From Nicholas Thomas
Is the pursuit of hypersonic flight the aviation industry’s equivalent of controlled nuclear fusion (25 July, p 30)? Even if sustained hypersonic flight powered by anything other than immensely wasteful rockets proves possible, it is unlikely ever to be practical.
The Lockheed SR-71 “Blackbird” is the only Mach 3 plane ever built, for good reason: it gets hot enough not only to affect the design of every component, but also to prevent anyone working on it when it lands.
Hypersonic vehicles will get a lot hotter. It would be possible to design an air bridge that allowed passengers off without them having to wait for the vehicle to cool, though emergency escape might be a bit more of an issue. Jet aircraft are practical because they are airborne for many hours a day, not sitting on the ground cooling, congesting airports and racking up interest payments.
Revelstoke, British Columbia, Canada
