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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Space Shuttle Solid Rocket Booster | 1/9 | https://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Booster | reference | science, encyclopedia | 2026-05-05T13:22:36.055022+00:00 | kb-cron |
The Space Shuttle Solid Rocket Booster (SRB) was the first solid-propellant rocket to be used for primary propulsion on a vehicle used for human spaceflight. A pair of them provided 85% of the Space Shuttle's thrust at liftoff and for the first two minutes of ascent. After burnout, they were jettisoned, and parachuted into the Atlantic Ocean, where they were recovered, examined, refurbished, and reused. The Space Shuttle SRBs were the most powerful solid rocket motors ever flown at the time of their debut. The Space Launch System (SLS) SRBs, adapted from the shuttle, surpassed it as the most powerful solid rocket motors ever flown, after the launch of the Artemis 1 mission in 2022. The Space Shuttle SRBs were the most powerful solid rocket motors ever to fly humans until similarly surpassed by the SLS SRBs with the launch of the Artemis II mission in 2026. Each Space Shuttle SRB provided a maximum 14.7 MN (3,300,000 lbf) thrust, roughly double the most powerful single-combustion chamber liquid-propellant rocket engine ever flown, the Rocketdyne F-1. With a combined mass of about 1,180 metric tons (2,600,000 lb), they comprised over half the mass of the Shuttle stack at liftoff. The motor segments of the SRBs were manufactured by Thiokol of Brigham City, Utah, which was later purchased by Alliant Techsystems (ATK). The prime contractor for the integration of all the components and retrieval of the spent SRBs, was United Space Boosters Inc., a subsidiary of Pratt & Whitney. The contract was subsequently transitioned to United Space Alliance, a joint venture of Boeing and Lockheed Martin. Out of 270 SRBs launched over the Shuttle program, all but four were recovered – those from STS-4 (due to a parachute malfunction) and STS-51-L (destroyed by the range safety officer during the Challenger disaster). Over 5,000 parts were refurbished for reuse after each flight. The final set of SRBs that launched STS-135 included parts that had flown on 59 previous missions, including STS-1. Recovery also allowed post-flight examination of the boosters, identification of anomalies, and incremental design improvements. Refurbished segments have been used on the solid rocket boosters of the Space Launch System.
== Overview ==
The two reusable SRBs provided the main thrust to lift the shuttle off the launch pad and up to an altitude of about 150,000 ft (28 mi; 46 km). While on the pad, the two SRBs carried the entire weight of the external tank and orbiter and transmitted the weight load through their structure to the mobile launcher platform. Each booster had a liftoff thrust of approximately 12 meganewtons (2,800,000 pounds-force) at sea level, increasing shortly after liftoff to 14.7 MN (3,300,000 lbf). They were ignited after the three RS-25 main engines' thrust level was verified. Seventy-five seconds after SRB separation, SRB apogee occurred at an altitude of approximately 220,000 ft (42 mi; 36 nmi; 67 km); parachutes were then deployed and impact occurred in the ocean approximately 122 nautical miles (226 km; 140 mi) downrange, after which the two SRBs were recovered. The SRBs helped take the Space Shuttle to an altitude of 28 miles (24 nmi; 45 km) and a speed of 3,094 mph (4,979 km/h) along with the main engines. The SRBs committed the shuttle to liftoff and ascent, without the possibility of launch abort, until both motors had fully consumed their propellants and had simultaneously been jettisoned by explosive bolts and thrusters to push them away from the Shuttle. Only then could any conceivable set of launch or post-liftoff abort procedures be contemplated. In addition, failure of an individual SRB's thrust output or ability to adhere to the designed performance profile was probably not survivable. The SRBs were the largest solid-propellant motors ever flown until 2022 and the first solid-propellant rockets designed for reuse. Each is 149.16 ft (45.46 m) long and 12.17 ft (3.71 m) in diameter. Each SRB weighed approximately 1,300,000 lb (590 t) at launch. The two SRBs constituted about 69% of the total lift-off mass. The primary propellants were ammonium perchlorate as the oxidizer along with aluminum powder and PBAN as fuel. The total propellant load for each solid rocket motor weighed approximately 1,100,000 lb (500 t) (see § Propellant). The inert weight of each SRB was approximately 200,000 pounds (91 t). Primary elements of each booster were the motor (including case, propellant, igniter, and nozzle), structure, separation systems, operational flight instrumentation, recovery avionics, pyrotechnics, deceleration system, thrust vector control system, and range safety destruct system. While the terms solid rocket motor and solid rocket booster are often used interchangeably, in technical use they have specific meanings. The term solid rocket motor applied to the propellant, case, igniter and nozzle. Solid rocket booster applied to the entire rocket assembly, which included the rocket motor as well as the recovery parachutes, electronic instrumentation, separation rockets, range safety destruct system, and thrust vector control. Each booster was attached to the external tank at the SRB's aft frame by two lateral sway braces and a diagonal attachment. The forward end of each SRB was attached to the external tank at the forward end of the SRB's forward skirt. On the launch pad, each booster also was attached to the mobile launcher platform at the aft skirt by four holddown studs, with frangible nuts that were severed at liftoff. The boosters were composed of seven individually manufactured steel segments. These were assembled in pairs by the manufacturer and then shipped to Kennedy Space Center by rail for final assembly. The segments were fixed together using circumferential tang, clevis, and clevis pin fastening, and sealed with O-rings (originally two, changed to three after the Challenger Disaster in 1986) and heat-resistant putty.
== Components ==