Slashdot Mirror
Fuelless Flight with Air Submarine?
An anonymous reader writes "Using the same physics principles as submarines, a new company is planning a fuelless air ship. Recent advances in ultra light and strong materials are making this concept a practical reality." There's no question that changes in buoyancy can be used to propel a vehicle, but "fuelless" is going to be tricky.
I don't know about you... it looks kewl, but I'll be damned if I'm gonna fly on that thing. Personally, I trust engines, fuel, etc.
Isn't that what the sci-fi writers of the 1940s/1950s thought the future would be like? After all, the Empire State Building has a blimp port at the top. I'll stick with good old ozone layer killing cars, thank you.
Wouldn't something in the air be a Supermarine?
Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.
Fuelless falling.
Using the same physics principles as submarines, a new company is planning a fuelless air ship.
Isn't a fuelless air submarine usually called a "balloon"?
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
It's a little creepy that this website looks like this other famous site and that they both advocate leaving the earth for a long trip in a high-tech airship. Coincidence?
HIV Crosses Species Barrier... into Muppets
All the same, it's still a cool idea. I want a small one to fly to work in (maybe add pedals for all the compression-> decompression stuff and you'll have a human powered plane ;)
Looks can be deceiving. Or CAN they?
The pontoons will be multiple layers of Kevlar and epoxy, which weigh as little as 1 lb/ft2, around a rigid carbon-fiber airframe
I've heard that there's a really bad problem from lightning strikes if you plane isn't made from an excellent conductor like metal. Various attempts have been made to make non-metal composites that don't get badly damaged by a strike. If this plan goes really high then this will be a problem.
Can some engineer tell me, have they solved this problem or is this idea just hot air?
Like all pain, suffering is a signal that something isn't right
However, just because it may not use fuel to continue on it's journey doesn't mean it didn't need some power to get it started...
Physics 101. Law of thermodymanics. Etcetera.
This issue is a bit more complicated than you think.
Like a lot of hot air.
Well, in any case, you might want to get an Immortality Device before you board one of these things.
Did you know you can fertilize your lawn with used motor oil?
To save on the compressed air, just fill me full of mexican food, and I could provide a cheap source of propulsion. Or we can outsource that to Mumbai.
Oh, the backup engine is there alright. We just neglected to carry fuel for it onboard :D
Because you never know when you might run out of air up there!
You know... there's another name for flying without fuel. Its called skydiving!
The only thing necessary for Micro$oft to triumph is for a few good programmers to do nothing". North County Computers
In the even of a water landing your seat cushions may be used as a floatation device.
"Have you ever thought about just turning off the TV, sitting down with your kids, and hitting them?"
Well this PhD smells a quack (from the link on the page http://www.fuellessflight.com/techno/tech.htm):
"We humans can rarely invent any process that nature does not already use. Most of the science we know today merely copies nature. Our thermodynamic laws were formed by observation of nature. They are not proven, merely not disproved. Within this section of our website you will be taught a new science that mimics the earth's weather, by harnessing the dual forces of gravity -- buoyancy and gravity acceleration. Harnessing gravity may be more technically described as the science of harnessing mass differentials. High density mass falls within a low density lifting fluid, like rain falls from the sky, and low density mass rises in a high density lifting fluid, like a bubble rises in water or helium rises in air."
I think I understand the technology he is proposing (I'm confident it still requires input energy, beyond the environment), but he really should tone down the quack-o-meter. I think we can rest easily that the thermodynamic laws are intact.
-Sean
This thing is supposed to fly because of a combination of reduced bouyancy (by way of creating multiple vacuum's inside it) and stored energy (by way of a turbine invented by the apparent author).
The turbine is for compressing air, to be used as power storage. I think.
If your craft is dependant on creating a vacuum inside for easy lift, but your power supply is compressed air, don't the two kinda cancel eachother out?
Even if you made it and got it up, what would it be like to try to control a zero-weight plane with mass? I picture it flipping around in the wind like a feather...
The aircraft, still in development, will be similar to a submarine that changes its buoyancy, a form of gravity, to float on the surface of the sea or cruise 300 ft below it.
Stephen J. Mraz, "Senior Editor," is in need of a severe beating. Since when is buoyancy "a form of gravity?"
I stopped reading there. Nothing bothers me more than shitty pseudoscience.
According the the white paper on the "Technology" link:
.0755 pounds per cubic foot lifting capacity for air).
