FA-69562 / Orbital propagation / Member archive

Velocity Verlet two-body propagation: Final energy uses the initial radius · case 02

Energy diagnostics hide integration drift because the potential never changes.

Member previewVariant 2 · 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 [[7000.0, 0.0], [0.0, 8.5], 398600.4418, 900.0, 20]	`[4100.742247, 6612.678063, -5.690094, 5.333971, -26.528713]`	`[4100.742247, 6612.678063, -5.690094, 5.333971, -20.813351]`	Failed

MEMBER ARCHIVE

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

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