Posted on 01/16/2017 12:22:48 PM PST by doug from upland
Tiny gravity sensor could detect drug tunnels, mineral deposits
By Sid PerkinsMar. 30, 2016 , 1:00 PM
A new device the size of a postage stamp can detect 1-part-per-billion changes in Earth’s gravitational field—equivalent to what the gizmo would experience if it were lifted a mere 3 millimeters. The technology may become so cheap and portable it could one day be mounted on drones to spot everything from hidden drug tunnels to valuable mineral deposits.
Gravity’s force is nearly the same everywhere on Earth. But there can be minute fluctuations, based on the density of the rock or other material below. Distance from Earth’s core, which varies according to altitude, also affects the magnitude of our planet’s gravitational attraction.
Most devices that measure these gravitational differences, called gravimeters, are based on two principles: They either measure the time it takes an object to fall a certain distance, or they measure the distance that a certain weight stretches a spring. (The stronger the force of gravity, the faster an object will fall, and the farther it will stretch a mass hanging by a spring.) In either case, state-of-the-art gravimeters cost more than $100,000 and are the size and weight of a car battery or larger—all of which severely limits their uses, says Giles Hammond, a physicist at the University of Glasgow in the United Kingdom. Although portable, current devices—some of which weigh as much as 150 kilograms—can’t easily fit in many places scientists would like to use them or be readily carried to remote locations or mounted on small drones. Sign up for our daily newsletter
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So Hammond and his colleagues set out to build a smaller, cheaper spring-based gravimeter. The heart of their device is a postage stamp–sized bit of silicon; it’s carved so that in its center there’s a 25-milligram bit of material left suspended by three stiff, fiberlike structures that are each about 5 micrometers across (less than one-third the diameter of the finest human hair). Together, these act as the spring. As the gravitational field surrounding the device changes—such as it would if it passed over a large underground cavern or a dense deposit of minerals, because of the sudden change of density in the underlying rocks—the tiny bit of silicon bobs up and down in response to that change, Hammond says. Those movements are tracked by monitoring the silicon’s shadow as it moves across a light detector.
The team’s gravimeter is so sensitive it can track the up-and-down motions of Earth’s surface caused by the changing positions of the sun and moon, the researchers report online today in Nature. (These so-called “Earth tides” occur and are measurable, but they are much smaller than those seen in the seas because rock is stiffer than water.)
For now, Hammond’s team has proven the device’s worth in the lab. Doing so in the field will be challenging, says Hazel Rymer, a volcanologist at the Open University in Milton Keynes, U.K. But if successful, the availability of gravimeters that are cheaper and much more portable than today’s equipment “will be a game-changer,” she notes. Researchers could deploy networks of the tiny gravimeters to monitor the movements of magma within and underneath volcanoes, possibly discerning the magnitudes and patterns of flows in advance of an eruption, for example. Or they could mount them on drones and use them to search for underground voids that could eventually evolve into sinkholes, or for humanmade structures such as tunnels used to smuggle drugs.
They could also help prospect for mineral deposits that are denser than the surrounding rock, thus affecting the local gravitational field, says Tim Niebauer, a physicist and president of Micro-g LaCoste, a Lafayette, Colorado–based company that manufactures a variety of gravimeters. Or, he notes, a string of the devices—especially ones that had parts-per-billion accuracy and could withstand high temperatures and pressures—could be fed down a borehole to monitor widespread changes in the amount of water in an aquifer or petroleum in a surrounding oilfield, possibly yielding information about how quickly such reservoirs might run dry. Those sorts of data can be gathered at Earth’s surface now, he adds, but “the closer you are to the reservoir, the better the measurements can be.”
Many of the potential applications for such devices “have been science fiction for so long,” Rymer says. “We’ve just been waiting for the technology to catch up with our ideas.”
good idea
I want one in my phone. How cool would that be.
gravimetric navigation is used by the Navy on submarines, it’s accuracy and the gravity vector maps are all highly classified but yes it not only is possible it is used on a regular basis presently by our boomer subs.
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I learned something new. Thanks.
Mineral deposits??? Paging Todd from Gold Rush - that poor SOB needs all the help he can get.
Depends on who owns the mineral rights to stuff under your property.
In many states, the surface property owner is not the same as the subsurface mineral owner..................
I hope the EPA doesn't get wind of the plan, they hate it when people get clever without checking with them first so they can kill it.
Submarine navigation is a very complex problem, mostly you are trying to buy down the errors that inevitably accumulate over time in your primary inertial navigation sensors by periodically getting an occasional position fix from some alternative known source that doesn’t force you to surface. Gravity maps plays a role in getting that fix (one method, there are others) and not, to my knowledge, in the primary navigation function itself. But I’ve been known to be wrong.
The border between Gaza and Egypt is 14 Kilometers long. The tunnels have been found as deep as 20 meters or 65’.
Time to dig a trench from the Mediterranean to the Red Sea..............Kinda like Exodus in reverse...............
Every golf course groundskeeper will want one.
So they know where to place the dynamite.
They could have used one of these in Vietnam.
I know, I was just making a joke.
The elevation needs to be known within a hundredth of a foot as well. And how do you get the data out of the device? I'm sure in the lab they have it wired up to a laptop or something. I suppose they have miniature data sending modules though as well - like bluetooth? I could see where you could “seed” the border with these chips, and see how their readings CHANGE over time.
They would also detect vibrations from foot and vehicle traffic as well if they are sensitive enough. Or - have them combined with a miniature seismic sensor.
I've read where they have, or are developing, sensors for storm watching that measure air pressure, wind speed and velocity and temperature and then relay that to the ground. The sensors are the size of a grain of rice! An airplane drops a bunch of them into the storm cell and away they go.
The only thing with the seismic or the GPR is that you would need to keep doing the surveys to detect new tunnels. That would be the nice thing about a bunch of static sensors. Maybe just focus on vibration sensors that could also maybe pick up on tunnelling activities.
The only thing with the seismic or the GPR is that you would need to keep doing the surveys to detect new tunnels. That would be the nice thing about a bunch of static sensors. Maybe just focus on vibration sensors that could also maybe pick up on tunnelling activities.
Maybe I’m missing something. If it is sensitive enough to gegister being raised 3mm (1/8”), how does one usefully compare various geolocations, unless sensor height is minutely/absolutely accounted for? How can readings in an airplane he compensated?
ping for later
I know a guy who has small lake on his property next to the house. He drained the lake and ran heat pump hose under the lake bed.
Cool in the summer, warm in the winter.
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