Build consecutive encounters. Each flyby changes the vessel’s outgoing orbit, which determines which planet orbits it can reach next.

Sun-centered linear distance scale; markers are enlarged. Departure is a tangential impulse from Earth’s circular solar orbit. Sun-only propagation connects instantaneous, unpowered flybys. Planet phases are freely placed at encounter points, so this tests an idealized sequence rather than real launch dates. Rings, atmospheres, moons and multi-body perturbations are excluded. Positive solar orbital energy means Solar System escape, not escape from the Milky Way. Limit: 10 encounters, 80 years per leg.

Sources: NASA · Gravity assists · JPL

Plan a circular, coplanar transfer. The explorer date sets the starting planetary longitudes; ideal alignment places the destination where the spacecraft can meet it.

Gold: spacecraft. Blue: departure planet. Red: destination planet. Distance scale is linear; markers are enlarged. The thin line at arrival shows the miss distance when alignment is wrong.

Hohmann transfer model: circular orbits, impulsive burns and Sun-only gravity between encounters. Velocity changes are relative to circular solar orbits, excluding surface launch, capture, parking orbits and propulsion losses. Flyby output uses a patched two-body approximation. These are educational estimates, not real launch windows or flight plans.

Sources: NASA · Trajectories · JPL · Astronomy Engine

Bend a spacecraft’s path around a moving planet. Compare its incoming and outgoing speeds in each reference frame.

Gold dot: spacecraft. Blue dot: planet. Planet motion points right. Paths share a linear distance scale; markers are enlarged.

Idealized unpowered flyby: spherical gravity, circular planet orbit and constant planet velocity during the encounter. Atmospheres, rings, moons and solar tides are excluded. Jupiter uses its system mass. The speed comparison uses asymptotic approach and departure, far from the planet; local speed rises near closest approach. This is a learning model, not mission navigation.

Sources: NASA · Gravity assists · JPL · Astrodynamic parameters · JPL · Planet sizes

Does leaving the Sun also mean leaving the Galaxy? Start with an outward solar speed, coast through a model galaxy, then compare the route after a hypothetical stellar encounter.

Gold dot: vessel. Center dot: model center. Gray ring: starting orbital radius. Dashed path: coast without the latest encounter. Distances share a linear scale; markers are enlarged. 1 kpc is about 3,262 light-years; 1 Myr is one million years.