NASA X | Environmentally Responsible Aviation – End of an ERA (Pt.2)
NASA’s Environmentally Responsible Aviation program is coming to a close. New advanced leading edge wing coatings are being developed that will deter bug strikes and help maintain laminar flow over airplane wings. And, we visit the Ames Research Center to see final testing of a new BWB model in the 40×80 wind tunnel.
December 18, 2015
Jennifer Pulley: Host
Kevin James, NASA AMES
Israel Wygnanski, University of Arizona
Jeanne Yu, Boeing
Dr. Mia Siochi, NASA Langley
It is often said that the only thing constant in life is change. That is as true at NASA as anywhere else.
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But the men and women of NASA generally see change differently than others because their life’s work is all about change. Through their tireless efforts, these talented professionals move past the status quo every day and help us understand and change our world for the better. But even though change is part of their job requirement, the people of NASA understand that all projects eventually come to an end, and they will have to transition from one assignment and get ready for their next challenge. That transition is beginning to happen now for the members of the Environmentally Responsible Aviation Project. After six long years of study, team members are closing the books on the ERA research project that has provided so much new information about how future aircraft will fly. This team has worked diligently over the past half decade to reduce aircraft drag by 8%, reduce aircraft weight by 10%, reduce engine-specific fuel consumption by 15%, reduce oxides of nitrogen emissions of the engine by 75%, and to reduce aircraft noise by 1/8 compared with current standards, all by the year 2025. These were stretch goals to be sure, but not surprisingly, their efforts have paid off for all of us. Today on “NASA X,” we will look at part two of this two-part program that has explored the work done by the ERA team. We will look back at some of their early work, while also looking at what some of the finished products look like. We will see how NASA and industry have worked together to improve the state of the art for aircraft design and will find out about promising new ideas that have come out of this work. Finally, we will bid farewell to the team that is changing the way we all fly.
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Created in 2009 as part of NASA’s Aeronautics Research Mission Directorate’s Integrated Systems Research Program, the Environmentally Responsible Aviation Project was tasked with exploring and documenting the feasibility of vehicle concepts and enabling technologies to reduce aviation’s impact on the environment. Aircraft have benefited greatly by the work done by NASA engineers over the decades, but with changes in technology, NASA knew that much more could still be done. The ERA project was organized to: mature promising technology and advance aircraft configurations that meet mid-term goals for community noise, reduce fuel burn and nitrogen oxides or NOX emissions. They were also tasked with determining the potential impact of these advanced aircraft designs and technologies into the air transportation system. They have done all this and more. The solutions that they have achieved will undoubtedly reduce fuel consumption by up to several percentage points for the aircraft community. That may not sound like much, but shaving aircraft fuel consumption even a few percentage points can save millions of dollars and help protect the environment from harmful emissions. One area that the team focused on heavily to meet these goals was to develop, in collaboration with their industry partners, a new type of aircraft called the Hybrid Wing Body concept. NASA planners did early wind tunnel tests and scale model tests with great success. The final phase of this testing is being done here at NASA Ames Research Center’s 40×80 tunnel in California. The NFAC is actually home to two interconnected wind tunnels. One test section, the world’s largest, measures 80 feet tall by 120 feet wide. The other one, the world’s second-largest, has a test section that measures 40 feet tall by 80 feet wide. This full-scale tunnel has been used since World War II and has helped perfect numerous aircraft designs and is now being used to help with this unique aircraft. Here is Kevin James from NASA Ames to explain.
