page_title: Space Shuttle
section_title: Solid Rocket Boosters
hierarchical_section_title: Space Shuttle / Description / Solid Rocket Boosters
caption_attribution_description: English: CAPE CANAVERAL, Fla. -- At NASA's Kennedy Space Center in Florida, a crawler-transporter moves a mobile launcher platform with two solid rocket boosters perched on top from the Vehicle Assembly Building's (VAB) High Bay 1 to High Bay 3. Inside the VAB, the boosters will be joined to an external fuel tank next month in preparation for space shuttle Endeavour's STS-134 mission to the International Space Station targeted to launch in February, 2011. For more information visit: http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html
context_page_description: The Space Shuttle was a partially reusable low Earth orbital spacecraft system that was operated from 1981 to 2011 by the National Aeronautics and Space Administration as part of the Space Shuttle program. Its official program name was Space Transportation System, taken from a 1969 plan for a system of reusable spacecraft of which it was the only item funded for development. The first of four orbital test flights occurred in 1981, leading to operational flights beginning in 1982. Five complete Space Shuttle orbiter vehicles were built and flown on a total of 135 missions from 1981 to 2011, launched from the Kennedy Space Center in Florida. Operational missions launched numerous satellites, Interplanetary probes, and the Hubble Space Telescope; conducted science experiments in orbit; and participated in construction and servicing of the International Space Station. The Space Shuttle fleet's total mission time was 1322 days, 19 hours, 21 minutes and 23 seconds.
context_section_description: The Solid Rocket Boosters (SRB) provided 71.4% of the Space Shuttle's thrust during liftoff and ascent, and were the largest solid-propellant motors ever flown. Each SRB was 45 m (149.2 ft) tall and 3.7 m (12.2 ft) wide, weighed 68,000 kg (150,000 lb), and had a steel exterior approximately 13 mm (.5 in) thick. The SRB's subcomponents were the solid-propellant motor, nose cone, and rocket nozzle. The solid-propellant motor comprised the majority of the SRB's structure. Its casing consisted of 11 steel sections which made up its four main segments. The nose cone housed the forward separation motors and the parachute systems that were used during recovery. The rocket nozzles could gimbal up to 8° to allow for in-flight adjustments.
  The rocket motors were each filled with a total 500,000 kg (1,106,640 lb) of solid rocket propellant, and joined together in the Vehicle Assembly Building (VAB) at KSC. In addition to providing thrust during the first stage of launch, the SRBs provided structural support for the orbiter vehicle and ET, as they were the only system that was connected to the mobile launcher platform (MLP). At the time of launch, the SRBs were armed at T-5 minutes, and could only be electrically ignited once the RS-25 engines had ignited and were without issue. They each provided 12,500 kN (2,800,000 lbf) of thrust, which was later improved to 13,300 kN (3,000,000 lbf) beginning on STS-8. After expending their fuel, the SRBs were jettisoned approximately two minutes after launch at an altitude of approximately 46 km (150,000 ft). Following separation, they deployed drogue and main parachutes, landed in the ocean, and were recovered by the crews aboard the ships MV Freedom Star and MV Liberty Star. Once they were returned to Cape Canaveral, they were cleaned and disassembled. The rocket motor, igniter, and nozzle were then shipped to Thiokol to be refurbished and reused on subsequent flights.
  The SRBs underwent several redesigns throughout the program's lifetime. STS-6 and STS-7 used SRBs that were 2,300 kg (5,000 lb) lighter than the standard-weight cases due to walls that were 0.10 mm (.004 in) thinner, but were determined to be too thin. Subsequent flights until STS-26 used cases that were 0.076 mm (.003 in) thinner than the standard-weight cases, which saved 1,800 kg (4,000 lb). After the Challenger disaster as a result of an O-ring failing at low temperature, the SRBs were redesigned to provide a constant seal regardless of the ambient temperature.
caption: Two SRBs on the mobile launcher platform prior to mating with the ET and orbiter
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