[HN Gopher] Technology Behind the Lilium Jet
___________________________________________________________________
Technology Behind the Lilium Jet
Author : dnst
Score : 103 points
Date : 2021-12-22 16:31 UTC (6 hours ago)
(HTM) web link (lilium.com)
(TXT) w3m dump (lilium.com)
| SkyPuncher wrote:
| If you work at Lilium, you need to make some tweaks to your
| website. This was an incredibly frustrating experience, to the
| point that I gave up.
|
| * Scroll jacking - looks pretty, impossible to use.
|
| * Cookie consent - It's both too large and takes to long to find
| the right action.
| hagbard_c wrote:
| I never saw any cookie prompt since I block _cookiebot.com_.
| Things seem to work just as good /bad without it, try blocking
| that domain and see if it works for you - not just on this site
| but all others which use these "services".
| Centmo wrote:
| I was a core engineer in a different manned eVTOL project, so
| have spent a lot of time thinking about this technology and
| watching the space. Lilium raised some eyebrows recently with
| their SPAC IPO valuation of over $3B, without having released
| footage of a single manned flight. The prototype is unique and
| aesthetically appealing, but my engineering mind recoils at the
| complexity of the design. The variable pitch blades, the
| adjustable exhaust nozzles, the tilt-wing vectored thrust system,
| etc. With complexity comes cost, maintenance, and exponentially
| increasing failure modes. Safety is paramount in aviation, so all
| flight-critical failure modes require redundant backup systems,
| which further increase cost and complexity. It's a slippery
| slope.
|
| The eVTOL space is currently seeing a Cambrian explosion of
| different design concepts, but the first to see economic
| viability I think will be the simpler ones.
| anonymouse008 wrote:
| > The eVTOL space is currently seeing a Cambrian explosion of
| different design concepts, but the first to see economic
| viability I think will be the simpler ones.
|
| Mind expanding a bit on this? And curious where you are now
| instead of this space... is it because you see the tech too far
| out?
|
| My original interest began with the SkyCar 400 from Moller. The
| same design theory of a lot of eVTOLs today; just with a petrol
| motor. The petrol motor reduced responsiveness of the control
| system, but I always thought it would work out in software.
|
| eVTOLs are wonderful, but I think any eVTOL without a 'hot
| swap' battery is going to be DOA in terms of the personal
| transport revolution.
| Centmo wrote:
| I ended up moving on for personal and geographic reasons,
| nothing to do with the tech. The tech is all there for short-
| haul flights with batteries as the only limiting factor for
| range and speed.
|
| There are various paths to economic viability for an eVTOL
| aircraft but I don't see how Lilium's current prototype fits
| into any of them. Unlike an ultralight design, it will
| require a certified pilot to chauffer passengers around until
| the day when full automation moves into the aviation space.
| Other than selling as an extravagant toy, this limits it to
| air taxi service. The design is complex so will be very
| expensive to buy and to maintain, so I don't see it as an
| improvement over existing helicopters beyond the 'green'
| energy source and claimed lower noise.
|
| I am familiar with the Moller SkyCar. Lots of promises were
| made and broken, and lots of money burned on that project.
| Many modern eVTOL concepts suffer from the same basic design
| flaw: forward flight hanging from small propellers is
| inefficient. If you care about range, you need the lift of a
| large airfoil. Moller also had stability issues, but the
| responsiveness of electric propulsion and the advances in
| IMUs have solved this problem.
|
| I think you can have a viable eVTOL product without a hot-
| swappable battery in the same way that electric cars have
| shown.
| semi-extrinsic wrote:
| Meh.
|
| The US is somehow singularly incapable of implementing decent
| public transport. Thus venture capitalists are throwing stupid
| amounts of money at exotic technology that could potentially
| alleviate some of the problems arising from this stupidity.
|
| First we had the "full" self-driving cars and robotaxis coming
| any day now. Then there's Musk's attempts at tunnel digging and
| Hyperloop that have gone nowhere. And now eVTOLs that will go
| nowhere.
|
| It's kinda fun to watch from afar though.
| dsego wrote:
| Don't worry, EU has money to throw around on stupid projects
| as well. Even worse, it's public money.
|
| https://seenews.com/news/croatias-rimac-to-get-200-mln-
| euro-...
| semi-extrinsic wrote:
| Oh sure, and countries in Asia as well, we don't hesitate
| to join in on these things.
|
| I'm just saying, if you trace these ideas back to their
| original motivation, it's the lack of decent public
| transport in California specifically and the US generally.
| kiba wrote:
| Roads required public money to build though.
