[HN Gopher] Feasibility of a Dune Ornithopter
___________________________________________________________________
Feasibility of a Dune Ornithopter
Author : HiroProtagonist
Score : 223 points
Date : 2021-10-23 00:25 UTC (22 hours ago)
(HTM) web link (pages.erau.edu)
(TXT) w3m dump (pages.erau.edu)
| Animats wrote:
| Drone-sized ornithopters have become reasonably flyable outdoors.
| But scaling works against you. One the size of a large
| helicopter, capable of vertical takeoff, is tough. Mostly a power
| problem, like all VTOL.
|
| Dune, like much of SF, runs on Rule of Cool. The skilled knife
| fighter, even shielded, is vulnerable to many of the standard
| anti-riot weapons, such as projectiles which throw a net. Being
| hit by an RPG round with a solid warhead would at least knock
| someone down hard, despite shielding, from sheer momentum
| transfer. And tanks work just fine in the desert, as has been
| amply demonstrated in the Middle East all the way back to Patton.
|
| [1] https://www.youtube.com/watch?v=IJA5C-ghj4s
| thrower123 wrote:
| This might be from the later Brian Herbert books, but I recall
| ornithopters having jets or thrusters for VTOL.
| Animats wrote:
| Thrust-based VTOL requires huge amounts of engine power.
| Which is why it's rarely seen on anything other than
| fighters, which are mostly engine anyway.
|
| There were some exceptions in the 1940s and 1950s, when jet
| engines didn't quite have enough power to get aircraft up to
| flying speed quickly. There were some attempts to use rocket-
| assisted takeoffs ("RATO" or "JATO") during WWII, and by the
| 1950s, this worked reasonably well. This peaked with the B-47
| bomber, which was basically a jet fighter scaled up to heavy
| bomber size. Here's a JATO-assisted B-47 takeoff.[1] And
| here's a jet fighter zero-length takeoff from a rack on the
| back of a truck.[2] That was pushing it; there were a lot of
| crashes.
|
| Awesome, but impractical, the technology was discarded in
| favor of aircraft with enough main engine power to get off
| the ground on short runways.
|
| Another dead end was the Avro-Car, which was supposed to be a
| VTOL for the Army. This is the famous flying saucer.[3] It
| was supposed to be a supersonic VTOL. It had nowhere near
| enough power for that, and could barely get out of its own
| ground effect. Plus it was unstable, although today it could
| probably be stabilized automatically. The prototype finally
| ended up at what's now NASA Ames, bouncing around the back
| lots in hovercraft mode. The U.S. Army was also funding the
| UH-1 helicopter, which was less awesome, but far more useful,
| so they cancelled the Avro-Car and ordered lots of Hueys.
|
| If you like weird VTOL craft and are in Silicon Valley, visit
| the Hiller Aviation Museum. Many of those strange ideas from
| the 1950s ended up there.
|
| So, using a booster to get a large ornithopter off the ground
| is, while not impossible, probably not something you'd do
| often. Although you could imagine some fortress having such a
| rig, so the leaders could escape when they were losing.
|
| [1] https://www.youtube.com/watch?v=vKQYG_fA2uM
|
| [2] https://www.youtube.com/watch?v=uxazX7Z_4iQ
|
| [3] https://en.wikipedia.org/wiki/Avro_Canada_VZ-9_Avrocar
| Andrew_nenakhov wrote:
| The baron was flying by himself, so in that universe they
| definitely had other ways to generate lift but trust-based
| propulsion.
| dragonshed wrote:
| Suspensors aren't really used for thrust, but as a way to
| augment or nullify the effect of gravity on an object.
|
| In the books, the kernel of fictional science used for
| multiple effects, including suspensors which is what the
| Baron uses, is called the Holtzman Effect [1]. The movie
| doesn't mention it at all, but the depictions of
| suspensors with all the massive vehicles, as well as
| floating furniture, glow globes, etc, are all consistent
| with how the books describe them.
|
| [1] https://dune.fandom.com/wiki/Holtzman_Effect
| Andrew_nenakhov wrote:
| I didn't say 'thrust', I said 'lift', and suspensors did
| lift the baron. It could be used to lift ornithopters as
| well, so it could, you know, flap wings for propulsion.
| arpa wrote:
| trust != thrust, just so you know.
| Andrew_nenakhov wrote:
| Tell it to autocorrecting keyboard on my android.
