Space Shuttle Solid Rocket Booster
Overview
 
The Space Shuttle Solid Rocket Boosters (SRBs) were the pair of large solid rockets
Solid rocket booster
Solid rocket boosters or Solid Rocket Motors, SRM, are used to provide thrust in spacecraft launches from the launchpad up to burnout of the SRBs. Many launch vehicles include SRBs, including the Ariane 5, Atlas V , and the NASA Space Shuttle...

 used by the United States' NASA Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

 during the first two minutes of powered flight. Together they provided about 83% of liftoff thrust for the Space Shuttle. They were located on either side of the rusty or orange-colored external propellant tank
Space Shuttle external tank
A Space Shuttle External Tank is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three Space Shuttle Main Engines in the orbiter...

. Each SRB produced 80% more liftoff thrust than one F-1
F-1 (rocket engine)
The F-1 is a rocket engine developed by Rocketdyne and used in the Saturn V. Five F-1 engines were used in the S-IC first stage of each Saturn V, which served as the main launch vehicle in the Apollo program. The F-1 is still the most powerful single-chamber liquid-fueled rocket engine ever...

 engine, the most powerful single-chamber liquid-fueled rocket engine ever flown — five of which powered the first stage of the Saturn V
Saturn V
The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...

 "moon rocket".
Encyclopedia
The Space Shuttle Solid Rocket Boosters (SRBs) were the pair of large solid rockets
Solid rocket booster
Solid rocket boosters or Solid Rocket Motors, SRM, are used to provide thrust in spacecraft launches from the launchpad up to burnout of the SRBs. Many launch vehicles include SRBs, including the Ariane 5, Atlas V , and the NASA Space Shuttle...

 used by the United States' NASA Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

 during the first two minutes of powered flight. Together they provided about 83% of liftoff thrust for the Space Shuttle. They were located on either side of the rusty or orange-colored external propellant tank
Space Shuttle external tank
A Space Shuttle External Tank is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three Space Shuttle Main Engines in the orbiter...

. Each SRB produced 80% more liftoff thrust than one F-1
F-1 (rocket engine)
The F-1 is a rocket engine developed by Rocketdyne and used in the Saturn V. Five F-1 engines were used in the S-IC first stage of each Saturn V, which served as the main launch vehicle in the Apollo program. The F-1 is still the most powerful single-chamber liquid-fueled rocket engine ever...

 engine, the most powerful single-chamber liquid-fueled rocket engine ever flown — five of which powered the first stage of the Saturn V
Saturn V
The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...

 "moon rocket". The SRBs were the largest solid-fuel rocket motors ever flown, and the first to be used for primary propulsion on human spaceflight
Human spaceflight
Human spaceflight is spaceflight with humans on the spacecraft. When a spacecraft is manned, it can be piloted directly, as opposed to machine or robotic space probes and remotely-controlled satellites....

 missions. The spent SRBs were recovered from the ocean, refurbished, reloaded with propellant, and reused for several missions. The prime contractor for the SRBs and the manufacturer of the vital solid fuel rocket segments was the Thiokol Corporation of Brigham City, Utah
Brigham City, Utah
Brigham City is a city in Box Elder County, Utah, United States. The population was 17,899 at the 2010 census. It is the county seat of Box Elder County. It lies on the western slope of the Wellsville Mountains, a branch of the Wasatch Range at the western terminus of Box Elder Canyon...

.

SRB casings were recovered and reused many times. In one recent example, an SRB stiffener (lower) segment from STS-1
STS-1
STS-1 was the first orbital flight of NASA's Space Shuttle program. Space Shuttle Columbia launched on 12 April 1981, and returned to Earth on 14 April, having orbited the Earth 37 times during the 54.5-hour mission. It was the first American manned space flight since the Apollo-Soyuz Test Project...

 — which over a 30 year period flew six times plus one ground test — was used in 2009 as part of the Ares I
Ares I
Ares I was the crew launch vehicle that was being developed by NASA as part of the Constellation Program. The name "Ares" refers to the Greek deity Ares, who is identified with the Roman god Mars...

 DM-1 test SRB. Collectively, the Ares 1 DM-1 included SRB segments from 48 different Shuttle flights and five ground tests.

Overview

The two reusable SRBs provided the main thrust to lift the shuttle off the launch pad
Launch pad
A launch pad is the area and facilities where rockets or spacecraft lift off. A spaceport can contain one or many launch pads. A typical launch pad consists of the service and umbilical structures. The service structure provides an access platform to inspect the launch vehicle prior to launch....

 and up to an altitude of about 150000 ft (28.4 mi; 45.7 km). While on the pad, the two SRBs carried the entire weight of the external tank and orbiter
Space Shuttle Orbiter
The Space Shuttle orbiter was the orbital spacecraft of the Space Shuttle program operated by NASA, the space agency of the United States. The orbiter was a reusable winged "space-plane", a mixture of rockets, spacecraft, and aircraft...

 and transmitted the weight load through their structure to the mobile launch platform. Each booster had a liftoff thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....

 of approximately 2800000 pound-forces (12.5 MN) at sea level, increasing shortly after liftoff to about 3100000 lbf (13.8 MN). They were ignited after the three Space Shuttle Main Engine
Space Shuttle main engine
The RS-25, otherwise known as the Space Shuttle Main Engine , is a reusable liquid-fuel rocket engine built by Pratt & Whitney Rocketdyne for the Space Shuttle, running on liquid hydrogen and oxygen. Each Space Shuttle was propelled by three SSMEs mated to one powerhead...

s' thrust level is verified. Seventy-five seconds after SRB separation, SRB apogee occurred at an altitude of approximately 220000 ft (41.7 mi; 67.1 km); parachute
Parachute
A parachute is a device used to slow the motion of an object through an atmosphere by creating drag, or in the case of ram-air parachutes, aerodynamic lift. Parachutes are usually made out of light, strong cloth, originally silk, now most commonly nylon...

s are then deployed and impact occurred in the ocean approximately 122 nautical miles (225.9 km) downrange, after which the two SRBs are recovered.

The SRBs are the largest solid-propellant motors
Solid rocket
A solid rocket or a solid-fuel rocket is a rocket engine that uses solid propellants . The earliest rockets were solid-fuel rockets powered by gunpowder; they were used by the Chinese in warfare as early as the 13th century and later by the Mongols, Arabs, and Indians.All rockets used some form of...

 ever flown and the first of such large rockets designed for reuse. Each is 149.16 ft (45.5 m) long and 12.17 ft (3.7 m) in diameter.

Each SRB weighs approximately 1300000 lb (589,670.1 kg) at launch. The two SRBs constitute about 60% of the total lift-off mass. The propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...

 for each solid rocket motor
Spacecraft propulsion
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the...

 weighs approximately 1100000 lb (498,951.6 kg). The inert weight of each SRB is approximately 200000 lb (90,718.5 kg).

