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VTOL On Demand Mobility

mboeller

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nice article:

especially this quote:
As opposed to some companies who were raking up hundreds of flights and saying very little (e.g. Joby Aviation) or flying a lot and talking a lot (e.g. EHang), Lilium was sometimes considered to have a “big mouth” — making wild claims that it seemed unlikely to be able to back up.

finally some technical paper also (link in the article above, but that link goes only to the investor page)

direct link: https://lilium.com/files/redaktion/refresh_feb2021/investors/Lilium_7-Seater_Paper.pdf
 
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yasotay

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This looks very promising. It think this team "got it right". The Joby machine is very attractive, but all of the parts likely impact the bottom line more adversely. Per above I think there will likely be two or more markets (long[er] range and short range).
 

Zoo Tycoon

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So Archer are to float via a SPAC,.... yippee they’re worth a Billion;-


Except they’ve now been sued for patent infringement......ah no they’re financial liability -


Interesting commentary on SPAC;-


SPAC = Shrinking Prospects? Access Cash!

Need to get some popcorn and enjoy the forthcoming show.
 
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AeroFranz

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There's a Wisk blog post about the suit. As you would expect, it's difficult to imagine it would be an objective assessment of the facts, but they do post a picture of the patented configuration and the current Archer configuration side-by-side. They look EXACTLY the same. And i don't mean they happen to have the same fuselage shape, or they both happen to tilt some propulsors.
No, it's the kind of similarity where too many things are exactly the same for it to be a coincidence. The kind of thing where i would dare someone to take a good look at both for a solid minute, then show them an unmarked outline drawing of one of the two, and i bet they wouldn't be able to say which it is.
Okay, one has skids and the other wheels, but other than that all the main bones of the vehicle look the same.
 

Zoo Tycoon

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The basic architecture of quite a few of the more serious proposed eVTOLs is tending to gel on a Curtiss Wright X19 derivative. Joby, Wisk. Archer, Vertical Aerospace, Hyundai to name but a few.

eVTOL has laid on a fine lunch and the lawyers are coming to feast.
 

Zoo Tycoon

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nice article:

especially this quote:
As opposed to some companies who were raking up hundreds of flights and saying very little (e.g. Joby Aviation) or flying a lot and talking a lot (e.g. EHang), Lilium was sometimes considered to have a “big mouth” — making wild claims that it seemed unlikely to be able to back up.

finally some technical paper also

direct link: https://lilium.com/files/redaktion/refresh_feb2021/investors/Lilium_7-Seater_Paper.pdf

The Great Lilium Ponzi Scam continues;-
So, I read the attached report a week or so ago and outwardly it looks pretty impressive. However the devil is always in the detail and their claim on battery power density/energy density looked odd. Normally these two properties are mutually exclusive. So, naughty me, I followed up the detail;- reference on page 25: "The cell family introduced by Shirk and Chinh (2020), demonstrates that a constant specific power beyond 2kW/kg can be achieved with eb ≈ 300W h/kg". That's wrong, just look at page 3 of the referenced data:
the graph shows that @300 wh/kg (energy) you can get at most 1.1kW/kg (power) which is very insufficient for the hover power (2.7kw/kg). For the required hover power, it needs around 270 wh/kg energy density (just look at the graph).

For a current battery that meets the required Power density over Energy density requirements it needs a factor of around 8.4, hence an energy density of only 200 wh/kg;- closed to half of that required to meet the performance promised.
https://voltaplex.com/samsung-25r5-18650-battery-inr18650-25r5.

How can 400 of Europe’s top engineers miss this ? Remember Liluim are telling their investors that it’ll be in commercial service in three years from today.

There’s more in Lillium 7 seater report which is of a highly dubious nature as well;- L/D, disc loading, noise, not to mention the Liliuim’s mystery of a lack of transition demonstration.
 
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VTOLicious

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Imho the report is not worth reading. The question is whether why one would publish a scientific paper that is based on a lot of assumptions when a flying prototype already generated a lot of test data that could be used to proof the theory :rolleyes:

...and btw, they already released CGI of a 16 seater as well
 

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AeroFranz

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I need to take a look at that report myself, thanks @Zoo Tycoon, i will look for those items you highlighted. The reason for a lack of transition flight video may be that...it's difficult.
Either
a) they didn't try it because if they crash investor confidence will plummet
b) they flew it and they crashed it, and are keeping it under wraps

admittedly there may be other explanations, i'm probably being influenced by my dislike for their entire operation...
 
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yasotay

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I saw this video and think this EVTOL solution has the right stuff. The designer has really thought through the bottom line, which is critical to vendors. This is why UPS and, to a lesser extent the USAF, have jumped onboard with this design. I wish them well.
 

