Hypersonic flight through Earth’s atmosphere describes travel at speeds greater than five times the speed of sound (Mach 5) and has been achievable for some time. However, more recently, hypersonic flight has been seen in two new types of weapon systems - ‘hypersonic glide vehicles’ and ‘hypersonic cruise missiles’. These are currently making news in military circles, being uncrewed, capable of carrying a nuclear warhead and travelling so fast they are practically impossible to intercept. In general, these vehicles rely on a separate, ‘first stage’ propulsion system (like a rocket) to launch them and achieve such high speeds.
Now, such high velocities may just have been made possible for jet engines on aircraft. Researchers from the University of Florida have discovered a means to stabilise the detonation needed for hypersonic propulsion by creating a special hypersonic reaction chamber for jet engines. They claim the system could allow for air travel at speeds of Mach 6 to 17, which is more than 4,600 to 13,000 miles per hour. Apparently, the technology improves jet propulsion engine efficiency, so that more power is generated while using less fuel than traditional propulsion engines - thus lightening the fuel load and reducing costs and emissions. Ironically, this new technology could also be used in rockets to make space travel more efficient.
Travelling above Mach 5, however, is a difficult challenge. Hypersonic speeds can raise the temperature of a vehicle well above 2000°C, undermining its structural integrity. One mitigation is achieved through giving the vehicle a blunt nose, which generates a detached bow shock wave in front of it. This can act to dissipate heat away from the vehicle’s body. Ultimately, new materials will be needed, such as so-called ultra-high-temperature ceramic matrix composites (UHTCMCs). These may help combat some of the problems associated with such high speeds.
Estimated time to maturity: 5 to 10 years