| arpa wrote:
| That's what happens when you put your trust in
| autocorrect: you lose all the thrust ))))
|
| I've turned off the autocorrect, and now I get all kinds
| of stupid touch interface mistypes, and lose time over
| correcting them, but at least i'm not miscorrected all
| the time.
| Andrew_nenakhov wrote:
| the most infuriating thing is that autocorrect sometimes
| inputs a correct word, but THEN changes in to another
| when you continue typing. Aaaargh. That is further
| complicated by my dependence on swipe-typing on
| smartphones. It works 98% of the time, but the remaining
| 2% might come out embarassing :(
| lrem wrote:
| TFA is citing jets from the original Dune novel.
| yoz-y wrote:
| Mainly if they are going to fight with medieval weapons but
| with force shields, they should be wearing medieval armor. That
| combination would make them much less mushy.
| jimnotgym wrote:
| >And tanks work just fine in the desert, as has been amply
| demonstrated in the Middle East all the way back to Patton.
|
| Tanks were being used to great effect by Rommel (and less
| successfully by others) for a long time before Patton graced
| the desert! In fact the battle of El Alamein where Rommel was
| severely pushed back was well underway when Patton landed. The
| Western Desert war began in mid 1940, Patton landed in late
| 1942.
|
| As my companion poster noted, none of this was against sand
| worms though
| ceejayoz wrote:
| > And tanks work just fine in the desert, as has been amply
| demonstrated in the Middle East all the way back to Patton.
|
| Probably not against sand worms.
| phendrenad2 wrote:
| And not for covering long distances to where the spice is...
| kortex wrote:
| Tanks are no weapon of choice. The rhythmic nature of the
| slats in the tank treads as it drives will surely attract a
| worm. Heh, they'll never learn.
| gilbetron wrote:
| Worth posting just because it is still a fun watch:
| https://www.youtube.com/watch?v=XQ7z57qrZU8
| jon-wood wrote:
| Tanks do work fine in the desert, but if they were rumbling
| along on tracks they'd quickly attract sand worms and be
| swallowed. I imagine suspensor propelled tanks would be similar
| since in the novels force fields will attract worms from far
| and wide, much more so than just rhythmic noise.
| skhr0680 wrote:
| > Being hit by an RPG round with a solid warhead would at least
| knock someone down hard, despite shielding, from sheer momentum
| transfer.
|
| Have you ever seen Elysium?
| [deleted]
| aj7 wrote:
| I've often wondered the exact opposite. Could thrust turbines
| evolve naturally?
| kleer001 wrote:
| as feasible as any other tech in Dune, shields, laseguns, space
| folding, genetic memory, etc...
| aaron_m04 wrote:
| And stillsuits.
| walrus01 wrote:
| giant floating guild navigators in tanks of spice that resemble
| wrinkled testicles? as per the 1984 film
| noisy_boy wrote:
| I just realized that several AWS icons[0] always remind me of
| the guild navigtor's tank[1] due to their "protruding-front"
| shape.
|
| [0]: https://imgur.com/a/RnK3e9C
|
| [1]: https://imgur.com/a/yc00FNz
| Ansil849 wrote:
| ...but apparently not as per the 2021 film. Seriously, where
| did the guild navigators go in the Zendaya version?
| Monroe13 wrote:
| I think we saw guild navigators with the emperor's envoy on
| Caladan. White-suited creatures with a red swirling gas
| behind their visors.
| walrus01 wrote:
| Perhaps the CGI testicle budget was spent on salary for
| Jason Momoa instead
| est31 wrote:
| The first scene of the 1984 movie does not exist in the
| books, even though they were depicted correctly. In fact,
| they didn't appear directly in the original Dune book at
| all, and they were only described in later books of the
| series (Both the 2021 and 1984 movies are adaptations of
| the first book, the 2021 one adapting the first 75% ish).
| carapace wrote:
| SPOILER ALERT
|
| Two Guild Navigators are in the Emperor's party on
| Arrakis when he confronts the "upstart duke". They are
| not mutant freaks, they look like normal humans, but
| their eyes are so blue from spice use that they appear
| black.
|
| The weird fish-baby in a tank is all David Lynch being
| David Lynch.
| elihu wrote:
| Actually, that wasn't an invention of David Lynch. It was
| just something sort of pulled in from the second book.
| est31 wrote:
| I looked up that part. Indeed there are two of the "guild
| agents, one tall and fat, one short and fat" as part of
| the entourage, and they are referred to in the text as
| Guildsmen. Paul asks them if they are both navigators and
| they reply with yes. And yeah they are revealed to have
| blue eyes, so I think this is correct. However, later
| books do describe the tanks in which the navigators live.
