11 ms·

Airships just don't work in strong winds, no need for a storm. And a plane can quickly move out of a hazardous location. An airship cannot move quickly.

chrisco255 5y ago
Is that true even if it has a large mass from cargo?
- lazide 5y ago
  Yes. It always has to have a much larger surface area in proportion to the weight it is carrying than any heavier than air craft, by definition. That means it has to have more volume to lift more weight. More volume means more surface area (though not linearly!). More surface area means more impact from strong winds, updrafts, downdrafts. And we haven’t figured out any plausible sort of propulsion that can even momentarily provide enough force to counteract something like a strong sudden downdraft without being too bulky to be practical.
  - hansvm 5y ago
    I think they still have a point though: Let X be any linear measurement of the airship (like length). The forces on the airship are proportional to X^2, and the max mass is proportional to X^3. Consequently, acceleration from wind and whatnot tends to 0 as the airship size increases (when fully loaded). Moreover, the necessary propulsion similarly scales with X^2 (which is convenient, because that's the amount of space you have to place the propulsion), while requiring increasingly negligible fractions of the ship's carrying capacity as the ship size increases.
    - lazide 5y ago
      Nice! Any chance you’d be interested in doing the math to figure out power to surface area ratios and what it would have to be to have the maneuvering capabilities of say a Cessna 172 in something like a blimp?
      - hansvm 5y ago
        If I'm not mistaken that's impossible as the size of the blimp increases (similar idea -- X^2 max power, X^3 mass, consequently acceleration and maneuverability are poor). The point was more that heavy winds aren't an issue for a sufficiently large blimp, even without maneuverability, because the impact of the storm on a blimp is negligible.
        FabHK 5y ago
        I'd think the forces would still be formidable. But yes, assuming the airship withstands the forces, it would not be thrown around as much (specifically: the accelerations and displacements would be lower) as it gets bigger. That seems plausible to me, by your x^2/x^3 argument.
        lazide 5y ago
        That doesn't make sense though - if the entire air mass is moving, and there is insufficient propulsion to go faster than the airmass is moving - then that airmass will carry the blimp into whatever that airmass hits? There is too much surface area for much else to happen right? Microburst wind speeds can hit 270km/h or more. Updrafts can hit 10,000 ft/minute or more [https://en.wikipedia.org/wiki/Downburst][https://www.britannica.com/science/updraft] https://en.wikipedia.org/wiki/Downburst][https://www.britann...
        hansvm 5y ago
        A few points: - The O(1/X) acceleration property prevents a 300km/h wind from getting the blimp to speed quickly. The "entire air mass moving" doesn't change that; you'll see wind flowing around the blimp, wind becoming turbulent and reversing directions, wind losing velocity and converting to heat and sound, local portions of the blimp temporarily deforming, potential blimp damage, and all kinds of other effects from a microburst, but you won't see a high mass-to-surface-area-ratio object have its center of mass accelerate quickly from wind drag. - The blimp _would_ need to have sufficient propulsion to counteract average wind forces over some time period. If you had a sustained downdraft with squared velocity averaging 270^2km/h over the surface of the blimp for any substantial length of time then the blimp would need equivalent upward propulsion to avoid _eventually_ crashing into the ground. For a sufficiently large blimp though, "eventually" can be extended as far as you'd like by reducing the acceleration induced by such forces and allowing you to average external forces over a longer time period before experiencing any negative repercussions.
  - Dylan16807 5y ago
    > Yes. It always has to have a much larger surface area in proportion to the weight it is carrying than any heavier than air craft, by definition. What do you mean 'by definition'? A heavier than air craft lifts with its surface. It has a relatively fixed surface area to weight ratio, no matter how big it gets. A lighter than air craft lifts with its volume. The bigger you make it, the less surface area you have per weight.
    - lazide 5y ago
      Heavier than air craft can be denser than air, by definition, and therefore have a lower ratio of surface area to weight - and hence less drag. This allows them to go fast (potentially), and power through problematic air turbulence with minimal impact. Lighter than air craft must (by definition), have an overall density less than the surrounding gas. This means their surface area and volume for any notable weight must always be quite large, and the corresponding influence from the surrounding air mass is always much, much higher, and their ability to fight any change in direction is always much less. Imagine what it would take to get a blimp to go the cruising speed of an airliner, and it might make more intuitive sense. And even those airliners avoid storms when they can. It might not be impossible - but it would require a degree of engineering not even considered here.
      - Dylan16807 5y ago