The gravityplane must be very large in order to be lifted by a lighter-than-air lifting gas such as helium that provides a very low amount of lift, thus a small gravityplane can never be built and models of the craft will always be very large. However, a scale model of the gravityplane can be built as a sea glider that is less than 30 foot long that will be capable of holding four passengers. The sea glider can work in water at this small size, because water has a lifting capacity 821 times greater than the lifting capacity of air (62 pounds per cubic foot lifting capacity for water and
If at 30 feet a gravityplane can hold 4 passengers, could this design ever provide a viable means of transport for larger groups of people?
30 feet/4 people = 7.5 feet/person
Thats approx 75 feet per group of 10. Makes for quite a large plane for even medium sized groups.
For cargo I suppose this could be cost effective depending on the maintenance costs and its lifetime. Lets assume that an average person weighs 200lbs (I know it may be too large, but to allow for an optimistic view of the plane's carying capacity).
7.5feet/200lbs ~= 1foot/26lbs
May be good for cargo because shape, size and conditions don't really matter.
Nope.
Much older.
Carl Sagan, Robert Heinlein, Ray Bradbury, and a number of other scientists and writers were inspired by "The Martian Tales of Edgar Rice Burroughs". The first one, "A Princess of Mars" was published in 1912. (And it's on Project Gutenberg!).
In these books, John Carter was mysteriously transported to Mars, which was called Barsoom by the inhabitants. He became the Prince of Helium (a city/city-state -- not the element). The Barsoomian navies had huge airships that were held in the air by use of the 9th (or 8th?) light ray, so they needed no power to stay aloft. (According to Burroughs, we only know of 7 rays of sunlight, as seen in a rainbow, from red to violet, but Barsoomian scientists had isolated 2 other colors, never seen on Earth, and one of these colors is what gave light a repulsive power so it was repulsed from objects and reflected to our eyes, and it was used to keep the Barsoom airships in the air.)
The Martian Tales are far-fetched, but a ripping good time to read (at least the 1st 10 are -- skip the last one).
When I first read the story, all I could think about were E.R.B.'s descriptions of the huge naval vessels floating through the air of a dead planet (there were no sea going navies, since there were no seas, except one at the south pole).
Too bad these stories seem all but forgotten now.
A continuous external feed of energy could, in theory, cause a craft to continue to operate without carrying any fuel. Perhaps one could capture energy from a large radiant light source. If only there were such a thing somewhere near the Earth...
However, if one were using efficient solar cells, one might expect such a ship to be black on the top. The inverted-orca coloring pictured would reflect too much light. Service to Seattle may be erratic, but you'd never have to worry about being forced to take a red-eye.
But, you know, this particular one reeks of vaporware. Ignore them until they demonstrate something useful and allow independent observers to examine it. Move along.
While it's possible to convert altitude into momentum, the energy harvested by doing this won't get you back to the same height. If the wind is gusty, it could be possible to pick up a bit of energy, but nowhere near enough to power a useful transportation vehicle. A possible exception: they could have a special way of harnessing energy from vomiting passengers...
That reminds me of the old joke back in the Navy... I think it went: There are more airplanes in the oceans than submarines in the sky.
I guess that's no longer true. :-)
The aircraft, still in development, will be similar to a submarine that changes its buoyancy, a form of gravity, to float on the surface of the sea or cruise 300 ft below it.
What's scarrier, flying without an engine, or that the general public won't think twice about this sentence?
In this house, we OBEY the laws of thermodynamics!
you need energy.
That would be the helium in this case. You could argues that it takes energy to build the thing, during which contained energy would be loaded via fuel powered vihicals, but thats a little overly semantical.
I mean, I can fill a ballon with helium, and it will rise without power.
The Kruger Dunning explains most post on
Even if you ignore the fuel needed to pump the helium in and out of the storage, they will need the power to propel the "gravy"-plane forward
They don't plan on pumping the helium in and out. It looks like they plan on leaving the helium static in the tanks, and pumping air in and out of other tanks, making the plane weigh more and less. However, it's not really the weight of the plane that matters, it's the density. The goal is to get the average density of all the materials onboard i.e. the people, instruments, seats, structure, tanks, etc to be less than the density of the air around it. This is where I think they will have problems.
Anyone familar with aviation or the atmosphere knows that the atmosphere gets much less dense as you go up. Here in Columbus, altitude 1,000 feet, the density of air is 1.2 kg/m^3 At 10,000 feet the density is 0.88 kg/m^3 and at 30,000 feet it is 0.41 kg/m^3. This plane would have to have an average density less than those values to reach those altitudes, and keep in mind that simply having the cabin pressurized for humans will make the entire cabin a bubble of "heavy" air.
