Stories of Aerospace Engineering

Read the stories of researchers and students at the Faculty of Aerospace Engineering, and discover the scientific questions they are working on and the solutions they come up with.

Is it dangerous to sit in a cinema for two hours with thirty people?

It is now well known that the risk increases considerably if a person with the coronavirus stays in a room for a long time, has a large lung capacity, and coughs or sneezes without covering up with his elbow, but how much higher is the risk?

Complicated puzzle in air traffic control solved after 25 years

Solving a 25-year-old aviation problem? That is just what Wouter Schaberg, student in Control and Operations in the Faculty of Aerospace Engineering managed to do. He made improvements to part of an algorithm that is used to prevent aircraft coming too close to each other following an averted conflict.

The first Flying-V test flight

Since 2017, a team of researchers from TU Delft has been working on a new, more sustainable type of passenger aircraft, the Flying-V. After the research phase, July saw an exciting and significant next step in the programme: the scale model’s first test flight. Would the aircraft remain stable when airborne, even at low speeds?

Lockdown presents unique opportunity to study sustainable taxiing at Schiphol

Starting a PhD on the first day of the Covid-19 lockdown was a bit challenging for Bieke von den Hoff. But the lockdown also gave her an unexpected and unique opportunity. As part of a trial programme at Schiphol Airport, she was asked to measure noise levels of a sustainable aircraft towing vehicle called the TaxiBot.

Student volunteers offer help in times of corona

When Thijs de Jongh saw an app asking for volunteers to support vulnerable groups halfway through March, he jumped at the opportunity. But instead of filling out the form De Jongh and his fellow students decided to get cracking with the organisation of gewoonmensen.nl, a website for people who need help, during and after corona.

IAWA scholarship recipient says success is about helping each other

The International Aviation Womens Association (IAWA) chose master’s student Julia Radius as its 2019 TU Delft scholarship recipient. The scholarship, which supports women studying in aviation or aerospace related fields, is giving Radius a deeper understanding of what it means to be successful.

The next phase in aircraft design

The aircraft design of the Flying-V is potentially much more efficient than the traditional “pipe with wings” design. The concept was received with great enthusiasm, but a lot of hard work will need to be done if the sustainable flying wing is to be ready by 2040.

