aerobreaking

Aerobraking is a spaceflight maneuver that uses the friction of a planet's atmosphere to slow down a spacecraft. Instead of expending large amounts of fuel for deceleration, a spacecraft performing aerobraking enters a carefully calculated orbit that dips into the upper layers of a planet's atmosphere. The drag created by the atmospheric gases gradually reduces the spacecraft's orbital speed.

This technique is particularly useful for missions traveling to planets with substantial atmospheres, such as Mars or Venus. It allows spacecraft to achieve a lower orbit with significantly less propellant compared to traditional braking maneuvers. The process requires precise navigation and atmospheric modeling to avoid overheating the spacecraft or descending too deeply. Over multiple orbital passes, the atmosphere's drag is used iteratively to lower the orbit to the desired altitude and inclination.

Aerobraking was first demonstrated by the U.S. Air Force's Project REBA in the 1960s. More recently, NASA missions like Mars Global Surveyor, Mars Odyssey, and the Mars Reconnaissance Orbiter have successfully utilized aerobraking to enter Mars orbit, saving substantial amounts of fuel that could then be used for scientific instruments or extended mission duration. It is a crucial technique for many interplanetary missions, contributing to mission efficiency and cost-effectiveness.