| kiba wrote:
| _The US is somehow singularly incapable of implementing
| decent public transport. Thus venture capitalists are
| throwing stupid amounts of money at exotic technology that
| could potentially alleviate some of the problems arising from
| this stupidity._
|
| With trains you don't need self driving cars!
|
| Rather, why don't we imagine a differently configured
| society? If you have streetcar suburbs, then it's possible to
| have a lot of last mile delivery delivered by light rail.
| Animats wrote:
| The whole thing hinges on battery energy density more than
| anything else. The planning document says 20 seconds of hover
| at landing, with a 60 second reserve. The demo flight has 45
| seconds of VTOL mode/hover at landing. That's cutting it close.
| You don't get a second chance at landing. No go-around.
|
| Regard this as a bet on improved batteries. With current
| batteries, it's a nice demo.
| jhgb wrote:
| Sounds basically like the Apollo lander...only today we have
| better computers and control systems.
| semi-extrinsic wrote:
| Yes, and it's a bet they will probably lose, if they really
| need 500 Wh/kg in three years time. Their battery graph is a
| fairytale at best.
|
| The current state-of-the-art batteries that researchers build
| in laboratories that last 10-20 cycles can put out about 400
| Wh/kg. You're simply not going to achieve first a 20%
| improvement over that, then a development of the tech to
| increase lifetime to something useable, and then scaling that
| to widespread commercial availability, within three years
| time.
| joering2 wrote:
| This was my take as well - and was wondering what is Fig. 11
| based off of? We can predict, but we don't know how the
| market for batteries will form in the next decade or so. I.e.
| the COVID disturbed all sorts of markets bad enough that
| price of many commodities went up X-fold and haven't gotten
| down yet.
| spacecity1971 wrote:
| Agree re simplicity. Ehang has been using what is essentially a
| consumer drone design for some time, and has demonstrated
| success with many flight tests. Although they aren't using the
| most efficient design, I wouldn't be surprised if they dominate
| the short range air taxi field.
| aj7 wrote:
| Exactly. And a seven-seater gets to pay for this.
|
| The V-22 was how many years late? How many billions over
| budget?
| walrus01 wrote:
| when you say "simpler", do you mean something somewhat more
| conventional that is a multi-rotor/tilt-rotor design like the
| joby evtol?
| Centmo wrote:
| From a safety perspective (ignoring cost, though which is
| also critical for viability), I mean minimizing the number of
| 'Jesus bolts' in the design - single components that if they
| fail, you are in a world of trouble. In the Lilium for
| example, what if the tilt mechanism for one of the main wings
| locks up while in cruise, and you only discover this while
| coming in for a vertical landing? This could be due any one
| of many possible reasons: SW bug, electrical failure,
| mechanical failure, debris jamming the mechanism, etc. You've
| got one wing producing forward thrust and the rest producing
| vertical thrust which is not likely to end well. You need to
| either prove that every part of this particular system is
| extremely reliable or you need a redundant backup system in
| place. Due to the design, neither of these options are easy
| here.
|
| Obviously you need to assume there will be motor-out
| situations in any eVTOL design and the system needs to handle
| this with full payload over the flight envelope needed for a
| safe landing. Lilium has the advantage of many propulsion
| systems to take over the lost thrust, but many other eVTOLs
| are questionable here.
|
| The same thinking has to be applied throughout the entire
| aircraft design (electrical and mechanical) and then you need
| to test, test, test. Each failure mode, using full payload
| over the full flight envelope, stability testing under
| differing weather conditions, the list goes on. To give you a
| rough idea, having a flying prototype is great but once you
| are comfortable enough with the design to put in a test pilot
| under controlled, monitored, and ideal conditions, you are
| maybe 20% of the way towards something you can responsibly
| put into service. If you want to see a simple design, check
| out the Opener Blackfly.
| papertokyo wrote:
| Is an airframe parachute essentially a requirement for a
| vehicle like this to be viable?
| Centmo wrote:
| It certainly increases the safety factor, but should
| never be relied upon as the sole redundant backup system.
| There are situations where it will not do you any good
| such as hovering at low altitude. If the aircraft does
| not have a reasonable glide slope, most people would feel
| a lot more comfortable with one.
| aj7 wrote:
| More cost.
| rayiner wrote:
| One of my senior projects in college was designing a ducted
| lift fan UAV. One of the things that was apparent from digging
| through the old research was the monstrous total complexity
| even of conceptually simple designs that had 1-2 ducted fans
| embedded in the body or wings. Computers make the complexities
| of controlling these things tractable, which was a much bigger
| problem in the 1960s. But even with relatively modern
| technology e.g. Lockheed has had a hell of a time with the
| F-35B.
