A Nonlinear Dynamical Model of the Impact of SDI on the Arms Race

We present numerical results from a nonlinear dynamical model with discrete time that simulates the implications of ballistic missile defense systems (SDI) on the arms race between the two superpowers. As dynamical variables we introduce the number of intercontinental ballistic missiles (ICBMs), antiballistic missile systems (ABMs) and anti-ABM systems such as antisatellite weapons (ASAT) of each of the two sides. The time evolution of these systems (arms race) is simulated numerically under various parameter assumptions (scenarios). The a priori unpredictability of human decisions is simulated through random fluctuations of the buildup parameters. The results of our idealized model indicate that for most parameter combinations, the introduction of SDI systems leads to an extension of the offensive arms race rather than a transition to a defense-dominated strategic configuration. A reduction in the number of offensive weapons, that is, an approach to a defense-dominated strategy, was observed if either the number of reentry vehicles per ICBM (MIRV) is limited to much smaller values than presently realized or if the accuracy of offensive weapons is significantly reduced. For the case of a strongly accelerated arms buildup (either offensive or defensive), we observe a loss of stability of the solutions that we interpret as a transition to unpredictable chaos. We also incorporate a discussion of economic and risk parameters, both of which also tend to increase with the introduction of SDI systems.