Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Royal Navy says quantum navigation test a success

thequantuminsider.com

Post reply on HN
Print view View original

221–230 of 279 posts

Re: Royal Navy says quantum navigation test a success

#221

Post by thesz »

wongarsu wrote: post #107
thesz wrote: post #87

Earlier quoted context omitted.

https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensa... "n condensed matter physics, a Bose–Einstein condensate (BEC) is a state of matter that is typically formed when a gas of bosons at very low densities is cooled to temperatures very close to absolute zero (−273.15 °C or −459.67 °F)..." I guess, a special device is needed. The size of such device will be in thousands of mobile phones just in volume needed…

There wasn't much money in miniaturizing them so far. Cooling down tiny amounts of matter is much easier than cooling down larger amounts, so maybe there's hope for a microchip sized BEC in 20 years.

Let us take a look at what boson is.

https://en.wikipedia.org/wiki/Boson

"multiple identical composite bosons (in this context sometimes known as 'bose particles') behave at high densities or low temperatures in a characteristic manner described by Bose–Einstein statistics: for example a gas of helium-4 atoms becomes a superfluid at temperatures close to absolute zero."

Helium leaks as nothing else, even more than hydrogen.

Here's some leak rates of heilum: https://www.researchgate.net/figure/Comparison-of-the-helium...

Let's say we have a um^3 of helium in the device proposed. Let's assume leak rate of 8*10^-9 of cm^3/sec. (1e-6/1e-2)^3/(8e-9) is equal to 1.2499999999999998e-4 - all helium will leak in 1/8 of microsecond in the device proposed.

I hope this helps.

Re: Royal Navy says quantum navigation test a success

#222

Post by bluGill »

bequanna wrote: post #151
bluGill wrote: post #138

Earlier quoted context omitted.

The earths magnetic field is not constant. I don't know how much it changes, but I know magnetic north drifts a bit every year. And every once in a while the field reverses (IIRC we are like 10k years overdue for a reversal if we read the history of them right - a lot of guesses go into that of cousre)

Right, but it seems it is constant enough in the near term for practical purposes.

I didn't mean to imply that it wasn't useful for practical purposes. That is what the article is about. I just meant to point out that there are limits and disadvantages to work around. I'm expecting to make this useful they will have to have a team to constantly remap the earth, and send those updates to whoever needs the information.

Re: Royal Navy says quantum navigation test a success

#223

Post by eyko »

jedc wrote: post #220
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…

Former submariner here with a quibble on this: > one of the primary reasons subs need to surface , in order to GPS lock While getting a GPS position is helpful, the primary reason a submarine goes to periscope depth regularly is for communications. The Navy needs to send information to submarines and know that they'll get it and take action within a certain timeframe. That's by far the primary driver.

From layman to former submariner, a very silly question I've always wondered about and that I now have the rare chance to ask someone with some expertise: Do submarines mostly roam about or do they tend to stay relatively quiet/idle? I always imagined submarines constantly moving about but at the same time it feels like a waste of fuel.

Re: Royal Navy says quantum navigation test a success

#224

Post by jwithington »

eyko wrote: post #223
jedc wrote: post #220

Earlier quoted context omitted.

Former submariner here with a quibble on this: > one of the primary reasons subs need to surface , in order to GPS lock While getting a GPS position is helpful, the primary reason a submarine goes to periscope depth regularly is for communications. The Navy needs to send information to submarines and know that they'll get it and take action within a certain timeframe. That's by far the primary driver.

From layman to former submariner, a very silly question I've always wondered about and that I now have the rare chance to ask someone with some expertise: Do submarines mostly roam about or do they tend to stay relatively quiet/idle? I always imagined submarines constantly moving about but at the same time it feels like a waste of fuel.

French (& American and Royal Navy) submarines are nuclear powered. No fuel necessary.

They do have measures of "nuclear fuel" remaining, but it lasts about 30 years (at least in the American boats) so generally doesn't impact day-to-day considerations.

Re: Royal Navy says quantum navigation test a success

#225

Post by oynqr »

eyko wrote: post #223
jedc wrote: post #220

Earlier quoted context omitted.

