FA-69545 / Orbital propagation / Member archive

Fixed-step RK4 two-body propagation: Loop stops one step short of the end time · case 05

The returned state is for T-h rather than T.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

Input [r0, v0, mu, T, steps] for a planar two-body orbit. Integrate state [x,y,vx,vy] with acceleration -mu r/|r|^3 using classical RK4 with h=T/steps for exactly steps steps. Return the final state rounded to 6 decimals.

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
fixed-step rk4 two-body propagation [[1.0, 0.0], [0.0, 1.2], 1.0, 5.0, 25]	`[-2.01559, 1.162383, -0.416337, -0.355256]`	`[-2.095663, 1.089551, -0.384431, -0.37274]`	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.