Attaching solid rocket boosters to GPM’s launch vehicle, the HII-A No. 23. Solid-fuel rocket boosters (SRBs) are large solid propellant motors used to provide thrust in spacecraft launches from initial launch through the first ascent stage.

Many launch vehicles, including the Ariane 5, Atlas V, and the NASA Space Shuttle, have used SRBs to give launch vehicles much of the thrust required to place the vehicle into orbit. The NASA Space Shuttle used two Space Shuttle SRBs, which were the largest solid propellant motors ever built and the first designed for recovery and reuse.The propellant for each solid rocket motor on the Space Shuttle weighed approximately 500,000 kilograms.

Solid propellant boosters are not controllable and must generally burn until exhaustion after ignition, unlike liquid propellant or cold-gas propulsion systems. However, launch abort systems and range safety destruct systems can attempt to cut off propellant flow by using shaped charges. As of 1986 estimates for SRB failure rates have ranged from 1 in 1,000 to 1 in 100,000.SRB assemblies have failed suddenly and catastrophically. Nozzle blocking or deformation can lead to overpressure or a reduction in thrust, while defects in the booster’s casing or stage couplings can cause the assembly to break apart by increasing aerodynamic stresses. Additional failure modes include bore choking and combustion instability. Failure of an O-ring seal on the Space Shuttle Challenger’s right solid rocket booster led to its disintegration shortly after liftoff.
Solid rocket motors can present a handling risk on the ground, as a fully fueled booster carries a risk of accidental ignition. Such an accident occurred in the August 2003 Brazilian rocket explosion at the Brazilian Centro de Lançamento de Alcântara VLS rocket launch pad, killing 21 technicians. Liquid rocket boosters generally cannot be moved after preparation is completed.
Image Credit: Mitsubishi Heavy Industries