Liquid rocket booster

Same as a solid rocket booster, but uses liquid instead of solid fuel

A liquid rocket booster (LRB) uses liquid fuel and oxidizer to give a liquid-propellant or hybrid rocket an extra boost at take-off, and/or increase the total payload that can be carried. It is attached to the side of a rocket. Unlike solid rocket boosters, LRBs can be throttled down if the engines are designed to allow it, and can be shut down safely in an emergency for additional escape options in human spaceflight.

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