New Component: Fusion Torch

Remember: Our fusion torch (with water as a propellant) has an ISP of 15000s and TWR of 2. High-thrust mode increases this TWR to 20 but decreases ISP to 1000s. Medium gear is TWR of 8 and ISP of 3,000s.


As the last time, an LSDV-5 (Herman Oberth) is used. They have cDR of 70/10/5 of metal matrix composite armour, and a cPF of 10/2/1. I’m ignoring the need for a jump drive at the moment. It has a Required Radiator Area (RRA) of 60, and radiator areas of 15 (hull) and 60 (folding wings).

Originally, they would have 120 spaces of HT of antimatter pulse drive. Replacing this with our fusion torch, it increases thrust from 960t to 1,440t, 5760t, or 144,000t. Replacing the corresponding tanks (300 in total) from nuclear pellets to water changes loaded mass to 8900t. This gives a thrust of 0.16g, 0.65g, or 1.52g, increasing to up to 3.27g for a completely unloaded craft. Note that it runs through its propellant supply in less than three minutes at full thrust.

Delta-v (for which I’m using the actual rocket equation instead of the approximation in THS) is 47.5km/s - or 3.17km/s at high thrust.

As a reminder: The SDV is armed with 4 10-MJ laser towers, 4 2.5MJ towers, and a coilgun (with ten munitions packets). Do note that it does not mount a particle beam like other designs. We’ll have to do a separate test for those.


Taking the same AKV design as last time (SIM-7 Predator-Class), we get cDR of 70/5/20, cPF of 5/1/2 (note that I reduced side armour). It is armed only with a coilgun bay and has one munitions pack in storage. The AKVs have a RRA of 1.5. Their Deployed Radiator Area (DRA) is 1.5 with extended radiator, 1.0 without.

We replace the 2.5 compact HT fusion pulse drive with compact fusion torches for an increase in thrust to up to 450t and the tank with water (22.5t total), increasing loaded mass to 118t. Acceleration is 0.38g, 1.52g, or 3.8g, and total delta-v 14.22km/s. This time, it can consume all of its fuel in less than a minute. Clearly, all of the designs could do with a bit more fuel…

The Encounter

In order to make everything more compatible with THS rules, I’m using 100 second turns for now. As last time, the engagement takes place at 20km/s relative velocity. It starts at a distance of 12,750km, the extreme range from THS. All spacecraft have spent 5km/s (500 burn points) of their dV, leaving the SDV with 4250 and the AKVs with 922. That’s burn points at high efficiency - high-thrust costs 15x as much, medium-thrust 5x.

The AKVs retract their radiators - nothing they mount needs much energy, so they can easily sustain it. The SDV doesn’t - nothing the AKVs mount can damage radiators at beyond 4,000 kilometres anyway.

Turn 1

Distance is 12,750km, for extreme range. At that range, only the heavy lasers can fire. They each do 2dx5 damage at this distance, modified by the result of the gunner roll. All of them concentrate fire on the first AKV. Gunnery roll is 10, for normal damage, and they roll (4, 6), (5, 4), (5, 4), and (5, 3) - all of them are absorbed by the armour. However, there’s one rolled six in it, and that means AKV A just lost 1ksf of hull radiator. It’ll have to rely on its folded one, now.

Turn 2

Distance is now 10,750km, still extreme. Repeating the exercise, all four heavy lasers concentrate on AKV B. However, this turn’s gunnery roll is a critical failure, at 17. No chance to penetrate armour. The damage rolls turn out with 4x6 and 2x1, destroying its hull radiator. If the AKVs had laser towers, those would’ve been destroyed too.

Turn 3

Distance is 8,750km, now in long range. Aside from the heavy lasers (now at 2dx10), the light lasers (halved at 1dx5) can join in - but they have no chance of penetrating the armour. The light lasers (gunnery roll doesn’t matter) roll 1 six, damaging the third AKVs radiator.

The heavy lasers, which had concentrated on the fourth AKV, roll an 8 for a successful gunnery roll. They do 90, 90, 60, and 90 damage. Three of them penetrate with 20pts, doubled to 40 “injury”. Against the AKV’s cHP of 84, that’s four rolls on the major damage table. Rolls are

  • 14: Drive Damaged: Acceleration is halved.
  • 17: Life support damaged: It’s uncrewed anyway.
  • 9: Originally Occupant Injury, but changed to Weapon damage instead. The coilgun is disabled.

Turn 4

Distance is 6,750km, still long range. With AKV D damaged, fire now concentrates on the first one again. Light lasers are truly useless now; all of the surfaces have been scoured clean.

The heavy lasers split targets to the first two AKVs and roll a 7 and 8 (normal cDR). The first AKV is hit by 50 and 100 damage, for 60 injury after armour. Acceleration is reduced to half, and we roll five times on the major damage table. One of these hits the bridge, and the AKV is crippled (no backup).

The second AKV is hit by 110 and 80 damage for 100 injury after armour. It is disabled.

