SkyLifter is an eVTOL air crane
skylifter.euI'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.
> 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.
Indeed, the Hindenburg could lift over 200tons however it’s useful lift (lifting capacity minus its own weight and structural limitations) was only about 10 tons…
Even if we ignore the lifting gas requirements just the structural requirements to be able to tie 250tons to the lifting body make this pretty much impossible.
This makes solar roadways and the air condenser solar water bottles seem viable.
For comparison the Airlander and P-791 only lift about 10-20 tons…
https://en.m.wikipedia.org/wiki/Lockheed_Martin_P-791
https://en.m.wikipedia.org/wiki/Hybrid_Air_Vehicles_Airlande...
> Indeed, the Hindenburg could lift over 200tons however it’s useful lift (lifting capacity minus its own weight and structural limitations) was only about 10 tons…
TBF it was 10t cargo on top of crew (40), passengers (50), and luggage. So probably closer to 15~20 useful lift.
Yes. Also, I was unable to find any information about the gas itself. The word "helium" isn't found on the website, they only mention "LTA"... Using helium could probably not be called green or sustainable, as it's not a renewable resource on earth, AFAIK.
I thought the website was more engineery than slick, but more specifically, the up to 250 tonnes appears to mean, we can envision building one of a sufficient size to deal with that. They have mockups of a 2, 25 and 250 tonnes, and the scale of the big one does seem very large:
https://www.skylifter.eu/air-crane/
So is this reaction just getting caught up on combining images of the small model, with the load capacity of the (theoretical) biggest model? There's lots of things, like cranes, that have a fairly standard size and a few mega sized examples used for very specific tasks.
My thoughts could not have been captured better than this.
This whole thing, like that flying wind-turbine thing or the solar road thing, is just bordering on plausible but so far away from feasible that one has to doubt the whole effort.
Its hard to imagine, in todays world of information at our fingertips that anyone could fool or misguide someone else, but as the current state of the world is, not only is a con job possible, but its getting easier and more profitable. The trick seems to be to be to make an idea, as I said above, bordering on the plausible but far away from feasible.
Yeah 250 tonnes is a lot.
Not sure if there is an alternative to helium or hydrogen, like maybe a void container, but it would still be heavy.
I guess they will suffer from bad press if they can't prove this can work. Easy to lie to investors but unless they have a prototype, I'm still very skeptical.
> 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.
Does it scale? Can you strap 10 of those things together (perhaps using some sort of scaffolding) to lift 10x the weight?
In the sense that lift is linear by volume yes, but the driving complexity I expect would increase superlinearly.
If you're strapping 10 things together, you're now dealing with a much less rigid structure, the straps/scaffolding are significant points of failure, and the attachment points don't scale the same way so you have to add an even more complex (and tangle-able) web of cabling for your payload.
Yes, individual cells filled with lifting gas scale nicely (after all that's how rigid airships are made), but the main issue here is "big", not the actual arrangement or architecture. You need BIG to be able to lift HEAVY.
I wonder if it would work in Venus atmosphere?
Operating a blimp on Venus would be a bit tougher than on Earth, partly because the density of Venus atmosphere is only 95 % of our air (less lift per lifting gas volume), and also because of the incredibly violent 100 m/s winds, 93 bar pressure and a temperature of 470 °C.
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, actually lift might be a problem ...
So to get 250 000 kg off the ground takes a volume of helium balloon (if the below site is right) of 250,000m3 (it seems to be fairly linear)
(this seems intuitive - air "weighs" about 1.2kg /m3 sea level, so a vacuum of 1m3 could lift 1.2kg. )
that is 100mx100mx25m ! that's the inner part of any athletic stadium. That's insane surely?
https://www.engineeringtoolbox.com/hot-air-balloon-lifting-f...
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.
>> 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.
> 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.
I think the difficulty is not that its a huge airship, its the precision required to use it as a crane.
That's an area i'd be quietly hopeful in. Assuming propulsion motors are available which are both:
Then there are already open source hardware and software solutions available for this - i'm not proposing someone slaps a pixhawk 4 on a huge airship and gets a few mates over to help tune the PIDs in Ardupilot - i mean that the know-how is there. Translating that into a product that would be suitable for controlling such an aircraft would be do-able. Certification costs and expensive hardware suitable to run it all on are a different matter.a) powerful enough to defend against wind acting against such a huge object b) responsive enough to change their thrust vector (power & direction) such that the associated PID loop can operate within some reasonable set point boundaryI guess this is a long way to say i don't think it'd be easy or cheap, but i don't think they'd have to make a break through innovation to make it possible.
