Which type of burn motor is considered safest for a rocket that is marginally capable of flight?

The safest type of motor for a rocket that is marginally capable of flight is a regressive burn motor. This type of motor is characterized by a decreasing thrust profile as it burns, meaning that the thrust diminishes over time rather than stabilizing or increasing.

The reason a regressive burn motor is considered safer for rockets that may have structural integrity or stability concerns is that the gradual reduction in thrust decreases the forces acting on the rocket as it ascends. Such a thrust profile allows for better control and mitigates the risk of flight instability, which can be particularly important for rockets in the marginal flight category.

In contrast, other motor types either maintain a steady thrust (like controlled burn motors) or increase thrust (such as linear and progressive burn motors), which could exacerbate any flaws in a marginally capable rocket’s design, potentially leading to loss of control or failure during ascent.