Description of a model designed to help decisionmakers more realistically appraise the scheduling implications of alternative weapon system programs. Most widely used models for program planning and scheduling do not take into account the problem of resource availability, although many important resources are limited and constrain the scheduling of activities that require them. SPARTAN, a computer model programmed in FORTRAN IV, is specially designed to address the problem of evaluating alternative weapon system proposals given limited resources. Heuristics or scheduling rules modify the basic computer program to increase the utilization of available resources or shorten the length of the schedule. Results from a test case indicate that a resource-constrained model can yield more realistic costs and completion dates, as well as different choices among development strategies, than a model that assumes unlimited resources. 103 pp. Ref.