| madengr wrote:
| [deleted]
| textcortex wrote:
| There is one fundamental error in this blog; the battery energy
| density graph. Battery tech does not follow Moore's law.
| Batteries are not transistors..
| aidenn0 wrote:
| "Simple by design, there are no ailerons..." then goes on to
| describe a vectored-thrust control scheme consisting of
| essentially 36 blown elevons. Clearly we mean something very
| different by the word "simple."
| conradev wrote:
| I know very little about aerospace, but from a manufacturing
| perspective it seems like having a single part or unit that you
| need to manufacture and test would be simpler
|
| but I imagine that this offloads complexity to the flight
| control software, though - is that what you are referring to?
| GravitasFailure wrote:
| Moving to an electric ducted fan instead of an internal
| combustion engine with a variable pitch propeller definitely
| simplifies things, though replacing that ICE and prop with 36
| ducted fans mounted to elevons seems like you're just
| swapping one set of complexities for a different set, though
| gaining complexity through redundancy isn't really the worst
| thing.
|
| My biggest concern with this system is what kind of glide
| ratio this has in a power loss scenario.
| skykooler wrote:
| It's fly-by-wire. Uncontrollable in a power loss scenario.
| null0ranje wrote:
| My biggest concern is how you maintain directional control
| in a power loss scenario.
| aidenn0 wrote:
| ballistic parachute?
| GravitasFailure wrote:
| Maybe. Not sure I've seen one that will work on a 7
| seater, especially with the extra mass of batteries.
| Tuxer wrote:
| There is a ballistic chute on the cirrus SF50 (their
| single-engine jet). It's a 7 seater IIRC (6 minimum), and
| roughly the same weight (2.7T for the cirrus, 3.1 for the
| lilium).
| bewaretheirs wrote:
| Design for hot-swap batteries, and eject the batteries
| (with their own smaller chute or chutes)?
| GravitasFailure wrote:
| Forgive me if I don't consider dropping lithium batteries
| from several hundred meters up a safety feature.
|
| A parachute on this system is a lot of extra mass to
| compensate for a problem solved when the Wright brothers
| were around.
| aidenn0 wrote:
| I mean will a 7-seater helicopter autorotate sufficient
| to provide control in a power-loss situation?
| GravitasFailure wrote:
| That too. As far as I can tell, this thing has all the
| control and glide capabilities of a brick. At least the
| brick has the inherent safety feature of not being
| mistaken for a passenger aircraft.
| Centmo wrote:
| A way around this risk is to come up with a design for
| which a total power loss is extremely unlikely (i.e. it
| would take multiple simultaneous non-correlated failures in
| a short span of time). This could be achieved through a
| distributed battery system where each motor has its own
| battery physically and electrically separated from the
| others, and critical flight electronics have their own
| backup batteries. A ballistic parachute is always nice as a
| last-resort hail mary.
| GravitasFailure wrote:
| Redundancy does go a long way, but that also introduces a
| lot of extra weight and complexity into an already heavy
| aircraft and can screw with your weight distribution.
|
| The parachute can work since there are ones for air
| dropping tanks, but at the same time I'm not sure I've
| seen anyone try to use a parachute as safety equipment on
| an aircraft this heavy.
| Centmo wrote:
| Agreed, the distributed battery system does not seem
| practical for the Lilium design but you could get at
| least part way there by segmenting the central battery
| into parallel modules with separate safety disconnects.
| Not sure about the feasibility of the parachute system,
| it may be impractical due to the aircraft weight as you
| mention.
| faeyanpiraat wrote:
| Would it be enough for the safety batteries at the motors
| to be only as big as to provide power for the aircraft
| for an emergency landing? Like for a 30 sec full thrust?
|
| That might not bother the weight distribution that much.
| samstave wrote:
| "It's simple! We KILL the Aileron!"
| mysterydip wrote:
| "The landing gear is fixed and there are no hydraulics."
|
| Will this cause issues during landing? I've seen helicopters land
| and it can be a bumpy/sketchy experience.
| kwhitefoot wrote:
| That's a very unconvincing video clip on that site.
|
| Here's a better one: https://www.youtube.com/watch?v=5ukmS9ZJm40
| Dunedan wrote:
| Note that the video you linked doesn't show their latest
| "demonstrator". Here is a video of their latest one:
| https://www.youtube.com/watch?v=jqvMXoVZfDw
| beaconstudios wrote:
| why are all these new variants of sport aircraft appearing at the
| moment? There must be something in the water because I've seen so
| many re-interpretations of the flying car in the past year or
| two. They look cool in movies but how are they at all a practical
| method of transportation outside of being toys for the ultra-
| rich?
