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  1. - Top - End - #91
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    Default Re: Airships as public transport Yay or nay?

    Could there be political reasons for deterring airplanes in this world? What if there were a war in the setting's past in which airplanes were used to catastrophic effect? Supersonic bombers were used to carpet bomb cities into rubble and were too difficult to intercept. After the war, the resulting peace treaty forbade the development of large airplanes for fear that they could be converted into bombers in anticipation of another war. Airships, on the other hand, are much easier to intercept and are seen as less of a threat.

    It's a bit of a contrivance but I think it's plausible. Depends on how the politics of your setting work, though.

  2. - Top - End - #92
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    Default Re: Airships as public transport Yay or nay?

    Quote Originally Posted by Berserk Mecha View Post
    Could there be political reasons for deterring airplanes in this world? What if there were a war in the setting's past in which airplanes were used to catastrophic effect? Supersonic bombers were used to carpet bomb cities into rubble and were too difficult to intercept. After the war, the resulting peace treaty forbade the development of large airplanes for fear that they could be converted into bombers in anticipation of another war. Airships, on the other hand, are much easier to intercept and are seen as less of a threat.
    I think that's an idea that certainly has merit.

    I've heard comments about the Gatling-gun, dynamite, airplanes, and the atom-bomb saying, more or less, that each one would be such a terrible weapon that it would bring about the end of war because no one would want to endure the horror of it. So far only the nukes have even come close, not in that they end wars but that governments are extremely reluctant to deploy them. Still it shows that the sentiment is there.
    Also, post WWI several of the peace-treaties limited the size of warships, and not only for Germany and it's allies. They broke down eventually, but if something like that delayed the delopment of HtAA until ABZs where already established, it might mean there's cultural or political inertia to maintain the existing system.
    Last edited by Deepbluediver; 2018-03-13 at 08:21 PM.
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  3. - Top - End - #93
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    Default Re: Airships as public transport Yay or nay?

    NPR's Science Friday is discussing living on Mars today (2018-03-16), and one of their subjects is a Martian Airship. Haven't got that far in the discussion yet, but it should be interesting.

    Edit: Their plan is for a vacuum-filled octahedral truss surrounded by a thin membrane for the lift balloon.
    Last edited by Lord Torath; 2018-03-16 at 02:43 PM.
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  4. - Top - End - #94
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    Default Re: Airships as public transport Yay or nay?

    Cold fusion could make airchips more viable. IIRC many forms would produce helium as a byproduct; hydrogen into helium seems to be the most basic fusion reaction. (and while hydrogen can also be used to float a balloon helium is safer because it's a noble gas and won't burn in oxygen (I'm not sure whether it will burn in chlorine trifluoride but I'm willing to wager it won't even burn in then) whereas hydrogen burns quite readily
    Last edited by Bohandas; 2018-03-18 at 01:52 AM.
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  5. - Top - End - #95
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    Default Re: Airships as public transport Yay or nay?

    Quote Originally Posted by Bohandas View Post
    Cold fusion could make airchips more viable. IIRC many forms would produce helium as a byproduct; hydrogen into helium seems to be the most basic fusion reaction. (and while hydrogen can also be used to float a balloon helium is safer because it's a noble gas and won't burn in oxygen (I'm not sure whether it will burn in chlorine trifluoride but I'm willing to wager it won't even burn in then) whereas hydrogen burns quite readily
    Interesting point but it really doesn't change too much. The safety issues with hydrogen are real, but they're not nearly as much of a technical challenge as they are a psychological/policy hurdle. The main, real, challenges that others have brought up are the theoretical limits of lift per volume (an issue that would be mitigated by using hydrogen instead of denser helium) and that it's actually very, very hard to keep a lighter than air craft stable in turbulent winds and to efficiently move it where you want to go at a decent pace.

    In terms of real-life viability, I simply don't see it happening given the current state of technology and the current relevant research. I can only see two plausible ways for it to happen, and if we neglect the possibility that steam-punk loving hipsters suddenly have a drastic increase in discretionary income, then the most likely path to widespread use would begin with some technological development that makes it economically viable for airships to take some business away from barges in the "we have to get a lot of heavy materials from point A to point B, and we care a lot more about cost than we do about how long it takes to get there" industry. While we, as people and as governments, tend to care a great deal about upper middle class folks falling to their deaths from a burning zeppelin, we tend to care a lot less about working class folks doing jobs that the vast majority of us don't have to do, and would not choose to do given our economic circumstances. Hydrogen won't be a deal breaker--particularly if it's cheaper and beater than helium, which it is--because, to be blunt, we collectively care less about professional sky sailors than we do about folks taking a pleasure-cruise that we could see ourselves taking. We've demonstrated this time and time again with coal miners, commercial fisherman, construction workers, oil men, and for that matter, the conventional sailors currently working the freighters and barges doing the same sort of work that an airship might hypothetically do.

