         SOLID ROCKET BOOSTERS
              Prior to launch, the entire weight of the Space  Shuttle is
         supported on the launch pad by two solid rocket boosters.  Each
         booster is attached to the pad by four large bolts.
              The heart of each booster is the motor, the largest solid
         rocket ever to be flown and the first designed for reuse.  It is
         made of four factory prepared segments filled with propellant at
         the manufacturer's facility and assembled at the launch site.
         The segmented design permits ease of fabrication, transportation
         and handling.
              The motor segments are loaded in pairs from one batch of
         propellant ingredients to minimize any thrust imbalances between
         boosters used for a single Shuttle flight.  Propellant loading is
         also done in such a manner as to cause a reduction in thrust 55
         seconds into the Shuttle flight to prevent overstressing the
         Shuttle vehicle during its critical phase of flight, the period
         of maximum dynamic pressure.  Each booster develops over
         11.8 million Newtons (2.65 million pounds) of thrust.
              The exhaust nozzle in the aft segment of each motor, in
         conjunction with the orbiter main engines, steers the Shuttle
         during flight.  It can be moved up to eight degrees by the booster
         thrust vector control system which is controlled by the orbiter
         guidance and control computer.
              At burnout the two solid rocket boosters are separated from
         the external tank by pyrotechnic (explosive) devices and moved
         away from the Shuttle vehicle by eight separation motors -- four
         housed in the forward compartment and four mounted on the aft
         skirt.  The separation motors are fired by a command from the
         orbiter.  
              The recovery system, in the forward section of the booster,
         consists of parachutes and a homing  device.  Following separation
         -- at about 5.8 kilometers (19,000 feet) -- the booster is slowed
         by a drogue parachute and finally by three main parachutes to
         impact water at a speed of about 25 meters/second (85 feet/sec),
         aft end first.  By entering the water this way, the air in the
         empty booster is trapped and compressed, causing the booster to
         float with the forward end out of the water.  After divers insert
         a nozzle closure and force the  water from the booster using air
         pumps, the booster is towed to shore.
              After recovery, the booster is disassembled and refurbished.
         The motor segments are shipped to the manufacturer for reloading
         for another Shuttle flight.  The other systems are refurbished
         either at the launch site or at the respective manufacturers'
         locations.
         
         Solid Rocket Booster
              Length      45.5 meters (149.1 feet)
              Diameter     3.7 meters (12.2 feet)
         
---
  Via FTL BBS (404-292-8761) and NASA Spacelink (205-895-0028)