        The mistake you're making is to assume the two types of craft have similar-enough shapes that you can mix up surface area and volume. But even though a heavier than air craft has a lot less volume, it doesn't have to have less surface area. Planes are pretty flat, and have a much higher ratio of surface area to volume. A small delicate plane can weigh less than 50 grams per square meter. Or we could look at planes designed for human-powered flight. Those are ruthlessly optimized so you know they have no more surface area than necessary, and they weigh well under a kilogram per square meter, even if you added a motor on top. The balloons google was using to lift mini cell towers, at 50 feet wide, had about 2 cubic meters of helium per square meter of surface area. So about two kilograms of payload per square meter. And if you made it bigger you could turn that into five or ten kilograms per square meter without even trying. Is it extremely hard for a blimp to beat an airliner, which even for a plane has a small surface area? Yes. But lots and lots of other plane designs lose to a big blimp. Some of them even lose to a small blimp. Especially slow planes. And this is only talking about reasonable plane designs.
- dredmorbius 5y ago
  Cargo mass adds to structural stresses, and subtracts from mass available for increased strength and resilience.
- romwell 5y ago
  >Is that true even if it has a large mass from cargo? Nope. It's just plain false. To wit: During its career, Graf Zeppelin had flown almost 1.7 million km (1,053,391 miles), the first aircraft to fly over a million miles. It made 144 oceanic crossings (143 across the Atlantic, and one of the Pacific), carried 13,110 passengers and 106,700 kg (235,300 lb) of mail and freight. It flew for 17,177 hours (717 days, or nearly two years), without injuring a passenger or crewman. It never crashed, and was retired at the dawn of WWII. The huge airships get a bad rep because the only country which could successfully build and operate them was Nazi Germany. As for dirigibles operated by the US, the UK, and the USSR... yup, none of them actually worked. Doesn't say anything about the vehicle type.
mschuster91 5y ago
Even the old Zeppelin airships never had a major issue with strong winds - and these days we have satellites and aircraf-based weather radar. Storms are no danger for airships.
- abecedarius 5y ago
  That's not how I remember it from https://en.wikipedia.org/wiki/Slide_Rule:_Autobiography_of_an_Engineer https://en.wikipedia.org/wiki/Slide_Rule:_Autobiography_of_a... though yes we have much better weather forecasting now.
  - romwell 5y ago
    You mean, the book that wasn't about a Zeppelin? As in, an aircraft made by the Zeppelin corporation. The British never learned how to make dirigibles[1], the Americans never learned how to operate them; all non-German airship projects were failures. That's why Zeppelin became synonymous with "rigid dirigible airship". Because all other projects failed. [1] R100 was a good design... but it was scrapped because of politics, and never entered service.
- zardo 5y ago
  If you look up the ship dispositions several were torn from their moorings and wrecked in storms. And several crashed in thunderstorms.
romwell 5y ago
>Airships just don't work in strong winds Citation needed, my friend. Reality check: do you think that the airships which regularly crossed the Atlantic ocean never experienced strong winds? Perhaps a trip to an ocean beach is in order, eh?
- dredmorbius 5y ago
  Crashes of the UK R-101 (48 souls), and US Navy ZR-2 (44 souls), Macon (2 souls), Akron (73 souls), and Shenandoah (14 souls). Winds and/or handling failures affected all of these airships. https://en.wikipedia.org/wiki/R38-class_airship https://en.wikipedia.org/wiki/R38-class_airship https://en.wikipedia.org/wiki/USS_Macon_(ZRS-5) https://en.wikipedia.org/wiki/USS_Macon_(ZRS-5) https://en.wikipedia.org/wiki/USS_Akron https://en.wikipedia.org/wiki/USS_Akron https://en.wikipedia.org/wiki/USS_Shenandoah_(ZR-1) https://en.wikipedia.org/wiki/USS_Shenandoah_(ZR-1) https://en.wikipedia.org/wiki/R101 https://en.wikipedia.org/wiki/R101
  - romwell 5y ago
    You might notice that none of them actually crossed the Atlantic, because nobody except Germans knew how to build and operate airships. None of the airships in your list were Zeppelins. None were ever providing passenger service. Again, just examine the track record of Zeppelins, and compare it to the track record of contemporary aircraft safety-wise.
    - dredmorbius 5y ago
      The ZR-2 was in fact a Zeppelin, the Macon and Akron were built by the Goodyear-Zeppelin corporation, a joint venture. The Shennendoah (ZR-1) was based on a Zeppelin design (ZL-49) though built in and by the US. Only the R-101 and R-38 were entirely independent designs (both UK). The R-101 was specifically designed for passenger service, and was conducting a demonstration voyage when she crashed with major loss of life. The only reason it didn't enter commercial service was because it didn't survive long enough to do so. Another British airship, R-100, flew from Britain to Canada. Airships were built and operated by Germany, the UK, the US, French, Hugarian-Croatians, Brazil, and others. The Macon, Akron, and Shennendoah were all lost at sea or over water. There's nothing inherent to nationality, corporate ownership, military vs. civilian use, or passenger travel which changes the laws of physics under which airships operate. The craft are inherently vulnerable, slow, low, and dangerous. Modern widebody jet aircraft have the highest safety record by passenger-mile travelled of any transportation mode. There are more people aloft at any moment of the day than airships carried in any year of commercial operation. https://www.travelandleisure.com/airlines-airports/number-of-planes-in-air https://www.travelandleisure.com/airlines-airports/number-of... Every claim of your comment proves false. A solid record.

