Nuclear Survivability Concepts for Airborne Computers

This paper reviews design concepts for nuclear survivability of computers used in aircraft and spacecraft. Data is provided to relate dose rate and total dose tolerance. The vulnerability of available solid state devices is examined and limitations (failure modes) discussed in relation to overall system survivability. The approach is to avoid hardening 'overkill' and reduce cost. Two methods of hardening are considered: (1) microprogram or software circumvention for microprocessors containing ROM memory but suffering from transient logic upset, and (2) an instruction/program reload configuration for fast, low-cost random access reloading of a microprocessor containing RAM memories. It is pointed out that LSI semiconductors and microcomputers can be seriously affected by radiation levels which are lower than that required to incapacitate the crew or destroy vehicle structures from thermal or blast effects. Another consideration is the presence of RF energy known as electromagnetic pulse (EMP) that can damage or degrade semiconductors and produce logic upset. Methods of circumvention described in this paper have been implemented by laboratory model.