| qzw wrote:
| I think everyone is trying to replicate the Tesla formula where
| the first Roadster was a toy for the rich, then followed by
| real products and now $Trillion in market cap. But there are a
| few steps in there that are probably hard to copy, like being
| able to sell carbon credits to other manufacturers, federal tax
| credit for buyers, etc. Oh, and one Elon Musk.
| HPsquared wrote:
| Electric cars have increased the availability of mobile
| electric power systems: experience with batteries, motors,
| controllers etc in cars is transferable to aircraft. It's "in
| the air" so to speak.
|
| Edit: Also the mass market adoption of small quadcopters; these
| "distributed electric propulsion" flying car type things are
| basically the same concept: flight control by altering the
| speed of an array of propellers.
|
| Also a lot of university teaching/research on both of the
| above.
| Dunedan wrote:
| One of the main backers of Lilium is Frank Thelen
| (https://en.wikipedia.org/wiki/Frank_Thelen), a VC from
| Germany, best known for his participation in the German version
| of Shark Thank ("Die Hohle der Lowen").
|
| He seems to believe that eVTOL are the future of mass
| transportation, like an airborne version of taxis. I personally
| don't find that plausible at all, but maybe I'm just not
| creative enough to imagine a future where this would work.
| beaconstudios wrote:
| I really hope that's not the case. Mass transit that's just
| cars that are even more noisy and can drop on people from the
| sky?
| fh973 wrote:
| Be aware that you are usually looking at prototypes, not
| available products.
|
| Currently its mostly another set of startups to invest in. They
| might look attractive to VCs because they're ambitious, require
| lots of capital, and the technical feasability of a specific
| approach is complex enough to find merits in. The jury is still
| out if any of them are actually viable from a technology and
| economic perspective.
|
| Lilium's approach specifically has been publicly critized by
| aviation experts to not be make sense when looking at the basic
| physics.
| brightball wrote:
| I could see these being a more cost effective option than
| helicopter transport. Especially in island areas.
| kensai wrote:
| Lilium, as I see it, has by far the most secure design of all air
| carrier designs we have seen recently. And there have been a lot
| including some really nice!
|
| Lilium is the only company going for this distributed propulsion
| system with so many rotors, adding the the safety of the whole
| thing. Safety should be paramount! A couple of deadly accidents
| can literally ground a fleet otherwise.
|
| Volocopter also tries a similar approach, but the lack of eVTOL
| probably makes that bird much slower than the Lilium product.
| fh973 wrote:
| However, Volocopter seems to be further with their product
| development, while there are serious doubts if the Lilium
| concept works at all.
| _Microft wrote:
| What do you mean that their concept might not work at all?
| They have flown several iterations of their prototypes
| already but maybe you have something different in mind, e.g.
| doubts about the possibility to scale the concept up?
|
| Here are videos of recent test flights:
|
| https://www.youtube.com/watch?v=0idI3sJJKZw
|
| https://www.youtube.com/watch?v=SqMEFdbuzQY
|
| https://www.youtube.com/watch?v=jqvMXoVZfDw
| AeZ1E wrote:
| Cool, but the event is not unmannedly flying around in a
| circle for 1 minute but to transport up to 7 people over
| several hundred miles.
| antoniuschan99 wrote:
| It's all unmanned unfortunately. Still waiting for them to
| demo at least a dummy payload like Joby did a few months
| back.
|
| Also, Joby, Ehang, and Volocopter are much further ahead in
| the sense they have done point to point or are building out
| the factory (same time last year Ehang got hit by being
| called a scam by Citron, however).
|
| From what I read, rumor is the big issue is battery density
| which is holding Lilium from being viable. We shall see!
|
| Also, Joby is most likely the one to look at to track the
| progress of this air taxi segment since they have just
| Spac'ed and their aircraft is the most conventional.
| KentGeek wrote:
| From those videos, it's difficult to be sure those are full
| size prototypes and not scale models.
| mrfusion wrote:
| How do the engines point down for take off?
| w0mbat wrote:
| I am not at all an expert in this field, but is "jet" the right
| word?
|
| I thought that required combusting fuel and using the flaming
| exhaust to propel something. This is propellors in tubes.
|
| Also this vehicle is about a third of the speed of what most
| people think of as a "jet plane".
