Robust metamaterial balloons
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
This capability is already demonstrated by a few special aerogels today but 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 (See:"[Self limitation for safety]" and "[Sharp edges and splinters]"). Pulling in all directions simultaneously (which natural occurring forces can't do) should rip the metamaterial apart easily. A malicious attack with utility fog may be possible (further analysis needed).
Steerability in high winds
- active surface motion can replace air resistance friction with much much lower infinitesimal bearing friction in the top layer surface pf the balloon. This tackles the tangential motion component of air.
- temporary adiabatic presence cloaking can tackle the air motion component normal (90°) to the surface.
For the balloon to not move as a whole the forces do not need to be compensated at every location independently. Allowing some stretching and bending the balloon can extract energy allowing it - given enough turbulences which are common near ground-level - to stay stationary permanently. The storm can last arbitrarily long. (This does not work in highly laminar stratospheric flows).
Base material quartz
Since earth's atmosphere contains oxygen any material that burns easily is problematic. While diamond does not burn in its bulk form the a highly filigree metamaterial structure would burn very vigorously. The solution is to use a material that is already in its oxidized state. Best options are 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. necessary internal nanomachine bearings may be made out of silicon carbide (moissanite) it burns but builds up a glass layer that prevents further burning.
- low mass air transport
- Various forms of "airmeshes" e.g. for transportation wind power and weather control (speculative)
- massive redirection of sunlight (speculative)
Since the density is lower than 1kg/m^3 (three orders of magnitude lower than dense material - factor 1000) huge volumes can be filled cheaply. Since for fire safety reasons atmospheric carbon dioxide can only be used in small quantities lithospheric mining is required making it a bit more expensive than dense carbon rich diamondoid products. There is no possibility for self accelerating growth through growing surface area like in the case of malicious air using replicators. But advanced mining can scale up self acceleratingly. It just needs energy in lithophilic elements out.
It seems possible that it'll become cheaper than todays cheapest building materials concrete and asphalt. Allowing to build airmeshes on a larger scale than todays ground-bound street network - a network of skyroads so to say.
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 potential well of Uranus and Neptune. Its unclear how safe hydrogen microcompartmentalized in glass metamaterial could be - maybe comparable to methane hydride - (TODO: closer investigatin required).
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)
- 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.