Retrorocket

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Descent of a Martian lander halted by retrorockets (computer-generated impression)
Soyuz space capsule retro-rockets cushion the landing impact

A retrorocket (short for retrograde rocket) is a

reusable launch systems
.

History

Rockets were fitted to the nose of some models of the DFS 230, a World War II German Military glider.[1] This enabled the aircraft to land in more confined areas than would otherwise be possible during an airborne assault.

Another World War II development was the British Hajile project, initiated by the British Admiralty's Directorate of Miscellaneous Weapons Development. Originally a request from the British Army as a method to drop heavy equipment or vehicles from aircraft flying at high speeds and altitudes, the project turned out to be a disaster and was largely forgotten after the war. Although some of the tests turned out to be successful, Hajile was too unpredictable to be used in conventional warfare, and by the time the war drew to a close, with no chance to put the project into action, it was shelved. Later Soviet experiments used this technique, braking large air-dropped cargos after a parachute descent.

Uses

Deorbit maneuvers

When a spacecraft in

reenter
the atmosphere at a much later date; in the case of crewed flights, long after life support systems have been expended. Therefore, it is critical that spacecraft have extremely reliable retrorockets.

Project Mercury

Due to the high reliability demanded by de-orbiting retrorockets,

lbf (4.5 kN) thrust retrorockets that fired for 10 seconds each, strapped to the heat shield on the bottom of the spacecraft. One was sufficient to return the spacecraft to Earth if the other two failed.[2]

Project Gemini

Gemini used four rockets, each 2,500 pounds-force (11 kN), burning for 5.5 seconds in sequence, with a slight overlap. These were mounted in the retrograde section of the adapter module, located just behind the capsule's heat shield.[3][4]

Apollo program

For lunar flights, the

lunar orbit insertion. The Apollo Lunar Module used its descent stage engine
to drop from orbit and land on the Moon.

Space Shuttle program

The

Orbital maneuvering system provided the vehicle with a pair of powerful liquid-fueled rockets for both reentry and orbital maneuvering. One was sufficient for a successful reentry, and if both systems were to fail, the reaction control system
could slow the vehicle enough for reentry.

Launch vehicle staging

To ensure clean separation and prevent contact,

ullage rockets
, both to aid separation and ensure good starting of liquid-fuel engines.

Landers

Retrorockets are also used in landing spacecraft on other astronomical bodies, such as the

Project Apollo
) the main rocket on a spacecraft can be re-oriented to serve as a retrorocket. The Soyuz capsule uses small rockets for the last phase of landing.

Reusable launch systems

New uses for retro-thrust rockets emerged since 2010 for

the European Commission's RETALT project and the China National Space Administration's Long March 8 are also pursuing retro-thrust re-entry for reusable boosters.[5][6]

New Shepard is a reusable single-stage suborbital rocket where the booster uses its main engine to land again after a flight. The capsule slows its descent with parachutes and uses retrorockets to slow down just before reaching the ground.

Operation Credible Sport

hostages in Iran resulted in the construction of two modified Lockheed C-130 Hercules, designated YMC-130H, which featured retro-rockets to allow it to perform extremely short landings. As part of the plan, these aircraft would land in the Shahid Shiroudi Stadium near the US Embassy in Tehran and use the retrorockets to come to a stop. One aircraft was destroyed in a crash during a test flight without any fatalities, and the plan was scrapped later that year.[7]

References

  1. ISBN 1-58663-762-2
    .
  2. ^ "Mercury capsule description & specifications". weebau.com. Retrieved 8 January 2020.
  3. ^ "Gemini". braeunig.us. Retrieved 7 January 2019.
  4. ^ "Gemini 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12". skyrocket.de. Retrieved 7 January 2019.
  5. ^ "RETALT project". retalt.eu. Retrieved 8 January 2020.
  6. Eric, Berger. "Europe says SpaceX "dominating" launch, vows to develop Falcon 9-like rocket"
    . Retrieved 8 January 2020.
  7. ^ Ian, D'Costa. "The US Military Planned on Using This Crazy Modified C-130 to Rescue Hostages in Iran". tacairnet.com. Retrieved 8 January 2020.
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