- #36
DrStupid
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- 502
russ_watters said:I'm not sure that difference mattered much to the passengers of the Hindenburg
I think it does. 62 of the 97 persons on board survived. I wouldn't expect that in case of an explosion.
russ_watters said:I'm not sure that difference mattered much to the passengers of the Hindenburg
That is assuming current use. If LEO satellites are to be replaced by balloons as i suggested, and a lot of companies is going to make global wireless internet networks like starlink using balloons that will massively increase the number of balloons in the air by orders of magnitude compared to today's use.Vanadium 50 said:First is that balloons (primarily weather balloons) are a major consumer of helium. As I said, the National Academies estimates 7% of helium is lifting. Party balloons make up most of this, so that leaves at most a 3% fraction. If one is concerned about reducing helium use, there is at most 3% to be gained here.
Perry, hydrogen is finite only insofar as all resources are finite by definition. The limitation in the hydrogen resource would probably first come from complaints by owners of formerly beach-front property as their property values decreased. Upside: reduced flood insurance costs.Vanadium 50 said:"Helium is a finite resource". So is hydrogen.
I am not sure. There is an obvious problem: altitude control. For example, after an airship unloads a heavy load, it needs to take ballast to avoid having too much buoyancy. Releasing helium after each flight is expensive. There are some solutions to the problem (see, e.g., http://aeroscraft.com/technology-copy/4580412172), but they are not simple. With a vacuum aircraft, one can just admit air to decrease buoyancy.Vanadium 50 said:Vacuum airships are a not-even-a-solution looking for a problem.
So maybe the market is small because current lighter-than-air aircraft have a lot of problems.Vanadium 50 said:There is a market for about two dozen airships in the world.
It is possible that there will never be a business case for vacuum aircraft, but it is not obvious so far.Vanadium 50 said:Making them orders of magnitude more expensive to get at most 30% more lift - and we have not accomplished that - is a non-starter.
Business can ignore vacuum airships until you can build a toy vacuum airship, or a prototype.akhmeteli said:It is possible that there will never be a business case for vacuum aircraft, but it is not obvious so far.
Baluncore said:Business can ignore vacuum airships until you can build a toy vacuum airship, or a prototype.
To do that you need a low mass truss, or some other structure to oppose the vacuum implosion.
You will have credibility when you can demonstrate a solution to that structural problem.
There are other ways available now to practically solve all your hypothetical problems.akhmeteli said:I just noted that there are indeed problems that vacuum aircraft could solve. If you disagree, I would like to hear your arguments.
What is hypothetical about the problems that I mentioned? So yes, there are other ways to solve them, and no, there is no vacuum aircraft. I just insisted that there are indeed problems that vacuum aircraft could help solve.Baluncore said:There are other ways available now to practically solve all your hypothetical problems.
There is no vacuum aircraft available to magically solve those hypothetical problems.
I don't think you heard what @Vanadium 50 said. You're talking about engineering (and maybe environmental) problems, but he's talking about economics problems. I understand that you are an aspiring inventor, but even if you succeed in inventing a functional vacuum airship, you still have to solve someone's economic/environmental problem in order to sell it. There has to be a market for the product. So when the time comes, you'll need to be able to show that your solution costs less than a traditional helium balloon or that the cost premium is worth the environmental savings. Right now, you seem to be completely ignoring the cost/market issue.akhmeteli said:I am not sure. There is an obvious problem: altitude control.
It may not be obvious to you, but it seems obvious to several of us. But here's the thing: the burden of proof is entirely on your side whereas the criteria/demands of proof are entirely on ours (or that of prospective investors). We can tell you what we think it will take and you'll have to provide that. Or not -- it seems you've been working on this for a long time and haven't gotten far.It is possible that there will never be a business case for vacuum aircraft, but it is not obvious so far.
some bloke said:Vacuum airships are a scifi idea where you evacuate the air out of a chamber to achieve lighter-than-air lift.