The energy to pressurize air will come from a wind powered turbine which will be deployed when the plane is descending, but I don't know how much power they expect to get from this. Any power produced by this turbine would affect the plane in the form of drag, which decreases speed and range. This would have to be a very flexible air storage system, since the requirements would change every day depending on high and low pressure systems, temperature, and the weight of whoever is on board.
They may also have stability and control issues. I assume that this would have to be a large plane, even with today's light weight materials. Just look at how big blimps have to be to carry their minimal cargo. A plane like this with huge wingspan and extreme buoyancy would be affected by every gust of wind and bit of turbulence that affected it, and although it could be very stable, control inputs would have to combat huge wind loads, and control effectiveness would be marginal, to say the least.
From my armchair view of this project, it seems possible on a small scale, but not to the point of carrying "massive loads" of people and cargo as the website claims.
My $0.02
I checked out the site and checked the "technology" page. They kept going on about the opposite effects of gravity - and didn't seem to be talking about dark energy or anything. So we get to the explaination - _bouyancy_ is gravity's alternate effect? WTF? If I recall, the only thing bouyancy and Archimedes have in common is the phrase 'specific gravity'.
It appears they just plan to do what hawks and eagles to every day and ride the thermals. Great idea, but thier marketing sucks, like thier trying to get big money from people who are clueless.
BK
"None of us are as dumb as all of us." - meeting mantra
In the year 2000... we will all fly in little vehicles that don't require fuel and can skip over rush hour traffic. Except rush hour traffic will be up in the air, and we'll have to drive in a car to avoid it... Unless, there's still people who drive below the flyers... or, or...
[head explodes]
Ignoring the possibility that these scientists might have to wait for a different set of physical laws before this craft becomes viable, are we to understand that this thingmarine will operate in a constant dive/climb cycle? The cost to fly it could be cheap, but the cleanup costs after a passenger flight would be astronomical. Anti-emetic anyone?
Tumbleweed.
next!
"You worthless post!"
-Shakespeare, 2 Gentlemen of Verona, 1. 1. 147
No - it's not a scam nor perpetual motion machine. A company has already built submarines on this principle that are being used as autonomous research drones. Here's announcment about the Slocum Glider. Here's a couple of action shots of it being deployed. My advice would be to talk a couple of college physics courses to undertand how BUOYANCY works.
Granted it's more complicated in air (larger because air is so dilute when compared with water) however with advances in composite materials, it is certainly doable.
Thalasar
When I first read the story, all I could think about were E.R.B.'s descriptions of the huge naval vessels floating through the air of a dead planet
I really don't want to sound like an Anime Fanboy here, but you might like to check out Last Exile if you haven't already seen it. It's a decent little series with some really impressive graphics, built around exactly that kind of concept...
3 more engines.
This plane (if possable) would have a very high glide ratio, so even if it crashes, unless it's a catastrophic failure, it could be a very soft crash landing.
To me this sounds like some intresting scifi, from a wild imagination, but not very well thought out. I'm shure that there will be something like this eventually, but most likeley not too soon.
The vehicle is really just a durigable with wings, I think that lighter than air flight has a potential to be come a really big thing in the next century, and that that is the angle to push, not the fuel-less flight aspect. Imagine taking an air cruise.
Well art is art isn't it, but then again water is water; and east is east; and west is west; and if you take cranberries
The idea that an airplane can fly endlessly carrying heavy loads of passengers and cargo without burning any fuel
So far so good.
The new hybrid "gravity-powered aircraft"
Starting to get bogus.
is formed by merging the capabilities of the following devices into a single new aircraft apparatus:
(1) an aircraft capable of aerostatic (lighter-than-air) lift to gain altitude; and,
Still OK.
(2) a glider aircraft capable of aerodynamic lift, having a high glide ratio to accomplish long range gliding; and,
Starting to get bogus.
("Glider"? Using diving planes to add a significant forward component to upward/downward motion is well understood. But a "glider" is something else - a high-speed device with significant aerodynamic lift - initially powered by atmospheric thermal energy in the form of updrafts storing energy by raising a NON-bouyant craft against gravity, then trading this stored energy for momentum as necessary by gliding downward. Raising a neutrally-bouyant object stores no energy.)
(3) a (patented, new design of Robert D Hunt) wind turbine that is capable of harnessing the force of wind to generate power as the aircraft glides downward. This cycle can be repeated indefinitely to allow the craft to stay aloft virtually forever.
Bingo! Perpetual motion.
You CAN get a lot of forward motion out of lift-driven vertical motion. But it takes ENERGY to adjust the lift. The submarines described in the original Slashdot posting are one example. Zepplins with diving planes that achieved speeds in excess of 200 MPH by this mechanism also existed in the mid 20th century.
