Electric airplanes could be on the horizon as NASA tests X-57
February 12, 2020 11:22 am
10 min read
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Electric cars have become pretty common. The next round of electric just might be airplanes. In fact, NASA has built an electric plane called the X-57. It’s a test bed for new propulsion systems that don’t burn fuel. For more details, Federal Drive with Tom Temintalked with the project manager for flight demonstrations and capabilities at NASA’s Armstrong Flight Research Center, Brent Cobleigh.
Tom Temin: So the X-57, describe it for us. It looks like an airplane and the wings come off and you stick new engines on and put it back.
Brent Cobleigh: This was a technology demonstrator. So the intent here was not to try to design the most optimal electric airplane, but to really focus on the propulsion system, the electrical propulsion system. So in order to do that sort of an inexpensive way, we basically took a general aviation airplane that already exists, and modify that with this new propulsion system. That way we can compare what was the performance of this airplane with a traditional engine that uses fuel and then compare that to the electrical system back to back. So that’s the key way that we’re developing technology with this test-bed X-57. And so we’re going through several phases with X-57. We’re gonna initially put in our propulsion system with sort of a two propeller configuration. And then, over time we’re gonna expand in the future phase to add more propulsion, more rudders on the airplane more like some of the more advanced configurations that are coming up in urban air mobility.
Tom Temin: Besides the propulsion system itself, that is the kilowatt hours being generated by batteries, there’s a whole system of variables, such as the wing shape and the propeller configuration and shape and movement. That sounds like a pretty complicated deal to get the most efficient combination, isn’t it?
Brent Cobleigh: Yeah, the way aviation is making improvements today, is that all system designs are getting more and more integrated. It used to be, you know, the aerodynamic team could sit in one building in the propulsion team could sit in the next. an the structures in another, and work on the airplane and sort of bolt everything together and fly it. But to get even more and more performance out of the airplanes, modern airplanes, you really have to work together. So the propulsion system interacts heavily with the aerodynamics of the wing and the wing shape. As we know, aircraft aerodynamics works better with longer wings that, like you see with birds that birds that sail have much longer wings. And so the X-57 in our final phase is gonna have a much longer, shorter, thinner wing. We call it high aspect ratio wing, and that has better performance. But when you do that, the wing becomes structurally more challenging to design and more flexible. And then you have multiple propellers blowing air over that thin wing. And so you have real challenges in the engineering design and how to make that all work together.
Tom Temin: Yeah, From the video, I saw it. The wing is almost like a B-24 from decades ago.
Brent Cobleigh: Yeah, it is very long. In terms of gonna have much smaller wing area than the original aircraft wing that we started with, and that allows us to basically have lower drag when we’re in flight, which allows you to use less energy to fly. The challenge with that configuration is with smaller wing area. It makes it more challenging to take off and land. You need a certain amount of wing area to lift the airplane up. So the way we solve the problem of take off and land, is that we add these extra rudders, propellers, essentially, along the leading edge of the wing. So when we’re taking off and landing, these extra propellers roles it to essentially accelerate flow over the wing. And so the wing aerodynamics thinks it’s flying faster than it really is, which gives us more lift. And then, once we take off all of those rotors along the leading edge, turn turnoff and fold back and become sort of aerodynamically clean again. And then we cruise with the two crews motors, which are electric motors as well. So in the end, you end up with an integrated system that uses a lot less energy.
Tom Temin: It sounds like this research could benefit not just electricity powered flight, but all powered flight.
Brent Cobleigh: Yeah, that’s true. What you’re seeing in sort of all field of aviation right now, is this the same kind of design concept to go to higher aspect ratio wings, lighter structures and more advanced propulsion. So even in non electric airplanes, you’re seeing certain to see these types of features get in there to really make airplanes possible.
Tom Temin: Talk about the programmatic aspect of this. Do you have contractors involved? I mean, who supply the airframe that you modified? And what about the batteries in the motors and all that kind of stuff?