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I'm wondering it would be feasible to use multiple layers of wall, with steadily increasing pressures inside, to prevent it from buckling under the strain.
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Add another layer at 10psi and you have 3 walls, each only taking 5psi, but with a vacuum on the inside. I don't know whether this would be any lighter than just making the chamber strong enough to withstand 15psi, but that's beside the point.
My question is - would this work? can you stagger the pressures via sequential containers? or am I missing something?
(emphasis added)DrStupid said:... Of course you can stagger the pressures via sequential containers. That's out of question. However, it doesn't help you. Three containers that withstand 5 psi are as heavy as a single container that withstands 15 psi. ...
gmax137 said:Has anyone challenged @DrStupid 's contention in post #2?
Great stuff, thanks. By comparison, the Hindenberg class airships were 135ft in diameter, 800 feet long (equivalent 500ft pure cylinder), 7.1 million cubic feet and had a cargo capacity of 22,000 lb. That's a structure weight of 481,000 lb and hydrogen weight of 40,000 lb for a displacement of 543,000 lb of air. Or per square foot, (pure cylinder), that's 0.96 lb of structure. So if they held a vacuum they could carry almost triple the cargo. But...they would have to hold a vacuum. Buoyed by helium they'd need to shed 12,000 lb to get airborne.jrmichler said:The absolute maximum weight of one square foot of the vacuum structure that withstands the above forces is 1.9 lbs. The structure must not buckle. The structure needs attachments for crew, cargo, engines, fuel, control surfaces, mooring, etc.
In practice, the airship structure must weigh about half that much, or about 1 lb per square foot, in order to carry crew, cargo, engines, fuel, control surfaces, mooring, etc. Any person who proposes a vacuum airship needs to do these calculations, and show a solution using commercially available materials
Vanadium 50 wrote: " Vacuum airships are a not-even-a-solution looking for a problem. "russ_watters said:I don't think you heard what @Vanadium 50 said. You're talking about engineering (and maybe environmental) problems, but he's talking about economics problems.
Let us assume for a moment that I indeed ignore the issues of economics. Would that be such a mortal sin? I believe a prototype vacuum balloon will have significant scientific and cultural value and would be of interest for millions. You can find dozens discussions at various forums, where people ask if a vacuum balloon is feasible. People want to know that. There have been at least three popular articles on vacuum balloons over the last year (at New Scientist, Science & Vie, and salon.com). Again, some work on vacuum balloons is being made at Los Alamos, NASA, Air Force Institute of Technologies (I gave references in my post #42 in this thread). Let me add that a vacuum balloon would also be the first lighter-than air solid.russ_watters said:I understand that you are an aspiring inventor, but even if you succeed in inventing a functional vacuum airship, you still have to solve someone's economic/environmental problem in order to sell it. There has to be a market for the product. So when the time comes, you'll need to be able to show that your solution costs less than a traditional helium balloon or that the cost premium is worth the environmental savings. Right now, you seem to be completely ignoring the cost/market issue.
I am not sure it makes much sense to compare a prototype vacuum balloon with a prototype of a run-of-the-mill invention. A prototype vacuum balloon would be a major breakthrough.russ_watters said:I suggest watching the TV show "Shark Tank" to see how inventors fare on it. One important thing to note: they pretty much always have a working prototype and a pending patent before pitching their ideas to investors. But that's not enough: they need to prove they are solving a market problem.
