Space shuttle solid rocket rockets

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Overview image of an SRB
Static burning test

The space shuttle solid rocket ( English Solid Rocket Booster , abbreviation SRB ) were responsible as boosters for the main part of the thrust to carry the space shuttle into space. To this day, they are the most powerful rocket engines that have ever been used.

In the future, these engines will be used for the planned SLS (Space Launch System) .

Use on the space shuttle

The two reusable SRBs produced the majority of the space shuttle's takeoff thrust, beginning with the take-off from the launch platform to a height of approximately 45 km where they were dropped.

Each SRB for the space shuttle consisted of four propellant segments and was 45.46 m long and 3.71 m wide. The take-off weight was 590 t per booster, with 84.7 t being attributable to the structure.

Each booster had a thrust of 12.45 MN at sea level, which increased to around 14.5 MN shortly after take-off  . The ignition occurred 6.6 seconds after ignition of the three main engines of the orbiter , provided that at least 90% had reached its full thrust, which should normally have been the case within 3 seconds. The SRB provided 83% of the required thrust when the space shuttle launched. 125 seconds after the start, two flaps on the upper tip of the solids booster were blown open, whereupon the internal pressure of the propellant was suddenly reduced. This ensured that both boosters lose their thrust at the same time. If one booster had delivered more thrust than the other, the asymmetrical thrust distribution would have caused the orbiter to tip over. Only then were the connecting bolts to the external tank separated and the booster pushed away from the tank with the help of eight small auxiliary rockets. 75 seconds after the separation, the SRB reached their apex height at around 65 km and then sank back to earth on three parachutes. Approximately 230 km from the starting point, the boosters fell into the Atlantic Ocean , from which they were recovered, examined and reused. For this purpose, NASA operated the two salvage ships " Freedom Star " and " Liberty Star ".

A failure of a booster sealing ring as a result of unusually low outside temperatures the night before the start was the cause of the Challenger crash , in which all seven astronauts died shortly after the start in 1986.

Use after the space shuttle


When the end of the space shuttle became foreseeable after the Columbia disaster in 2003, the then President of the United States , George W. Bush , decided to launch the Constellation program, which would secure manned access to Earth orbit and manned flights to the after the end of the shuttle Moon and beyond should allow. A further developed SRB was intended as the first stage for the manned launch vehicle Ares I and two as a booster for the Ares V , which should also use a main stage based on the external tank of the space shuttle. In contrast to the version with four fuel segments for the space shuttle, the boosters for the Ares rocket family, in addition to more modern electronics and avionics, should consist of 5 fuel segments. The burn time hardly changes due to the additional fuel, but there is a significant increase in thrust, the extended boosters now reach over 16 MN and are by far the most powerful rocket engines in the world. The SRB are now around 55 m long and have a takeoff weight of around 700 t. Before the end of the Constellation program, only one suborbital test flight with the Ares IX mission took place, but on this flight only four of the five segments were filled with fuel. On the ground, however, there were already three test ignitions of the five-segment booster as part of the Constellation program.

Space Launch System

After the Constellation program was discontinued in 2010 by the subsequent President Barack Obama for cost reasons, the United States Congress decided to continue using some of the concepts, for example, the SRB should be developed in a further developed form as a temporary booster for the one based on the shuttle's carrier system Similar to the Ares V, the new manned SLS launcher will act. Its first flight with the Artemis 1 mission is scheduled to take place in 2021 at the earliest, with the new NASA spacecraft Orion-MPCV being carried into orbit around the moon and back to earth in its second unmanned test flight. Recovery and reuse is not provided for with the SLS. The boosters for the SLS were taken directly from the Ares program. After the three successful test ignitions for Ares so far, further tests were carried out in March 2015 and June 2016. In the medium term, however, these boosters are to be replaced by more modern ones, a tender from NASA is currently (as of 2015) in progress. Proposals are more modern solid fuel boosters with a lighter housing made of composite materials or kerosene-powered liquid boosters with modernized F-1 engines or NK-33 engines . The new boosters should bring a significant increase in the SLS's payload to up to 130t in low earth orbit.


The fuel consists of a mix of ammonium perchlorate ( oxidizer , 69.6% by weight), aluminum (fuel, 16%), iron oxide ( catalyst , 0.4%), a polymer ( butadiene rubber or butadiene as a binder and additional fuel, 12.04%) and an epoxy resin hardener (1.96%). This mixture is called Ammonium Perchlorate Composite Propellant (APCP) and delivers a specific impulse of 242 s at sea level or 268 s in a vacuum.

Web links

Commons : Space Shuttle Solid Rocket  - Collection of images, videos and audio files

Individual evidence

  1. a b Space Launch System Solid Rocket Booster. NASAfacts, February 6, 2015, accessed March 10, 2015 (pdf).
  2. a b Martin Knipfer: SLS: Booster QM-1 ready for testing., March 9, 2015, accessed March 10, 2015 .
  3. QM-2 test of the SLS booster. Retrieved August 23, 2016 .