 Supercavitation Submarine, possible? |
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 Apr 3 2007, 09:17 PM
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#26
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Target  Group: Members Posts: 34 Joined: 2-April 07 Member No.: 11,358  |
Hmm- but how would a supercavitation sub compare to a hydrofoil craft? If you're looking to compete with surface craft, I don't see much advantage to the sub: you're already giving up stealth, and a surface craft would have far more ability to navigate just because you'd be able to see where the heck you were going.
Supercavitation subs might work better as a variation on what's been mentioned before- you position them quietly in neutral waters, pre-check their flight-path (that's basically what it is, after all) and wait for the go signal. At the point you get it, you rocket into range and deliver your payload before the enemy can react. Depending on what the sub's carrying you might have a couple score cruise missiles heading for a land-bound target or a spread of torpedoes targeting their docks. Just make sure that your inbound vector's set so that you can either hide or get back out again as quick as possible. |
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Apr 4 2007, 12:44 AM
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#27
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Moving Target Group: Members Posts: 192 Joined: 29-December 06 Member No.: 10,483 |
I think a lot depends on how loud supercavitation actually is, versus the speed you are getting. A couple hundred miles an hour is damn fast for anything maritime, and underwater you really don't have to worry too much about surface conditions which would kill a hydrofoil. Though I can't see it as much use for charges. After all if you really want to give them a surprise hit you could launch cruise missiles from the same sub.
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Apr 4 2007, 01:27 AM
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#28
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Moving Target Group: Members Posts: 239 Joined: 21-August 05 Member No.: 7,586 |
Just because supercav subs can go supercav does not mean that they have to.
Personally i believe that future navies wont have surface warships and submarines, but supercavitation capable ships that can do all the tasks of the former.. Again! Just because your ship is capable of supercavitation does not mean that it is always wise to use it. In addition to that i believe supercav is loud, in fact so extremly loud that i wonder if passive sonar systems might have trouble to determine the source due to echo and other problems. @ garro: having oots in your sig, but not recognizing the latest episode... shame on you.... :silly: |
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Apr 4 2007, 01:32 AM
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#29
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Moving Target Group: Members Posts: 870 Joined: 2-October 06 From: Athens Ga Member No.: 9,517 |
Actually I am thinking about the poor whales and dolphins on the wind screens!
Maeel - Ah I got it. That part in the jail was my favorite part so far. I would love to get a T-Shirt with just that panel on it. |
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Apr 4 2007, 01:48 AM
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#30
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Moving Target Group: Members Posts: 239 Joined: 21-August 05 Member No.: 7,586 |
One of my players got a supercav freighter as some sort of mobile home, because i was inspired by firefly. now he plays his char to be an enviromentalist, and he also noted that he only uses supercav in emergencies because 'da poor whales cant see shit, if i use dat alot...'
@ garro: i find xykon and company extremly funny...especially when they talk about sacrificing hobgoblins... |
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Apr 5 2007, 02:24 PM
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#31
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Old Man Jones Group: Dumpshocked Posts: 4,415 Joined: 26-February 02 From: New York Member No.: 1,699 |
On a silly note, supercavitation appears in this week's Iron Man comics.
A "rogue" artificially-intelligent version of the Iron Man armor, needing to increase it's ability to move quickly in underwater combat, vents compressed air at high pressure across most of it's body surfaces to achieve a partial supercavitation effect. The plausibility of this actually working in real life is suspect, but it was a fun fictional use. I found an interesting article on supercavitating bullets. Apparently designed for greater penetration through body tissues (rather than speed), it probably would not be really useful in most combat situations, but might be of use in big game (metacritters?) hunting where penetrations depths of feet or even yards might be required. I still believe that for a combat submarine, the fact that you would be alerting your targets that you have arrived in the area outweighs any possible benefit of speed. It's not warp drive, after all, even at 200 MPH it would still take a good chunk of time to travel any significant distance. Even if you shut off the supercav drive when you get there, every enemy ship in the area would have heard your approach, and have plenty of time to go full alert and start active sonar sweeps and arm everything they've got. As opposed to a normal sub being able to deliver a strike before anyone even realizes it's there. Alerting the enemy is a bad thing. I concede that supercav might have application for a pure non-stealth transport, but in the vast majority of cases such a craft would be inferior to using simple air transport. |
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Apr 5 2007, 06:03 PM
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#32
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Neophyte Runner Group: Members Posts: 2,174 Joined: 13-May 04 From: UCAS Member No.: 6,327 |
On another note, here's a site on supercavitating vehicles in a fictional game world.
http://www.deepangel.com/html/empire_-_synopsis.html Looks like it's a game in progress. |
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Apr 5 2007, 06:43 PM
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#33
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Creating a god with his own hands Group: Members Posts: 1,405 Joined: 30-September 02 From: 0:0:0:0:0:0:0:1 Member No.: 3,364 |
Supercav would be usefull for deep-water strategic repositioning
crossing entire oceans in days instead of weeks. otherwise, you'd just use an impeller tunnel or electro-static propulsion. nice and quiet. |
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Apr 7 2007, 10:15 PM
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#34
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Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
This isn't a problem for deployments, though. A fusion-powered submarine able to travel at 200 knots can get to trouble spots in 1/7th the time of a fast-moving conventional sub. Then it go stealthy and quiet.
