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SkyLifter is an eVTOL air crane

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Re: SkyLifter is an eVTOL air crane

#61

Post by phreeza »

maxwell86 wrote: post #33
phreeza wrote: post #26

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 i…

Because it doesn’t work. You’d need a foot ball field of area, and a 3 story building, to life a small yacht like space. The wind forces on the surface would be extreme, and you’d need a lot of power to even stay somewhere stationary instead of flying away. All of this would add weight, increasing the volume of helium needed, increasing the wind exposed surface area, making the problem worse. You’d need a huge indust…

I don't know, I'm sure you are right that it's not practical as a mass market product. But just coupling together two Zeppelin NTs, they should be able to lift an average RV, so it doesn't seem impossible to me. And something like that should definitely be within the budget of an average billionaire?

Re: SkyLifter is an eVTOL air crane

#62

Post by doikor »

lstodd wrote: post #58
doikor wrote: post #3

Earlier quoted context omitted.

Just fly it close to the ground and the only controlled airspace is near airports (and some big cities, military stuff, etc). Should not be that hard to stay out of those for the most part if you are transporting stuff like windmill parts to the middle of nowhere.

If you fly low how do you deice the thing while avoiding terrain? Most of the crashes were due to flying into the terrain in adverse weather conditions after all.

Flying low does not mean "scraping trees" but for example Glass G airspace (uncontrolled basically) is everything under 1200' not near airports etc. For a lighter than air craft 1000 feet off the ground is quite a big margin of error actually.

And I doubt one would be flying something like this in bad weather anyway. One would just wait for the next weather window.

And one could easily take the ship into 4000' or something like that and still have minimal amount of other aircraft around once outside of airports (proper commercial jets fly at 40k feet or so).

Re: SkyLifter is an eVTOL air crane

#63

Post by doikor »

masklinn wrote: post #50
Toutouxc wrote: post #40

Earlier quoted context omitted.

I'm not sure I understand your point, are you saying that airships don't work? Because the Hindenburg was able to take 100+ people across the Atlantic (86 years ago!), that's much more than the maybe 10-person "luxury RV" that the OP was suggesting. Today's Zeppelin NT semi-rigid airships are reasonably small and can carry 10+ passengers on shorter flights. Yes, airships are expensive, inconvenient and slow, they lea…

> Yes, airships are expensive, inconvenient and slow, they leak helium and they require huge hangars and mooring masts, but that's far cry from "can't work". "Can't work" is a pretty good effective compression of "work on the barest of technicality while being more expensive, slower, less flexible, and less reliable than pretty much all alternatives". Also the Hindenburg was absolutely not able to take 100+ people ac…

> By comparison, bloody Concorde transported up to 128, with a crew of 3, in 3.5 hours, at lower prices.

Pretty sure the crew of Hindenburg included a whole bunch of waiters, cooks, etc. just like the Concorde had flight attendants on top of its flight crew of 3. Hindenburg was basically a small cruise ship in the air.

https://www.airships.net/hindenburg/interiors/ has some nice drawings/photos about the interior.

Basically traveling on it was more like a nice sleeper train with cabins and a good restaurant than a modern airplane.

Re: SkyLifter is an eVTOL air crane

#64

Post by lstodd »

doikor wrote: post #62
lstodd wrote: post #58

Earlier quoted context omitted.

If you fly low how do you deice the thing while avoiding terrain? Most of the crashes were due to flying into the terrain in adverse weather conditions after all.

Flying low does not mean "scraping trees" but for example Glass G airspace (uncontrolled basically) is everything under 1200' not near airports etc. For a lighter than air craft 1000 feet off the ground is quite a big margin of error actually. And I doubt one would be flying something like this in bad weather anyway. One would just wait for the next weather window. And one could easily take the ship into 4000' or som…

> 1000 feet off the ground is quite a big margin of error actually.

Actually, no. It can't maneuver fast enough, it can't gain altitude fast enough. A downdraft or a squall and it's going into a hill or a tree from 1000ft in no time.

Only good thing about lighter-that-air is that when they crash, they tend to crash slowly. Otherwise completely useless.

Re: SkyLifter is an eVTOL air crane

#65

Post by phreeza »

maxwell86 wrote: post #60
Toutouxc wrote: post #40

Earlier quoted context omitted.

I'm not sure I understand your point, are you saying that airships don't work? Because the Hindenburg was able to take 100+ people across the Atlantic (86 years ago!), that's much more than the maybe 10-person "luxury RV" that the OP was suggesting. Today's Zeppelin NT semi-rigid airships are reasonably small and can carry 10+ passengers on shorter flights. Yes, airships are expensive, inconvenient and slow, they lea…

> Because the Hindenburg was able to take 100+ people across the Atlantic (86 years ago!), that's much more than the maybe 10-person "luxury RV" that the OP was suggesting. Today's Zeppelin NT semi-rigid airships are reasonably small and can carry 10+ passengers on shorter flights. You can also build a car with square wheels and cross north america in one. > I'm not sure I understand your point, are you saying that a…

Why is it that small craft work but large craft don't, when two of the main problems you mention (leakage and wind shear attack surface) scale favourably with increased volume? Both should scale as 1/r per transported mass if my math is correct?