|
| The dune wiki says that Herbert apparently liked how the
| navigators were depicted in the movie so he added their
| description to his last Dune book "Chapterhouse Dune".
| But even earlier books described the guild navigators as
| humanoid fish in a tank.
|
| Apparently the explanation for these different forms is
| that there is a progression, where the guild navigators
| start out looking like humans, and eventually they look
| like the two in the Lynch movie.
|
| https://dune.fandom.com/wiki/Guild_Navigator#Physical_Des
| cri...
|
| So what I said about the navigators not appearing at all
| was wrong, as they do appear in the first book, but they
| appear only way later in the story.
| carapace wrote:
| Ah, much respect est31. Well met. :)
| PeterisP wrote:
| IIRC spacing guild did try to keep their mutated
| navigators appearance secret from the general public, so
| having some normal-looking guild agents say "we're
| totally the navigators" does not really mean that they
| actually are navigators.
| shazeubaa wrote:
| There's mention of "stages" of navigators in one (or
| more?) of the books. Stage 3, as I recall are the
| advanced form in the tank.
| adolph wrote:
| _Original inception dates back to Leonardo da Vinci, but it is
| not until recently that we have been able to achieve these flight
| characteristics on small scales._
|
| I wonder what is meant by recently.
|
| _The first ornithopters capable of flight were constructed in
| France. Jobert in 1871 used a rubber band to power a small model
| bird._
|
| https://en.wikipedia.org/wiki/Ornithopter
|
| I think the work would also be improved by a mention of bio-
| inspired work on the PRANDTL-D wing.
|
| _The Armstrong team (supported by a large contingent of NASA
| Aeronautics Academy interns) built upon the 1933 research of the
| German engineer Ludwig Prandtl to design and validate a scale
| model of a non-elliptical loaded wing that reduces drag and
| increases efficiency. The team also applied these concepts to
| improve propeller blades._
|
| https://technology-afrc.ndc.nasa.gov/featurestory/prandtl-wi...
| pvg wrote:
| For some reason I'd mostly seen Penaud's model in popular
| accounts but googling Jobert landed me at a site that has a
| bunch of illustrations from _Progress in Flying Machines_
| (1894) that shows what they all looked like. Jobert 's first:
|
| https://invention.psychology.msstate.edu/i/Chanute/library/p...
|
| And the whole lot:
|
| https://invention.psychology.msstate.edu/i/Chanute/library/P...
| phendrenad2 wrote:
| Leonardo da Vinci's designs weren't ornithopters, or even
| anything like real birds. They were fixed-wing gliders with
| fanciful bat-like shapes for stylistic reasons.
| bryanrasmussen wrote:
| >They were fixed-wing gliders with fanciful bat-like shapes
| for stylistic reasons.
|
| My understanding is they were commissioned by playboy
| Milanese nobleman intent on bringing down the Borgia crime
| family, whose parents had been knifed down in an alley in
| front of him when still a child after exiting a wonderful
| setting of the Magnificat composed by Gaffurius.
| ccozan wrote:
| Wait, is this the _original_ Batman origin story?
| Gravityloss wrote:
| If you construct a fabric+wood ribs wing, it will easily look
| bat-like. Many early airplanes were like that too.
| telesilla wrote:
| Reminds me, where or when can I buy a robobee?
|
| https://m.youtube.com/watch?v=hEZ7rHRifVc
| pharmakom wrote:
| I always thought Dune had lower gravity, would also explain how
| the worms work.
|
| Also note there is low gravity tech. Maybe it's a hybrid.
| KineticLensman wrote:
| > I always thought Dune had lower gravity, would also explain
| how the worms work.
|
| On page 79 of 'Dune' (my 1973 paperback copy), when the
| Atreides soldiers first land on Arrakis, a group of them 'shout
| and roister' as they disembark. One of them says 'Nine-tenths
| of a G by the book'. Another says 'Feel that under your dogs?
| That's gravity, man.'
|
| So not massively different from Earth-normal. Not sure if is
| this enough to affect the feasibility of a winged craft (or
| sandworms). On that note, air pressure would also affect the
| feasibility of winged vehicles, as in the difficulty of trying
| to fly a (small) helicopter on Mars.
| smoldesu wrote:
| Not a huge Dune lore-head, but I kinda feel slighted by how the
| new movie depicted them now...
| BEEdwards wrote:
| I disagree, I liked the dragonfly inspired ornithopter.