Primary elements of each booster are the motor (including case, propellant, igniter and nozzle), structure, separation systems, operational flight instrumentation, recovery avionics, pyrotechnics
Pyrotechnics
Pyrotechnics is the science of using materials capable of undergoing self-contained and self-sustained exothermic chemical reactions for the production of heat, light, gas, smoke and/or sound...

, deceleration system, thrust vector
Thrust vectoring
Thrust vectoring, also thrust vector control or TVC, is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine or motor in order to control the attitude or angular velocity of the vehicle....

 control system and range safety
Range safety
In rocketry, range safety is assured by the systems which protect people and assets on the rocket range in cases when a launch vehicle might endanger them. Range safety is usually the responsibility of a Range Safety Officer...

 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' applies to the entire rocket assembly, which includes the recovery parachutes, electronic instrumentation, separation rockets, range safety destruct system, and thrust vector control. The term 'solid rocket motor' applies to the propellant, case, igniter and nozzle.

Each booster is 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 is attached to the external tank at the forward end of the SRB's forward skirt. On the launch pad, each booster also is attached to the mobile launcher platform at the aft skirt by four frangible nut
Frangible nut
The frangible nut, commonly confused with an explosive bolt, is a component used in many industries, but most commonly by NASA to sever mechanical connections. It is, by definition, an explosively-splittable nut...

s that are severed at lift-off.

The boosters are composed of seven individually manufactured steel segments. These are assembled in pairs by the manufacturer, and then shipped to Kennedy Space Center by rail for final assembly. The segments are fixed together using circumferential tang, clevis, and clevis pin
Clevis pin
A clevis fastener is a three piece fastener system consisting of a clevis, clevis pin, and tang. The clevis is a U-shaped piece that has holes at the end of the prongs to accept the clevis pin. The clevis pin is similar to a bolt, but is only partially threaded or unthreaded with a cross-hole for a...

 fastening, and sealed with three O-ring
O-ring
An O-ring, also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a disc-shaped cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.The O-ring...

s (two prior to the Challenger Disaster in 1986) and heat-resistant putty.

Hold-down posts

Each solid rocket booster has four hold-down posts that fit into corresponding support posts on the mobile launcher platform. Hold-down bolts
Screw
A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...

 hold the SRB and launcher platform posts together. Each bolt has a nut at each end, the top one being a frangible nut
Frangible nut
The frangible nut, commonly confused with an explosive bolt, is a component used in many industries, but most commonly by NASA to sever mechanical connections. It is, by definition, an explosively-splittable nut...

. The top nut contains two NASA standard detonator
NASA standard detonator
The NASA Standard Detonator is a device used by NASA for applications where a charge must be detonated, usually in conjunction with frangible nuts as a release mechanism. NSDs have been used since the Gemini program, and were used for the Space Shuttle program, including the Solid Rocket Booster ...

s (NSDs), which are ignited at solid rocket motor ignition commands.

When the two NSDs are ignited at each hold down, the hold-down bolt travels downward because of the release of tension in the bolt (pretensioned before launch), NSD gas pressure and gravity. The bolt is stopped by the stud deceleration stand, which contains sand. The SRB bolt is 28 in (711.2 mm) long and is 3.5 in (88.9 mm) in diameter. The frangible nut is captured in a blast container.

The solid rocket motor ignition commands are issued by the orbiter's computers through the master events controllers to the hold-down pyrotechnic initiator controllers (PICs) on the mobile launcher platform
Mobile Launcher Platform
The Mobile Launcher Platform or MLP is one of three two-story structures used by NASA to support the Space Shuttle stack during its transportation from the Vehicle Assembly Building to Launch Pad 39-A at the Kennedy Space Center as well as serve as the vehicle's launch platform...

. They provide the ignition to the hold-down NSDs. The launch processing system monitors the SRB hold- down PICs for low voltage during the last 16 seconds before launch. PIC low voltage will initiate a launch hold.

Electrical power distribution

Electrical power distribution in each SRB consists of orbiter supplied main DC
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...

 bus power to each SRB via SRB buses labeled A, B and C. Orbiter main DC buses A, B and C supply main DC bus power to corresponding SRB buses A, B and C. In addition, orbiter main DC bus C supplies backup power to SRB buses A and B, and orbiter bus B supplies backup power to SRB bus C. This electrical power distribution arrangement allows all SRB buses to remain powered in the event one orbiter main bus fails.

The nominal operating voltage is 28±4 volts DC.

Hydraulic power units

There are two self-contained, independent Hydraulic Power Units (HPUs) on each SRB. Each HPU consists of an auxiliary power unit
Auxiliary power unit
An auxiliary power unit is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft, as well as some large land vehicles.-Function:...

 (APU), fuel supply module, hydraulic pump
Pump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...

, hydraulic reservoir and hydraulic fluid
Hydraulic fluid
Hydraulic fluids, also called hydraulic liquids, are the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water...

 manifold assembly. The APUs are fueled by hydrazine
Hydrazine
Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...

 and generate mechanical shaft power to drive a hydraulic pump that produces hydraulic pressure for the SRB hydraulic system. The two separate HPUs and two hydraulic systems are located on the aft end of each SRB between the SRB nozzle and aft skirt. The HPU components are mounted on the aft skirt between the rock and tilt actuators. The two systems operate from T minus 28 seconds until SRB separation from the orbiter and external tank. The two independent hydraulic systems are connected to the rock and tilt servo
Servomechanism
thumb|right|200px|Industrial servomotorThe grey/green cylinder is the [[Brush |brush-type]] [[DC motor]]. The black section at the bottom contains the [[Epicyclic gearing|planetary]] [[Reduction drive|reduction gear]], and the black object on top of the motor is the optical [[rotary encoder]] for...

actuators.

The HPU controller electronics are located in the SRB aft integrated electronic assemblies on the aft external tank attach rings.

The HPUs and their fuel systems are isolated from each other. Each fuel supply module (tank) contains 22 lb (10 kg) of hydrazine. The fuel tank is pressurized with gaseous nitrogen at 400 psi (2.8 MPa), which provides the force to expel (positive expulsion) the fuel from the tank to the fuel distribution line, maintaining a positive fuel supply to the APU throughout its operation.

In the APU, a fuel pump boosts the hydrazine pressure and feeds it to a gas generator. The gas generator catalytically decomposes the hydrazine into hot, high-pressure gas; a two-stage turbine converts this into mechanical power, driving a gearbox. The waste gas, now cooler and at low pressure, is passed back over the gas generator housing to cool it before being dumped overboard. The gearbox drives the fuel pump, its own lubrication pump, and the HPU hydraulic pump. As described so far, the system could not self-start, since the fuel pump is driven by the turbine it supplies fuel to. Accordingly, a bypass line goes around the pump and feeds the gas generator using the nitrogen tank pressure until the APU speed is such that the fuel pump outlet pressure exceeds that of the bypass line, at which point all the fuel is supplied to the fuel pump.

When the APU speed reaches 100%, the APU primary control valve closes, and the APU speed is controlled by the APU controller electronics. If the primary control valve logic fails to the open state, the secondary control valve assumes control of the APU at 112% speed.

