Solid Rocket Boosters (SRBs)

Introduction

Solid Rocket Booster (SRB): A solid propellant motor used in spacecraft launches to provide thrust from initial launch through first ascent.
Used by launch vehicles such as Atlas V, SLS, and Space Shuttle for providing the majority of thrust needed to reach orbit.

Size and Design:
- Space Shuttle used the largest SRBs ever built until the SLS.
- SRBs were the first designed for recovery and reuse.
- Each Space Shuttle SRB motor weighed about 500,000 kg.
Comparison with Liquid Propellant Rockets:
- SRBs provide large thrust with simple design.
- They do not require significant refrigeration and insulation.
- SRBs are cheaper to design, test, and produce than liquid propellant boosters.
- They allow for staging, reducing the need for liquid propellant and lowering launch mass.
Performance Examples:
- Ariane 4 rocket with no boosters: 2,175 kg payload.
- Ariane 44P with 4 boosters: 3,465 kg payload.

Ignition and Burn:
- SRBs are not controllable once ignited and must burn until exhaustion.
- Launch abort and range safety systems can attempt to cut propellant flow with shaped charges.
Failure Risks:
- Failure rates for SRBs have varied; known for sudden, catastrophic failures.
- Issues like nozzle blocking, casing defects, bore choking, and combustion instability can cause failures.
- Notable failure: Challenger disaster due to O-ring seal failure.
Handling Risks:
- Fully fueled SRBs pose risks of accidental ignition.
- Example: 2003 Brazilian rocket explosion killing 21 technicians.

Fixed Number of Boosters:
- Space Launch System, Space Shuttle, Ariane 5, LVM3
Variable Number of Boosters:
- Atlas V, Delta II, Delta IV Medium, PSLV, Ariane 6, Vulcan Centaur

Various historical and technical references are available, including NASA documents and archived resources.