DWG

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One of the eVTOL companies turned up in an ad on my browser a couple of weeks ago claiming it was going to be the greatest investment opportunity since Tesla. I laughed so hard I meant to share it here for amusement, but promptly lost track of which one it was. I've just found it again, or rather an article on its self-promotion:


It looks like they're trying to achieve eVTOL market dominance via the hot air method.
 

Reaper

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I need to take a look at that report myself, thanks @Zoo Tycoon, i will look for those items you highlighted. The reason for a lack of transition flight video may be that...it's difficult.
Either
a) they didn't try it because if they crash investor confidence will plummet
b) they flew it and they crashed it, and are keeping it under wraps

admittedly there may be other explanations, i'm probably being influenced by my dislike for their entire operation...
nice article:

especially this quote:
As opposed to some companies who were raking up hundreds of flights and saying very little (e.g. Joby Aviation) or flying a lot and talking a lot (e.g. EHang), Lilium was sometimes considered to have a “big mouth” — making wild claims that it seemed unlikely to be able to back up.

finally some technical paper also

direct link: https://lilium.com/files/redaktion/refresh_feb2021/investors/Lilium_7-Seater_Paper.pdf

The Great Lilium Ponzi Scam continues;-
So, I read the attached report a week or so ago and outwardly it looks pretty impressive. However the devil is always in the detail and their claim on battery power density/energy density looked odd. Normally these two properties are mutually exclusive. So, naughty me, I followed up the detail;- reference on page 25: "The cell family introduced by Shirk and Chinh (2020), demonstrates that a constant specific power beyond 2kW/kg can be achieved with eb ≈ 300W h/kg". That's wrong, just look at page 3 of the referenced data:
the graph shows that @300 wh/kg (energy) you can get at most 1.1kW/kg (power) which is very insufficient for the hover power (2.7kw/kg). For the required hover power, it needs around 270 wh/kg energy density (just look at the graph).

For a current battery that meets the required Power density over Energy density requirements it needs a factor of around 8.4, hence an energy density of only 200 wh/kg;- closed to half of that required to meet the performance promised.
https://voltaplex.com/samsung-25r5-18650-battery-inr18650-25r5.

How can 400 of Europe’s top engineers miss this ? Remember Liluim are telling their investors that it’ll be in commercial service in three years from today.

There’s more in Lillium 7 seater report which is of a highly dubious nature as well;- L/D, disc loading, noise, not to mention the Liliuim’s mystery of a lack of transition demonstration.

the specific energy density is mentioned only for the cells and pack density is hidden in the structure weight, battery companies with lower TRLs are given as reference, some of the references of the battery companies are taken down, mass fractions are taken from Bacchinis paper, which dont really align which GaTech's Brian German, Rob MacDonalds paper, no real drag breakdown...
It's a sizing paper, which is ok to publish, but it doesnt have the quality of a research paper from academia or Joby.
In addition: more professors name on your paper dont give you more credibility.
 

Grey Havoc

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Hanwha System is also investing in Urban Air Mobility (UAM), or flying vehicles that will provide transportation in urban areas in the future. THe company sees synergies between its UAM investment and LEO investment.

“Our communications space will be expanded by enhanced satellite connectivity, which means that, for example, we can enjoy a steady stream of digital contents onboard airplanes including UAM, or we can control autonomous flight airframes like drones by using the satellite connectivity,” Choi said.
 

AeroFranz

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nice article:

especially this quote:
As opposed to some companies who were raking up hundreds of flights and saying very little (e.g. Joby Aviation) or flying a lot and talking a lot (e.g. EHang), Lilium was sometimes considered to have a “big mouth” — making wild claims that it seemed unlikely to be able to back up.

finally some technical paper also

direct link: https://lilium.com/files/redaktion/refresh_feb2021/investors/Lilium_7-Seater_Paper.pdf

The Great Lilium Ponzi Scam continues;-
So, I read the attached report a week or so ago and outwardly it looks pretty impressive. However the devil is always in the detail and their claim on battery power density/energy density looked odd. Normally these two properties are mutually exclusive. So, naughty me, I followed up the detail;- reference on page 25: "The cell family introduced by Shirk and Chinh (2020), demonstrates that a constant specific power beyond 2kW/kg can be achieved with eb ≈ 300W h/kg". That's wrong, just look at page 3 of the referenced data:
the graph shows that @300 wh/kg (energy) you can get at most 1.1kW/kg (power) which is very insufficient for the hover power (2.7kw/kg). For the required hover power, it needs around 270 wh/kg energy density (just look at the graph).