I don't quite understand that. In my post I referred exactly to this solution of "pumping the helium back into a pressurized tank". I wrote: " There are some solutions to the problem (see, e.g., http://aeroscraft.com/technology-copy/4580412172), but they are not simple." Let me note that pressure vessels bring their own share of problems.russ_watters said:That said, I think you are downplaying the engineering benefits as well, by basically ignoring completely how the existing solutions work. For the sake of your own business model and the potential time/energy/money wasted in pursuing an idea that really isn't likely to go anywhere, you need to take an honest look at both sides of this. On the engineering side, I can't understand why you wouldn't consider pumping the helium back into a pressurized tank to be a solution to the engineering/environmental problem of wasted helium and airship storage. It seems really obvious. On the other side, since that is obvious but isn't apparently common, maybe that's because ballast is cheap and easy? I suppose you can say that a vacuum balloon with a pump and valves for ballast control is "a solution" to this technical problem, but other solutions clearly exist and I don't see a reason to believe the vacuum balloon would be a cheaper solution (back to the economic problem) -- because ultimately that's what matters most here.
I respectfully disagree about the burden of proof. We are on Physics Forums, not in an investors' office. Not being sure vacuum balloons are hopeless business-wise is not against the rules of Physics Forums, unless you tell me otherwise:-) What's obvious for you is not necessarily obvious for everybody. And again, it may well be that you are right. I am just not sure at the moment.russ_watters said:It may not be obvious to you, but it seems obvious to several of us. But here's the thing: the burden of proof is entirely on your side whereas the criteria/demands of proof are entirely on ours (or that of prospective investors). We can tell you what we think it will take and you'll have to provide that. Or not -- it seems you've been working on this for a long time and haven't gotten far.
I cannot build a prototype. Building a prototype would be a major breakthrough. And I agree, our finite-element analysis (FEA) does not prove that a vacuum balloon is technically possible. "FEA does not eliminate the need for prototypes, but it can shorten the process.” (https://www.asme.org/topics-resources/content/fea-and-the-question-of-credibility)russ_watters said:Step 1: Build a functioning prototype to prove it is actually technically possible. And no, your arxiv paper and patent application are not sufficient as such proof. Even if all the math is right in your paper, it isn't enough.
We wrote an article (https://arxiv.org/abs/1903.05171) showing that a vacuum balloon can be made using currently available materials. The design was verified for strength and buckling using finite-element analysis. We also cite designs of vacuum balloons by others.jrmichler said:Any person who proposes a vacuum airship needs to do these calculations, and show a solution using commercially available materials
Er, well...it was the next sentence:akhmeteli said:Vanadium 50 wrote: " Vacuum airships are a not-even-a-solution looking for a problem. "
What did I not hear? He did not mention economics until later.
Vanadium 50 said:There is a market for about two dozen airships in the world.
Broadly, nothing -- what's wrong happens when you get specific. When you try to invent a new thing or method for doing something, the specific details are what matters.akhmeteili said:So I mentioned some problems a vacuum aircraft could solve. What's wrong with that?
This is a good example of a specific issue, but without numbers it is just handwaving. You say it is economically impractical, yet this is how it is currently done, so clearly your claim that it is economically impractical is false. Since ultimately your goal is to bring a vacuum airship to market, you need to know the numbers to prove how your idea would be better than what is currently done: how much helium does a helium airship lose per flight or month or year and how much does that cost? How much would your idea save (taking into account the energy use of the pumps)?And let me note that the problems I mentioned have an obvious economics aspect. For example, if we could release helium each time, we would not have a problem with altitude control, but it is economically impractical.
I'd rather not. If you can show your idea is possible, that would be cool, but to bring it to market is all about the economics. It's boring, but it is what matters. Yes, that makes it a mortal sin.Let us assume for a moment that I indeed ignore the issues of economics. Would that be such a mortal sin?
Ok. Prove it.I believe a prototype vacuum balloon will have significant scientific and cultural value and would be of interest for millions.
It was interesting to millions insofar as it was free entertainment. Cool. But that's not what you are after, is it? You want to eventually sell this as a commercial product, right?Let me give you an example. A few years ago some people made a human-powered helicopter (https://en.wikipedia.org/wiki/Human-powered_helicopter). I suspect it has no business potential, but it was a breakthrough, it was interesting for millions.
