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.

Glue for art’s sake

Hans Poulis (TU Delft Adhesion Institute) recently received funding from the NWO for his research proposal in the field of adhesive aging. The proposals were accepted in the first round of funding of the Netherlands Institute for Conservation, Art and Science (NICAS). Poulis: “This is the first time that the Adhesion Institute will be developing a new type of adhesive from scratch.” There are currently all sorts of standard adhesive types in use for the restoration of works of art. Synthetic adhesives are often more stable than natural adhesives, but are not always entirely suitable. They were not developed for restoration purposes and therefore never have all the necessary characteristics. So we usually don’t know how they will alter over time, either chemically or mechanically. In other words, how the substances age over time under environmental influences. They might turn yellow, for instance, or the qualities of the adhesive bond may alter. Hole in the market It is a niche market, and not really commercially viable for businesses. Recanvassing paintings requires relatively large amounts of adhesive, but you can imagine that for repasting tiny paint flakes only tiny amounts of adhesive are needed. The Adhesion Institute will be looking into that latter process, and particularly into reverse glass paintings and compositions in oil paint and gouache. These works are typical for many works of art that will need restoring in the short term if we want to preserve them for future generations. Developing a specific adhesive for this purpose is not cost-effective for a company, if only for the high costs of the research involved. Poulis: ‘Firstly we’ll take two post-doc researchers into the field. I hope to organise a brainstorm session in March with professionals who have years of experience, including curators. They know exactly which requirements the adhesive must meet. Based on the outcome of that session, we will determine the start phase of our research. That will centre on the question: what chemical substance will we base it on? That will be our main ingredient. We will then create different mixtures and depending on the requirements, adapt the recipe accordingly. Using various lab tests we will determine how the mixtures react, initially and over time.’ From test to product By carrying out aging tests, we aim to find out how mixtures react after a certain number of years. For instance, light exposure tests will enable us to see to what extent such a substance turns yellow over time. For these tests, Xenon lamps are used. They generate UV light and initiate an accelerated aging process. Poulis: ‘Ultimately, we will also test the adhesives on works of art (mock-ups). Of course, in practice you never know precisely what will happen to the adhesive, because of the numerous circumstances that could influence it. Moreover, there are no data available which can link accelerated aging tests to actual conditions.’ The Adhesion Institute has set itself a two-year time limit in which to develop an adhesive which is suitable and stable in the long term when it comes to mechanical and visual performance. The consortium for this research project includes a commercial company specialised in the manufacture of small quantities of adhesive. They would be able to put it into production. Poulis: ‘And who knows, it might generate a spin off.’ --- The NICAS is an interdisciplinary research centre aimed at the conservation of cultural heritage. It works in collaboration with the Netherlands Organisation for Scientific Research (NWO), the Rijksmuseum, the University of Amsterdam (UvA), the Cultural Heritage Agency of the Netherlands (RCE), and Delft University of Technology (TU Delft). Click here to visit the NICAS website.