Turn 5

Distance is 4,750km. Last turn at long range; the SDV begins retracting the radiator. Heavy laser turrets target the AKV C, rolling a 15. That’s a failure by one, and the effective armour is doubled. None of them penetrate.

Turn 6

Now it gets interesting. At 2,750km and therefore effective range, the AKVs can retaliate with XLMP packages. At the same time, the SDV’s secondary lasers are now doing full damage at 2dx5. Still cannot penetrate the armour, though.

The last remaining AKV with a weapon fires the first shot. Gunnery roll is 13, meaning normal armour. The XLMP does 2dx5(2); it rolls a damage of 25. One of those rolls is a 1. There’s a question in the rules here: Whether a side-mounted laser tower could be disabled by an attack from the front. Going to go with “yes”, here; one of the heavy laser towers is disabled.

The remaining three concentrate on AKV C. Normal-damage gunnery roll, and they do 50, 40, and 50 damage - failing to penetrate. It accumulates 45 heat points.

Turn 7

At only 750 kilometres distance, this is the last turn before ramming. Distance is still effective.

AKV C fires its XLMP again, doing 15 damage. Doesn’t penetrate, but disables another heavy laser.

The SDV fires its two lasers at AKV C. Again, it rolls badly - 30 and 50 damage. No penetration, and now at 90 heat points.


Ramming itself is a special action in THS. Both AKVs spend the maximum available burn points (both at medium gear; acc of 152 for AKV C, costs 760, and 76 for AKV D, costs 380) for +11 and +9 respectively, as does the SDV (150 burn points at medium thrust, costs 750, for +11).

The first AKV rolls a 7, for a MoS of 18 while the SDV rolls 11, for MoS of 13. The quick contest therefore went to the AKV with a margin of 5. The SDV has a size of modifier of +5, therefore a margin of 11 would be needed - the AKV has missed.

The second AKV rolls 14 with the SDV rolling 13; that also doesn’t suffice.

Turn 8

Now at close range and - crucially - no longer facing the front, AKV C fires an XLMP. This does 4dx5(2) damage, and it triggers it against the SDV’s rear. Armour is 5, which is halved after the successful gunnery roll. Damage is then 55, for injury of 104. That’s not enough to trigger a major damage. But it does manage to disable another heavy laser tower.

The SDV fires its heavy laser at AKV C, again not managing to penetrate the armour. Distance is now 250km. It also turns to present its front to the AKVs. Heat points at 135.

Turn 9

Both AKVs begin thrusting, pointed towards the SDV, and trying to reduce relative speed. Except they don’t have enough dV to do so, having spent most of their remaining fuel during the ramming.

AKV C fires another XLMP; this unfortunately is too far away for full damage and the 30 damage does not penetrate.

The SDV fires its heavy laser again, for 55 damage. Yet another turn with no penetration. 180 heat points - capacity is 240.

Turn 10

AKV C is at 3750km, AKV D at 4000km. Distance is long for both, and XLMP won’t work anymore. The SDV’s laser turret does, though. And finally, it manages to penetrate the armour, doing 90 damage. That’s 40 injury, for three major damage rolls. This damages the coilgun, drive (half acceleration), and some of the cargo. The SDV re-extends its radiators.


I’m going to stop this right here - both remaining AKVs are badly bloodied, and will be killed without being able to approach again.

In summary, the SDV has survived the encounter, the AKVs haven’t. On the other hand, while the SDV has not suffered heavy damage, three of its four heavy lasers have been disabled. On the other hand, this was $800M of SDV against $124M of AKVs - and the introduction of two or four more AKVs would probably have been decisive.


Kinetic Attack

What if, during turn 8, we would have used a KKMP? The SDV is hit three times. Realistically, this should be against the front armour; damage is 1dx28 per hit. Two hits do 84 damage before armour, for a total of 28 injury. Clearly, worse than the XLMPs.

Successful Ramming

Ramming is often said to be decisive during such combats. If the AKV would have hit, its damage would be 3dcHPRV, for 3d8427 damage. Rolls of 5, 2, and 6 do a total of almost 30,000 damage and vapourizing the SDV.

Particle Beams

What if the SDV would have a single particle beam? A 60 metre accelerator masses 80 tons and takes 16 spaces. Against the cPF of 5 from the front, it does 4dx200 damage. On turn 3, that would be half-damage, doing 600 radiation damage. Turn 4 increases this to 1,800, turn 5 to 3,600. On turn 6, first at effective range, it’s increased to 5,600 and has the first roll for radiation damage; it manages to disable the unmanned controls and the ladar. One out of the fight. Turn 7, and it does 2000 radiation damage to another target.

In summary, it’s not greatly effective; those 80 tons could have bought another four heavy laser towers which would arguably helped more.


Well. It has been rather tense, so that is something that I liked. On the other hand, it appears quite difficult to ram other spacecraft. I’ll recheck the rules on this, maybe I missed something. Other than that, though, I really liked it.