Who cares? Answer: Investors -- that's who cares. You have to be trying to sell this idea to someone, right?I am not sure it makes much sense to compare a prototype vacuum balloon with a prototype of a run-of-the-mill invention. A prototype vacuum balloon would be a major breakthrough.
That first quote is from me, and you didn't state the issue in your post (even if it was mentioned in the link). Regardless, you need a way to prove to investors that your idea is better. To me, there is no obvious reason why an air vacuum pump should be superior to a helium pump.I don't quite understand that. In my post I referred exactly to this solution of "pumping the helium back into a pressurized tank". I wrote: " There are some solutions to the problem (see, e.g., http://aeroscraft.com/technology-copy/4580412172), but they are not simple." Let me note that pressure vessels bring their own share of problems.
This current discussion is yours to direct as you wish. What is your ultimate goal? If we say, "yep, your idea will work" what have you won? We, the audience have no stake in this game, so winning or losing means nothing to us. If you want us to prove you wrong and we don't, what happens next? Answer: nothing. And that's not what you want, right?I respectfully disagree about the burden of proof. We are on Physics Forums, not in an investors' office.
That's unfortunate. Without it, your idea will go nowhere. Do you even know what is required to build a prototype? Specifically? Do you have a written proposal for the next step?I cannot build a prototype. Building a prototype would be a major breakthrough.
It's a good point: helium balloons are basically altitude agnostic, up to the point where they are fully inflated. A vacuum ballon's lifting capability decreases rapidly as altitude increases.Baluncore said:@jrmichler
Your computations are for sea level. Some things scale sensibly.
I think the idea of using an unmanned vacuum airship at 60,000 feet for mobile phone and internet connectivity is an interesting model. The air pressure at that altitude is only about 1 psi. The airship structure therefore need only counter a 1 psi differential envelope pressure. But the volume must be sufficient to lift the gross weight.
I would say, it was in the next paragraph:-) So it was not obvious the first phrase was about economics. And I answered to his "market" paragraph separately.russ_watters said:Er, well...it was the next sentence:
I have not heard about airships releasing helium for altitude control. I don't think it is done on a large scale.russ_watters said:This is a good example of a specific issue, but without numbers it is just handwaving. You say it is economically impractical, yet this is how it is currently done, so clearly your claim that it is economically impractical is false. Since ultimately your goal is to bring a vacuum airship to market, you need to know the numbers to prove how your idea would be better than what is currently done: how much helium does a helium airship lose per flight or month or year and how much does that cost? How much would your idea save (taking into account the energy use of the pumps)?
Well, different people have different goals.russ_watters said:I'd rather not. If you can show your idea is possible, that would be cool, but to bring it to market is all about the economics. It's boring, but it is what matters. Yes, that makes it a mortal sin.
I provided some arguments, but if you don't believe that " a prototype vacuum balloon will have significant scientific and cultural value" , it's fine with me.russ_watters said:Ok. Prove it.
No, I want to see a prototype vacuum balloon in my lifetime. I don't see it as a source of income for me. Actually, I spent quite a bit of money on it:-)russ_watters said:It was interesting to millions insofar as it was free entertainment. Cool. But that's not what you are after, is it? You want to eventually sell this as a commercial product, right?
I do want to "sell" the idea, but not as a money-making idea at this point. And I believe the idea does "sell" to some extent. As far as I know, our work was the first to show that a light enough structure made of currently available materials can have sufficient strength and stability to buckling. Nowadays, theoretical and experimental work on vacuum balloons is being done in several places, and almost everybody cites our work.russ_watters said:Who cares? Answer: Investors -- that's who cares. You have to be trying to sell this idea to someone, right?
And the second quote ( " There are some solutions to the problem (see, e.g., http://aeroscraft.com/technology-copy/4580412172), but they are not simple." ) was mine, not yours:-), and the link is about pressurizing helium.russ_watters said:That first quote is from me, not you. Regardless, you need a way to prove to investors that your idea is better.