|
| Maybe not as originally envisioned, but I like the aesthetic.
| jcun4128 wrote:
| I did like how they look like helicopter blades and it is
| built like a gunship/AH64 style. The gliding stuff was like
| hmm... also generally as a side note, giant things would sink
| through the ground like the opening ship landing oh well.
| craftinator wrote:
| > Maybe not as originally envisioned, but I like the
| aesthetic.
|
| I think you'll find that you've identified the target market
| for almost all modern film adaptations of science fiction
| novels.
| edmundsauto wrote:
| Doubly true if the elided part of the quoted section is
|
| > Maybe not as (I) originally envisioned, but I like the
| aesthetic.
|
| I am guilty of this in every book to film adaptation I've
| ever seen.
|
| (Also - book sales / movie audience ratios will almost
| always necessitate generalization.)
| [deleted]
| yoz-y wrote:
| I might have misheard, but aren't they also referred to as
| "jetflies" in the chase scene? That is a bit more apt name
| for this particular design.
| m0llusk wrote:
| It is more complicated than that. The book is vague though
| colorful on many points, so there is considerable room for
| interpretation. On several points in the book ornithopters are
| described as bug like, buzzing when active, and having bug like
| buzzing wings. The evocative version in the movie is consistent
| with one particular interpretation of what the book was
| depicting.
| kebman wrote:
| Here's a fun and working model aircraft powered by articulated
| flight: https://www.youtube.com/watch?v=ysnAVwtdbYc
|
| Things that strike me off the bat for creating "the real thing:"
| Ground effect with rising heat, helping with lift. Longer and
| lighter wingspans made out of special exotic materials that is
| incredibly durable, flexible and easy to articulate, perhaps with
| a "muscular" system. Much stronger, lighter and tuneable
| machines. Systems or mechanics preventing compartment shake. I
| think this is probably the most difficult part in order to
| achieve comfortable flight. The part of a bird best evolved to
| counteract this movement is the head, since they need that as a
| stable platform to observe the world despite the rest of the body
| moving.
| jcun4128 wrote:
| Yeah this guy makes these things like everyday. Recently using
| direct servo drive is interesting.
| carapace wrote:
| One of the interesting details not mentioned in the book (it's in
| either one of the appendices or in the Dune Encyclopedia) is that
| the wings are powered by muscles, not engines. It's an aspect of
| the minimal use of technology in that Universe.
| sandworm101 wrote:
| I wouldn't say a minimal use of tech, more that they use very
| mature tech. Mature tech 'just works' with minimal intrusion or
| maintenance. I think of it like home heating systems. Once we
| all had fires or stoves as central objects in houses. Now we
| have a switch on a wall connected to a system that can go years
| without maintenance. Sure, there is an entire industry behind
| the scenes and some debate the benefits of one tech over
| another, but the average user only ever sees the switch. So the
| ornithopter's engines have been replaced by electromechanical
| muscles because they probably go decades without need of
| attention.
| carapace wrote:
| You're right that the technology they use is very mature, but
| anti-machine stigma is a definite "thing" in the Dune milieu,
| blowback from the Butlerian Jihad. At one point Reverend
| Mother Gaius Helen Mohiam says something to the Lady Jessica
| about the difficulties of working with a feudal culture that
| has "turned it's back on most technology", something like
| that.
|
| Ornithopter muscles are not electromechanical, they're
| organic.
| superkuh wrote:
| >blowback from the Butlerian Jihad.
|
| Which itself is a reference to Samuel Butler's 1872
| satirical novel "Erewhon" which featured a culture that had
| banned all complex machines due to an experience with
| machine intelligences revolting.
| https://en.wikipedia.org/wiki/Erewhon
| sandworm101 wrote:
| I think the language re "machines" in the Dune context
| refers more to thinking devices, computers, than to
| mechanization.
| hutzlibu wrote:
| True, but allmost all of our modern machines need lots of
| thinking devices to work.
| sandworm101 wrote:
| I see lots of calculators that can execute programs
| (CPUs). I see lots of software that is great a pattern
| recognition or trend analysis (AI). What I haven't seen
| are any devices actually thinking through a problem.
| hutzlibu wrote:
| Depends how you define thinking. I used it in that
| calculations are "thinking" work.
| addingnumbers wrote:
| That seems uncomfortably close to claiming every Turing-
| complete device is artificial intelligence.
| carapace wrote:
| Well, Turing was formalizing something that his mind was
| doing, so in a sense, yes, Turing Machines have always
| been AI.
