What do you people think of this launch method?
At approx 3:05
This catapult method is suitable for small wings weighing 10 or 20 kg. As Makani’s wing scales as its take-off control becomes a more complex affair, without talking about the required catapult power and length for wings weighing tons. Now Makani uses incorporated VTOL mean by turning the wind propellers as we know.
A comparable method is shown on https://youtu.be/UPiTiHPXciE : it could scale more, but also the same for its cost.
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I’m not sure about the scaling issues with this one. The way I see it, wind + powerzone + kite speed should guarantee that the kite will fly all the way to zenith.
If your kite does not fly vertically in the power zone due to gravity, you might have to rethink the design IMHO. Or start flying at an angle to vertical.
The acceleration of the looping kite is already very high, so the catapult should not be an issue.
I guess the argument to kill this method is that the kite needs to have both speed and wind to work, and wind at ground level may be gusty at most spots. In addition, the tether length must probably be longer for a bigger wing, demanding a cleared area around the ground station.
I still think this approach is interesting though, due to the fact that it could scale to any size (please correct me on this if I’m wrong).
Disclaimer: These are my private thoughts, and not Kitemill’s official views.
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A good baseline launching method to compare with all others is tow-launch. Its proven to Gigant jumbo glider scale and still a mainstay in glider-sports, with winch-tow now common. Such a comparison with operational methods tends to make speculative methods look marginal. Another baseline comparison is SkySails launching its shipkites from a payout winch, which is not practical with fast rigid wings.
An ideal AWES launch method needs to get the kite up out of common calm surface inversion into the LLJ layer. Ballistic launch methods do not reach high enough for these common conditions. E-VTOL involves excess flying mass unless the E-VTOL component lands after launch while the WECS flies. Flygen mode does not solve the E-VTOL problem, but compounds inherent poor scaling.
My general view of Makani is that they are showing how not to do AWE, once the limits of their architecture are understood.
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Each architecture and operating environment has particular launch requirements.
Altitude, launch speed, wind speed, weather, permission and more requirements have to be satisfied for every working case.
Automation of deployment and recovery has often been stated as key to utility deployments (There are human employment and oversight arguments against this requirement)
This vertical spud gun type launch tube method worked for the small rigid architecture. Certainly didn’t land that way though…
The skysails mast launch, which automatically unpacks, inflates, launches then captures, deflates and stows a soft kite … is so impressive.
In terms of launching kite turbine networks (Daisy kites - my favourite kinda architecture) The launching of the turbine network itself is not so important as the launching of the lifting kite. The kite network can either get hoisted up a pre-established tense flying lifting line or the kite network is first stretched out then allowed to be pulled up by its top (Current method). The lifting kite however is a different matter… I don’t need the lifter to fly at a high angle, I just want plenty of line tension so that torque can be reliably transmitted down the stack of rings.
In this post on lifter kites Can you share your experience with your lifters? @tallakt likes a high angle on his lifting kites.
Because a Daisy turbine uses the lifting line as its axis, too high a lifting line angle means huge cosine losses… so yep I just want plenty of tension, and a low lift angle.
This means a lifter suitable for a Daisy kite turbine might well be a small Makani type kite as seen launched in the video above. Have it loop powerfully all day at around 30deg elevation generating enough to keep it controlled with spare to land neatly… sweet.
As it is, I’m super cheap (don’t need a space-pen when you have a pencil) the high lifting angle of the sssl is not a problem. I limit the maximum turbine stack elevation with a back-stop line, safer this way too…
Back to how this affects launching an sssl … I’d love to automate this without adding parasitic weight to the sssl there are a bunch of ways a drone could be employed to unstow, release, recapture and stow a soft kite.
Here’s where I show a couple dodgy video experiments…
I think you (as in you people) might be missing a few important things here: The kite is self propelled from ground level if there is sufficient wind where you fly. It is not a ballistic launch. This is how any beginner might launch a kitesurfing kite straight downwind, and it works well if you can control the power output.
Second point: you are almost guaranteed “wind” if the ground based winch is able to reel in at sufficient speed. I think there might be a feasibility window here, even for the larger sizes.
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Kind of off-topic here, but for lifter launches, I dont see why the following approach should not scale to any size:
Where the smallest doll is something like this:
The rest are soft kites in acsending order, the last being sufficiently powerful for your application
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Stacking and staged launching is a fab idea.
Makes handling easier too.
Being me I tried a dodgy test
I tried stacking the SSSL kites (the factory ones have an odd number of ribs) Sewing a rib on top and a strong line all the way through top to bottom…)
It kinda worked but if the top kite steered away from alignment with the lower kite …the lower kite would be forced to collapse… Being SSSL it was far from stable.
Boxy framed kite stacking, Isn’t that where the 100 year old altitude record comes from ?
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I’ve had that idea in my “toolbox” for a while, but did not yet require it. Would be fun to see what you could do with it. I would guess a redesigned SSSL kite with a slit in the middle to pass the main kite tether would be the most probably way forward, or just a different design kite that allows for easy stacking.
The slit idea still doesn’t prevent side to side collapse on misalignment.
Also any slit would ideally be sleeved and bridled to prevent pressure release to the upper through the skin
I don’t know a particular good solution for the SSSL kites. Perhaps a bridle on top is a valid way to do it? At least then there wont be such an incentive for the lower kite to collapse spanwise. I guess a redesign would be necessary for this kite.
Why not use a soft kite as a lifting kite to launch the rigid wing glider?
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Yes why not? I believe it just hasnt been done. There are a few issues though. I tried launching a LEI by the pump leash attachment, attached to a pilot/single line kite. The pilot has a very low elevation angle relative to ground, even lower when loaded by a 3 kg kite. And the kite was only stable upside down… just to give a taste of the challenges involved