But the Zepplins BURNED FUEL to change their bouyancy (by heating some of their bouyancy gas), just as the submarines use energy to compress or expand gas in their bouyancy tanks. This makes them a heat engine (though a slowly cycling one) and subject to the carnot cycle limit.
This craft proposes to use a turbine to collect energy from the wind of its passage and use that to adjust its bouyancy, use the bouyancy to produce forward motion, creating the wind to drive the turbine. Like a generator with its shaft connected to a motor which is also wired to its output, the energy goes around and around, with some being lost in every pass.
This is not to say it won't fly at all. But to the extent that it DOES fly it's getting its basic power from vertical air currents, just like any other glider. By being nearly neutrally bouyant it sacrificed the ability to store energy in the gravitational potential of its own weight at altitude, and it's replacing that by being able to convert the wind of its passage to stored electricity, then feed that back into forward motion via bouyancy adjustments rather than propulsive fans.
But I expect this to be more expensive and less efficient than other alternatives - such as an equivalent modification to the original 200-MPH zepplins WITHOUT the fixed wings.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Honestly, after reading this site, it smacks of all the hype around the Segway (and many similar, less-successful "revolutionary breakthrough" schemes).
Yes, it is possible to create a fuel-less aeroplane that can still maintain forward motion. Advanced glider technology certainly fits this description. However, there are a couple of things that are missing from the adware:
The physics of underwater motion are similar those of flight - basic fluid dynamics here. The problem is he's ignoring fundamental environmental differences between water and air. The density differences between the two make it possible to move large masses underwater, but only tiny masses in the air using the same principles. Not to mention that the fluid consistency and motion between air and water are radically different, which invalidates using the ocean as a model for the sky.
He's a fraud. Pure and simple.
-Erik
There are always four sides to every story: your side, their side, the truth, and what really happened.
You're forgetting that lift capacity goes by the cubic footage of the lifting body, not the length.
I'm too lazy to do the math, but a longer body would have a far larger volume in the lifting body than liner.
7.5 ft per person on a 30ft version != 75ft for 10 ppl.
"You worthless post!"
-Shakespeare, 2 Gentlemen of Verona, 1. 1. 147
Loosing power on only one side is not a picnic even. The remaining engines will have to push harder to maintain speed but this makes the entire aircraft want to turn constantly. Very few runways come in corners.
Gliders on the other hand are designed to ehm well glide. This thing would never suffer an engine failure. Power system (it does have one) fail? Simply glide gently down giving you a far wider range in wich to find a suitable landing splot.
There are many reasons this can fail but worries about safety because of a lack of engines ain't one of them . Note that it isn't a balloon. With wings that size it could exchange hight for speed and with that control over its direction.
MMO Quests are like orgasms:
You may solo them, I prefer them in a group.
Not quite. The idea is to use a large area of vacuum to provide normal lift. Then a second ballast tank can be adjusted will cause the thing to decend. When it decending, it uses the forward energy to spin the turbines which then powers the compressors. The steady state of this thing will be floating at 100,000 ft or so.
I think it can work if they can solve the "magical box that can hold a total vacuum that weighs less than the air its going to displace" part of the problem but thats been know about since the days of Boyl and Dalton.
This system uses the energy of the wather system to move around a device that wants to float at a n altitude above ground level. In that way its much like a sail boat. The reality is if anyone can build a large vacuum chamber, they can stick engines on it and get from LA to London much quicker than current jets if they can get up high enough. I figure this will happen about the time someone finds the right stuff to make a space elevator out of.
John McPhee wrote an incredible book called "The Deltoid Pumpkin Seed" about the Aeron company, which designed an aircraft that would combine airship technology with a lifting-body style airplane, where the entire body of the plane provides lift. This was a serious design, with no pseudo-science factor. However, the original design (the Aeron 3) was exactly the one described in this post. It was a two-hulled, helium-filled aircraft that would use wings to turn buoyant lift into forward motion. The whole idea was the dream of a christian missionary and pilot who wanted a craft that could deliver bibles and tractors to the third world at minimal cost. The Aeron 3 was destroyed on the ground by high winds before its first test flight. The company didn't bother to rebuild it after they hired some real engineers and hit on the lifting body idea.
Bridge, in Brooklynn, used and in good condition.
$500,000.00. neg.
I accept PayPal.
i have a better idea for the gravitational device. A toast with jam tied to the back of a cat....
ok that wasnt that funny. So im NOT the joker.
"The quality of life is inversely proportional to the number of keys on your keyring."