| carapace wrote:
| That's the origin and emphasis of the Butlerian Jihad,
| for sure, but it seems to me that there's a more general
| disdain of machines in the galactic culture. Although
| they certainly do use a lot of machinery: shield
| generators, poison snoopers, spaceships, etc. so maybe
| not.
| PeterisP wrote:
| On the other hand, in Dune universe we see all that weird
| machinery used by a very unusual part of the society, the
| top 0.01%; and even they're not a product of the
| societies they live in but an import from the partially
| shunned Ixian community - so we can presume that the
| ordinary people don't make or use machines nearly as
| much. E.g. there are some instances of complex
| electronics, but it seems like most planets e.g. Caladan
| would have near-zero electronic industry, it doesn't seem
| that this would be a career option for some random
| inhabitant of Atreides' home planet to just decide to
| study electronics and make them.
| tait wrote:
| Did anybody else find the changing tab title annoying?
| joecool1029 wrote:
| Pretty sure the author did it as a troll, in which case it's
| great, I hate it.
|
| > <!-- Javascript to make dat scrolling title SON! -->
|
| ^ comment on it
| snet0 wrote:
| But.. why? Am I out of touch to not see the humor here?
| Annoying the people who you intend to read your posts?
| brundolf wrote:
| I thought it was neat and wasn't really bothered. Though I'm
| not really sure what it's supposed to depict
| willhinsa wrote:
| What comes to mind to me is a sandworm coming out of the
| ground, and pulling something back down underneath with it.
| ganzuul wrote:
| It was interesting to see the update rate of background
| tabs.
| vadfa wrote:
| I miss the days of quirky title bar "animations".
| _Microft wrote:
| The German industrial control and automation company _Festo_ [0]
| created a bionic swift [1] as an engineering demo this year. The
| flapping wings are no longer as rigid as in their earlier
| flapping bird model [2]. Go and check out their other stuff (e.g.
| a dragonfly: [3], a flying fox or aquatic animals), it 's great!
| Here is a Youtube search for _Festo Animals_ for your convenience
| [4].
|
| [0] https://en.wikipedia.org/wiki/Festo
|
| [1] BionicSwift: https://www.youtube.com/watch?v=hUE8o056Cpc
|
| [2] SmartBird: https://www.youtube.com/watch?v=nnR8fDW3Ilo
|
| [3] Dragonfly: https://www.youtube.com/watch?v=nj1yhz5io20
|
| [4] https://www.youtube.com/results?search_query=Festo+Animals
| elihu wrote:
| Reminds me of Tyrell Corporation:
| https://www.youtube.com/watch?v=VSOzdFoZsho
| tunnuz wrote:
| Do you like our owl?
| k__ wrote:
| A friend of mine lives a few cities from a Festo factory.
|
| She didn't know what they build, but she always said the name
| Festo sounds like being an evil corp in a scifi story.
|
| She was a bit shook, when I told her about the robots, haha
| aj7 wrote:
| My friend, the late Michael Polatnick, coined a word to
| describe your friend. "Stupido."
|
| Festo got big making pneumatic devices and grippers, parts
| that are used in almost every automated factory. And almost
| every mechanical engineer involved with mechanisms knows of
| Festo.
| dvh wrote:
| How does that make you feel?
| audiometry wrote:
| Let me tell you how it makes me feel.
| einpoklum wrote:
| This is very impressive. However - is there not a problem of
| scale? As you scale, surface area is squared, but mass is
| cubed. I mean, ok, you could have a lighter central fuselage,
| but then how effective can this be in carrying passengers or
| cargo?
| _Microft wrote:
| Planes aren't filled solidly, though. They are more like a
| shell around a volume, so I'd think the mass would rather
| scale like the surface area than the volume of the plane.
| Beside that, I would agree that it seems impossible to get
| such a solution working in dimensions of dozens of meters. A
| pun: maybe they just took "do things that don't scale" too
| literally? ;)
| lugged wrote:
| Bigger wings?
| Sharlin wrote:
| Bigger wings means heavier wings, and greater torque needed
| to actuate the wings, which means more power needed as well
| as greater stresses involved, all of which means even more
| mass, which eats into your payload budget.
| walrus01 wrote:
| human powered ornithopter:
| https://en.wikipedia.org/wiki/UTIAS_Snowbird
| b0rsuk wrote:
| > This state of constant, high magnitude stress, leads to a very
| short fatigue life for the structure.
