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cool video! I wonder what is the smallest practical size for a personal zeppelin? I feel like a small craft would not require such complex docking. Volume incr

cool video! I wonder what is the smallest practical size for a personal zeppelin? I feel like a small craft would not require such complex docking. Volume increases as the cube of the diameter while weight goes by the square for the ship's structure itself plus a constant for what it can carry laden, and you'll lose a lot of "volumetric lift" as you bring it down in size. What's the difference in lift/density of hydrogen vs hot air, like in a balloon? I guess we've never seen them marketed so it's probably impractical. Too bad, good tagline for such a company, to indicate the bespoke nature of such personal transport: "Oh, the human!"

Animats 4y ago
> what is the smallest practical size for a personal zeppelin? About 80 cubic meters of helium.[1] [1] https://www.youtube.com/watch?v=xOJvtaiNp5c https://www.youtube.com/watch?v=xOJvtaiNp5c
- maxbond 4y ago
  That was awesome, thanks for sharing. (Nit: that's appears to be a blimp, it doesn't appear to have a rigid body.) Also relevant: https://youtu.be/CwABJGzifao https://youtu.be/CwABJGzifao (also a blimp)
- aaron695 4y ago
  > About 80 cubic meters of helium. This doesn't add up since you get ~1 kg per cubic meter. That design is an inflatable plane. https://www.guinnessworldrecords.com/world-records/443025-smallest-airship https://www.guinnessworldrecords.com/world-records/443025-sm... - "The particular design of the envelope creates lift as well as buoyancy, which allows the envelope to be smaller than if it solely relied on buoyancy to keep the craft aloft" Maybe with a small kid and a high tech envelope and hydrogen which is ~ 1.1kg. It would be impressive to get to 80 cubic meters. [edit] Those aéroplumes are fucking cool in the comment above. They are 110 cubic meters. They also fly them in caves - https://www.youtube.com/watch?v=07Cp_NfdLbE https://www.youtube.com/watch?v=07Cp_NfdLbE
  - Animats 4y ago
    > That design is an inflatable plane. It was clear that some of the lift came from the airfoil, but, you're right, that's most of the lift. It's similar to the Aereon inflatables of the 1960s and 1970s. Some flew, but were not very useful.
knodi123 4y ago
I've often wondered if there might be a more efficient propulsion design using modern materials, using something like a whale's fluke, or some flapping wings. Seems like in addition to personal zeppelins, there's room to innovate with more biological designs.
- perilunar 4y ago
  The trick to efficiency is to accelerate more mass at a lower delta v. Doesn't matter if it's rotating or oscillating. I.e. long flapping wings/tail or long, slow propellor blades. One benefit of an airship is large propellors are more practical than on a small plane.
- jacquesm 4y ago
  Tears for Fears and Brittany Murphy have you covered: https://www.youtube.com/watch?v=RQ9NERE5OHw https://www.youtube.com/watch?v=RQ9NERE5OHw
- perilunar 4y ago
  Also see the Festo Air Ray: https://www.festo.com/us/en/e/about-festo/research-and-development/bionic-learning-network/highlights-from-2006-to-2009/air-ray-id_33851/ https://www.festo.com/us/en/e/about-festo/research-and-devel...
  - knodi123 4y ago
    That's exactly the kind of thing I was imagining, thanks! And from 2010 no less!
- addaon 4y ago
  Propellers are usually up around 85% efficient at their design speed (with fixed pitch propellers falling off very rapidly away from this design speed, and variable pitch props having a flatter optimum). There's room for improvement here, but not a game-changing amount. A larger, slower prop captures most of the potential improvement with far less incremental complexity than something completely novel.
perilunar 4y ago
> What's the difference in lift/density of hydrogen vs hot air, like in a balloon? Density data from Wikipedia: Air @ STP: 1.225 kg/m³ Air @ 100°C (typical for a hot air balloon): 0.9486 kg/m³ → lifting force ~0.2764 kg/m³ Hydrogen: 0.0899 kg/m³ → lifting force ~1.1351 kg/m³ Helium: 0.1786 kg/m³ → lifting force ~1.0464 kg/m³ Subtract the density from air and you get the lift force (mass). i.e. hot air can lift about 24% as much as hydrogen, or conversely, you need 4 times the volume. There are hot air airships. See: https://en.wikipedia.org/wiki/Thermal_airship https://en.wikipedia.org/wiki/Thermal_airship

