The Germanwings incident, where a plane was deliberately and tragically crashed by a co-pilot whilst crossing the French Alps in March 2015, has prompted a global debate about how many pilots are necessary aboard commercial flights. According to some aviation experts the answer might even be none.

Due to advances in sensor technologies, computing and artificial intelligence (AI), human pilots are becoming less necessary and some companies are experimenting by replacing pilots of cargo planes with robots and remote operators. Moreover, few people may know that commercial aviation is already heavily automated; modern aircraft are generally flown by computer autopilots that track the aircraft’s position using motion sensors and ‘dead reckoning’, corrected as necessary by GPS. Moreover, the deployment of new Global Navigation Satellite System (GNSS) constellations (the European Galileo and the Chinese Beidou), and the modernization of the existing ones (The American GPS and the Russian GLONASS), will increase the availability and the number of satellites-in-view (satellites above the theoretical local horizon if the earth was a perfect sphere without any hills or mountains; they are only theoretically receivable). Consequently, these systems are paving the way for new and improved (higher accuracy and reliability) navigation algorithms and techniques.

A recent survey reported that a pilot spends just a few minutes manually piloting the plane –  mainly whilst executing takeoff and landing – while most of the time the computers flies the aircraft (except in case of emergencies or anomalies, in which case the pilot can take control).

However, pilots are still necessary due to the fact that flying remains very instinctive, with hands-on operations subject to limitless contingencies that require human input. The on-board computers need to be told what to do, how, when and where to do it. Pilots are continuously manipulating, operating and commanding the different aircraft systems and subsystems.

This is not to say that flying autonomously, under the remote supervision of pilots in an office thousands of kilometers away, could not bring several benefits. Firstly, there are safety implications. Flight crew error has been implicated in about half of all fatal airline accidents, whilst without pilots the airplane can’t be hijacked.  Along with improved safety, it could offer dramatic cost savings for airlines and passengers, due to the reduced spending on aircrew salaries, training, healthcare, layover hotels and benefits, whilst also reducing fuel costs (autonomous flights are more efficient, that will affects fares and greenhouse gas emissions).

However, the development of pilotless aircraft will also need to address several difficulties and challenges, not only from a technological point of view (e.g. sense and avoid systems, which require high-computational power); they need to be safe and reliable enough for autonomous operations, and they would require an enormous and expensive rebuilding of the entire civil aviation infrastructure, from the air traffic control, to the development of fleets of thousands of aircraft. Moreover, they will need new certification procedures, regulatory responses and even more significantly, they would need to overcome negative public perception.

It is unclear if the public will be comfortable in boarding a commercial plane without pilots. Some of the main concerns include what happens if the autonomous system fails and there is no on-board crew to take control, and also whether an AI pilot could ever match the human ability to quickly assimilating unrelated facts, act on them and make bizarre-but-brilliant decisions in emergency situations (e.g. the case of the aircraft landing in the Hudson river in January 2009 after engine failure).

Whether or not pilotless aircraft will ever fly, several companies and research centers are undertaking the challenge of exploring the concept in a way that will nevertheless bring numerous other benefits to the aerospace industry, especially from a technological perspective.

Related links:

There will be no need for pilots in 40 years from now: The RAeS 150th Anniversary debate, 12 Jan 2016

The post Will Planes Be Pilotless? The Future of Commercial Aviation appeared first on INNOVATE - Novel Aerospace Technologies.

Over the last 20 years the number of aircraft that are handled by airports has increased dramatically and continues to rise, according to ICAO (International Civil Aviation Organization). Transportation with aircraft is becoming cheaper as low cost airlines become more popular. For the first time ever the total number of UK passengers passing through UK airport terminals exceeded 250 million for a period of 12 months (October 2014 to September 2015 – see Civil Aviation Authority).

