Is this flight software?

No. SIDUS models are educational reimplementations. Cross-check before any flight decision.

Kepler propagate

Universal-variable two-body state propagation (AGC KEPLER problem class).

SIDUS educational calculator. Category orbital. Tags: apollo, GNC, orbital, trajectory. Pure SI. Not flight software.

r(t), v(t) ← χ · √μ (t−t₀) = f(χ, α, r₀, v₀)

Two-body state propagation (AGC class)

Fundamentals of Astrodynamics and Applications (David A. Vallado): Standard reference for two-body, Lambert, maneuvers, and J2. Equations implemented independently in SIDUS.
Apollo-11 AGC source (NASA / MIT (public domain listings)): Comanche055 & Luminary099 guidance computer source. Algorithms reimplemented from published equations, not copied as binary/listing dumps.
Virtual AGC (ibiblio / Ron Burkey): AGC emulator, scanned listings, and historical documentation.
Orbital Mechanics for Engineering Students (Howard D. Curtis): Textbook derivations for Hohmann, vis-viva, rocket equation, elements.

Read /llms.txt or call https://sidus.tools/api/mcp. Open the interactive page for live SI inputs.