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Post by Lokifan on Jul 18, 2014 1:42:50 GMT
I was watching the show "The Last Ship" a few nights ago.
The plot was that the engines failed on an Arleigh Burke destroyer--a pretty big US Navy ship--because they essentially lost all their cooling water. They needed to get electricity to a lab onboard or vital research would be destroyed, as well as make headway to a nearby island for fresh water to cool the engine (and keep the crew alive).
They did this by launching three parachutes tied to the bow of the ship. The wind pulled the parachutes like kites, and the ship was pulled along at 3-4 knots. Pulling the ship spun the propeller, and they drove the ship's generator from the propeller's shaft, giving them enough power to run the critical lab.
Myths are:
1) Can parachutes pull a destroyer?
2) Can a spinning a propeller on a ship like this drive a generator?
I'm thinking no, that there wouldn't be enough power in the "kites" to move the ship, but then again...the ship IS massive but the ocean is about as frictionless as you could hope for.
Keeping the "kites" from fouling each other would also seem problematic.
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Post by the light works on Jul 18, 2014 2:11:38 GMT
I was watching the show "The Last Ship" a few nights ago. The plot was that the engines failed on an Arleigh Burke destroyer--a pretty big US Navy ship--because they essentially lost all their cooling water. They needed to get electricity to a lab onboard or vital research would be destroyed, as well as make headway to a nearby island for fresh water to cool the engine (and keep the crew alive). They did this by launching three parachutes tied to the bow of the ship. The wind pulled the parachutes like kites, and the ship was pulled along at 3-4 knots. Pulling the ship spun the propeller, and they drove the ship's generator from the propeller's shaft, giving them enough power to run the critical lab. Myths are: 1) Can parachutes pull a destroyer? 2) Can a spinning a propeller on a ship like this drive a generator? I'm thinking no, that there wouldn't be enough power in the "kites" to move the ship, but then again...the ship IS massive but the ocean is about as frictionless as you could hope for. Keeping the "kites" from fouling each other would also seem problematic. to place a LITTLE bit of technical information into the mix: on the kite crew, our standard lifters were 180' skydiving parachutes. we flew them on 5/8" line, and in high wind conditions they were capable of dead lifting more than 400 pounds. not sure what this translates into in terms of direct pull. fouling would not be a problem - as long as the lines were properly adjusted. you can easily bias them to fly to the right or left of the wind line. I also know that there are rigs on sailing vessels that use the propeller to drive the generator while they are under sail - and if it is an electric drive ship, with DC motors, it may be possible to generate minimum power with relatively slow headway. - however, I know very little on the specifications on this.
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Post by Lokifan on Jul 18, 2014 4:08:03 GMT
The parachutes in the show were rectangular, so I suppose that makes them steerable. However, each was tied to the ship by a single rope. I was looking for a clip of the show but couldn't find it. It was from episode 4, "We'll Get There", if anyone has On Demand from their cable company. I just rewatched the scene. Another thing that struck me as strange was the way they were launched. The ship's engineer said that pilot chutes were loaded into "launchers" that were in turn mounted on an M-16 rifle. The pilot chute would be fired up, then it pulled the actual chute up when they caught the wind. However, I think the CGI guys didn't understand the idea, as they seem to not understand the difference between the pilot and the main chute--it looked more like the main chute was fired up (but that could also be "poor" camera work as it was a quick shot and Micheal Bay was involved . Looking up the specs on the ship, a small Arleigh Burke class destroyer displaces 8300 tons. That's a lot of weight, but what it takes to overcome inertia and water friction, I don't know.
