Ostranauts reactor
Battery mode, D2O, wiring, and the power bus: how to start the reactor and keep the ship alive.
Quick answers
- What does it need?A D2O canister, an He3 supply, and a charged battery to ignite.
- How do I start it?Load the fuel, set the power switch to Battery, let it ignite, then flip to Charge so the reactor recharges the batteries.
- Why won't it start?Work the usual chain: dead battery, wrong bus mode, or incomplete wiring: check those before blaming the core.
- Zero battery?No. Charge the battery at a station kiosk or swap in a charged one first.
Three inputs, one ignition.
Community documentation is consistent: a fusion reactor needs a D20 canister, an He3 supply, and a charged battery to start.
D2O canister
Heavy water fuel: check the canister is installed and not leaking.
He3 supply
The fusion fuel loop. Missing He3 means no sustained burn.
Battery charge
Ignition power. Dead battery = reactor will not start, even with fuel.
The sequence that works.
Based on confirmed by players steps.
- Install the D2O canister and He3 supply on the reactor core.
- Make sure a ship battery has charge; charge it at a station kiosk if needed.
- Switch the reactor to battery mode: the knob must actually be in battery position with speed unpaused.
- Once it ignites, switch the power bus to charge mode so the reactor recharges the battery instead of draining it.
- Verify circuits: many "won't start" reports end up being incomplete wiring, not a dead reactor.
The community parts list.
A fusion torch needs more than the core.
For a build-your-own reactor, players reference this minimum parts list (verified against 0.14-era community guides):
- 2x Fusion Field Coils Assembly
- 4x Reactor Core segments
- 1x Magnetohydrodynamic (MHD) Generator
- 1x Pellet Feed and 1x Fuel Regulator
- 1x Fusion-grade Laser Capacitor and 1x Laser
- 1x Cryo Distribution Pump and 1x Cryo Reservoir
- D2O and He3 supplies (Liq. He canister)
Install the field coils first on a 5x5 floor space, set the four core segments over them, then attach the support parts. The cryo and fuel tanks sit under the ship and need extra room. Keep the control panel accessible before wiring.
Inputs and outputs are not symmetric.
The most common community confusion.
Batteries have an input port and an output port. Station power feeds the input; a reactor feeds the output side. If the reactor runs but batteries stay empty, the bus is probably still in output mode: switch it to charge.
Also note: batteries should not drain while the reactor is in battery mode; if they do, check the bus switch and wiring before blaming the battery.
Common questions
Why won't my reactor start in battery mode?
The usual causes: the battery has no charge, the power bus is not switched to battery mode, or the wiring between battery, switch, and core is incomplete. One community report traced it to wrong wiring: after bypassing the switches and re-running cable over the core, it started.
What does a fusion reactor need to run?
Community guides list three inputs: a D2O canister, an He3 supply, and enough battery charge to ignite. The reactor then needs its fuel loop intact.
Why won't my batteries charge from the reactor?
Battery direction matters. Batteries have input and output ports: input typically receives station power, while the reactor charges from its output side. After starting the reactor, switch the power bus to charge mode.
Power is on but nothing works: is it a bug?
Check gas pressure and temperature first; powered devices still fail in a vacuum or a freezer. If O2 and temp are fine and circuits look right, a reload or checking the breaker/signal box state fixes many reports.
Can I start the reactor with zero battery?
No. The reactor needs starting power from a charged battery (or external feed). If the battery is dead, charge it from a station kiosk or swap in a charged one.
How do I charge a tool battery?
Install the matching charger: Battery Charger: Gott for Gott tools, Battery Charger: Halvorson for Halvorson tools, and charging stations for Bingham-12 EVA suits and Weber lasers. Connect the charger to power and confirm the battery model matches; a red battery in the wrong charger does not charge.
Why is my ship out of power?
Work the chain: dead battery, wrong bus mode, or incomplete wiring. If the battery is dead, charge it at a station kiosk or swap in a charged one. Then check the reactor's power switch (Battery vs Charge) and trace the cable run from battery to switch to reactor.
What does the power switch on the reactor do?
It selects the power bus mode. Community start order: put the middle switch to Battery for ignition, then flip it to Charge once the reactor runs so it recharges the batteries. Leave it in Battery and the batteries keep draining.
How do I build a reactor from scratch?
The community parts list: 2x Fusion Field Coils Assembly, 4x Reactor Core segments, 1x Magnetohydrodynamic (MHD) Generator, 1x Pellet Feed, 1x Fuel Regulator, 1x Fusion-grade Laser Capacitor, 1x Laser, 1x Cryo Distribution Pump, 1x Cryo Reservoir, plus D2O and He3 supplies. Install the field coils first on a 5x5 floor, place the core over them, then attach the support parts; the cryo and fuel tanks sit under the ship and need extra room.