The next phase in aircraft design

The aircraft design of the Flying-V is potentially much more efficient than the traditional “pipe with wings” design. The concept was received with great enthusiasm, but a lot of hard work will need to be done if the sustainable flying wing is to be ready by 2040. I n June 2019, TU Delft and KLM presented their plans for the Flying-V: an aircraft designed to save 20% on both fuel and emissions due to its unique shape. KLM is sponsoring the project for sustainable flying as part of its 100th anniversary programme. During celebrations to mark the event last October, the scale model and the mock-up of the interior of the Flying-V attracted huge interest, and the story was covered by numerous media, from Dutch Design Week to the DWDD talk show. “Something we had been working on for years was suddenly in the spotlight”, explains Roelof Vos, project leader of Flying-V and Assistant Professor of flight performance and propulsion. Checking the calculations A patent that appeared in the media first drew Vos’s attention in 2014. Graduate Justus Benad from TU Berlin had come up with a draft design for Airbus, for a flying wing with seating for 300 passengers. “Most new aircraft concepts aren’t radically different from current designs. This one intrigued me”, says Vos. “It promised a staggering 10% improvement in aerodynamic efficiency and a 2% reduction in take-off weight compared with a conventional aircraft. My immediate reaction was: as critical researchers, we have to check these claims thoroughly.” Vos also thought that he could improve the draft design: “We gave it an oval fuselage instead of a round pipe, and it became the Delft Flying-V.” The aerodynamics research based on this version improved the results even further than the original promising 10%. The prognosis for a lower take-off weight also turned out to be correct, although this was difficult to calculate for an aircraft that was still only a design on paper. “After consulting with experts from Airbus, we concluded that whatever else, the aircraft would not become heavier. Our claim is that the unladen weight will be 7% lower, but the total weight will depend on the interior and all the systems.” Construction weight The lower weight is largely due to the unique shape of the aircraft: “Passengers normally sit in the middle of the plane and the wings generate the lift; this force must then be transferred to the cabin. This requires extra construction weight, which is no longer needed in our design.” This is nothing new; it’s one of the ideas behind aircraft such as the Blended Wing Body planes (BWB), in which the wings, cabin and engines are designed as a single unit. “But the Blended Wing Body design is not attractive from an industrial perspective, as every aircraft needs to be designed individually, whereas the Flying V is easy to lengthen or shorten so you can build series of aircraft using 95% of the same parts”, explains Vos. Test model Work is currently underway in the Aeroplane Hall of the Faculty of Aerospace Engineering to construct a scale model of the Flying-V with a wingspan of three metres. Researcher Malcom Brown is heading the project. His students are closely involved, as they are with other parts of the project. “It’s great to see how much students learn from doing something practical like building a model that actually works”, says Brown. “Some of them aren’t as practical as others when it comes to things like drilling or filing, but that’s just as much part of the learning process. The model will be used for actual research flights, so we have to be as accurate as possible.” Measurement arm A 3D measurement arm with laser scanner was purchased specially for the job. “The measurement arm allows us to determine the precise shape and location of components to a tenth of a millimetre. In this way, we can check whether all the parts we have ordered satisfy our requirements and are positioned correctly”, explains Brown. Despite all this accuracy, building a test model is a nerve-racking business, right up to the last moment. “Real life is never the same as the calculations, so we won’t know whether the aircraft can really fly, or the flight characteristics, until the test flights. Wind tunnel tests, for example, have shown that the aircraft might be less stable at a certain high angle. This didn’t show up in the computer simulations”, he continues. “Scaling up wind tunnel measurements to life-size test models is always a huge challenge in aerospace engineering.” A doctoral candidate is currently looking into ways of improving the theory behind this scaling up process; the research will be of use to other projects too. Interior Professor of Environmental Ergonomics Peter Vink, who is working on the plane’s interior, isn’t troubled by the scaling-up problems. Part of the interior has been built to true size and