For a current battery that meets the required Power density over Energy density requirements it needs a factor of around 8.4, hence an energy density of only 200 wh/kg;- closed to half of that required to meet the performance promised.
https://voltaplex.com/samsung-25r5-18650-battery-inr18650-25r5.

How can 400 of Europe’s top engineers miss this ? Remember Liluim are telling their investors that it’ll be in commercial service in three years from today.

There’s more in Lillium 7 seater report which is of a highly dubious nature as well;- L/D, disc loading, noise, not to mention the Liliuim’s mystery of a lack of transition demonstration.
I finally got around to reading the paper. A few notes:

- The paper did not have Lilium support, they were not given official specs so this is a reverse-engineering effort. So there is some margin for error from the get go.

-First big item that should raise eyebrows: "For all of our assessments we take the cell based energy density as an input
parameter, as Lilium assumes the structural modules of the battery cells will be part of the empty aircraft structure.
"
This is very weird. The industry standard is to take the specific energy at the cell level, and then apply a hefty penalty due to the containment system and the battery management system required to regulate battery operation and protect from thermal runaway, and only then you get the specific energy at the battery level. The penalty could be anywhere between 15% to 40%. Whatever figure ends up being used, it's substantial and cannot be ignored. If you lump this into the airframe structure, fine, but then the empty weight of the vehicle should reflect this.

-Hover thrust calculations are for T/W = 1.0. In reality you will be using higher power levels for station keeping in gusts, and in hover-climb

-This brings us the discharge rate of the battery (so called "C-rate"). The quoted numbers lead to a discharge of 8.42C (this at T/W = 1.0), which is a very high number. This in itself wouldn't be bad, if not for the fact that all things equal, batteries with high C rate have lower specific energy, which makes their claims of 320 kw.h/kg at the battery level even harder to justify.

-The range is based on a minimum state of charge of 10%. The reason is that you seriously affect battery life if you go below this number. What i haven't seen, is consideration for the fact that you may only get to use 90% of the nominal battery when the battery is new. Most other companies will apply an additional 85% factor on top of this to take into account the fact that your battery may be at it's "end of life" (EOL).

-As @Zoo Tycoon mentioned, and L/D of 18.26 seems on the high side. They gain something by not having vertical surfaces, but take on quite a risk IMHO by getting rid of rudders, if only for backup.

-Not surprising, but based on the numbers of the paper, the vehicle has a discloading of 243 psf.
 

Zoo Tycoon

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Thanks AeroFranz, I agree on the points you raise.

Apart from the rather odd note “no private funds were used”in its production, I’m struggling a bit with this;-

- The paper did not have Lilium support, they were not given official specs so this is a reverse-engineering effort. So there is some margin for error from the get go.

Even upon re-reading it I’m not picking up where this is in the paper;- the reports author uses a Lilium business address so would seem to be a Lilium employee.
 

AeroFranz

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Even upon re-reading it I’m not picking up where this is in the paper;- the reports author uses a Lilium business address so would seem to be a Lilium employee.
that's what happens when you skip to the technical portion of the paper! :p
Now that you pointed it out i see it. I only saw the university affiliations at a first glance and missed the Lilium employee. Instead i took the caption in figure 1 - " All data is based on estimates from company data in the public domain"- to mean there was no proprietary information being used.

edit: looking at the list of authors under the title, as i said above, i hadn't paid much attention.
But now that i've taken a good look at it i must say it's odd. Indeed, the author is a Lilium employee and the other five names are not authors but "reviewers". It's like the whole point of this paper was to get academia experts to agree on Lilium's claims. They must have been tired of being questioned and also needed to allay investor's fears. I wonder how successful they will be. AvWeek has been reporting their claims without questioning them too much, so i'm guessing they will be at least partly successful.

As far as I'm concerned, having someone whose name is preceded by a "Dr." or "Prof" isn't good enough. You can cherry pick sympathetic reviewers or simply people who have not spent the last eight years designing these types of vehicles. A lot of what goes into the design of UAM eVTOL vehicles is subtle, with a lot of second order effects that have to be taken into consideration. People in Academia who specialize in, say, hydrogen powered airliners, or some other unrelated vehicle type, are not going to be relevant.
Also curious that none of the reviewers are from TU Munich, the Alma Mater of the founders. TUM is known for its aircraft design expertise.

I can tell you just about every UAM company must have reverse-engineered Lilium's vehicle as part of the normal competitor analysis. Granted, Lilium pivoted to a slightly different mission type (long-range regional), but no other company has felt the need to copy any part of their design.

Who knows, maybe in five years i'll be eating crow. Right now i feel like this is just another misleading and likely successful attempt to keep the money grab going.
 