Re: SkyLifter is an eVTOL air crane

#66

Post by cycomanic »

lifeisstillgood wrote: post #38
CraigJPerry wrote: post #19

Earlier quoted context omitted.

>> 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 that's 411k m3 with only half that as gas capacity ! Interesting. But back-of-the-envelope lighter than air is just hard . It's certainly possible to see this working in niche areas, but boy, it's a tough sell compared to "get a giant Sikorsky"

It's somewhat interesting that people are saying this is unrealistic because of the possible 250t maximum lift version. And then people bring up helicopters, that just shows how little idea people have about what insane amount 250t is. The strongest helicopter is the Mi-26 with a lifting capacity of 20t (the sikorsky has something like 12t AFAIK) so that's an order of magnitude off. It is safe to say that building a helicopter with that lift is very likly out of our engineering capability.

Re: SkyLifter is an eVTOL air crane

#67

Post by cycomanic »

masklinn wrote: post #50
Toutouxc wrote: post #40

Earlier quoted context omitted.

I'm not sure I understand your point, are you saying that airships don't work? Because the Hindenburg was able to take 100+ people across the Atlantic (86 years ago!), that's much more than the maybe 10-person "luxury RV" that the OP was suggesting. Today's Zeppelin NT semi-rigid airships are reasonably small and can carry 10+ passengers on shorter flights. Yes, airships are expensive, inconvenient and slow, they lea…

> Yes, airships are expensive, inconvenient and slow, they leak helium and they require huge hangars and mooring masts, but that's far cry from "can't work". "Can't work" is a pretty good effective compression of "work on the barest of technicality while being more expensive, slower, less flexible, and less reliable than pretty much all alternatives". Also the Hindenburg was absolutely not able to take 100+ people ac…

What sort of comparison is that the concorde was flying from 1976, the Hindenburg disaster was in 1937. You say can't work is a good compression of not economically feasible and you come to the economically feasible by comparing 1937 tech/economics with 1976 one?

For comparison a commercial plane service didn't even exist for airfoil planes in 1937. So by your argument it was impossible to fly across the Atlantic (it wasn't actually, people had done it but your argument is uneconomical=impossible) , but nowhere close to bringing 100 passengers across.

Re: SkyLifter is an eVTOL air crane

#68

Post by maxwell86 »

phreeza wrote: post #65
maxwell86 wrote: post #60

Earlier quoted context omitted.

> Because the Hindenburg was able to take 100+ people across the Atlantic (86 years ago!), that's much more than the maybe 10-person "luxury RV" that the OP was suggesting. Today's Zeppelin NT semi-rigid airships are reasonably small and can carry 10+ passengers on shorter flights. You can also build a car with square wheels and cross north america in one. > I'm not sure I understand your point, are you saying that a…

Why is it that small craft work but large craft don't, when two of the main problems you mention (leakage and wind shear attack surface) scale favourably with increased volume? Both should scale as 1/r per transported mass if my math is correct?

> Why is it that small craft work but large craft don't,

Because the goal of small craft is to go with the flow wherever the wind brings you, because that's fun.

The goal of commercial crafts is to go or transport stuff from A to B, independently of wind, and they are really bad at that.

Re: SkyLifter is an eVTOL air crane

#69

Post by ZeroGravitas »

masklinn wrote: post #42
ixfo wrote: post #30

Earlier quoted context omitted.

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.

> 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. The problem is not building the thing (though it is one problem), it's that if you're using this as a crane you're moving an entire baseball field with a decimeter if not centimeter-scale precision.

The problem seems to scale with the weight carried.

I have no intuitive feel for how heavy 250 tonnes is, but even if current crane tech can move that weight with centimeter precision, they're explicitly marketing this for tasks where the current tech has issues with access, which implies they don't think it competes directly with traditional cranes on their own territory, but does work well enough in specific circumstances to be an option.

Maybe its a bad idea overall, or unrelated business model issues render it a dead-end, but beating the current product in every concievable metric in every concievable use case is not necesssry for a product to be a success.

Re: SkyLifter is an eVTOL air crane

#70

Post by ClumsyPilot »

CraigJPerry wrote: post #59
ClumsyPilot wrote: post #57

Earlier quoted context omitted.

I think this is fundamentally impossible, win loads are powerfull enough to ouright warp and destroy giant ground based cranes like they were tissue paper if the operator makes a mistake, like lifting oart of a stadium roof in high wind. there are scary videos all over youtube. Those things and made of hige steel girders. This is going to be a light, fragile airframe with much bigger 'sail' in the form of the airship…

The skin of a Boeing 747 is about 2mm thick. We’ve been hurling them at 600mph through storms for half a century at this point. I don’t know for sure but i suspect the airframe of this concept is within reach of current tech.

The passenger planes have a tendency to break in half mid air if they are subject to sudden stress, turns, etc, like TU 144 did at a paris airshow.

https://www.youtube.com/watch?time_continue=57&v=iEsLQd_yY0s...

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