Robust vacuum balloon metamaterial

Advanced atomically precise manufacturing allows to build a new class of aeronautic balloons that use vacuum instead of lifting gas. The necessary support structures that counter the external pressure can be made fine and filigree enough such that the whole structure is still lighter than air.

Note: Aeronautic balloons out of robust metamaterials are not to confuse with: Diamondoid balloon products

Proof of principle & Math

(TODO: Run the numbers!)
While pushing the limits this seems promising since
there is experimental evidence even with today's materials (from certain special aerogels).
Further up in the stratosphere and above this becomes increasingly questionable.

Mechanical stability

Unlike todays aerogels balloon metamaterial is an advanced atomically precise metamaterial and shows much more resilience against physical attack (crunching/ripping).

Chrunching: When it is crunched it reversible folds down to a state with almost no void gaps rasing its compressive strength to almost to the level of solid matterial. Obviously it will stop floating for the time it stays crunched. The material can (and probably should) get designed in such a way that when it gets crunched it stores at least enough energy such that the subsequent (undamaged) unfolding - which has to work against atmospheric pressure - can be easily performed.

Ripping: When a force acts on the balloon-metamaterial that pulls it apart the internal structure can reversibly align into the axis of the polling force again like in the compressive case to the point where it becomes almost as dense as solid material and reaches almost the tensile strength of solid material. In practice one probably wants to put in a safety limit way below the strength of carbon nanotubes for preventing injuries (See:"Self limitation for safety" and "Sharp edges and splinters"). Pulling in all directions simultaneously not just one (which natural occurring forces can't do) should rip the metamaterial apart easily.

A malicious attack aiming to drop balloons from the sky with using e.g. using utility fog with microcomponent recomposer microbots capabilities may be possible (further analysis needed).

Steerability in high winds

• active surface motion can replace air resistance friction with lower infinitesimal bearing friction in the top layer surface of the balloon. This tackles the tangential motion component of air. Overcompensation can act as propulsion.
• temporary adiabatic presence cloaking can eventually tackle the air motion component normal (90°) to the surface (very speculative).

Extracting energy from relative air motions in turbulences and employing it to stay stationary.
Allowing some stretching and bending on local patches on the balloon can extract energy from local turbolences.

If enough energy can be harvested then the balloon can be kept stationary permanently without an external energy supply. Exploitable turbulences are more common near ground-level. It seems this should not work from turbolences caused by the presence of the airship itself. Those need to be cloaked as described above. Also this does not work in highly laminar flows like common high up in a calm atmosphere (especially tropospheric weatherless stratosphere). What does work there is dynamic soaring.

Dynamic soaring is a way that allows for harvesting energy from wind-speed gradients at larger scales than the scale of the aerial vehicle (even without contact to stationary ground). This does not leave the vehicle entirely stationary but requires it to criss-cross at the scale of the wind-speed gradient. It's seems likely that larger quantities of energy can be harvested than from local turbolences.

Base material sapphire & quartz

Since Earth's atmosphere contains oxygen any material that burns easily is problematic. One reason to go for vacuum balloons rather than hydrogen as lifting gas. While diamond does not burn in its bulk form, a highly filigree metamaterial structure would burn very vigorously. A solution is to use a material that is already in its oxidized state. Good options seem to be Silicon dioxide (quartz) aluminum dioxide (sapphire) or titanium dioxide (Rutile/Anatas/Brookite). Biominerals like calcite and hydroxylapatite also do not burn since they are based on oxides of carbon and phosphorus respectively. See: Salts of oxoacids. Necessary internal nano-machine bearings may be made out of silicon carbide (moissanite) it burns but builds up a glass layer that prevents further burning.

Applications

• low mass air transport
• Various forms of "airmeshes" e.g. for transportation wind power and weather control (speculative)
• massive redirection of sunlight (speculative)

Price

Since the density of the vacuum balloon metamaterial is lower than 1kg/m³
(three orders of magnitude lower than dense material like water - factor 1000)
huge volumes can be filled cheaply.

It seems possible that the vacuum balloon metamaterial will become cheaper than today's cheapest building materials concrete and asphalt. Especially in terms of volume. Eventually allowing to build airmeshes on a larger scale than today's ground-bound street network. A network of skyroads so to say. See: Atmospheric meshes. Less but still speculative just airships.