Brent Cobleigh: This was originally a very what we call a seedling effort. So it initially started as hey, let’s put a couple engineers together and let them work on this problem just to kind of see what develops. And very, very quickly, people started realizing the benefits that were available to us that we were trying to pursue. And also, we quickly realized, hey, if we’re gonna really build this vehicle and fly it in a meaningful way, that we’re gonna have to increase the size of the team to actually make this a reality. So we grew the airplane project from a seedling effort, and then we moved it into my project to actually execute it and turn it into a basically a small experimental plane, or X-plane as we call it. And so that project we actually started with some small companies. ES AERO in California is our prime contractor, and they work with several smaller companies like Joby Aviation, which has been developing electric motors over the last several years, and those are seedling efforts as well. And then the battery system is also a big challenge. Batteries are very heavy, and that’s our power system. That’s where we get our energy from. And so we’ve had to both have a big technology development effort to make them not only lightweight but make them safe at the same time. And that’s very, very challenging. So Electric Power Systems is the company that’s been developing a battery with NASA, and we’ve had a really nice synergistic relationship with all these companies. The battery development, for example, had several challenges along the way, and we actually reached out to some of our space friends and NASA, and they actually helped us with some of the design problems we had with that battery. And now that batteries actually having some commercial success outside the X-57 program. There’s many companies out there working with this small company, EPS to actually take this technology to other urban air mobility applications?
Tom Temin: Yes, urban air mobility. I mean, when you look at the Wright Brothers, they flew the first time about the length of the average McMansion in the suburbs. Does this demonstration project lead you to think understanding that it is very early that the time will come when electrically powered vehicles like this could fly a economic number of passengers a useful distance?
Brent Cobleigh: Yeah, well, so they’re several markets out there for electric airplanes, and the initial one that people are looking at is this sort of urban. You can think of it as urban air taxi’s, think of your traditional Uber type situation, but you’re using the third dimension the vertical dimension, to fly across the city very, very rapidly. And so in that market there is just since X-57 has started, the amount of investment money going into that in industry is just skyrocketed. And so us at NASA were believers in this technology. But the people who have lots of money are also becoming believers, and they are investing billions of dollars right now, and many, many companies to make that a reality. But the other markets are also very promising, and money has started flowing to those as well. So urban application is moving small numbers of passengers, but eventually to make a really big impact on the industry and sort of the commercial market, you want to move people, large numbers of people. So electrifying passenger airline aircraft is also a goal of NASA, and it will most likely start off with smaller airplanes and then move to commuter airlines and eventually to the large sort of cross country type, single aisle airplanes. And in those cases, it may not be initially be fully electric airplanes. They may be hybrid electric airplanes in the same way as cars developed hybrid first Those applications will probably come to be first, but there’s a lot of performance benefit you can get in that and obviously both in the energy side, but also in the environment side. If you’re burning less fuel, you’re making a less negative impact on carbon in the atmosphere, and so you really that’s really an important part of the of what electric does for us.
Tom Temin: Right now for airline type travel., those planes generate 20-30-40 kilowatts of energy times however many hours carrying so much weight, so much distance. Do you see that fundamental physical problem being altered? Or will the electrical systems have to generate the same number of kilowatts for the same distance, for the same time?
Brent Cobleigh: Yeah, so I think initially there are a lot of skeptics out there that looked at the energy density and fuel and said, you’re never gonna get there with battery technology, which is probably true, at least not within my kid’s life times even. But, if you sort of look at the airplane as an integrated system. There are ways to improve the performance of the airplane through hybrid approaches, there’s many different types, that allows sort of a traditional engine to be combined with electrical systems to reduce the overall energy, usage on an airplane and make it less costly to operate as well. So you can imagine a situation where you have electrical systems that help for takeoff and landing, for example. Then you can reduce down the turban airplane during a cruise situation and emit less carbon, run the engine at cooler temperatures which causes less maintenance, things like that. So there’s these hybrid approaches the big companies are looking at now, and they’re starting to invest huge amounts of money because now they see that if you look at the system as an integrated system that you can get some really interesting benefits out of that. That’s gonna be more of those types of design studies are gonna show us the path, I think, for hybrid large airplanes in the future.
Tom Temin: So maybe we’ll see an Airbus Prius model someday?
Brent Cobleigh: Yeah, I think that that’s what the type of thing you’re gonna see initially. Airplanes are already becoming more electrified the sub systems on the airplane, you know, already happening today. But you’re gonna see that increasing as time goes on. That’s just getting more and more challenging to make an airplane more efficient. And electric provides a path of sort of a whole new design element that allows you to make these things more efficient.