No one likes an airport full of air pollution ^{(http://www.phisicalpsience.com/public/Air_Pollution/air_pollution_China.html)}

However, most of the airports in the UK cannot easily expand in size as it is expensive and in many cases impossible to use more land around the airport in order to build terminals or runways. Heathrow airport opened as a civil airport in 1946 and since then it has constantly been changing. Now a third runway is being considered but there is a limit on how much bigger it can get. Passenger numbers, however, continue to increase and larger aircraft such as the Airbus A380, which need more space, are becoming increasingly prevalent as well. Furthermore, all these aircraft moving around airports or waiting to take-off produce a lot of carbon dioxide which increases the air pollution around the airports.

So is there a way to solve these problems without spending vast amounts of money to build new terminals and super-high efficiency engines? Is there a way to use the current infrastructure more efficiently and effectively?

Busy airports can have very long queues near the runway ^{(https://www.flickr.com/photos/aalokg/3086725781)}

As things are now, from the moment an aircraft begins to travel from a gate until it eventually takes-off an aircraft can spend a long time waiting. An aircraft might have to wait for other aircraft to move around, much like cars do in a congested city. Aircraft are bigger than cars and are much harder to manoeuvre! Having a hundred of them in one airport makes it hard to organise. Furthermore, when aircraft use the runway they have to wait for the turbulence of the previous aircraft to dissipate. If an aircraft is large then the turbulence is bigger. Smaller aircraft are more affected by turbulence so it is best to group aircraft according to their size. Moreover, aircraft travelling to the same direction after they take-off need to have some distance between them. So it would be better to have one aircraft going, say, north and the next going south.

A controller has many complicated decisions to make ^{(https://www.faa.gov/nextgen/snapshots/stories/?slide=20)}

Well, this starts to get a bit complicated for the people in the control tower, who have a number of decisions to make, such as – who takes-off first? Who has priority? When to pushback? When to start heading for the runway?, What happens when 20 aircraft are moving around the airport? Who gets priority when they meet at a crossroad? Should the arriving aircraft taxi first or the departing? One aircraft is late… do we wait? Who goes next? This aircraft was going south. Now two aircraft are taking-off and both are going north. Where do we fit the aircraft that was late? This is a situation that you don’t want to be thinking while you are heading to your vacation in Marbella and waiting to enjoy your piña colada.

Ok, we have established that handling a big airport is not easy. Well, that is why we have computers. Just put all the information to the computer wait for the solution and problem solved. This would be great but the problem is tricky even for a computer. Nonsense, nothing is even slightly hard for a fast computer, you may say.

Let’s say you have 5 aircraft and you want to find the best take-off sequence. You can have aircraft 1 taking-off first, then 2, 3, 4 and 5. Or you can have aircraft 1 taking-off first and then 3, 2, 4, 5 and so on. There are 120 combinations that you will need to consider, which is the factorial of the number of the aircraft you are considering (5! = 5*4*3*2*1 = 120). Do that for 10 aircraft and you have more than 3 million combinations. For 20 aircraft you have 2.4*10¹⁸ combinations!

Brute force search for the optimal solution takes forever! ^{(https://triunfob.wordpress.com/page/67/)}

Lets assume that a computer can find the result of one combination with just 10 simple operations. The fastest computer today (Tianhe-2) can do 3.386*10¹⁶ operations per second. Pretty impressive right? Well, processing all the combinations that can arise from just 26 aircraft (approximately 4*10²⁶ combinations) will take more than 3 millennia!

Now think that over just one day a PC will need to route 1200 flights. Each flight has numerous available paths to reach its destination and each aircraft can park at one of the 230 stands that are available (depending on their size). Furthermore, at every given time you can have more than 10 aircraft that need to take-off. You have arriving aircraft, departing aircraft, aircraft that go for maintenance, de-icing, changing gates etc.  This problem is impossible to solve with brute force. So that is why optimisation is so important.

Utilising optimisation methods can reduce the duration that is needed to find a solution while providing an optimal or near optimal solution. This means that it can find a very good (or even the best) solution to a problem within seconds. A good solution can increase the capacity of an airport and reduce the time that an aircraft has its engines on. Reducing the average taxi time for an aircraft by 2 minutes can save up to £15 million worth of fuel per year in an airport like Heathrow.