|
| So maybe the wings should be living? Nature seems to have
| perfected automatic repair.
|
| > This is currently not possible, and it will never be attempted.
|
| There's a novel by Jack Vance which works around the technical
| difficulties by having a low gravity planet, and descendants of
| colonists use material from the outer parts of the spaceship. So
| there's very limited supply of this space tech substance, and
| wings are passed from generation to generation.
| nabla9 wrote:
| The idea that what works for insects or small birds should work
| in larger scale if you just have materials does not hold up.
|
| Small insect wing aerodynamics is closer to high viscosity
| aerodynamics. Viscous forces are more important and efficacy of
| lift generation from an airfoil is less important. Air can be
| considered incompressible.
|
| Reynolds numbers (Re) - orders of magnitude. 10^7
| for helicopter main rotor 10^4 for large insects 10
| for small insects
|
| Helicopter rotor aerodynamics is in laminar flow region limited
| from above buy the transonic region. Airfoil lift is the most
| important thing and laminar flow is important.
|
| Insect flight is mostly turbulent flow. Generating enough lift
| using leading edge vortex and half strokes like insects do for
| helicopter sized object and rotor sized wing is not self evident.
| At least the wings should be much larger than helicopter rotors
| and flap very slowly.
| Sharlin wrote:
| Yeah. For insects, flying really is more like _swimming_. Air
| has very different properties at that scale.
| underscore_ku wrote:
| RC Ornithopter https://www.youtube.com/watch?v=2Nd8BA3OHCc
| dumdumdumdum wrote:
| Somewhat similar: https://www.youtube.com/watch?v=ZCrS52sM3Zs
| rosetremiere wrote:
| Wow, I love those "concrete tiles". Any idea where this is?
| phkahler wrote:
| I had a rubber band powered bird over 35 years ago. Looked a lot
| like this:
|
| https://youtu.be/GqWkctx3Z2I
| elihu wrote:
| I remember those. I don't think elementary-school-aged me ever
| got mine to fly properly.
| elihu wrote:
| I just watched the new movie today; it's good. The dragonfly-like
| wings were an interesting choice. It seems like they'd be less
| efficient at lift than a jointed wing, but then I thought, maybe
| an unusual wing surface material could be used?
|
| The problem is that when the wings go up, they're pushing air in
| the wrong direction and propelling the ornithopter down. But
| suppose the wing was covered in tiny little hinged flaps that
| close on a downstroke, but open on an upstroke? That way the
| upstroke would push the aircraft down much less than the
| downstroke lifts.. (These wouldn't even need to be controlled in
| any way, they could just be passive flaps. Though being able to
| lock them closed might be useful for certain acrobatic
| maneuvers.)
| carabiner wrote:
| Yeah, it's horribly inefficient to do this (flapping wings) at
| larger sizes. Birds, bats, insects actually evolved to flap
| less as they get larger:
| https://www.researchgate.net/figure/Wingbeat-frequency-versu...
|
| A condor with a 10-ft wingspan might not flap for _hours_ - so
| it glides, just like an airplane:
| https://www.sciencealert.com/giant-andean-condors-can-fly-fo...
|
| A hummingbird (4 inch wingspan) flaps at 60 Hz though. It can
| hover too, just like an insect.
| k__ wrote:
| By that data we already build our planes like birds.
|
| If a 10ft bird flaps its wings less than once an hour a plane
| sized bird would probably fly for days without flapping its
| wings
| trhway wrote:
| >A hummingbird (4 inch wingspan) flaps at 60 Hz though. It
| can hover too, just like an insect.
|
| during hover hummingbird doesn't flap the wings up/down,
| instead it flaps it in horizontal plane. On each stroke, back
| and forward, the wing is set at an angle of attack and thus
| is kind of like propeller during each flapping stroke pushing
| air down :
|
| https://youtu.be/naE7fK-gCPs?t=110
|
| Hummingbird weights 3 grams. An APC 4x4 prop at 3000 rpm
| would generate 4 grams thrust consuming 0.2 Watt. Such energy
| density would mean 6 KWt for human, ie. 60x our regular
| power. So no wonder :
|
| https://www.lib.niu.edu/2000/oi000811.html
|
| "Hummingbirds are sugar addicts. Their metabolism is so
| incredibly fast that they need to refuel about every 10
| minutes. Each day they consume 50 percent of their body
| weight just to maintain their normal weight. Hummingbirds
| burn from 6,600 to 12,000 calories per day. If a man had the
| metabolism of a hummingbird, he would have to eat almost 300
| pounds of hamburger a day to keep from wasting away."