Former submariner here with a quibble on this: > one of the primary reasons subs need to surface , in order to GPS lock While getting a GPS position is helpful, the primary reason a submarine goes to periscope depth regularly is for communications. The Navy needs to send information to submarines and know that they'll get it and take action within a certain timeframe. That's by far the primary driver.

From layman to former submariner, a very silly question I've always wondered about and that I now have the rare chance to ask someone with some expertise: Do submarines mostly roam about or do they tend to stay relatively quiet/idle? I always imagined submarines constantly moving about but at the same time it feels like a waste of fuel.

Layman here as well, but there are probably no fuel concerns because the reactors are constantly running anyway.

Re: Royal Navy says quantum navigation test a success

#226

Post by thatguy0900 »

eyko wrote: post #223
jedc wrote: post #220

Earlier quoted context omitted.

Former submariner here with a quibble on this: > one of the primary reasons subs need to surface , in order to GPS lock While getting a GPS position is helpful, the primary reason a submarine goes to periscope depth regularly is for communications. The Navy needs to send information to submarines and know that they'll get it and take action within a certain timeframe. That's by far the primary driver.

From layman to former submariner, a very silly question I've always wondered about and that I now have the rare chance to ask someone with some expertise: Do submarines mostly roam about or do they tend to stay relatively quiet/idle? I always imagined submarines constantly moving about but at the same time it feels like a waste of fuel.

I wonder what the fuel difference is between fighting the currents and generating electricity while staying in the same area VS just moving around

Re: Royal Navy says quantum navigation test a success

#227

Post by gresrun »

eyko wrote: post #223
jedc wrote: post #220

Earlier quoted context omitted.

Former submariner here with a quibble on this: > one of the primary reasons subs need to surface , in order to GPS lock While getting a GPS position is helpful, the primary reason a submarine goes to periscope depth regularly is for communications. The Navy needs to send information to submarines and know that they'll get it and take action within a certain timeframe. That's by far the primary driver.

From layman to former submariner, a very silly question I've always wondered about and that I now have the rare chance to ask someone with some expertise: Do submarines mostly roam about or do they tend to stay relatively quiet/idle? I always imagined submarines constantly moving about but at the same time it feels like a waste of fuel.

While I'm 100% positive the details of operational concerns like this are classified, there are 2 distinct types of submarines today with 2 different objectives:

1) Attack Submarines (e.g. Los Angeles-class & Virginia-class for USN) which usually roam within a designated operations area, surveilling, tracking, and generally keeping tabs on other nations' surface & sub-surface fleet dispositions. These subs typically have multi-week sorties and may intermittently surface for surveillance & comms.

2) Ballistic Missile Submarines aka "Boomers" (e.g. Ohio-class for USN) which are given a strategic area in which to operate and their objective is to remain silent & undetected, waiting for the hopefully-never-coming order to launch their SLBMs. These subs usually have multi-month sorties and often don't surface until the end of their patrol.

Re: Royal Navy says quantum navigation test a success

#228

Post by avidphantasm »

vesinisa wrote: post #133
avidphantasm wrote: post #126

This sounds like fancy next-gen inertial navigation. You’ll still need charts (and ENCs) and still need GPS (for periodic updates to the inertially derived position).

Inertial navigation is a form of dead reckoning. It needs periodic updates (GPS fixes) to stay accurate. If this however works like some other commenters have theorized (by finding reliable matches to the known contour of the bottom of the ocean), it's not a form of dead reckoning and can instead be used as a fix for dead reckoning.

I don’t know how that would work. Most of the ocean (ca. 75% is unmapped) and is constantly changing.

Re: Royal Navy says quantum navigation test a success

#230

Post by George83728 »

sampo wrote: post #207
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…

> It’s a naval chart that would not require surfacing. Other sources say this is about inertial navigation, not based on charts. "Accelerometers measure how an object’s velocity changes over time. With this, and the starting point of the object, the new position can be calculated." https://www.imperial.ac.uk/news/188973/quantum-compass-could...

What's the difference between measuring accelerations and measuring gravity?

I think with any INS system, if you want to be very accurate you need charts of gravitational anomalies. So these seem like one and the same to me.

Post reply on HN