Submarine detection

Australian scientists have developed a new way to locate and identify even the ’quietest’ of today’s submarines.

The Australian development, called MAGSAFE, uses the detection of changing magnetic fields to identify and monitor a moving submarine. The method, which is unique in that it captures 12 magnetic field-related data values per reading as opposed to the single number measured by a conventional magnetic anomaly detector (MAD) magnetometer, arises from research into new minerals exploration technologies that detect magnetic fields.

A major project at CSIROIndustrial Physics, which includes a contract with the Defence Science and Technology Organisation’s (DSTO) Capability Technology Demonstrator program, is now applying this development to naval defence.

“It is technology that has the potential to assist with improved security for Australia,” says CSIRO researcher Dr Cathy Foley, who heads up the CSIRO team behind the project. “It will enable a submarine’s depth, bearing and orientation to be tracked.”

The technology is basically a ’tensor gradiometer’, which is a device that can measure minute changes in magnetic field gradients. It uses three independent rotating sensors, which use high-temperature superconducting quantum interference devices (SQUIDs) to monitor the magnetic field gradient.

In theory, the system means that pilots whose aircraft are fitted with MAGSAFE detectors will be able to measure the range, depth and bearing of a submarine, how fast it is going and if it is diving – all from one flyby.

MAGSAFE will also have an inherently higher sensitivity and immunity to external noise compared to conventional MAD systems, which means it will be especially effective when tracking a modern ’ultra-quiet’ submarine.

Over shallow or deep oceans, traditional MAD systems also detect magnetic fields caused by ocean swell or geographical conditions, which makes the detection of a specific target quite difficult. New MAGSAFE algorithms and data processing will extinguish these noise sources.

While still a MAD system, MAGSAFE is built on a new gradiometer sensor and a novel method of rotating three such sensors to monitor the differences in magnetic field gradients. This difference is monitored in a superconducting flux transformer fabricated onto flexible tape, folded into a U-shape to form opposing sensing loops with a central monitoring loop coupled to the SQUID device.

The opposing loops in the flux transformer have the effect of rejecting the otherwise overwhelming common-mode signal of the earth’s magnetic field, and the rotation removes the need for the exacting engineering tolerances which have until now limited the effectiveness of fixed gradiometers.

Dr Foley says the theoretical predictions are revolutionary and have created considerable industry excitement. “Detection of magnetic fields is the key for many industries, including defence, mineral exploration, food industries and correctional facilities,” she says.

The technology grew from a joint project with CSIRO Exploration and Mining in 2000, which sought to develop a new magnetic gradiometer for mineral exploration.

“With a consortium of Australian mining companies – BHP Billiton, WMC Resources, Newmont, MIM Exploration (now Xstrata) and De Beers – we were able to demonstrate the value of our new measurements,” says Dr Foley. “By using the rotating gradiometer concept, commodity companies could significantly improve their detection of minerals and oil to prevent false drilling, saving $10 million for every false drilling for oil, for example.”

Dr Foley says there is a long history of geophysics and defence-based technologies being transferred between each industry. “When completed, MAGSAFE will provide a new measurement capability that will benefit industry, the economy and Australia’s security. However, it also has other applications. It could, for example, easily detect stainless steel objects such as hypodermic needles that are difficult to detect using traditional methods.”

The CSIRO teams are now completing their current three-year project with the DSTO to get MAGSAFE operating and performing in real-world situations.