Kinetic Impactor: Real Orbit Propagation (2D)

This 2D companion to the 3D kinetic-impactor simulator drives the same DART-style momentum-enhancement formula Δv = β·(m·v)/M, but instead of multiplying that Δv by a lead time to approximate a straight-line drift, it solves the real two-body Kepler problem: the impactor's Δv is applied as a tangential kick to the asteroid's velocity at perihelion, its new semi-major axis and eccentricity are derived from vis-viva and angular-momentum conservation, and both the original and deflected orbits are propagated forward by solving Kepler's equation exactly for the chosen warning time. The resulting "orbit shift" is the literal distance between two independently propagated Kepler orbits — the same class of calculation real planetary-defense teams run, and a useful check on when a linear Δv×T shortcut over- or under-estimates the real drift.