Each HPU on an SRB is connected to both servo
Servomechanism
thumb|right|200px|Industrial servomotorThe grey/green cylinder is the [[Brush |brush-type]] [[DC motor]]. The black section at the bottom contains the [[Epicyclic gearing|planetary]] [[Reduction drive|reduction gear]], and the black object on top of the motor is the optical [[rotary encoder]] for...

actuators on that SRB. One HPU serves as the primary hydraulic source for the servoactuator, and the other HPU serves as the secondary hydraulics for the servoactuator. Each servoactuator has a switching valve that allows the secondary hydraulics to power the actuator if the primary hydraulic pressure drops below 2050 psi (14.1 MPa). A switch contact on the switching valve will close when the valve is in the secondary position. When the valve is closed, a signal is sent to the APU controller that inhibits the 100% APU speed control logic and enables the 112% APU speed control logic. The 100-percent APU speed enables one APU/HPU to supply sufficient operating hydraulic pressure to both servoactuators of that SRB.

The APU 100-percent speed corresponds to 72,000 rpm, 110% to 79,200 rpm, and 112% to 80,640 rpm.

The hydraulic pump speed is 3,600 rpm and supplies hydraulic pressure of 3050 +/- 50 psi (21 +/- 0.34473786465 MPa). A high pressure relief valve
Relief valve
The relief valve is a type of valve used to control or limit the pressure in a system or vessel which can build up by a process upset, instrument or equipment failure, or fire....

 provides overpressure protection to the hydraulic system and relieves at 3750 psi (25.9 MPa).

The APUs/HPUs and hydraulic systems are reusable for 20 missions.

Thrust vector control

Each SRB has two hydraulic gimbal
Gimbal
A gimbal is a pivoted support that allows the rotation of an object about a single axis. A set of two gimbals, one mounted on the other with pivot axes orthogonal, may be used to allow an object mounted on the innermost gimbal to remain immobile regardless of the motion of its support...

 servoactuators: one for roll and one for tilt. The servoactuators provide the force and control to gimbal the nozzle for thrust vector control.

The space shuttle ascent thrust vector
Thrust vectoring
Thrust vectoring, also thrust vector control or TVC, is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine or motor in order to control the attitude or angular velocity of the vehicle....

 control portion of the flight control system directs the thrust of the three shuttle main engines and the two SRB nozzles to control shuttle attitude and trajectory during lift- off and ascent. Commands from the guidance system are transmitted to the ATVC (Ascent Thrust Vector Control) drivers, which transmit signals proportional to the commands to each servoactuator of the main engines and SRBs. Four independent flight control system channels and four ATVC channels control six main engine and four SRB ATVC drivers, with each driver controlling one hydraulic port on each main and SRB servoactuator.

Each SRB servoactuator consists of four independent, two- stage servovalves that receive signals from the drivers. Each servovalve controls one power spool in each actuator, which positions an actuator ram and the nozzle to control the direction of thrust.

The four servovalves in each actuator provide a force summed majority voting arrangement to position the power spool. With four identical commands to the four servovalves, the actuator force-sum action prevents a single erroneous command from affecting power ram motion. If the erroneous command persists for more than a predetermined time, differential pressure sensing activates a selector valve to isolate and remove the defective servovalve hydraulic pressure, permitting the remaining channels and servovalves to control the actuator ram spool.

Failure monitors are provided for each channel to indicate which channel has been bypassed. An isolation valve on each channel provides the capability of resetting a failed or bypassed channel.

Each actuator ram is equipped with transducer
Transducer
A transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...

s for position feedback to the thrust vector control system. Within each servoactuator ram is a splashdown load relief assembly to cushion the nozzle at water splashdown and prevent damage to the nozzle flexible bearing.

Rate gyro assemblies

Each SRB contains two Rate gyro
Rate gyro
A rate gyro is a type of gyroscope, which rather than indicating direction, indicates the rate of change of angle with time. If a gyro has only one gimbal ring, with consequently only two planes of freedom, it can be adapted for use as a rate gyro to measure a rate of angular movement.Rate gyros...

 assemblies (RGAs), with each RGA containing one pitch and one yaw gyro. These provide an output proportional to angular rates about the pitch and yaw axes to the orbiter computers and guidance, navigation and control system during first-stage ascent flight in conjunction with the orbiter roll rate gyros until SRB separation. At SRB separation, a switchover is made from the SRB RGAs to the orbiter RGAs.

The SRB RGA rates pass through the orbiter flight aft multiplexers/demultiplexers to the orbiter GPCs. The RGA rates are then mid-value-selected in redundancy management to provide SRB pitch and yaw rates to the user software. The RGAs are designed for 20 missions.

Propellant

The propellant mixture in each SRB motor consists of ammonium perchlorate
Ammonium perchlorate
Ammonium perchlorate is an inorganic compound with the formula NH4ClO4. It is the salt of perchloric acid and ammonia. It is a powerful oxidizer, which is why its main use is in solid propellants...

 (oxidizer, 69.6% by weight), aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 (fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

, 16%), iron oxide
Iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,...

 (a catalyst, 0.4%), a polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

 (such as PBAN
PBAN
Polybutadiene acrylonitrile copolymer, also noted as polybutadiene — acrylic acid — acrylonitrile terpolymer.This was the binder formulation widely used on the 1960-70's big boosters...

 or HTPB, serving as a binder that holds the mixture together and acting as secondary fuel, 12.04%), and an epoxy
Epoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....

 curing agent (1.96%). This propellant is commonly referred to as Ammonium Perchlorate Composite Propellant
Ammonium Perchlorate Composite Propellant
Ammonium perchlorate composite propellant is a modern solid rocket propellant used in both manned and unmanned rocket vehicles. It differs from many traditional solid rocket propellants such as black powder or Zinc-Sulfur, not only in chemical composition and overall performance, but also by the...

, or simply APCP. This mixture develops a specific impulse
Specific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...

 of 242 seconds at sea level or 268 seconds in a vacuum.

The main fuel, aluminum, is used because it has a reasonable specific energy density of about 31.0MJ/kg, but a high volumetric energy density, and is difficult to accidentally ignite.

The propellant has an 11-point star-shaped perforation in the forward motor segment and a double-truncated-cone
Cone (geometry)
A cone is an n-dimensional geometric shape that tapers smoothly from a base to a point called the apex or vertex. Formally, it is the solid figure formed by the locus of all straight line segments that join the apex to the base...

 perforation in each of the aft segments and aft closure. This configuration provides high thrust at ignition and then reduces the thrust by approximately a third 50 seconds after lift-off to avoid overstressing the vehicle during maximum dynamic pressure
Max Q
In aerospace engineering, the maximum dynamic pressure, often referred to as maximum Q or max Q, is the point at which aerodynamic stress on a vehicle in atmospheric flight is maximized...

 (Max Q).