James: If you take an airplane from, say, 1950… 1950, and you take an airplane from, say, today, and you lay them on top of each other, they have almost exactly the same outline. And there have been a lot of improvements, but as we start looking for something that’s dramatically different, where you’re really gonna make improvements in fuel economy, fuel emissions, and acoustics, you know– say, community noise– and the impact that we have on how people live their lives, we have to keep looking and sometimes think outside of the box. So this is a hybrid blended wing body. We call the generic airplanes of today “tube and wings,” and that sort of makes sense, ’cause there’s just a big old tube with a wing on it, and we all just go along for the ride. What we’ve done here is, we’ve actually taken that tube, and with the abilities that we’ve had in improvements in structures and materials– specifically composites– we can now go from a tube shape to more of an elongated shape, because the pressure vessel wants to be a tube, and we want to kind of stretch it a little. Well, when we stretch it and then we blend the wings into it, we get this hybrid blended-wing body airplane. And through very careful control of weight and very careful configuration control, including how you put the engines on it, we have significant improvements in fuel burn and also very significant improvements in noise. Our mandate was a 50% reduction in fuel burn gate to gate and a 42 dB–decibel– reduction in noise in a cumulative fashion from a 1999 target airplane. Where we ended up was really, really close. We made over 48% improvement in fuel burn, so missed it by just that much, and really close to the– we’re at 40 dB down, cumulative. But a good way to keep in mind what that really means is, every six decibels of change is a doubling of the noise– our perception of the noise. So when we start talking about numbers like 42 dB down, even if it’s cumulative, that is a huge improvement. What that really is in terms of quality of life for people in the cities, especially around airports, is a significant improvement to what they’ve come to expect. It’s been a lot of hard work. There’s always frustrations, but that’s kind of what makes the job fun sometimes– is solving the challenges. We have worked with some phenomenally good people, and it’s just–it is– we are really, truly blessed. NASA has, hands down, the best people on the planet. Just really good people. Smart, interactive, social, full of good ideas and wanting to solve problems. It has been a lot of fun seeing the pieces all come together, and ERA was laid out in a really– kind of a very slick way. We’ve got the vehicle and the systems integration, we’ve got, you know, structures, and we’ve got the engine and propulsion, and, again, to meet the stated goals, all three legs had to deliver. And as we get to the end of the program, it is just incredible seeing the progress that was made and the deliverables that we’re getting from all of the components, and as they come together, you see that we are actually going to be able to be in a position to say something like this works, and this is where we should be headed.
The research from the Hybrid Wing Body aircraft will continue, and one day in the near future, we may all see these types of revolutionary aircraft flying in our skies.
Another concept the ERA team has been working on called Active Flow Control Enhanced Vertical Tail Flight Experiment has shown much promise as well. The ERA team worked in cooperation with Boeing to develop a plan to test this innovative idea in the wind tunnel and on an actual aircraft in flight. Before flight tests were done, the team installed 31 sweeping jet actuators onto a tail section of a 757 aircraft. These jets can manipulate, on demand, the air that flows over the vertical tail and rudder surfaces. This test is important because it has the potential to reduce the weight associated with the tail section. An aircraft’s vertical tail is primarily used to add stability and directional control during takeoff and landing, especially in the event of an engine failure. But when the aircraft is cruising at altitude, the same large, heavy tail is not necessary. Engineers theorized they could reduce the size of the vertical tail by using the sweeping jets to generate the same side force during takeoff and landing. That would reduce both the weight and drag of the airplane and decrease its fuel consumption. In order to test this large tail section, the team had to place it inside the NASA facility that is home to the world’s largest wind tunnels: the National Full-Scale Aerodynamics Complex, or NFAC. Ground studies by a team of NASA, Boeing, University of Arizona, and Caltech researchers on this full-scale 757 vertical tail in the NFAC, did in fact show that the active flow control jets could potentially increase side force by as much as 20% to 30%. That low number of 20% increase in side force could allow designers to scale down the vertical tail by about 17% and therefore reduce fuel usage by as much as 1/2%. But this is not the only potential benefit. In addition to reduced weight and fuel economy, this type of device could also allow for new aircraft to use shorter runways. Here is the man who is called the father of active flow control, the University of Arizona’s Iggy Wygnanski.
Wygnanski: We–we can possibly take off from a football-field-size with some sort of a… rotor-type airplane– maybe partly tiltrotor or partly tiltwing. And we can fly, possibly, at 350 to 400 knots and do this very efficiently. So since most of our flights are of the order of 1,000 miles, if you do it from downtown to downtown, from a parking lot to another parking lot, that’s much more effective than to do it the way we do today, because on the distance, let’s say, from here to Tucson, I spent about two hours at the airports, and this is not really necessary. And there are a lot of, by the way, small airports of runways that are less than 5,000 feet– are in a lot of city centers or close to city centers that can be utilized and can be utilized effectively. So some sort of short-takeoff airplane that would use this technology could be very effective.
After testing on the tail was complete at the NFAC, NASA and Boeing placed the tail on a Boeing test aircraft called the ecoDemonstrator. This aircraft is unique because it is being used as a flying test bed to evaluate different technologies that could increase efficiency. With the active flow tail attached, testing continued back at Boeing Field with much of the research data being validated in flight.
Yu: Building on that 100-year collaboration we’ve had between NASA and Boeing, the ecoDemonstrator Program really is about continuing that legacy and spurring some more action to see that continued collaboration together successfully.
This collaboration and testing is important not only because technology must move forward but because of the significant savings this could potentially afford aircraft operators and the flying public.
Yu: When you think about the worldwide fleet of airplanes, there are about 18,000 airplanes that fly today, and it’s projected to grow to 36,000 airplanes in the next 20 years, so if you can get a little bit of improvement on one airplane and it’s multiplied times 36,000 in the next 20 years, so it’s huge improvements with regard to reducing overall fuel burn.
