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How do you build a sail for a blimp/hybrid airship and what would it look like? Similar to a sail boat how could a blimp maneuver without propellers? Can a blimp sail against the wind? Wind can travel in opposite directions over the same location depending on altitude.

Jet stream patterns.

https://earth.nullschool.net/#current/wind/isobaric/500hPa/orthographic=-41.18,34.22,610/loc=-58.714,40.895

enter image description here

On worldbuilding.SE: Could a city be built out of Balloons?

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    The two workarounds suggested in worldbuilding (that I remember) are to either give the vessel enough vertical height it can benefit from the slower winds close to surface to "create" wind shear or dynamic soaring, which would really be a gas bag assisted glider. Neither solution, even if they actually worked, looks much like a blimp or an "airship". – Ville Niemi Apr 14 '18 at 17:24
  • You must understand that sailboat rely on (at least) 2 fluids not going in the same direction or at the same speed (namely the moving air and the water moving either slower either in another direction). In the air, on average all the air mass surrounding the airship is going in the same direction. thus the motorized airship (balloon?) must follow this flow. – Manu H Apr 16 '18 at 13:14
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    Salomon Andrée and two companions attempted to fly over the North Pole in a balloon that used drag ropes and a sail in an attempt to be steerable to some degree. Even his belief that he was able to travel a mere ten degrees off the wind seems to have been wishful thinking, and the expedition ended in disaster, though the proximal cause seems to have been a leaky balloon. – sdenham Apr 16 '18 at 15:02

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Sailing vessels work by exploiting the motion difference between the air and the water. The sail holds the air and the keel holds the water.

Unless you have some severe wind shear (which comes with its own problems), or you have truly massive sails, there's no gradient for you to exploit because it's all air.

BowlOfRed
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  • something like a jet stream? –  Apr 14 '18 at 03:07
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    I don't have details of how strong the shear normally is near jet streams. If it's really fast like multiple m/s over 10s of meters height, it seems in the realm of physical possibility to extract that energy. I suspect such regions will be rare though. – BowlOfRed Apr 14 '18 at 03:16
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No, a blimp cannot sail against the wind. It can only sail with the wind.

A ship can sail against the wind because it is in contact with the water surface. There are three motions which acts on a ship:

  1. The hull limits the ship to forward and backward movement only. A ship cannot move sideways due to the massive drag generated by the water if it attempts to do so.
  2. The rudder can rotate the ship using reaction forces between the ship and water alone.
  3. The sail can be freely rotated to any direction.

In a blimp, (1) and (2) are gone because it does not interact with ground or water. It only interacts with air. Therefore, no matter which way you rotate the sails and no matter how many sails you attached to the blimp, it cannot move against the wind.

One may, perhaps, trade altitude for airspeed by diving, then use the airspeed together with rudder to rotate the blimp and make it travel in a desired direction, but then that would be like gliders and not blimps anymore.

kevin
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