is currently on display in the Faculty of Industrial Design Engineering. “We are using the project as an opportunity to improve comfort for passengers”, he says. Four winning ideas were chosen from a design competition for students. They related to beds, lounge seats, group seating and individual seats. The beds make it possible for economy-class passengers to sleep horizontally, according to Vink: “We place three beds one above another, whereby the middle bunk can be slid up allowing the bottom bunk to be used for seating during take-off and landing. This is necessary to provide fast escape routes in the event of evacuation. You don’t lose any seating, because three beds take up just as much space as three seats”, he explains. In the group seating, passengers sit opposite each other like they do on trains. “More than a quarter of all passengers fly in groups. Sitting opposite each other makes it easier to chat or play games with the children”, continues Vink. “The lounge seats allow you to sit in different positions, from chill to working with a laptop. It is important to change your position regularly, and with this seat, your position is determined by what you are doing.” The individual seats are not directly next to each other, but alternate and are mounted at an angle of 26 degrees to the aircraft’s flight direction. This is a safety regulation. “Sitting at too wide an angle to the plane’s flightpath is less safe if the plane crashes”, he explains. “But there’s another advantage to this arrangement: you have more leg and shoulder room.” Boarding and disembarking in these spots is also made easier because you can flip over the seat cushion. “You can also use the folded seat position if you want to sit a bit higher”, says Vink. Sustainability Sustainability was also taken into account in the interior design. “Interior constitutes weight, and the heavier the plane is, the more fuel you need. The seats we’ve designed are three to five kilos lighter than the current models. In the rest of the interior, we’ve tried to use as much openwork as possible, rather than solid structures, using generative design methods. This saves material and therefore weight.” Many of these ideas could be used in regular aircraft, but there are still some unanswered questions about the interior of the Flying-V. “For example, our plans don’t leave enough room for hand luggage”, says Vink. “Then again, we have until 2040 to think about it.” Still so much to do The media attention may have quietened down, but work behind the scenes is still in full swing. “This was an integrated project from the word go; all disciplines are involved. You don’t want to complete a fantastic aerodynamic design, only to discover that the finished product is far too heavy”, explains Vos. “So we recently met experts from across the sector to discuss the challenges they envisaged. We ended up with a list of almost 50 subjects that need further scrutiny.” They varied from highly practical to totally theoretical. “This new aircraft must be capable of landing and being serviced at existing airports. Imagine if you have to change an engine and they’re fitted on top of the wings. You can get to them using a crane at Schiphol, but what about at other airports in the world?” And there are more conceptual questions about the dynamic stability of the design. “You need to know precisely how the mass is distributed and how the aerodynamics change at different speeds”, says Vos. “We can measure some of this during the test flights, but a small test model doesn’t fly fast enough to be able to draw any definite conclusions. We can try to estimate it using existing methods, but these were designed for the existing models. So in order to do this, we need to come up with a clever way of combining the results of various tests and analyses.” Next phase All three of them agree about the need for a new configuration. “You can’t just carry on using the current solutions”, claims Vink. “Existing configurations only allow incremental, minor improvements”, adds Vos. “This may well be the first step in the next phase of aviation”, says Brown. “The sector knows that it needs to modernise. Not only for economic reasons because fuel is currently the biggest expense for aviation companies, but also because of the increasingly strict emissions policies.” So will we be flying in a Flying-V in 2040? “Airbus, Schiphol, KLM and other parties are already very enthusiastic. We’ll form a consortium next year, so that we can work more intensively on developing the design with all of these parties”, explains Vos. But the researcher is still erring on the side of caution. “There’s still so much that we don’t know about this aircraft; in another five years, we might even come to the conclusion that it’s not feasible after all.” Existing configurations only allow incremental, minor improvements Read more