Predicting Combined Neutron Degradation and Gamma Induced Effects on a Closed Loop System

This paper demonstrates a technique for modeling open loop or closed loop systems in either functional block representation and/or multiple circuit configurations utilizing actual piece-parts data. Computer programs have been developed to represent systems as functional blocks or transfer functions. The SECURE program incorporates a multiplicity of detailed circuits and transfer functions which provides a more complete prediction of system response based on piece-part models; e. g., Ebers and Moll. The program and piece-part models contain the capability of simulating and therefore predicting system response to an ionizing and displacement radiation. Comparison between SECURE results and a linear controls system analysis program demonstrates the close agreement between simulation results. By the use of superposition the simulation was extended to include the radiation effects of an operational amplifier. The response of the amplifier had been predicted using the TRAC computer code (Ref 1). The radiation response of a closed loop system is compared with results obtained when detailed circuitry is simulated by use of the SECURE program. The system used as an illustrative example is a closed loop single axis inertial platform (Ref 2). As a part of the prediction, the SECURE code is used as a design aid in selecting circuit configurations and modifying circuit design.