Ostranauts Fusion Reactor Guide

Core vs peripherals

The Reactor Core is four quarters installed over a Field Coils Assembly (two stacked parts). Twelve feed ports around the core accept peripherals — pellet feeders, laser arrays, capacitors, fuel regulators, pumps — with flexible placement. The control terminal on the core is where you run purge, fuel, and bus modes.

Why batteries sit on the input side

The core needs external power before it can fuse anything. Connect a ship battery to the input port (inward-facing red arrow on the wiki install diagram). Once running, the output port feeds the MHD generator's production back into the grid — often through more batteries acting as buffers.

Salvage vs buy

Boneyard derelicts often carry partial Sulaiman kits — a regulator without a feeder, or a cracked laser array. The salvage guide priority list ranks fusion parts near the top for resale value. Buying Fusion Parts cargo at stations fills gaps when RNG refuses to spawn a capacitor.

Install order on feed ports

Peripheral placement is flexible — the wiki explicitly says parts need not touch each other — but practical builds cluster fuel regulator → pellet feeder → laser capacitor → laser array on adjacent ports so conduit and maintenance paths stay short. MHD generator placement matters most: prioritize the port closest to your output arrow and battery bank.

Power draw while idle vs firing

Idle draw keeps CRYO, control systems, and magnetic pumps alive; ignition spikes laser cap recharge and pellet injection. Size battery banks for the spike, not the idle tick. If your PwrViz overlay shows scrubbers dipping when LAS CAP charges, add storage or stagger startup until life support is on a protected breaker.

Read draw before you expand

Use the PDA PwrViz cartridge or the reactor control UI output meters. Community reactor videos commonly cite ~100+ kW charge rates on healthy setups — but your hull's total draw must stay below sustained output or batteries bleed dry. Add a bank before you add a second scrubber deck.

Brownout symptoms

Doors stuck open or closed, scrubbers silent, nav rebooting, transponder refusing ON — all classic low-bus symptoms. Life support failure kills crew faster than debt collectors; see life support guide for priority loads.

Battery bank placement

Put storage between reactor output and the rest of the ship — a dedicated "e-room" adjacent to the core minimizes conduit length and heat bleed into crew quarters. Many optimal layouts use two banks: one on reactor input for startup isolation, one on output for load buffering.

Breaker panel zoning

Split branches logically:

• Do01Life support branch — scrubbers, O2 pumps, heaters (never share breaker with optional luxuries)
• Do02Avionics branch — nav console, transponder, antenna
• Do03Utility branch — doors, lights, workshop fabricators
• Do04Propulsion branch — RCS intake regulators (electric control, not the gas itself)

Signal boxes for soft switching

Signal boxes connect to device outputs and behave like software breakers — main breaker off kills all connected loads; individual toggles re-enable one device. Chain boxes with AND/OR logic if you want "reactor on AND life support armed" interlocks. KosGames' signal box primer matches in-game behavior: infinite outputs, eject severing, logic gates for multi-input setups.

Sample footprint (text blueprint)

Imagine a rectangular e-room: south wall lined with D2O and He3 tanks; east and west feed ports carry paired laser arrays and capacitors; north side hosts MHD generator output wired into a battery bank; corridor door bridged with double conduit paths overhead (as shown in recent 1.0 let's-play reactor episodes). Field coils sit dead center with a one-tile maintenance gap for EVA repairs.

Torch drive coupling

When the ICFR doubles as a fusion torch main engine, the same core room feeds interplanetary burns. That integration is why the 13×7 footprint matters — you are building a propulsion bay, not a closet generator. Keep main-engine fuel plumbing visually separate from life-support breakers so a burn checklist does not accidentally kill scrubbers mid-transit.

Startup heat spike

The purge-and-ignite sequence (next section) deliberately stresses the core. Run CRYO cooling on laser assemblies, keep CORE PURGE off once vacuum is achieved so you do not suck fuel back out, and watch pressure indicators until they read VAC. Skipping vacuum leads to failed ignitions and wasted D2O.

Sustained operation

He3 burns faster than D2O — the Fusion wiki recommends roughly 1 D2O tank to 3–13 He3 tanks for extended torch travel. Before ignition, verify fuel readouts meet minimums (He3 > ~6.6 kg, D2O > ~4.45 kg). If core temp keeps rising while output flatlines, check MHD connection, laser alignment (LAS ALIGN), Cryo ON, and Ablative Core Liner condition.

Heat vs habitable decks

Do not put crew bunks directly above the core unless you enjoy CO2 headaches. Route habitation one pressure door away, with scrubbers on a protected breaker branch so reactor experiments cannot suffocate the ship.

Why RCS brownouts still happen on fusion ships

Players expect unlimited power once the ICFR hums — then RCS refuses to fire during a dock because the avionics breaker tripped or the battery input was switched to charge mode incorrectly. Keep RCS regulators on a branch that stays powered during reactor bus changes.

Main engines vs reactor fuel

Torch drives consume the same D2O/He3 family as the reactor. Long burns drain tanks you sized only for electrical generation. Cargo runs for Fusion Parts, He3, and D2O become routine — budget mass on the hull accordingly.

Optional vs essential

Core Pump is optional in vacuum (speeds purge). MHD is optional for thrust-only but required to charge ship batteries. Cryo Pump + Reservoir are essential for closed-cycle power — running without cryo overheats, burns the Ablative Core Liner, and can explode the reactor.