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Post by the light works on Jul 18, 2014 5:23:03 GMT
The parachutes in the show were rectangular, so I suppose that makes them steerable. However, each was tied to the ship by a single rope. I was looking for a clip of the show but couldn't find it. It was from episode 4, "We'll Get There", if anyone has On Demand from their cable company. I just rewatched the scene. Another thing that struck me as strange was the way they were launched. The ship's engineer said that pilot chutes were loaded into "launchers" that were in turn mounted on an M-16 rifle. The pilot chute would be fired up, then it pulled the actual chute up when they caught the wind. However, I think the CGI guys didn't understand the idea, as they seem to not understand the difference between the pilot and the main chute--it looked more like the main chute was fired up (but that could also be "poor" camera work as it was a quick shot and Micheal Bay was involved . Looking up the specs on the ship, a small Arleigh Burke class destroyer displaces 8300 tons. That's a lot of weight, but what it takes to overcome inertia and water friction, I don't know. you don't have to actively steer the kite if it is just used as a lifter. they don't pull as efficiently as if you can put them directly into the "power zone" but you really don't get much time in the power zone, anyway. I happened to have seen that episode out of the corner of my eye, which is how I know that the arrangement is quite possible as long as they are bridled properly. our standard launch was a "rip launch" where we laid out the entire line, and then allowed the lifter to inflate. it, in turn would pull up the line hard enough to inflate the spinsocks. (a light wind line was 2 90' spinsocks on a kite - a high wind line sometimes had 3, just because we could. in light wind, we could fly our 300' parafoil, but that was custom built rather than a retired parachute - our kitemaker tried a 500' foil, but we could never get it to inflate right - and it was way too powerful, anyway. we also had "the bruise" which was a 250' parachute. (yes, black and blue) - LONG before kiteboarding was invented, our kitemaker used it for bouncing down the beach at about 30 feet per bounce. kite powered boats are a thing. that much is factual - and they are more efficient per square foot of sail area. the key question is whether that is enough sail area. www.gizmag.com/cargill-ship-will-be-largest-ever-to-utilize-kite-power/18005/
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Post by the light works on Jul 18, 2014 5:32:57 GMT
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Post by Lokifan on Jul 18, 2014 5:52:07 GMT
Nice catch on the kiteboating. I found the Kiteboat Project site that's pretty amazing--and they're local to San Francisco. Records have been set using kites to power boats, and they have had electrical generators powered by the boat motion (from Wiki). Egads, it might be possible...and it would make GREAT television to do it in real life.
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Post by the light works on Jul 18, 2014 12:54:07 GMT
Nice catch on the kiteboating. I found the Kiteboat Project site that's pretty amazing--and they're local to San Francisco. Records have been set using kites to power boats, and they have had electrical generators powered by the boat motion (from Wiki). Egads, it might be possible...and it would make GREAT television to do it in real life. It was a subject we had an interest in on the beach crew. I find it interesting that they have basically transitioned to kiteboarding kites.
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Post by memeengine on Jul 19, 2014 9:38:16 GMT
I'm thinking no, that there wouldn't be enough power in the "kites" to move the ship, but then again...the ship IS massive but the ocean is about as frictionless as you could hope for. I think you'll find that the ocean is far from frictionless. Most of the resistance to movement of a vessel is due to skin friction, i.e. friction between the hull and the sea water. Even a smooth hulled vessel like a modern destroyer is going to take a lot of power to move. Add to that the extra drag of the props and rudder and I would think that the parachutes would produce very little in terms of forward motion. If you then try to turn the prop-shafts to generate power then you're going to be increasing the drag even further. I agree with your concerns about the parachutes fouling each other. It strikes me that unless the parachute rigs have been designed to work together (such as the trio of parachutes used to slow the Apollo capsules down), they would tangle and collapse into each other. There's also the problem that real wind isn't constant in force or direction. If the wind drops or shifts suddenly, the parachutes are in the water. If the wind suddenly picks up (especially if it also shifts direction) will the parachute cable be able to take the strain? You also have the problem of steering. Attaching all of the chutes to the front of the vessel won't allow you to steer in any meaningful way. It also means that, like a hot air balloon, you can only go in the direction that the wind is blowing. There's a good reason that sailing ships had multiple masts and a variety of sails. That set up allowed them to sail across the wind and, even to a degree, into the wind. Another consideration is where the parachutes are flying relative to the ship. You mentioned them flying like kites, which suggests that they are up above the level of the ship. If that's the case, then much of the potential pulling power would be lost because they would be attempting to lift the bow of the ship. To maximize their pulling power, they would need to be straight out in front of the bows. The problem with that arrangement is that the structure of the ship would then act to block the wind from the 'chutes. Finally, if there's enough wind to pull the ship at a constant speed, wouldn't it be easier to jury-rig a wind turbine or two to generate electricity?
