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SkyLifter is an eVTOL air crane

skylifter.eu

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Re: SkyLifter is an eVTOL air crane

#21

Post by davidhyde »

I'm calling bullshit on this. Slick marketing driven website, low resolution photos of actual prototypes, hand-wavy FAQ and no other technical details. They claim speeds of 40 knots but does that mean that can stay stationary in 40 knot winds (the same as traveling at 40 knots) or that it can hitch a ride on high winds? The wind forces on the balloon look they would be far too high for those tiny fans to counteract even with its flying saucer shape. And solar panels to power them? Come on!

250 tonnes is A LOT to lift. Look how big a hot air balloon needs to be to lift a few passengers in a basket. Sure helium has more lifting power but it doesn't create miracles. That means the balloon would have to be absolutely massive. Far bigger than the CGI renders they show on their site. Helium is very expensive and a lot of it will leak out of a balloon like that even if you can reclaim the bulk of it back at the storage site.

I'd like to be proven wrong because the idea seems wonderful but the only thing they may be successful at doing is lifting some money from the hands of some gullible investors.

Re: SkyLifter is an eVTOL air crane

#23

Post by masklinn »

Already__Taken wrote: post #8
krisoft wrote: post #5

Earlier quoted context omitted.

I think comparing it to a plane is misplaced. They call it a crane. Presumably the load and the craft arrives on a truck and you use it to hoist the load up the last few maybe hundreds of meter max. Do i read that wrong? Edit: yes! I was reading that wrong. To quote the relevant part: “SkyLifters fly from job to job, so they can do work in locations that would be challenging for land cranes.”

If you rent a crane though you're also paying for the crew to drive the thing to you. This really has a chance of just auto-piloting over to the job to be then be run by an operator.

You'll definitely be renting the crew. The skylifter website specifically mentions the one crew. And per my calculations the thing is the size of a cricket or baseball field, there is no way it'll be flying itself.

Re: SkyLifter is an eVTOL air crane

#24

Post by ck45 »

Roritharr wrote: post #7
Thomaschaaf wrote: post #4

In germany there was a similar project the "CargoLifter" which sadly never succeeded: https://en.wikipedia.org/wiki/CargoLifter

CargoLifter for me personally marks the beginning of the German Decline in Engineering. The reasons for why it failed are the same reasons why we have such large problems with infrastructure projects and are falling behind in innovative technology. It's a very sad read.

I have similar feelings about https://en.wikipedia.org/wiki/Transrapid. At some point the whole project became too political and nobody wanted to be responsible to either push the project or pull the plug. Instead a ton of money was basically wasted.

Re: SkyLifter is an eVTOL air crane

#25

Post by masklinn »

davidhyde wrote: post #21

I'm calling bullshit on this. Slick marketing driven website, low resolution photos of actual prototypes, hand-wavy FAQ and no other technical details. They claim speeds of 40 knots but does that mean that can stay stationary in 40 knot winds (the same as traveling at 40 knots) or that it can hitch a ride on high winds? The wind forces on the balloon look they would be far too high for those tiny fans to counteract e…

> 250 tonnes is A LOT to lift. Look how big a hot air balloon needs to be to lift a few passengers in a basket. Sure helium has more lifting power but it doesn't create miracles. That means the balloon would have to be absolutely massive.

Agreed, per my calculations it'll need to be around 120m wide, and 30 deep (lifeisstillgood comes up with slightly smaller numbers of 100 x 25, possibly because they used 1.1kg / m3 where I used 1 for the lifting power of helium). That's more or less a baseball field.

And it's just for the naked payload, you still need to account for the envelope itself, the solar panels, the cabin, the engines, the batteries, and the fuel (as, per site, it has a biofuel backup). That probably adds a dozen tonnes at least (the solar panels alone would be 5-10 depending how much of the top's surface is covered). By the end you're probably looking at a men's cricket field, one on the large size.

