page_title: Space Shuttle Solid Rocket Booster
section_title: Overview
hierarchical_section_title: Space Shuttle Solid Rocket Booster / Overview
caption_attribution_description: English: This photograph was taken during the static test firing of the DM-2 (Demonstration Motor) for the Solid Rocket Booster (SRB) at the testing ground of Thiokol Corporation near Brigham City, Utah. As one of the major components of the Space Shuttle, SRBs provide most of the power, their combined thrust of some 5.8 million pounds, for the first two minutes of flight. The SRBs take the Space Shuttle to an altitude of 28 miles and a speed of 3,094 miles per hour before they separate and fall back into the ocean to be retrieved, refurbished, and prepared for another flight. MSFC has the management responsibilities with Thiokol Corporation as the prime contractor.
context_page_description: The Space Shuttle Solid Rocket Booster was the first solid-propellant rocket to be used for primary propulsion on a vehicle used for human spaceflight and provided the majority of the Space Shuttle's thrust during the first two minutes of flight. After burnout, they were jettisoned and parachuted into the Atlantic Ocean where they were recovered, examined, refurbished, and reused.
  The Space Shuttle SRB was the most powerful solid rocket motor ever flown. Each provided a maximum 14.7 MN 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 t, 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 ATK. The prime contractor for most other components of the SRBs, as well as for the integration of all the components and retrieval of the spent SRBs, was USBI, a subsidiary of Pratt and Whitney. This contract was subsequently transitioned to United Space Alliance, a limited liability company joint venture of Boeing and Lockheed Martin.
context_section_description: 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 2,800,000 pounds-force (12 MN) at sea level, increasing shortly after liftoff to about 3,300,000 lbf (15 MN). 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; 67 km); parachutes were then deployed and impact occurred in the ocean approximately 122 nautical miles (226 km) downrange, after which the two SRBs were recovered. The SRBs helped take the Space Shuttle to an altitude of 28 miles (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 (to orbit) flight, without the possibility of launch or liftoff/ascent abort, until both motors had fully, and simultaneously, fulfilled their functions, consumed their propellants, were producing zero net reaction thrust and had been jettisoned (again simultaneously) by explosive jettisoning bolts from the remainder of the vehicle launch "stack" (shuttle w/engines; fuel/oxidizer tank).  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 and the first of such large 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 (oxidizer) and atomized aluminum powder (fuel), and the total propellant 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 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.
caption: Static test firing, 1978
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