[HN Gopher] Vacuum airship
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Vacuum airship
Author : guerrilla
Score : 90 points
Date : 2023-07-20 09:24 UTC (13 hours ago)
(HTM) web link (en.wikipedia.org)
(TXT) w3m dump (en.wikipedia.org)
| twic wrote:
| What if you kept the envelope "inflated" using an electric field?
| Make it out of something conducting, insulate the outside, then
| charge it up. Self-repulsion will stop it collapsing. I leave the
| calculations as an exercise for the reader.
| user070223 wrote:
| Though total vacuum is not that attractive, you could mix the
| idea with hydrogen/helium. My question is whether it's being used
| today, and how much would it cost / save
|
| Previous discussion https://news.ycombinator.com/item?id=8170569
| justinclift wrote:
| > His patent application was eventually denied on the basis that
| it was "wholly theoretical, everything being based upon
| calculation and nothing upon trial or demonstration."
|
| The standards for what's considered patentable have certainly
| changed for the worse since then.
| dvh wrote:
| These days it's more like: for x in `cat
| /usr/share/dict/words`; do submit-patent "airship
| filled with $x" done
| dodslaser wrote:
| My airship is full of eels
| glumreaper wrote:
| Outstanding comment! Bound to fly over the head of some in
| HN.
| appplication wrote:
| It's an airship, it's bound to fly over all of our heads.
| Unlike those pesky hovercraft.
| rascul wrote:
| Sorry, I can't help myself.
|
| https://mywiki.wooledge.org/DontReadLinesWithFor
| adolph wrote:
| Oh hai, I see you are building a bike shed. You might
| consider a curl call over to OpenAI for all the
| method/apparatus/etc patent-talk.
| nickpinkston wrote:
| Seems like it's easier to build a fireproof hydrogen design than
| get this right.
|
| Some of these proposed designs use an internal metal honeycomb
| for structural support, but an even lighter weight fireproof
| honeycomb could just prevent hydrogen leaks / oxygen mixing with
| honeycomb walls acting as "fire walls" and also reducing the
| extent of any leaks.
| mywacaday wrote:
| Always make me happy to be reminded to look at myth busters
| https://youtu.be/kM-k1zofs58
| mlatu wrote:
| i think the most promising research is atmospheric ionic
| thrusters.
|
| sure they have little to do with vacuum per se but if you could
| improve them enough to build a sort of cavity with lower pressure
| inside while providing upwards thrust, essentially directing air
| streaming into the cavity whereever you want to direct it to, you
| could both have your cake and eat it. it would be a very good
| insect trap and a highly efficient way to get rid of excess
| electricity quickly. perhaps you could also fix the ozone layer
| with this...
|
| ;)
| nickpinkston wrote:
| This could be like an atmospheric Titan disaster if you get it
| wrong, but at least you could parachute out.
| csours wrote:
| But at 1 bar delta p, not 400 bar.
|
| Delta P means pressure difference. DO NOT GOOGLE.
| BatFastard wrote:
| Could you use a hybrid approach? Put hydrogen gas into a vacuum
| until the pressure the hydrogen exerted would offset the vacuum.
| animal531 wrote:
| I'm busy making an far future airship building management game
| where you have a little crew dropped into orbit of some kind of
| gassy planet, their mission to mine resources from the atmosphere
| and expand their ship, diving deeper and deeper as they pick up
| mass.
|
| I don't want there to be giant gas balloons obstructing the view
| and/or gameplay that's happening, so I'm using a zero point
| module that can keep the ship floating at a given altitude.
| taneq wrote:
| Not to complain about zero-point-module based airships, of
| course, but you could do as the '90s isometric RPGs did with
| houses, and just not render the airships' lifting bodies.
| bshipp wrote:
| Agreed, or only render the bags at full zoom and have them
| dematerialize as you move in for a closer look. That way you
| can easily find the airships on an overview map by their
| large sphere but still be able to micromanage the
| infrastructure as you zoom in.