Incorrect. There is contact with water in several areas in supercavitating submarine designs, especially the "skis" that keep the submarine from falling out of its own bubble. Subs are buoyant in air, not in underwater air bubbles. Sensors, communications, and other items can poke outside the bubble at a necessary increase in strain. So can propulsion units, like the propellers of hydrofoils.
Would you provide a reference explaining that?
What, magic doesn't work in supercavitating subs? :) Just send the sub's mage astral and have him scout ahead, or use a variant of the "x-ray vision" spell of SR3. As for erosion, no, water won't inflict that on a properly designed sensor probe. Handling water at hundreds of knots is nothing new for pumps and pipelines; I'm sure the lessons there can be put to good use on supercav sub probes.
If you have a coastal or riverine navy with no interest in crossing oceans, I agree. But there is a potent force multiplier in being able to move your naval assets about at hundreds of knots - you can effectively have fewer ships in more places at once. Once so positioned, they'd have to behave like normal subs or become target practice, but that doesn't change the utility of being able to rapidly move warships around outside of hostile waters.
That's a really good point. There are easier ways of moving ships quickly than supercavitating subs. Oh, and going back to the original post: aneutronic boron fusion is unlikely to work. It suffers too many energy losses to sustain its operating temperature. |
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Apr 8 2007, 03:13 AM
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#35
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Moving Target Group: Members Posts: 870 Joined: 2-October 06 From: Athens Ga Member No.: 9,517 |
Why would the communications need to be in the water? We are talking about an air bubble not a force field.
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Apr 8 2007, 02:44 PM
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#36
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Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
If the communications are sound-based or laser-based, you don't want to try to project the signals through the vapor-water interface. It'd be like trying to send them through heavy surf. Easier to stick a communications arm into the water now and then. |
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Apr 8 2007, 04:57 PM
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#37
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Moving Target Group: Members Posts: 239 Joined: 21-August 05 Member No.: 7,586 |
I wouldnt be so sure about that. From what i have read on wikipedia, this kind of fusion is a tricky one, but very promising, if made feasible. D-T reactors are too heavy and too large to be used on ships, not to mention the problems of radioactive fuel and waste. |
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Apr 8 2007, 09:16 PM
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#38
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Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
Yes, boron-hydrogen fusion is promising, but it has a couple of big strikes against it. First, and primarily, the p-B11 reaction is very lossy. At the conditions necessary to sustainably generate power from the p-B11 reaction, you suffer 1.74x as much energy loss to bremsstrahlung radiation as you're generating from the reactions. http://en.wikipedia.org/wiki/Aneutronic_fu...n#Power_balance Or, to summarize: the p-B11 reaction won't generate power. There are also some secondary problems once you handwave pass the whole "doesn't generate power" part: Second, p-B11 has a low reaction rate and very high operating temperatures, resulting in the need for a MUCH larger reactor (much more plasma volume) than a deuterium-tritium reactor. Contrary to your assertions that a D-T reactor would be larger, a p-B11 reactor would be the larger reactor by a factor of at least 700 (for the same power output), and potentially 2100. http://en.wikipedia.org/wiki/Aneutronic_fu...n#Power_density Third, p-B11 does generate neutrons in some side reactions, accounting for 0.2% of power produced. As neutron shielding thickness and mass is determined as a function of individual neutron energies, not neutron quantities, p-B11 would need quite substantial shielding to handle the 2.9MeV neutrons coming from the reaction - and the much larger reactor volume will make the shielding heavier than that of an equal-power D-T reactor's shielding. In comparison, D-T fusion has some issues with neutron radiation generation and the associated waste, but this is a problem that has been largely solved by 7 decades of neutron-filthy fission engineering. In exchange, D-T fusion has the advantages of the most compact form of fusion reactors, easiest fusion reaction to achieve, and provides an easy way to harness the energy released from the fusion reactions thanks to the volumetric deposition of neutrons in the reactor wall. |
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Apr 8 2007, 11:31 PM
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#39
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Moving Target Group: Members Posts: 239 Joined: 21-August 05 Member No.: 7,586 |
Doesnt sound like 'wont generate power' to me. sounds more like a maybe yes maybe no. Why would scientist research this, if they know that it will not work.
