The gravitational maneuver is a way to change the direction of movement of the spacecraft, as well as increase or decrease its speed using the gravity of massive objects and without using valuable fuel on board the spacecraft.
Probably, the possibility of such a gravitational maneuver was guessed still antique astronomers and stars of ancient Babylon when they observed comet movements that change their trajectory and speed when they flew next to other celestial bodies.
The principle of operation of the gravitational maneuver can be described as follows: if the spacecraft is closer to the inner side of the orbit of the planet, then its speed slows down. If the device is a span with the outside of the orbit of the planet, then its speed will increase. This principle of action resembles the work of the prashaner, the throwing projectile. That is why often gravitational maneuver is called "gravitational random".
It should be understood that in the reference system associated with the celestial object, which is used for gravitational maneuver (for example, the probe passes near Venus), no positive effect for the spacecraft will not be observed, except for changing its flight path. However, relative to other celestial bodies (for example, the Sun), the spacecraft will move faster / slower.
The advantages of gravitational maneuver are obvious. It allows you to increase / slow down the speed without having to include engines, which leads to a large fuel economy. Less fuel is more than payload. Accordingly, so much useful load is fed to one spacecraft, as they would have had to carry two devices that did not use the effect of "gravitational powers". Safe as a result, money can be distributed to other space projects.
Probably the most famous apparatus used by the gravitational maneuver, the American Voyager-2 became. Thanks to the system of accelerations and braking, he flew in a tour of the solar system along the land-Jupiter-Saturn-Uranian-Neptune route. And now, having received acceleration from the planets, already out of the borders of the solar system.
No less interesting, Voyager 1 apparatus. Its current speed of 17 km / s, achieved with the help of gravitational maneuvers, is the highest among all man-made human objects, although at the start it was an order of magnitude less.
The combination of gravitational maneuvers was forced to resort the interplanetary station "Cassini". Twice using the gravitational field of Venus and one time of the earth and Jupiter, the device accelerated to the required speed, using at the same time 25 times (!) Less fuel than it would take without the use of gravitational maneuvers.
This is interesting: G Ravitational maneuver is most profitable to apply near objects with greater speed and greater gravity. The perfect candidate for such an object is obvious: stars. The minds of scientists have long been exploring the idea to fly on the spacecraft near the neutron stars. According to estimates, such a maneuver could disperse the ship to 1/3 of the light speed. This is the magnitude! With this speed, intergalactic flights no longer seem so impossible ...