stories of Aerospace Engineering Roelof Vos, Malcom Brown, Peter Vink This is a Portrait of Science from Aerospace Engineering I n June 2019, TU Delft and KLM presented their plans for the Flying-V: an aircraft designed to save 20% on both fuel and emissions due to its unique shape. KLM is sponsoring the project for sustainable flying as part of its 100th anniversary programme. During celebrations to mark the event last October, the scale model and the mock-up of the interior of the Flying-V attracted huge interest, and the story was covered by numerous media, from Dutch Design Week to the DWDD talk show. “Something we had been working on for years was suddenly in the spotlight”, explains Roelof Vos, project leader of Flying-V and Assistant Professor of flight performance and propulsion. Checking the calculations A patent that appeared in the media first drew Vos’s attention in 2014. Graduate Justus Benad from TU Berlin had come up with a draft design for Airbus, for a flying wing with seating for 300 passengers. “Most new aircraft concepts aren’t radically different from current designs. This one intrigued me”, says Vos. “It promised a staggering 10% improvement in aerodynamic efficiency and a 2% reduction in take-off weight compared with a conventional aircraft. My immediate reaction was: as critical researchers, we have to check these claims thoroughly.” Vos also thought that he could improve the draft design: “We gave it an oval fuselage instead of a round pipe, and it became the Delft Flying-V.” The aerodynamics research based on this version improved the results even further than the original promising 10%. The prognosis for a lower take-off weight also turned out to be correct, although this was difficult to calculate for an aircraft that was still only a design on paper. “After consulting with experts from Airbus, we concluded that whatever else, the aircraft would not become heavier. Our claim is that the unladen weight will be 7% lower, but the total weight will depend on the interior and all the systems.” Construction weight The lower weight is largely due to the unique shape of the aircraft: “Passengers normally sit in the middle of the plane and the wings generate the lift; this force must then be transferred to the cabin. This requires extra construction weight, which is no longer needed in our design.” This is nothing new; it’s one of the ideas behind aircraft such as the Blended Wing Body planes (BWB), in which the wings, cabin and engines are designed as a single unit. “But the Blended Wing Body design is not attractive from an industrial perspective, as every aircraft needs to be designed individually, whereas the Flying V is easy to lengthen or shorten so you can build series of aircraft using 95% of the same parts”, explains Vos. Test model Work is currently underway in the Aeroplane Hall of the Faculty of Aerospace Engineering to construct a scale model of the Flying-V with a wingspan of three metres. Researcher Malcom Brown is heading the project. His students are closely involved, as they are with other parts of the project. “It’s great to see how much students learn from doing something practical like building a model that actually works”, says Brown. “Some of them aren’t as practical as others when it comes to things like drilling or filing, but that’s just as much part of the learning process. The model will be used for actual research flights, so we have to be as accurate as possible.” Measurement arm A 3D measurement arm with laser scanner was purchased specially for the job. “The measurement arm allows us to determine the precise shape and location of components to a tenth of a millimetre. In this way, we can check whether all the parts we have ordered satisfy our requirements and are positioned correctly”, explains Brown. Despite all this accuracy, building a test model is a nerve-racking business, right up to the last moment. “Real life is never the same as the calculations, so we won’t know whether the aircraft can really fly, or the flight characteristics, until the test flights. Wind tunnel tests, for example, have shown that the aircraft might be less stable at a certain high angle. This didn’t show up in the computer simulations”, he continues. “Scaling up wind tunnel measurements to life-size test models is always a huge challenge in aerospace engineering.” A doctoral candidate is currently looking into ways of improving the theory behind this scaling up process; the research will be of use to other projects too. Interior Professor of Environmental Ergonomics Peter Vink, who is working on the plane’s interior, isn’t troubled by the scaling-up problems. Part of the interior has been built to true size and is currently on display in the Faculty of Industrial Design Engineering. “We are using the project as an opportunity to improve comfort for passengers”, he says. Four winning