Even though it is a complicated optimisation problem, a lot of research is currently happening in this area. An optimisation model that was developed by The University of Nottingham has recently been applied to Heathrow airport’s take-off processes and proved to be very effective. Hopefully more research will lead to having a more precise and integrated model with accurate movements of aircraft that will allow ground movement models to be used for more reliable integrated decision making systems in airports.

More information about Air Traffic Optimisation can be found at.: Air Transportation Research webpage of ASAP research group.

The Institute for Aerospace Technology is currently welcoming applications for a range of PhD Fellowships. These Fellowships are funded by the Institute’s Marie Skłodowska-Curie Actions Initial Training Network, ‘INNOVATIVE’. For more information and to apply, please visit the University’s careers page.

The post Is air traffic optimisation really that important? appeared first on INNOVATE - Novel Aerospace Technologies.

A useful approach to integrating the work of the researcher within the industrial context is to divide the project time between the university and the company. Ideally, the PhD student should spend some time with the company at the start of the project to jointly define the objectives and develop a strategy to address the challenges involved. The period spent in academia would then be used to analyse the problem and build-up an extensive knowledge on what has been previously done in that field, taking full advantage of the knowledge available at the University.

In my personal experience, the main source of knowledge in academia are the professors and colleagues within my working group, who contribute to pass on knowledge that has been built up through years of research, not only through papers and theses, but more practically with day-by-day collaboration, discussion, and follow-up of specific problems.

After an extensive analysis of the problem within the academic environment, a period within the industrial team can be beneficial by enabling the application of the findings to an industrial context. Whilst integrating within the team of the company also adds more “practical” points of view to the project. For example, how long will it take to perform a given task? Or how far from the real world are the results obtained for an ideal test case? All of this gives us a feeling that what we are doing is going to be used to improve and develop real parts of an aircraft, providing a strong link with the reality of the problem we are addressing.

Such collaboration with a partner company is leading me to better structure the project I am working on, by requiring me to carefully plan the expected times to accomplish the given tasks and by evaluating the applicability of what I am doing. Often, we tend to excessively focus on the single problem while losing sight of the bigger picture, which may well overwhelm the single problem itself. The experience within the working group of my industrial partner led to a better balance between these two aspects, with constant reality-checks on what I am doing.

Moreover, the team provides additional insights and suggestions while benefitting from my academic findings, so that an exchange of knowledge in both directions is possible. After all, I feel like I became part of two different working teams, addressing the same challenges in a different context, and providing a link between them.

The integration of the researcher in both the academic and the industrial working group appears to be a fundamental piece of the puzzle of industrial collaboration with academia. Chris Firth, chief scientist of the UK branch of Thales (a French multinational focusing on aerospace and defence) recently stated that industries struggle to retain students after their PhD, due to the generally low amount of time, on the order of few months, spent in the companies’ teams during the project. In my view, a nearly-equal balance between the time spent in the university and the time in industry would be ideal to maximise the collaboration between the two parts, although this would depend on the “technology readiness” of the project itself.

The INNOVATE project proved to be a great choice in terms of industrial experience, as flexibility and support was provided by both The University on Nottingham and the partner company in organising the secondments. The interaction with both sides led to greatly expand the knowledge and impact of my project, from the basic underlying physical principles of my studies to the perspective of industrial application.

Andrea is currently doing his secondment at Rolls-Royce Deutschland. The Company is supporting his project on Heat Transfer and Thermal Management for the Aero-Engine Core.

The Institute for Aerospace Technology is currently welcoming applications for a range of PhD Fellowships. These Fellowships are funded by the Institute’s Marie Skłodowska-Curie Actions COFUND project, ‘INNOVATIVE’. For more information and to apply, please visit the University’s careers page.

The post Spending time in industry during the PhD appeared first on INNOVATE - Novel Aerospace Technologies.

