The Setup

Similar to last time - except now, we’ll pit two SDVs against each other. Specifically, two modified Oberth-class SDVs from last time. I’ll remove the one multi-purpose system from the front and replace it with a full-sized weapon system. Each of the Oberths looks like this:

Front Hull System
[1-3] Advanced Metallic Laminate Armour
[4] Structural Reinforcement
[5!] Weapon System
[6] Habitat
[core] Control Room
Centre Hull System
[1] Advanced Metallic Laminate Armour
[2!] Secondary Battery (ten UV lasers)
[3-4] Fuel Tank
[5] Structural Reinforcement
[6] 3x external clamps
Rear Hull System
[1-2] Advanced Metallic Laminate Armour
[2-3] Fuel Tank
[4] Structural Reinforcement
[5-6] Water Fusion Torch (1.5g each)
[core] Fusion Reactor
TL Spacecraft dST/HP Hnd/SR HT Move LWt. Load SM Occ dDR FTL Cost
10^ Oberth 800 -1/5 12 3g/30km/s 3,000t - +9 12ASV 63d/7d/21d - -

Let’s test two different configurations: The first one, the Newton, mounts a full-size 20cm EM gun. Each hit does of one of these 60-kilogram projectiles does 3dx10xR damage (3dx0.3xR with proximity detonation).

The second, the Röntgen, instead mounts a particle beam. 3dx20(5), with a half-damage range of 2000km. Which of these is the better weapon? And remember: They both still have secondary particle beams with 3dx6 (5) damage and a range of… damn it, I made a mistake in the last post: Their half-damage range is only 1000km instead of 2000km. This would’ve made the Oberth lose more significantly. Anyway.

We’ll assume a closing speed of five kilometres per second (100 km per turn). At what kind of distance can we expect the combat to happen?

  • The Newton’s kinetics take a 1d-5 every turn in flight, and they’ll close in at a combined velocity of 20km/s, i.e. 400km per turn. The base modifier is 15 + 9 (SM) - 7 (sAcc) - 9 (relative velocity) + 2 (fixed-mount) = 10. Every turn gives another expected -1.5 to that, meaning they can fire (and hope for a lucky hit) at most four turns (plus one) flight time out - meaning 2000 kilometres range. Proximity detonation would increase that to about 2800 kilometres, but reduces damage to an effective 18d - that’s insufficient to breach the armour on the front or back.
  • The Röntgen is easier to compute - out to 2000 kilometres, it does 3dx20 (5) vs an effective front armour of 12d+2. That’s sufficient to easily penetrate the armour. Out to 4000 kilometres, it does 30d against the same, still penetrating. And out to 8000 kilometres, it’s 15d vs 12d+2. It still penetrates.
  • The secondaries do 3dx5 out to 1000 kilometres, slightly penetrating. Out to 4000 kilometres, they do 4d-1. That’s not sufficient to penetrate the rear armour, but it works against the side armour.

The battle

Luckily for the Newton, it can actually close the distance - if it accelerates, Röntgen faces the choice to either accelerate too, masking its particle beam, or fire upon the enemy and not accelerate. This starts at 8000 kilometres out.

  • Turn 1 Distance: 8000 kilometres. Closing speed: 5km/s. Röntgen fires for the first time, doing an effective 3d-2. In this case, that’s 13 damage. 787 damage left.
  • Turn 2 to 20 Newton continues accelerating, and has spent 11.4km/s dV on this. During that time, it is continuously bombarded by the particle beam, bringing it now down to 618 HP. It is now moving at a relative 16.4km/s, and the distance has been reduced to slightly over 4000 kilometres.
  • Turn 21 Newton now stops accelerating (it needs to remainder of the dV to avoid turning this into a suicide mission). Penetrating damage is now up to 3dx6-2, and Newton now takes 34 damage.
  • Turn 22 to Turn 26 Every turn, Newton takes more damage, the last turn especially damaging at 82 damage. It’ll get worse. Distance is slightly over 2000 kilometres. On the other hand, those effective five turns for the railgun impact now mean an effective range of about 3000 kilometres, so that’s quite nice. Newton has fired since turn 23, and the first shot is actually going to threaten on turn 27.
  • Turn 27 Röntgen fires, doing 3dx16-2 damage (in this case, 94, bringing Newton down to 134HP.) The first shot arrives. Malus from flight time is -8, bringing our target to 0 (a.k.a. impossible). Shot misses.
  • Turn 28 Newton takes another 126 damage, is now at 8. The next two shots arrive, with -4 and -2 modifier respectively. They roll against 6 and 8 respectively. Rolling 10 and 13, missing.
  • Turn 29 Distance is slightly over 1000 kilometres now; Newton now down to -86HP. The next two incoming shots take -3 and -1 (targets of 7 and 9 respectively). They both miss again.
  • Turn 30 Distance 768 kilometres. Newton reduced to -260 HP. Next two shots take -6 (that was unlucky!) and -1 respectively. Again, both miss (unlucky).
  • Turn 31 Distance 440km. Reduced to -402HP. One shot takes -2, the other has been fired close enough and doesn’t take any malus. And… both again miss. Wow.
  • Turn 32 Distance 112km. Reduced to 462HP. Both shots take no malus - and one, finally, finally, manages to hit. Röntgen does not manage to dodge, and takes 942d damage, reduced to 879d due to armour. It takes over 3000 damage, and has to roll three survival checks. It manages to make all of them.
  • Turn 33ff With the railgun velocity insufficient to overcome the velocity difference, Newton is unable to produce any more hits. Accordingly, it is reduced to a drifting hulk over the next turns.


Victory to the particle beam craft!

However, it could have gone differently, with a bit of luck - or maybe a rapid-fire kinetic gun. With these the Newton would have a gotten +2 on all of the to-hit rolls, which would have meant two shots hitting on turn 29 (both from the same salvo), doing 31d damage each (total of 217), and another hitting on turn 32 (115 damage). Nope, that did not help.

Still, this gives us a rough overview of space combat - SDVs are useful (and armed with particle beams and/or kinetics), but AKVs can also be used and can take out SDVs. More details would need a test run with an encounter between several spacecraft, but I’ll leave it for now.