I'm not a physics major, I'm a math major, so someone correct me, please, if I'm wrong, but isn't this just yet another take on perpetual motion? Doesn't this proposal violate a couple laws of thermodynamics? And wouldn't this whole deal take some *serious* advances in materials engineering?
I'd be curious to hear if anyone in any of the fields of physics, materials sciences, or aviation would like to offer why this is bordering on revolutionary brilliance, or why this is a totally unmitigated crock of sh--.
Peace.
Chr0m0Dr0m!C
Yes, I remembered that book from years back, as soon as I saw the article. Interestingly, Aereon Corporation is still in business after all these years. Check it. . .
http://www.aereoncorp.com/
The page about the Aereon III is especially interesting.
These ships were based on the theory that a lighter-than-air craft could "glide" upwards, then vent some gas and glide downward, then drop some ballast and glide upward again, and continue in this manner until it ran out of gas or ballast. It's all about using aerodynamics to translate the up-and-down movements into horizontal motion. It's not a perpetual motion machine.
A nifty and clever idea, but one of dubious practicality.
Since buoyancy is caused by gravity pulling the fluid (air/water) around you toward the earth and you moving away from the earth to take its place. "Form of gravity" is probably a less accurate term than "effect of gravity." Still, Stephen J. Mraz was right, you're wrong. How about that severe beating?
Nothing bothers me more than shitty pseudoscience.
Be careful when you deride things you don't understand. This isn't new technology. It's been in use in autonomous submarines for years. Employing the same principles in the air hasn't been done yet because it's a bit more complicated: The speeds are a lot higher, the weather becomes a factor, and the margin for error is a lot smaller.
"With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea...."
RFC 1925
The work required to pump all the air out of the ship to make it buoyant and rise to some height is more than the work required to just lift the ship that distance. Drag and any forward kinetic energy given to the plane implies that the energy recovered by the turbines during fall is not sufficient to pump all the air out of the ship again to once again make it rise, thus you will have to carry along fuel to run an engine to drive the pump that changes your buoyancy. If you use external power to evacuate the buoyancy chambers on the ground, then it can be said that the pressure differential represent stored energy. As the ship rises, gas pressure potential energy is traded for gravitational potential energy (altitude) and kinetic energy (forward motion).... So both the compressed helium and the evacuated chamber represent stored energy which must be loaded onto the ship while on the ground, thus this ship requires fuel like any other ship. Not only this but the inefficiencies in recovering kinetic and gravitational potential energy demand that the ship carry much more stored energy that that required to lift the ship through one up and down cycle.... So you may not hear the phrase "filler up" that the air park, but "emptier out" if effectively the same thing DN
In order to recover all of that energy you must transfer ALL of it back into the compression of the hydrogen. This is impossible as there are NO 100% efficient "wind turbines" to recover that energy.
Forget about the fact that the plane glides forward - that's just smoke and mirrors. Look at the simpler case where the "plane" falls straight down and doesn't glide at all then ask yourself if it can recover the energy required to get it back to its original altitude. Obviously it can't.
I've made up my mind and now I've got to lie in it.
The structural requirements of a vacuum are much greater than helium. The entire structure goes into compression and bending when in a vacuum, meaning it will need to be extremely strong in order to resist bending. This is a bit like sucking the air out of a 2 liter pop bottle, it will collapse easily, and the pop bottle will need to be substituted with a steel canteen in order to keep its form. Unfortunately, this kind of structure is heavy, and in terms of air ships are extremely inneficient.
A regular blimp inflates, so the forces on the skin are entirely in tension, the only bending forces are caused by loads the ship is carrying and more importantly, sudden wind gusts which could tear a weak ship apart. Structurally speaking, this is vastly more efficient and completely eliminates bending due to a vacuum, and the tensile force alone in the skin is often enough to provide a stiff but flexible frame, just like a ballon once inflated keeps its shape even under tremendous strain. It is a very resiliant structure.
There are two huge problems that have always existed with airships, and fuel is not one of them. The first problem is landing the craft. They have a tendency to blow around with even slight gusts of wind, and if anything happens like a downdraft, they can get smashed into the ground. The second problem is weather related. In violent weather, the thin skin on these ships can get torn easily. The larger the craft, generally speaking, the bigger the problems. This is not to say these problems are inherently unsolvable, but why bother using zero fuel when fuel already will cost next to nothing if it uses solar power or fuel cells.
WWII subs are not a good example because they didn't dive very deep, and they were diesel powered, meaning they couldn't stay submerged very long on battery before they were forced to surface to run their engines.
:). In particular "hover mode" cycles a shitload of water per second (that's the highly specific non-classified term for you). The purpose is to create a very stable platform for launching weapons, missiles, whatever, with no forward motion.
