What are the minimum components that make up a propulsion system?

• A. Thrust chamber and nozzle
• B. Fuel and oxidizer
• C. Guidance electronics
• D. Rocket motor and an igniter

Answer: (D)

A propulsion system must have two essential parts: a means to burn propellant and a way to start that burn. The rocket motor provides the combustion chamber, contains the propellant, and converts chemical energy into high-speed exhaust, which creates thrust. An igniter supplies the initial energy to ignite the propellant so the burn begins. The nozzle and thrust chamber are part of the motor, but they don’t generate thrust by themselves without ignition. Propellants (fuel and oxidizer) are what get burned, but you still need a motor to contain and ignite them. Guidance electronics handle control, not propulsion generation. So, the simplest, functional propulsion system is a rocket motor paired with an igniter.