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Royal Navy says quantum navigation test a success

thequantuminsider.com

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Re: Royal Navy says quantum navigation test a success

#61

Post by jchallis »

themodelplumber wrote: post #19
jchallis wrote: post #13

This is the most obvious practical application of my PhD topic. A Bose Einstein Condensate is an extremely sensitive detector of gravity- a nuclear submarine could use it to make an ultra-accurate map of the world based on variations in the gravitational constant g. This would remove one of the primary reasons subs need to surface , in order to GPS lock. It’s a naval chart that would not require surfacing. A French p…

Fascinating. Q for you since you are so clued in. I am a ham radio operator and was thinking about novel forms of signal propagation. I landed on the idea of gravitons. Could gravitonic signal propagation be done somehow? While researching, I keep coming across familiar terms I know from radio land. Just curious if the fields here could be harnessed for communication. Thanks.

The big big downside of gravity waves is that they have no dipole radiators - with electric charge you have + and - and that allows very efficient propagation. For gravity there is only one charge ,and this allows only quadrupole radiation - making it extremely awful for transmission.

Re: Royal Navy says quantum navigation test a success

#62

Post by _joel »

themodelplumber wrote: post #19
jchallis wrote: post #13

This is the most obvious practical application of my PhD topic. A Bose Einstein Condensate is an extremely sensitive detector of gravity- a nuclear submarine could use it to make an ultra-accurate map of the world based on variations in the gravitational constant g. This would remove one of the primary reasons subs need to surface , in order to GPS lock. It’s a naval chart that would not require surfacing. A French p…

Fascinating. Q for you since you are so clued in. I am a ham radio operator and was thinking about novel forms of signal propagation. I landed on the idea of gravitons. Could gravitonic signal propagation be done somehow? While researching, I keep coming across familiar terms I know from radio land. Just curious if the fields here could be harnessed for communication. Thanks.

The detectors are such precision instruments it took over 10 years of calibration until they even had the first detection. Maybe some far off comms network could use them, but I doubt anytime soon. I wonder if you could use erasure codes with them too :)

Re: Royal Navy says quantum navigation test a success

#63

Post by jchallis »

snovv_crash wrote: post #39
jchallis wrote: post #13

This is the most obvious practical application of my PhD topic. A Bose Einstein Condensate is an extremely sensitive detector of gravity- a nuclear submarine could use it to make an ultra-accurate map of the world based on variations in the gravitational constant g. This would remove one of the primary reasons subs need to surface , in order to GPS lock. It’s a naval chart that would not require surfacing. A French p…

Isn't this the method used by the sub in Hunt for Red October? Or did they also use a gyroscopic and look for changes in the gravitational vector, not just its magnitude?

Red October used the usual gyroscopes approach that gets more and more inaccurate as it sails. I think a key plot point is that they need to surface to take a latitude / longitude , precipitating much suspense.

Re: Royal Navy says quantum navigation test a success

#64

Post by thinkingemote »

varjag wrote: post #52
julienfr112 wrote: post #44

Earlier quoted context omitted.

Is the gravity really constant ? I mean, big chunk of lava moving with different concentration of iron would make it change, wouldn't it?

Gravity is not magnetism, it does not care if it's iron or anything else.

There might be some confusion in these replies related to the gp's mixture of two terms. g = gravity of the earth which varies and the gravitational constant G which is a Constant and the same across the universe.

Re: Royal Navy says quantum navigation test a success

#65

Post by andromeduck »

WinstonSmith84 wrote: post #55
rz2k wrote: post #14

Earlier quoted context omitted.

That sounds absurd, but the $5 pressure sensor on my weather station could detect a volcanic explosion 5,000 miles away. Is there even a difference between a submarine and the surrounding water's gravitational fields when the sub has neutral buoyancy?

I'd argue that the gravity field of a sub is not uniform despite having neutral buoyancy. No idea though how significant that is vs. how sensible the measurement is

You'd have better luck trying to measure a neutron with a bathroom scale.

Re: Royal Navy says quantum navigation test a success

#66

Post by K0balt »

sakras wrote: post #38
kebman wrote: post #30

Earlier quoted context omitted.

You're probably surprised that you don't see it, because it's top secret. Here's an example of something you don't hear about: AI Assisted Battlefield Tactics. While I've never heard of it (certainly not in the press), I simply assume that they're doing research on it. I base this assumption on the AlphaStar AI from DeepMind that would completely pawn Grand Masters in the game of StarCraft 2. While AlphaStar is obvio…

AlphaStar hardly pawned GMs in any meaningful way. It mainly won on mechanics, even when Deepmind tried to nerf its mechanics. Probably the most important thing is that the “200 APM limit” is way higher than any human can do, because it made use of each one of its actions. Humans can reach 400+ APM by spamming, but their EPM will stay much lower than 200. The result is that it had god-tier micro that changed the game…

The word is pwned, not pawned, by the way. I suspect your autocorrect, as well as op’s has had it’s way with your prose.

I often wonder how much autocorrect will shape the evolution of language.

