Back in the 1960s, a senior Pentagon official would greet incoming recruits to his department with a cheery announcement: ‘Welcome to the world of strategic analysis, where we program weapons that don’t work to meet threats that don’t exist.’ The recent media excitement over Chinese tests of a hypersonic nuclear weapon which, anonymous Pentagon officials told credulous reporters, overcomes even the ‘constraints of physics’ shows that not much has changed.
Hypersonic missiles fly at five times or more the speed of sound. While ballistic missiles follow a fixed trajectory up into space and down again, so their course can be tracked soon after launch, hypersonics are designed to manoeuvre through the upper atmosphere, so that defenders cannot plot their course and thereby intercept them.