Concerns over global climate change have prompted many countries to re-think about the concept of transport. Indeed, it is of primary importance to reduce impacts of transport on the environment. This is no different for the aerospace industry, which is particularly focused on the idea of greener aircraft, due to the level of fuel consumed by aircraft and the resultant emissions of carbon dioxide and other greenhouse gases (GHG) into the atmosphere. As a matter of fact, a ‘short-haul’ flight produces as much as three times the GHG emissions per passenger mile, compared to using a car.

Despite various attempts to realise a commercial hybrid aircraft, traditional gas turbine airplanes are still considered significantly reliable and cost-efficient.

Moreover, the optimisation of the aircraft aerodynamic performances is still regarded as being of paramount importance. It is here that flow control comes to the stage!

Indeed, original and innovative flow actuator methodologies are being developed. The target for the aerospace industry is to achieve the largest effect on the flow field – in terms of skin friction reduction and mitigation of flow separation – with the minimum amount of energy required. At the same time, the actuator transient should be small enough, in order to assure a fast real-time response.

As a matter of example, smart wind turbines have already benefited from Dielectric Barrier Discharge (DBD) plasma actuators. In fact, the primary effect of these devices is to virtually modify the aerodynamic shape of each blade, in order to increase the wind turbine capability of “capturing energy”, and to reduce the noise emissions, at the same time.

Another actuation philosophy is represented by synthetic jets (SJ), produced by a periodic cycle of ejection and suction of fluid through small orifices. Depending on the cycle frequency and amplitude, these devices can successfully introduce vortex motions of different size and phase in the flow field.

However, both DBD and SJ can only produce flow field perturbations which originate from the body wall – for instance the aircraft wing surface. Thus, they would take “some time” to reach the larger vortex structures, located outside the boundary layer. These motions, namely the hairpin eddies, are peculiar for their persistence in time and space. Moreover, as observed in many studies, the pattern of these structures tends to stretch itself within small pitch angles, down to the near-wall region of the boundary layer.

Direct numerical simulation of turbulent channel flow. Distribution hairpin vortices along the stream-wise direction (Zhou et. al 1999).

Hence, there must be a correlation with the wall skin friction distribution!

In effect, the main idea spreading among fluid dynamicists consists of controlling the wall skin friction – difficult so far because of the high-frequency velocity fluctuations – by simply disrupting the outer hairpin vortices – which evolve far more slowly.

Remote flow control is a key part of the solution. Before all else, the actuator has to be capable of:

• Not affecting the flow field between the wall and the hairpin vortex cores
• Being effectively faster than the flow field transients
• Perturbing the flow field locally in time and space, hence taking action only where and when needed

Currently, very few techniques are available. One of these is laser energy deposition. As mentioned on the previous blog post, this method is particularly effective within supersonic regimes. In fact, its primary effect is the formation of a system of shock waves which evolve in very small time and space scales, and which interfere with the shocks forming naturally around the body. As a result the heat flux distribution would be affected.

Hence, in order to adapt remote flow control to subsonic regimes, a medium to transport energy into the flow field is necessary. This sort of energy carrier, should also release its content locally and in small time scales.  How about explosive bubbles floating in air?

In fact, soap bubbles are the simplest and easiest way to transport chemical energy into the flow field, without significantly affecting it.

However, one more ingredient is still needed to definitely induce a micro explosion. Which agent could activate an exothermic reaction, without affecting the surrounding flow field? The answer is obviously coherent laser light. What is more, according to the laser wavelength and power used, several exothermic reactions can be targeted, including photosensitive, free-radical ones. However, a fundamental constraint to build such a flow actuator is its reliability. In other words, how easily can the reaction occur?

Several tests have been carried out at The University of Nottingham’s laboratories, on small bubbles filled with flammable gas and ignited by using green laser light – at 532nm. In this way, the gas contained inside the bubble is brought up to its flashpoint. However, due to the arduousness of focusing the laser light in a tiny spot – order of tenths of nanometres – hence depositing its energy, this process has revealed itself not very reliable.

