At atmospheric pressure, a given volume of hydrogen weighs approximately 7% (there is some variation with temperature) of an equivalent volume of air. All that

At atmospheric pressure, a given volume of hydrogen weighs approximately 7% (there is some variation with temperature) of an equivalent volume of air. All that is needed to contain hydrogen at atmospheric pressure is a membrane it can't pass through. The inwards force exerted on the membrane by the atmosphere is perfectly balanced by the outwards force exerted by the hydrogen gas. The only structural material required is for the purpose of harnessing the lifting power of the enclosed gas, providing an aerodynamic shape, etc.. Conversely, a vessel containing a vacuum must be built to withstand the 101,325 N/m^2 net inward force exerted upon it by the atmosphere that is not balanced by the outward pressure of the contents of the vessel. Consider, for a moment, what you would need to build a 1 m^2 coffee table out of if 20 elephants were to be able to stand on top of it at once. For the sake of argument, let's say that we had a magical material that would let us build a replica of the Hindenburg that is of equal weight to the original, only with vacuum vessels replacing the hydrogen bags. The Hindenberg contained 200,000 m^3 of hydrogen lift gas, weighing 1,798 kg and displacing enough atmosphere to provide a total lift of 25,850 kg, 10,000 kg of which were considered it's cargo capacity beyond the passengers it carried. This new version of the Hindenberg, despite being built with materials and techniques that are probably well beyond our current level of technology, would carry the same number of passengers and just 18% more cargo. For those of you who think that vacuum vessels are a lot safer than hydrogen, I'd like to remind you that the atmosphere surrounding 200,000 m^3 of vacuum provides a rather huge amount of potential energy waiting to be released. When vacuum vessels of a large size fail the resulting implosion can be both spectacular and devastating. https://www.youtube.com/watch?v=Zz95_VvTxZM https://www.youtube.com/watch?v=Zz95_VvTxZM