| Sosh101 wrote:
| I wonder if such a thing is possible with modern materials?
| post-it wrote:
| Probably, but you get a ~15% lift improvement over helium, and
| about half that over hydrogen. The returns are very diminished.
| mkl wrote:
| If you make it big enough, you don't even need the vacuum:
| https://en.wikipedia.org/wiki/Cloud_Nine_(sphere)
| jcahill84 wrote:
| Well that made for a really fun rabbit hole to start my day.
| Thanks.
| https://worldbuilding.stackexchange.com/questions/36667/can-...
| MPSimmons wrote:
| What's interesting to me is that nobody in that thread
| actually used a sphere the size that Bucky proposed.
|
| A sphere with a 1km diameter has a volume of 680,317,581
| cubic yards.
|
| A sphere 1 mile in diameter has a volume of 2,854,543,238
| cubic yards.
|
| The driving mass force per those comments seems to be the
| surface area of the sphere, which grows according to the
| square, but the lifting power grows by the cube.
| dr_dshiv wrote:
| Hydrogen reduces the lifting force of a pure vacuum by less than
| 10% and solves the problem of needing a stronger-than-diamond
| super lightweight shell. So, until you can make a shell with a
| mass less than the total amount of hydrogen, it doesn't make much
| sense.
|
| I'd like to find calculations on the effect of hot/cold hydrogen
| on lift--might be a way to change the lift without releasing
| ballast or gas.
| dcminter wrote:
| I'd been wondering if an aerogel sphere with a mylar coating
| (constructed under vacuum) would be sufficiently low density to
| float - the aerogel would let it resist the pressure and the
| mylar would seal it.
|
| I guess the aerogel would be dense enough compared to hydrogen
| that a conventional balloon would be better in all respects
| though.
|
| Still curious as to whether it's been done already though.
| Scalene2 wrote:
| Making an aerogel sphere in a vacuum would be quite the
| challenge.
| dcminter wrote:
| I mean you need a vacuum to create an aerogel in the first
| place!
| dsign wrote:
| I have done a bit of research on that. I don't think that
| current aerogels are engineered to withstand full atmospheric
| pressure. With that said, the approach would make sense for a
| number of reasons:
|
| - Helium and hydrogen "escape from everywhere".
|
| - Hydrogen burns
|
| - Helium is obtained from natural gas and is rather
| expensive.
|
| An aerogel made from biomaterials (think of a sort of bio-
| engineered coral) could possibly have enough strength and low
| density.
| dcminter wrote:
| I thought the silica based ones were pretty strong under
| compression?
|
| Edit: Wikipedia has a persuasive picture of some aerogel
| supporting a house brick!
| aaron695 wrote:
| [dead]
| harimau777 wrote:
| Isn't the main problem with hydrogen its flammability? Or is
| that something that is exaggerated?
| rob74 wrote:
| According to the Wikipedia article, even using helium only
| reduces the lift by 14%...
| lsaferite wrote:
| Isn't the objective to have livable space though? If the
| space is filled with helium or hydrogen then you cannot
| live in the space.
| WithinReason wrote:
| Filling it with a vacuum however...
| lsaferite wrote:
| Haha. Sorry, I was reading some of the links posted here
| where they talked about using slightly warmer air and
| must have gotten lost.
| lesuorac wrote:
| It's exaggerated.
|
| The problem with hydrogen is that it was involved in a very
| public accident (the Hindenburg). However, only 1/3 of the
| people on it died and they did so on the ground because they
| couldn't escape from the fire [1]. The flammability of
| hydrogen can be mitigated just as the flammability of
| gasoline can be mitigated.
|
| Also keep in mind the Ford Pinto is from 1970 while the
| Hindenburg was from 1930 and the Pinto's failure mode was
| _not unique_ to the Pinto; it was endemic of car designs of
| the time (doesn't mean the Pinto doing that design was smart,
| its just that cars were literally unsafe in any accident).
