Tracking and Data Relay Satellites Spacelab Great Observatories (including Hubble ) Galileo , Magellan , Ulysses Mir Docking Module ISS components Boosters (Stage 0) - Solid Rocket Boosters No. boosters 2 Engines 1 solid Thrust 12.5 MN each, sea level liftoff (2,800,000 lbf ) Specific impulse 269 s Burn time 124 s Fuel