    If anything, mastering fusion would make airships even less economically viable. The chief advantage of airships air in efficiency and cost at lower speeds. Due to how drag works, lighter than air craft have huge technical hurdles when it comes to achieving very high speeds--hurdles that can't be entirely surmounted by pumping large amounts of energy into the system. However, if we had cold fusion, electricity would be cheaper, which likely means that planes and boats would be cheaper to run, either because we develop better batteries and cheap electric planes and ships running off cheap nuclear power, or because the obsolescence of fossil fuels for electrical power generation would make them cheaper as a source of aviation fuel.

  6. - Top - End - #96
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    Default Re: Airships as public transport Yay or nay?

    Quote Originally Posted by Bohandas View Post
    Cold fusion could make airchips more viable. IIRC many forms would produce helium as a byproduct; hydrogen into helium seems to be the most basic fusion reaction. (and while hydrogen can also be used to float a balloon helium is safer because it's a noble gas and won't burn in oxygen (I'm not sure whether it will burn in chlorine trifluoride but I'm willing to wager it won't even burn in then) whereas hydrogen burns quite readily
    Well, sort off...

    Quote Originally Posted by Lvl 2 Expert View Post
    Instead of restating the reasons I think zeppelins were always a bit of a long shot (I prefer ekranoplans if we have to travel weird anyway) I decided to calculate if nuclear fusion could contribute significant amounts of helium. The energy density of deuterium used for fusion (presumably turned into helium, the page doesn't quite specify) is around 4 million MJ/L. A cubic meter of helium can be used to lift roughly a kilogram of mass off the ground. So that's 1000 liters. Assuming we can make an airship where the ship weights half of the load it can take in passengers and freight, and assuming 70kg standard humans each with 30kg of clothing, luggage and inflight meals, an airship made for 100 passengers would weight around 15,000kg when full, thus requiring around 15,000m^3 or 15 million liters of helium. 15 million times 4 million is 60 trillion MJ or 60EJ (exajoule, 10^18 joule) of energy produced in the process of making that much helium (more if you can start from regular hydrogen, but we're disregarding that for now).

    How much is that, 60 exajoules? Well, roughly the yearly energy consumption of South Korea, or one tenth of the yearly energy consumption of the US. That means this is actually sort of feasible, assuming most of our energy would come from fusion, the number of airships stays small (think more private jet, less vacation liner) and we don't develop a shortage of helium due to other applications, like needing a lot of it for medical scans and electron microscopes or something. Under ideal circumstances and assuming no losses during operation the US could float 10 large airships a year using waste products of nuclear fusion.
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  7. - Top - End - #97

    Default Re: Airships as public transport Yay or nay?

    Quote Originally Posted by Berserk Mecha View Post
    Could there be political reasons for deterring airplanes in this world? What if there were a war in the setting's past in which airplanes were used to catastrophic effect? Supersonic bombers were used to carpet bomb cities into rubble and were too difficult to intercept. After the war, the resulting peace treaty forbade the development of large airplanes for fear that they could be converted into bombers in anticipation of another war. Airships, on the other hand, are much easier to intercept and are seen as less of a threat.

    It's a bit of a contrivance but I think it's plausible. Depends on how the politics of your setting work, though.
    Actually, you probably don't even need to go that far. WWII reshaped the environment because of how much money was spent on aviation research--the U.S. alone spent about 1.5 trillion in current dollars. All you need to change is that instead of being stampeded into giving the money away, the government sticks to the original plan to issue low interest loans. The airplane industry ends the war with significant debt rather than cash flush, and probably without government funded civilian use plants ready to go.

    The change in momentum should give you what you need to keep using LTA craft.

    Also, the uses of LTA craft currently are focusing on their ability to loiter in a small area--serving as a mothership for drones in search and rescue, for example. Overhead command centers for disaster relief. Or just an aerial cell tower--they were going to try that in Puerto Rico last year, but it didn't happen (I don't think I ever heard why).

  8. - Top - End - #98
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    Default Re: Airships as public transport Yay or nay?

    Quote Originally Posted by Rockphed View Post
    In the US, a short plane trip can have about 2/3rds of its time tied up in the airport between loading the plane, getting through security, and unloading the plane. A train, however, has significantly less bottle necking. On the other hand, a plane from Detroit to Chicago takes less than an hour of flight time but 6 hours on the train.
    Or about 4.5 hours by car. And when you get there... you have a car.

