FA-69548 / Orbital propagation / Member archive

Velocity Verlet two-body propagation: Position drift omits the one-half acceleration factor · case 03

Positions overshoot toward the central body every step.

Member previewVariant 3 · 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 [[0.0, 9000.0], [-6.2, 0.8], 398600.4418, 1200.0, 15]	`[-6489.974993, 6502.627983, -4.081661, -4.298127, -25.81975]`	`[-6596.602558, 6758.244077, -4.170275, -4.186438, -24.748038]`	Failed

MEMBER ARCHIVE

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