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VTOLicious

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As said before, with an appropriate landing gear I could imagine that Lilium's "Jet" evolves into a useful STOL aircraft. However, 150 kts cruise speed is not very impressive and rather typical for a helicopter than a jet.
 

AeroFranz

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To reinforce the point made above about batteries, and the reduction factors that have to be applied in order to find out how much actual energy you can use for a given mission, the picture below comes from a recent Electra.aero webinar.
This is more typical of what a design study would use when sizing batteries (this might actually be skewed a little bit because Electra uses a range extender gas turbine, so they'd rather exaggerate the penalties of batteries...). The truth is probably somewhere between hat Lilium says and what Electra says.

1618694791051.png
 

Zoo Tycoon

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Aero Franz - Nice chart illustrating what the electrical aeroplane designer is really up against. I’ve seen this on one of my projects a few years back;- “what!, we’re left with how much?” Although the chart may skewed a bit (the factors look familiar), it still doesn’t include some of the real world additional power demands such as anti ice.

Also you’re spot on about the small complex interactions, potentially with big impacts which are only really found when undertaking real world design;- the devil is always in the detail.

The fundamental issue with electric propulsion is its still marginal. The pundits that predicted a moors law type (doubling every five years) battery improvement have thus far been proved wrong. Flying and particularly vtol, is both energy and power hungry. So the only viable schemes are those which efficiently use the what little is available. Jets while looking cool, are very inefficient at low speed so no other honest eVTOL company is giving them the time of day, QED.
 
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Reaper

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Also curious that none of the reviewers are from TU Munich, the Alma Mater of the founders. TUM is known for its aircraft design expertise.
Because none of the founders actually studied at Institute of Aircraft Design of the TUM and the head of the institute is one of their biggest critics.
If you lump this into the airframe structure, fine, but then the empty weight of the vehicle should reflect this.
In comparison Joby has 235Wh/kg with the comment added that even this number is deceptive since a lot of battery systems and structure are integrated.
 

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AeroFranz

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Also curious that none of the reviewers are from TU Munich, the Alma Mater of the founders. TUM is known for its aircraft design expertise.
Because none of the founders actually studied at Institute of Aircraft Design of the TUM and the head of the institute is one of their biggest critics.
Wow. Just wow.
 

Zoo Tycoon

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Here’s Lilium’s SPAC investors pack;-


And here’s a pretty accurate assessment of it;-


This has the potential to kill off the whole eVTOL business.

(The sixteen seater seems to have about the same wing area as the seven, yeah right as if that’ll fly)
 
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Reaper

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Also curious that none of the reviewers are from TU Munich, the Alma Mater of the founders. TUM is known for its aircraft design expertise.
Because none of the founders actually studied at Institute of Aircraft Design of the TUM and the head of the institute is one of their biggest critics.
Wow. Just wow.
My feeling is that they didnt have an aircraft designer on board from the beginning, which would be helpful.
 

coanda

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Another horror:

View: https://youtu.be/5oiWtYLA-Go


When will we have breathalyzers mandatory for drafting tables?
View: https://media.giphy.com/media/DsdVe5jhHWNC8/giphy.gif
 

dannydale

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Another horror:

View: https://youtu.be/5oiWtYLA-Go


When will we have breathalyzers mandatory for drafting tables?

EDIT: Also why does the camera angle *carefully* keep the foldy bits edge-on when they articulate? ████ing annoying!
 

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Rhinocrates

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So, where on the spectrum of enthusiasts starting to swim out of their depth, through dreamers who think engineering design comes after illustration,* to 'But wait! We also have a bridge to sell you!'?

*Let's call that a type of solipsism. They think that only what they see is real and all they see are boardrooms and PowerPoints.

By the way, an architect's joke: An architect is someone who thinks that conception precedes erection. Engineers probably know a version of that one too.
 

Charlesferdinand

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Another horror:

View: https://youtu.be/5oiWtYLA-Go


When will we have breathalyzers mandatory for drafting tables?
That is what you get when you watch too much Transformers as a kid.
 

dannydale

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Another horror:

View: https://youtu.be/5oiWtYLA-Go


When will we have breathalyzers mandatory for drafting tables?
That is what you get when you watch too much Transformers as a kid.
Nah, even Transformers wouldn't touch this s███ with a thirty nine and three quarter foot pole!
 

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Zoo Tycoon

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Prop down wash;- all eVTOL are going to have them (watch to the end to understand just what these can do);-

View: https://youtu.be/ObfdLy-QlsU


The problem increases with mass and disc loading. Remember although lighter the Lilium has an even greater disc loading than the V22.
 
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