You are a businessman in London with a crucial dinner this evening in Tokyo. Even allowing for the nine-hour time difference, you won’t need to reset your morning alarm as you’ll be on the ground and knocking back the sake just two hours after take-off.
Or maybe you’re a busy working woman keen to get the Christmas shopping done. You can’t waste too much time on it – so how about New York? You’ll be there in less than an hour.
Boarding all rows for Flight Hypersonic!
Long restricted to the realms of sci-fi, the dream of flying at least five times the speed of sound – and getting anywhere in the world in less time than it takes to go from King’s Cross to Newcastle on the fast train – came a step nearer this month.
Engineers at Lockheed Martin in the U.S. revealed that they are developing the SR-72, a successor to the SR-71, the iconic Blackbird long-distance spy plane.
The Blackbird holds the air speed record of Mach 3 – three times the speed of sound – but the SR-72 will go twice that speed, at up to 4,567 mph.
At Mach 6, it would be three times as fast as Concorde.
Able to circumnavigate the globe in six hours at an altitude of about 80,000ft, Son of Blackbird, as it’s been dubbed, will be an extraordinary weapon of war: effectively, it will be too fast to shoot down and too fast for moving military targets to avoid it.
Indeed, it will be so fast it will have to be clad in a skin made from titanium crystals wrapped in carbon fibre to resist the extreme friction heat such speeds will create.
All very useful militarily, but the question many scientists and aviation experts have been asking is: can the same technology be used to transform civil aviation to send passengers around the world in lightning speed?
Enthusiasts have been talking up hypersonic travel for years and, apart from a few short-lived experiments, nothing much has happened. This is largely because the field is fiendishly expensive to develop and the technical difficulties enormous.
But what has excited aviation experts about Lockheed Martin’s announcement is that it claims to have overcome the biggest technical hurdle – the so-called ‘thrust gap’ in the plane’s propulsion.
Essentially, while a conventional jet turbine can get a plane up to Mach 2.5, the so-called ‘scramjet’ – a powerful jet engine that can work at extraordinarily high speeds by sucking in supersonic air – cannot start working until the plane is flying at more than Mach 3.5.
The problem is bridging the gap from the lower speed to the higher one. But Lockheed says it has designed an engine that can do just that, powering the aircraft from a standstill to Mach 6.
‘It’s a significant step forward. They seem to have simplified things,’ says Dr Phillip Atcliffe, senior lecturer in aeronautical engineering at Salford University.
A specialist in hypersonic flight, he believes such travel would be a ‘great development for mankind’, but adds: ‘It would shrink the world even more than we already have, but it’s not going to happen overnight.
‘There’s a lot of technology to be developed and we have to have governments and companies who are prepared to research and design it – and then airlines to buy it.’
But he believes that if the money were available – and we are talking serious money – a hypersonic passenger jet would not be unfeasible. It could even be developed by 2030.
Nobody denies the challenges of building a Mach 6 passenger jet would be far greater than for a spy plane the size of a fighter jet.
It would have to be a lot bigger and – most important – it would have to protect its passengers from the intense heat created by the plane’s extraordinary speed as it passes through the atmosphere.
Concorde flew no faster than Mach 2, primarily because the materials weren’t available in the Sixties that could withstand greater heat.
Technology has advanced since then, and the SR-72 will be a so-called ‘warm structure’ – it will heat up rather than reflect the heat with the sort of ceramic tiles that covered the Space Shuttle.
There’s also the noise to consider. Concorde wasn’t allowed to fly supersonic over land because of the ‘sonic boom’ – the sound associated with the shockwaves created by a craft moving faster than the speed of sound.
According to experts, if a passenger jet flew at Mach 6 at current jet altitudes of around 30,000ft, the sonic boom could damage buildings.
So how high might a hypersonic passenger jet have to fly, and how long might it take to get around the skies?
Believe it or not, Dr Atcliffe refers me to the very first episode of the children’s TV series Thunderbirds, in which the brave puppets of International Rescue have to deal with a bomb on board a hypersonic airliner, the Fireflash.
‘The episode was made in 1964, but they got it right in so many ways,’ he says. ‘It flew from London to Tokyo in two hours at Mach 6, which is surprisingly accurate if you allow for acceleration at the start and deceleration at the end.’
The Fireflash flew at about 250,000ft – still within the Earth’s atmosphere – and Dr Atcliffe reckons this, too, could be about the perfect altitude. It would be sufficiently high to cut down the heat generated because the atmosphere is colder and thinner.
As for the flying experience, cocooned inside their pressurised cabin, hypersonic passengers would probably experience little that was different from flying today.
Acceleration might be a little faster on take-off with the plane taking about 23 minutes to reach Mach 6.
Clearly, there wouldn’t be much time for films, and the crew would have to be quick with the drinks trolley and duty frees.
One major difference: for heat protection, there might not be any windows – even in the cockpit, where pilots would have to fly by computer.
And what about the question that would surely be uppermost in passengers’ minds: would it be safe to travel at almost 5,000mph?
Concorde suffered only one major accident, but it was catastrophic – the 2000 Air France disaster in which all 109 people on board died after the plane hit a piece of debris on the runway as it took off from Paris.
‘If anything goes wrong, it’s going to go wrong very quickly, and the potential for disaster is that much greater,’ warns Dr Atcliffe.
‘If something breaks the plane’s skin, at that sort of speed the airflow is so powerful it can start tearing chunks off the plane and it would disintegrate very quickly.’
And there’d be no room for a malfunctioning air con system or passengers would start to cook.
Aeronautical experts admit this is all uncharted territory – even the Space Shuttle reached such high temperatures only for a few minutes as it re-entered Earth’s atmosphere.
It’s also hard to say how much it might cost to fly hypersonic. Ticket prices will inevitably depend on how many passengers a plane can carry – so the more it can hold, the more commercially viable the flight.
Concorde had room for only 100 passengers, but it was limited by Sixties technology. Experts say there is no reason why a hypersonic jet couldn’t take up to 300 passengers.
Not that it will look as pretty as a conventional jetliner, and certainly not as sleek as Concorde.
It’s more likely, says Dr Atcliffe, that the wings would blend into the fuselage more closely and that it would have a stubby shape to cope with the huge air pressures.
But despite the excitement in the voices of aeronautical professionals, Jock Lowe, BA’s former chief Concorde pilot, has been saying for years that a hypersonic passenger jet just won’t fly as an idea, and he’s not changing his tune now.
‘I know how difficult it was to design and build Concorde and that was far more do-able,’ he tells me. ‘It’s simply not practical for anything bigger than a small spy plane,’ he insists.
Maintenance could also be an issue, says Jock. ‘Imagine the Space Shuttle being turned around in an hour and being sent off again . . . that’s the size of the problem.’
The industry doesn’t appear to share his views: aircraft giant Boeing is also researching hypersonic flight and calls it, in a nod to Star Trek, the ‘warp speed of today’.
The Victorians believed travelling at more than 30mph would make the human body collapse. What they would have made of technology that could propel people at 150 times that velocity is anyone’s guess.