Booster
A rocket stage, often a solid rocket motor or liquid-fueled first stage, that provides additional thrust at liftoff and early ascent.
Explanation
Boosters augment the core stage of a launch vehicle, typically providing 50-80% of total liftoff thrust. Solid rocket boosters (SRBs) are the most common type, used on vehicles like the Space Shuttle, Ariane 5, and SLS. Liquid boosters, like those on Falcon Heavy (three Falcon 9 first stages strapped together), can be throttled and recovered for reuse. Boosters are typically jettisoned two to three minutes after liftoff once their propellant is consumed or their thrust is no longer needed. The term is also used generically for any first stage, including reusable boosters that land and are refown. Booster performance determines a vehicle's payload capacity and is a key differentiator among heavy-lift and super-heavy-lift launch systems.
Why It Matters
Boosters provide the brute force needed to lift heavy payloads off the ground. The number, type, and recoverability of boosters define a launch vehicle's cost, capability, and reusability profile.
Concept Map
How Booster connects to other glossary terms:
Frequently Asked Questions
Are all boosters reusable?
No. Most boosters are expendable. SpaceX's Falcon 9 and Falcon Heavy first stages are currently the only reusable orbital-class boosters.
Why use solid boosters instead of liquid?
Solid boosters provide very high thrust for their size and are relatively simple. However, they cannot be throttled or shut down once ignited.
Sources
Last updated: July 1, 2026