The Aeronautical physics is flawed. It is a copy of a toy, and does not scale up.
Brian M
Without a major break through in battery technology then we do need to look at alternative fuels.

Hydrogen is a good starting point, but not convinced that its the only solution, we really need a high energy density fuel similar to petroleum products, but made via renewable/green processes.
No reason why it can't be carbon based either, provided the carbon is used from carbon already circulating (air) or the carbon element is retained and recycled.

i.e. We might already might have the right chemical fuel, we just need to be able to produce it sustainably.

The statement "...simplest possible airframe: a 6-rotor multicopter" seems to be a contradiction. For 3D steering it is enough to have three (3) rotors without cyclic (swashplate) control.

If only 3 rotors are installed (keeping the footprint of the vehicle unchanged) diameters of each can be increased. Bigger diameter of a propeller means, as a rule, higher efficiency.

Please, clarify why 6 rotors are needed? I am ready to be corrected.

Thank you!
IMHO, using hydrogen as fuel for any kind of land/air/sea vehicle is an extremely bad idea because sooner or later there would be accidents/leaks/raptures & hydrogen fuel is explosive! It does NOT start fires (like gasoline etc); it explodes like a bomb!

IMHO, for any kind of vehicle, which batteries cannot provide enough power/energy, it would be best to use a biofuel, like biodiesel!
(Which is easy & cheap to produce (from countless kinds of plants/biomass) & energy dense & VERY unlikely to start any fires, after ruptures/leaks!)
I applaud the use of Kelvin as a temperature reference without the "degrees Kelvin" reference that is so often incorrectly used. Unfortunately, "kelvins above absolute zero" is equally incorrect. Always Kelvin not kelvin or kelvins and it's always understood that 0 K is absolute zero. At least there are no descriptions of something being ten times smaller or ten times less than something else, as is all too common in these entries.
Laszlo KRUPPA , I'm guessing it's for redundancy since it will carry humans. But I agree with you that the statement is flawed.
To FB36:
While hydrogen may not be the best fuel from the standpoint of energy per unit of volume and the difficulty of storage, it exploding is not a huge issue. Pure hydrogen will only burn if it has oxygen and even then, it's a very controlled flame without the right mix of oxygen. It's only when a 1 to 1 H2 to O mix is reached that there is an explosion. It's not any different than gasoline, which is used safely in most current vehicles.
Aaaah an update about my Favorite aircraft ! ! ! This is so refreshing.
@all the naysayers, what a bunch of shallow minded and uninformed comments !
@owlpic Your comment does not even to begin to make sense !, This is the best aerodynamics for a basic hexacopter design that is out there in this size ! The Beauty is in it's simplicity being a Hexacopter !
@Brian M. It might not be the only solution, however it is a solution that not only Skai is working on to perfect. Clearly the Skai Team is working hard on this and obviously knows where the limits can be pushed, it is what they do 24/7 ! Carbon based will just keep on producing the environmental headache we all face with fossil fuels these days.
@laszlo Kruppa O please...REALLY ???? It IS the simplest for as it has not tilting motors or mammoth wings sticking out the sides, The 6 rotors makes for brilliant Redundancy ! ! ! I would not want to see it done ANY other way !!!!

@FB36 Again another senseless comment from you as in previous topics ! ANY kind of propulsion is dangerous, maybe your blind but have you seen how many thousands of people have been scorched to a crisp in aircraft related accidents due to Aviation Fuel ! ! ! ! I have seen them and its real bad, YET they are certified. Skais Hydrogen system will be MUCH safer ! ! !
@Username, The only Flaw is the perception of what it is that they are doing that you don't understand, the Skai Craft is one of the very best concepts out there !

Towerman, maybe attacking everyone isn't the best way to convince people that this is a great idea? I agree these are amazing concepts, and I agree that Hydrogen is safer than avgas or jetfuel. I look forward to these machines becoming reality, but there will be many failed attempts along the way, as with any breakthrough startups...
I'm tired of deliberate trolling. Comments meant to confuse and derail reality. None of those posters understand what Exactly it is that Skai and other brilliant concepts are doing Exactly. They don't care for these concepts they only want their primitive fuel guzzlers to be the be all end all for eternity ! I have no respect for those preaching misinformation,uneducated hearsay and deceiving comments.