As I wrote to you, I don't expect any significant impact from my posts here. I just thought that the posts may be interesting for some people, as the participants of this thread seem to have some interest in vacuum balloons. So my "goals" here are very limited.russ_watters said:This current discussion is yours to direct as you wish. What is your ultimate goal? If we say, "yep, your idea will work" what have you won? We, the audience have no stake in this game, so winning or losing means nothing to us. If you want us to prove you wrong and we don't, what happens next? Answer: nothing. And that's not what you want, right?
Yes, I know what is required. The structure is quite simple conceptually: it is a sandwich spherical shell containing two ceramic face skins and an aluminum honeycomb core between them. The ceramic skins are the most problematic part. For a small prototype (say, 5 meter diameter), the face skins are very thin and difficult (but not impossible) to manufacture. Standard technologies can be used to manufacture ceramic skins for a bigger prototype (say, 50 m diameter), but the large size brings its own share of problems.russ_watters said:That's unfortunate. Without it, your idea will go nowhere. Do you even know what is required to build a prototype? Specifically?
You are correct.jrmichler said:A very quick ball park estimate convinced me that the mass of the pressurization air is significant, probably enough to make this concept impractical.
Thank you for looking at our paper. I don't see why we should not have referenced our patent application. Yes, USPTO rejected the application as they believed that Armstrong's invention destroys novelty of our application. However, Armstrong did not even say that the walls of what looks like a honeycomb in their pictures can be under compression. It looks like they are under tension in their design. What's worse, Armstrong does not have any calculations of strength, let alone buckling, so one just cannot build a light enough and strong enough structure following their invention (I guess Armstrong's first name Lavanda is a female name, but I am not sure).jrmichler said:I looked at your arxiv paper. I note that you reference your patent application 11/517915, even though it was rejected because of prior art US Patent #1,390,745 by Armstrong. The Armstrong patent issued September 13,1921.
I don't think Barton's design is feasible without using at least some lighter-than-air gas. If I remember correctly, he admitted that much somewhere, but I am not sure.jrmichler said:Your paper also references US Patent 7,708,161 by Barton, which uses a series of pressurized chambers so as to use material in tension, and thus avoid the buckling problem. On a quick reading of the Barton patent, I did not see any mention of the mass of the air in the pressurized chambers. A very quick ball park estimate convinced me that the mass of the pressurization air is significant, probably enough to make this concept impractical.
We were aware of Metlen's work, but we did not intend to offer a comprehensive bibliography. That work is a thesis by a Palazotto's student. We did reference some representative work by Palazotto and his associates.jrmichler said:Your references missed the MS Thesis by Metlen, titled Design of a Lighter Than Air Vehicle That Achieves Positive Buoyancy Using a Vacuum, June 2012. Link: https://apps.dtic.mil/dtic/tr/fulltext/u2/a587008.pdf.
I agree. We showed that theoretically it is possible, so I don't doubt that it will be done one day. I would not bet on or against its practicality though.jrmichler said:It appears that a lighter than air vehicle using vacuum is possible. Practical, however, is a different matter.
We all wonder things like that.Stormer said:I wonder if it can be done if it can even compete with LEO satellites.
I don't feel kickstarter is the way to go right now, although I may be mistaken. Other people tried and failed to raise funds for a vacuum balloon at kickstarter.Vanadium 50 said:If a prototype vacuum balloon will interest millions, why not do a kickstarter and make one? I suspect the interest is broad, or deep, but not both.
Of course, absolute vacuum is not needed. I think very rough vacuum (say, 1% of atmospheric density) would be enough. It will not affect lift much.Vanadium 50 said:Also consider this: will the vacuum inside be absolute? Better than in space? Of course not - it would cost billions to get that last nanogram of lift. What we really mean is that there is less air on the inside than on the outside. But we already have balloons that do this: hot air balloons. So this is really a question of whether the operating point is right: is high lift, high cost better than low lift, low cost?