Modern nuclear subs actually do put a lot of power into buoyancy adjustments, and yes that's the correct spelling
Without either forward motion, or hover tanks, standard buoyancy adjustments would not keep the ship stable and it would tend to tilt one way or another, especially after launching its payload.
Standard buoyancy adjustments aren't nearly as power intensive, but they are used more often than in WWII, since subs now dive very deep and may have to adjust for thermal layers and other ocean / weather events.
The plane adjustments are used differently depending on the desired effect. The stern planes adjust the orientation of the ship, while the bow planes allow you to move up and down without tilting much. This is important with subs nowadays because of their sheer length. One degree of tilt could put you at 7-10 feet of difference from bow to stern, which is a big deal when you're at periscope depth and don't want to breach.
The design this appears to be a "high" pressure balloon. Nasa is currently researching ultra long duration balloons.i ndex.shtml
:(
http://www.wff.nasa.gov/~code820/uldb/
During the day the sun will heats the helium causing it to expand and the craft floats upward.
During the night the helium cools causing it to contract and the craft falls downwards.
The whole thing looks too heavy to even get off the ground.
These things aren't necessarily for humans to ride in. Wouldn't it be cool to have these things carrying electronics for various purposes? I think that there are already proposals to use derigibles for cell-phone base stations (or whatever they're cslled).
Is a sailboat a perpetual motion machine? Is a windmill a perpetual motion machine? This ship could sail in 3 dimensions and draw power from a turbine. Theoretically, that is possible. Althoug it does need some additional power, hard tack and beans possibly.
But what I don't understand is why he doesn't just create a giant inflatable airplane hybrid, that would probably work better. It could get 90% lift from helium and 10% from forward movement from a turbo fans powered by solar power. The helium ballon aspect of it could be the structural system as well, it would be an active system (inflatable), rather than a very heavy and expensive rigid frame.
I'm skeptical of information provided on web pages featuring starry backgrounds and bright blue text. It reminds me of UFO Abduction websites, Black Helicopter Life Cycle websites, and Heaven's Gate.
The flag just makes more sense than the constitution. - Judas Gutenberg
The inherent problem with airships is that the huge surface area combined with low weight means they get blown around easily and handle badly. Adding wings doesn't help. It's been tried. Adding power does help. Adding steerable power helps even more.
For an idea of what a successful modern lighter-than-air craft looks like, see Zeppelin Luftschifftechnik GmbH, which has built several large rigid airships in the last few years. But even with carbon fibre and Kevlar, the load capacity is small.
just as the submarines use energy to compress or expand gas in their bouyancy tanks. This makes them a heat engine (though a slowly cycling one) and subject to the carnot cycle limit.
Actually, as long as you compress and expand gas adiabatically, then the Carnot cycle is irrelevant.
Obviously you cannot make an engine that works in this way, because the point of an engine is (1) to do net work or (2) to cause a heat transfer. So the efficiency of any engine cycle has a Carnot limit.
But the process you have described need not be an engine. In fact, this should be completely obvious. Since there is no net work being done, and no heat transfer, how on earth can you even define an thermodynamic efficiency for the cycle?
And you don't even need to get this complicated. (Slow) compression and expansion of an isolated volume of a gas is reversible and adiabatic. Hence it is isentropic.
This is complete bull! There is no way for this thing to "to stay aloft virtually forever" without some sort of external energy input. Entropy 101.
On a side note, does anyone know how stinking cold it is at 50,000 ft. I don't know for certain but I'm sure is a really small number (in K of course). The heat loss from such a ship must be significant at these elevations. Does anyone know how these folks propose to keep their passengers from freezing? They can't always fly in the sun; they will need some sort of energy source to keep the temperatures at levels suitable for human existence. No, their magical compressors won't be able to do much about this
>To be safe they re-ran the numbers three times to be absolutely, positively sure the refuelers hadn't made any mistakes; each time using 1.77 pounds/liter as the specific gravity factor. This was the factor written on the refueler's slip and used on all of the other planes in Air Canada's fleet. The factor the refuelers and the crew should have used on the brand new, all-metric 767 was .8 kg/liter of kerosene.
Lessons: a triple-check doesn't help you if there's a systematic error. Standardized measurements are a Good Thing.
>the EICAS issued a sharp bong--indicating the complete and total loss of both engines. Says Quintal "It's a sound that Bob and I had never heard before. It's not in the simulator."
Lesson: in a safety-critical system, train the users for "impossible" situations.
>Hydraulic pressure was falling fast and the plane's controls were quickly becoming inoperative. But the engineers at Boeing had foreseen even this most unlikely of scenarios and provided one last failsafethe RAT.
