Which motor has a higher total impulse?

The total impulse of a rocket motor is a measure of the total energy that the motor can provide during its burn, which is a product of its thrust and burn time. The motor classification system uses letters to indicate the impulse range of the motor, where each letter corresponds to a different range of total impulse, and higher letters denote higher impulse capacities.

In this scenario, the K motors indicate a higher total impulse than J motors. Specifically, a K motor has more impulse than a J motor. Among the options, both K185 and K550 are in the K class, thus indicating they have the potential for higher total impulse compared to the J135 and J415 motors.

When assessing K185 and K550, it is important to look at their specific specifications. K550 specifically has a higher total impulse than K185 due to its design and performance characteristics, contributing to its classification higher in terms of impulse range.

Therefore, the motor with the highest total impulse in the given choices is K550, which provides more total thrust over its burn time compared to the others.