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The Space Shuttle Solid Rocket Boosters (SRBs) were the first solid fuel motors 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 SRBs were the most powerful rocket motors ever flown. Each provided a maximum 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 , 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. Out of 270 SRBs launched over the Shuttle program, all but four were recovered – those from STS-51-L (last ''Challenger'' mission) and STS-4.〔(【引用サイトリンク】url=http://www.nasaspaceflight.com/2012/07/final-flight-superb-performance-sts-135s-srbs/ )〕 Over 5,000 parts were refurbished for reuse after each flight. The final set of SRBs that launched STS-135 included parts that flew on 59 previous missions, including STS-1.〔(【引用サイトリンク】url=http://www.spaceflightnow.com/shuttle/sts135/110418srbs/ )〕 Recovery also allowed post-flight examination of the boosters,〔(【引用サイトリンク】url=http://www.nasaspaceflight.com/2011/06/sts-134-ifa-review-srbs-rsrms-perform-admirably/ )〕 identification of anomalies, and incremental design improvements.〔(【引用サイトリンク】url=http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120001536.pdf )〕 ==Overview== The two reusable SRBs provided the main thrust to lift the shuttle off the launch pad and up to an altitude of about . 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 launch platform. Each booster had a liftoff thrust of approximately at sea level, increasing shortly after liftoff to about . They were ignited after the three Space Shuttle Main Engines' thrust level was verified. Seventy-five seconds after SRB separation, SRB apogee occurred at an altitude of approximately ; parachutes are then deployed and impact occurred in the ocean approximately downrange, after which the two SRBs are recovered. The SRBs were the largest solid-propellant motors ever flown and the first of such large rockets designed for reuse. Each is long and in diameter. Each SRB weighed approximately at launch. The two SRBs constituted about 69% of the total lift-off mass. The propellant for each solid rocket motor weighed approximately . The inert weight of each SRB was approximately . 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. "Solid rocket booster" applied to the entire rocket assembly, which included the recovery parachutes, electronic instrumentation, separation rockets, range safety destruct system, and thrust vector control. The term "solid rocket motor" applied to the propellant, case, igniter and nozzle. 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 lift-off. 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 three O-rings (two prior to the ''Challenger'' Disaster in 1986) and heat-resistant putty. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Space Shuttle Solid Rocket Booster」の詳細全文を読む スポンサード リンク
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