| nickff wrote:
| 'Jet' has been used to describe many different types of
| propulsion system. The first jets were what you'd call rocket
| engines. Then we got 'turbojets' (mostly on aircraft), followed
| some time later by 'turbofans'. Most confusingly, ducted
| propellers on submarines are called 'pump-jets'.
|
| I would agree with you that this seems better-described as a
| ducted fan (which the author also says), but this use of 'jet'
| is not beyond the pale.
| divbzero wrote:
| Jet propulsion involves ejecting a jet of fluid [1] and does
| not require combustion of that fluid.
|
| [1]: https://en.wikipedia.org/wiki/Jet_propulsion
| Karliss wrote:
| There is also waterjet and jet stream. Not uncommon dictionary
| of jet is narrow,forceful stream of fluid or the nozzle
| producing it. Taking that into account difference between jet
| and propeller in tube is matter of speed and compression. It's
| just that fuel combustion is one the most practical energy
| sources including for producing jets of gas.
| HPsquared wrote:
| Interesting stuff. Haven't heard of the Lilium specifically, but
| have seen other distributed electric propulsion concepts here and
| there. DEP is such a nice idea, eliminating a lot of the problems
| with helicopters/fixed wing aircraft (noise, space requirements
| etc.) to carve out a new category of aircraft that is perfectly
| suited to an emerging technology (high energy density batteries).
|
| If we ever do get flying cars, they will use distributed electric
| propulsion.
| dmitrygr wrote:
| "fifth evolution of our technology over our six year history"
| reads: "it still doesn't work, we aren't sure if it can, but need
| more investor cash"
|
| Their rosy projections of how they expect battery systems to
| magically materialize and double in density over the next few
| years to make this device actually work are also quite funny.
| aj7 wrote:
| "So, the Lilium aircraft requirements can be summarised as
| follows...
|
| *High seat capacity to achieve attractive unit economics and
| affordable pricing over time"
|
| devolves to
|
| "Yes, we are building a 7-Seater!"
| rikeanimer wrote:
| This paper "Electric VTOL Configurations Comparison" [
| https://www.mdpi.com/2226-4310/6/3/26/pdf ] presents a pretty
| decent energetic analysis of a few of these eVTOL projects
| (including Lilium) and is _very_ generous to them.
|
| Lilium is vaporware. Ask anyone who has worked in the space. Or
| just look at it. Or their promotional materials.
|
| Ducted fans huh... meh. I don't think they have an interest in
| people understand how fly-y/hover-y things actually work.
|
| I do applaud the investors for their vigorous desire to increase
| the velocity of money throughout society, it is important
| econometrically. Somehow I doubt they'll be happy to see their
| currency shredded by 36 rc brushless motors struggling to thrust
| an anemic wing into the sky though (before its glorious ~250km/h
| cruise to destination [of course])--and then ~15s landing hover.
|
| What exciting times to fly in.
| rickreynoldssf wrote:
| What Brilliant Web Designer thought it was a good idea to pulse
| the text? Are you trying to give me a seizure? SMH WTF
| kevincox wrote:
| And that 2px per full spin of the scroll wheel ensures I really
| had time to absorb the content.
| Timothycquinn wrote:
| I've been watching this space for quite a long time and this
| company seems to have the engineering and backing to make it
| happen. From a safety perspective, this design has a potential
| for massive redundancy over several other designs being promoted
| out there.
|
| Considering that their marketing is not to desperate, and their
| releases of footage is slow and stead, I predict that they are
| very confident in their designs.
|
| If I had a few million to throw around, I would definitely be
| investing in this company.
| djrogers wrote:
| These are som pretty impressive goals. If they can truly achieve
| a hover state as quiet as 60db, and get the efficiency they've
| outlined, these could truly change the way we look at short-haul
| travel.
|
| The idea of a 2 hour drive from a small town to the big city
| being reduced to a 1hr flight (with no airport - yay helipads) is
| already a market where helicopters are making money. Doing that
| in even less time, in more comfort (ugh - choppers are loud), and
| at lower cost per hour/mile will change things dramatically.
| axiosgunnar wrote:
| How is 2h to 1h any ,,revolution"? And wouldn't simple (bullet)
| trains be better for that?
| orangepurple wrote:
| New train lines won't be built ever again in the United
| States
| dragonwriter wrote:
| > New train lines won't be built ever again in the United
| States
|
| New train lines are being built now in the United States.
| renewiltord wrote:
| There's construction ongoing on new train lines in the
| United States. Whether they're being built is up for
| debate.
