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Booster Statistics
Thrust at lift-off
1,202,020 kilograms
(2,650,000 pounds)
Propellant Properties
Atomized aluminum powder (fuel - 16 %)
Ammonium perchlorate (oxidizer - 69.83 %)
Iron oxide powder
(catalyst - 0.17 %)
Polybutadiene acrylic acid
acrylonite (binder - 12 %)
Epoxy curing agent (2 %)
Empty: 87,543 kilograms
(193,000 pounds)
502,126 kilograms
(1,107,000 pounds)
Gross: 589,670 kilograms
(1,300,000 pounds)

IMAGE: Solid rocket booster separation video
About two and a half minutes after launch the solid rocket boosters exhaust their fuel then separate from the shuttle.

IMAGE: Mission Basics

Space Shuttle Basics

Solid Rocket Boosters

The solid rocket boosters (SRB) operate in parallel with the main engines for the first two minutes of flight to provide the additional thrust needed for the orbiter to escape the gravitational pull of the Earth. At an altitude of approximately 45 km (24 nautical miles), the boosters separate from the orbiter/external tank, descend on parachutes, and land in the Atlantic Ocean. They are recovered by ships, returned to land, and refurbished for reuse. The boosters also assist in guiding the entire vehicle during initial ascent. Thrust of both boosters is equal to 5,300,000 lb.

IMAGE: Diagram of Solid Rocket BoosterIn addition to the solid rocket motor, the booster contains the structural, thrust vector control, separation, recovery, and electrical and instrumentation subsystems.

The solid rocket motor is the largest solid propellant motor ever developed for space flight and the first built to be used on a manned craft. The huge motor is composed of a segmented motor case loaded with solid propellants, an ignition system, a movable nozzle and the necessary instrumentation and integration hardware.

IMAGE: Solid rocket boosters at separation
The SRBs separate from Columbia about two minutes after the first launch of the Shuttle Program.

Each solid rocket motor contains more than 450,000 kg (1,000,000 lb.) of propellant, which requires an extensive mixing and casting operation at a plant in Utah. The propellant is mixed in 600 gallon bowls located in three different mixer buildings. The propellant is then taken to special casting buildings and poured into the casting segments.

Cured propellant looks and feels like a hard rubber typewriter eraser. The combined polymer and its curing agent is a synthetic rubber. Flexibility of the propellant is controlled by the ratio of binder to curing agent and the solid ingredients, namely oxidizer and aluminum. The solid fuel is actually powdered aluminum—a form similar to the foil wraps in your kitchen—mixed with oxygen provided by a chemical called ammonium perchlorate.

Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 10/22/2002
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