For rocket motors, how is 'burn time' generally defined?

Burn time for rocket motors is typically defined as the time from ignition until total burnout of the propellant. This means that burn time encompasses the entire period during which the rocket motor produces thrust, starting from the moment it is ignited and continuing until all of the fuel is consumed and thrust ceases.

While some definitions might emphasize the duration a motor can sustain thrust, to fully capture the concept of burn time, it is essential to include both the ignition phase and the total consumption of the propellant. Therefore, the correct answer accounts for both aspects: the duration of sustained thrust (the effective burn) and the complete lifecycle of the propellant from ignition to burnout, which is reflected in the correct response.

This comprehensive understanding of burn time is crucial for rocket design and performance analysis, as it impacts flight trajectory, altitude, and operational planning, making it a key focus in rocketry studies.