JEGLEY: we found that if you have a crack and it grows to a certain point and gets to a point where it is stitched that crack will turn so instead of going through stitching it will turn and that is a good thing because in flight you would rather not have a crack grow all the way around a wing.
WHITFIELD: When you look at a piece of carbon epoxy composite material it honestly doesn't look very strong in it's raw form, but once it has gone through the entire process it can be much much stronger than metals.
JEGLEY: We start out with a fabric it looks kind of like carpeting, and you roll that out into the shape that you are looking for and you position all the different parts of your structure where you want them then you come through with a stitching machine. After you stitch the whole thing together the panel goes into an oven and it is infused with epoxy we heat it up and get everything just the way we want it and then cool the structure. What happens is you end up with a piece material could be a very large piece of material which is now stiff and strong and just in the right shape that you want it.
WHITFIELD: Another key component to carbon epoxy composite materials is that they can be tailored to be much stronger than metal. At the molecular level, the properties of metal are isotropic, which means that the properties all run in the same directions. Because of this feature aircraft designs are very bulky in some areas to provide stiffness, making a craft much heavier. But with composites you are starting with fiber which are very strong tough threads, so you can position those threads in any direction that you want. So if there is an area on the aircraft that takes a lot of loads, the designers can places the fibers in that direction providing enormous strength, but while also using much less material and weight than metal aircraft.
Of course validating that the pieces will work is a major element of the development stage. For that reason quite a bit of testing goes on here.
So I know that NASA is really does some great testing of its material before they go on any aircraft. How are you testing PRSEUS at the moment?
JEGLEY: One of NASA's goals is to develop technology for future aircraft. When we are developing new structure one of the things we need to do is fully understand how it is going to behave. And to do that we start by looking at very small pieces then we move up slowly to very large pieces till we get to a full scale part of an aircraft. The when we understand that we go to the next stage which might be something more like this where we have what we call a build up structure. So we have a skin and we have a stiffener on it. And then we can apply a load we might push on it, we might pull on it, we might bend it. To look at how that behaves. All the while were doing this we are doing analytical studies to make sure we understand and can predict how it is going to behave. Because if we don't predict it properly then we feel we don't really understand it well enough and we have to take a step back and figure e out what we it is we are missing. We have many facilities around the center here that we use for doing this type of test.
WHITFIELD: Well Dawn thanks so much talking to us today about PRSEUS. This looks like an amazing technology and you are doing a fantastic job. Thanks so much.
JEGLEY: Thank you.
WHITFIELD: Up next, let's look at another of the basic principles of flight -- thrust.
Since the earliest days of flight, engineers have looked for ways to make the engines we use on aircraft more powerful and efficient. One of the most important early engines was the 1903 Wright Brother design that was used for their first flight at Kitty Hawk. It only produced about 12 horsepower, but it opened the door for all aircraft engines to come. Since that time there has been a steady progression in the development of engine technology. From the relatively simple propellers of the past to the incredibly advanced jet propulsors of today, engines have never been better, but... Although current engines are already very efficient, quiet, and relatively green, they pale in comparison to what the next generation of engine technology will be. This is because NASA and its industry partners are breaking through long held barriers in design to make the next generation engines much much better.
To help understand how engine technology is improving, lets first take a look at how a basic turbo fan engine works. Incoming air is captured in the engine inlet. Some of the air passes through the fan and into the compressor and burner, where it is mixed with fuel for combustion. The hot exhaust passes through the core and fan turbines and then out the nozzle. The rest of the incoming air passes through the fan and bypasses, or goes around the engine. So a turbofan gets some of its thrust from the core and some of its thrust from the fan. The ratio of the air that goes around the engine to the air that goes through the core is called the bypass ratio.
Many engines today have a bypass ratio of roughly around 5 to 1. Engineers have known for many years that if they could increase the bypass ratio, then the engine would become much more efficient, but the trouble with increasing the bypass meant that the size of the engine would have to grow, making it heavier and also unable to fit under the wings of most planes. So what to do? Over the past 20 or so years NASA and industry have been working on a solution that would create ultra high bypass engines while also addressing the stated problems of size and weight. Today a new engine designed in collaboration with Pratt & Whitney and NASA has been developed that will more than double the bypass of current engines, which will in turn make the aircraft much more efficient and quieter.
This new engine design has taken many years of research and development just to get to the point where we are today because, three key pieces of technology needed to be developed that didn't exist. A new gearing system, an ultra efficient fan, and a more efficient nacelle. Although each of these were difficult to perfect, one of the most challenging was the gearing system for the turbo fan.
This is because there is a paradox in engine design. The slower the big fan at the front moves the more efficient it is, but the turbines at the back have to move at a very high rate of speed to work efficiently, hence the paradox. In order to have a slow moving fan at the front and a very fast moving low pressure turbine fans working together, a revolutionary gear system had to be developed that can do allow both of these part to work optimally.
DR. ALAN EPSTEIN, PRATT & WHITNEY: So what the gear lets me do is shrink the core engine that makes the power to a large degree. It makes it lighter, it takes a couple thousand parts out and it means I can replace some very rare super alloys with some more common gear seal. We always knew that we could do that, but you need a gear that is way over 99% efficient; you need a gear, we're talking about 25k 30k horsepower gears, naval ship has that kind of power with a gear that is the size of a small house. We had to develop a gear that is the size of a small automobile wheel not a house, and it had to last 20 years without maintenance and it has to be super efficient. We have been working on this for at least 20 years.
