The primary difference between a rocket motor and a rocket engine lies in the type of propellant they use: a rocket engine uses liquid propellant, while a rocket motor uses solid propellant.
Essentially, the distinction is based on the state of the propellant used for generating thrust:
-
Rocket Engine: Employs liquid propellant(s) which are pumped into a combustion chamber. Examples include engines using liquid oxygen (LOX) and kerosene (RP-1), or LOX and liquid hydrogen (LH2).
-
Rocket Motor: Utilizes solid propellant(s), typically a mixture of a fuel and an oxidizer, packed into a casing. Once ignited, the solid propellant burns from the inside out, producing thrust.
| Feature | Rocket Engine | Rocket Motor |
|---|---|---|
| Propellant Type | Liquid | Solid |
| Complexity | More complex, involving pumps, valves | Simpler design; fewer moving parts |
| Throttling | Generally capable of throttling | Typically not capable of throttling |
| Restarts | Restart capability is often possible | Usually cannot be restarted once lit |
| Performance | Generally higher specific impulse | Generally lower specific impulse |
Think of it this way: a rocket engine is like a car engine, where you're constantly feeding fuel (liquid propellant) into the combustion chamber. A rocket motor is more like a firework; you light it, and it burns until the solid propellant is exhausted. The reference definition is correct, so if one understands liquid vs solid fuel then that person understands rocket engines vs rocket motors.