A voyage of discovery through our solar system with lasers

How can we learn more about planets and moons? Dominic Dirkx recently wrote his PhD dissertation on a new method of accurately measuring the distance between the earth and satellites orbiting or on planets and moons to within between a millimetre and a centimetre. Current radio measurements are accurate to about a metre. Dirkx took laser tracking, a technique that’s currently used for measuring the distance to earth’s satellites (accurate to within a few millimetres), and extrapolated that to interplanetary distances. His research primarily shows that it’s vital that we not only measure the distance extremely accurately. Other measurements will also need to be improved in order to make the most effective use of laser tracking. If we manage to do that, this method can potentially play an important role in the exploration of our solar system. That might sound obvious, but his research has shown that focusing on making laser measurements and measurements of elements such as magnetic fields, shape or a planet’s seismic activity more accurate can really have a significant impact on your results. Influence of the clock on earth When trying to improve laser measurements, Dirkx asked to what extent the ultimate measurements are influenced by the clock we use here on earth. Dirkx: ‘When you measure distance, you’re actually measuring movement. You use a clock on earth and a clock in space to measure how long a laser pulse is en route. Because you know what the speed of light is, you look to see where a satellite is from one moment to the next. And that means that if you’re just a nanosecond out, it can easily make 30 centimetres difference.’ If you examine how something moves, you examine how gravity works and as such, you learn about the surroundings. Imagine that you measure how a satellite orbits the planet Mars: that will allow you to find out more about the composition of the planet. Last year, for example, this method was used – alongside other measurements – to discover an ocean under the surface of Enceladus, a moon of the planet Saturn. A remarkable thesis defence Dirkx graduated nominally and with distinction. David Smith (MIT) felt it was worth the trip to Delft to sit on the committee during his thesis defence. Smith is specialised in laser ranging as well as planetary sciences. Dirkx: ‘He’d worked with colleagues from our research group in the past, and I’d met him at conferences. He’s someone who’s extremely intimidating to doctoral candidates – a major figure with an endless list of significant publications to his name.’ Dirkx: ‘What really helped during my promotion was having the opportunity to work on the European FP7 ESPaCE project. This enabled me to build up a large network, so I’ve always had lots of people to discuss my research with. My tip for other PhDs is therefore to talk to people whenever you can. Not only within your own research group, but particularly outside of it.’

Understanding aircraft behaviour on final approach

PhD student Floris Herrema (Air Transport and Operations) recently won the SESAR Young Scientist of the Year Award for his MSc thesis ‘Compression on final approach and Time Based Separation (TBS) for Optimised Runway Delivery’. His work has had a direct impact on the knowledge and safety of TBS and the deployed TBS at London Heathrow Airport: the first in the world. “I never expected to win the SESAR Young Scientist of the Year Award, so I was actually quite relaxed on the day of the final round in Bologna, Italy. Single European Sky Air Traffic Management Research (SESAR) is a European funding institute focused on air traffic management (ATM). This means I got to stand in front of 400 people in the field of ATM that day, which was great.” Predicting aircraft behaviour “The objective of my study was to quantify and model the potential performance compression improvements on final approach for Time Based Separation (TBS). The concept of TBS was known, but it was too complicated to actually implement it. I have developed a new air speed profile, the Floris Friso Herrema (FFH) tool, with which we can better predict the expected aircraft behaviour and TBS. This is very relevant information for air traffic controllers. It is now easier to understand and thus implement. And it was implemented at London Heathrow Airport last year, which is now the first TBS airport in the world.” The advantages “The most important advantage is the recovery we achieve during strong headwinds. It is still estimations based on Heathrow, but we expect that during strong headwinds we can achieve two more landings per hour. In addition, TBS is on track to save 80.000 minutes of delay per year. The benefits to the airlines can add up to 7.5 million pounds per year.” Impact “I was specifically looking for a thesis subject with potential impact. It is part of the reason why I wanted to work together with EUROCONTROL on this from the start. I combined a traineeship at EUROCONTROL together with my master’s project. You see without implementation, theory is just theory. This is also why it is great now working together with Ricky Curran and Dries Visser (both Air Transport and Operations) during my PhD project. With everything I do, they ask: what is the social and academic impact? The university and EUROCONTROL each give me feedback and advice that is always slightly different. There is certainly extra value in combining these views. I hope to always keep moving around in both worlds and be an active link between the two.” Future “My PhD project, ‘Big data analyses and machine learning at airports to support decision making’, is well underway. I am working on feasible machine learning techniques. The goal is to implement it at all major airports in Europe. I really enjoy working on this. Right now we are trying to embed my research in a European research project. We are working hard on a few proposals in the context of the Horizon 2020 programme to try and obtain funding for this. If we could achieve this, that would be great of course.” The most important advantage is the recovery we achieve during strong headwinds.