Frightened of hydrogen balloons because of the Hindenberg disaster? Find the scarcity and price of helium dispiriting? But you still want to use a big balloon for travel and freight? Check out this theoretical possibility:
IN 1670, Francesco Lana, a Jesuit mathematician from Brescia, published a small volume describing his various inventions, including a chapter entitled “A demonstration of the feasibility of constructing a ship with rudder and sails, which will sail through the air”. A sketch showed what it would look like: a typical wooden sailing boat, except that the vessel would be suspended below four copper spheres, each containing a vacuum that, being lighter than air, would provide lift.
The idea didn’t fly. No one could make spheres with walls as thin as Lana calculated he would need – and in any case, they would have collapsed from external air pressure as soon as they were evacuated. But maybe Lana was on to something. There is now renewed interest in his vision of airships sailing through the clouds, borne aloft by nothing – and this time we might have the engineering solutions to get them off the ground. [“Could vacuum airships go from steampunk fantasy to 21st century skies?” Philip Ball, NewScientist (21 December 2019, paywall)
That would require a strong structure.
There is a problem, though. Without anything inside an airship’s shell, the air pressure is enormous. Use today’s materials to make a shell strong enough to resist the compression and it will end up so heavy that the vacuum inside will be unable to lift it. [Julian Hunt at the International Institute for Applied Systems Analysis] speculates that light yet superstrong carbon-based materials like graphene and carbon nanotubes could overcome this difficulty.
Ben Jenett, working on his doctorate at the Massachusetts Institute of Technology’s Center for Bits and Atoms, has another solution, and he has already made progress towards it.
Jenett has devised lightweight “lattice materials” in which tiny, rod-like struts are assembled into frameworks with tremendous stiffness and strength. It is the same principle as that behind the familiar triangular truss structures in cranes and the Eiffel Tower. Jenett’s struts are linked to form octahedral units with eight triangular faces that can be assembled into extended lattices. They are extremely light without sacrificing strength. A 10-centimetre cube of this lattice material weighs just under 6 grams, about as much as a small strawberry.
Fun! Perhaps we’ll start seeing the big balloons floating through the sky again. They should be far less polluting than modern aircraft.
