Aerocapture
Encyclopedia
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
of a spacecraft, arriving at a celestial body
Celestial Body
Celestial Body is a Croatian film directed by Lukas Nola. It was released in 2000....
with a hyperbolic trajectory
Hyperbolic trajectory
In astrodynamics or celestial mechanics a hyperbolic trajectory is a Kepler orbit with the eccentricity greater than 1. Under standard assumptions a body traveling along this trajectory will coast to infinity, arriving there with hyperbolic excess velocity relative to the central body. Similarly to...
, in order to bring it in an orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
with an eccentricity of less than 1. It uses the drag created by the atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
of the celestial body
Celestial Body
Celestial Body is a Croatian film directed by Lukas Nola. It was released in 2000....
to decelerate. Only one pass in the atmosphere is required by this technique, in contrast with aerobraking
Aerobraking
Aerobraking is a spaceflight maneuver that reduces the high point of an elliptical orbit by flying the vehicle through the atmosphere at the low point of the orbit . The resulting drag slows the spacecraft...
. 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 skipSkip reentry
Skip reentry is a reentry technique involving one or more successive "skips" off the atmosphere to achieve greater entry range or to slow the spacecraft before final entry, which helps to dissipate the huge amount of heat that is usually generated on faster descents...
by Zond 6
Zond 6
Zond 6, a formal member of the Soviet Zond program and unmanned version of Soyuz 7K-L1 manned moon-flyby spacecraft, was launched on a lunar flyby mission from a parent satellite in Earth parking orbit...
and Zond 7
Zond 7
This article was originally based on material from ...
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.
Aerocapture was originally planned for the Mars Odyssey orbiter, but later changed to aerobraking for reasons of cost and commonality with other missions.
Aerocapture has been proposed and analyzed for arrival at Saturn's moon Titan
Titan (moon)
Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....
.
In fiction
Aerocapture within fiction can be read in Arthur C. ClarkeArthur C. Clarke
Sir Arthur Charles Clarke, CBE, FRAS was a British science fiction author, inventor, and futurist, famous for his short stories and novels, among them 2001: A Space Odyssey, and as a host and commentator in the British television series Mysterious World. For many years, Robert A. Heinlein,...
's novel 2010: Odyssey Two
2010: Odyssey Two
2010: Odyssey Two is a 1982 best-selling science fiction novel by Arthur C. Clarke. It is the sequel to the 1968 novel 2001: A Space Odyssey, but continues the story of Stanley Kubrick's film adaptation with the same title and not Clarke's original novel. The book is a part of Clarke's...
, 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
Aerobraking
Aerobraking is a spaceflight maneuver that reduces the high point of an elliptical orbit by flying the vehicle through the atmosphere at the low point of the orbit . The resulting drag slows the spacecraft...
), which is demonstrated via special effects.
See also
- Atmospheric reentryAtmospheric reentryAtmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...
- Skip reentrySkip reentrySkip reentry is a reentry technique involving one or more successive "skips" off the atmosphere to achieve greater entry range or to slow the spacecraft before final entry, which helps to dissipate the huge amount of heat that is usually generated on faster descents...
- AerobrakingAerobrakingAerobraking is a spaceflight maneuver that reduces the high point of an elliptical orbit by flying the vehicle through the atmosphere at the low point of the orbit . The resulting drag slows the spacecraft...
- Aerogravity assistAerogravity assistAn aerogravity assist, or AGA, is a spacecraft maneuver designed to change velocity when arriving at a body with an atmosphere. A pure gravity assist uses only the gravity of a body to change the direction of the spacecraft trajectory. The change in direction is limited by the mass of the body,...
- Asteroid captureAsteroid captureAsteroid capture can happen when an asteroid approaches a large planetary body.Typically asteroids that approach close enough to a planet are thrown out into space or impact the body. In rarer instances, the asteroid is captured in orbit around the planet...