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The figure below shows a cargo airship called "Flying Whales LCA60T" able to carry 60 tons of freight. In order to take the useful load from one location, the dirigible has to discharge up to 60 tons of water.

I know that its 32 thrusters are fixed: they can not pivot, but they can modify the pitch angle of their blades in the interval [-pitch_max, pitch_max].

My question would be: How can this airship position itself along the longitudinal axis of a container, or group of containers, in order to lift them on board, if the wind blows perpendicular to the longitudinal axis of the containers and of the airship?

I know that the airship is designed to work in winds as high as 11 m/s.

Yes, LCA60T can orient itself with the nose in the wind while hovering but the containers could have a position that is perpendicular to the wind. Besides this, while hovering, the airship has to be able to face lateral winds of at least 3-4 m/s because it is designed to work in the north of Canada (and other unfriendly locations) where the wind blows continuously.

Another question: What would be the lateral drag coefficient of LCA60T? (If I know the lateral drag coefficient of the airship, I can calculate the power needed by this machine to keep zero lateral speed (to hover) in a lateral wind of a few meters per second.)

The drag coefficient of such an airship while moving forward can be between 0.023 and 0.045 according to a 1932 study

Some explanations: LCA60T has two groups of 6 thrusters whose main purpose is to push the airship forward. It also has 4 groups of 4 thrusters each, I guess for stabilizing the airship in pitch, especially while hovering. There is also a group of 4 thrusters placed above the nose of the airship for yaw control at low and zero speed.

All 32 motors are electrical and are powered by a group of 4 helicopter gas turbines that each turns an 1 MW electric generator. So, in total, the max power available for the 32 thrusters is 4 MW.

View from below the airship showing locations of the thrusters

Flying Whales - An industrial project to revolutionize air cargo transport (Video posted on Jun 13, 2023).

Technical characteristics:

  • Length: 200 meters
  • Diameter: 50 meters
  • Volume of Helium: 180,000 cubic meters
  • Number of Helium bags: 14 nonpressurized helium cells
  • Useful load: 60,000 kilograms,
  • Cargo bay volume: 96 m by 8 m by 7 m high cargo bay
  • Speed: max 100 km/h, 80 km/h cruise speed
  • Range: 400 to 500 km around its base. Most of the time, the airship will fly no more than 100 km from its base. Each time (day) the airship will return to the base.
  • Hovering capabilities: LCA60T’s has a unique stationary hovering design for loading and unloading
  • Max altitude: 3000 m
  • Powerplant: Four Honeywell 1 MW turbo-generators
  • Efficiency of the 1 MW generator: 97%, Weight: 280 pounds, Power density: 8 kW/kg
  • The 1 MW generator can also be used as a motor
  • Number of thrusters: 32
  • First flight: the end of 2025 (most likely later). Serial production begins in 2027 at the earliest. Place of building the first airship: Laruscade (near Bordeaux), France.
  • Crew: 3, including a pilot and loadmaster
  • Daily operating cost: about $50,000

LCA60T delivering humanitarian aid. LCA60T delivering humanitarian aid.

LCA60T landing on its cradle. LCA60T landing on its cradle.

Flying Whales reveals the design of LCA60T.

The two picture above show no ground crew orienting somehow, using cables, the airship while it hovers.

UPDATE: Based on the lateral drag coefficient given by Peter Kämpf, I estimated the power needed to keep LCA60T hovering in a lateral wind of 5 m/s and no headwind. (The lateral cross section of 8400 m2 I estimated by using the top view image of the airship. I also took into account the surface of the rear fins.)

Power required calculation: 525 kW

This is a view from above of the LCA60T. This is a view from above of the LCA60T. Length = 200 m, max diameter = 50 m.

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  • $\begingroup$ Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Aviation Meta, or in Aviation Chat. Comments continuing discussion may be removed. $\endgroup$
    – Jamiec
    Commented May 8 at 13:07

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The design shows a few features which let me suspect that this is more an artist impression than a proper design.

  1. The tail surfaces are rather small for the size of the envelope.
  2. The hull seems rather stubby, with a diameter/length ratio of 1:4. A more slender design is much easier to control and has less drag, albeit at the cost of lower structural efficiency. 1:6 would be more credible.
  3. Arranging the propellers in line reduces their efficiency. I would understand counter-rotating pairs of two, but certainly not four in a row, each on their own mast.
  4. With that stubby hull the cruise speed will be very close to the critical speed. I doubt that anyone really looked into this!

Now to your first question:

How can this airship position itself along the longitudinal axis of a container.

It cannot. The airship has to be aligned with the local wind direction. There are two rows of sideways-blowing propellers on the top of the ship which can give the ship a limited sideways speed. However, since the rear row is further away from the rear end than the forward row is from the forward end, the forward row of propellers can only run at full power when the airship is meant to yaw. Also, besides a side force their location will cause a rolling moment.

Given the low propeller efficiency resulting from their position near the hull and the power needed which you calculated for a wind speed of 5 m/s, I estimate that roundabout 1 MW of electric power will be needed to keep the ship steady at a lateral wind speed of 5 m/s - with a substantial roll angle so the sideways shift of the low center of gravity can counteract the rolling moment of the side thrusters.