Lesson: when your engineers go paranoid, if there are lives at stake then for God's sake listen to them. "Belt and suspenders" engineering saved lives in this incident.
>Quintal "got busy" in the manuals looking for procedures for dealing with the loss of both engines. There were none..
Lesson: learn from experience. There have been incidents, like volcanic ash injection, that have forced shutdowns of all engines on a jetliner. If your statistics say the engines can't fail at the same time, and the graybeards say they can, then you left something out of the statistics.
>The avoidance of disaster was credited to Capt. Pearson's "Knowledge of gliding which he applied in an emergency situation to the landing of one of the most sophisticated aircraft ever built."
Lesson: there is no substitute for a wealth of experience. Downsize your 20-year veterans to save money, watch things go wrong.
Sorry for the diversion, but these are things I'm passionate about.
(I got my nick from "The Moon is a Harsh Mistress"
Funny once, Mike.
1. To change bouyance you will have to expend energy somehow.
2. It will be SLOW!!!
3. It will be huge and very dangerous in high winds. Super light and strong composits or not there are limits and this thing would be at the ragged edge.
4. For what? It will be super slow and trains, barges, and ships are very good at moving heavy loads over long distances at slow speeds.
5. No one will fund it. Not only would you have to build this thing but you would have to setup air fields for it. It will not mesh well at the current airports.
One of those great PopSci pipedreams like flying cars.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
Mr. Hunt describes it convincingly. Buoyancy is caused by the differing force with which gravity pulls on heavy and light things. Gravity pulls with more force on heavier things, (F=MA; mass is higher), and less on lighter things. Hence, the heavier thing sinks relative to the lighter thing. Buoyancy.
Not that anyone ever actually follows a link and reads what is there, but I recommend that all the "non-believers" here take a look at Seaglider.
Or follow this google search for even more.
Seaglider applies much the same principles as this vehicle but to an underwater environment. It has a small onboard power supply, but it alternately uses gravity and bouyancy to propel itself.
I may not be an Aerospace Engineer but I am an Ocean Engineer and Fluid Dynamics in air is the same as Fluid Dynamics in water. Just change your value for rho.
Just call it an airship and be done with it.
I'm sure some of you are breaking out your ideal gas law to see if this is a perpetual motion machine. However, please take this into account: buoyant acceleration is actually = g*(m-md)/(m+md) where m is the mass of the buoyant object and md is the mass of the diplaced gas.
It's pretty clear to me that the designer of this aircraft not only took some physics in college, but also actually studied the textbook and did the problem sets. And there lies the problem. I'm convinced that (s)he did a few too many of those problems that start out: "Disregarding air resistance, find the..." or "Ignoring the effects of friction, calculate...."
Perhaps first year physics texts should come with a shrink wrap EULA that states something along the lines of: "The scenarios presented in this book do not accurately represent reality."
Airships are the size of cruise liners, but the reason for that is that the lifting capacity of an airship increases with volume, i.e. x^3. You can get round about 1kg of lifting capacity from 1m^3 of helium.
It's also a rigid ship, the gas bags are inside a rigid frame. The frame used to be aluminium but they'd use carbon fibre these days. Buoyancy bladders are not a particularly big hurdle.
It's all technically possible but I'm not convinced it'd be what you could call quick.
Government of the people, by corporate executives, for corporate profits.
This isn't a typo, but just a plain old mistake by our illustrious Dr. Hunt:
"A conventional glider is towed to fairly high altitude by an airplane or is launched by a tow wench."
That must be one really big mama. The "Attack of the Forty Foot Woman" comes to mind.
Oh, maybe he meant "winch".
Three reasons: wind, weather, and airship structure.
The wind can be brutal at higher altitutdes, that's where the jet stream is.
And the weather has all sorts of things like rain, high and low air pressure, hail, lightning, hurricanes, typhoons, and worst of all, other aircraft speeding around.
I've read the website. While it seems logical, an airship twice the size of a 747 built like they describe makes me wonder about rigidity and strength and weight.
My only other concern was it seems the cockpit is between the pods and has lousy visibility. But, that's me...
It my be the second most common element in the universe but we have a hard time getting it. Helium is mined from limited reserves and like fossil fuels takes millions of years to be produced. For this to actually be reusable (for years to come) it has to use vacuum, or dare I say it, hydrogen. Hydrogen is easy to get hold off and only dangerous when mixed with oxygen. It also has much better lift. But I suppose I shouldn't complain when someone puts forward an idea for clean flight AND gets some attention.
