Definition: radiation hardened

Refers to electronic products used in space, satellite, nuclear plant and military applications. Radiation hardened devices are built to withstand cosmic rays and other natural electromagnetic radiation, as well as nuclear explosions. The effects of such radiation can be a temporary alteration or a slow degradation of the semiconductor elements in memory cells and transistors. If either a cell or transistor is induced to change its state, it can cause a program to crash (see abend). As the elements in a chip are made smaller, radiation has an increasingly greater and harmful influence.

"Rad hard" products are highly insulated from the outside world. In addition, devices may be built with redundant components at the system level or at the circuit level, and error-correcting memories can detect and correct a memory failure. See electromagnetic radiation.

A Wide Resistance Difference

This C-RAM phase change 4MB memory chip is shown without the cover and before the leads are cut. When the bit is 0, the memory cell resistance is 5,000 ohms, but 100,000 ohms when a 1. Due to the huge resistance difference between a 0 and 1, the chip is inherently radiation hardened (see phase change memory). (Image courtesy of BAE Systems.)