WHITFIELD: Much of the testing for this engine has in fact come at NASA laboratories. NASA's unique facilities and subject matter experts have helped the Pratt & Whitney team tremendously in understand how to configure the ultra high bypass engine.
CHRIS HUGHES, NASA GLENN RESEARCH CENTER: So this is an example of the ultra high bypass engine from Pratt & Whitney called the Geared Turbo Fan. This particular engine has a bypass ratio of about 15 to 1 which means that 15 times the amount of air goes through this part than goes through this part. This is the engine part this is the bypass part. In this particular engine all the thrust is generated in this part. And we have removed the fan so that you can see how small the engine air flow is compared to the overall flow. So why... Why do we want to do this? This particular design, especially the one Pratt & Whitney is working on the geared turbo fan has the potential of having as much as 20 percent fuel better fuel burn than a regular jet engine today, the reason they can do that is because the more air that you can put up here the more efficient the engine is and the better the fuel economy.
WHITFIELD: Because fuel costs have spiraled out of control in recent years the fuel efficiency of this engine could be a game changer for the aircraft industry. The people who care are not so much Airbus, but their customers, the airlines. So, an A320 with these new engines on compared to the current engines will make $200 to $400 dollars per hour on the order of a million-and-a-half to 2 million dollars a year on reduced fuel cost, depending on the cost of fuel, typically. So its worth millions per year for the airlines. Doesn't mean that they still won't charge for the extra bag though. Of course fuel economy is not the only huge benefit to this engine; its noise reduction capability is truly astounding. On a typical jet aircraft the fans at the front are moving at more that the speed of sound, making them very noisy, but because this new engine's fans in the front move slower, they now make much much less noise.
EPSTEIN: They are really quiet. How quiet is "really quiet?" For a 737-size airplane, a 150-passenger airplane, the objectionable noise on the ground the area that hears objectionable noise is reduced by about 3/4 -- almost to the NASA goal, which is to keep it in the airport.
WHITFIELD: Another key component in the testing chain of the entire engine happens here at NASA Glenn in The Advanced Subsonic Combustion Rig or ASCR. This facility is the only one in the country that allows real time, real world testing conditions for engine combustors.
DR. KEN SUDER, NASA GLENN RESEARCH CENTER: This is the advanced subsonic combustor rigs. It is really one of the unique facilities in the U.S. which enables us to test combustors in gas turbine engines at realistic conditions that they would see in a gas turbine engine flying in today's aircraft and even those flying in the next 20 years form now. The real beauty of this rig is that it allows us to operate pretty much over the whole flight regime, so we can map out what the emissions are near the ground during idle and take off conditions, but also at approach and landing. In addition even at cruise, cause were also becoming more and more concerned about emission in the atmosphere and what that does to our environment.
WHITFIELD: The environment is one of the key components in much of the work going on now. NASA and industry realize that good stewardship is not only beneficial to the planet but a can be a good business model, too. The work that is coming out of this program is looking at both fuel flexible applications as well as strictly environmental concerns.
DR. MICHAEL WINTER, PRATT & WHITNEY: Our geared turbo fan is 15 percent more efficient and can run on a wide range of fuels. In fact we are some of the leaders working with the industry in the development of biofuels.
WHITFIELD: Of course, testing for these new engines is not only happening at NASA, but also on a unique airplane owned by Pratt & Whitney.
Adams: Pratt & Whitney actualy owns two 747 airplanes that we do testing on. There are four engines on a 747; we will actually take one of the existing JT9D engines off -- which is a Pratt & Whitney-made engine that powers 747s -- and we will actually, in some cases, replace that engine with one of our test engines. So we will run the airplane on four engines. Three of which are currently certified on the airplane the fourth being the experimental.
WHITFIELD: Of course, this new geared turbo fan is not the only game in town. NASA has also taken a look back at some older technology including a concept called the open rotor that also shows much promise.
DR. DALE VAN ZANTE, NASA GLENN RESEARCH CENTER: So here at NASA we're working on the next generation engine technologies -- both ducted engines, like the geared turbo fan, and unducted engines, like the open rotors. So we recently finished a series a tests with General Electric and the FAA on open rotors, looking at these technologies to reduce fuel burn and improve acoustic performance of these next generation engines. So as you try to go to higher and higher bypass ratio engines the fans keep getting larger and larger diameter. And at some point it just makes sense to get rid of the cowling and go with just, what essentially looks like a propeller. The difference is these are very specialized high speed propellors so that an open rotor powered aircraft would be able to fly essentially the same speed as an aircraft with a jet engine.
WHITFIELD: In the past, the open rotor concept had been promising but the major drawback was the noise. Thanks to the advent of modern computation fluid dynamics, NASA and industry engineers have been able to redesign the blades for these open rotors and make them much much quieter.
VAN ZANTE: The system studies that NASA has done have shown that -- for a single isle aircraft, if we built an open rotor engine today and put it on an aircraft, it would probably be quieter than most of the aircraft that are flying out there now. So we have come a long long way in being able to solve the acoustic issues that were part of the original unducted rotor program.
WHITFIELD: So there you have it. NASA's ERA program and industry are truly changing the way we all fly. NASA is pushing the industry hard to make these changes see the light of day, and industry is responding with truly innovative and ground breaking technologies.
With this type of collaboration and work ethic, there is no doubt that the world will soon see a dramatic difference in the way we all fly.
I'm Vince Whitfield, and we will see you next time on NASA X.