Is this flight software?

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

Apsides

Periapsis / apoapsis radii and speeds from semi-major axis and eccentricity.

SIDUS educational calculator. Category orbital. Tags: apollo, orbital, vis-viva. Pure SI. Not flight software.

r_p = a(1−e) r_a = a(1+e) v_p, v_a via vis-viva

Periapsis & apoapsis geometry

Fundamentals of Astrodynamics and Applications (David A. Vallado): Standard reference for two-body, Lambert, maneuvers, and J2. Equations implemented independently in SIDUS.
Orbital Mechanics for Engineering Students (Howard D. Curtis): Textbook derivations for Hohmann, vis-viva, rocket equation, elements.
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.

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