FA-69550 / Orbital propagation / Member archive

Velocity Verlet two-body propagation: Position drift omits the one-half acceleration factor · case 05

Positions overshoot toward the central body every step.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

Input [r0, v0, mu, T, steps]; planar two-body. Velocity Verlet with h=T/steps: p += h v + h^2 a/2; a_new = a(p); v += h (a + a_new)/2; carry a_new. Return final [x,y,vx,vy] rounded to 6 plus specific energy v^2/2-mu/|r| rounded to 6.

Why this case matters

Orbit determination and mission planning chain many small conversions; one wrong branch or unit silently moves a spacecraft by kilometres.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
velocity verlet two-body propagation [[1.0, 0.0], [0.0, 1.2], 1.0, 5.0, 25]	`[-1.263526, -0.22052, 0.347844, -0.667586, -0.496317]`	`[-2.100327, 1.143517, -0.394254, -0.35669, -0.276826]`	Failed

MEMBER ARCHIVE

The complete case is available to members.

This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

Member access is invitation-based. Sign in with your invited account to inspect the sources.