Aerobraking Campaign — Walking Down an Orbit with Atmospheric Drag

Aerobraking is how missions like Mars Reconnaissance Orbiter and Mars Global Surveyor trade a highly elliptical capture orbit for a low, near-circular science orbit without a huge propellant budget. This simulator propagates a real Keplerian orbit around a Mars-sized planet, and on every periapsis pass applies a drag impulse computed from the exponential atmosphere the craft dips into — shrinking the apoapsis pass after pass while the periapsis, where the drag actually happens, stays fixed. Tune the periapsis depth, the spacecraft's drag-panel strength and the atmosphere's scale height, and watch the campaign either crawl safely toward a circular orbit or overheat itself in a handful of passes if you dive too deep.