Ostranauts reactor
Battery mode, D20, wiring, and the power bus: how to start the reactor and keep the ship alive.
Three inputs, one ignition.
Community documentation is consistent: a fusion reactor needs a D20 canister, an He3 supply, and a charged battery to start.
D20 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 D20 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.
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 D20 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.