Influence of base material on cost

Since for fire safety reasons carbon from the reduction of atmospheric carbon dioxide can only be used in small quantities as building material, lithospheric mining is required. This is making it a bit more expensive than dense carbon-rich diamondoid products.

Having a silicate or aluminate or other lithospheric element based design there is no possibility for local self accelerating growth like in the case of malicious air using replicators without a complete redesign of the entire system to HCNO usage. Advanced mining can scale up self acceleratingly reducing costs. See related page: Lithospheric mesh.

Why not hydrogen as lifting gas? – Relation to the conventional lifting gas method

Avoiding the use of the very scarce element helium may lower price from todays perspective albeit we may import that element from space in the future if we figure out how to get it out of the deep gravitational potential well of Uranus and Neptune. Or some yet undiscovered ultra deep space location (wildly speculating).

Its unclear how safe hydrogen microcompartmentalized in glass metamaterial could be - maybe comparable to methane hydride - (TODO: closer investigatin required).

As commonly known hydrogen as lifting gas has gained a bad reputation from the Hindenburg disaster.
One could arguably say though that flying around in planes surrounded by two giant tanks of kerosene is no less scary. The combustible high energy material is just well hidden away in airplanes wings. If planes become hydrogen powered (as some work is done on as of time of review 2023) it becomes even less of a difference. Well, the attack surfaces of airships for lightning strikes or crashes with other flying objects is bigger. And steerability is more limited. This being at the mercy of the wind situation may get significantly better with very advanced gem-gum-tech though as described above.

In the end a lot depends on the scale. If large scale interconnected aerial meshes really become a thing, then having them combustible internally (hydrogen as lifting gas) or externally (carbon as building base material) would be a recipe for a really bad apocalyptic large scale disaster with a burning skies coming crashing down. Thus better no carbon and no hydrogen, but silicon oxide or aluminum oxide and vacuum (or helium).

Energy content of the spanned up vacuum

Note that the vacuum alone carries a significant amount of energy.
Pressure in Pascal times volume in m³ gives Joules of energy.
10kPa*1m^3 = 100kJ/m³ = 277.8Wh/m³
About equivalent to lifting 1m³ of water up 10m of height
1000kg/m³*10m/s²*10m = 100kJ/m³

This is still minute that is ~100x less compared to chemical energy storage.
Uncompressed hydrogen gas at 1atm: 11880kJ/m³
Uncompressed methane gas at 1atm: 37800kJ/m³

On the one hand this may be a safety issue,
on the other hand a potential inverted air pressure energy storage
lacking losses from compression heating up air due to the infinite reservoir.
Though with advanced tech there are probably better ways. See: Chemomechanical converters.

Limits of low and high pressure

The hight limit of metamaterial vacuum balloons is probably a lot lower than the height limit for conventional balloons. (TODO: estimate the hight limit on earth)

At places with higher atmospheric densities (e.g. gas giant planets) the pressure becomes so high that crushing is not preventable. A hot air balloon or active lift via medium movers remains the only option. In Venus high pressure carbon dioxide atmosphere normal terrestrial earth air is a fine lifting gas. (TODO: estimate the pressure limit / water depth resilience on earth)

Wire-frame vs compartmentalization

Wire-frame structures are the lightest internal structures possible but do not compartmentalize the inner volume for accidental flooding protection. (TODO: Investigate in how far compartmentalization can be added (no full wire-frame displacement) without making the structure to heavy to fly and lift)

Related

• Different concept: Gem-gum balloon products
• Atmospheric mesh Warning! you are moving into more speculative areas.

External links

• Video showing some aerogel (SEAgel) floating in gas according to the narrative the surrounding gas is pure nitrogen which is a tiny bit heavier than air. The trustworthiness of the narrative is questionable. They should have said "air made thick by nitrogen" instead of "air made thin by nitrogen". It could also be a even heavier gas. Note that advanced atomically precise materials would be A) self sealing against ambient air and truly floating in normal air. They would be B) much stronger that is they would return to their original shape after fully crushing them or fully stretching them to a dense state. A state in which they are very strong.