The Margin

Out in the dark, a ship is a closed loop of power and heat with a number on it. That number is the margin.

Everything a ship does draws on one pool. Thrust, air, computation, keeping a human body and the hull above the temperature where things fail — all of it is the same currency, because power and heat are the same currency out here. Waste heat is as much a problem as cold: a hull in vacuum sheds warmth only by radiating it slowly, so running hot is its own way to die. The margin is the single reserve that holds all of this up at once.

It does not refill in transit. You leave port with what you can carry, and you arrive — or don’t — on what’s left.

This is the arithmetic under every decision made in the long dark. Spend the margin on one claim and you have it for nothing else. There is no bank, no line of credit, no neighbor to borrow from at the distances a working tug crosses. A pilot who wants to keep something warm that isn’t herself is not being generous in the abstract; she is moving a number from the column that gets her home.

Salvors talk about the margin the way sailors once talked about the weather — constantly, superstitiously, and with the respect owed to the thing that decides.