| Obviously in 50 years we've come a long way with gasoline
| safety; I expect we could make a significantly safer blimp
| nearly 100 years after the Hindenburg.
|
| [1]: https://en.wikipedia.org/wiki/Hindenburg_disaster
| Xylakant wrote:
| There is already a way to change the lift without releasing
| gas: pump the gas into a compressed container - it reduces the
| volume and thus the specific lift.
| TylerE wrote:
| This assumes a flexible envelope. Most airships are rigid.
| Volume doesn't change. Indeed, being rigid is what makes them
| airships and not blimps.
| Xylakant wrote:
| Rigid airships still have flexible gas bags (cells) inside.
| They just have a rigid hull around them.
| WirelessGigabit wrote:
| So 1 kg of Helium in a balloon with a volume of 10cm^3 has
| more lifting power than that 1 kg of Helium in a balloon of
| 5cm^3?
| the_third_wave wrote:
| Lifting power is defined by the mass of displaced medium
| minus the mass of the displacing medium. Change your units
| from cubic centimetres to cubic metres and the answer is
| "yes".
| snewman wrote:
| Yes, although a better way of saying it is that it is not
| the helium which has lifting power, it is the balloon. A
| balloon has lifting power equal to the weight of the air
| displaced by the volume of the balloon. From this, you must
| subtract the weight of the balloon and its contents. Helium
| is one of the few materials that allows you to wind up with
| a positive net lift.
|
| (Also, for this to work, 1kg of helium would occupy a
| balloon much larger than 10cm^3).
| stetrain wrote:
| Yes, like how a 1kg 10cm^3 block of wood will have more
| buoyancy in water than a 1kg 5cm^3 block.
|
| Bouyancy "is equivalent to the weight of the fluid that
| would otherwise occupy the submerged volume of the object,
| i.e. the displaced fluid."
|
| So compressing your lifting gas reduces the amount of air
| being displaced by its presence, reducing the buoyancy.
| scotty79 wrote:
| The helium is only to keep the baloon of given volume from
| collapsing.
| dr_dshiv wrote:
| Such a good way to think of it!
| Xylakant wrote:
| Yes - the latter is more dense by a factor of 8 (2^3) and
| thus has less lifting power.
|
| To take an actual real example:
|
| Air has a weight of 1.222 kilograms/m^3 (dry, clean,
| standard pressure) Helium has a weight of about 0.167
| kg/m^3.
|
| That means that 1m^3 of helium lifts about 1kg. If you now
| compress that helium by a factor of 10, then 1m^3 of
| compressed helium would weigh 1.67kg - more than the
| sourrounding air and provide negative lift.
|
| edit: get your unit and orders of magnitude right. :sigh:
| harimau777 wrote:
| It looks like this sort of thing is already used by
| submarines to control their depth. https://en.wikipedia.org/w
| iki/Variable_buoyancy_pressure_ves...
| csours wrote:
| Now offering $250,000 rides to space on my carbon fiber vacuum
| airship.
| [deleted]
| defrost wrote:
| In fiction
|
| (unmentioned in wikipedia article) There's a golden age of
| science fiction story whose author I don't recall that had a
| story hinging on surviving the crushing pressure of Jupiter's
| atmosphere.
|
| While putting it forward that no material could withstand a
| differential pressure of
|
| (Jupiter pressure XX atmosphere) | (Human necc. 1 atmosphere)
|
| a (fictional) solution was proposed of staggered shells, each
| reducing the pressure by 1 atmosphere (the amount required for a
| vacuum airship).
|
| I'll throw it out there for anyone to chase up or recall the
| story name + author.
|
| This reduction in stages notion is mentioned in the above article
| and it does prompt the question of whether a modern honeycomb
| material could be fabricated as a thick walled shell about a
| ballon shape with interior vacum and pressue reduction staggered
| through the honeycomb.
