Reactors and heat

An antimatter reactor makes power where no sunlight reaches. The big one will not run without a nuclear scientist aboard; the small one asks for nobody. Both make half as much heat again as they make power, and what that heat can be thrown into is what decides the rest of your ship.

A plant instead of a panel

Every other source of power in the game is sunlight. Far from the Sun there is not much of it, and inside a warp bubble there is none at all. The AR-8 Antimatter Reactor is the answer: a uranium core lit by a trickle of antiprotons, making 0.6 u/s whether there is a star in the sky or not. That is two and a half SP-6 Twin Arrays in full sun, out of one part.

What it burns is antimatter, and hardly any: 1 μg every twelve hours. A full AM-8 Antimatter Container runs it for 2,040 hours, which is eighty-five days. A container launches empty, so every reactor is fed by a mine: the helium-3 chain on the Moon is the only place antimatter comes from.

It is switched on with Start up on its own sheet, or with the Running toggle in the hangar, and it stays as you left it. The core does not light at once: it comes up over 180 s, and the sheet counts it — Core coming up: 40 %. Shut it down and the core goes cold, so an emergency start is power three minutes later, not three seconds.

A core that is up stays up. Fly the ship, leave it for the space center, take control of it again a week later — the plant is still at full output, because it never stopped. The world keeps the core the way it keeps the fuel in the tanks, and it keeps running while the game is shut. Only four things put it out: Shut down, an empty container, the loss of the nuclear scientist, or fins that carry nothing. Any of those and the next start is another 180 s.

It needs a nuclear scientist

No other part in the game asks for one particular trade. The reactor does. Unless a living Nuclear Scientist is aboard the ship, the core stays cold and the plant makes nothing at all. A scientist will not do, nor an engineer, nor the best pilot in the programme. Its sheet says so plainly: No nuclear scientist aboard.

The reactor carries its own: one shielded seat beside the core, reserved for the trade. Only a Nuclear Scientist can be put in it, so a warp ship needs no extra cabin for the one Meek it cannot fly without. What runs the plant is broader than that seat, though: the reactor reads the whole ship, so a nuclear scientist riding in a Crew Capsule further up the stack works it just the same, and a second one in a Passenger Cabin is a spare.

Nuclear Scientists come onto the recruit board at the Astronaut Center's third level and cost 1,400 cr at par. See the trades and Recruit a Meek.

And the small one needs nobody

A probe has no room for a Meek and no reason to carry one, so the AR-4 Antimatter Reactor is the same core at a quarter of the size with the room taken out of it: no seat, no trade, nothing to find. It is on the 4 m stack, the same width as a WC-4 Warp Coil, and it is sold first: Antimatter Power on tier 4 sells the AR-4, a tier after the small mine that fuels it, and the AR-8 waits on tier 5's Crewed Reactors.

What you pay for that is output. It makes 0.12 u/s against the AR-8's 0.6, and it burns a microgram every thirty-two hours rather than every twelve — nearly twice the antimatter for each unit of power. That is enough for a Warp Coil and the container feeding it, and not enough for a Warp Ring: the bigger bubbles stay the crewed ship's. Inside a wall the plant burns for the whole span skipped, so on one AM-8 a Coil probe has about 136 days of drive and plant together, and on one AM-4 about forty.

Its waste heat is 12 kW, so one water fin carries it and a Coil together under an open sky. Everything else below — the throttling, the wall temperatures, the fact that it runs while you are away — is the same for both plants.

Heat is the ceiling

The reactor makes 60 kW of waste heat against the 40 kW of power it delivers. A ship in space has no air to carry heat away, so the only way to be rid of it is to radiate it, and the only parts that radiate it are radiators — fins of hot metal folded against the hull and swung out when they are needed.

The game adds up the heat every part aboard makes, adds up what every deployed fin aboard can shed, and divides. Whatever share of the load your fins carry is the share of full output the reactor is allowed to make. With fins for half the heat it runs at half power, and its sheet says which: 0.30 u/s — held to 50 % by heat. With no fin at all it makes nothing and reads No way to shed 60 kW: deploy a radiator.

It never overheats and never explodes for want of cooling. It is simply held down to what the ship can carry. A stowed radiator is a lid and sheds nothing, and one halfway out sheds half.

A fin only sheds into a colder sky

A radiator throws heat at whatever sky it is under, and it only works while the fluid in its pipes is hotter than that sky. In open space the sky is as cold as anything gets, so every fin runs at its full rate. Inside a warp bubble the sky is the bubble's wall, and each drive's wall has a temperature of its own. A fin cooler than the wall sheds nothing whatever.

How much a fin sheds climbs as the fourth power of the fluid inside it. That is why the three radiators are not three sizes of the same thing: doubling the temperature is sixteen times the heat, so each rung of the ladder is a step change.

The three walls in that table are the three warp drives: 350 K is a WC-4 Warp Coil, 600 K a WR-8 Warp Ring and 800 K a WL-8 Warp Lattice. Every radiator's info card carries the same four rows, so you can read off which bubbles a fin can live inside before you buy either part.

So the ladder runs: water pipes under a Coil and nowhere hotter, potassium under a Coil or a Ring, sodium under anything including a Lattice. Picking the drive picks the radiator.

How many fins

Outside a bubble the sky is the open one, so the open-sky column is what your reactor is judged against in ordinary flight. Three RW-3 Water Radiators carry a reactor there; one RK-6 or RS-8 carries it several times over.

Forming a bubble is where the wall bites. The game will not let you close one your ship cannot shed into, and it counts the drive's own heat as well as the plant's.

A fin is fragile once it is out. Every radiator is rated for 2 g and a 0.5 m/s touch while open, against the hull's own figures while it is latched. Deploy them above the air and stow them before you burn hard or come down, exactly as you would a solar panel. See Deploy a solar panel: a radiator opens the same way.

It runs while you are away

A reactor left running goes on running when you leave the flight or close the game, the way a mining rig does. It keeps burning its antimatter and keeps making its power. An AR-8 also keeps needing its nuclear scientist: take that Meek off the ship and the plant goes out. An AR-4 has nobody to lose.