Thus, a photosensitive, free-radical reaction could represent the best substitute, due to the very fast response after the first laser pulse, and its higher reliability – in terms of the occurrence of the reaction. In order to achieve this result, coherent light, within the UV range, should be contemplated. By the same token, the laser light should also be focused in a small spot, not really to deposit energy in air; it should rather localise the effect of the beam light to the region of interest.

UV laser light focusing on a small spot (newqyresearchgroup.tumblr.com).

In conclusion, remote flow control appears to be the state-of-the-art and the finest approach to control aerodynamic skin friction, by manipulating and eventually destroying the hairpin eddy cores – located near the outer region of boundary layers. In three words, a remote flow actuator should be:

• Fast
• Precise
• Reliable

The research which I have conducted as part of the INNOVATE project will help to better understand how to reduce the most considerable component of the aerodynamic drag force – the friction with air – which aircraft (likewise cars, trucks, etc) have to tackle every day. An improvement in the aircraft aerodynamic performances would reduce fuel consumption, and contribute to the reduction of aviation’s current levels of carbon emissions into the atmosphere.

In case the readers are interested about the answer to the question in the title of this article, please make sure not to miss the next blog on remote flow control, where further updates will be presented!

The post Explosive bubbles: Is it really the future of subsonic flow control? appeared first on INNOVATE - Novel Aerospace Technologies.

“It is good to have an end to journey toward; but it is the journey that matters, in the end”. Ernest Hemingway might have used it in a very different context but if you travel quite frequently on long/short haul flights, you begin to understand the significance of having a comfortable experience on-board…

I’m quite used to flying on long haul flights but my last journey from India was an eye-opener in many regard. For the first leg of my journey (Mumbai to Delhi), I was upgraded to Business Class, and I was treated to the hospitality and comfort that you would expect in an Executive Class in Boeing-777. The experience of the next leg of my journey (Delhi to Birmingham) proved to be a stark contrast to the first one. Although it was a Dreamliner, the horror of the entertainment system not working for a 9 hour flight, while seated in the middle seat of the middle column, greatly outweighed any positives; But as they say, bad luck makes good stories! So that inspired me to investigate some next-gen technologies that various aerospace companies are working on, which might shape our in-flight experience in future.

Windowless Fuselage (Source: CPI, U.K, 2016)

One such innovation which is tipped to hit the market within next 10 years is the windowless fuselage.  Imagine yourself seated in a plane cruising at an altitude of 39,000 ft. and instead of those boring white panels all around, you are treated to a view of the outside world, as you would see if the fuselage were transparent. This is what The Centre for Process Innovation (CPI) is looking to achieve through flexible OLEDs. The entire inner surface of the fuselage (or selected sections) can be covered with thin high definition, flexible displays screens made from these OLEDs, thus allowing the screens to either be used as displays or for lighting.

VR Helmets patented by Airbus (Source: Wired. 2014)

Airbus recently patented a design of Virtual Reality Helmets for its planes. As per the patent filing, the helmets offer the passengers sensorial isolation from external environment. If it’s really able to provide the sound, visual and/or olfactory isolation, as it claims, that would certainly redefine the whole flying experience! That said, it’s still in its preliminary stages of development and some experts claim that this is more of an Airbus’ strategy to protect its IP rather than bringing something very new to the market. Even if it does become a reality someday, if you still end up being the unlucky one whose helmet isn’t working, you might feel like you are trapped in a plane full of robots with no one to talk to!

Detachable cabin module patented by Airbus (Source: Wired, 2015)

Something which really caught my attention in recent times was an Airbus patent on detachable cabins. Essentially, the fuselage of the plane will have a void at its core where the whole “cabin module” could be slotted in. Thus the passengers won’t board the plane itself, but instead the passengers and luggage would be loaded in the cabin module while the aircraft might not even have been parked yet! This would not only significantly reduce the a passenger’s waiting time at the departure lounge, it would significantly reduce an aircraft’s immobilization time, thus making it an extremely interesting prospect in financial terms.