| deepnotderp wrote:
| A small town doesn't have the density for a HSR link, see eg
| China's HSR debt.
|
| A 120 mile link at 14 million a mile is more than a billion
| dollars.
| loudmax wrote:
| A bullet train is better if there's one that already happens
| to go from your location to your destination. If they manage
| to make these VTOL planes safe and cheap enough, they'll be
| far easier to deploy than any train system. Also while
| there's overlap between short haul aviation and train
| markets, the infrastructures don't have to be mutually
| exclusive.
| bostonsre wrote:
| Yea, 60 decibels at 100m would be pretty crazy to achieve.
| avidiax wrote:
| 60dB @ 100m is 77db @ 15m
|
| For comparison, in Washington state, the legal limit for an
| automotive exhaust is 72db@15m.
|
| Still an achievement, but definitely not something you want
| your neighbor to land at 3 am.
| wmf wrote:
| Obviously aircraft are louder than cars. It seems like this
| should be compared to a helicopter since it uses the same
| pads.
| ananonymoususer wrote:
| Can we please use dBa (a measure of absolute sound pressure)
| rather than dB (a relative term used in many domains)?
| fh973 wrote:
| It might actually be too good to be true. The German magazine
| Aerokurier is citing experts that seem to have doubts about
| feasibility [1].
|
| The category is called air taxis, other competitors are
| Volocopter and Archer, with different concepts.
|
| [1] https://topgear-autoguide.com/category/sports-
| car/futuristic...
| gibolt wrote:
| Experts always have questions about disruptive technology.
|
| They are often not right, since disruptions are not
| incremental change, but tons of nuanced ones that lead to a
| significantly better overall system.
|
| Edit: "Often" does not mean always, or the majority of the
| time. Lilium is clearly not a scam, and seems to be making
| steady progress towards their goals.
| chefkoch wrote:
| ...but physics isn't something that cares If you want to
| disrupt.
| hn_throwaway_99 wrote:
| I think this is such an important point to differentiate.
| Yes, incumbent experts can be caught flat-footed when a
| new technology comes along that is essentially just _much
| better_ at what they do. Best example in my mind is the
| iPhone, where essentially the big old-school cell phone
| execs totally poo-poo 'ed Apple's ability to create a
| compelling cell phone in 2008: "A computer company
| doesn't know what they're doing."
|
| But that is fundamentally different than pointing out
| real physical limitations of an idea, and the danger is
| you get exactly the OP response, "The old guard always
| dismisses you until you change the world!" yada yada.
| This is basically _exactly_ what happened with Theranos -
| anyone in the actual field of microfluidics knew it was
| all bullshit.
| wmf wrote:
| Of course, but it seems like the gap between what is
| physically possible and what has been demonstrated is
| pretty large when it comes to aircraft. Has anyone made a
| specific argument that Lilium violates the laws of
| physics?
| kiba wrote:
| How energy efficient is this concept? Can't this air taxi
| thing be done with better public transport and urban
| design?
| rayiner wrote:
| > Experts always have questions about disruptive
| technology. They are often not right
|
| They're usually right, because most technology that seeks
| to be disruptive doesn't end up working.
| RandallBrown wrote:
| My take was actually the opposite. I can't see this changing
| anything.
|
| Since this thing won't be able to take off from my driveway or
| land at my destination, I figure it will still take 2 hours to
| go door to door. Once you arrive, you'll still need your own
| transportation too.
|
| Unless this is somehow cheaper and more comfortable than
| driving, I can't imagine ever using something like this.
| akrymski wrote:
| Why not use hydrogen instead of heavy batteries?
|
| Why not use jet engines instead of propellers?
| twp wrote:
| What is missing from this blog:
|
| Where is the safety margin? i.e. what happens if something goes
| wrong? Can the aircraft make a safe landing if the motors fail?
| Do the limited control surfaces give it enough maneuverability to
| make an emergency landing in a tight field, especially in bad
| weather?
|
| tl;dr great blog, thank you for the technical insight, it sounds
| like you've designed Lilium for a perfect world. Popular aviation
| needs to have basic safety margins and there are no safety
| margins evident here.
| samstave wrote:
| Multiple questions for aerospace folks here:
|
| Why are designs with multiple wings no longer developed, not just
| bi/tri wing planes with wings stacked, but why aren't their rows
| of smaller wings, or multiple wings? Do the vortices of the trail
| of a leading wing fuck up themlift potential on wings behind it?
|
| ---
|
| We simple golf balls for greater distance through the air, and
| Wales see an advantage to the barnacles that grow on the leading
| edge of their flippers which have shown to create eddys behind
| the tail edge of the flipper which aids in greater vortices and
| greater propulsion..