| straphka wrote:
| Just so you know, those numbers are way off. If you think
| about it how would a hummingbird consume that amount of
| calories in half its bodyweight? See
| https://www.birdspot.co.uk/bird-brain/how-many-calories-
| do-h...
|
| I mean, when extrapolated to human size it's still 125k
| calories a day, but 6600 for a bird of 3g is just not
| possible.
| vkou wrote:
| They are (deliberately?) juxtaposing calories (the
| scientific unit of energy) and kilo-calories (the
| nutritional unit of energy).
|
| Unfortunately, the latter are, confusingly, also called
| called 'calories', despite one nutritional 'calorie'
| being 1000x of a 'regular' calorie.
| FunnyLookinHat wrote:
| I thought it was accurate - k-cal are usually represented
| as Calories (capital C) as opposed to the individual unit
| of measure: calories.
|
| See: https://en.wikipedia.org/wiki/Calorie
| adrian_b wrote:
| Yes, that must be the source of confusion.
|
| 6000 to 12000 calories, not kilocalories, per day, means
| 1.5 g to 3 g per day of sugar, which is plausible for a
| humming bird.
| alisonkisk wrote:
| Only the "6,600 to 12,000 calories per day." is way off,
| because it's physics cal not nutritional (k)cal.
|
| And it's more like 100lb of hamburger for a human, not
| 300lb.
| chrisseaton wrote:
| 125k calories is about half a chocolate bar. It's not a
| lot.
| alisonkisk wrote:
| It's 125k kcal.
| [deleted]
| fareesh wrote:
| The dragonfly wings were in the video games too I think
| skhr0680 wrote:
| Dune2's ornithopter has bird-like wings. That game had a
| really unique aesthetic
| generalizations wrote:
| You just change the angle of the wing on the upstroke so it's
| slicing through the air. It's not actually a problem. :) Same
| thing real dragonflies and even birds do (though birds fold up
| their wings too).
| ganzuul wrote:
| The fatigue life seems to be the biggest problem next to
| power production. Superelastic alloys might survive though.
|
| If the intuition is some kind of supersonic reverberation
| that lets the wings operate in a local low air density then
| it might not be that hard to find an envelope of lift in that
| regime.
| elihu wrote:
| I kind of assumed that's what actual dragonflies do (I mean,
| they have to get lift somehow), but for a very large wing
| that rotation must cause quite a bit of drag in itself. In
| the movie, the ornithopter wings are maybe 50 to 100 feet
| long and usually moving too fast to see. I would tend to
| assume that the aerodynamics would be different for something
| that huge than an insect, but I don't have any good intuition
| for what would be most efficient. Maybe a combination of wing
| rotation and self-opening flaps would be best? Or a wing that
| splits itself into multiple parallel wings on the upstroke
| and combines into one on the downstroke?
|
| It's interesting that dragonfly wings are so long and thin,
| which I suppose minimizes the amount of drag as they rotate
| between the downstroke angle and the upstroke angle.
| sandworm101 wrote:
| >> the aerodynamics would be different for something that
| huge
|
| With such a large moving airfoil there are inefficiencies.
| Pretending that the wing is a solid object, very quickly
| the tips will be moving faster than the speed of sound. At
| such speeds void/shockwaves start to form, radically
| changing everything. The root of the wing is barely moving,
| the tips are supersonic, and somewhere along the middle is
| a transition zone that moves back and forth depending on
| speed. Good luck designing that airfoil. (This is what
| makes the TU-95 Bear so loud. Its propeller tips are
| supersonic while the rest of the aircraft isn't.)
|
| There is a Russian saying about helicopters: You can place
| every problem in all aerodynamics on the tip of a rotor
| blade.
| cgriswald wrote:
| All these conversations are lacking a discussion about
| the atmosphere on Arrakis. We have only hints about the
| composition and density of the atmosphere. We can assume
| that the atmosphere isn't toxic and contains quantities
| of oxygen and carbon dioxide that make breathing both
| possible and comfortable. We can be sure it doesn't crush
| humans or explode their lungs.
|
| We also don't know the gravity of the planet. It might be
| 1.2g or 0.85g.
|
| So we don't know how much lift is generated per stroke,
| how much lift is required, or what the speed of sound
| actually is on the planet.
| philipswood wrote:
| Ornithopters seem to be an Imperium-wide vehicle and not
| a Arrakis-only device which blunts the urgency of these
| questions and variances.