chrisco255 5y ago

Is that true even if it has a large mass from cargo?

lazide 5y ago
Yes. It always has to have a much larger surface area in proportion to the weight it is carrying than any heavier than air craft, by definition. That means it has to have more volume to lift more weight. More volume means more surface area (though not linearly!). More surface area means more impact from strong winds, updrafts, downdrafts. And we haven’t figured out any plausible sort of propulsion that can even momentarily provide enough force to counteract something like a strong sudden downdraft without being too bulky to be practical.
- hansvm 5y ago
  I think they still have a point though: Let X be any linear measurement of the airship (like length). The forces on the airship are proportional to X^2, and the max mass is proportional to X^3. Consequently, acceleration from wind and whatnot tends to 0 as the airship size increases (when fully loaded). Moreover, the necessary propulsion similarly scales with X^2 (which is convenient, because that's the amount of space you have to place the propulsion), while requiring increasingly negligible fractions of the ship's carrying capacity as the ship size increases.
  - lazide 5y ago
    Nice! Any chance you’d be interested in doing the math to figure out power to surface area ratios and what it would have to be to have the maneuvering capabilities of say a Cessna 172 in something like a blimp?
    - hansvm 5y ago
      If I'm not mistaken that's impossible as the size of the blimp increases (similar idea -- X^2 max power, X^3 mass, consequently acceleration and maneuverability are poor). The point was more that heavy winds aren't an issue for a sufficiently large blimp, even without maneuverability, because the impact of the storm on a blimp is negligible.
      - FabHK 5y ago
        I'd think the forces would still be formidable. But yes, assuming the airship withstands the forces, it would not be thrown around as much (specifically: the accelerations and displacements would be lower) as it gets bigger. That seems plausible to me, by your x^2/x^3 argument.
      - lazide 5y ago
        That doesn't make sense though - if the entire air mass is moving, and there is insufficient propulsion to go faster than the airmass is moving - then that airmass will carry the blimp into whatever that airmass hits? There is too much surface area for much else to happen right? Microburst wind speeds can hit 270km/h or more. Updrafts can hit 10,000 ft/minute or more [https://en.wikipedia.org/wiki/Downburst][https://www.britannica.com/science/updraft] https://en.wikipedia.org/wiki/Downburst][https://www.britann...
        hansvm 5y ago
        A few points: - The O(1/X) acceleration property prevents a 300km/h wind from getting the blimp to speed quickly. The "entire air mass moving" doesn't change that; you'll see wind flowing around the blimp, wind becoming turbulent and reversing directions, wind losing velocity and converting to heat and sound, local portions of the blimp temporarily deforming, potential blimp damage, and all kinds of other effects from a microburst, but you won't see a high mass-to-surface-area-ratio object have its center of mass accelerate quickly from wind drag. - The blimp _would_ need to have sufficient propulsion to counteract average wind forces over some time period. If you had a sustained downdraft with squared velocity averaging 270^2km/h over the surface of the blimp for any substantial length of time then the blimp would need equivalent upward propulsion to avoid _eventually_ crashing into the ground. For a sufficiently large blimp though, "eventually" can be extended as far as you'd like by reducing the acceleration induced by such forces and allowing you to average external forces over a longer time period before experiencing any negative repercussions.
