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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Space Shuttle Solid Rocket Booster | 3/9 | https://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Booster | reference | science, encyclopedia | 2026-05-05T13:22:36.055022+00:00 | kb-cron |
Each SRB had two hydraulic gimbal servoactuators, to move the nozzle up/down and side-to-side. This provided thrust vectoring to help control the vehicle in all three axes (roll, pitch, and yaw). The ascent thrust vector control portion of the flight control system directed 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 were transmitted to the Ascent Thrust Vector Control (ATVC) drivers, which transmitted signals proportional to the commands to each servoactuator of the main engines and SRBs. Four independent flight control system channels and four ATVC channels controlled six main engine and four SRB ATVC drivers, with each driver controlling one hydraulic port on each main and SRB servoactuator. Each SRB servoactuator consisted of four independent, two-stage servovalves that received signals from the drivers. Each servovalve controlled one power spool in each actuator, which positioned an actuator ram and the nozzle to control the direction of thrust. The four servovalves operating each actuator provided a force-summed majority-voting arrangement to position the power spool. With four identical commands to the four servovalves, the actuator force-sum action prevented, instantaneously, a single erroneous input affecting power ram motion. If differential-pressure sensing detected the erroneous input persisting over a predetermined time, an isolating valve would be selected, excluding it from the force-sum entirely. Failure monitors were provided for each channel to indicate which channel had been bypassed, and the isolation valve on each channel could be reset. Each actuator ram was equipped with transducers for position feedback to the thrust vector control system. Within each servoactuator ram was 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 contained three rate gyro assemblies (RGAs), with each RGA containing one pitch and one yaw gyro. These provided 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 was made from the SRB RGAs to the orbiter RGAs. The SRB RGA rates passed through the orbiter flight aft multiplexers/demultiplexers to the orbiter GPCs. The RGA rates were then mid-value-selected in redundancy management to provide SRB pitch and yaw rates to the user software. The RGAs were designed for 20 missions.
=== Segment cases === Made out of 2-cm-thick D6AC high-strength low-alloy steel.
=== Propellant ===
The rocket propellant mixture in each solid rocket motor consisted of ammonium perchlorate (oxidizer, 69.6% by weight), atomized aluminum powder (fuel, 16%), iron oxide (catalyst, 0.4%), PBAN (binder, also acts as fuel, 12.04%), and an epoxy curing agent (1.96%). This propellant is commonly referred to as ammonium perchlorate composite propellant (APCP). This mixture gave the solid rocket motors a specific impulse of 242 seconds (2.37 km/s) at sea level or 268 seconds (2.63 km/s) in a vacuum. Upon ignition, the motor burned the fuel at a nominal chamber pressure of 906.8 psi (6.252 MPa). Aluminum was chosen as a propellant due to high volumetric energy density, and its resilience to accidental ignition. Aluminum has a specific energy density of about 31.0 MJ/kg . The propellant had an 11-pointed star-shaped perforation in the forward motor segment and a double-truncated-cone perforation in each of the aft segments and aft closure. This configuration provided high thrust at ignition and then reduced the thrust by approximately a third 50 seconds after lift-off to avoid overstressing the vehicle during maximum dynamic pressure (max. Q).
== Function ==