Propagate a Keplerian orbit and watch the conserved invariants certify the math.
See it run - a worked example, 100% in this browser tab
The problem
Orbit visualizers rarely tell you whether their propagation is actually faithful, and conflate the dated gravitational constant with eternal truth.
The local-first solution
This plugin solves Kepler's equation by Newton-Raphson in the browser, reconstructs position and velocity over one period, and recomputes the conserved specific energy and angular momentum at every sample to report the true drift from their analytic values.
What it does
Newton-Raphson solve of Kepler's equation M = E - e sin E
Perifocal position and velocity reconstruction over one full period
Vis-viva specific energy and specific angular momentum tracked as invariants
Max invariant drift mapped to the GeoNum trust ladder
Cited IAU/JPL gravitational parameters per primary, surfaced as confirmable inputs
Honest scope
Exact closed-form two-body relations in f64; mu = G*M is a dated/measured constant you confirm per primary, and the value used is always surfaced. Perturbations (J2, third-body, drag, relativity) and hyperbolic/parabolic orbits are NOT modeled. A green verdict certifies the invariants, not the long-horizon ephemeris. Not flight-certified mission software.
Authorities cited
Vallado, D. A. (2013). Fundamentals of Astrodynamics and Applications, 4th ed. Microcosm/Springer. Sec. 2.2-2.4 - Kepler's equation, the eccentric/true anomaly relations, and the perifocal position/velocity reconstruction.
Bate, Mueller, White (1971). Fundamentals of Astrodynamics. Dover. Ch. 1-4 - the two-body problem, vis-viva v^2 = mu*(2/r - 1/a), and conservation of specific energy and angular momentum.
Danby, J. M. A. (1988). Fundamentals of Celestial Mechanics, 2nd ed. Willmann-Bell. Sec. 6.6 - Newton-Raphson solution of Kepler's equation and convergent starting guesses.
Kepler, J. (1609/1619). Astronomia Nova (equation of the orbit) and Harmonices Mundi (the third law, T^2 proportional to a^3). The mean anomaly advances linearly in time.
Curtis, H. D. (2014). Orbital Mechanics for Engineering Students, 3rd ed. Butterworth-Heinemann. Ch. 2-3 - the orbit equation r = a(1 - e*cos E) and the angular-momentum/energy integrals.
IAU 2015 Resolution B3 / JPL DE ephemerides - standard gravitational parameters: GM_Earth = 3.986004418e14, GM_Sun = 1.32712440018e20 m^3/s^2 (confirm per primary and epoch).
Visualize an orbit
Propagate an orbit in the browser and save the invariant-checked result to Sandbox, attach it to a Worklog case, or route it into a Gate client portal. Nothing is uploaded to anyone's cloud.