Which would be very different from several meters of shielding for D-T Fusion, not to mention that generating power via neutron heated steam is bulky and inefficient, and if it comes to submarines its also noisy. not to mention:
so as long as there is no scientific statement that says it is definitely impossible, i will assume that they managed it by 2070.... |
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Apr 9 2007, 01:43 AM
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#40
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Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
Why don't you read what you quoted. It's recommended that there's a 200:1 power gain, while hydrogen-boron-11 fusion occurs at a 1:1.74 LOSS. The reason that scientists research this is because of the attraction of aneutronic fusion. It's alluring, it's useful, and if it works out, it's good stuff. Despite the odds, it's worth investigating to see if there's a loophole. But when you put all the material together, there isn't a loophole. And what you quoted even says the feasibility is low.
You ignored it my last post, so I'll lay out the basic math for you: A proton-Boron-11 fusion reactor needs TWO THOUSAND, ONE HUNDRED TIMES the volume of a D-T reactor. I don't care if the D-T reactor needs 10 meters of radiation shielding while the p-B11 reactor needs 1-meter, the p-B11 will still have heavier shielding because the reactor is 2100x bigger than the D-T reactor of the same power output. Take a moment and just ponder what "2100x the size" means. That's a speedboat compared to an Aegis-class missile cruiser. It's a typical car compared to 2-mile train. Variations in surface thickness do not come close to closing the gap when there's a 2000-fold difference in volume.
So screw steam. Use the neutrons to heat heat exchangers that warm a gas and drive gas turbines. Or heat up heat exchangers that can power thermoelectric units.
What you just quoted in no way supports your conclusion. Did you read the material before you posted? |
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Apr 9 2007, 04:07 AM
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#41
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Moving Target Group: Members Posts: 239 Joined: 21-August 05 Member No.: 7,586 |
i read: this would open up the possiblity of net energy production which sounds very much like a' maybe it can be done' to me.
The way i read it, only if you compare power density at the same pressure. However,
was what i tried to disprove with
Not to mention you require two volatile fuels (one highly radioactive), which would pretty much crap to have on a submarine. You might be right that aneutronic fusion is not doable with conventional designs like the tokamak. Still:
I dont claim to be an expert in plasma physics, but as long as it is being researched as a possible powersource, i assume that there are REAL experts, who work with this stuff on a daily basis. And if they believe that there might be a loophole, then thats good enough for me. |
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Apr 9 2007, 07:43 AM
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#42
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Moving Target Group: Members Posts: 556 Joined: 28-May 04 From: Moorhead, MN, USA Member No.: 6,367 |
I wasn't intentionally looking for this, but this video on fusion is really informative and relevant.
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Apr 9 2007, 12:38 PM
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#43
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Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
It's a "may be possible" sort of thing that invokes the fusion research equivalents of unobtainium, like megatesla confinement fields. Practically speaking, it's not feasible.
Actually, when they're run at the same pressure, p-B11 requires 700x the volume of a D-T reactor for the same pressure output. As soon as you start relaxing the similarities so the D-T reactor can run in easier conditions, the advantage grows to 2100-fold.
Yes, there are problems for material design due to the neutron flux, but they're not impossible problems, and there's a huge body of engineering knowledge for solving the issues. And the problem of neutron flux in D-T fusion is starting off from the basis of "yes, we have working solutions, just imperfect ones," while the problem of p-B11 fusion is starting at "it doesn't work, because it suffers more losses than it generates." Of the two, solving the neutron flux of D-T fusion is the easier issue to solve. Trade carbon linings for vanadium linings would be a start, as would switching to D-D or D-He3 fusion.
...yeah. Let's review real world and Shadowrun submarine designs before addressing that objection. In the real world, nuclear submarines carry diesel back-up power plants with substantial tonnages of diesel aboard (not to mention torpedo fuel, explosives, flammable hydraulic oils, etc.). The typical oxygen generation system of submarines also generates substantial quantities of hydrogen. Non-nuclear military submarines carry even more diesel and, in the cases of those subs with fuel cell AIPs, they also carry that "volatile" fuel you mentioned, hydrogen. I'm sure you're aware that the quantity of hydrogen required by fuel cells dwarfs the quantity of hydrogen (in deuterium and/or tritium formats) required by fusion reactors. In Shadowrun (3rd edition), a multitude of submarine options use volatile fuels, not the least of which are fuel cell power plants. Again, I'm sure you can make the comparison of hydrogen requirements for a fuel cell vs a fusion reactor. In short, the volatility of hydrogen in a submarine is not an exceptional problem, particularly not in the tiny quantities required of a fusion-powered submarine. As for radioactivity, tritium emits beta particles that can be stopped by a sheet of paper. If it's really bothering you, shift to a deuterium-deuterium reaction or D-He3, both of which are still much more favorable than p-B11.
It shouldn't be good enough for you - you should maintain a healthy skepticism because fusion research tends to be filled with pie-in-the-sky dreamers who can claim abundant PhDs. Predictions of fusion performance by the most knowledgeable insiders have consistently outpaced actual performance. |
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