The propulsion designer is confronted with significant difficulties in selecting rocket motor parameters in applications where both cost and performance issues exist. While not a problem in principle, there is a formidable problem in practice because of the impracticality of conducting all of the necessary propulsion tradeoffs within the context of the entire system. The propulsion designer must therefore uncouple the rocket motor optimization from the system optimization by developing a measure of propulsion cost effectiveness and by treating major interface variables with constraining relations. The context for an analysis of this problem is a small-diameter free-flight artillery rocket system incorporating a solid-propellant rocket motor. Several low-cost rocket motor approaches are compared with a conventional design. While offering unit cost savings, these lowcost approaches involve performance and reproducibility penalties. Even with a single definitive costeffectiveness measure, it is shown that any of these designs may be regarded as optimum, depending on how the comparison is made (i.e., which constraints are imposed). Chamber pressure serves as an example of optimization of a continuous variable in the presence and absence of constraints. Again, system constraints are found to have a profound effect on optimization results.