fire in missiles what the same battery 4 SM bigger fires as guns), for SM + 10.
Injury Accumulation
By default, injury accumulates based on HT rolls, with a bonus for smaller injuries (everything below Crippled). Spaceships have HT of 12 to 14 (depending on some factors). If we assume HT 13 as the default, a Minor (-3) wound will have us roll against 16, for a probability of success of 98%. That’s not quite the effect we’d like.
If we follow Exxar’s proposal of using Douglas Cole’s Defend vs Death and roll vs HT/2 + 3, we end up rolling vs 9 as a base value. If you do the math on this, it turns out there’s a perfectly nice way of doing injury accumulation that doesn’t require any rolls at all: You write down all of the injury levels from -6 to 0. If you receive an injury, you put a marker on the corresponding slot. If there’s a marker already in there, you instead move it to the next-higher injury marker. Repeat if necessary. That makes all of the accumulation rolls into powers-of-two:
| Severity | Rolls to First Death Check |
|---|---|
| -6 | 128 |
| -5 | 64 |
| -4 | 32 |
| -3 | 16 |
| -2 | 8 |
| -1 | 4 |
| 0 | 2 |
Example Combats
Let’s take a simple example. In the left corner, we have three weapon systems. These might be spinal, major batteries, or anything smaller. For a laser, it’ll have SM + 6 Wound Potential. It’ll also have an armour reduction of (-2), but I’ll assume the armour is hardened so this washes out.
We have two targets, both of the same SM: The first one is unarmoured and has just its Robustness of SM + 7. The other one mounts two Nanocomposite systems, for a total Armour Potential of SM + 6.
Unarmoured Target
Firing a major battery at the unarmoured target means SM + 6 WP vs SM + 7 Robustness, for a -1 severity injury. That makes it Reeling; it is pretty damaged. You need four hits to force a death check.
A spinal battery requires one hit; a medium battery 4; a secondary 8; a tertiary, 16. Of course, the medium/secondary/tertiary battery fires 3/10/30 shots; therefore, it’s more efficient to kill an unarmoured spacecraft with smaller guns.
If we take an SM+10 spacecraft, a contact-detonated 25 kiloton nuke will inflict a Severity +6 wound, for total destruction. In proximity detonation mode, it will only inflict a Severity-6 wound, so nothing too bad. You’ll need a 2.5 megaton weapon to inflict meaningful damage (Crippling) with a proximity detonation. In fact, proximity detonation seems to almost never be worth it: The best you can do is increasing your hit probability from 0.5% to 16.2%, for 30 times fewer misses. But each actual hit is worth so much more as a contact detonation it’s far better to throw away 29 warheads and contact detonate one rather than having 30 hits that fail to do meaningful damage.
Armoured Target
Firing a major battery at the armoured target means SM + 6 WP vs SM + 7 Robustness and SM + 6 Armour Potential. Armour piercing and hardening cancel each other out, leaving no damage.
If you’re using the damage roll rules, you roll vs 7 or less to increase wounding potential by one. That makes roughly a 1-in-6 chance to inflict damage; reduced by armour it becomes SM+3 WP, for a -4 severity. So you’ll need an expected 200 hits to force the first death check. No smaller battery can penetrate, but the spinal battery will penetrate and—without variable damage—be reduced to SM+3 WP for all attacks. That makes it just 32 hits for the first death check, better than the 100 hits three major batteries could produce in the same time.
For EM guns, a single hit will do SM + 9 WP if you’re firing from rest. That’s reduced to SM + 8 from armour, which is a Crippled result. Pretty bad. A missile hit simply obliterates it.
If you use a particle beam instead, the major battery will effectively reduce armour to SM + 4, which reduces WP to SM + 4, and injury severity to -3. You’ll need 16 shots to cause a death check. A spinal battery will only take 4 shots (both armour is less important and you do more damage). A medium battery will take 64 shots. The bigger weapons look good again.
Side-note: This essentially reproduces Transhuman Space space combat. Most combat spacecraft mount spinal particle beams; the bigger, the better. Lasers are secondary weapons, not enough to penetrate front armour.
Again, an SM+10 spacecraft is simply obliterated by any nuke that contact-detonates. But even a 2.5 megaton weapon will need four proximity detonations to get to that first death-check.
Remember that each beam from an X-ray warhead will do 13(-4) wounding; against an SM+10 spacecraft with 17 Robustness and 16 hardened Armour, that will not penetrate.
Summary
What this exercise has shown quite clearly is that (a) kinetic weapons just scale so differently, and (b) it’s actually possible to armour against non-kinetic weapons.
What next? Well, I have an idea for changing the Spaceships design system to take volume into account (and no longer have armour as systems).