|
| Why don't we dimple wing surfaces? Or plane bodies?
|
| Or helicopter blades?
|
| What happens when we simulate the leading edge barnacle bumps on
| the leading edge of a wing, or more aptly, the leading edge of a
| blade on a helicopter?
|
| What software is used to model the airflow over a wings surface,
| such as solid works...
|
| --
|
| How much overlap is there between fluid hydro and aero dynamics?
| (Specifically the observation of the impact to flow/eddy creation
| over a surface?)
| gfody wrote:
| I always loved the look of Burt Rutan's dragonfly, there's a
| list of issues mostly related to conventional (non-vtol) flying
| - https://www.nestofdragons.net/weird-
| airplanes/tandemwings/qu...
| dmitrybrant wrote:
| Off topic, sorry, but: Why do web designers think that they can
| provide a better _scrolling_ experience than the default system
| behavior that the user expects in every other interaction?
|
| By the way, hijacking scrolling behavior often breaks other
| things, such as searching for text in a page. Go ahead, try it,
| search for a term in that article.
| aidenn0 wrote:
| I hate scrolljacking too, but to answer your question,
| overriding the default system behavior in general isn't about
| providing a _better_ experience but rather a more consistent
| (from the POV of the designer) experience.
|
| The downside of course is that it looks less consistent with
| other apps and webpages from the user POV.
| fikama wrote:
| I just wanted to add that scrolling works normal on mobile.
| Including searching. It's only loading a bit too long.
| tailspin2019 wrote:
| I was about to say that it's quite smooth for me on Safari -
| then I searched for something as per your suggestion and the
| whole page was vertically offset and effectively broken... oh
| dear.
|
| Edit: The scroll hijacking makes more sense in the context of
| the home page, which actually uses it to reasonable effect (not
| endorsing the technique, but the home page is attractive at
| least).
|
| I think the mistake was leaving it on for heavy content pages
| like the one linked where it adds very little but breaks other
| basic behaviour.
| skykooler wrote:
| It's quite smooth with a trackpad. With a mouse scroll wheel,
| it's basically non-functional.
| [deleted]
| systemvoltage wrote:
| The sexier the blogpost, the less believable it is for me. Make
| this page in Times New Roman or Computer Modern typeface,
| preferably in a PDF format, and I am automatically convinced
| :-). It just means that they have better things to do than
| aesthetics!
| tommoor wrote:
| Yea, it's atrocious on this article - makes it unreadable tbh
| as scrolling muscle memory is completely messed up.
| AeZ1E wrote:
| Can we make sustainable public transport attractive again - an
| stop hyping gadgets for the rich?
| oh_sigh wrote:
| Lilium Jet has 600 employees. What do you think they could
| contribute to sustainable public transport that the millions of
| people employed across the globe directly involved in public
| transport can't do?
| mrshadowgoose wrote:
| Those are not mutually exclusive endeavors.
|
| Please be aware though, that there's always going to be a large
| population segment that will desire to proceed directly from
| point A to B in comfort.
|
| Unless by "public transport" you're including "government owned
| autonomous taxis", public transport will never be attractive to
| that population segment.
| OnlineGladiator wrote:
| > Please be aware though, that there's always going to be a
| large population segment that will desire to proceed directly
| from point A to B in comfort.
|
| How large do you consider this population segment to be?
| sokoloff wrote:
| Order of magnitude as large as the group that commutes by
| car today.
| [deleted]
| mrshadowgoose wrote:
| Quite large, certainly a good chunk of the population that
| currently drives. There's also a segment of the public
| transit riding population that would prefer personal
| transit, but do not have the option.
|
| People generally prefer to a) be comfortable, and b)
| proceed directly from point A to B with no interstitial
| bullshit.
|
| You almost never get b) with public transit as commonly
| realized today.
| Maarten88 wrote:
| A high-speed train can connect inner cities just as fast as
| this gimmick jet. It is orders of magnitude more efficient
| and scalable, and much more safe. A good train could easily
| be more comfortable, if there is a market for that. Do you
| think that jet will have dining rooms, sleeping cabins, ample
| room for luggage? Do you think it will even have a toilet?
|
| Just. Build. A. Train.
| mrshadowgoose wrote:
| High-speed trains are awesome. We absolutely should be
| building more of them for the people who'd like to use
| them.
|
| But if someone wants to go directly from point A to B in a
| "gimmick jet", why should we try to prevent that?