Animats 4y ago

> what is the smallest practical size for a personal zeppelin? About 80 cubic meters of helium.[1] [1] https://www.youtube.com/watch?v=xOJvtaiNp5c https://www.youtube.com/watch?v=xOJvtaiNp5c

maxbond 4y ago
That was awesome, thanks for sharing. (Nit: that's appears to be a blimp, it doesn't appear to have a rigid body.) Also relevant: https://youtu.be/CwABJGzifao https://youtu.be/CwABJGzifao (also a blimp)
aaron695 4y ago
> About 80 cubic meters of helium. This doesn't add up since you get ~1 kg per cubic meter. That design is an inflatable plane. https://www.guinnessworldrecords.com/world-records/443025-smallest-airship https://www.guinnessworldrecords.com/world-records/443025-sm... - "The particular design of the envelope creates lift as well as buoyancy, which allows the envelope to be smaller than if it solely relied on buoyancy to keep the craft aloft" Maybe with a small kid and a high tech envelope and hydrogen which is ~ 1.1kg. It would be impressive to get to 80 cubic meters. [edit] Those aéroplumes are fucking cool in the comment above. They are 110 cubic meters. They also fly them in caves - https://www.youtube.com/watch?v=07Cp_NfdLbE https://www.youtube.com/watch?v=07Cp_NfdLbE
- Animats 4y ago
  > That design is an inflatable plane. It was clear that some of the lift came from the airfoil, but, you're right, that's most of the lift. It's similar to the Aereon inflatables of the 1960s and 1970s. Some flew, but were not very useful.

knodi123 4y ago

I've often wondered if there might be a more efficient propulsion design using modern materials, using something like a whale's fluke, or some flapping wings. Seems like in addition to personal zeppelins, there's room to innovate with more biological designs.

perilunar 4y ago
The trick to efficiency is to accelerate more mass at a lower delta v. Doesn't matter if it's rotating or oscillating. I.e. long flapping wings/tail or long, slow propellor blades. One benefit of an airship is large propellors are more practical than on a small plane.
jacquesm 4y ago
Tears for Fears and Brittany Murphy have you covered: https://www.youtube.com/watch?v=RQ9NERE5OHw https://www.youtube.com/watch?v=RQ9NERE5OHw
perilunar 4y ago
Also see the Festo Air Ray: https://www.festo.com/us/en/e/about-festo/research-and-development/bionic-learning-network/highlights-from-2006-to-2009/air-ray-id_33851/ https://www.festo.com/us/en/e/about-festo/research-and-devel...
- knodi123 4y ago
  That's exactly the kind of thing I was imagining, thanks! And from 2010 no less!
addaon 4y ago
Propellers are usually up around 85% efficient at their design speed (with fixed pitch propellers falling off very rapidly away from this design speed, and variable pitch props having a flatter optimum). There's room for improvement here, but not a game-changing amount. A larger, slower prop captures most of the potential improvement with far less incremental complexity than something completely novel.

perilunar 4y ago

> What's the difference in lift/density of hydrogen vs hot air, like in a balloon? Density data from Wikipedia: Air @ STP: 1.225 kg/m³ Air @ 100°C (typical for a hot air balloon): 0.9486 kg/m³ → lifting force ~0.2764 kg/m³ Hydrogen: 0.0899 kg/m³ → lifting force ~1.1351 kg/m³ Helium: 0.1786 kg/m³ → lifting force ~1.0464 kg/m³ Subtract the density from air and you get the lift force (mass). i.e. hot air can lift about 24% as much as hydrogen, or conversely, you need 4 times the volume. There are hot air airships. See: https://en.wikipedia.org/wiki/Thermal_airship https://en.wikipedia.org/wiki/Thermal_airship