quantum gravity gradiometer
 

Another question being can it detect submarines subsurface?


https://www.thetimes.co.uk/article/b...sics-9qs9stx78

British team heralded after ‘Edison moment’ breakthrough in quantum physics

A British breakthrough in the use of quantum physics to map the subterranean world has been heralded as an “Edison moment”.

Researchers from the University of Birmingham revealed today that they had won a global race to develop a device known as a quantum gravity gradiometer, which can map underground features with unprecedented speed and accuracy.….

The project has been funded by the Ministry of Defence, which is interested in using the technology, which detects minute differences in the Earth’s gravitational field, as a navigational tool.

Professor Kai Bongs of the University of Birmingham, said: “This is an ‘Edison moment’ in sensing. With this breakthrough we have the potential to end reliance on poor records and luck as we explore, build and repair…..

Until now, quantum gravity gradiometers had worked only in controlled laboratory conditions. The device described today in the journal Nature is the first to work in the real world, and was tested by detecting a tunnel under the streets of Birmingham…..

It is roughly the size of a washing machine and can create maps with a spatial resolution of about 50cm. Dr Michael Holynski, senior author of the study, said that a smaller version is being developed. “We have a device that is 15kg and can fit in a backpack,” he said. The aim is to make one about as small as a Coca-Cola can.

“It’s going to happen over the next ten years or so, that’s what we believe,” he added. “Gravity is the best way of looking deep into the soil. If you want to look past the first couple of metres, it’s got to be gravity.”

Dr Gareth Brown, of the Defence Science and Technology Laboratory, an agency of the Ministry of Defence, said: “For national defence and security, accurate and rapid measurements of variations in microgravity open up new opportunities to detect the otherwise undetectable and navigate more safely in challenging environments.

“As gravity-sensing technology matures, applications for underwater navigation and revealing the subterranean will become possible.”


https://idstch.com/technology/quantu...ine-detection/

Interesting comment about also being used to detect stealth aircraft…

As if MoD would be thinking such a thing! Is there no limit to the cynicism displayed in this forum???

Indeed. A submariner’s greatest fear. A transparent ocean. Long discussed and debated - potentially game changing.

It would make the submarine obsolete overnight.

Good thing if you think about it (unless you are a submariner) it will be the same for all. So can
save the expenditure for a submarine fleet and either use it for other defence systems or just to reduce the defence budget.

Hmm airborne gradiometers have been used in oil & mineral surveying for years - and they're not easy to operate or interpret

there is so much "noise" in the method - very good at seeing features several kms across and at similar depths - not so good for features a couple of hundred m across and near surface

And the computation back at base (NOT in real time) is fearsome

Yes, Asturias; but these babies are quantum. Not your usual atoms floating about.

Quantum entanglement getting in everywhere. Just do a search on Chinese quantum radar….

e.g.
https://interestingengineering.com/c...t-stealth-jets

"aYes, Asturias; but these babies are quantum. Not your usual atoms floating about"

which presumably will justify a VAST price

Problem isn't the atoms - it's the effects you're trying to measure

gravity is Gravity and the differences are miniscule - the "noise" - position, acceleration (s), height are serious issues - and of course the difference in the gravity field from 10,000 tons of SSBN cp 10,000 tons of seawater measured over a kilometre or so away is vanishingly small

But hey , ho - there will be lots of BIG contracts and a lot of science done - just don't expect it to work very well......... or very soon.........

and there's me thinking we were still trying to have a quantum theory of gravity ...... must have missed the announcement of a Grand Unified Theory. Shame on me.

Asturias56,

Indeed, very small differences - but we are getting very good at measuring very small differences - be they at astronomical or quantum levels - especially for gravity…

https://newatlas.com/physics/gravity...ne-millimeter/

I’m with Asturias on this one. I’ve been involved with gravity surveys, including airborne ones.

The main problem is extracting the signal from the noise. If you wish to acquire precision gravity data, the first thing you do is keep the gravimeter stationary.

For a typical oil exploration gravity survey, you are looking for a precision of about one milligal. This is roughly 1 millionth of a G!

If you are bouncing the gravimeter around in an aircraft, even on a relatively calm day, the processing required is extremely difficult and one of the things you sacrifice is the ability to detect small scale features.

In the case of a survey I was involved with, we were able to locate the margins of a buried sedimentary basin that was tens of kilometres across. We were not expecting to be able to find oil-bearing structures.

I haven’t done any calculations, but I suspect that the gravity signal from a submarine, even near the surface, would be buried in the noise, regardless of the sophistication of the measuring equipment.

If the s/m displaces water equal to its mass - would it even have a gravity signature?

It'll have a different mass distribution, so it will definitely have some sort of signature (whether or not it's measurable is another question). Presumably, if you were designing a new submarine from scratch, you could then try to make the mass distribution more even.

If the sensor struggles in an airborne environment, what about deploying it like a sonobuoy? Either to float, or maybe to sink slowly thorugh the water reeling out a wire to a floating antenna?

Ninthace,

There would be gravity signature, or anomaly as we say in the trade. ;)

For modeling purposes and ignoring the ballast tanks, think of the pressure hull as a steel cylinder full of air. It will have a different bulk density than the surrounding water.

PS I’ve just done some calculations, based on an Ohio-sized cylinder and I calculate a density of 2.3 gm/cc. More than I expected. I guess reactors and missiles are heavy!

Given the ballast tanks are either side of the hull, can you ignore them? It is going to a long thin anomaly. Most of what follk see as submarine is casing, the actual boat is quite a bit smaller. Things have obviously moved on since I tried to measure G. :8

It's quantum. The atoms can be in two or more places at once. You'll need Brian Cox to explain that one; I just take his word for it.

I was ignoring them as a first-order approximation and assuming they were full of water.

…..or Erwin Schrödinger

If that is correct, the boat needs to be getting a lot of offsetting lift from somewhere. I'd thought the idea was to trim them for neutral buoyancy. Is that not so?

You also have to remember sampling - an Ohio is approx 170m x13m x 1m

To get an "anomaly " you're going to need 2 or three "anomalous values minimum - so that's approx one every 50m if you are lucky enough to be running parallel with the boat and every 3m across track

At 180 mph (80 mps) you have to get a value every 0.5 sec or 0.04 secs depending on relative heading. Worse at jet speeds of course.

Then you have to locate that anomaly in a bucket load of data (after several hours of ongoing data collection) with all the issues of "noise" mentioned above in real time.

I42 will correctly point out that the Ohio anomaly would be bigger than the actual vessel - but that just spreads it out across a little bit more ocean , with the edges almost impossible to define. Every grav survey I've seen is pretty good at defining things down to 3-10 kms resolution - after that you're kidding yourself.