|
| I'll reiterate with your example. Building high-speed
| trains, and developing "gimmick jets" are not mutually
| exclusive endeavors. It's clear that you are not personally
| interested in a "gimmick jet", but there are people who
| would be. Why exactly should we be stopping those people?
| natechols wrote:
| I like trains too (and short-haul aircraft frighten me),
| but it's much easier to find an unobstructed path for a
| small aircraft than a high-speed train. There's also more
| latitude for experimentation with these piecemeal private
| sector experiments. I would expect a high-speed rail line
| between San Jose and San Francisco, for example, to cost
| far more than Lilium's current market cap. I'm not even
| sure where you'd put the track, without killing an existing
| train line.
| thescriptkiddie wrote:
| Not only is this company obviously a scam, if their product
| actually did exist it would be extremely expensive as well as
| louder and more dangerous than a regular helicopter.
| AeZ1E wrote:
| What a useless startup
| Timothycquinn wrote:
| What gives you this impression? They have amazing engineers and
| huge backers. My impression is that they are one of the most
| likely to succeed in this space.
| AeZ1E wrote:
| They won't be able to deliver on their spec. Not even close.
| https://www-aerokurier-
| de.translate.goog/elektroflug/lilium-...
| orangepurple wrote:
| After reading your article I came to one conclusion: RUN,
| don't walk from Lilium. They are obviously tricking people
| who don't know a single thing about airplane engines.
|
| Lilium responded to the aerokurier article on Monday with
| an email in which our experts were accused of having set
| the hover efficiency of the drives far too low with an
| efficiency of 20 percent. Lilium, on the other hand, claims
| that values "of 85-95% are the industry standard for turbo
| fan levels". According to Lilium, this mistake should have
| been noticed by any industry expert.
|
| Lilium is right with regard to the efficiency of turbofan
| engines viewed in isolation, as they are standard today on
| all high and fast flying airliners. However: There are no
| turbo fans installed on the Lilium Jet. They are jacketed
| propellers driven by electric motors.
| icefox11 wrote:
| That is precisely the problem: believing that one can succeed
| in this space. Flying personal transport is not economical.
| On a side note, it doesn't matter how brilliant an engineer
| is if you set impractical goals to him. Neither good
| engineers not deep pocketed backers could make Theranos real.
| deepnotderp wrote:
| And why are you so certain that flying personal transport
| is not economical?
|
| Certainly the history of the automobile should show that
| such statements can look ridiculous in hindsight.
| rmah wrote:
| He's certain because of energy budgets, weight
| constraints, safety reasons and more. The history of the
| automobile vs aircraft shows he's right.
|
| To move something in the air inherently uses more energy
| than any sort of ground transport. To make the aircraft
| more efficient, you have cut weight, which means more
| exotic (i.e. expensive) materials. The powerplant has to
| have a higher power:weight ratio (again more expensive).
| It's more dangerous to be flying, so you need additional
| safety equipment that ground vehicles don't need. Etc,
| etc.
|
| And if any aviation technologies manages to gain
| price/performance better than the stuff used for ground
| transport... it will be adopted by ground transport.
| Which still leaves air transport more expensive for the
| reasons listed above and many others. Hell, in WW2, they
| stuck an aircraft engine into the most common US tank
| (sherman). Interestingly, sherman tank crews didn't have
| to worry about falling out of the sky and dying if their
| engine failed (though they had lots of other worries, of
| course).
|
| Long story short: there is nothing magical about electric
| motors turning propellers. And battery energy density is
| utterly horrible vs gasoline/kerosene. Air transport will
| ALWAYS be more expensive than ground transport. Perhaps
| someday it will be cheap enough to be common. But
| personally, I doubt that such a day is anytime soon.
|
| Last aside... You can buy a small used two or four seater
| plane NOW for < $100k. Get a pilots license and you can
| fly around to your heart's content. General passenger
| aviation today is not reserved for the ultra rich.
| karmicthreat wrote:
| I don't doubt this concept could ferry people around. But its
| safety margin is razor thin. 60s reserve? That is barely time for
| an operator to figure out where to ditch.
| Ancapistani wrote:
| If I'm reading it correctly, they're claiming 60s of reserve
| _at hover_. That would translate to roughly 10m of reserve in
| level flight.
| sokoloff wrote:
| On a windy day or two, I've done multiple go-arounds in a
| fixed wing aircraft. In low weather, missing an approach to
| land is also relatively common.
|
| "Don't worry, your pilot has 60 seconds of reserve with which
| to land safely" is terrifying rather than reassuring.
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(page generated 2021-12-22 23:00 UTC)