The US Navy is experimenting with a replacement for GPS (which doesn’t work underwater) in the form of cosmic muons (which do.) Task & Purpose’s report begins,

Task & Purpose said:

The Navy is researching a new technology that could help sailors and Marines navigate in places where the Global Positioning System just doesn’t work.

Unlike GPS signals, cosmic ray muons are a natural source of radiation that can pass through rock, buildings and earth and can be used at high latitudes north of the Arctic Circle, where GPS satellites do not work well due to their orbital constraints, the Office of Naval Research wrote in a press release on Tuesday.

(The Navy is testing a GPS-like device that doesn’t require satellites “The future is extremely bright for this line of research.”.) The press release the article mentions is How Science is Finding Ways to Navigate in GPS-Denied Environments

The Task and Purpose piece also quotes from a paper published in Nature Scientific Reports Muometric positioning system (μPS) with cosmic muons as a new underwater and underground positioning technique in 2020, [B]y utilizing this universality and relativistic nature, cosmic muons have a potential to be used for positioning the receiver detector located underwater or underground three dimensionally with a great accuracy.

From what the Nature article, which is a challenging read, says, the technique’s based on measuring the flight time of highly-relativistic muons between a reference detector at the surface and the final detector under the water. There are three or more reference detectors arrayed on the surface with positions and time-references determined by GPS. Presumably the underwater detector also needs to know what time it. The final picture shows a cable joining the surface detector and the underwater detector (which seems to somewhat defeat the purpose). It also talks about taking ~100 days to make a measurement.

It appears (to me) that the technique described in this paper is aimed at making very accurate measurements of slow seafloor movements. Otherwise, I’m not sure how one would do this. EM waves (laser beams?) and pressure waves (sonar) probably don’t propagate well enough or with sufficiently reliable velocity, especially in water with temperature and salinity gradients, etc. The muons supposedly travel very close to the speed of light, >0.9999999c.

btm said:

The US Navy is experimenting with a replacement for GPS (which doesn’t work underwater) in the form of cosmic muons (which do.) Task & Purpose’s report begins,

Task & Purpose said:

The Navy is researching a new technology that could help sailors and Marines navigate in places where the Global Positioning System just doesn’t work.

Unlike GPS signals, cosmic ray muons are a natural source of radiation that can pass through rock, buildings and earth and can be used at high latitudes north of the Arctic Circle, where GPS satellites do not work well due to their orbital constraints, the Office of Naval Research wrote in a press release on Tuesday.

(The Navy is testing a GPS-like device that doesn’t require satellites “The future is extremely bright for this line of research.”.) The press release the article mentions is How Science is Finding Ways to Navigate in GPS-Denied Environments

The Task and Purpose piece also quotes from a paper published in Nature Scientific Reports Muometric positioning system (μPS) with cosmic muons as a new underwater and underground positioning technique in 2020, [B]y utilizing this universality and relativistic nature, cosmic muons have a potential to be used for positioning the receiver detector located underwater or underground three dimensionally with a great accuracy.

From what the Nature article, which is a challenging read, says, the technique’s based on measuring the flight time of highly-relativistic muons between a reference detector at the surface and the final detector under the water. There are three or more reference detectors arrayed on the surface with positions and time-references determined by GPS. Presumably the underwater detector also needs to know what time it. The final picture shows a cable joining the surface detector and the underwater detector (which seems to somewhat defeat the purpose). It also talks about taking ~100 days to make a measurement.

It appears (to me) that the technique described in this paper is aimed at making very accurate measurements of slow seafloor movements. Otherwise, I’m not sure how one would do this. EM waves (laser beams?) and pressure waves (sonar) probably don’t propagate well enough or with sufficiently reliable velocity, especially in water with temperature and salinity gradients, etc. The muons supposedly travel very close to the speed of light, >0.9999999c.

Um, what? Knee jerk reaction, a pretty awful method.

Cosmic muons travel a long distance downwards, being either the second or third most penetrating particle (depending on energy), the other candidate being the neutron.

Cosmic muons are generated by the interaction of cosmic rays with the atmosphere, so collect enough and what it will tell you is which way the atmosphere is, ie. which way is up. But no more information than that.

> Office of Naval Research (ONR)

On the other hand, the Office of Naval Research (ONR) is a very prominent and sensible organisation, so there must be something in it. The ONR is the world authority on navigation using the stars. The ONR star charts are used to ensure that the Hubble Space Telescope is pointing in the correct direction.

> international projects to address capability gaps in Polar Regions

Fair enough.

> The winning project is a team composed of researchers from Japan, U.K., U.S. and Finland, and will seek to show in nine months a proof of concept of an alternative navigation system in the Arctic using muons with precision equal to that of GPS. They will be using a natural source of radiation called cosmic ray muons as an alternative to the satellite-derived GPS signals. The unique aspect of this work is these subatomic particles pass through rock, buildings and earth.

Still don’t get it.

> the timing difference between ‘pings’ – the signals from a crossing muon in our detectors – can allow the user to measure the distance from one detector to another with multiple detectors allowing location by triangulation.

The chance of one cosmic muon passing through multiple detectors is tiny, and decreases as the square of the distance. The cosmic muon flux is “1 muon per square centimeter per minute”. The chance of it being aligned to pass through two detectors say a km apart would occur only about once in 10^8 minutes. So the object you want to triangulate by this method would have to stay stationary for 600 years to get a single trianulated position.

> After initially testing the system in a large water-immersion tank in the U.K

Even at this small a scale, forget it, too slow.