Aerocapture

Aerocapture is a technique used to reduce velocity of a spacecraft, arriving at a celestial body with a hyperbolic trajectory, in order to bring it in an orbit with an eccentricity of less than 1. It uses the drag created by the atmosphere of the celestial body to decelerate. Only one pass in the atmosphere is required by this technique, in contrast with aerobraking. However, this approach requires significant thermal protection and precision closed-loop guidance during the maneuver. This level of control authority requires either the production of significant lift, or relatively large attitude control thrusters.

In practice

Aerocapture has not yet been tried on a planetary mission, but the re-entry skip by Zond 6 and Zond 7 upon lunar return were aerocapture maneuvers, since they turned a hyperbolic orbit into an elliptical orbit. On these missions, since there was no attempt to raise the perigee after the aerocapture, the resulting orbit still intersected the atmosphere, and re-entry occurred at the next perigee.

In fiction

Aerocapture within fiction can be read in Arthur C. Clarke's novel "," in which two spacecraft (one Russian, one Chinese) both use aerocapture in Jupiter's atmosphere to shed their excess velocity and position themselves for exploring Jupiter's satellites. This can be seen as a special effect in the movie version (created by MGM/released by Warner Home Video) in which only a Russian spacecraft undergoes aerocapture (in the film incorrectly called aerobraking), which is demonstrated via special effects.

ee also

*Atmospheric reentry
*Skip reentry
*Aerobraking

References

* [http://www.inspacepropulsion.com/tech/aeroassist.html NASA article on aeroassist]