SBIR-STTR Award

Fault tolerance in a real-time computing environment is a critical need for the terminal guidance computer in interceptors in Ground-based Midcourse Defense (GMD). In much of the GMD system, fault detection, correction and/or compensation can be done entirely in software. But in the case of faults introduced into the guidance computer by radiation, a combined hardware and software approach can be very useful. Specifically, high dose rates can cause logic upset, but can also cause latchup in integrated circuits. The former can be handled by EDAC, or in extreme cases, by a rollback to data stored in non-volatile memory, and re-starting from this earlier point. But if latchup occurs, power to the computer must be toggled off, then restored. This can take much longer that EDAC or rollback. In the short mission duration of an interceptor, this time may not be available. If latchup-immune chips can be employed, coping with high dose rates is greatly simplified, since power doesn't need to be dumped. The proposed program applies to the high dose rate threat a technique developed for suppressing latchup caused by heavy ions in space. Success in this effort will significantly simplify the job of developing a fault tolerant real-time computing environment for GMD

Missile Defense Kinetic Kill Vehicle (MD-KKV) systems are required to operate in a fault tolerant manner even though exposed to the highly-stressing effects of nuclear-weapon detonations and the natural space radiation environments (which can be very harsh at northern latitudes during intense solar storms). Additionally, MD-KKV systems often are designed using commercial-grade/commercial-off-the-shelf (COTS) parts in order to utilize the highest performance parts available. Satisfying all requirements simultaneously is a non-trivial challenge, since many COTS parts are susceptible to radiation-induced latchup. When a part suffers latchup, it may be permanently damaged, or it may be placed in a high dissipation, non-functional state from which it can only recover by by toggling power off, then on again. In either case, the system controller reacts to the radiation pulse by initiating the power-cycle routine. Since time is critical in terminal guidance, any such interruption could be mission-ending. Clearly, then, the use of latchup-susceptible parts types is high risk for a fault-tolerant system. Full Circle Research, Inc. and Raytheon Missile Systems are collaborating to develop the latchup-mitigation process proposed herein,which, once qualified, would potentially make a large number of otherwise unusable or high-risk latchup-susceptible COTS part types usable and low-risk in nuclear-hardened MDA assets, particularly missile-defense interceptors.

Keywords:
Latchup, Cots, Radiation Induced Latchup, Nuclear