    Whereas taking a plane involves driving to the airport, parking, hiking through the terminal, finding your gate, checking in, being subjected to guilty-until-innocent and potentially invasive & humiliating screening, being herded onto the aircraft, being crammed in with strangers cattle-style, and so on... only go get off the plane and wait around for luggage they may well have sent to another country. Ends up taking about as long as driving that distance, and then you don't have any way to get around once you're actually out of the airport.

    I doubt people would endure that experience to take an LTA passenger craft.
    Last edited by Max_Killjoy; 2018-03-29 at 08:34 PM.
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  9. - Top - End - #99
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    Default Re: Airships as public transport Yay or nay?

    Noticed this thread and haven't read through all the way... but I have wondered in a scifi or fantasy setting if a vacuum airship might be useful. Without the downsides of containing a gas, it seems like it could be a cheap alternative to airplanes for stuff that doesn't need to arrive as quickly.
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  10. - Top - End - #100
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    Default Re: Airships as public transport Yay or nay?

    Quote Originally Posted by Togath View Post
    Noticed this thread and haven't read through all the way... but I have wondered in a scifi or fantasy setting if a vacuum airship might be useful. Without the downsides of containing a gas, it seems like it could be a cheap alternative to airplanes for stuff that doesn't need to arrive as quickly.
    The purpose of the gas is to give counterpressure to the air outside. You may have ever heard of experiments in which two half spheres are placed together, the air is pumped out and after that even horses can't pull hard enough to separate the halves again. That's air pressure doing that. A vacuum airship needs to have a shell that can withstand that pressure without collapsing, preferably while being lighter than some cloth and the gas inside it would have been, and cheaper too. It's a very non-trivial engineering challenge, and it carries its own safety risk. A small hole could cause explosive compression, so like explosive decompression in reverse. The damage to the inside of the balloon wouldn't be very bad, but you would in one moment lose all of your lift and plummet to earth slowed down only by the air drag the (supposedly still shaped) "balloon" provides, while a traditional gas balloon is much slower to empty, and thus easier to take in for an emergency landing, at the very least in theory.
    Last edited by Lvl 2 Expert; 2018-03-30 at 05:54 AM.
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  11. - Top - End - #101
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    Default Re: Airships as public transport Yay or nay?

    Agree with Lvl 2 Expert. A vacuum airship is only a theoretical construct for a good reason--nobody can figure out how to make a large, lightweight structure that will hold a vacuum against atmospheric pressure. Atmospheric pressure is a lot higher than people realise--14.7 pounds per square inch may not sound like much, but it means that the total pressure compressing an average human being is around 17 *tons*. A blimp the size of the Hindenburg would have hundreds of millions of tons of pressure to contend with if it was filled with vacuum!

  12. - Top - End - #102
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    Default Re: Airships as public transport Yay or nay?

    Quote Originally Posted by Rogar Demonblud View Post
    Actually, you probably don't even need to go that far. WWII reshaped the environment because of how much money was spent on aviation research--the U.S. alone spent about 1.5 trillion in current dollars. All you need to change is that instead of being stampeded into giving the money away, the government sticks to the original plan to issue low interest loans. The airplane industry ends the war with significant debt rather than cash flush, and probably without government funded civilian use plants ready to go.

    The change in momentum should give you what you need to keep using LTA craft.
    I agree- I think people under-estimate the effect that economic pressures can have, especially over a prolonged period. Where we ended up today is NOT inevitable, it was the result of a specific sequence of events with many contributing factors. Even if you only change a few small things, if you do it far enough back you can diverge quite a bit by the time you reach the setting you want to place your story in.

    As another example, suppose the US government had chosen not to deregulate the airline industry in 1978- how might that have altered the current dynamics? That sort of speculative history is strongly based on what sort of assumptions you go into it with and where you want to steer things.


    Combining this with a suggestion someone made earlier, I'm really liking the "HTAs exist, but are not available to the public, normally" explanation. They were/are considered weapons of war, especially in the immediate post-war period, and were pretty much on lockdown for several decades while the ABZ industry continued to develop, making ABZs faster, safer, and able to carry larger loads than what we see in our modern world. HTAs by contrast remained small and uncomfortable, and it usually requires a substantial permitting process to be allowed anywhere near one. Unless you are in the military or you've got sufficient political connections of course.


    Quote Originally Posted by Rogar Demonblud View Post
    Also, the uses of LTA craft currently are focusing on their ability to loiter in a small area--serving as a mothership for drones in search and rescue, for example. Overhead command centers for disaster relief. Or just an aerial cell tower--they were going to try that in Puerto Rico last year, but it didn't happen (I don't think I ever heard why).
    Here's another thought I just had- what about using a ABZ of some kind to lift a number of small gliders up and then release them? Since we don't readily available HTA aircraft, and it might not make sense to get out a giant ABZ for a short trip, this sort of thing replaces inter-island puddle-jumper aircraft.
    Last edited by Deepbluediver; 2018-08-28 at 09:58 PM.
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  13. - Top - End - #103
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    Default Re: Airships as public transport Yay or nay?