Ignition

SRB ignition can occur only when a manual lock pin from each SRB safe and arm device has been removed. The ground crew removes the pin during prelaunch activities. At T minus five minutes, the SRB safe and arm device is rotated to the arm position. The solid rocket motor ignition commands are issued when the three Space Shuttle Main Engine
Space Shuttle main engine
The RS-25, otherwise known as the Space Shuttle Main Engine , is a reusable liquid-fuel rocket engine built by Pratt & Whitney Rocketdyne for the Space Shuttle, running on liquid hydrogen and oxygen. Each Space Shuttle was propelled by three SSMEs mated to one powerhead...

s (SSMEs) are at or above 90-percent rated thrust, no SSME fail and/or SRB ignition Pyrotechnic Initiator Controller (PIC) low voltage is indicated and there are no holds from the Launch Processing System (LPS).

The solid rocket motor ignition commands are sent by the orbiter computers through the Master Events Controllers (MECs) to the safe and arm device NSDs
NASA standard detonator
The NASA Standard Detonator is a device used by NASA for applications where a charge must be detonated, usually in conjunction with frangible nuts as a release mechanism. NSDs have been used since the Gemini program, and were used for the Space Shuttle program, including the Solid Rocket Booster ...

 in each SRB. A PIC single-channel capacitor discharge device controls the firing of each pyrotechnic device. Three signals must be present simultaneously for the PIC to generate the pyro firing output. These signals — arm, fire 1 and fire 2 — originate in the orbiter general-purpose computers
IBM AP-101
The IBM AP-101 is an avionics computer, used most notably in the U.S. Space Shuttle, but since also in the B-52 and B-1B bombers and the F-15 fighter, among others. When it was designed, it was a high-performance pipelined processor with core memory...

 (GPCs) and are transmitted to the MECs. The MECs reformat them to 28 volt DC signals for the PICs. The arm signal charges the PIC capacitor to 40 volts DC (minimum of 20 volts DC).

The GPC launch sequence also controls certain critical main propulsion system valves and monitors the engine ready indications from the SSMEs. The MPS start commands are issued by the onboard computers at T minus 6.6 seconds (staggered start engine three, engine two, engine one all approximately within 0.25 of a second), and the sequence monitors the thrust buildup of each engine. All three SSMEs must reach the required 90% thrust within three seconds; otherwise, an orderly shutdown is commanded and safing functions are initiated.

Normal thrust buildup to the required 90% thrust level will result in the SSMEs being commanded to the lift off position at T minus three seconds as well as the fire 1 command being issued to arm the SRBs. At T minus three seconds, the vehicle base bending load modes are allowed to initialize (movement of approximately 25.5 in (647.7 mm) measured at the tip of the external tank, with movement towards the external tank).

The fire 2 commands cause the redundant NSDs to fire through a thin barrier seal down a flame tunnel. This ignites a pyro booster charge, which is retained in the safe and arm device behind a perforated plate. The booster charge ignites the propellant in the igniter initiator; and combustion products of this propellant ignite the solid rocket motor initiator, which fires down the entire vertical length of the solid rocket motor igniting the solid rocket motor propellant along its entire surface area instantaneously.

At T minus zero, the two SRBs are ignited, under command of the four onboard computers; separation of the four explosive bolts on each SRB is initiated; the two T-0 umbilicals (one on each side of the spacecraft) are retracted; the onboard master timing unit, event timer and mission event timers are started; the three SSMEs are at 100%; and the ground launch sequence is terminated.

Separation

The SRBs are jettisoned from the space shuttle at high altitude (about 146,000 feet or 44.5km). SRB separation is initiated when the three solid rocket motor chamber pressure transducers are processed in the redundancy management middle value select and the head-end chamber pressure of both SRBs is less than or equal to 50 psi (344.7 kPa). A backup cue is the time elapsed from booster ignition.

The separation sequence is initiated, commanding the thrust vector control actuators to the null position and putting the main propulsion system into a second-stage configuration (0.8 second from sequence initialization), which ensures the thrust of each SRB is less than 100000 lbf (444.8 kN). Orbiter yaw attitude is held for four seconds, and SRB thrust drops to less than 60000 lbf (266.9 kN).

The SRBs separate from the external tank within 30 milliseconds of the ordnance firing command.

The forward attachment point consists of a ball (SRB) and socket (External Tank (ET)) held together by one bolt. The bolt contains one NSD pressure cartridge at each end. The forward attachment point also carries the range safety system cross-strap wiring connecting each SRB RSS and the ET RSS with each other.

The aft attachment points consist of three separate struts: upper, diagonal and lower. Each strut contains one bolt with an NSD pressure cartridge at each end. The upper strut also carries the umbilical interface between its SRB and the external tank and on to the orbiter.

There are four booster separation motors on each end of each SRB. The BSMs separate the SRBs from the external tank. The solid rocket motors in each cluster of four are ignited by firing redundant NSD pressure cartridges into redundant confined detonating fuse manifolds.

The separation commands issued from the orbiter by the SRB separation sequence initiate the redundant NSD pressure cartridge in each bolt and ignite the BSMs to effect a clean separation.

Range safety system

A range safety
Range safety
In rocketry, range safety is assured by the systems which protect people and assets on the rocket range in cases when a launch vehicle might endanger them. Range safety is usually the responsibility of a Range Safety Officer...

 system (RSS) provides for destruction of a rocket or part of it with on-board explosives by remote command if the rocket is out of control, in order to limit the danger to people on the ground from crashing pieces, explosions, fire, poisonous substances, etc. To date, the RSS has only been activated once – during the Space Shuttle Challenger disaster
Space Shuttle Challenger disaster
The Space Shuttle Challenger disaster occurred on January 28, 1986, when Space Shuttle Challenger broke apart 73 seconds into its flight, leading to the deaths of its seven crew members. The spacecraft disintegrated over the Atlantic Ocean, off the coast of central Florida at 11:38 am EST...

 (37 seconds after the breakup of the vehicle).

The shuttle vehicle has two RSSs, one in each SRB. Both are capable of receiving two command messages (arm and fire) transmitted from the ground station. The RSS is used only when the shuttle vehicle violates a launch trajectory red line.

An RSS consists of two antenna couplers, command receivers/decoders, a dual distributor, a safe and arm device with two NASA standard detonator
NASA standard detonator
The NASA Standard Detonator is a device used by NASA for applications where a charge must be detonated, usually in conjunction with frangible nuts as a release mechanism. NSDs have been used since the Gemini program, and were used for the Space Shuttle program, including the Solid Rocket Booster ...

s (NSD), two confined detonating fuse manifolds (CDF), seven CDF assemblies and one linear-shaped charge (LSC).

The antenna couplers provide the proper impedance for radio frequency and ground support equipment commands. The command receivers are tuned to RSS command frequencies and provide the input signal to the distributors when an RSS command is sent. The command decoders use a code plug to prevent any command signal other than the proper command signal from getting into the distributors. The distributors contain the logic to supply valid destruct commands to the RSS pyrotechnics.

The NSDs provide the spark to ignite the CDF, which in turn ignites the LSC for shuttle vehicle destruction. The safe and arm device provides mechanical isolation between the NSDs and the CDF before launch and during the SRB separation sequence.

