Physics lab aims to hit the target

A John Hopkins Applied Physics Laboratory (APL) team is developing a small device to measure the spin rates and orientation of flying artillery projectiles. The research may reduce the need for expensive and expansive weapon tests and evaluation methods.

APL’s Research and Technology Development Centre (RTDC) is working with the US Army Research Laboratory at Aberdeen Proving Ground on a scaled-down version of APL’s patented xylophone bar magnetometer.

Tucked onto a penny-sized chip in the back of a projectile, the sensor would measure the vector components in the Earth’s magnetic field over time and give researchers instant information on the shell’s behaviour as it flies downrange.

Among other methods, the Army currently gathers this data by firing projectiles down long, specially designed ranges, tracking them with high-speed video or X-ray photos and analysing the footage.

The APL team believe that a magnetometer small enough to put in the projectile itself would negate expensive evaluation techniques as the projectile could be fired under normal conditions, and know right away if the projectile is doing what it’s supposed to do.

The Laboratory’s team on this Defence Advanced Research Projects Agency (DARPA) funded project previously developed the xylophone bar magnetometer.

Based on a classic resonating xylophone bar, the device consists of four nodes that feed an alternating electrical current through a conductive metal bar. The current, set to the same frequency as the bar’s own mechanical resonance, causes the bar to vibrate in the presence of a magnetic field.

Small, lightweight, and requiring little power, the magnetometer scaled down using polysilicon materials and micro-electromechanical systems fabrication techniques.

The next stage includes integrating the miniature measuring device with electronics on the chip, and making it compatible with batteries, transmitters, and other components designed to fit in a projectile’s tracer well.

The microscopic magnetometer is said to be an early step on the path to ‘smarter weapons’ such as hi-tech bullets loaded with computer chips that give fast and accurate data on speed, location, and progress toward a target.