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Fascinating - I wonder what the procedure is for a jammed propeller on a sub. I’m used to airplanes, which have redundancies for everything, but a sub propeller
by philip1209 2y ago
Fascinating - I wonder what the procedure is for a jammed propeller on a sub. I’m used to airplanes, which have redundancies for everything, but a sub propeller is really a single point of failure. Potentially seaweed or rope could become entangled, right?
Would the sub typically have to surface to manually clear the propeller? Or, does it have enough torque to just (noisily) obliterate most entanglements?
- mmooss 2y agoIf fishing nets / lines can stop a sub, it would save money on mines.
- kqr 2y agoUnderwater nets were a common defense against submarines during the second world war, protecting harbours and the like. I have no reason to think the case is otherwise now.
- mmooss 2y ago'Net' is a generic term. I have a 'computer', NOAA has a 'computer', but they aren't the same thing. I would be surprised if a fishing net was sufficient to stop a military sub. Also, subs now are a lot more capable than they were then.
- deleted 2y ago[deleted]
- UltraSane 2y agoModern nuclear subs turn the prop with hundreds of thousands of horsepower. That is very hard to stop.
- simne 2y agoThey are in actively using, where convenient to block large water area. As even in war ports, usually active traffic. Second reason why now limited usage, WWII submarines was very limited power, many experts consider them as just high-speed boats with extremely limited underwater capabilities, but modern submarines are really powerful, especially nuclear.
- bell-cot 2y agoIf a fishing net or line was strong enough to stop a sub, then no sane commercial fisherman would ever pay the extra $$$$$ for it, to get that that level of overkill. Plus, the "nuclear-strength" net or line would weigh a LOT more, and fishing involved plenty of hauling your stuff out of the water & other handling.
- mmooss 2y agoFor safety, you do not want it to stop the sub. You want the sub to tear right through it or else the sub is going to take your boat with it, and what if the sub decides to dive?
- bell-cot 2y agoSorta kinda. The sub could be stopped, in the sense of "badly tangled in our equipment, and will need to stop and get untangled", without actually hauling the fishing boat along after it. Maybe the equipment wasn't well secured to the boat. Maybe your savvy crew realized the problem and cut loose. Either way, you're out some expensive equipment.
- Animats 2y agoHere's a modern commercial fishing net: [1] The net itself isn't that heavy per unit area; it's just big. The top support line of the net is a string of floats, like pool lane markers, but larger. They're fishing for herring, not the Great White Whale. Anti-submarine nets are far, far heavier.[2] MESH ROPES: - flexible steel galvanized wire rope This is a single strand, flexible steel galvanized wire rope consisting of 70 wires and 21 hemp yarns. It is one-inch in diameter, has a breaking strength of 98,280 pounds and is internally lubricated and protected against the action of salt water by saturating the fiber cores with a preservative composition. It weighs 1.8 pounds per running foot and is supplied on reels carrying 3,000 feet of wire and weighing 5,000 pounds packed for shipment. The top support line of a submarine net looks like a bridge cable. The floats are the size of cars or larger. [1] https://www.youtube.com/watch?v=k_CP6VtgDVc https://www.youtube.com/watch?v=k_CP6VtgDVc [2] https://maritime.org/doc/netsandbooms/index.php https://maritime.org/doc/netsandbooms/index.php
- mupuff1234 2y agoI think divers can be dispatched from the sub.
- m4rtink 2y agoAlso if the propeller still ends up inoperable, the sub could in an emergency also use buoyancy control to both possibly tear free from entanglement but even to travel forward, by adjusting the dive planes, to make it also go forward instead of just up and down.
- FungalRaincloud 2y agoI understand how this works, but for some reason, when I read your comment, I thought of Flappy Bird.
- nradov 2y agoThere are plenty of airplanes which have only a single propeller. You can find videos online from light aircraft where the propeller literally fell off in flight. Sub propellers have a lot of torque. There's no way that one would really get entangled by seaweed. But thick ropes, cables, and heavy fishing tackle are a risk. Every military sub carries qualified divers who could manually cut it free as a last resort.
- philip1209 2y agoSorry, I was referring to Part 121 operations and missed it in an edit.
- traceroute66 2y ago> Every military sub carries qualified divers The same divers who occasionally "inspect" undersea cables. :)
- potato3732842 2y agoThey've even been alleged to "maintain" pipelines.
- nradov 2y agoThose are usually different divers, sent as detachments to certain boats only for special missions. They are trained in using closed-circuit gear and perhaps in saturation operations, and aren't part of the submarine's standing crew. The sub's standing crew would typically have a few qualified divers trained in just the basics. They would only use open-circuit gear on shallow bounce dives for inspections and light maintenance. Anything more complex would require bringing in a dedicated dive team.
- sgarland 2y agoMy boat’s divers were definitely trained in more than just the basics, including closed-circuit. I don’t think it was regularly used, but they knew how to. If you’re somewhere you aren’t supposed to be, and you have to dive to fix or inspect something, you don’t want to be sending bubbles up. You’re on your own in the ocean, whether civilian or military, sub or surface. You have to be able to handle any and all potential issues.
- hindsightbias 2y agoIf silence is important, modern subs have divers and they can work on it w/o surfacing. In peacetime they'd probably want to surface and concentrate on not damaging anything. I would guess they test props against real-world commercial fishing nets as part of some qualification process.
- potato3732842 2y ago>I would guess they test props against real-world commercial fishing nets as part of some qualification process. I assume enough nets have been run over by various vessels over the centuries that they can simply predict performance by looking at the design and plugging key parameters into a formula or table.
- Retric 2y agoThe propellers on nuclear subs are powerful enough to ignore seaweed and almost anything else, it’s (edit: 100’s of thousands HP) rotating a multi story steel building with literally tons of momentum. They do have divers which can get out without surfacing to deal with some problems, but Nuclear subs can move forward without the propeller. Water is so dense those stubby wings you see on the side can when angled properly create forward thrust when the sub moves up or down which they can do repeatedly by adding and removing water from a ballast tank. Essentially acting like gliders who can swap gravity to keep going.
- quickthrowman 2y agoIt probably isn’t millions of HP, 746MW is roughly equal to 1 million HP. Regardless, it’s still several hundred thousand horsepower driving the propeller, so your point still stands!
- Retric 2y agoGood catch, I remember someone referring to a sub that way and never double checked the numbers.
- pandemic_region 2y agoright, horsepower not hit points I see now.
- yial 2y agoAccording to Wikipedia for USS Virginia class subs, the propulsion is 1 × S9G nuclear reactor280,000 hp (210 MW).
- bogeholm 2y agoAccording to Wikipedia, the reactor on a Virginia-class sub has 280,000 hp (thermal, I guess) and 2x40,000 shp steam turbines. So a little less oomph than 2 out of the 5 fuel pumps on a Saturn V, just for an irrelevant comparison ;)
- 2y ago
- shim__ 2y agoRegular propellers somwtimes feature an rope cutter. If that doesn't work the sub could still surface and dispatch divers to free the prop.
- andrewflnr 2y agoI would be shocked (and impressed) if military subs had that. It sounds noisy.
- Onavo 2y agoMaybe they can add a backup MHD drive (those are mostly solid state) like ram air turbines on a plane.
- bhhaskin 2y agoI would imagine they would have cable cutters built in, but maybe that would effect stealth.