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 - its the size of a stadium.
Nothing short of a rocket engine will be able to keep it in place.
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...
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"
> So that's 411k m3 with only half that as gas capacity ! Interesting.
Not sure how you reached 411, 245 x 41 would be 323k for a straight cylinder, which the hindenburg was nowhere near[0]. And the envelope was larger than the useful gas volume owing to the internal scaffolding, and the internal volume being subdivided into 16 cells separated by structural rings[1].
And the 232t useful lift was pure lift, before taking in account the 215t of the airship itself (at basic empty weight). The useful lift (payload) was 40 crew, 50 passengers, their luggage, and 10t cargo.
[0] https://3iz4pu1r2cxqxc3i63gnhpmh-wpengine.netdna-ssl.com/wp-...
[1] https://3iz4pu1r2cxqxc3i63gnhpmh-wpengine.netdna-ssl.com/wp-...
Thank you.
I got to 411k by 245x41x41 (figures in GP). Yes that's not a cylinder but I am just doing very rough maths.
I did not think about the useful lift - so while the Hindenburg is a 100 years old, a lift of 232k kg was competing with a empty weight of 215. incredible - and thanks for the links
It still seems back of the envelope that lighter than air lift is just not generally useful
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.
Lighter-than-air is still largely untapped territory today, and it's a shame because it should scale in size very well. Without going straight away into more ambitious projects that were fantasized the past century [0], I'd love for a resurgence of it.
Tons of companies over the years have taken a shot at it (CargoLifter, Aeros, Walrus HULA, HAV).
Turns out, so far, it's all been pretty shit, because outside of super specific niches airships are so slow they need to be much cheaper than aircraft, but the upfront costs to create massive-enough airships to even have a chance makes it a difficult proposition.
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.
If I remember correctly, Cargolifter failed to have a straightforward loading and unloading method. The airship is designed to lift a certain amount of weight, which has to be replaced as soon as you dismount the cargo. Cargolifter used water which was transported to the destination site via trucks. I only had a quick glance at the SkyLifter website, but I did not find any solution for that problem.
It seems surprising to me that there is not more information on the website regarding what gas this gas-filled lenticular-shaped aerostat thing is floating with. I understand they are aerostatic and the gas needs to be lighter than air, but that doesn't leave many options that are not helium I guess. And then in order to drop whatever they haul down, they'll need to either let it escape or contain it somewhere else, or spend energy at keeping it down somehow.
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.
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?
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 industrial hall to store it safely on the ground, and you can’t tie it with a rope anywhere.
The helium required to fill the balloon would make the operating costs of this thing absurd, cause it’s a lot of helium, that leaks all the time and have to be replenished, and helium is super expensive (and necessary for pricy things like cooling superconducting magnets applications, which have infinite budget).
Any 3rd year University student with basic knowledge of fluid mechanics, thermodynamics, and mechanic, can draft in a napkin why we already know that this can’t work.
I’ve sat in meetings where the VCs contracted me and others to do DD on these types of companies, where every contractor told them that this can’t physically work, and the VCs with too much money take that knowledge and translate it to “very high risk investment”. These companies got 100 million dollars and burnt through them, without nothing to show, but for the VC was more important to not have that money parked somewhere and be able to tell investors that they have “mobility companies” in their portfolio, which I think is borderline misleading / scamming because everyone knew that these companies “concepts” couldn’t physically move a thing, cause that was a physical impossibility with the tech that they wanted to use.
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 leak helium and they require huge hangars and mooring masts, but that's far cry from "can't work".
> 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 across the atlantic, half of that was crew which you don't usually consider "taken over" as they have to fly back. So Hindenburg took 3 days to carry 72 passengers across the atlantic, needing 40 crew to do so, at a ticket price of $7460 (one way, in modern USD).
By comparison, bloody Concorde transported up to 128, with a crew of 3, in 3.5 hours, at lower prices.
> 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.
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.
> 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 airships don't work?
No, I'm saying that companies that try to sell airships don't work.
