Why is the thrust curve of a Bates grain considered neutral?

The thrust curve of a Bates grain is considered neutral primarily because it does not create significant thrust variations over time. A neutral thrust curve means that the thrust produced remains relatively constant throughout the burn, which can lead to predictable performance and stability during flight. This stability is beneficial in rocketry, as it allows for easier calculations of expected flight behavior and ensures a more reliable rocket launch.

In contrast, other types of thrust curves may exhibit more pronounced variations or fluctuations. For instance, curves that produce a smooth, continuous thrust can still vary in magnitude over specific intervals, while those that vary greatly based on temperature can hinder performance by introducing unpredictability in thrust based on changing conditions. Furthermore, fluctuations that impair performance may lead to instability, reduced altitude achieved, or even failure in maintaining controlled flight. Hence, the characteristics of the Bates grain's thrust curve contribute significantly to its classification as neutral in terms of thrust variability.