    Quote Originally Posted by Togath View Post
    Noticed this thread and haven't read through all the way... but I have wondered in a scifi or fantasy setting if a vacuum airship might be useful. Without the downsides of containing a gas, it seems like it could be a cheap alternative to airplanes for stuff that doesn't need to arrive as quickly.
    NPR's March 16th 2018 episode of Science Friday is discussing living on Mars, and one of their subjects is a Martian Airship. Their plan is for a vacuum-filled octahedral truss surrounded by a thin membrane for the lift balloon. Only would work on Mars because its atmosphere is 1% as dense as ours, though.
    Last edited by Lord Torath; 2018-03-30 at 07:35 AM.
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  14. - Top - End - #104
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    Default Re: Airships as public transport Yay or nay?

    Quote Originally Posted by Lord Torath View Post
    NPR's March 16th 2018 episode of Science Friday is discussing living on Mars, and one of their subjects is a Martian Airship. Their plan is for a vacuum-filled octahedral truss surrounded by a thin membrane for the lift balloon. Only would work on Mars because its atmosphere is 1% as dense as ours, though.
    Thanks for posting that link, I was wondering where the vacuum airships were coming from. I didn't watch a video there if there was one.

    I suspect they have the idea of vacuum airships on Mars wrong, the atmosphere of Mars is a lot less than Earths, as noted, but that also means there's a lot less lift from displacing it, and the pressure may be less, but it still goes up rapidly as you increase the area. Air pressure on Mars is according to Wikipedia 0.087 psi, that is 12.5 lb per square foot, or 113 lb per square yard. I think that's enough to break anything rigid that is light enough to fly in it.
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  15. - Top - End - #105
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    Default Re: Airships as public transport Yay or nay?

    Quote Originally Posted by halfeye View Post
    Thanks for posting that link, I was wondering where the vacuum airships were coming from. I didn't watch a video there if there was one.

    I suspect they have the idea of vacuum airships on Mars wrong, the atmosphere of Mars is a lot less than Earths, as noted, but that also means there's a lot less lift from displacing it, and the pressure may be less, but it still goes up rapidly as you increase the area. Air pressure on Mars is according to Wikipedia 0.087 psi, that is 12.5 lb per square foot, or 113 lb per square yard. I think that's enough to break anything rigid that is light enough to fly in it.
    I seriously doubt NASA would be considering it if they did not have a material that could withstand the pressure (although there is admittedly no mention of it in the linked article).
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  16. - Top - End - #106
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    Default Re: Airships as public transport Yay or nay?

    Could you make guided aircrafts?
    Say, a blimp or zeppelin that is connected to a line or chain to guide it and keep it steady? Updrafts, head winds and stability would all be much less of an issue. Just like trains, the airship could make easy and regular stops at specific points. They wouldn't even need to take off or land, just always stay afloat.
    It would be like a subway, or a train, but flying over (or under) the rail/line instead of rolling on top of it.

    The benefits compared to a train would be that they could make high-altitude lines without a heavy supporting infrastructure - I think a taut chain spanned between buildings could already function as a guide for a small airship. For a big metropolis this would evade all the problems with subway lines - no digging, no tunnels, not trouble bypassing existing buildings: simply span a line or rail between two points and attach small powered blimps to the line with some sort of pulley system.
    I'm thinking it might even have less friction than a train or subway track. I know a lot of ferries that are guided by actual chains underwater (the ferry just floats and is pulled across the water by the chain). I imagine these airships would be similar, but instead of floating on water they float in the air.

    Just throwing it out here. Would this be viable? Would it be vastly more expensive than building an entire subway system? Any problems I have not foreseen yet?
    Last edited by Murk; 2018-03-30 at 04:19 PM.

  17. - Top - End - #107
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    Default Re: Airships as public transport Yay or nay?

    Well, the biggest problem is where you actually put the cable? Buildings in cities aren't all conveniently the same height to string a cable along the top, and you can't put it between them (e.g. along the street) because there wouldn't be room for a decent-sized airship. It also doesn't solve the issue of public transport between cities. Also, how do people actually board and alight from the airship? Presumably they'd have to do that at the same level as the cable, which would require expensive modifications to existing buildings to allow that to happen.

  18. - Top - End - #108
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    Default Re: Airships as public transport Yay or nay?

    Plus, buildings aren't designed to take the large lateral loads that a tethered airship would induce on them. Not that they couldn't be modified to be more like pyramids, but they wouldn't look like they do today.
    Last edited by LordEntrails; 2018-03-31 at 10:37 AM.

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