Aerocapture

Atmosphäreneinfang (English Aero capture) refers to a technique by which the velocity of a space vehicle that arrives on a hyperbolic trajectory of a celestial body with relatively dense atmosphere can be reduced, so that it enters into orbit. As a result, the spacecraft orbits the heavenly body after this maneuver on an elliptical orbit, with the result that it can not leave this without further drive.

Process

To decelerate the spacecraft, it approaches the celestial bodies so much that it flies through grazing the upper atmosphere, where it is greatly slowed. By this occurring much friction heat it needs a heat shield. The degree of deceleration depends strongly on the altitude from, this is very critical and requires full understanding of the atmosphere as well as the flight path ahead. An excessively low heating approach and deceleration become too large, while when too high, the risk of approach to the spacecraft from the atmosphere rebounding and uncontrolled unit to a useless path.

After Atmosphäreneinfang the flight speed of the spacecraft has decreased below the escape velocity of the celestial body. He therefore enters into an elliptical orbit around him, with an eccentricity of less than 1, the planet closest point ( periapsis ) is in this case still deep within the atmosphere. Therefore, the spacecraft must still during the first revolution in the apoapsis ( planets most distant point) with his engine, the train lift (ie accelerate again ) to raise the periapsis above the atmosphere, as it occur otherwise after one complete revolution, back into the atmosphere and crash would.

A less high -boost with the target while the other rounds decelerate by atmospheric braking ( aerobraking ) continue to reduce the eccentricity of the elliptical orbit is also possible.

Does the celestial bodies no appreciable atmosphere, so no Atmosphäreneinfang can be performed on this celestial body.

Missions

So far this technique has only been used in two space probes. Zond 6 and Zond 7 are re-entered after a Atmosphäreneinfang over the Indian Ocean after a nearly complete orbit Earth in the atmosphere, in order to then put in for a landing.

The first probe, which was to reach another planet with a Atmosphäreneinfang was Mars Odyssey, like many other plans of NASA, this was however not implemented and the probe used a rocket engine to brake.