Vacuum balloons will have their strong and weak points, different from those of helium and hot-air balloons, so maybe they will have their niches. It's difficult to predict their future now. It will probably depend on the specific technology.Vanadium 50 said:The market for non-party balloons is pretty much concentrated at the low-lift low-cost end. There are about 10,000 hot air balloons and 1000 weather balloons (with an increasing fraction using hydrogen). The argument is that there are huge new markets on the other end of this continuum.
If you cannot demonstrate a vacuum balloon with positive lift at sea level, with a 14.6 psi external pressure, how are you going to increase that performance over fourteen times, to lift in the 1 psi pressure expected at 60,000 feet? Without that advance it cannot become a substitute for LEO satellites.akhmeteli said:It's difficult to predict their future now. It will probably depend on the specific technology.
1% at sea level is not much, but at 60k feet the pressure is 1 psi = 6.8% of SL.akhmeteli said:Of course, absolute vacuum is not needed. I think very rough vacuum (say, 1% of atmospheric density) would be enough. It will not affect lift much.
So 10 knot wind provides a pressure of 0.5 rho v^2=17 Pa, according to my calculation (I used air density rho=1.29 kg m^-3). This figure seems to agree with information at https://www.engineeringtoolbox.com/wind-load-d_1775.html . However a vacuum balloon withstands atmospheric pressure of about 10^5 Pa. So it does not look like this kind of wind would be dangerous for a vacuum balloon.Baluncore said:I expect someone will build a vacuum novelty that can hover near sea level inside a big sheltered building, just to prove it can be done. I wonder if one could survive the impact of a 10 knot gust of wind without imploding.
Gusts of wind and wind shear do not act symmetrically, so they induce a bending moment in the structure. That is quite different to atmospheric pressure which is applied equally over the entire surface area.akhmeteli said:So it does not look like this kind of wind would be dangerous for a vacuum balloon.
In that post I was not replying to you or to Stormer, but to Vanadium 50, so I did not have in mind high altitude balloons or substitutes for LEO satellites.Baluncore said:If you cannot demonstrate a vacuum balloon with positive lift at sea level, with a 14.6 psi external pressure, how are you going to increase that performance over fourteen times, to lift in the 1 psi pressure expected at 60,000 feet? Without that advance it cannot become a substitute for LEO satellites.
Your concept of commuting between the surface and operating altitude with the same structure is fascinating, but fabulous.
Again, I considered "sea-level" balloons. If one needs a vacuum balloon for 60000 feet, the vacuum should be, say, 15 times better than 1%. It is still rough vacuum.Baluncore said:1% at sea level is not much, but at 60k feet the pressure is 1 psi = 6.8% of SL.
That same 1% at 60k feet reduces the differential pressure from 6.8% to 5.8%.
Still, what I calculated is four orders of magnitude less than the atmospheric pressure. If you believe the factors you mention change the situation dramatically, I would like to see your calculation.Baluncore said:Gusts of wind and wind shear do not act symmetrically, so they induce a bending moment in the structure. That is quite different to atmospheric pressure which is applied equally over the entire surface area.
When you build a 6-balloon it will contain air, not vacuum. It must be supported during construction. The hangar will need to support the rigid airframe during construction. When it is evacuated, it will "lift off" inside the shed, be disconnected from the suspension, and then move out onto the field.akhmeteli said:Let us imagine now that one has a 6-balloon and needs to deploy it at 60000 feet. One can, say, fill it with air to prevent crushing by sea-level atmospheric pressure and gradually move it upwards (say, by heating the air inside) and gradually bleeding out air. This approach is not easy, but not quite "fabulous".
If it is to be used as a satellite in a global network then does drag really matter much? Can it not then just drift with the wind only doing small maneuvers and let other satellites take over when it drifts away from a ground station and towards another?Baluncore said:Fat and short cylinders will be more resistant to bending collapse, but will have greater drag when travelling.