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Royal Navy says quantum navigation test a success

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Re: Royal Navy says quantum navigation test a success

#241

Post by nradov »

timthelion wrote: post #237
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.

Do military subs have antenna buoys on cables that they can raise up without having to surface?

Yes, modern subs typically carry comms buoys. Some are tethered and allow for two-way communication. Others are transmit only and float up to the surface independently.

Re: Royal Navy says quantum navigation test a success

#242

Post by rcxdude »

George83728 wrote: post #230
sampo wrote: post #207

Earlier quoted context omitted.

> 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.

There isn't any inherent difference (indeed, you can do some coarse gravity surveys by basically watching the drift of an IMU relative to GPS), but there's a pretty big difference in terms of the parameters of your sensor. Most gravimeters don't make for good accelerometers and vice-versa. One of the biggest reasons being dynamic range: most gravimeters are only able to sense a very small range around 1g, which means they quickly saturate when there's any significant motion. I don't know if that's something which these quantum sensors can work around, however. (Also, you need a gyro good enough to go along with those accelerometers, which may still be a challenge)

Re: Royal Navy says quantum navigation test a success

#243

Post by ThinkBeat »

gresrun wrote: post #227
eyko wrote: post #223

Earlier quoted context omitted.

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…

Clearly the Ballistic Missile Submarines surfaces intermittently surface for comms as well? If not, they won't know when to set off their missiles making then not very useful as a deterrent

I have often wondered how close to the surface they need to get.

I would presume retractable antennas could be extended from a sub from a non-trivial depth. Or cable attached to buoys Or something much smarter that I have not thought about yet.

Re: Royal Navy says quantum navigation test a success

#244

Post by ThinkBeat »

I have two somewhat related questions:

Can a submerged military submarine let divers "out", and / or divers "in"?

Do they have air locks / water locks?

It would seem possible, enormously dependent on the depth of the submarine. Not just from the perspective of the integrity of the giant uboat but also the integrity of divers.

In movies (which are always "accurate") they put people into torpedo tubes. Which I believe do feature some form of an air locks and ports to open and close. Not sure a person would fit, or if it is physically possible given the operation of the tube.

If possible, can they enter the same way?

My second question is if you can do deep sea fishing? (while submerged) Have fresh as can be sushi?

I figure if you can let a person in and out, that person could go hunt fish and bring it back.

They dont have windows but from sonar does pick up some sea creatures. You could possibly have a harpoon with a sensor on it you could extend to catch fish.

It just seems it ought to be possible. With a nuclear submarine, I think, one of the limits to how long you can operate before requiring supplies is food. I hope a nuclear submarine has a way to creating fresh water from salt water as benefit for having a reactor. at least.

Re: Royal Navy says quantum navigation test a success

#245

Post by yencabulator »

ThinkBeat wrote: post #244

I have two somewhat related questions: Can a submerged military submarine let divers "out", and / or divers "in"? Do they have air locks / water locks? It would seem possible, enormously dependent on the depth of the submarine. Not just from the perspective of the integrity of the giant uboat but also the integrity of divers. In movies (which are always "accurate") they put people into torpedo tubes. Which I believe…

Standard practice for 40+ years: https://en.wikipedia.org/wiki/SEAL_Delivery_Vehicle

Re: Royal Navy says quantum navigation test a success

#246

Post by yencabulator »

ThinkBeat wrote: post #243
gresrun wrote: post #227

Earlier quoted context omitted.

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…

Clearly the Ballistic Missile Submarines surfaces intermittently surface for comms as well? If not, they won't know when to set off their missiles making then not very useful as a deterrent I have often wondered how close to the surface they need to get. I would presume retractable antennas could be extended from a sub from a non-trivial depth. Or cable attached to buoys Or something much smarter that I have not thou…

There's a couple of different "wake up" signals that can reach deeper into water. Their biggest limitation is very low bandwidth, so an attack sub will emerge (/send up a buoy on a tether) to get an updated tactical map.

https://hackaday.com/2020/07/15/the-many-methods-of-communic...

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

Re: Royal Navy says quantum navigation test a success

#247

Post by [deleted] »

yencabulator wrote: post #246
ThinkBeat wrote: post #243

Earlier quoted context omitted.

Clearly the Ballistic Missile Submarines surfaces intermittently surface for comms as well? If not, they won't know when to set off their missiles making then not very useful as a deterrent I have often wondered how close to the surface they need to get. I would presume retractable antennas could be extended from a sub from a non-trivial depth. Or cable attached to buoys Or something much smarter that I have not thou…

There's a couple of different "wake up" signals that can reach deeper into water. Their biggest limitation is very low bandwidth, so an attack sub will emerge (/send up a buoy on a tether) to get an updated tactical map. https://hackaday.com/2020/07/15/the-many-methods-of-communic... https://en.wikipedia.org/wiki/Communication_with_submarines

[deleted]

Re: Royal Navy says quantum navigation test a success

#248

Post by awesometech »

awesometech wrote: post #153
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…

Submarines do not have to surface to get a GPS lock. https://en.wikipedia.org/wiki/Submarine_navigation "On the surface or at periscope depth, submarines have used these methods to fix their position"...GPS being one of them. A submarine can also navigate by the stars without surfacing. https://www.usni.org/magazines/proceedings/2021/october/navi... "This is precisely the information required by the traditional metho…

Why was I downvoted please? I provided facts to my counterpoint.

Re: Royal Navy says quantum navigation test a success

#249

Post by jedc »

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.

Ohio-class submarines (the ones that carry missiles): when they're "on station" they're just tooling around staying as quiet as they can. There's a relevant phrase for them: "Three knots to nowhere"

Los Angeles and Virginia-class submarines are always doing something: doing exercises, transiting from one location to another, etc. And typically multiple things at once. While the boat is transiting from an exercise area to homeport, the team is doing engineering drills, or other kinds of training. Or the forward part of the boat is doing exercises with a carrier battle group while the engineering team is doing engineering drills. (There's ALWAYS engineering drills or maintenance happening.)

Fuel isn't a primary concern: a nuclear reactor is fueled for the life of the boat, so 30-ish years. That said, effective life of a reactor is something the Navy tracks closely, and depending on the life of the boat, the life left in the reactor, some boats are decommissioned as they get close to the end of their fuel life, and others get re-fueled. (And in the case of the USS San Francisco, who had recently been refueled before it hit an underwater mountain, they cut off the front half of the submarine and welded the front half of a recently-decommissioned submarine on, because the reactor and fuel was too valuable to go to waste)

Re: Royal Navy says quantum navigation test a success

#250

Post by jedc »

timthelion wrote: post #237
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.

Do military subs have antenna buoys on cables that they can raise up without having to surface?

antenna buoys on cables? No.

But there are VLF antennas that Ohio-class submarines have to receive low-data-rate comms while submerged.

Any reasonable communications have to be made while at periscope depth. (Which is subtly different than "having to surface"... at PD just the thin mast is out of the water.)

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