Retrorocket

A braking rocket serves to reduce the velocity of a spacecraft or for changing the orbit of soft landing. Braking rockets push the exhaust not impede flight direction from what the spacecraft slows down or stops.

Braking rockets to leave orbit

By the use of braking rocket spacecraft in orbit are slowed sufficiently that recirculation and landing can be performed. The necessary change in speed in a low earth orbit is in this case only about 90 m / s, the residual rate is degraded by atmospheric friction.

The Mercury and Gemini spacecraft NASA had separate braking rockets with solid-fuel engines for this purpose. The four retro rockets for the Gemini spacecraft burned per 5.5 s, for a total of 22 s In contrast, using the Space Shuttle, as well as before the Apollo spacecraft not separate braking rockets, but the time allotted for orbit maintenance engines. In Earth orbit missions of the Apollo program, the PLC engine burned for this purpose about 12 s, while the Orbital Maneuvering System of the Space Shuttle burns for about three minutes.

The first use of a braking rocket to leave the orbit was carried out on 14 April 1959 the return capsule of the Discoverer reconnaissance satellites 2 Since the braking rockets were fired at the wrong time, however, the return capsule did not go down in the intended target area.

Braking rockets for suborbital flights

The suborbital test flights of the Mercury program, NASA braking rockets were also used. This was not necessarily ballistic flights necessary, but was an important test for the orbital flights. The first mission took place on 19 December 1960, the mission Mercury - Redstone 1A. The two braking rockets of the Mercury capsule burned per 10 seconds, but time 's offset by 5 and reduced the speed to 168 m / s

Braking rockets at the moon landing

When landing on the moon or on another celestial body without atmosphere neither parachutes nor atmospheric braking can be used to reduce speed. Therefore it must be dismantled, the whole line speed by braking missiles, resulting in much longer burn times and higher fuel consumption. The first successful use of a braking rocket for a soft landing on the moon took place on February 3, 1966 by Luna 9

Use of braking rockets just before touch down

In contrast to U.S. space ships that are based on water or gliding, Russian spaceships land on the mainland. Despite the use of parachutes, the falling speed of the return capsule is still very high. Therefore, further braking rockets are fired shortly before touchdown, which further reduce the speed and mitigate the impact. This system first came to the Voskhod spacecraft Cosmos 47 used and is still used for Soyuz spaceships.