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.
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.
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.
Google Loon or whatever they called the stratospheric balloons carrying solar powered cell/wifi base stations that made their way around the earth with the Jetstream or w/e used a bladder in the balloon that was inflated/deflated with ambient air.
Similar to a ship taking/releasing ballast water in ballast tanks.
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).
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:
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".
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.
Water is lighter than air and only needs a modest temperature to have it's vapor pressure exceed ambient pressure at high altitude.
Bonus for self-inflating when you reach altitude/letting you accumulate thermal energy in some form and take off by dumping the heat into your liquid water bladder to inflate your water vapor balloon.
Wonder how well/cheaply (in weight for $affordable budget) you could insulate the balloon to curb your thermal power demand. Maybe enough that you could use your liquid water bladder with a little insulation as a thermal mass to run an absorption heat pump (Type2: warm power, cold sink, hot target output) off of ambient temperature during the day, cooling the thermal mass back down during the night.
Or lightweight solar panels, I suppose, feeding an air-source heat pump to boil the water. Normal Li-ion batteries sadly don't really have enough energy density (water takes 620 Wh/kg to boil; commercial energy-dense Li-ion is in the 200~300 Wh/kg range; at sea level and boiling point (=lowest possible temperature without it wanting to condense on every dust particle and other condensation nucleus) water vapor is half as dense as 20°C air so it could lift itself twice (and once it's used to lift itself already), and even a very good heat pump will have severe difficulty reaching a COP of 4.0).
So I guess if you try really hard you could make a self-inflating steam balloon that takes off using Li-ion fed heat pumps and later stays airborne using solar cells to continue feeding the heat pumps...
Yeah, sorry, drifted off towards the end somewhat.
But no, water is lighter than air.
In it's gaseous form.
Which requires substantial temperature or low pressure. The former you can make easily, the latter you encounter if you fly high enough.
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.
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.
(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.
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.
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).
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.
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.
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.
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.
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.
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.
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 )
> 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.
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.
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.
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.
You are correct, it is still an option. But at some point I will introduce some combat as well and I don't want the ship to have such an obvious weakpoint.
It could be that I delay the combat at which point the player will have the option to have a honeycombed lifting body(/ies?) that can be armored or shielded in some way.
You're probably overthinking the realism. you do have prior art in all aspects though
Zero Point - Skies of Arcadia
Propeller - Final fantasy
balloon with combat - Red alert 2 Kirov Airship
will kinda depend on if this is 3d or not. if you're first person just shooting at the balloon portion, then yeah. go zero-point since profile will matter greatly. If this is an isometric or top down kinda game then like red alert you're just shooting a target not a piece of a target and you can just ignore damage to lifting apparatus (propellers or balloons) without breaking immersion.
Thanks for the feedback! You're right, it's not meant to be super realistic.
Although it is 3d its more of a base and unit management game, so its not an issue if other entities just ignore the envelopes.
It would probably be fine. The pressure under water is much much greater than in space. A submarine would be fine in space, but a spaceship would collapse quickly in the ocean.
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.
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
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.
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...