Another food for thought regarding this invention, which the patent doesn’t talk about, would be the possibility of incorporating an ejection mechanism for the cabin module in case of emergencies. It certainly would be extremely challenging to develop a mechanism to safely bring down the cabin module to ground, but it certainly could be a ground-breaking invention in terms of passenger safety!

It’s not all nice and rosy when it comes to next-gen technologies though. Some of the recent ideas and patents regarding seating configurations could give you nightmares about flying on an aircraft again!

Project HD31 by Zodiac (Source: Zodiac Aerospace, 2015)

Take for instance the HD31 Project from a French aerospace company called Zodiac. For every two passengers facing forwards, one is facing backwards. Now imagine this in a packed economy class environment and it won’t take you long to realize how excruciatingly annoying this can be!

If you thought a seating arrangement of 3-4-3 for a twin isle aircraft was a bit tight, Airbus recently came up with an idea of cramming up another seat in each row! Just imagine yourself seated in the middle of the 5-seat column for a long haul flight and having to pass in front of your neighbours to go the wash-room!

3-5-3 Seating arrangement (Source: Airbus, 2015))

It remains to be seen which of these prospects actually come into practice in future, but it’s pretty safe to assume that our whole in-flight experience would undergo some massive changes in next 2-3 decades. In the meantime, as they would say on an Air India flight, let us “sit back and enjoy”..

The post An insight into the future of in-flight experience: the good, the promising and the ugly appeared first on INNOVATE - Novel Aerospace Technologies.

The ambitious long-term environmental targets set by the European Commission (2011) and the Advisory Council for Aeronautics Research in Europe (ACARE) require airframers and their suppliers to improve the integration between an aircraft’s propulsion system and the airframe…

In particular, concepts such as the distribution of the thrust generation along an airframe’s main components and of ‘ingesting’ the fuselage boundary layer are considered to be of great importance in the industry’s attempts to fulfill ACARE requirements. However, for large aircraft the power densities are so large that they would require much higher power density subsystems than can be designed with current conventional technology.

The E-Thrust is an electrical distributed propulsion system concept for lower fuel consumption, fewer emissions and less noise (Source: Airbus Group, 2016)

The international research community has therefore suggested that the electric machines within an aircraft may need ‘superconducting’ motors. A hybrid system could be the best solution, with modified gas-turbine alternators providing electric power to a large number of superconducting propulsors.

Numerous researchers today have proposed superconducting machines connected by a network with superconducting cables that will still require conventional power conversion, switches and protection device. However, a distributed propulsion aircraft would significantly gain in performance implementing fully superconducting power systems (reduced heat losses and no transitions between environmental and cryogenic temperature).

Cryogenic systems

While the international research has so far been largely focused on the electrical aspects of the superconducting system, less consideration has been given to the cryogenic system to support the high power superconductors. In general a cryogenic system is formed by a cooling system (also called cryocooler) that operates below the boiling temperature of the liquid nitrogen (77 K), a coolant that could be gaseous or liquid and an insulation system that limits the heat losses.

To maintain a closed loop of cold fluid at the superconductors’ operating temperature, fully centralized large cryocoolers have been identified to be likely the best option for aerospace applications for their low weight and high efficiency. Reciprocating cryocoolers are likely to be unsuitable for applications with large cooling power required. Their performances rely on regenerative materials which are bulky and heavy. Moreover, the reciprocal operations require regular maintenance and the deterioration of regenerative materials needs periodical substitutions. Scalability and reliability are crucial factors for the main cryocooler and indications are that Reverse-Brayton Cycle (RBC) would be the best suited. The cryogenic temperature the cryocooler has to maintain is related to the transition temperature of the superconducting material employed in the system.

