About one decade ago, the Ballistic Missile Defense Organization (BMDO), then the Strategic Defense Initiative Organization, funded Silicon Designs to develop radiation-hardened accelerometers for kinetic energy vehicles to measure the change in velocity resulting from rocket motor firings that occur while changing trajectory. Smaller than a person’s thumbnail, these devices have very low power requirements and can operate over a wide temperature range and after being exposed to space radiation for long periods of time.
The accelerometer contains two major components: a micro-electro-mechanical systems (MEMS) sense element die or chip and an application-specific integrated circuit (ASIC). Sense elements, which detect acceleration, are fabricated on the surface of a wafer. Then the radiation-hard integrated circuits measure and digitize the acceleration detected by the sense element. Due to its small size, low cost, low power consumption, and ability to operate over a wide temperature range, the accelerometer is ideal for several applications in the automotive, heavy industry, and military areas.
These devices are currently used in the Patriot missile interceptors and for oil drilling applications (the same design features that make it radiation insensitive also allow it to work in the severe environments found at the bottom of a 10,000-foot oil well). In addition, through licensing agreements, the accelerometers have been modified for use as air bag sensors and are in about half the automobiles sold in the United States today. The miniature accelerometer forms the basis of a crash sensor that is superior to the mechanical devices found in previous air bag designs.