A hypersonic arms race between America, Russia and China, as all three countries prepare for a new era of faster, smarter and more nimble missiles. What are hypersonic weapons and will they change the character of war?
Hypersonic weapons are those that can travel more than five times the speed of sound, or around one mile (1.6km) per second. They come in two flavours. Hypersonic cruise missiles are powered by rockets or jets throughout their flight. They are simply faster versions of existing cruise missiles, like the Tomahawk. Hypersonic boost-glide weapons are different. They are launched into the upper atmosphere in the normal fashion atop existing ballistic missiles, but then release hypersonic glide vehicles (HGVs) which fly lower, faster and—to an adversary—much more unpredictably than old-fashioned re-entry vehicles. Though some, like the Avangard, are intended to carry nuclear warheads, others can use their high speed and accuracy to destroy targets with the kinetic energy of impact alone. At ten times the speed of sound, a kilogram of anything has more kinetic energy than you get from exploding a kilogram of TNT. Current ballistic weapons are very fast, but not as manoeuvrable; current cruise missiles are very manoeuvrable, but not as fast. Hypersonic cruise missiles and HGVs are novel because they fuse these qualities of speed and agility.