Space Combat
Light-lag, thermodynamics and the rocket equation — why space fights nothing like atmosphere.
Light-lag is the defining fact
Vacuum removes wind, drop and drag. It replaces them with harsher constraints. Sensors show you where a target was, and at real engagement ranges that is a targeting problem rather than a footnote.
| Range | Light delay | Railgun flight time | Target drift at 1 g |
|---|---|---|---|
| 10 km | 0.0 ms | 1.7 s | 14 m |
| 100 km | 0.3 ms | 16.7 s | 1 km |
| 1,000 km | 3.3 ms | 2.8 min | 136 km |
| 10,000 km | 33.4 ms | 27.8 min | 13625 km |
| 100,000 km | 333.6 ms | 4.6 hr | 1362500 km |
| 1M km | 3.3 s | 46.3 hr | 136250000 km |
Unguided fire has a very short leash
A railgun slug fired at 10,000 km takes nearly half an hour to arrive, during which a ship under 1 g drifts thousands of kilometres. Beyond a few thousand kilometres, unguided fire is not aiming at a ship — it is aiming at where a ship has no particular reason to avoid being.
Three consequences fall out rather than being designed in: guided weapons dominate at range, point defence is the real battle, and closing to knife range is a deliberate tactic rather than a failure of nerve.
There is no stealth in space
A ship must radiate its waste heat or cook its crew, and radiated power against a 2.7 K background is detectable at absurd range.
| Radiator temp | Area | Radiated power | Detection range |
|---|---|---|---|
| 300 K | 100 m² | 0.0 MW | 0.1 AU |
| 600 K | 500 m² | 3.7 MW | 1.1 AU |
| 1200 K | 1000 m² | 117.6 MW | 6.5 AU |
| 2000 K | 2000 m² | 1814.5 MW | 25.4 AU |
Detection ranges assume a generous sensor threshold; the order of magnitude is what matters. Even a cold ship is visible across the inner system.
Stealth in space is a thermodynamics problem, not a technology problem, and C.A.T.S. treats it as one. What is achievable is ambiguity — being one contact among many, hiding your vector, masquerading as cargo. Never invisibility.
Delta-v is the real currency
Movement is not limited by speed but by budget, and the rocket equation is unforgiving:
Δv = Isp × g × ln( wet mass ÷ dry mass )
| Mass ratio | Chemical | Nuclear thermal | Fusion torch |
|---|---|---|---|
| 1.5:1 | 1.8 km/s | 3.6 km/s | 39.8 km/s |
| 2:1 | 3.1 km/s | 6.1 km/s | 68.0 km/s |
| 3:1 | 4.8 km/s | 9.7 km/s | 107.8 km/s |
| 5:1 | 7.1 km/s | 14.2 km/s | 157.9 km/s |
| 10:1 | 10.2 km/s | 20.3 km/s | 225.9 km/s |
A manoeuvre that burns delta-v is a resource decision with campaign consequences — exactly the persistence the design brief asks for.