There is an article in today’s Financial Times (behind a paywall so no link) suggesting that a working “Quantum Compass” might be 3-5 years away, according to the UK’s Porton Down and National Physical Laboratory. Their (partly military) interest is in a non-jammable non-satellite-based GPS replacement.
This chatty article actually has rather more scientific content than the FT, but focusses on the supposedly equivalent natural mechanism in birds.
I did think of putting this in “Maintenance and Avionics”, but decided that might be a little premature! 
Is there any evidence bird magnetic field direction sense organ actually works like this? They’ve been shown to respond to visual direction clues. PS. British robins don’t migrate.
I have read of one theory which was that birds could see the magnetic field as a shadow in their visual field.
Their (partly military) interest is in a non-jammable non-satellite-based GPS replacement.
How would a compass help that? You can’t practically jam a normal compass, and a quantum compass would not be any better for navigation than any other compass. What is really needed is a super stable accelerometer (inertial navigation) and there is a lot of work going on in that.
How would a compass help that?
That’s a very good question.
However, the article certainly implies more than just knowing your track, or which way you are pointing:
… they work by supercooling trapped ions and reducing the effect of external radiation so they are sensitive only to electromagnetic fluctuations produced by the earth.
Measuring the influence of those fluctuations on the particles should allow scientists to track the movement of a chip containing the trapped ions with extreme precision.
Frankly, at this level of explanation, “electromagnetic fluctuations” could mean almost anything, notwithstanding the “supercooled trapped ions”.
===
I don’t think anybody has proved that their magnetic sense relies on quantum mechanics though it has been suggested for quite a while.is there any evidence bird magnetic field direction sense organ actually works like this?
I have seen research elsewhere claiming that flocking birds (that land en masse, and don’t want to hit each other), land either due north or due south, and not directly into wind as one might assume.
This is a more informative New Scientist Link which seems to be about the same device.
As Peter suspected, it is an accelerometer and has nothing to with magnetism.
It seems the FT should stick to financial journalism.
OK… that is very interesting.
However, I am fairly sure this
“Today, if a submarine goes a day without a GPS fix we’ll have a navigation drift of the order of a kilometre when it surfaces,” says Neil Stansfield at the UK Defence Science and Technology Laboratory (DSTL) at Porton Down.
is bull and that inertial nav is far more accurate than that today.
It may not be complete bull, if he is comparing a decent accelerometer against a very good accelerometer with a detailed gravitational map.
I think INS navigation in submarines must present problems you just don’t find in aeroplanes.
Aeroplanes fly long distances, comfortably higher than terrain for the most part, so that gravity acts mostly downward, and I suspect the average gravity over the whole trip is very much downward, or at least towards the centre of the Earth. This makes INS pretty good for 2D navigation, though perhaps less so for estimating altitude.
A submarine might stay near a coast for a day, with water on one side and rock on the other, and rock has roughly twice the density of water.
According to the back of my envelope:
If you solve for the acceleration in: 1km = acceleration x (one day)^2 / 2,
and then use Newton’s Law of Gravity to see what net mass at what distance could create that fictitious acceleration,
I get 8 Megatons of rock (4 MT net) at a distance of one kilometer.
Which isn’t very much, in the context of a landmass. (Order of magnitude: 400m x 100m x 100m with relative density=2).
Caveat: I do not do this for a living, so I might have put too many zeroes somewhere!
I’m sure it won’t be in smartphones in 3-5 years, but in 10-15 it might – if we are still using smartphones then!
…is bull and that inertial nav is far more accurate than that today.
I don’t think so. I even doubt their one kilometre accuracy after a full day. That’s a very long time for a standalone system. A big problem are the tiny initial errors in position and orientation that will be integrated over such a long time and result in a large deviation, even if the sensors themselves were ideally perfect. Typical airliner INS systems (100,000$+) guarantee something like RNP-5 (i.e. position within a radius of 5NM with 95% probability) after only two hours of flight. Here is a good overview of the error sources and their order of magnitude: http://www.vectornav.com/support/library?id=76
Fascinating post about the off-vertical gravity effects! Clearly the submarines must have a solution, otherwise they could not sail hundreds of nm under the northern polar ice cap, end up under a patch known to have a relatively thin ice, surface through it (breaking a hole in the ice on the way up), and launch the ICBMs, and they’ve had that capability for decades.
Typical airliner INS systems (100,000$+) guarantee something like RNP-5
I recall, from a pre-9/11 cockpit visit on a 747, they are normally within 1-2nm after crossing the Atlantic (7 hrs?). So I would think the RNP-5 is just a nav performance label – just like the stupid RNAV1/PRNAV crap which is being thrust upon GA despite even the cheapest and nastiest GPS outperforming RNAV1 by a factor of ten.
That Vectornav link is very interesting but I don’t see much evidence for their statement
With the rapid advances in MEMS gyro technology, the overall performance of MEMS gyros are quickly approaching that of the low end FOGs
in what is actually on the market. I think there is still a 100x gap between the best MEMS and the cheapest FOG gyros.
Personally, I would install an uncertified “INS box” ASAP if there was one going for substantially less than the current €20k FOG solution (which takes in a GPS antenna and outputs NMEA… just like that).