These companies are good at raising money, because the idea they sell is simple to explain, and many people don't do due diligence.
But in the same way that a car with square wheels is a worse solution to the problem, along pretty much any axis of comparison, than any of the alternatives available in the market, so are airships. With the difference that airships are also way more expensive than the solutions that are already in use.
This is why companies that build and try to sell them, default in 3-5 years after having raised the money.
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The only types of airship that "works" are balloons able to cary 2-5 people. The weight is small, so the balloon surface is also small against the wind, the components required to drive them are simple and easy because the balloon is "small", and their use is purely occasional and recreational (or a tourist attraction where you can charge a bonus), so cost isn't a "huge" issue. People pay for the "fun", not to go from A to B.
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.
So you're saying a luxury air yacht could work after all?
No, because people buying a luxury air yacht care about going from A to B.
If your claim is that there is a market for luxury air yachts that are extremely expensive to maintain, require a huge crew 10x larger than a yacht, are 10x "smaller" than a yacht, and can't remain stationary somewhere nor from A to B, but instead only can go "wherever the wind goes", then I don't believe you.
Feel free to prove me wrong. But the amount of yachts in Montecarlo during the F1 grand prix suggests that a significant market of the luxury yacht market does care very much about going from A to B, and about being able to remain stationary in their yacht somewhere.
So not being able to go from A to B and having to put your "yacht" inside a crappy hangar without views to be able to stay at one particular place pretty much kill the idea.
OK fair enough, I was thinking more about the operations within a day, when the travel style of a Goodyear blimp would be sufficient. But you are right that long distance point-to-point travel would likely be a requirement for the longer timescales.
FWIW I'd be really interested in a writeup of your actual napkin math that convinces you of the infeasibility so strongly.
The math is simple, its just the Archimedes principle, fluid drag force basics, and power law of propelers and jet engines.
Archimedes says:
m = V * (density air - density helium)
that is, the total mass that you can carry (including helium, propellers, fuel, all of it), scales linearly with the volume V of the balloon, and the difference in densities between the gas inside and outside.
There is little that you can do about the density difference beyond heating helium to make it larger, but at equal temp on the ground its 0.1, so you end up with:
m = 0.1 V
so if you want to carry 120'000 kg, then you need 1'200'000 m3 of helium.
That's a lot of helium. If you put it in a ball, the radius would be 66 m. or 132 m diameter. The wind surface of the ball would be 13'685 m2.
The force of air on a ball is obtained from the definition of the drag coefficient:
F = density_air * C_d * v^2 * A
The C_d is worse at low Reynolds number, so lets fix that at 1.0 (worst case, it gets slightly better as the flow speed increases, but whether its 1 or 0.8 it doesn't really matter).
So if you want to stay stationary at 20 m /s winds (72 km / h), then you need to apply a force of
F = 1.225 kg/m3 * 1.0 * 20^2 * 13'685 = 6.7 MN
The power required to produce similar thrust via a propeller is more or less
P = sqrt(F^3/(rho * A_propeller))
so with 10x 2m diameter propellers, you'd need
P = sqrt(6.7^3 MN / (1.225 * 10 * pi * 1^2)) = 2.8 MW
of power. If you actually wanted to move against the wind at 70km/h you'd need almost 6 MW.
That's not "a lot" but is not "nothing either".
If you take Rolls-Royce AE 2100 engine powering the C130 Hercules, each engine produces 7.5 MW. These engines aren't "silent", so riding in this thing isn't going to be nice, but no engine in this league is silent.
Considering that you also need electricity and other stuff on board for a crew of 20-40 people...
You end up that for 120 tons, you need at least one cargo aircraft propeller engine to be able to move at 70km/h against the wind (which is pretty slow). You might want two, you know, in case one fails, and the wind carries you to antarctic.
From those 120 tons, you need to subtract the helium, the propellers, the crew, etc. to get to the effective weight that you can carry.
If you wanted to go faster, notice that the drag increases with velocity square. You can try to reduce the surface like zeppelins do, but the surface is still going to be pretty big, because "volume" is what make these flight.
Also if you reduce the surface in travel direction, you are going to increase lateral surface cause that's how volume works, and that's going to make it worse when you have cross winds.
For any reasonable speed you might be looking at close to 20 MW of power, which is 777 jet-turbine like amounts of power.