| Helmut10001 wrote:
| This was in Hyperion Canthos, Dan Simmons! [Edit] after
| checking, it was not Jupyter that Dan Simmons wrote about, but
| the story sounded very familiar. Apologies.
| defrost wrote:
| Good to know, cheers.
|
| Definitely _not_ the story I 'm dimly recalling though as I
| would have read it before 1982 as part of my (until then)
| ever expanding collection of tattered science fiction novels
| and anthologies.
|
| ( First book of the _Hyperion_ series being published in 1989
| )
| bjelkeman-again wrote:
| Something authors often ignore when writing fiction about
| Jupiter is the intense radiation there. You often see
| stories/games about astronauts doing EVA around Jupiter, but it
| is way more dangerous than the Van Allen Belts around Earth.
|
| https://www.esa.int/Enabling_Support/Space_Engineering_Techn...
| defrost wrote:
| Fair point - I do a bit of geophysics and look at ground and
| cosmic radiation so a point appreciated.
|
| That said .. there's always some killjoy dragging reality and
| science into science fiction . . . :-)
| bjelkeman-again wrote:
| True. I love a good story over anything else. But sometimes
| it just seems the writers, particularly for TV are just
| lazy. A few fixes in the script and everything looks a lot
| better. The Expanse is a good compromise IMHO.
| PufPufPuf wrote:
| I recall something like that being described in Larklight by
| Philip Reeve
| yetihehe wrote:
| You can buy small vacuum chambers on ebay. Making a large one
| is also doable. What's problematic is making one lightweight
| enough to be buoyant. When you make staggered one it will still
| have too much mass because all shells will weight as much as
| one thicker shell.
| bakje wrote:
| ChatGPT thinks the story you're referring to is "a meeting with
| Medusa" by Arthur C. Clarke [1]
|
| The plot summary on Wikipedia doesn't mention the staggered
| shells, but it does sound like this might be right [2]
|
| 1.
| https://chat.openai.com/share/476fb915-6037-47dd-8c06-095fd2...
|
| 2. https://en.wikipedia.org/wiki/A_Meeting_with_Medusa
| twic wrote:
| Oh, that's a very nice use of ChatGPT. This sort of question
| is usually impossibly hard to find by searching, and requires
| consulting the sages.
| mathewsanders wrote:
| I was so excited to try this because I have a book that
| I've not been able to locate (have tried my own searches,
| Reddit and online forums) but ChatGPT gave me a lot of
| hallucinations and listed out real books and incorrectly
| claimed that all those books had the plot bit that I'd
| remembered.
| twic wrote:
| Ah! Well. Nevertheless.
| taneq wrote:
| That one was fun. I loved the fusion ramjet exit strategy,
| and the big reveal at the end.
|
| There was also the one (was it Clarke or Asimov?) where they
| simply grew genetically engineered Jovian bodies and
| transferred their minds to them. That one (as you'd expect)
| ends with the explorers deciding it was way too much fun
| running around Jupiter as raptor-thingies.
| ayames wrote:
| This was "City" by Clifford Simak. Great book. The Jovians
| were called "lopers".
| defrost wrote:
| Damn good chance that was the one, it fits my reading
| timeline and I had a lot of Clarke (and my other "Golden Age"
| authors) - and the staggered shell for pressure reduction
| could very well by a minor throway plot point - Clarke put a
| lot of thought into space exploration and his stories were
| riddled with plausible notions that deserved further study
| (even if ultimately impractical).
| at_a_remove wrote:
| I also saw one, different, wherein the solution was that the
| shell curled in on itself and compressed, like squeezing a
| scroll.
|
| This was pre-Outer Limits, too, if I am right. The main premise
| was that a monomaniacal skillionaire decided to hoax the planet
| into uniting against a horrible threat inside Jupiter. The last
| transmissions from this doomed ship, as it descended through
| the ever-thicker atmosphere, was a kind of Lovecraftian
| exhortation that they were too horrible for him to properly
| describe, ending in "Defend! _Defend!_ " before cutting out.
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