Side by side
| Drive | Speed | Payload | Main obstacle |
|---|---|---|---|
| Electric (ion / Hall) | tens of km/s | tonnes | Far too slow for the stars |
| Nuclear pulse | 3–5 % c | ≈ 1,000 t | Nuclear explosives in space, treaty ban |
| Laser light sail | ≈ 20 % c | ≈ 1 g | 100 GW laser array, sail materials, braking |
| Inertial fusion | ≈ 12 % c | ≈ 450 t | Repetitive fusion ignition, helium-3 supply |
| Antimatter-catalysed | tens of % c (concept) | ≈ 100 t (concept) | Antimatter production and storage |
Speeds and payloads are from published design studies and our own planning figures; they are orders of magnitude, not specifications.
Speed versus mass
Every interstellar concept trades speed against payload. A gram-scale sail can be pushed hard because there is almost nothing to push. A crewed ship needs the energy density of nuclear or fusion fuel, which today limits it to a few percent of light speed.