What pair of large rockets flanked the Space Shuttle external tank at launch?

Solid rocket boosters flanked the Space Shuttle’s external tank at launch.

The Shuttle stack had three major elements: the winged orbiter, the large orange external tank, and two white solid rocket boosters attached on opposite sides of the tank. The boosters supplied powerful thrust during the first part of ascent, when the fully fueled vehicle was heaviest.

Unlike the orbiter’s liquid-fueled main engines, the boosters used solid propellant. They ignited at liftoff and operated for roughly two minutes before separating from the external tank. Parachutes then helped guide them into the ocean, where they were recovered, refurbished, and prepared for later missions.

The boosters were not “fuel tanks” or auxiliary engines hidden inside the orbiter. Each was a complete reusable solid rocket motor assembly with its own casing, nozzle, avionics, separation hardware, and recovery equipment. Their distinctive side-by-side placement made them one of the Shuttle’s most recognizable features.