The first message, called arm, allows the onboard logic to enable a destruct and illuminates a light on the flight deck display and control panel at the commander and pilot station. The second message transmitted is the fire command.

The SRB distributors in the SRBs are cross-strapped together. Thus, if one SRB received an arm or destruct signal, the signal would also be sent to the other SRB.

Electrical power from the RSS battery in each SRB is routed to RSS system A. The recovery battery in each SRB is used to power RSS system B as well as the recovery system in the SRB. The SRB RSS is powered down during the separation sequence, and the SRB recovery system is powered up.

Descent and recovery

The SRBs are jettisoned from the shuttle system at 2 minutes and an altitude of about 146,000 feet (44.5 km). After continuing to rise to about 220,000 feet (67.1 km), the SRBs begin to fall back to earth and once back in the atmosphere are slowed by a parachute system to prevent damage on ocean impact. A command is sent from the orbiter to the SRB just before separation to apply battery power to the recovery logic network. A second, simultaneous command arms the three nose cap thrusters (for deploying the pilot and drogue parachutes), the frustum
Frustum
In geometry, a frustum is the portion of a solid that lies between two parallel planes cutting it....

 ring detonator (for main parachute deployment), and the main parachute disconnect ordnance.

The recovery sequence begins with the operation of the high-altitude baroswitch, which triggers the pyrotechnic nose cap thrusters. This ejects the nose cap, which deploys the pilot parachute. Nose cap separation occurs at a nominal altitude of 15704 ft (4,786.6 m), about 218 seconds after SRB separation. The 11.5 ft (3.5 m) diameter conical ribbon pilot parachute provides the force to pull lanyards attached to cut knives, which cut the loop securing the drogue retention straps. This allows the pilot chute to pull the drogue pack from the SRB, causing the drogue suspension lines to deploy from their stored position. At full extension of the twelve 105 ft (32 m) suspension lines, the drogue deployment bag is stripped away from the canopy, and the 54 ft (16.5 m) diameter conical ribbon drogue parachute inflates to its initial reefed condition. The drogue disreefs twice after specified time delays (using redundant 7 and 12-second reefing line cutters), and it reorients/stabilizes the SRB for main chute deployment. The drogue parachute has a design load of approximately 315000 lb (142,881.6 kg) and weighs approximately 1200 lb (544.3 kg).

After the drogue chute has stabilized the SRB in a tail-first attitude, the frustum is separated from the forward skirt by a pyrotechnic charge triggered by the low-altitude baroswitch at a nominal altitude of 5500 ft (1,676.4 m) about 243 seconds after SRB separation. The frustum is then pulled away from the SRB by the drogue chute. The main chute suspension lines are pulled out from deployment bags that remain in the frustum. At full extension of the lines, which are 203 ft (61.9 m) long, the three main chutes are pulled from their deployment bags and inflate to their first reefed condition. The frustum and drogue parachute continue on a separate trajectory to splashdown. After specified time delays (using redundant 10 and 17-second reefing line cutters), the main chute reefing lines are cut and the chutes inflate to their second reefed and full open configurations. The main chute cluster decelerates the SRB to terminal conditions. Each of the 136 ft (41.5 m) diameter, 20-degree conical ribbon parachutes have a design load of approximately 195000 lb (88,450.5 kg) and each weighs approximately 2180 lb (988.8 kg). These chutes are the largest that have ever been used — both in deployed size and load weight. The RSRM nozzle extension is severed by a pyrotechnic charge about 20 seconds after frustum separation.

Water impact occurs about 279 seconds after SRB separation at a nominal velocity of 76 feet per second (23.2 m/s). The water impact range is approximately 130 nmi (240.8 km) off the eastern coast of Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

. Because the parachutes provide for a nozzle-first impact, air is trapped in the empty (burned out) motor casing, causing the booster to float with the forward end approximately 30 feet (9.1 m) out of the water.
Formerly, the main chutes were released from the SRB at impact using a parachute release nut ordnance system (residual loads in the main chutes would deploy the parachute attach fittings with floats tethered to each fitting). The current design keeps the main chutes attached during water impact (initial impact and slapdown). Salt Water Activated Release (SWAR) devices are now incorporated into the main chute riser lines to simplify recovery efforts and reduce damage to the SRB. The drogue deployment bag/pilot parachutes, drogue parachutes and frustums, each main chute, and the SRBs are buoyant and are recovered.

Specially fitted NASA recovery ship
NASA recovery ship
-References:...

s, the Freedom Star and the Liberty Star, recover the SRBs and descent/recovery hardware. Once the boosters are located, the Diver Operated Plug (DOP) is maneuvered by divers into place to plug the SRB nozzle and dewater the motor case. Dewatering, pumping air into and water out of the SRB, causes the SRB to change from a nose-up floating position to a horizontal attitude more suitable for towing. The retrieval vessels then tow the boosters and other objects recovered back to Kennedy Space Center
Kennedy Space Center
The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...

.

Challenger disaster

The Challenger accident
Space Shuttle Challenger disaster
The Space Shuttle Challenger disaster occurred on January 28, 1986, when Space Shuttle Challenger broke apart 73 seconds into its flight, leading to the deaths of its seven crew members. The spacecraft disintegrated over the Atlantic Ocean, off the coast of central Florida at 11:38 am EST...

 originated with a design flaw and system failure of one of its SRBs. The cause of the accident was found by the Rogers Commission
Rogers Commission Report
The Rogers Commission Report was created by a Presidential Commission charged with investigating the Space Shuttle Challenger disaster during its 10th mission, STS-51-L...

 to be a faulty design of the SRB joints compounded by unusually cold weather the morning of the flight. The commission found that the large rubber "O-rings" in SRB joints were not effective at cold temperatures like those of the January 1986 morning of the accident (36 °F (2.2 °C)). A cold weather-compromised joint in the right SRB failed at launch and eventually allowed hot gases from within that rocket booster to sear a hole into the adjacent main external fuel tank and also weaken the lower strut holding the SRB to the external tank. The leak in the SRB joint caused a catastrophic failure of the lower strut and partial detachment of the SRB, causing a collision between the SRB and external tank. With a disintegrating external tank and severely off-axis thrust from the right SRB, the Space Shuttle stack disintegrated due to large, abnormal atmospheric forces.

During the subsequent downtime, detailed structural analyses were performed on critical structural elements of the SRB. Analyses were primarily focused in areas where anomalies had been noted during postflight inspection of recovered hardware.

One of the areas was the attachment ring where the SRBs are connected to the external tank. Areas of distress were noted in some of the fasteners where the ring attaches to the SRB motor case. This situation was attributed to the high loads encountered during water impact. To correct the situation and ensure higher strength margins during ascent, the attach ring was redesigned to encircle the motor case completely (360 degrees). Previously, the attachment ring formed a 'C' shape and encircled the motor case just 270 degrees.

Additionally, special structural tests were performed on the aft skirt. During this test program, an anomaly occurred in a critical weld
Weld
Weld most commonly refers to a joint formed by welding.Weld may also refer to:-People:* Weld family, an extended family of New England** Theodore Dwight Weld** Tuesday Weld* Weld-Blundell family* Cecil Weld-Forester, 1st Baron Forester...

 between the hold-down post and skin of the skirt. A redesign was implemented to add reinforcement brackets and fittings in the aft ring of the skirt.