One thing that everyone keeps forgetting is drag / weight / size. The type of equipment that this guy is talking about is going to take up a lot of space. Usually things that take up space weight something. Things that also take up space require energy to move them through the air. His only form of propulsion is gliding / compressed air, but gliders are usually extremely aerodynamic vehicles with a high glide ratio. Drag and the weight of the aircraft are directly related to such a ratio. So in theory, the super marine would go up, glide a foot, and then have to repeat. Not to mention maneuverability. Highly impractical.
Sounds a little like Tom Swift's Paraplane (which used an external gasbag) from Tom Swift and His Electronic Retroscope, Grossett & Dunlap, 1959.
Aside from perpmo in general, using stored compressed air to power the compressors to gather more compressed air? That was iterated at least twice. The Engineer in me would not tolerate a second audition for an exact count of banal pseudo-scientific nuggets...that one is a deal killer all by itself.
"If no one tilts at windmills, the damn things will take over the world!"- christian simpleman
It'll be slow if you are really going "fuelless".
In which case you'd be competing against trains, ships and airships.
Doesn't really matter tho. They're looking for stupid investors- take the money, make an "honest attempt", and walk away.
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Heck a wind powered blimp would sound even more convincing - just hang an adjustable sail/keel/rotorsail (like gyrocopter) a few hundred feet down, and you could do some sailing, this assumes of course that the winds a few hundred feet down are different enough from the winds above.
Add a windmill or two to get power for miscellaneous stuff for the blimp - assuming different winds at windmill altitude from blimp altitude. Still solar power could be more effective.
Nice idea, but crap physics. Here's why:
From chemistry and Avogadro's Law, the weight of one mole of a substance is the same as the atomic weight of that molecule, and has a volume of 22.4 liters at standard pressure and temperature (0C and 29.92 inches). So, for 78% N2 (28), 21% O2, and 1% H2O (32), air weighs about 1.28 kg/m3, or almost exactly 1kg per cubic yard. The same yd3 of Helium (2) would weigh only 68 grams. So a cubic yard of helium displacing air provides 932 grams of lift. (The mass != weight quibble isn't really relevant here, OK?)
Allowing the airship to have the same volume of the USS Akron, 6.5 million ft3 is 224 tonnes (metric) of air displaced by 16.4 tonnes of He, so the maximum potential lift is 208 tonnes.
Now the problems start.
Blimps use balonets to allow for helium expansion with heating and especially altitutde changes. For a maximum altitude of 10,000 feet (700mb), the blimp must allow for 30% expansion (1000mb at surface to 700mb at altitude) if it doesn't want to vent helium. Zepplins and other airships handled this through flexible bags containing the helium/hydrogen.
The movie in the article's website said their airship would rise some 10 miles before floating back down. Ten miles is 50,000 feet, or about 100mb. This requirement limits the on-ground volume of helium to only 10% of all available to allow for expansion. Thus the maximum lift would fall 208 tonnes to only 20.8 tonnes.
Okay, how about only five miles/25,000 feet? Pressure there is about 350mb, so you can only start with 35% helium volume, or 72.8 tonnes possible lift.
Now, somebody explain how to build a 6.5 million ft3 volume container for less than 20 tonnes (or 70 tonnes) that can be pressurized, as stated in the movie, to compress the Helium enough to start descent. Oh, not to mention the pressure tanks and multi-kilowatt vertical turbine to electically power the flyweight air pumps filling those tanks. The paint on the hull would weigh more than the cargo.
This might work on a planet like Jupiter, where the air pressure is around 10,000mb and more the deeper you go, but until somebody comes up with aluminum-strength aerogel, I think this plan is crap.
Pacifist paratroopers yell, "Ghandi!" when they jump.
On the 10th of February 1972, in New Scientist magazine, Daedalus proposed a similar scheme, using ammonia as the working fluid:
"... one might think, a balloon filled with ammonia would rise rapidly to 25,000 feet, and then lose lift by the liquefaction of its gas."
"... overcome this by putting his ammonia in a somewhat elastic balloon which will always squeeze it to about 0.1 atmospheres greater pressure than the atmosphere outside. This will raise its condensation-point sufficiently for the ammonia to liquefy at about 34,000 feet."
It seems that someone has been taking Daedalus seriously, but when they did the math, they found that the ammonia was a bit troublesome, and they now seek to do without it.
You can read a copy of the original Daedalus column in "The Inventions of Daedalus: A Compendium of Plausible Schemes" by David E.H. Jones, W.H. Freeman & Co 1982. ISBN 0-7167-1412-4.
Regards.
Six boxes to use in the defense of liberty: letter, soap, ballot, witness, jury, ammo.