Having a relevant test bed, like Boeing’s ecoDemonstrator, is helping to mature technology concepts that have been extremely important to NASA’s Environmentally Responsible Aviation Project. Researchers have been working hard to develop technologies to reduce airplane fuel consumption, noise, and emissions. Being able to prove those concepts in flight tests gives them a better shot of getting into the commercial fleet.
♪ ♪ Because the ecoDemonstrator was designed to test multiple experiments at once, Boeing and the ERA team also decided to test special material coatings on the right wing of this aircraft that could reduce bug contamination. This test was called the Insect Accretion and Mitigation experiment, which in laymen’s terms means that it is simply an experiment to test how to keep bug guts from reducing aircraft efficiency. It might seem odd that NASA would spend its time worrying about seemingly innocuous bug strikes, but believe it or not, these small creatures can significantly reduce an aircraft’s efficiency. In a set of flight tests near Shreveport, Louisiana, the team assessed how well five different coatings repel insect residue. Studies have shown that keeping the flow smooth, or laminar, over a wing can reduce fuel consumption as much as 6%. Even something as small as a bug on a leading edge can cause turbulent wedges that interrupt laminar flow. That results in an increase in drag and fuel consumption. Engineers at NASA developed and tested a number of nonstick coatings in a small wind tunnel back at NASA Langley. Their initial findings allowed them to reduce the number of material from about 20 test samples down to 5. With these five best candidates in hand, the team was now ready to place the samples on the right wing of the ecoDemonstrator for flight validation. The next step was to find the best bug-infested area in which to flight test the surfaces. After narrowing the list of 90 airports to 6, Shreveport, Louisiana, was chosen due to its temperature, geology, runway size, and potential for large numbers of bugs. During 15 planned flights, researchers installed sections of coatings onto the leading edge slats of the ecoDemonstrator 757. First, they established a baseline using uncoated surfaces to capture insect accumulation rates. Then they removed those sections and installed samples of the five treated panels. One of the things engineers want to test is how durable the coatings are. Treated surfaces will only be effective as drag reducers if they can withstand the harsh flying environment.
Siochi: So what we’re doing here is testing some of the coatings that we developed to prevent bugs from sticking to aircraft wings. This has been about a five-year effort, and we started in the lab knowing that the problem is that if bugs stick to aircraft wings, you effect the laminar flow and therefore fuel efficiency. So we’ve taken samples– you know, designs of material coatings– from the lab to wind tunnel tests, and we finally have the big test, which is testing it on an actual aircraft, and so that’s what we are here to do. What we do is, we mount our samples onto the wing of one side of the aircraft, and we designed the test so that half of the panels are untreated that are mounted and half of them have the surfaces that we are flying. And so what we do is have several takeoffs and landings, because those are the parts of the flight profile where you actually accumulate bugs. And so what we want to do is test to see if the coatings that we developed actually reduce the number of bug strikes that you get, and that’s why we fly together with the untreated coatings. And the reason we’re interested in that is because an aircraft is designed for cruise, but in order to get to cruise, you got to pass by takeoff and landing, which is when the bugs are gonna accumulate, and so you basically negate the effect of designing the aircraft to benefit from being in cruise because you already have the bugs by the time you get to cruise. That’s why we have to do a lot of takeoffs and landings, because those are the parts of the flight where we actually have the problem. What we hope to accomplish is that the flight test confirms what we actually saw in the lab, right? So we tested over 200 different compositions in the lab, in a small-scale bug gun, in the wind tunnel, and actually even in the small aircraft. We’ve down-selected to five compositions; if any one of those, or at least one of those, actually works in practical application on the aircraft, which means that we’ve reduced– significantly reduced the number of bugs sticking to the surface, and where they stick is not a critical location to trip the flow, then it would be a success, right? This is actually a long-standing problem. We’ve seen literature all the way back to the ’50s trying to solve this problem, and so if we’re able to have a solution based on current understanding of what makes things stick and not stick, that would be a huge success.
Testing also continues on this unique application, and early results have shown that the ideas that have been generated may possibly work to reduce bug strikes on future aircraft. These are just a few of the innovative ideas that came out of NASA’s Environmentally Responsible Aviation Project. Only time will tell how many new technologies and innovations will come from the hard work done by this team from NASA. They can be proud that their hard work and efforts will lead to radical changes in aircraft design and efficiency for them and future generations. The results from this team and from NASA in general prove that when we as a country set a goal, if we put the right people on the task and let them work to completion, we can accomplish anything.(c)2015 NASA | SCVTV