ideas were chosen from a design competition for students. They related to beds, lounge seats, group seating and individual seats. The beds make it possible for economy-class passengers to sleep horizontally, according to Vink: “We place three beds one above another, whereby the middle bunk can be slid up allowing the bottom bunk to be used for seating during take-off and landing. This is necessary to provide fast escape routes in the event of evacuation. You don’t lose any seating, because three beds take up just as much space as three seats”, he explains. In the group seating, passengers sit opposite each other like they do on trains. “More than a quarter of all passengers fly in groups. Sitting opposite each other makes it easier to chat or play games with the children”, continues Vink. “The lounge seats allow you to sit in different positions, from chill to working with a laptop. It is important to change your position regularly, and with this seat, your position is determined by what you are doing.” The individual seats are not directly next to each other, but alternate and are mounted at an angle of 26 degrees to the aircraft’s flight direction. This is a safety regulation. “Sitting at too wide an angle to the plane’s flightpath is less safe if the plane crashes”, he explains. “But there’s another advantage to this arrangement: you have more leg and shoulder room.” Boarding and disembarking in these spots is also made easier because you can flip over the seat cushion. “You can also use the folded seat position if you want to sit a bit higher”, says Vink. Sustainability Sustainability was also taken into account in the interior design. “Interior constitutes weight, and the heavier the plane is, the more fuel you need. The seats we’ve designed are three to five kilos lighter than the current models. In the rest of the interior, we’ve tried to use as much openwork as possible, rather than solid structures, using generative design methods. This saves material and therefore weight.” Many of these ideas could be used in regular aircraft, but there are still some unanswered questions about the interior of the Flying-V. “For example, our plans don’t leave enough room for hand luggage”, says Vink. “Then again, we have until 2040 to think about it.” Still so much to do The media attention may have quietened down, but work behind the scenes is still in full swing. “This was an integrated project from the word go; all disciplines are involved. You don’t want to complete a fantastic aerodynamic design, only to discover that the finished product is far too heavy”, explains Vos. “So we recently met experts from across the sector to discuss the challenges they envisaged. We ended up with a list of almost 50 subjects that need further scrutiny.” They varied from highly practical to totally theoretical. “This new aircraft must be capable of landing and being serviced at existing airports. Imagine if you have to change an engine and they’re fitted on top of the wings. You can get to them using a crane at Schiphol, but what about at other airports in the world?” And there are more conceptual questions about the dynamic stability of the design. “You need to know precisely how the mass is distributed and how the aerodynamics change at different speeds”, says Vos. “We can measure some of this during the test flights, but a small test model doesn’t fly fast enough to be able to draw any definite conclusions. We can try to estimate it using existing methods, but these were designed for the existing models. So in order to do this, we need to come up with a clever way of combining the results of various tests and analyses.” Next phase All three of them agree about the need for a new configuration. “You can’t just carry on using the current solutions”, claims Vink. “Existing configurations only allow incremental, minor improvements”, adds Vos. “This may well be the first step in the next phase of aviation”, says Brown. “The sector knows that it needs to modernise. Not only for economic reasons because fuel is currently the biggest expense for aviation companies, but also because of the increasingly strict emissions policies.” So will we be flying in a Flying-V in 2040? “Airbus, Schiphol, KLM and other parties are already very enthusiastic. We’ll form a consortium next year, so that we can work more intensively on developing the design with all of these parties”, explains Vos. But the researcher is still erring on the side of caution. “There’s still so much that we don’t know about this aircraft; in another five years, we might even come to the conclusion that it’s not feasible after all.” Existing configurations only allow incremental, minor improvements Roelof Vos, Malcom Brown, Peter Vink This is a Portrait of Science from Aerospace Engineering Other Portraits of Science Design for a better world The future of architectural glass

