The faster planes of the future

30 July 2019

Interview with 

Michael Carley, University of Bath

CONCORDE-PLANE

Air France's Concorde plane

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It's no secret that Izzie Clarke isn't the biggest fan of flying. So for her, the faster the plane, the better. She can reach her destination quickly and - hopefully - won’t have to spend as much time on the plane. Could we see faster planes in the future? Could supersonic flight, travelling faster than soun, be a commercial option? Michael Carley is a senior lecturer from the department of Mechanical Engineering at The University of Bath and joined Izzie in the studio to explain supersonic flight.

Michael - Supersonic flight is flight faster than the speed of sound, so faster than 770 miles an hour, if you're at or near sea level. Typical altitudes for commercial aircraft, you’d be doing more than about 670 miles an hour.

Izzie - Wow! What could it do for us? What is its potential?

Michael - Really, the point is that it's very fast, so for people who feel a need to not spend much time in the air and want to get to wherever they’re going in a hurry and who can afford to spend the money to make that worthwhile, that is the advantage. The issue for a lot of us would be that the amount of money you would need to spend to travel that fast just isn't worth it.

Izzie - Right, I see. And we saw something like this in the past, which was Concorde, so what was that and what went wrong there?

Michael - Concorde was a joint Anglo-French high-speed aircraft, so it flew at about twice the speed of sound. Technologically it was a massive success. It advanced the technology in all sorts of ways. It did successfully fly across the Atlantic at twice the speed of sound. The thing that used to impress people was that fighter pilots would occasionally meet a Concorde, the fighter pilot would be sitting in a cockpit at the same sort of height but having to wear a special pressure suit. People on Concorde were having a nice meal, sitting in their shirtsleeves in an air-conditioned cabin.

So it had comfort, it had speed, it had everything except it wasn't economical. It cost about $12,000 in modern terms to fly from New York to Heathrow and back again, which is about three times the price of modern first-class flight. It was very very noisy which made it completely unacceptable to people living on the ground and in the end it just wasn't possible to sell enough of them to make it economical to run.

Izzie - Now, economics aside, how are planes like this able to fly so fast?

Michael - Partly utterly monstrous engines and that is one of the things you need. You need to generate a lot of thrust to overcome the drag that's involved in flying at these speeds. You need a specially shaped wing, so Concorde is one of the very few utterly recognisable aircraft. People who have no interest in aeroplanes can recognise Concorde. So it's delta wing, it's got a very sweptback leading-edge; that is essentially what allows it to fly at those speeds.

There are a couple of other issues, the control is difficult. Matthew, I'm sure, will be able to tell you how hard it was to land an aeroplane. The problem with something like Concorde was that you had to keep the nose so high you can't see over it when you're landing or taking off, because of the difficulties of landing and taking off at low speed, which you have to do with those monstrous engines. So there are particular difficulties that go with high-speed aircraft that aren't, therefore, pretty conventional, economical, normal airliners that are in service today.

Izzie - And where are we now though with these superfast planes?  Could we see something like this make a return?

Michael - We could. There are a few options depending on who you are. One of the things to notice is that even the military don't have supersonic transport aircraft. Supersonic aircraft in military use are purely for combat. There have been proposals in the past to convert essentially fighters into small supersonic transports for business purposes. There is one company which has just placed a firm order for 20 supersonic business jets, so they'll carry about 10 passengers.

So realistically, we might see business jets or supersonic aircraft for business use in the near future, next 5 to 10 years, it's unlikely that we'll see commercial aircraft being operated by the airlines.

Izzie - And what are some of the issues that they would have to overcome regardless of whether this is business or commercial?

Michael - The big one is going to be fuel cost, they burn a lot of fuel. One of the things that we need to deal with is flying less. Supersonic aircraft, there won't be very many of them, but they are disproportionately high consumers of fuel so that will become an issue depending on how regulation goes in future.

Nobody has solved the noise problem yet, although NASA seemed to be getting close to it. In the next year or two they should have a demonstrator flying which will reduce noise to acceptable levels. What they say is it will be like a car door being closed rather than a massive bang if one of these aircraft goes over.

So there are the two big ones, solving the issues that allow you to operate the aircraft. Most of the other problems have been solved in a technological sense on Concorde, but we still haven't solved the problem of what it costs to run them and how we get the noise down.

Izzie - So do you think we will ever see something like a commercial supersonic plane in the future?

Michael - It's not likely. We’ve worked out how to fly reasonably economically with fairly conventional aircraft. If we are going to spend that kind of money again, I suspect some people are going to go for bust and just use suborbital flight. So in effect you use a small spacecraft, and then instead of thinking about three or four hours between London and New York, you're talking about one hour from London to Sydney, and in effect you bring space technology down to Earth rather than trying to bring military fighter technology to the flying public.

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