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Post by the light works on Jul 19, 2014 11:30:38 GMT
I'm thinking no, that there wouldn't be enough power in the "kites" to move the ship, but then again...the ship IS massive but the ocean is about as frictionless as you could hope for. I think you'll find that the ocean is far from frictionless. Most of the resistance to movement of a vessel is due to skin friction, i.e. friction between the hull and the sea water. Even a smooth hulled vessel like a modern destroyer is going to take a lot of power to move. Add to that the extra drag of the props and rudder and I would think that the parachutes would produce very little in terms of forward motion. If you then try to turn the prop-shafts to generate power then you're going to be increasing the drag even further. I agree with your concerns about the parachutes fouling each other. It strikes me that unless the parachute rigs have been designed to work together (such as the trio of parachutes used to slow the Apollo capsules down), they would tangle and collapse into each other. There's also the problem that real wind isn't constant in force or direction. If the wind drops or shifts suddenly, the parachutes are in the water. If the wind suddenly picks up (especially if it also shifts direction) will the parachute cable be able to take the strain? You also have the problem of steering. Attaching all of the chutes to the front of the vessel won't allow you to steer in any meaningful way. It also means that, like a hot air balloon, you can only go in the direction that the wind is blowing. There's a good reason that sailing ships had multiple masts and a variety of sails. That set up allowed them to sail across the wind and, even to a degree, into the wind. Another consideration is where the parachutes are flying relative to the ship. You mentioned them flying like kites, which suggests that they are up above the level of the ship. If that's the case, then much of the potential pulling power would be lost because they would be attempting to lift the bow of the ship. To maximize their pulling power, they would need to be straight out in front of the bows. The problem with that arrangement is that the structure of the ship would then act to block the wind from the 'chutes. Finally, if there's enough wind to pull the ship at a constant speed, wouldn't it be easier to jury-rig a wind turbine or two to generate electricity? hydrodynamic resistance is still significantly lower than dry-land resistance, at low velocities. as for fouling, once inflated, a parachute behaves as a semirigid body. as long as there are no streamers to get tangled together, the main bodies, risers, and shrouds will not become entangled unless you force them into each other. also, a wind shift that will dump the kites is incredibly unlikely, and would typically only happen in inclement weather. and keep in mind that I do have experience with flying parachutes as kites. steering IS a challenge - without sailing specific hulls, your arc is significantly reduced, and with the kites all anchored forward of the midpoint, you are not going to have a strong lee helm - but in the scene they were happy to be running with the wind, so control would be an advanced test. as for flying position, it is not that significant - angle of attack is more important than alignment with the wind, and with a good length of line, wind shadow is almost irrelevant. as I already said, a static kite will not pull as efficiently as a dynamically controlled kite in the "power zone" but with enough sail area, it becomes a moot point, anyway. and if they had the hardware to build a wind turbine, it would be more effective in generating power - but the show implied they did not have a wind turbine kit on board, while they did have parachutes. (which I did not see if they said WHY a ship without aircraft had parachutes.)
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Post by Lokifan on Jul 19, 2014 17:22:45 GMT
Actually, they had a line in the show about the lab being in "one of their helicopter bays", implying that they had multiple helicopters at some time.
There was also a scene in a previous episode where I thought they raced their assault crew to Gitmo via helicopter, but I may be wrong; I was only half watching it at the time.
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Post by Cybermortis on Jul 19, 2014 20:23:32 GMT
I was watching the show "The Last Ship" a few nights ago. The plot was that the engines failed on an Arleigh Burke destroyer--a pretty big US Navy ship--because they essentially lost all their cooling water. They needed to get electricity to a lab onboard or vital research would be destroyed, as well as make headway to a nearby island for fresh water to cool the engine (and keep the crew alive). They did this by launching three parachutes tied to the bow of the ship. The wind pulled the parachutes like kites, and the ship was pulled along at 3-4 knots. Pulling the ship spun the propeller, and they drove the ship's generator from the propeller's shaft, giving them enough power to run the critical lab. Myths are: 1) Can parachutes pull a destroyer? 2) Can a spinning a propeller on a ship like this drive a generator? I'm thinking no, that there wouldn't be enough power in the "kites" to move the ship, but then again...the ship IS massive but the ocean is about as frictionless as you could hope for. Keeping the "kites" from fouling each other would also seem problematic. I rather like this idea. Of course MB is not likely to be allowed to try this with a real USN Destroyer, so they'll probably have to settle for a smaller scale test as a proof of concept. I'd also suspect that generating power angle is something that they couldn't, or at least wouldn't be allowed to, test. The reason is that a lot would depend on the design of the engine of the ship, which is likely to be classified information - or at least not something the USN would want aired on an international TV show. The IIA version has two enclosed hangers for ASW helicopters. This would also mean that the ship would displace some 9,200 tons.
