“Titanium Avocado” Could Provide GPS Quality Navigation Without Satellites

Sandia National Laboratories is developing an avocado-sized vacuum chamber made of titanium and sapphire that could one day use quantum mechanical sensors to provide GPS-grade navigation without the need for satellites.

In just a few decades, GPS has evolved from military technology to so many everyday applications that modern society now depends on it. However, GPS is not always available in places like high polar latitudes or in deep mountain valleys, and it can be scrambled or tampered with.

The vulnerability of GPS and similar systems lies in their dependence on constellations of satellites orbiting the Earth. These satellites emit time-stamped signals that are synchronized with atomic clocks. Using these signals, a GPS receiver in something as small as a wristwatch can use the Doppler effect on satellite signals as they pass overhead to establish an extremely precise position over the position. and the speed of the receiver. If these signals are interrupted or corrupted, the system fails.

An alternative is technology that was originally developed for military rockets during WWII and is commonly used on submarines when submerged to find their way. Called inertial guidance, this is a fully self-contained system that uses gyroscopes and accelerometers to calculate where the navigation device is relative to a known fixed position.

New Autonomous System Could Provide GPS Grade Navigation Patches

Sandia National Laboratories

It does this by measuring every rotation and movement of the device along the three axes. If these measurements are accurate enough, the results can rival those of GPS.

The problem is that, like GPS, inertial guidance systems have to be very precise and have the same atomic clock level of timing. This is possible with existing systems that use mechanical gyroscopes or lasers shining through clouds of rubidium gas to measure quantum effects, but these rely on heavy and expensive vacuum systems that remove all of the molecules from the gas. air likely to disturb the measurements.

The Sandia team’s approach is to take custom-built, rugged quantum sensors and place them in a chamber with a volume of just one cubic centimeter (0.06 cubic inch). This chamber is made of titanium with sapphire windows – materials that even prevent gases like helium from seeping in, unlike stainless steel and Pyrex glass.

The chamber can maintain a relatively hard vacuum for a long time, but instead of using complex and heavy pumps to produce that vacuum, the team fell back on an older electronic technology called getters. If you’ve ever looked at an old radio valve, you may have seen a silver or soot stain on the inside of the top of the tube. This is caused by a getter, which is a chemical plug formed around a filament. When a valve was manufactured, the vacuum inside was not strong enough, so a current was passed through the plug. This set off a chemical reaction that absorbed all of the stray air molecules.

In the case of the Sandia chamber, the getters are about the size of a pencil eraser and are placed in two narrow tubes that protrude from the chamber. It’s unclear how long the chamber will hold the vacuum, so the team aims to keep one sealed and operational for five years. In the meantime, researchers will focus on making the device less bulky and easier to manufacture.

The research was published in AVS Quantum Science.

Source: Sandia National Laboratories

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