So why doesn't make sense to build this to go from A to B?
Cause physics. If you want this to "float" (you can't really call this flying), you need absurd amounts of volume, and it turns out, that moving things with a large volume through a fluid requires a lot of energy.
You could do a more detailed analysis, improve the performance of every single component by 10x, but you can't change the physics.
Even if you just want to lift cargo, and barely move it from A to B, this wouldn't make sense, because the surfaces created by the huge volume would mean that you need absurd amounts of power to just stay stationary in case of "mild" winds. Even if you had enough power, wind changes direction quickly, but the huge propellers required for this don't. So if you need to lift heavy cargo, you probably need to position it with < 1mm tolerance, cause by definition you can't move heavy cargo after you position it, so you gotta get it right (e.g. something like a highway bridge).
You can't do that with this thing either cause of physics (big area, movement very sensitive to wind, impossible to control).
For the luxury thing, you end up much better with a luxury private jet, or a private 787 or whatever. The C130 Hercules, can take off with 137 tons, is orders of magnitude faster and cheaper, and only needs a crew of 3!
For transporting a bridge, you end up much better with a bunch of heavy cargo helicopters.
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Instead, if you just "float" somewhere, and you don't care were, balloons and zeppelins are pretty good.
They aren't as good as a modern glider obviously, but they benefit from working with the physics and not against them.
Other vehicles that "float", like boats and submarines, exploit the fact that water is way denser than air, yet even they have pretty big submerged volumes, but luckily for them water doesn't change direction as fast as wind does.
Thanks for writing this all out, but I think your initial calculation is off by an order of magnitude, no? You need 1m^3 of helium to lift a kg.
I don't have time to work through the rest now but I'll give it a shot tomorrow.
If you heat the helium enough, yes.
But even with 1 order of magnitude less volume, the fluid dynamics are still really bad.
These things "fly" like a brick, we are just making this brick lighter and lighter, but a brick is a brick.
We'd have to shape the helium into an airfol (an helium airfoil) to solve the main drawback.
Well you don't have to really heat it, it's just room temperature. The kind of density you are talking about is only reached well below 100K.
So here is my take on your estimate:
First of all, I was thinking more about an RV-sized gondola. So something like this [0].
The axles are rated for 30000 lbs together, so let's say 15000 kg fully loaded. This includes ridiculous stuff like marble countertops, so there is likely a lot of headroom for trimming weight.
Taking that into account, and the room temperature helium density, we get 15000 m^3 of volume.
Then I would argue that taking a sphere is really not the right approach, because it has poor drag coefficient and also having this elongated shape is what gives you control authority (try steering a circular boat with a rudder, any rudder you apply will just make you spin). The argument about crosswinds also does not really apply because you would always point the nose at the apparent wind, not dead at the direction you want to go. Same as a boat in current or an aeroplane. The exception are gusts of course, and I do see those could pose a problem.
So let's take an ellipsoid with a 1:2 aspect ratio. you need semi major axes of a=b=12m and c=24m to get ~15000m^3 volume. So this thing will definitely not fit in your garage, but it will fit into a pretty standard barn that any rural construction crew builds routinely.
The frontal area is then pi*(12m)^2 = 452 m^2. The drag coefficient for such an ellispoid is somewhere around 0.1 from what I can tell. Can get even lower for a proper airfoil shape but let's go with 0.1 to account for stuff like the gondola etc.
For 20m/s, (way faster than any water-based yacht can travel) gives a force of
1.225 kg/m3 * 0.1 * (20m/s)^2 * 452 m^2 = 22 kN
and a corresponding power needed of
sqrt((22kN)^3 / (1.225 kg*m^-3* 10 * pi * 1m^2)) = 0.5 MW = 700hp
That seems like a very realistic power requirement for such a vehicle, the RV I liked to earlier has 600hp. Might have to be a bit more because the prop area is perhaps a bit much here, but that scales linearly so I don't think thats a huge problem.
Of course if you want to maintain TAS much above 20m/s things escalate quickly. For 40m/s:
1.225 kg/m3 * 0.1 * (40m/s)^2 * 452 m^2 = 88 kN
sqrt((88kN)^3 / (1.225 kg*m^-3* 10 * pi * 1m^2)) = 4.2 MW = 5200 hp
which does indeed seem excessive. But I think for such a craft 20m/s would actually be acceptable. Can't fly it in a storm and can't compete for speed, but both those things are true for leisure sailing yachts.