Re: SkyLifter is an eVTOL air crane

#26

Post by phreeza »

I don't get why none of these companies try to get ultrarich people to finance their development by selling "air yachts". Basically strap a luxury RV with big windows to the bottom of one of these airships.

Imagine the splash you could make at your friends yacht meeting when you float in from above. Watch emperor penguins migrate or elephants in the Okavango delta from the comfort of a couch.

What am I missing, why isn't this a thing?

Re: SkyLifter is an eVTOL air crane

#27

Post by smoyer »

lifeisstillgood wrote: post #14

I am trying to avoid being negative here but lifting 250 tonnes in remote / difficult areas is a serious challenge. The lift is not so much the problem (although that's a big balloon) - fighting wind sheer will require stupendous amounts of power. Especially as wind is pressing not just at that cargo but at the balloon itself. And anywhere that's remote / inaccessible almost always comes with lots of wind. Hmm, actua…

I came to admit I can't imagine how the small solar power "field" shown on top of the balloon could possible push that shape through the air - either at a reasonable speed for transport or to counteract wind. If lift isn't a problem as you pointed out above, what might work is a tethered version that basically replaced the need for a tower crane. You could develop a tethered, active mooring that was much like the four-point active anchor system the navy uses to accurately maintain position during submarine rescue.

Re: SkyLifter is an eVTOL air crane

#28

Post by nuccy »

wcoenen wrote: post #18
wepple wrote: post #12

Can somebody explain to me how it is able to hover (suggesting it is neutrally buoyant in air) but then attach a load and overcome the weight?

I was wondering about the same thing. It doesn't seem to be explained on the company site. The only thing I could come up with is to have neutral buoyancy air blatters that can expand/contract. These would be inside the volume of buoyant gas but connected to the outside air. Then pump the buoyant gas into a pressure tank to reduce buoyancy, or release it from the tank to increase buoyancy.

Yes, but the size of the blatter would be enourmous for 250 claimed tonnes: 1 m^3 of air weights 1.21 kg, so if to reach neutral buoyancy you use helium (0.18 kg / m^3) or vacuum (0 kg / m^3, best case), then to counteract lifting/releasing of just one tonne (1000kg) you need to offset 833 m^3 with vacuum and 970 m^3 with helium. Having blatter inside and having such high expension requirements means that the vehicle effectively needs two shells, which will add weight and complexity. Stretchable main "ballon" might be simpler.

Re: SkyLifter is an eVTOL air crane

#29

Post by willyt »

wepple wrote: post #12

Can somebody explain to me how it is able to hover (suggesting it is neutrally buoyant in air) but then attach a load and overcome the weight?

I looks like they tether it to the ground with tension cables to weights or piles when they are lifting very heavy loads. If this was replacing a standard construction crane that would be economic as these things often have their own significant foundations. If it's a piled foundation for a building it's not uncommon to put extra piles in where you will have cranes. Maybe smaller loads can be done with bladders as others have suggested. You only have to lift 25 tonnes to beat the MI-26 which is the biggest heavy lift chopper and hard to get hold of.

Re: SkyLifter is an eVTOL air crane

#30

Post by ixfo »

CraigJPerry wrote: post #19
lifeisstillgood wrote: post #14

I am trying to avoid being negative here but lifting 250 tonnes in remote / difficult areas is a serious challenge. The lift is not so much the problem (although that's a big balloon) - fighting wind sheer will require stupendous amounts of power. Especially as wind is pressing not just at that cargo but at the balloon itself. And anywhere that's remote / inaccessible almost always comes with lots of wind. Hmm, actua…

>> that is 100mx100mx25m That’s huge! I wondered how big was the hindenberg, wiki claims 245m long and 41m wide, and 41m tall (excl. cabin). Only 200k litres of gas capacity. 232k tonnes lift.

So it is huge, but well within historic capabilities - and materials science has come a long way since then. I'm quietly hopeful for this.
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