Orbital Voyager

A spacecraft launches into a small solar system (one sun, four planets in circular orbits, and a belt of twelve asteroids) and has to visit four beacons scattered across deep space. The mission has a twenty-year clock and a fuel budget, and one wrong turn flings it into the sun, into a rock, or off the edge of the map. Every body, the rocket included, is exactly as big as it is drawn, so a pass that looks like a hit is a hit. The Genetic Algorithm (GA) decides what to do at every step of the way.

How it works

1. Each Reset reshuffles the seed. The same physics applies every time, but the launch pad and the beacons move, so a plan from one run won't transfer to another.
2. Every 0.1 simulated years the rocket gets a new burn. A fresh GA runs on our servers while the rocket coasts, searching over candidate burns (a direction and a magnitude) from where the spacecraft will be, with the fuel it has left.
3. The browser scores every candidate by simulating the next several months of flight through real Newtonian gravity. Sun crashes are heavily penalized, planet and asteroid crashes less so, and progress toward the nearest unvisited beacon is rewarded.
4. The server picks the best burn and sends it back. The rocket applies the impulse and continues until the next decision point. This is closed-loop control: the GA always sees the live state, instead of trying to plan the whole mission in advance.
5. Each candidate has only two genes (burn direction and magnitude), so each inner GA converges in just a few generations and a fraction of a second.

What to watch

• Trails fan out from the craft while the GA plans. Blue ones are safe candidate burns and the gold one is the current best. Red ones end in a crash, with an X where they hit. The launch is planned slowly so you can watch it: the first rounds are mostly red, and evolution finds a safe launch before the rocket flies. The Burn Plan panel counts the crashes in each round and in the whole mission, and says what the chosen burn is forecast to do.
• Once the rocket resumes, watch the beacons turn solid green with a check mark as the craft sweeps through them. The dashed circle inside each beacon is the real zone the craft has to pass through.
• Look for the trail kinking near a planet. The GA discovers gravitational slingshots (passing close at the right relative velocity to steal orbital energy) without being told they exist. Same trick NASA used to fly Voyager past the outer planets.
• Visiting all four beacons in one episode is the Grand Tour achievement.

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