These two modifications added approximately 450 lb (204.1 kg) to the weight of each SRB. The result is called a "Redesigned Solid Rocket Motor" (RSRM).

Construction

The prime contractor for the SRB motors is ATK Launch System's Wasatch Division based in Brigham City, Utah
Brigham City, Utah
Brigham City is a city in Box Elder County, Utah, United States. The population was 17,899 at the 2010 census. It is the county seat of Box Elder County. It lies on the western slope of the Wellsville Mountains, a branch of the Wasatch Range at the western terminus of Box Elder Canyon...

.

United Space Alliance
United Space Alliance
United Space Alliance is a spaceflight operations company. USA is a joint venture which was established in August 1995 as a Limited Liability Company , equally owned by Boeing and Lockheed Martin. The company is headquartered in Houston, Texas and, employed approximately 8,800 people in Texas,...

's Solid Rocket Booster Element division is the prime contractor for SRB assembly, checkout and refurbishment for all non-solid-rocket-motor components and for SRB integration.

Many other companies supply various components for the SRBs:
  • Parker-Abex Corp. of Kalamazoo, Michigan
    Kalamazoo, Michigan
    The area on which the modern city stands was once home to Native Americans of the Hopewell culture, who migrated into the area sometime before the first millennium. Evidence of their early residency remains in the form of a small mound in downtown's Bronson Park. The Hopewell civilization began to...

     (hydraulic pumps)
  • Aerojet
    Aerojet
    Aerojet is an American rocket and missile propulsion manufacturer based primarily in Rancho Cordova, California with divisions in Redmond, Washington, Orange, Gainesville and Camden, Arkansas. Aerojet is owned by GenCorp. They are the only US propulsion company that provides both solid rocket...

     of Redmond, Washington
    Redmond, Washington
    Redmond is a city in King County, Washington, United States, located east of Seattle. The population was 54,144 at the 2010 census,up from 45,256 in 2000....

     (hydrazine gas generators)
  • Arde Inc. of Mahwah, New Jersey
    Mahwah, New Jersey
    Mahwah is a township in Bergen County, New Jersey, United States. As of the 2010 United States Census, the township population was 25,890. The name Mahwah is derived from the Lenni Lenape word "mawewi" which means "Meeting Place" or "Place Where Paths Meet".The area that is now Mahwah was...

     (hydrazine fuel supply modules)
  • Arkwin Industries Inc. of Westbury, New York
    Westbury, New York
    Westbury incorporated in 1932 as a village in Nassau County, New York in the United States. The population was 15,146 at the 2010 census.The Village of Westbury is in the Town of North Hempstead....

     (hydraulic reservoirs)
  • Aydin Vector Division of Newtown, Pennsylvania
    Newtown, Pennsylvania
    Newtown is the name of some places in the U.S. state of Pennsylvania:* Newtown, Bucks County, Pennsylvania* Newtown Township, Bucks County, Pennsylvania* Newtown, Lehigh County, Pennsylvania* Newtown, Schuylkill County, Pennsylvania...

    (integrated electronic assemblies)
  • Bendix Corp. of Teterboro, New Jersey
    Teterboro, New Jersey
    Teterboro is a borough in Bergen County, New Jersey, United States. As of the 2010 United States Census, the borough population was 67, making it the fourth smallest municipality, by population, in New Jersey....

     (integrated electronic assemblies)
  • Consolidated Controls Corp. of El Segundo, California
    El Segundo, California
    El Segundo is a city in Los Angeles County, California, United States. Located on the Santa Monica Bay, it was incorporated on January 18, 1917, and is one of the Beach Cities of Los Angeles County and part of the South Bay Cities Council of Governments...

     (hydrazine)
  • Eldec Corp. of Lynnwood, Washington
    Lynnwood, Washington
    Lynnwood is a city in Snohomish County, Washington, United States. The population was 35,836 at the 2010 census, making it the fourth largest in Snohomish County and twenty-ninth largest in Washington State. The city is a mix of urban, suburban, small city, crossroads and bedroom community to many...

     (integrated electronic assemblies)
  • Explosive Technology of Fairfield, California
    Fairfield, California
    Fairfield is a city located in Solano County in Northern California, USA. It is generally considered the midpoint between the cities of San Francisco and Sacramento, approximately from the city center of both cities, approximately from the city center of Oakland, less than from Napa Valley, 18...

     (CDF manifolds)
  • Gaco Western of Seattle, Washington
    Seattle, Washington
    Seattle is the county seat of King County, Washington. With 608,660 residents as of the 2010 Census, Seattle is the largest city in the Northwestern United States. The Seattle metropolitan area of about 3.4 million inhabitants is the 15th largest metropolitan area in the country...

     (Hypalon Paint)
  • Lockheed Martin
    Lockheed Martin
    Lockheed Martin is an American global aerospace, defense, security, and advanced technology company with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It is headquartered in Bethesda, Maryland, in the Washington Metropolitan Area....

     (formerly Martin Marietta
    Martin Marietta
    Martin Marietta Corporation was an American company founded in 1961 through the merger of The Martin Company and American-Marietta Corporation. The combined company became a leader in chemicals, aerospace, and electronics. In 1995, it merged with Lockheed Corporation to form Lockheed Martin. The...

    ) of Denver, Colorado
    Denver, Colorado
    The City and County of Denver is the capital and the most populous city of the U.S. state of Colorado. Denver is a consolidated city-county, located in the South Platte River Valley on the western edge of the High Plains just east of the Front Range of the Rocky Mountains...

     (pyro initiator controllers)
  • Moog Inc. of East Aurora, New York
    East Aurora, New York
    East Aurora is a village in Erie County, New York, United States, southeast of Buffalo. The Village of East Aurora lies in the eastern half of the Town of Aurora.The population was 6,673 at the 2000 census...

     (servoactuators, fuel isolation valves)
  • Motorola
    Motorola
    Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...

     of Scottsdale, Arizona
    Scottsdale, Arizona
    Scottsdale is a city in the eastern part of Maricopa County, Arizona, United States, adjacent to Phoenix. According to the U.S. Census Bureau, as of 2010 the population of the city was 217,385...

     (range safety receivers)
  • Pioneer Parachute Company of Manchester, Connecticut
    Manchester, Connecticut
    Manchester is a township and city in Hartford County, Connecticut, United States. As of the 2010 census, the town had a total population of 58,241.- History :...

     (parachutes)
  • Sperry Rand Flight Systems of Phoenix, Arizona
    Phoenix, Arizona
    Phoenix is the capital, and largest city, of the U.S. state of Arizona, as well as the sixth most populated city in the United States. Phoenix is home to 1,445,632 people according to the official 2010 U.S. Census Bureau data...