Flying in a V

The lorry pulls up very slowly, en route from the Faculty of Aerospace Engineering to Schiphol. The cargo on board is precious: the 3-meter-wide flying scale model of the revolutionary Flying-V aircraft. Chief engineer Malcom Brown: “The Flying V will use far less energy thanks to its aerodynamic V-shape.”

Bringing silent aviation closer

Hundreds of millions of people living near airports are still at increased risk of developing hearing problems cardiovascular diseases. Roberto Merino-Martinez, who himself lives near Rotterdam Airport, is researching a relatively new topic in the field of aerospace engineering: Aeroacoustics. An annoying whistle Although aircraft engine noise has decreased substantially over the past decades, air flow around the airplane structure itself is still a considerable source of noise. In wind turbines, this mechanism causes the typical swooshing sound. During the first part of his PhD, in which Merino-Martinez focused on flyover measurements at Schiphol airport, he was surprised to find that many types of planes produced a huge tonal peak at a frequency of 1720 Hz. That is a sound about as annoying as a heart monitor flatlining. “It was especially loud for the Airbus A320, one of the most popular passenger aircraft of all time,” Merino-Martinez says. “It turned out to be caused by a cavity in the nose landing gear, acting like a whistle. It is my most cited research paper to date, and I believe Airbus may fix this in their newer models.” An array of van microphones “The noise models used when designing new planes are simply not good enough. They lack sufficient detail and often predict noise levels to be lower than they actually are”, explains Merino-Martinez. “Improvements in acoustic imaging and its algorithms are essential. A single microphone suffices to measure a general noise level. Add a second and some directionality can be obtained. But to really understand aircraft noise, to make a high-resolution image of all its sound sources, you need to use a microphone array.” Noise created by aircraft wings As it turned out, Merino-Martinez worked most of his PhD on integrating a versatile microphone array into the existing TU Delft laminar flow anechoic wind tunnel, in order to be able to perform the desired measurements. “The solution we came up with allows for the microphones to be rearranged depending on the details of the experiment,” he says. “Sometimes you want to move them further apart for a higher resolution image, or closer together to improve the array’s frequency response.” He also spent a lot of time improving the algorithm for reconstructing the sound sources. “I wanted to accurately measure the sound levels created by airfoils, such as the wings of an airplane or the blades of a wind turbine. A lot of noise can be created by instabilities in the airflow at the trailing edge.” Most acoustic imaging algorithms are based on point sources because they are mathematically simpler. Merino-Martinez rewrote the algorithm so that it was also possible to accurately reproduce line sources of sound. "Our approach gives better results than existing solutions, even those developed by NASA." The silent flight of owls Using the new array and algorithm, Merino-Martinez and his colleagues performed measurements on variations of two noise-reduction techniques. “They are both inspired by the silent flight of owls,” he says. “Their feathers create a saw-tooth profile, called serrations, which interferes with the scattering of the airflow at the trailing edge.” The researchers also investigated the insertion of porous materials or metal foams at the trailing edge, causing a similar interference. “It’s a great solution from a scientific point of view,” he says, “but real-world application is difficult, as these materials can get dirty or attract lightning.” Whereas serrations are already being commercially used by some wind turbine manufacturers, it may take another ten years for the conservative airplane industry to follow suit. “Safety first.” Roberto Merino-Martinez +31 (0)15 27 81736 r.merinomartinez@tudelft.nl This is a story from Aerospace Engineering An annoying whistle Although aircraft engine noise has decreased substantially over the past decades, air flow around the airplane structure itself is still a considerable source of noise. In wind turbines, this mechanism causes the typical swooshing sound. During the first part of his PhD, in which Merino-Martinez focused on flyover measurements at Schiphol airport, he was surprised to find that many types of planes produced a huge tonal peak at a frequency of 1720 Hz. That is a sound about as annoying as a heart monitor flatlining. “It was especially loud for the Airbus A320, one of the most popular passenger aircraft of all time,” Merino-Martinez says. “It turned out to be caused by a cavity in the nose landing gear, acting like a whistle. It is my most cited research paper to date, and I believe Airbus may fix this in their newer models.” An array of van microphones “The noise models used when designing new planes are simply not good enough. They lack sufficient detail and often predict noise levels to be lower than they actually are”, explains Merino-Martinez. “Improvements in acoustic imaging and its algorithms are essential. A single microphone suffices to measure a general noise level. Add a second and some directionality can be obtained. But to really understand aircraft noise, to make a high-resolution image of all its sound sources, you need to use a microphone array.” Noise created by aircraft wings As it turned out, Merino-Martinez worked most of his PhD on integrating a versatile microphone array into the existing TU Delft laminar flow anechoic wind tunnel, in order to be able to perform the desired measurements. “The solution we came up with allows for the microphones to be rearranged depending on the details of the experiment,” he says. “Sometimes you want to move them further apart for a higher resolution image, or closer together to improve the array’s frequency response.” He also spent a lot of time improving the algorithm for reconstructing the sound sources. “I wanted to accurately measure the sound levels created by airfoils, such as the wings of an airplane or the blades of a wind turbine. A lot of noise can be created by instabilities in the airflow at the trailing edge.” Most acoustic imaging algorithms are based on point sources because they are mathematically simpler. Merino-Martinez rewrote the algorithm so that it was also possible to accurately reproduce line sources of sound. "Our approach gives better results than existing solutions, even those developed by NASA." The silent flight of owls Using the new array and algorithm, Merino-Martinez and his colleagues performed measurements on variations of two noise-reduction techniques. “They are both inspired by the silent flight of owls,” he says. “Their feathers create a saw-tooth profile, called serrations, which interferes with the scattering of the airflow at the trailing edge.” The researchers also investigated the insertion of porous materials or metal foams at the trailing edge, causing a similar interference. “It’s a great solution from a scientific point of view,” he says, “but real-world application is difficult, as these materials can get dirty or attract lightning.” Whereas serrations are already being commercially used by some wind turbine manufacturers, it may take another ten years for the conservative airplane industry to follow suit. “Safety first.” Roberto Merino-Martinez +31 (0)15 27 81736 r.merinomartinez@tudelft.nl This is a story from Aerospace Engineering Read more stories of Aerospace Engineering Related stories The responsibility gap of self-driving cars Roboats in Amsterdam The flying V