At the beginning of the payload pick-up process, when the airship is well balanced, a stronger sideways breeze will let it pivot around the payload like a kite. Only when in the middle of ballast release will there be noticeable tension on the crane cables and still enough weight of the payload to function as an anchor. Once the container is lifted up, it has to swivel to align itself with the airship. Given a bit of free space, this can be accomplished easily, with a few persons helping to dampen the movement of the container by pulling on ropes hanging from the container.

What is less easy to control is compensation of sudden gusts. Even a ground crew of dozens of people was insufficient in the past to prevent the sideways movement of airships in gusts.

LZ 8 after being blown into the hangar by a gust

LZ 8 after being blown into the hangar by a gust (May 16, 1911). Image source.

Airships had to respect weather conditions much more than airplanes do today. Their inertia prohibits them from fast maneuvering, so gusty weather must be avoided. Also, since the release of water ballast has to be finely coordinated with lifting up the load, any such pick-up maneuver will take several minutes in which the airship needs to stay reasonably close to the cargo, which will have progressively less ground load as the dumping of ballast progresses. Some sideways motion of the cargo shortly before the airship is light enough to lift it off the ground must be taken into account.

and your second question is:

What would be the lateral drag coefficient of LCA60T?

I would use the value for a horizontal cylinder and mix a bit of a sphere into it. The cylinder has a drag coefficient of 1.17 and the sphere 0.47, so in total, given that the cyclinder is dominant, it should be a value between 1.0 and 1.1.

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  • $\begingroup$ Thank you very much for such a comprehensive and helpful answer. Based on the lateral drag coefficient estimated by you, I added an update to my post in which I attempted to calculate the power needed to keep the airship fix above a location. (If there are mistakes I will correct them.) $\endgroup$ Commented May 6 at 20:25
  • $\begingroup$ @RobertWerner With your updated question I noted that there are corresponding lower propellers for creating a side force. I need to update the answer. $\endgroup$ Commented May 6 at 20:41
  • $\begingroup$ Peter Kämpf said: "There are two rows of sideways-blowing propellers each on the top and bottom of the ship". I am not sure I understand this statement. Yes, from the picture I posted (which is a view from above not from one side) it appears that this is the case but in fact the 16 propellers distributed in 4 groups have their shafts pointing in the vertical direction as in the case of a quadcopter. However, as the thrusters can not pivot, the airship has to develop some roll angle to move sideways. There are only four propellers on top on the dirigible close to its nose. $\endgroup$ Commented May 6 at 21:23
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    $\begingroup$ @RobertWerner I mistook the top view of the last picture as a side view. Sorry! $\endgroup$ Commented May 6 at 22:08
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    $\begingroup$ @RobertWerner Yes. A flying prototype will cost less, but full certification will be much more than that and be so expensive. And is required to earn revenue with the design. To break even, you will need a fleet of at least 100 such airships, operating successfully over decades. This again requires serious infrastructure on the ground. $\endgroup$ Commented May 8 at 0:11
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The project originated from ONF (the French National Forests Office) employees to improve the 4-ton capacity of helicopters carrying wooden logs from mountainous areas. The startup was created 12 years ago, funded by public and private funds from different countries, now targets multiple industries. Several fundraising campaigns have been successful but the project also gives rise to skepticism. Funding such projects is part of France history and has been revitalized under its current administration. At this time public investment in the project amounts to 90 millions euros.

A similar project in Belgium, FlyWin, was discontinued after testing a demonstrator.

The key need is the capability to load and unload while hovering, to allow operations on slopping ground. Horizontal stabilization is critical, as well as altitude keeping while transferring the load. A first test flight was initially planned for 2020, now delayed to 2028. According to this post:

  • Stabilization will be based on 32 propellers.

  • The team was testing them in a wind tunnel last Summer.

enter image description here

Our test also aims to evaluate the thrust generated by these propellers under high sideslip conditions. This data is essential for optimizing airship performance in challenging scenarios, ensuring safety and efficiency.

As long as the design is not complete, and the first flight not done, what can be said? We have seen here other highly speculative projects which are still not operational.

According to this article (in French), among the many problems to solve:

  • How to transfer 60 tons of freight to the ground and simultaneously load 60 tons of ballast? This problem is known since a long time and no solution has been found yet to keep the airship stable during this dual transfer.

  • The use of water ballast at freezing temperatures (Québec is part of the project). Tanks must be drained but also refilled while hovering.

  • The use of helium, subject to recent shortages and price variations. Filling the envelope could be as costly as several millions dollars, tightness is critical.

  • The navigation in windy conditions, which can slow or stop the aircraft.

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    $\begingroup$ The description as a "highly speculative project" seems extremely applicable here. Airships are anything but a new concept; what is new and so much better here to change the underlying economic and operational realities that have made them little but relics and an advertising oddity? Until it's flying & making money without massive subsidies, my skepticism will remain. $\endgroup$
    – Ralph J
    Commented May 6 at 22:21

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