Is this flight software?

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

Density Isp

rho*Isp figure of merit.

SIDUS educational calculator. Category propulsion. Tags: propulsion. Pure SI. Not flight software.

ρIsp = ρ · Isp · figure of merit

Density specific impulse

NASA Glenn Research Center: Beginner’s Guide to Aeronautics (NASA GRC): Ideal rocket equation, specific impulse, thrust equation, dynamic pressure education pages.
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.