Definition

Noun: A reaction engine is a type of engine that generates thrust by expelling a high-speed stream of matter rearward. This action produces an equal and opposite forward reaction, propelling the vehicle forward, based on Newton's third law of motion.

Usage

A reaction engine is the core mechanism for propulsion in the vacuum of space or within the atmosphere. It does not require an external medium to push against. - The spacecraft was powered by a sophisticated reaction engine. - Jet engines and rocket engines are both types of reaction engines.

Advanced Usage

• Principle of Operation: The term specifically refers to the engine's reliance on the reaction from expelled mass (the working fluid), distinguishing it from engines that push against an external surface like a propeller.
  • The efficiency of a reaction engine depends on the exhaust velocity of its propellant.

Variants and Related Words

• Reaction Propulsion (n): The method of propulsion achieved by a reaction engine.
  • Rockets are the only practical form of reaction propulsion for space travel.

Synonyms

• Jet engine (a specific, common type of reaction engine that uses atmospheric air).
• Rocket engine (a specific type of reaction engine that carries its own oxidizer).

Related Phrases

• Reaction motor: A less common synonym for reaction engine.
  • The early prototype used a simple reaction motor.

Noun

1. a jet or rocket engine based on a form of aerodynamic propulsion in which the vehicle emits a high-speed stream