Re: Royal Navy says quantum navigation test a success

#67

Post by K0balt »

buildbot wrote: post #35
HyperSane wrote: post #27

Earlier quoted context omitted.

The US military is working on a device that can use stars to determine location even during the day.

Couldn’t that be just celestial navigation with a very specific notch filter for starlight wavelengths? So you can see stars in daylight?

Basically, ultra high dynamic range.

Re: Royal Navy says quantum navigation test a success

#68

Post by jackdh »

gnfargbl wrote: post #36

The Imperial College researcher who builds these things describes his research here: https://www.imperial.ac.uk/centre-for-cold-matter/research/q... The page claims that this device attempts to measure acceleration accurately enough that position can be determined (by integrating over time, twice).

It's off topic however on the people page[0] of the above link, I enjoyed going through to try and spot the photoshopped in ones!

[0]https://www.imperial.ac.uk/centre-for-cold-matter/people/

Re: Royal Navy says quantum navigation test a success

#69

Post by conradev »

themodelplumber wrote: post #19
jchallis wrote: post #13

This is the most obvious practical application of my PhD topic. A Bose Einstein Condensate is an extremely sensitive detector of gravity- a nuclear submarine could use it to make an ultra-accurate map of the world based on variations in the gravitational constant g. This would remove one of the primary reasons subs need to surface , in order to GPS lock. It’s a naval chart that would not require surfacing. A French p…

Fascinating. Q for you since you are so clued in. I am a ham radio operator and was thinking about novel forms of signal propagation. I landed on the idea of gravitons. Could gravitonic signal propagation be done somehow? While researching, I keep coming across familiar terms I know from radio land. Just curious if the fields here could be harnessed for communication. Thanks.

The Three-Body Problem science fiction series involves gravitational waves. I’m not going to spoil it, but the series is a great read :)

Not quite possible today, though, as others have pointed out

Re: Royal Navy says quantum navigation test a success

#70

Post by tomas789 »

As mentioned here [1] they use atom interferometry to build extremely precise sensors of acceleration and rotation. This is everything needed to build an inertial navigation system (INS). This is completely independent of any external system. My guess is that this is what makes is so interesting for subs.

Probably the biggest issue with INSs is accuracy of the raw IMU measurements. The acceleration must be integrated twice. That means any error in the measurement gets exponentially larger with time. Rotation velocity measurements are integrated only once (some IMUs measure absolute orientation but it is not the case here) so the error does not explode as fast. Is is the combination with translation that is problematic. If you rotate around vertical axis by 90deg +/- 1% and then travel for 1000km +/- 1% the rotation accuracy will cause bigger error in final location.

To have an INS capable of long time operation without any other means of drift correction one has to nail many other things.

- Gravitational constant varies and you have to have an accurate map of it. We might not have a good enough one. I don't know. The subs could collect their measurements and perform a large scale optimization to increase the accuracy of this map.

- The rotation of earth gets added to the rotation speed measurements. The rotation is not constant (hence the leap seconds from now and then). We have to be able to extrapolate it well enough.

- Sampling rate of the quantum IMU has to be high enough. How usefull is the most precise measurement if you can measure only once in 10 minutes? Traditional IMUs sample at 1 kHz and more.

- Does the new quantum gyroscope add enough value to the accuracy of the final IMU compared to Fibre-optic gyroscopes? They are incredibly accurate as they are based on laser interferometry and then can sample at high frequency. Plus they are an established technology which partially benefits from economy of scale [5] because they are used in airplanes [6].

- The measurements of both rotation velocity and acceleration have to be measured in 3 axes. Are the relative orientations and translations of those axes stable enough as the device moves?

- Is the noise present in the measurements corelated to something or is it truly random? The corelation could mean an systematic error to the state estimate.

- You will likely also have to have an atomic clock on board labeling each IMU measurement as soon as it is made. But this is not a problem nowadays as one can have a small Rubidium-based atomic clock in a package starting to resemble a chip [2] [3] [4].

- And of course you will need enough computing power to calculate everything. I'm not sure how modern hardware they are allowed on board of nuclear-carrying subs. This is slight problem for things like Mars rover as due to the testing requirements the main chip can be easily 30 years old when the rocket is launched [7].

Also, the situation is not as bad as we can utilize the sensor fusion and correct lots of errors caused by IMU measurements. From the top of my head one can obviously measure water pressure which estimates depth (with some error). Sea bed topology could be other type of measurement but my guess is that this measurement is too crude compared to the accuracy of the quantum-based INS.

[1] https://www.imperial.ac.uk/centre-for-cold-matter/research/q...

[2] https://eu.mouser.com/new/microchip/microchip-macsa5x-atomic...

[3] https://www.sparkfun.com/products/14830

[4] https://www.accubeat.com/nano-atomic-clock

[5] https://emcore.com/wp-content/uploads/2016/12/EMCORE-Commerc...

[6] https://www.airbus.com/en/products-services/space/equipment/...

[7] https://bigthink.com/hard-science/perseverance-rover-brain/

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