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Post by Lokifan on Jul 19, 2014 20:59:49 GMT
The Flight 1 version, although not listed as having aircraft, did have aircraft equipment listed on the reference I used. Frankly I don't see how need LAMPS III electronics if you don't have a helicopter. www.globalsecurity.org/military/systems/ship/ddg-51-specs.htmI've probably got it wrong and it's a small issue, but I'd appreciate someone more knowledgeable than me figuring it out. EDIT: Okay, I found a picture of a Burke Flight 1 with a helo deck: fas.org/man/dod-101/sys/ship/ddg-51.htm My guess is that it has the capability to support helocopters, but it's not considered "part of the ship". It's probably only equipped with a helicopter for certain missions as needed.
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Post by Cybermortis on Jul 19, 2014 22:40:45 GMT
The type I had a landing pad, which would allow quick and easy movement of personal and supplies to the ship as well as allowing the Marines on board to be deployed as part of a larger force if needed. What it lacked was the ability to store helicopters anywhere but on the landing pad, which is not ideal for the helicopter.
At the time the original ships were being designed and built this was not considered a problem, as the ships were most likely intended to be deployed as part of a carrier's escort group. As the cold war started to thaw it would have become clear that the needs of the navy were switching from large scale carrier deployments to less concentrated patrol missions with individual ships - which was far more cost effective.
Patrol missions by individual ships work best when those ships act as mobile bases for smaller craft, which do most of the actual work. Historically such missions have been carried out by the ships boats*, but helicopters can cover far more ground more quickly and have greater versatility. So it would have been decided that giving the ships the ability to carry helicopters of their own, rather than reply on larger ships, made sense. It also makes sense when looking at the escort role for carrier groups, as you end up with considerably more assets you can put into the area without overstretching the capabilities of the big ships or relying on them to the extent that if something prevents them from being able to launch aircraft you are screwed - the 'not putting all your eggs in one basket' principle.
We tend to forget that ships are designed for the roles that are needed for predicted to be needed for the navy at the time. But going from design to finished ship takes years**, usually a decade or so, and the needs of the Navy can change significantly in that time. These days designers tend to design ships with more internal space than they actually need, on the principle that the extra space can be used for new systems or features which allows the design to be modified with limited problems and hence remain in service for decades. It is also one of the reasons the old Battleships were phased out - their design makes modifying them far more expensive than is practical.
(*Most cutting out and patrol duties carried out by the Royal Navy during the Napoleonic wars were done with the ships boats, not the ship itself. In fact it was rare for the ship to actually be involved in stopping merchant ships (to check papers or press men) themselves, and often they would never even see the ship that was stopped.)
(**Even in the 1800's it would take 18-24 months or more to build a 36 or 38 gun frigate...and this was in the middle of a war and using 'shortcuts' to building (such as using fir for planking rather than oak). Although modern tools mean we can work a lot faster, the ships we are building are a hell of a lot larger - A heavy frigate circa 1812 would displace 1,800 - 2,200 tons. Or put another way a single Arleigh Burke displaces four and a half heavy frigates circa 1812 or two and a half HMS Victory's. So we can build faster, but have more to build...and that is not including the need to build all the equipment that goes into modern ships)
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Post by silverdragon on Aug 6, 2014 7:39:26 GMT
Some thoughts... maybe a bit random, but maybe some ideas...
Can a Chute pull a ship?... yes. Speed, not much. Its all Relative.... Depends on the wind, and how big the sail is. And yes, we are talking sails here, because the principal is the same isnt it?...
Spinning a propeller to make sparks.... plausible.. but again, speed dependant.
If you are in a force nine, yes, maybe you have a certain speed. But in a force nine, you would have other problems..... Like keeping the weather on the outside......
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Post by wvengineer on Aug 6, 2014 12:46:54 GMT
My first thought it why does this ship not have a backup generator? While my experience with modern ships is very limited, I have been through a couple in my time. The ones I saw had backup generators that typically ran off diesel. This way they could generate power if their main engine(s) were out of service for whatever reason.
The next question I have is on reverse powering of the drive train system.
