A small step has been taken towards the dream of hypersonic travel, and cheap satellite launches, that supersonic air-breathing engines could make possible.
In the Australian desert a rocket has been fired into space, reaching 7.5 times the speed of sound (9,200 km/h or 5,750 mph) and 278 kilometers (173 miles) in height. In the days of space travel this is commonplace, but on the way down the payload provided valuable data about the stresses hypersonic planes will need to combat in order to operate.
At the moment our fastest travel, be it into space or sending missiles across the globe, depends on rockets. But in theory there is a better way: Supersonic Combustion Ramjets – or "scramjets". Rockets are weighed down by the oxygen they must carry to combine with fuel. By drawing oxygen from the atmosphere scramjets, would carry much less weight, making room for other things.
Naturally scramjets won't work in space, and initial designs depend on a rocket to boost them to supersonic speeds. Nevertheless, Professor Michael Smart of the University of Queensland told IFLScience that by replacing the second stage of a rocket launch, scramjets could make satellite launches far more efficient and they could “fly back and land much more gracefully than Space X.”
An even more exciting aspect of the scramjet dream is for horizontal travel – in theory, scramjet-powered aircraft could fly from Sydney to London or New York in 2 hours. We're still a long way from that. This week's test is part of the Hypersonic International Flight Research Experimentation (HiFiRE) Program, a set of 10 planned launches scattered over several years. Smart told IFLScience the intention is that the last HiFiRE will involve “more than ten seconds of horizontal scramjet flight.”
Even at scramjets' astonishing speed, this will only cover approximately 30 kilometers (18 miles), and certainly won't be carrying passengers or satellites. However, Smart argues that once horizontal scramjet flight has been demonstrated it will be “up to a Boeing or a Branson to make it commercial.” He told IFLScience space tourism is likely to be a much earlier application than visiting the other side of the world before your legs have time to get cramped.
The other nine HiFiRE flights are about making the tenth one possible, collecting data either on how scramjets operate while plummeting to Earth at hypersonic speeds, or, as in 5b's case, studying the drag and heating an airplane-shaped object would experience at these extraordinary speeds. “We're building up the technology in small steps,” he told IFLScience.
The test is 5b because the second stage rocket of HiFiRE 5 failed, but Smart said the second try was entirely successful. “We haven't analyzed the data, but we've seen that we got everything we were looking for.”