page_title: Aerocapture
hierarchical_section_title: Aerocapture
caption_attribution_description: English: Schematic showing the various phases of aerocapture maneuver.
context_page_description: Aerocapture is an orbital transfer maneuver in which a spacecraft uses
  aerodynamic drag force from a single pass through a planetary
  atmosphere to decelerate and achieve orbit insertion.
  Aerocapture uses a planet's or moon's atmosphere to accomplish a quick, near-propellantless orbit insertion maneuver to place a spacecraft in its science orbit. The aerocapture maneuver starts as the spacecraft enters the atmosphere of the target body from an interplanetary approach trajectory. The aerodynamic drag generated as the vehicle descends into the atmosphere slows the spacecraft. After the spacecraft slows enough to be captured by the planet, it exits the atmosphere and executes a small propulsive burn at the first apoapsis to raise the periapsis outside the atmosphere. Additional small burns may be required to correct apoapsis and inclination targeting errors before the initial science orbit is established.
  Compared to conventional propulsive orbit insertion, this nearly fuel-free method of deceleration could significantly reduce the mass of an interplanetary spacecraft as a substantial fraction of the spacecraft mass is often propellant used for the orbit insertion burn.
context_section_description: Aerocapture is an orbital transfer maneuver in which a spacecraft uses
  aerodynamic drag force from a single pass through a planetary
  atmosphere to decelerate and achieve orbit insertion.
  Aerocapture uses a planet's or moon's atmosphere to accomplish a quick, near-propellantless orbit insertion maneuver to place a spacecraft in its science orbit. The aerocapture maneuver starts as the spacecraft enters the atmosphere of the target body from an interplanetary approach trajectory. The aerodynamic drag generated as the vehicle descends into the atmosphere slows the spacecraft. After the spacecraft slows enough to be captured by the planet, it exits the atmosphere and executes a small propulsive burn at the first apoapsis to raise the periapsis outside the atmosphere. Additional small burns may be required to correct apoapsis and inclination targeting errors before the initial science orbit is established.
  Compared to conventional propulsive orbit insertion, this nearly fuel-free method of deceleration could significantly reduce the mass of an interplanetary spacecraft as a substantial fraction of the spacecraft mass is often propellant used for the orbit insertion burn. The saving in propellant mass allows for more science instrumentation to be added to the mission, or allows for a smaller and less-expensive spacecraft, and potentially a smaller, less-expensive launch vehicle. 
  Because of the aerodynamic heating encountered during the atmospheric pass, the spacecraft must be packaged inside an aeroshell (or a deployable entry system) with a thermal protection system. The vehicle also requires autonomous closed-loop guidance during the maneuver to enable the vehicle to target the desired capture orbit and command the vehicle to exit the atmosphere when sufficient energy has been dissipated. Ensuring the vehicle has enough control authority to prevent the spacecraft penetrating too deep into the atmosphere or exiting prematurely without dissipating enough energy requires either the use of a lifting aeroshell, or a drag modulation system which can change vehicle drag area during flight. 
  Aerocapture has been shown to be feasible at Venus, Earth, Mars, and Titan using existing entry vehicles and thermal protection system materials. Studies are currently underway to assess aerocapture feasibility at Uranus and Neptune in support of missions in the next decade. Aerocapture at Jupiter and Saturn is considered a long-term goal as their huge gravity wells result in very high entry speeds and harsh aerothermal environments that make aerocapture a less attractive and perhaps infeasible option at these destinations. However, it is possible to use aerocapture at Titan to insert a spacecraft around Saturn.
caption: Schematic showing the various phases of the aerocapture maneuver. Atmospheric height is greatly exaggerated for clarity.
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