- Dylan16807 5y ago
  > Yes. It always has to have a much larger surface area in proportion to the weight it is carrying than any heavier than air craft, by definition. What do you mean 'by definition'? A heavier than air craft lifts with its surface. It has a relatively fixed surface area to weight ratio, no matter how big it gets. A lighter than air craft lifts with its volume. The bigger you make it, the less surface area you have per weight.
  - lazide 5y ago
    Heavier than air craft can be denser than air, by definition, and therefore have a lower ratio of surface area to weight - and hence less drag. This allows them to go fast (potentially), and power through problematic air turbulence with minimal impact. Lighter than air craft must (by definition), have an overall density less than the surrounding gas. This means their surface area and volume for any notable weight must always be quite large, and the corresponding influence from the surrounding air mass is always much, much higher, and their ability to fight any change in direction is always much less. Imagine what it would take to get a blimp to go the cruising speed of an airliner, and it might make more intuitive sense. And even those airliners avoid storms when they can. It might not be impossible - but it would require a degree of engineering not even considered here.
    - Dylan16807 5y ago
      The mistake you're making is to assume the two types of craft have similar-enough shapes that you can mix up surface area and volume. But even though a heavier than air craft has a lot less volume, it doesn't have to have less surface area. Planes are pretty flat, and have a much higher ratio of surface area to volume. A small delicate plane can weigh less than 50 grams per square meter. Or we could look at planes designed for human-powered flight. Those are ruthlessly optimized so you know they have no more surface area than necessary, and they weigh well under a kilogram per square meter, even if you added a motor on top. The balloons google was using to lift mini cell towers, at 50 feet wide, had about 2 cubic meters of helium per square meter of surface area. So about two kilograms of payload per square meter. And if you made it bigger you could turn that into five or ten kilograms per square meter without even trying. Is it extremely hard for a blimp to beat an airliner, which even for a plane has a small surface area? Yes. But lots and lots of other plane designs lose to a big blimp. Some of them even lose to a small blimp. Especially slow planes. And this is only talking about reasonable plane designs.
dredmorbius 5y ago
Cargo mass adds to structural stresses, and subtracts from mass available for increased strength and resilience.
romwell 5y ago
>Is that true even if it has a large mass from cargo? Nope. It's just plain false. To wit: During its career, Graf Zeppelin had flown almost 1.7 million km (1,053,391 miles), the first aircraft to fly over a million miles. It made 144 oceanic crossings (143 across the Atlantic, and one of the Pacific), carried 13,110 passengers and 106,700 kg (235,300 lb) of mail and freight. It flew for 17,177 hours (717 days, or nearly two years), without injuring a passenger or crewman. It never crashed, and was retired at the dawn of WWII. The huge airships get a bad rep because the only country which could successfully build and operate them was Nazi Germany. As for dirigibles operated by the US, the UK, and the USSR... yup, none of them actually worked. Doesn't say anything about the vehicle type.

