Different Scenarios

We did test the space combat system. But this was only one configuration of weapons - what other things can we change?

Scenario: Point Defense and Rapid Fire

As ericthered pointed out, a viable tactic might be to use the lasers on the Oberth as point defense, and rely on kinetics (with proximity detonation) to take out the AKVs.

Using the original AKVs, fire against the shells is vs -2 (shell SM) +2 (rapid fire), minus range modifiers. At point defense range, that’s another +12, meaning each of the Oberth’s rapid-fire lasers can easily destroy the one shell fired by each of the AKVs and it comes down to ramming.

Instead, let’s exchange the 12cm EM gun of the AKVs for a 6cm rapid fire one. Of the ten shots it fires per turn, only about half will be shot down. Rolling against 9 means that about 8 of the 20 shots hit, each doing 9dx30 damage. The Oberth’s armour still lets 246d through, and each of the shots is sufficient to kill it. Ouch.

I would also test X-Ray Laser ammunition; unfortunately, the Predator as written has a 12cm cannon, which is too small to fire that iconic Transhuman Space ammunition. Well.

Scenario: Particle Beam Parade

Let’s test the particle beam. With its (5) armour divisor, it should work quite nice against armoured spacecraft.

Firstly, let’s modify the secondary battery of the Oberth, replacing the four 100 MJ UV lasers with 100 MJ particle beams. Those have a range of 1050/3000km, and do 2dx5 (5) burn rad sur damage. They’re also less accurate at -3. In the example above, the Oberth can begin firing at its full range of 3000km, at a skill of 10.

Turn 1 The AKVs are 3000km out. All particle beams target the same AKV, hitting twice. Each hit is for 5d, of which the armour absorbs 3d. Aggressive Armadillo takes a total of 6 damage, and gets an armour system damaged.

Turn 2 2600km. Aggressive Armadillo is hit twice more, for another 13 damage. This damages a second armour system and the railgun.

Turn 3 2200km. Brave Beaver is attacked, with no hits.

Turn 4 1800km. Brave Beaver is hit four times. A total of 24 damage, destroying two armour systems.

Turn 5 1400km. Brave Beaver is hit twice, for 10 damage, and is now at negative HP. Another armour system and the EM gun are disabled.

Turn 6 1000km. Both of the undamaged AKVs are hit once. No longer at half-damage, they are hit for 10d, minus the armour’s effective 3d. Curious Crow takes 26 damage and loses two armour systems. Dangerous Dalmatian takes 22 damage and also loses two armour systems. The AKVs fire two shots.

Turn 7 600km. Curious Crow takes a total of 32 damage, but manages to not get destroyed. However, its EM gun is destroyed. Dangerous Dalmatian does not survive.

Turn 8 200km out. Two more AKVs are destroyed by the particle beams, and I’m going to say the last one died from RF lasers.

Turn 9 The two shots fired by the AKVs arrive. Again rolling against 9, both fail to hit.

Summary Far closer. It also was significantly faster to play, mostly by discounting the 10MJ lasers and armour damage. And remember, only 2% of the Oberth was spent on anti-AKV weaponry.

Missile Spam

Now, we’ll change another thing. The consensus is that missile weapons rule everything in GURPS Spaceship’s combat system. Let’s therefore modify the AKVs to fire missiles. They’re now the space-equivalent of a missile boat - and since they’re supposed to stay out of range anyway, we’ll drop most of the armour and can mount eight missile launcher systems. Uhm, wow. That’s a lot of missiles - eighty 16cm missile launchers, with a total ammunition of 400 missiles! Each of the 1600 SM-1 missiles the four AKVs bring to bear weights 66 kg and costs $66K. In total, those 1600 missiles cost over $100M - far more than the AKVs, and this brings the total cost for the AKV’s side to about $160M.

What kind of performance do the missiles have? According to SS3:36, each missile has 5G acceleration and 15km/s deltaV That means the Oberth is unable to avoid them by straight acceleration, and would have to run them out of deltaV.

To make it fair, let’s also replace the Oberth’s four 10MJ RF UV lasers with twelve 300kJ VRF UV lasers. Range is 1000/3000km, damage 1d+2. Not that it matters against missiles.

The AKVs launch at 5000km distance, at a closing speed of 20km/s. The missiles use 10km/s of their deltaV to accelerate to a relative 30km/s; everything else is spent on countering dodges. They will impact in two minutes, forty seconds.

Turn 1 Distance 3000km. 1600 missiles left. Roll is at -8. Rapid-fire brings that up to effective skill-11. Eight missiles are hit.

