The recovery sequence
begins with the operation of the high-altitude baroswitch, which
triggers the functioning of the pyrotechnic nose cap thrusters.
This ejects the nose cap, which deploys the pilot parachute. This
occurs at 15,704 feet altitude 225 seconds after separation. The
11.5-foot-diameter conical ribbon pilot parachute provides the
force to pull the lanyard activating the zero-second cutter, which
cuts 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 12 95-foot suspension lines, the drogue
deployment bag is stripped away from the canopy, and the 54-foot-diameter
conical ribbon drogue parachute inflates to its initial reefed
condition. The drogue disreefs twice after specified time delays,
and it reorients/stabilizes the SRB for main chute deployment.
The drogue parachute can withstand a load of 270,000 pounds and
weighs approximately 1,200 pounds.
After the drogue chute
has stabilized the vehicle in a tailfirst attitude, the frustum
is separated from the forward skirt by a charge triggered by the
low-altitude baroswitch at an altitude of 5,975 feet 248 seconds
after separation. It is then pulled away from the SRB by the drogue
chute. The main chutes' suspension lines are pulled out from deployment
bags that remain in the frustum. At full extension of the lines,
which are 204 feet long, the three main chutes are pulled from
the 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, the main chutes' 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-foot-diameter, 20-degree
conical ribbon parachutes can withstand a load of 180,000 pounds
and weighs 2,180 pounds. The nozzle extension is severed by pyrotechnic
charge either at apogee or 20 seconds after low baroswitch operation.
Water impact occurs 295
seconds after separation at a velocity of 81 feet per second.
The water impact range is approximately 140 miles off the eastern
coast of Florida. Because the parachutes provide for a nozzlefirst
impact, air is trapped in the empty (burned out) motor casing,
causing the booster to float with the forward end approximately
30 feet out of the water.
The main chutes are released
from the SRB at impact using the parachute release nut ordnance
system. Residual loads in the main chutes deploy the parachute
attach fittings with the redundant flotation tethered to each
fitting. The drogue and frustum; each main chute, with its flotation;
and the SRB are buoyant. The SRB recovery aids are the radio beacon
and flashing lights, which become operable at frustum separation.
The radio transponder in each SRB has a range of 8.9 nautical
miles (10.35 statute miles), and the flashing light has a nighttime
range of 4.9 nautical miles (5.75 statute miles).
Various parameters of
SRB operation are monitored and displayed on the orbiter flight
deck control and display panel and are transmitted to ground telemetry.
The prime contractor
for the SRB motors is Morton Thiokol Corporation, Wasatch Division,
Brigham City, Utah. United Space Booster Inc. Booster Production
Company is prime contractor for SRB assembly, checkout and refurbishment
for all non-solid-rocket-motor components and for SRB integration.
Companies supplying various components for the SRBs are Pioneer
Parachute Co., Manchester, Conn. (parachutes); Abex Corp., Oxnard,
Calif. (hydraulic pumps); Arde Inc., Mahwah, N.J. (hydrazine fuel
modules); Arkwin Industries Inc., Westbury, N.Y. (hydraulic reservoirs);
Aydin Vector Division, Newtown, Pa. (integrated electronic assemblies);
Bendix Corp., Teterboro, N.J. (integrated electronic assemblies);
Consolidated Controls Corp., El Segundo, Calif. (fuel isolation
valves, hydrazine); Eldec Corp., Lynnwood, Wash. (integrated electronic
assemblies); Explosive Technology, Fairfield, Calif. (CDF manifolds);
Martin Marietta, Denver, Colo. (pyro initiator controllers); Moog
Inc., East Aurora, N.Y. (servoactuators); Sperry Rand Flight Systems,
Phoenix, Ariz. (multiplexers / demultiplexers); Teledyne, Lewisburg,
Tenn. (location aid transmitters); United Technology Corp., Sunnyvale,
Calif. (separation motors); Sundstrand, Rockford, Ill. (auxiliary
power units); Motorola Inc., Scottsdale, Ariz. (range safety receivers).