mschuster91 5y ago

Even the old Zeppelin airships never had a major issue with strong winds - and these days we have satellites and aircraf-based weather radar. Storms are no danger for airships.

abecedarius 5y ago
That's not how I remember it from https://en.wikipedia.org/wiki/Slide_Rule:_Autobiography_of_an_Engineer https://en.wikipedia.org/wiki/Slide_Rule:_Autobiography_of_a... though yes we have much better weather forecasting now.
- romwell 5y ago
  You mean, the book that wasn't about a Zeppelin? As in, an aircraft made by the Zeppelin corporation. The British never learned how to make dirigibles[1], the Americans never learned how to operate them; all non-German airship projects were failures. That's why Zeppelin became synonymous with "rigid dirigible airship". Because all other projects failed. [1] R100 was a good design... but it was scrapped because of politics, and never entered service.
zardo 5y ago
If you look up the ship dispositions several were torn from their moorings and wrecked in storms. And several crashed in thunderstorms.

romwell 5y ago

>Airships just don't work in strong winds Citation needed, my friend. Reality check: do you think that the airships which regularly crossed the Atlantic ocean never experienced strong winds? Perhaps a trip to an ocean beach is in order, eh?

dredmorbius 5y ago
Crashes of the UK R-101 (48 souls), and US Navy ZR-2 (44 souls), Macon (2 souls), Akron (73 souls), and Shenandoah (14 souls). Winds and/or handling failures affected all of these airships. https://en.wikipedia.org/wiki/R38-class_airship https://en.wikipedia.org/wiki/R38-class_airship https://en.wikipedia.org/wiki/USS_Macon_(ZRS-5) https://en.wikipedia.org/wiki/USS_Macon_(ZRS-5) https://en.wikipedia.org/wiki/USS_Akron https://en.wikipedia.org/wiki/USS_Akron https://en.wikipedia.org/wiki/USS_Shenandoah_(ZR-1) https://en.wikipedia.org/wiki/USS_Shenandoah_(ZR-1) https://en.wikipedia.org/wiki/R101 https://en.wikipedia.org/wiki/R101
- romwell 5y ago
  You might notice that none of them actually crossed the Atlantic, because nobody except Germans knew how to build and operate airships. None of the airships in your list were Zeppelins. None were ever providing passenger service. Again, just examine the track record of Zeppelins, and compare it to the track record of contemporary aircraft safety-wise.
  - dredmorbius 5y ago
    The ZR-2 was in fact a Zeppelin, the Macon and Akron were built by the Goodyear-Zeppelin corporation, a joint venture. The Shennendoah (ZR-1) was based on a Zeppelin design (ZL-49) though built in and by the US. Only the R-101 and R-38 were entirely independent designs (both UK). The R-101 was specifically designed for passenger service, and was conducting a demonstration voyage when she crashed with major loss of life. The only reason it didn't enter commercial service was because it didn't survive long enough to do so. Another British airship, R-100, flew from Britain to Canada. Airships were built and operated by Germany, the UK, the US, French, Hugarian-Croatians, Brazil, and others. The Macon, Akron, and Shennendoah were all lost at sea or over water. There's nothing inherent to nationality, corporate ownership, military vs. civilian use, or passenger travel which changes the laws of physics under which airships operate. The craft are inherently vulnerable, slow, low, and dangerous. Modern widebody jet aircraft have the highest safety record by passenger-mile travelled of any transportation mode. There are more people aloft at any moment of the day than airships carried in any year of commercial operation. https://www.travelandleisure.com/airlines-airports/number-of-planes-in-air https://www.travelandleisure.com/airlines-airports/number-of... Every claim of your comment proves false. A solid record.