Turn 2 Distance 2400km. 1592 missiles left. Roll is at -8, skill-11 with rapid fire. Nine missiles hit.

Turn 3 Distance 1800km. 1583 missiles left. Roll is at -7. Each gun divides fire between two targets, for effective skill-9. Eleven missiles hit.

Turn 4 Distance 1200km. 1572 missiles left. Roll is at -6. Again dividing between two targets, 14 missiles are hit.

Turn 5 Distance 600km. Last chance for non-PD fire, and there are still 1558 missiles left. Roll is against -4. Dividing rapid fire between three targets for an effective skill-9, 18 missiles are hit - but there are still 1540 missiles left.

Turn 6. Point defence. Range penalty is +12. Including -1 SM penalty, effective skill without rapid fire is 25. Dividing the fire between 7 targets per gun is -16 from splitting fire, and +3 each for rapid fire. Effective skill is 12. 78 missiles are knocked down; far too few to make a difference.

Most of the missiles are going to hit (to-hit roll is at +5 without proximity detonation), and each does 6dx4x30, or 740d damage. An exemplary 2647 damage (from one missile) easily vapourizes the Oberth. In fact, we could have easily killed the Oberth with 200 missiles.

Summary Boring. The AKVs fired their missiles, the Oberth could never even hope to intercept all of them, and any hit kills it. The image of an AKV firing hordes of what are essentially slightly-lighter sidewinders as main anti-spacecraft weapons just doesn’t really fit - nor does the fact that the best weapon for point defence would be a peripheral battery of 500kg VRF lasers, of which the Oberth could mount 300.

In an analogy, this would be like attacking a WW2-Fletcher destroyer with 1600 Hellfire missiles (each of which completely destroys it), and the best defense is to mount 300 Miniguns and fire away. That’s not satisfying to me.

Rule alternatives and modifications

Missile Shield SS3:35 gives us the Missile Shield switch, which allows point defence weapons to kill as many missiles as they have shots. In the example above, that would be 1200 - not quite enough to survive, but again, the Oberth devotes only 2% of her mass to anti-missile weaponry.

Larger Missiles The dual issues of too many missiles and too light weapons could be solved by using larger missiles. For that, we’ll model the missiles as 3t (i.e. SM+3) spacecraft. Each missile-AKV could then launch eight missiles. Those mount one warhead and one control room system, two armour systems in the front (for a total of 1d+2DR), three HEDM engines (6G) and thirteen fuel tanks (15.6km/s deltaV). We’ll assume that any penetrating hits will disable the missile (HEDM fuel is volatile). Since we’re using armour-as-dice, this directly tells us which guns will never kill a missile, and which ones will kill one with each shot.

In this example, they are immune against beams of up to 300kJ; using four 1MJ VRF beams (less than one weapons battery), the Oberth rolls against skill-15 (eight missiles per laser. PD is at +12, +2 from rapid fire, a total of -16 for multi-tasking and +3 from SM, for a total of +1) when defending from a launch by four missile-AKVs. This means it’ll have a 25% chance of shooting down all missiles in the final defence phase. If one includes previous turns’ defences, they’re easily able to avoid the missile attach.

Looking at the performance, these missiles have a powered range from rest of two million kilometres, which they reach after 260 seconds at a speed of 15.6km/s. This could be stepped up further by reducing acceleration (10 million kilometres at 10m/s, for example), but against any evading target you lose far more deltaV by them evading.

Counter-Missiles The Oberth could also mount nuclear counter-missiles. With Spaceships assuming that nukes damage everything in a 15km radius, they should be able to kill several incoming missiles with each one. To avoid multi-kills, the 1600 missiles above would have to be spread out into a circle more than 1200km wide, moving perpendicular to the target spacecraft - but the ones at the edge would take almost four minutes at full acceleration to hit the target.

If we assume the missiles begin converging a minute before impact, they can cover 90km distance (and pay 3km/s for that), which means an average distance of 2.25\,km between missiles. Fifty defensive, nuke-tipped missiles are enough to blanket that area and destroy all incoming missiles.

This would definitely help to kill large missile swarms, but would at the same time also kill every other approach - it now becomes a game of mounting the smallest possible missiles, and engage in a battle of attrition. That’s not what we want.

Summary In summary, we assume that the heavier missiles are a product of the vulnerability of smaller missiles even against light weaponry. This pushes everybody to bigger missiles - three tons should be at the lower end.