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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Space Shuttle Solid Rocket Booster | 6/9 | https://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Booster | reference | science, encyclopedia | 2026-05-05T13:22:36.055022+00:00 | kb-cron |
The SRBs are jettisoned from the shuttle system at 2 minutes and an altitude of about 146,000 feet (45 km). After continuing to rise to about 220,000 feet (67 km), the SRBs begin to fall back to earth and once back in the denser 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 parachute), the frustum 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 15,704 ft (4,787 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 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 315,000 lb (143 t) and weighs approximately 1,200 lb (540 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 5,500 ft (1,700 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 (62 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 m) diameter, 20° conical ribbon parachutes have a design load of approximately 195,000 lb (88 t) and each weighs approximately 2,180 lb (990 kg). These parachutes are the largest that have ever been used, in both 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 m/s). The water impact range is approximately 130 nmi (240 km) off the eastern coast of Florida. 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 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 ships, the MV Freedom Star and the MV 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 drain the water from the motor case. 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.
== Challenger disaster ==