Ostranauts Reactor Guide — Fusion Torch Without the Fire
✔ Last checked: 2026-08-04
Ostranauts has exactly one reactor type — an Inertial Confinement Fusion torch burning He3 and D2O — and starting one is a genuine 16-step procedure, not a power button. One launch-window reviewer put it perfectly: learning to assemble and start a reactor properly takes “about 20 hours of real life instead of 10 years. Progress!” Here’s the map so it takes you less.
The parts list
Component names below are from the official wiki; individual prices and stats are being re-verified for 1.0.
| Role | Component |
|---|---|
| Core | IC Fusion Reactor Core (Sulaiman “TW”-class) |
| Containment | 2x Fusion Field Coils Assembly |
| Fuel path | Pellet Feeder Assembly, Reactor Fuel Regulator, He3 + D2O canisters |
| Ignition | Laser Array Assembly, Fusion-Grade Laser Capacitor |
| Cooling | Cryo Reservoir + Cryo Distribution Pump |
| Power | Ship Battery (startup), optional MHD Generator (recharges batteries from plasma) |
| Optional | Fusion Core Pump (evacuates air before startup) |
The build wants a ~13x7 tile space; the coils occupy 5x5 with the center tile removed so the core sits over vacuum. A dedicated Reactor Room also boosts your ship’s sale value.
Startup, in phases
The wiki preserves the full official 16-step checklist — worth keeping open on a second screen. The phases, in order:
- Power: set the PWR bus to battery, run the lamp test.
- Vacuum: evacuate the core chamber to VAC. Skipping this is the classic failed-ignition (or worse) mistake.
- Ignition chain: laser alignment on, pellet feeder on, cryo cooling running.
- Containment and burn: energize field coils, bring the MHD generator online, ignite.
Fuel and running behavior
The documented mix skews heavily toward He3 — roughly one D2O tank per 13 He3 tanks, with minimums around 6.6 kg He3 and 4.45 kg D2O (wiki figures, re-verifying for 1.0). Under thrust, reactor temperature dropping is normal — heat leaves with the plume. Persistent overheating at idle means your cryo loop is undersized; see life support for keeping the rest of the ship from cooking.
Sourcing parts? Fusion components are among the most valuable salvage in the Boneyard — which is exactly why finding an intact set is rare.
FAQ
Is there a fission reactor in Ostranauts?
No — interplanetary travel runs on an Inertial Confinement Fusion (ICF) torch drive fueled by He3 and D2O. When players say 'reactor' they mean this fusion assembly.
Why does my reactor temperature drop when I thrust?
That's normal and documented: reaction heat is ejected as part of the thrust plume. If it drops too far, reduce your acceleration limit or add another laser/feeder pair.
How much space does a reactor need?
Wiki-documented footprint is roughly 13x7 tiles total, with the field coils in a 5x5 area whose center tile is removed for vacuum access. Being re-verified for 1.0.
Why won't my reactor start?
The most common misses: core not evacuated to vacuum before ignition, no cryo cooling running, power bus not set to battery for startup, or missing fuel canisters. Follow the official checklist in order.