Propulsion: Prepare for takeoff!

17 July 2018

Interview with

Justin Burrows, Rolls Royce

Plane on Runway

Plane on Runway

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This year marks the 100th anniversary of the Royal Air Force. And, just last month, the newest fighter jet, the F-35 Lighting II, arrived in the UK. To celebrate these milestones, Chris Smith and Izzie Clarke embarked on the maiden flight on our own airline FlyNaked! Marika Ottman spoke with Justin Burrows from Rolls Royce in Derby about how we power a fighter - or indeed any - plane! But first, a special announcement from the crew...

Ladies and gentlemen, flight F-35 is now ready for boarding. Please make your way to gate 1 with passports at the ready.

Welcome onboard The Naked Scientists Airlines.Our in-flight entertainment will consist of a journey through time to learn about the evolution of the fighter plane. Today we will be flying on a Concorde. Although the Concorde is not a fighter plane, many of its features were inspired by military aircraft, including it’s supersonic shape and its powerful turbojet engine.In contrast, the role of a fighter plane is to take down enemy aircraft, usually in battles called dogfights. Fighters are designed to fly incredibly fast while also being highly maneuverable. Comfort is not a priority.

If you’ll indulge me ladies and gentlemen, the origin of fighter aircraft is quite interesting. In 1914, the first world war broke out. Airplanes at the time were made of wood and fabric. These wooden and fabric planes were completely unarmed. Their only purpose was to fly over enemy lines to track the troops and take photographs. It is said that enemy pilots would simply wave at each other as they flew past. However, as the war became more brutal, pilots became less civil and started carrying pistols on board. Some even threw bricks at each other! By 1915, machine guns were mounted to aircraft. And thus, the fighter was born.

Over the next 100 years, some remarkable advancements were made on fighters. We have gone from fabric and wooden wings to the F-35 lighting, but how did we get there? Stay tuned, and you’ll find out. Passengers, please fasten your seatbelts as we prepare for takeoff. Wishing you a pleasant flight here on the naked scientists.

Izzie - Sounds like a rather large engine, which makes me think: what does it take to power a fighter, or indeed any plane? To find out, Marika Ottman went to Rolls Royce in Derby. They built about a third of the world's jet engines and historically they've made engines like the iconic Merlin that powered the Spitfire. And they've still got examples of all of them. Justin Burrows is a material scientist with the company.

Justin - So were in the Rolls-Royce Heritage Centre. What this is is a chronological exhibition of technologies that the company's been involved with. We've got some piston engines here. so the Merlin. Then we move on to some of our early jet engines. And then we've got our latest large civil gas turbine engine, the Trent 1000.

Marika - The forward motion of an aircraft is caused by a force called thrust, which is produced by a propulsion system. In the early fighter planes of World War 1 and World War 2, thrust was produced by propellers.
Justin - Think of the blades on a propeller like two sides of a screw. So if you think about a screw that you screw into a wall at home, if you turn the screw it will pull itself into the wall. Well, a propeller kind of works in a similar way. So each of those blades as you spin them round, they then take the air and push it backwards.

Marika - propellers provide a simple and effective way to create thrust. So why don't we see propellers on modern fighters?

Justin - When we go into World War II, Spitfires were finding that if they went into a steep nosedive they’d get to, or approaching, the speed of sound. But what happens when you get there is that the air at that point is very very hard to move. The prop simply can't mechanically take the load on it so it's creating too much drag. It's also very difficult to have enough power to push the propeller through the air because it becomes very heavy. So it's kind of like trying to spin it through concrete at that point. So the solution to that was to go to jet engines.

Marika - In 1930 Frank Whittle submitted a patent for the turbojet engine. The development of the jet engine changed aviation entirely. Fighter jets were able to fly faster and higher, speeding past the enemy or around them in dogfights. Justin showed me one of the largest jet engines made to date, and took me through how it works.

Justin - We're looking at a Trent 1000 which is one of our largest civil aircraft engines, and we're standing in front of the fan section. Each one of the blades in here, just to give you an idea, is about six feet long and there's 80 of them in a conventional set in a jet engine. As these blades spin, they take air from the front of the engine and throw it towards the back. That is what gives us thrust on the aircraft. About 65 percent cent the air from that propeller bypasses the engine so it goes down the side of it. It just uses it to push the aircraft forward. about 30 to 35 percent goes through the center of the engine and that helps power the turbine section at the back of the engine. So the air that goes down the middle of the engine goes into the compressor section. So all that does is compress the air. It compresses it so well that it raises the temperature to about 700 degrees C, which is pretty hot to start with. With that point we then mix it with fuel which in this case is kerosene. We light a match, the temperature of the gas then increases dramatically and the pressure increases. So the turbine is very clever because it does two things, so it extracts energy from that gas which then drives the fan. The other thing it does is that gas going out the back also adds to the thrust.

Marika - Aircraft propulsion has advanced exponentially in the past 100 years. So what do we have to look forward to? Justin brought me to the technology centre to give me an exclusive peek into Rolls-Royce’s latest technologies.

Justin - So we are in the Technology Exhibition Building. This is purpose built for our end user customers. They'll come in here, see some of our new technologies, what we're going to be doing in the future. They also have the opportunity to look at the current build line as well, so they could see engines being made.

Marika - The current build line includes engines that are actually able to predict when they need maintenance.

Justin - As our aircraft are flying around they’re live, and they're sending data to what we call our operations center. We have a team of engineers looking at that data and if we've got an aircraft that is displaying a problem or an issue, we can arrange for a repair team to make the aircraft as soon as it lands with the parts are already there and they can fix the issue. And then there's no disruption to the customer. The other thing we can do is give the data to our manufacturing people and our design teams,they can then use that data from service of what happens to components to redesign components so they're more effective when they're in service. So there's kind of a whole feedback loop going on with all the data that we're getting from the aircraft.

Marika - So what is the future of jet engines?

Justin - One of the things we're involved with is an engine called UltraFan, which has two big improvements over the current civil gas turbines. One of them is it has a composite fan which is lightweight. The other thing is the fan is slightly larger. We've got a gearbox in that engine and that allows the fan to turn at a slower speed than the turbine. That enables us to deliver a product which gives fewer emissions and it's more effective than our current engine. We're looking at the potential for electric hybrid vehicles. What we then need to look at is materials for electric motors, energy storage how we can generate electricity to drive those motors, and how we can store enough power enough fuel if you like to keep the electric motor driving a propeller.

Marika - So just to be clear, you're talking about an electric airplane?

Justin - Yes we are. It won't be tomorrow but it might be a few days after that.

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