     (multiplexers / demultiplexers)
  • Teledyne
    Teledyne
    Teledyne Technologies Incorporated is an industrial conglomerate primarily based in the United States but with global operations. It was founded in 1960, as Teledyne, Inc., by Henry Singleton and George Kozmetsky....

     of Lewisburg, Tennessee
    Lewisburg, Tennessee
    Lewisburg is a city in Marshall County, Tennessee, United States. The population was 10,413 at the 2000 census. It is the county seat of Marshall County...

     (location aid transmitters)
  • ATK Launch Systems Corp. of Brigham City, Utah
    Brigham City, Utah
    Brigham City is a city in Box Elder County, Utah, United States. The population was 17,899 at the 2010 census. It is the county seat of Box Elder County. It lies on the western slope of the Wellsville Mountains, a branch of the Wasatch Range at the western terminus of Box Elder Canyon...

     (separation motors)
  • Hamilton Sundstrand
    Hamilton Sundstrand
    Hamilton Sundstrand, is a global corporation that manufactures and supports aerospace and industrial products for worldwide markets. It was formed from the merger of Hamilton Standard and Sundstrand Corporation in 1999. A subsidiary of United Technologies Corporation, HS is headquartered in Windsor...

     of Windsor Locks, Connecticut
    Windsor Locks, Connecticut
    Windsor Locks is a town located in Hartford County, Connecticut, United States. As of the 2000 census, its population was 12,043. It is the site of Bradley International Airport, which serves the Greater Hartford-Springfield region. It is also the site of the New England Air Museum...

     (auxiliary power units)
  • VACCO Industries of South El Monte, California
    El Monte, California
    El Monte is a residential, industrial, and commercial city in Los Angeles County, California, United States. The city's slogan is "Welcome to Friendly El Monte," and historically is known as "The End of the Santa Fe Trail." As of the 2010 census, the city had a total population of 113,475,...

     (safe and arm device)
  • Voss Industries of Cleveland, Ohio
    Cleveland, Ohio
    Cleveland is a city in the U.S. state of Ohio and is the county seat of Cuyahoga County, the most populous county in the state. The city is located in northeastern Ohio on the southern shore of Lake Erie, approximately west of the Pennsylvania border...

     (SRB Retention Bands)

Advanced Solid Rocket Booster

NASA was planning on replacing the post-Challenger SRBs with a new Advanced Solid Rocket Booster (ASRB) to be built by Aerojet
Aerojet
Aerojet is an American rocket and missile propulsion manufacturer based primarily in Rancho Cordova, California with divisions in Redmond, Washington, Orange, Gainesville and Camden, Arkansas. Aerojet is owned by GenCorp. They are the only US propulsion company that provides both solid rocket...

 at a new facility, on the location of a canceled Tennessee Valley Authority
Tennessee Valley Authority
The Tennessee Valley Authority is a federally owned corporation in the United States created by congressional charter in May 1933 to provide navigation, flood control, electricity generation, fertilizer manufacturing, and economic development in the Tennessee Valley, a region particularly affected...

 nuclear power plant, at Yellow Creek, Mississippi. The ASRB would have produced additional thrust in order to increase shuttle payload, so that it could carry modules and construction components to the ISS. The ASRB program was canceled in 1993 in favor of continued use and improvement of the SRB.

Two ASRB casings can be found on the Space Shuttle Pathfinder
Space Shuttle Pathfinder
- External links :* *...

 on display at the United States Space & Rocket Center
United States Space & Rocket Center
The U.S. Space & Rocket Center in Huntsville, Alabama is a museum showcasing rockets, achievements, and artifacts of the U.S. space program. The facility is also home to United States Space Camp and Aviation Challenge...

 in Huntsville, Alabama
Huntsville, Alabama
Huntsville is a city located primarily in Madison County in the central part of the far northern region of the U.S. state of Alabama. Huntsville is the county seat of Madison County. The city extends west into neighboring Limestone County. Huntsville's population was 180,105 as of the 2010 Census....

.

Filament-wound cases

In the need to provide the necessary thrust to launch polar-orbiting shuttles from the SLC-6 launch pad at Vandenberg Air Force Base
Vandenberg Air Force Base
Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command ....

 in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, SRBs using filament-wound
Filament winding
Filament winding is a fabrication technique for manufacturing composite material, usually in the form of cylindrical structures. The process involves winding filaments under varying amounts of tension over a male mould or mandrel. The mandrel rotates while a carriage moves horizontally, laying...

 cases
(FWC) were designed to be more lightweight than the steel cases used on Kennedy Space Center-launched SRBs. Unlike the regular SRBs, which had the flawed field joint design that led to the Challenger Disaster in 1986, the FWC boosters had the "double tang" joint design (necessary to keep the boosters properly in alignment during the "twang" movement when the SSMEs are ignited prior to liftoff), but used the two O-ring seals. With the closure of SLC-6, the FWC boosters were scrapped by ATK and NASA, but their field joints, albeit modified to incorporate the current three O-ring seals and joint heaters, were later incorporated into the present-day field joints on the current SRMs.

Five-segment booster

Prior to the destruction of the Space Shuttle Columbia
Space Shuttle Columbia
Space Shuttle Columbia was the first spaceworthy Space Shuttle in NASA's orbital fleet. First launched on the STS-1 mission, the first of the Space Shuttle program, it completed 27 missions before being destroyed during re-entry on February 1, 2003 near the end of its 28th, STS-107. All seven crew...

 in 2003, NASA investigated the replacement of the current 4-segment SRBs with either a 5-segment SRB design or replacing them altogether with liquid "flyback" boosters using either Atlas V
Atlas V
Atlas V is an active expendable launch system in the Atlas rocket family. Atlas V was formerly operated by Lockheed Martin, and is now operated by the Lockheed Martin-Boeing joint venture United Launch Alliance...

 or Delta IV EELV technologies. The 5-segment SRB, which would have required little change to the current shuttle infrastructure, would have allowed the space shuttle to carry an additional 20000 lbs of payload in an International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

-inclination orbit, eliminate the dangerous "Return-to-Launch Site" (RTLS) and "Trans-Oceanic Abort
Space Shuttle abort modes
A Space Shuttle abort was an emergency procedure due to equipment failure on NASA's Space Shuttle, most commonly during ascent. A main engine failure is a typical abort scenario. There are fewer abort options during reentry and descent...

" (TAL) modes, and, by using a so-called "dog-leg maneuver", fly south-to-north polar orbiting flights from Kennedy Space Center. With the destruction of the Columbia, NASA has shelved the 5-segment SRB for the Shuttle Program, as the three surviving Orbiters, Discovery
Space Shuttle Discovery
Space Shuttle Discovery is one of the retired orbiters of the Space Shuttle program of NASA, the space agency of the United States, and was operational from its maiden flight, STS-41-D on August 30, 1984, until its final landing during STS-133 on March 9, 2011...

, Atlantis
Space Shuttle Atlantis
The Space Shuttle Atlantis is a retired Space Shuttle orbiter in the Space Shuttle fleet belonging to the National Aeronautics and Space Administration , the spaceflight and space exploration agency of the United States...