|
| To be used on many different imperium planets seem to
| imply that it operates across an acceptable range of
| gravities and pressures, etc.
| cgriswald wrote:
| Ornithopter is a type of vehicle. It's unlikely any
| specific vehicle of the type would be generic enough to
| operate across the variety of planets that likely exist
| within the Imperium without modification to the design.
|
| This particular branch of the discussion was focusing
| specifically on the feasibility of the 'dragonfly'
| ornithopters operating on Arrakis as represented in the
| new film.
| adrian_b wrote:
| The problem with the supersonic tips is identical for
| normal aircraft propellers.
|
| For aircraft with fixed wings for generating lift, the
| propellers can be small, so supersonic speed is reached
| only at a higher rpm, but for a helicopter there is no
| difference from this point of view compared with an
| ornithopter.
|
| The blades of a helicopter propeller must also be able to
| rotate along their longitudinal axis, like those of an
| ornithopter, but nonetheless they are more efficient than
| flapping wings, because there is no dead time and no
| energy lost for the reversing motions, and the fatigue
| resistance need not be as extreme as it would be required
| for flapping wings.
| Joeri wrote:
| In the dune universe they have some kind of antigravity
| technology, so perhaps this is used to dampen the
| shockwave at the tips?
|
| In our universe given enough power there is probably a
| way to generate an opposite wave to counter the
| shockwave.
| ben_w wrote:
| But if you have antigravity, why do you need wings?
|
| (Same also applies to having force fields, but the whole
| "slow blade" vs fast blade thing is enough to at least
| handwave that away)
| simonh wrote:
| Possibly cost. But also suspensors only seem to give
| lift, or very small amounts of lateral thrust. All the
| pure suspensor vehicles we see move extremely slowly.
| It's possible the 'thopters use suspensors for primary
| lift, maybe 80% of vehicle weight, and the wings are just
| for manoeuvring lift and thrust.
| jon-wood wrote:
| The aversion to using force fields is more about their
| interaction with laser guns, when shot by one they cause
| an explosion equivalent to a small nuclear weapon. Not
| ideal to have wrapping a vehicle you may be flying in
| formation on an attack run.
| adrian_b wrote:
| In real insects there is no problem with the drag for wing
| rotation, because the rotation is not an active motion, but
| a passive motion caused by the flow of the air.
|
| The insect wings have a rigid front edge, which is moved up
| and down, while the rest of the wing is flexible. When the
| front edge goes down, the rear part of the wing is pushed
| by the air upwards until it assumes a slanted position that
| pushes the air backwards. The reverse happens on the
| upwards beat.
|
| So in most insects only the rigid front edge of the wing is
| moved actively while the rest of the wing assumes passively
| various shapes that are determined by the distribution of
| rigid veins and flexible membranes in the wing, which
| ensure that the shape of the wing is the right one for good
| efficiency.
| [deleted]
| simonh wrote:
| >You just change the angle of the wing on the upstroke
|
| In fact we see that the wing joints can do this in the movie.
| When the wings fold up for deployment, the joint rotates them
| into orientation.
| Sharlin wrote:
| However, momentum _is_ a problem. The vibrations, and thus
| stresses, induced on the body of the thopter must be
| ludicrous. When the wings go up, the body must go down, and
| vice versa.
| adrian_b wrote:
| Actually this can be an explanation for the fact that in
| the movie the ornithopters have 8 wings instead of 4, like
| an insect.
|
| On each wing position there are a pair of wings, one above
| the other. If when one goes up, the other goes down, and
| vice-versa, that eliminates the vertical oscillation of the
| body.
| elihu wrote:
| Interesting, I hadn't noticed that the ornithopters in
| the movie had 8 wings rather than 4.
| Sharlin wrote:
| Good point!
| fnord77 wrote:
| the wings make the craft much wider than a helicopter, plus
| someone could easily walk into them when it is on the ground,
| idling.
|
| wonder why no insects evolved with a rotating wing. rotating
| propulsion exists in nature, though at a microscopic level.
| (flagella)
| rini17 wrote:
| I guess ability to stow wings easily is a big advantage. To
| stow any kind of rotating propellers is problematic.
|
| These ornithopters can certainly stow the wings too, it just
| never came up in the story.
| everyone wrote:
| When I visit that site in firefox the name of the tab keeps
| changing.. A bunch of zeroes getting longer, then shorter. Is
| that some intentional javascript thing??
| jcun4128 wrote:
| Saw same thing in Chrome
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