Having a comprehensive understanding of the issues involved in determining an appropriate size for the stockpile of
strategic nuclear weapons under a START III agreement is extremely important prior to its negotiation. Too high an estimate
will make a treaty difficult to obtain while too low an estimate could diminish U.S. strategic deterrence in the first half of the
21st century. The highly interdependent and time-varying relationship among the factors of initial stockpile size, rate of
weapon failures over time, weapons testing protocols, and the capacity of refurbishment facilities suggested the use of a
system dynamics simulation model to assist decision-makers in arriving at acceptable levels.

A computer model was developed using ithink system dynamics development environment. The model has been designed
to be easy to use in conducting "what if" exercises and ad hoc sensitivity analyses, while at the same time faithfully
modeling the essential elements of the process of weapon failure, testing and refurbishment. Taking advantage of the
multimedia user-interface features of ithink, a "learning environment" for the user has been created which begins with an
interactive tutorial on the essential issues involved in the process. It also allows the user to experiment by employing
different sets of estimates of input parameters - initial stockpile size, failure rates, refurbishment facility capacity, etc. - to see
the effect on weapons availability over periods of up to 30 years following treaty implementation.