To evacuate the centre of a vacuum balloon, the skin must be effectively rigid. One way to build such a skin would be with a geodesic-sphere framework.
INDICATIONS
The dome-support frameworks invented by Buckminster Fuller give a light but strong framework to a geodesic dome without any internal braces.
The geodesic vacuum balloon would use the same concept, extended over a full sphere.
The outer skin of the balloon would need to be largely impermeable to air.
The skin could be made in layers, for example a coarse geodesic framework 1 metre thick (to give great rigidity), a fine geodesic framework 1 centimetre thick (to support the impermeable membrane), and the membrane itself.
Any sufficiently-rigid skin construction method would be practicable for a large enough vacuum balloon. For example, if the skin was made of armoured steel 5 millimetres thick, a vacuum balloon of similar dimensions to the 'Graf Zeppelin' would float if evacuated.
Light but rigid internal braces could be used for additional safety.
Development of devices and control software is possible here, with new approaches open to patenting or trade-secreting.
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