So far mankind has been able to pass the speed of sound at 343 m/s, yet we continue to strive to reach the speed of light as first discovered by Albert Einstein. In space travel, the idea of hypersonic space travel has lurked around for several decades. The term has been around since the 70s and refers to speed above Mach 5, which is five times the speed of sound.
So far, there have been a number of various commercial and private ventures hoping to reach hypersonic. For instance, the Hypersonic SpaceLiner will be able to travel from Europe to Australia in 90 minutes and it will soon be ready by 2030, according to its makers in Germany. Lockheed Martin is now developing Mach 20 – more than 15,000 miles per hour – and Mach 30 technologies. That could take a flight from the UK to Australia down to less than an hour.
Attempts to reach Mach 20 consistently have been thwarted by a lack of robust materials that can withstand the temperatures generated at these speeds, which is why the next generation of hypersonic materials are as unusual as they are deeply complex. “We have a material that cools itself by shedding electrons like the human body cools itself by sweating,” says Fouse.
Not only does hypersonic travel lack several advanced materials and technology. Yet hypersonic travel is also much harder to reach compared to reaching the speed of light, as temperatures get so hot that the air molecules become unstable and start losing electrons. The air begins to change chemically and becomes an electrically-charged field. However, such speeds have been reachable as the V-2 rocket, first used in World War II by Nazi Germany, reached a maximum velocity of 5,150 miles per hour - more than five times the speed of sound.
Hypersonic flight has applications beyond consumer travel. In defence, it could give governments the upper hand over enemies and, in the event of a humanitarian crisis, it could eventually allow aid to reach victims much faster although the cost of travel will be very high in the early years.
For its part, the Pentagon has pursued several parallel development paths for hypersonic weaponry. The Defense Department spent $108 million on hypersonics research and development in 2016 and $378 million in 2016. The department’s 2018 budget request includes $292 million for hypersonics research. The Defense Advanced Research Projects Agency, the Air Force and Army have all tested “boost-glide” vehicles that launch atop rocket boosters then glide, unpowered, at hypersonic speeds. However, most of the test flights have ended in failure.
So far, most hypersonic test flights have been unmanned and experimental, and have lasted for no more than a couple of minutes. However, The X-15, operated by the United States Air Force and the National Aeronautics and Space Administration secured the official world record for the highest speed ever reached by a manned, powered aircraft in June, 2015. Its maximum speed was 4,520 miles per hour or Mach 6.72.