Interstellar Flight

Why fly

Resources never cross a system's boundary, so a colony lives on what lies under its feet. No asteroid belt — no cheap metals; no ice — nothing to feed the colony. Supplies can't fix that. The only fix is to fly where the thing you need is, and that takes several real days.

One law

Every flight has three parts: acceleration, coasting, braking. The engine runs only at the ends, and at full power. In empty space nothing slows a ship down, so a long drift costs not a gram of fuel: you pay only to change speed. That is how a hop to the next moon works, and the road to another star. In combat the count is the same: inertia is free, a manoeuvre costs fuel.

Thrust, mass and fuel

The drive gives thrust, the reactor feeds it energy. A weak reactor will not let the drive open up. Spare power adds nothing: the drive takes exactly as much as it needs. The heavier the ship, the slower it accelerates.

Fuel burns, and the ship grows lighter. By the end of the road it brakes already light, so braking comes out shorter than acceleration. How much fuel to burn is up to you: less means a lower speed and a longer road. The peak speed is the one the ship can still stop from on the fuel it has left. The game will not let you fly somewhere you would have nothing to brake with.

Inside a system

Inside a system the course can be changed on the move. The ship keeps the part of its speed that points along the new course. If it is going so fast that it can no longer stop at the new target, the game says so before the turn. With empty tanks a ship can still crawl around the system on reserve thrust — very slowly.

An order that weighs like a decision

Between the stars the law is the same and the scale is different: acceleration and braking stay short stretches at the ends, and the drift between them lasts years. An interstellar course is set once: there is no turning point, and the course cannot be changed under way. You can change your mind only in the first minutes after departure — with "Call back the flight" on the road screen. The copy returns to the orbit it left, and the cells pay what was burnt by then twice: for the acceleration and for the braking. After that the only way is forward.

On the road a replicant is busy with the road: building, surveying and refuelling wait for arrival. There is one thing it can do — study, so set up a study plan before departure.

What has to line up

• The ship stands on the outer orbit. Interstellar departures leave only from there, and getting there inside the system takes days too.
• The target is visible on this system's star map. An observatory widens the radius.
• There is enough fuel to brake as well. A ship must be able to stop where it is going.
• The road fits into a week of real time. A longer way the game will offer to split: a nearer target or a faster ship.

The hull decides whether the flight happens

The hull sets the speed ceiling. Interstellar space holds roughly one hydrogen atom per cubic centimetre. At a fraction of light speed each of those atoms strikes the ship's bow like a particle out of an accelerator, and the hull holds that stream back with a shield field. No amount of thrust takes the ship faster than its field is rated for.

The starting hull is made for flights within a system, and it usually can't reach the next star within a week. Interstellar flight begins with the second hull and a good match of engine and reactor.

A hull is printed at a factory and fitted like any other module. The replicant stays itself: only the body around it changes.

Ticks and light

Ticks shorten the drift, but the road has a lower bound: no drive gets a ship there faster than light. Hit it and the game says so plainly: "physics from here on". And part of the road can't be bought off with ticks at all.

What is simplified on purpose

• Gravity does not bend the course. A ship does not fall towards the star and does not pick up speed at the giants.
• The drive gives its thrust straight in g. It is not derived from expelled mass, and the Tsiolkovsky equation stayed in the textbook.
• There is no relativity. At these speeds the onboard clock would fall noticeably behind the clock at home, and you would have to keep two clocks in your head. Everyone would get confused, starting with us.
• Sideways speed vanishes by itself in a turn. In real space it would have to be cancelled with the engine.

Everything a decision depends on stayed in: how much fuel to burn, whether you can stop in time, how long light takes. The rest is simplified so that a flight can be estimated in your head. How the same law works under fire is told in "Combat and Weapons".

Arrival

The ship lands on the outer orbit of the new system, and the system opens up: its layout, sites, finds and history. The first to arrive is recorded as the discoverer.

Think about the return ticket before you leave. Only a colony refuels a ship: the system needs a working fuel synthesis station — yours, an ally's or a neutral's (on the Exodus branches, see "Signals and Contact"). In an empty system the road back has to be built first. Fly where you intend to stay.