Lambert's Problem: Orbital Rendezvous Transfer Solver (2D)

Real station-keeping and rendezvous planning rarely gets the luxury of a perfectly aligned Hohmann transfer — a chaser vehicle has to reach a target at a specific position after a specific flight time, from wherever it happens to be. That two-point, fixed-time boundary value problem is Lambert's problem, and this simulator solves it live with the universal-variable method (Stumpff functions plus Newton–Raphson root-finding on the universal anomaly z), the same technique used to plan real rendezvous burns and interplanetary transfer windows. Set a departure radius, a target radius, the angle swept between them and the time of flight, and watch the solver compute the one two-body trajectory that satisfies all four constraints — then verifies itself by numerically integrating Newton's law of gravitation along that trajectory and reporting how close the independent propagation lands to the true target. This top-down 2D rendering makes the shared orbital plane explicit: pan and zoom to inspect the geometry directly.