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?
This will be a pain in the ass to manage in controlled airspace because it's so much slower than anything else. But I guess it would also use different flight levels, so maybe not a problem at all.
I wonder how does the fuel usage compare to a plane, that's the real measure of green-ness.
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.”
> Presumably the load and the craft arrives on a truck
Nah they're absolutely gigantic and usually semi-rigid (especially if you have solar panels on top).
SkyLifter seems very cagey about the purported crane's dimensions (couldn't find anything on the subject), but the Airlander 10 (which I understand only lifts 14t) is 90 x 43 x 26... meters.
IIRC the rule of thumb is that you need 1m3 of helium to lift 1kg, to lift just a 250t payload you thus need 250000m3 of helium.
According to skylifter's "design" page the lenticular envelope has a height of 1/4th the diameter (3 units wide, 0.75 units deep). For a cylinder that's 108m wide and 27m high, so taking in account the lenticular shape we might be closer to 120m/30m (400ft wide by 100ft high). That's the size of a baseball field, and 14 stories high.
And that's only taking the payload in account, not the solar panels, not the cabin, not the engines, ...
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.
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).
> 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.
It doesn't look big enough. Basically it's Archimedes principle, same as for stuff that floats:
The force produced is the weight of the mass displaced. So a hole in the air would lift up an equivalent mass to what the air in that hole would have weighed. For a ship this is a heck of a lot, since water is a lot denser than air. You can have a huge cruise liner because the hole it makes in the water would weigh 1T/m3, which for the size of such a ship is enough to lift up a massive chunk of metal. But air is nowhere near as dense, so even a cruise ship water-hole sized balloon with magic gas that weighs nothing would only be able to lift ca 1/1000 of the ship.
One trick you can do with air is heat it up so that the atoms push the sides out more, making your balloon bigger for the same mass. I'm not sure how to quantify the difference though. I suppose you take the ideal gas law and say it's proportional to the absolute temp? Limited how hot you want to make the thing that's naturally at about 300K.
Can't tell how big they intend to make this but it just looks like isn't big enough. A big enough balloon would also give rise to other engineering issues, like what do you do with wind and how to you keep the helium inside?
Also if this kind of thing generally worked every moving company would have one. Stick a balloon your sofa, get the kids to take it to your new house.
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?
Basically two methods:
1) have counterweights (e.g. as mentioned above for another similar concept Cargolifter which used water);
2) expand its volume during loading and contract after unloading. E.g. pumps compress gas while unloading and release it back while loading.
These two options are obviously the same thing - change the vehicle density to adjust the buoyancy but implemented with and without external weights. Submarines do this also by filling the ballasts tanks with either water or flushing them with compressed air.
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.
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.
That makes sense. It would indeed be simpler to make the buoyancy volume variable in that case.
I'm not sure though that fabrics exist which are both stretchable and can hold on well to small molecules like helium. (e.g. mylar can be stretched only 4% at most.) Maybe some type of "accordion" type connection between the bottom and top halves of the saucer-shaped balloon would work.
It can just swap weight(s).
So instead of having to move your 25 ton cargo around, you now have to move your 25 ton ballast to be swapped for the cargo at the drop off point so the SkyLifter doesn't yeet itself into stratosphere.
The FAQ and literally everything else about this project is vague, disappointing and a little fishy.
Cranes also use counterweights.
Crane counterweights are a completely different matter. The crane doesn't have to drop the counterweight to take on load (the opposite really, unless it's a superheavy with active counterweighting the entire point is to be more stable once loaded).
So the issue with this thing is, any time you move an actual load from A to B, you need to have a weight waiting for you at point B. Or to offgas at which point you won't be able to make a second trip without regassing.
If the weights remain on the ground you can use a pulley system to load and unload weight, just put slack in the cable and lighten the load… Could even be automated with the right sensors.
Similar project? https://www.flying-whales.com/
(Not saying if any of those is viable, just mentioning in case it makes the conversation more interesting.)
Doesn't this type of craft normally struggle with any kind of wind?
I can imagine that seriously hampers it's profitability when it can't be used 90% of the time because the wind threatens to be more than 10 mph...
"Hi! We built a balloon!" "Okay."