Space MIAD Practice Test 2025 - Free Space MIAD Practice Questions and Study Guide

Solid propellant is characterized by its inability to be stopped or restarted once ignited, which is a significant disadvantage in many applications. This limitation arises from the nature of solid propellants, which burn continuously until the fuel is depleted. This lack of throttling and restart capability makes it challenging to adjust the thrust levels during flight or to safely abort a mission.

In comparison, the other options describe positive traits or features of different propulsion systems. For example, the ability to throttle and restart is often associated with liquid propellant systems, allowing for more control during flight. A simple design is typically viewed as an advantage, making solid propellant systems easier to manufacture and handle. Very high thrust is a noteworthy characteristic of solid propellants, yet without the ability to control or modify thrust once engaged, the operational flexibility is limited. This illustrates why the inability to stop or restart is a core disadvantage of solid propellant systems.