Graphene foam can be made up of tiny spheres of graphene that contain a vacuum. The graphene spheres are large enough that the average density of the graphene and vacuum is less than helium, so I suggested it as a helium substitute. Here is my original article:
It wasn’t long after I wrote it that a Chinese group achieved it, and they subsequently discovered it makes an ideal platform for cultivating stem cells, something that hadn’t even crossed my mind. But that’s engineers for you. Someone invents one idea and someone else runs with it and makes something far better. Anyway, graphene foams already exist today that are 6 times lighter than air.
We hear a lot about high altitude balloons being used for communications, e.g. Google’s Loon project. As is the norm for Google, the idea predates their’s considerably, but never mind, at least they are developing it where others left it on the drawing board.
High altitude balloons so far use helium to achieve the low density. In stark contrast, a huge solid balloon could be made out of graphene foam, and it could be lighter than helium yet stronger than steel. Graphene foam is therefore ideal for making solid balloons for a wide range of purposes.
Way above clouds, the top surface of such a balloon would be perfect to produce solar power for use inside, and the lower side is perfect to transmit this to the ground house communications transponders or simply reflect communication signals.
It could be ideal to house a death ray too, but let’s not think about that for now.
A large, solid, strong balloon could act as an excellent base for a wide range of activities, but it could also be mobile, just like an airship. A combination of special carbon motors such as graphene electron pipes directly powered by energy stored in graphene capacitors. These would be charged with solar electricity generated by from the intense sunlight unimpeded by clouds, the movement of a carbon wire through the magnetic field, thermocouples, solar panels, or harnessing power from high altitude winds. They could even use power harvested from hurricanes and tornadoes, saving many lives and a lot of property too:
Balloons could also used to deal with forest fires, collecting and storing water directly from clouds and dropping it onto the fire. In fact, these highly positive emergency uses may ultimately be the main reason such a large object would be allowed to remain up in the sky unchallenged in spite of its potential misuses (such as acting the role of mother-ship to a fleet of smaller airships or other weapons). With no need for helium, this kind of solid balloon would be much more environmentally friendly than the traditional variety, perfect for sustainability.