From Tim Langley
Brian Richards rightly points out the merits of modern dirigibles for transporting bulky objects (26 June, p 30).
Unfortunately, helium is widely seen as the only satisfactory buoyancy resource. Helium is truly wonderful, but it is very scarce. World annual production of the gas is only sufficient to allow the building of 1000 Hindenburg-sized airships per year (see New Scientist, 21 December 2002, p 48).
Hydrogen has better lifting capabilities, but is regarded as too dangerous for use as a buoyancy agent. One way of improving its safety might be by using what I call the “double bubble”, where an outer envelope of ammonia surrounds a hydrogen envelope within.
Ammonia has fair buoyancy capabilities and, though unpleasant, does not explode. It is produced, used, transported and stored with comparative safety in quantities exceeding 100 million tonnes per year. Any leakage from the hydrogen envelope would find its way into an atmosphere of ammonia – in which it cannot explode and which could be constantly monitored.
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This is not a perfect solution – and there may well be better ones – but if a fraction of the development effort expended on non-buoyant aircraft were directed to this problem, we might yet begin to see the environmental, economic and aesthetic benefits of airships.
Hereford, UK