, and Endeavour
Space Shuttle Endeavour
Space Shuttle Endeavour is one of the retired orbiters of the Space Shuttle program of NASA, the space agency of the United States. Endeavour was the fifth and final spaceworthy NASA space shuttle to be built, constructed as a replacement for Challenger...

 were retired in 2011 after the completion of the International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

.

A five segment engineering test motor, ETM-03, was fired on October 23, 2003.

On September 10, 2009 a five-segment Space Shuttle SRB was static fired on the ground in ATK's desert testing area in Utah. This was the test of what was to be the first stage for the Ares I
Ares I
Ares I was the crew launch vehicle that was being developed by NASA as part of the Constellation Program. The name "Ares" refers to the Greek deity Ares, who is identified with the Roman god Mars...

 rocket.

Displays

Space Shuttle Solid Rocket Boosters are on display at the Kennedy Space Center Visitors Complex in Florida, the Stennis Space Center in Port St. Louis, Mississippi, United States Space & Rocket Center
United States Space & Rocket Center
The U.S. Space & Rocket Center in Huntsville, Alabama is a museum showcasing rockets, achievements, and artifacts of the U.S. space program. The facility is also home to United States Space Camp and Aviation Challenge...

, Huntsville, Alabama and at Thiokol Missile Systems in Brigham City, Utah.

Future and proposed uses

NASA plans to reuse the SRB designs and infrastructure in several Ares rockets. In 2005, NASA announced the Shuttle-Derived Launch Vehicle
Shuttle-Derived Launch Vehicle
Shuttle-Derived Launch Vehicle, or simply Shuttle-Derived Vehicle , is a term describing one of a wide array of concepts that have been developed for creating space launch vehicles from the components, technology and/or infrastructure of the Space Shuttle program. SDVs have also been part of...

 slated to carry the Orion Crew Exploration Vehicle into low-Earth orbit and later to the Moon. The SRB-derived Crew Launch Vehicle (CLV), named Ares I
Ares I
Ares I was the crew launch vehicle that was being developed by NASA as part of the Constellation Program. The name "Ares" refers to the Greek deity Ares, who is identified with the Roman god Mars...

, originally featured a modified standard 4-segment SRB for its first stage, while a liquid-fueled second stage, powered by a single, modified Space Shuttle Main Engine
Space Shuttle main engine
The RS-25, otherwise known as the Space Shuttle Main Engine , is a reusable liquid-fuel rocket engine built by Pratt & Whitney Rocketdyne for the Space Shuttle, running on liquid hydrogen and oxygen. Each Space Shuttle was propelled by three SSMEs mated to one powerhead...

, would have propelled the Orion into orbit.

The current design, initially introduced in 2006, and since revised, will feature the originally planned, but scrapped 5-segment SRB for its first-stage, with a second stage powered by an uprated J-2X
J-2 (rocket engine)
Rocketdyne's J-2 rocket engine was a major component of the Saturn V rocket used in the Apollo program to send men to the Moon. Five J-2 engines were used on the S-II second stage, and one J-2 was used on the S-IVB third stage. The S-IVB was also used as the second stage of the smaller Saturn IB...

 rocket engine derived from the J-2 engine used in Project Apollo
Project Apollo
The Apollo program was the spaceflight effort carried out by the United States' National Aeronautics and Space Administration , that landed the first humans on Earth's Moon. Conceived during the Presidency of Dwight D. Eisenhower, Apollo began in earnest after President John F...

 on the Saturn IB
Saturn IB
The Saturn IB was an American launch vehicle commissioned by the National Aeronautics and Space Administration for use in the Apollo program...

, Saturn V
Saturn V
The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...

, and Saturn INT-20
Saturn INT-20
The Saturn INT-20 was a proposed intermediate payload follow-on from the Apollo Saturn V launch vehicle. An interstage would be fitted on top of the S-IC stage to support the S-IVB stage, so it could be considered either a retrofitted Saturn IB with a more powerful first stage, or a stubby,...

 rockets. In place of the standard SRB nosecone, the Ares I would have a tapered interstage assembly connecting the booster proper with the second stage, an altitude control system derived from the Regulus missile system, and larger, heavier parachutes to lower the stage into the Atlantic Ocean for recovery.

Also introduced in 2005, was a heavy-lift
Heavy Lift Launch Vehicle
A Heavy Lift Launch Vehicle, or HLLV, is a launch vehicle capable of lifting more mass into Low Earth Orbit than Medium Lift or Mid-Heavy Lift Launch Vehicles.There is no universally accepted capability requirements for heavy-lift launch vehicles....

 Cargo Launch Vehicle (CaLV) named Ares V
Ares V
The Ares V was the planned cargo launch component of the Constellation program, which was to have replaced the Space Shuttle after its retirement in 2011. Ares V was also planned to carry supplies for a human presence on Mars...

. Early designs of the Ares V utilized five standard-production SSMEs and a pair of 5-segment boosters identical to those proposed for the Shuttle, but since then NASA had redesigned the boosters around the RS-68 rocket engine used on the Delta IV EELV system. Initially, NASA switched over to a system using the 5-segment boosters and a cluster of five RS-68s (which resulted in a widening of the Ares V core unit), but since then, NASA has further reconfigured the vehicle with six RS-68B engines (which would operate like the current SSMEs, but at half the price), with the boosters themselves becoming "5.5-Segment Boosters," with an additional half-segment to provide additional thrust at liftoff.

The current redesign will make the Ares V booster taller and more powerful than the now-retired Saturn V/INT-20, N-1, and Energia
Energia
Energia was a Soviet rocket that was designed by NPO Energia to serve as a heavy-lift expendable launch system as well as a booster for the Buran spacecraft. Control system main developer enterprise was the NPO "Electropribor"...

 rockets, and will allow the Ares V to place both the Earth Departure Stage
Earth Departure Stage
The Ares V Earth Departure Stage was a rocket stage which NASA planned to design at its Marshall Space Flight Center in Huntsville, Alabama as part of Project Constellation...

 and Altair spacecraft into Low-Earth orbit for later on-orbit assembly. Unlike the 5-segment SRB for the Ares I, the 5.5-segment boosters for the Ares V are to be identical in design, construction, and function to the current SRBs except for the extra segments. Although there is no final decision on the recovery or reuse of this system, it is most likely that the standard recovery process like that employed on the shuttle will be used. Like the current shuttle boosters, the Ares V boosters would fly an almost-identical flight trajectory from launch to splashdown.

The Constellation program, including Ares I and Ares V, was canceled in October 2010 by the passage of the 2010 NASA authorization bill. Existing Constellation contracts remain in place until Congress passes a new funding bill for 2012.

The DIRECT
DIRECT
DIRECT is a proposed alternative heavy lift launch vehicle architecture supporting NASA's Vision for Space Exploration, which would replace the space agency's planned Ares I and Ares V rockets...

proposal for a new, Shuttle-Derived Launch Vehicle, unlike the Ares I and Ares V boosters, uses a pair of classic 4-segment SRBs with the SSMEs used on the Shuttle.

External links

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