I have seen a couple different system designs. First one the ship will have multiple turbines to take steam power to multiple propellers. In this, the generator has it own steam supply and turbine. Here there is no mechanical connection between the generator and the prop shaft, so there is no way to get power from one to the other. No need to touch on the gearing issues.
The other way is to have a single turbine that generate rotational power from the steam supply. This turbine is attached to a large gear reduction system to gear the high speed low-torque power of the turbine to the low speed-high torque of the prop. There are some PTO ports at various points in the gear train to provide power to various ship systems at the speed an torque they need. In this case, to get the reverse power they want, you would have to provide enough power to turn over EVERYTHING in the gear train. This included the props, shafts, gearbox, generator, and turbine since the turbine is hard connected to the gearbox, and anything else connected to the system. This would require some massive input torque from the prop(s) to overcome the huge inertia of everything in the system. Think it take a lot of work to push start a car? Nothing compared to this. I can't see 3-4 knots being able to produce enough torque to get everything moving.
Of course, my final question is why does this ship not have water to make steam? Every ship I have been on from WWII battleship to sub to modern heavy transport have on board water purifier systems. How can they run out of steam water when they are surrounded an inexhaustible supply of water and they have the equipment on board to make as much as needed to replace water they loose.
Yeah, yeah, I know is a Micheal Bay product. Physics and logic need not apply.
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Post by Cybermortis on Aug 6, 2014 13:33:44 GMT
Could you create a homopolar generator of some sort using the rotation of the prop shaft?
You might not have magnets on a ship, but you would have a lot of metal cabling and presumably batteries that you could use to create an electromagnet.
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Post by silverdragon on Aug 8, 2014 8:36:41 GMT
Just a thought. Propeller on ship, big thing pokes through waterproof hole in ship, spins fast, one end has blades outside, other end has basic forward/reverse and then big-as-a-truck Engine..... Just where do you isolate the engine to make a turbine from an alternator or swap the engine for the generator kind of thing?... This isnt plug-n-play parts, you cant just take away the drag by a non working engine to pass power to the generator without a LOT of work.
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Post by watcher56 on Aug 8, 2014 16:58:12 GMT
Shift into neutral? The dialog suggested that there was an alternator driven directly from the prop shaft. You really need to disconnect from reality to enjoy most of the newer TV shows and movies.
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Post by the light works on Aug 9, 2014 2:40:44 GMT
Shift into neutral? The dialog suggested that there was an alternator driven directly from the prop shaft. You really need to disconnect from reality to enjoy most of the newer TV shows and movies. I.E. turbine turns a generator, motors turn the prop shafts. simpler drivetrain with less inertia. - like a railroad locomotive.
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Post by tom1b on Aug 10, 2014 1:22:57 GMT
Is The Last Ship’s USS Nathan James Based on a Real Ship?"Are parachute style kite sails really used to pull ships? Yes. On The Last Ship TV show, crew members of the USS Nathan James fire three parachutes into the air, which deploy and begin to pull the ship. The concept is based on a real technology that debuted in 2008 as a way for modern steel ships to harness wind power and in turn cut down on fuel consumption. The episode simplifies the launching process of the kite sails (they’re not fired into the air out of handheld guns) and exaggerates the number of sails (normally just one). The sky sail is also controlled and monitored by a complicated computer system and is designed to assist a working engine, rather than make up for a non-functioning one." It includes a video of the SkySails system being used. These end of the world virus series/movies are just stupid. Ebola has a fatality rate of 90%. If the entire planet became infected with ebola, the survivors are the ones with the immunity system to kill it. Those are the ones are the ones you want to survive. They haven't even eradicated the common cold. But Hollywood, and sadly the American public, always get it wrong when it comes to viral diseases. On the power generating side: The Arleigh Burke class destroyer is equipped with 3 Allison AG9140 Generators for electricity and 4 General Electric LM2500-30 gas turbines for propulsion, so losing the propulsion system would have no impact on power generation and moving the propeller wouldn't generate electricity. Most US Navy ships have generators in addition to a propulsion system. The planned Zumwalt class destroyer will have 2 Rolls Royce engines for propulsion and 2 for power generation. Kidd class (predecessor of Arleigh Burke class) had 3 engines for propulsion and 2 for electricity. The nuclear ships have steam turbines for propulsion and other steam turbines for electricity. The Nimitz class carrier has 4 turbines for propulsion and 8 for electricity.
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