Reverse-Brayton Cryocooler (Source: Navy Metalworking Centre, 2015)

Superconducting materials

Since the discovery of superconductivity, great efforts have been devoted to the discovery of materials with higher and higher transition temperatures. Indeed, the consistent amount of energy required to cool down large device at the temperature of Kelvin would discourage any practical applications. At present, the superconductor with highest transition temperature is a ceramic material compounded of mercury, barium, calcium, copper and oxygen which present no resistance under 138 K. Unfortunately, this superconducting material cannot be employed for engineering applications since it is too brittle to be used to produce cables. The high temperature superconducting wires that have been commercially available since 1990 are made from a powder of bismuth-strontium-calcium-copper-oxide (BSCCO) which is deposited to form a film or a tape.

Most recently, second generation high temperature superconducting wires have been manufactured in a similar way using yttrium-barium-copper-oxide (YBCO). This material is superconductive at 92 K, but it presents electromagnetic properties suitable for electrical machines at lower temperatures (typically at the nitrogen boiling temperature or below).

Low temperature superconductors

Even though high temperature superconductors are a promising technology for future applications, low temperature superconductors are vastly adopted worldwide for their structural and electromagnetic properties. In particular, recent progress in a new superconducting material Magnesium Diboride (MgB2), allows the design of superconducting electrical machines that are much more power dense than convectional machine at environmental temperature. MgB2 presents no resistance at 39 K, but it shows interesting electromagnetic properties between 20 and 30 K. The application of MgB2 at 20 K is particularly interesting from the thermodynamic point of view since it allows for the use of liquid hydrogen as main coolant and therefore the possibility to take advantage of its great capability of absorbing heat while it evaporates. The combination of MgB2 superconducting cables and electrical machines, cooled down by liquid hydrogen may represent a viable technology for the power distribution system and the thrust generation system of future aircraft.

Design constraints

The design of a cryocooler for aerospace applications that is able to maintain a temperature of 20 K, removing considerable amount of heat, is really challenging. The question of how to dispose of the waste heat in the superconducting system and the associated cryocooling system will have a major impact on the overall aircraft design and its eventual performance. Simple calculations show that using ambient air, even at high altitudes, as the final heat sink will lead to challenging design constraints, in particular due to the low thermal efficiency that can be achieved. A low temperature heat sink is required when operating at temperatures below 60 K.

The main options that could be considered are liquid methane (LCH4) or liquid natural gas, and liquid hydrogen (LH2), due to their high latent heat, their boiling points and their heating values. Their usefulness as a fuel is of particular interest because they can offset the kerosene carried by the aircraft to mitigate the additional mass required by the cryogenic system. It is noted that LCH4 in particular has excellent combustive qualities and has higher chemical energy content by mass than kerosene. Modifications to gas turbine engines in order to burn methane would be relatively minor. Using hydrogen as a fuel may be more complex, since it would require larger modifications to the engine design. A more likely use of spent hydrogen coolant may be in an auxiliary power unit (APU) to provide additional electrical power.
The mass of the cryocooler can be generally expressed as a function of the input power required by the cooling cycle and since the weight is a crucial parameter to optimize in aerospace applications, the inefficiency of the superconducting electrical machines would severely restrict the scope for a feasible system solution. The target efficiency to make superconducting distributed propulsion a viable solution for ACARE requirements is 99.7%.

Note about the author:
The author further investigated cryogenic and superconducting technologies during his secondment with Airbus Group Innovation as part of the Institute for Aerospace Technology’s INNOVATE project, as an opportunity to improve his professional skills in an industrial environment.

The post Cryogenic applications for visionary aircraft concepts appeared first on INNOVATE - Novel Aerospace Technologies.

With very few exceptions, going to the office is mostly a dull experience acceleration wise. That is until one day when instead of taking the usual bus to work you get on a plane to Aberdeen, and instead of sitting on the usual three-degrees-of-freedom office chair you find yourself in a six-degrees-of-freedom full Airbus Helicopters H225 flight simulator (Figure 1, Figure 2).

Figure 1 Outside view of the helicopter simulator

On the otherwise usual days, as part of my PhD, I study people’s physiological reaction to various levels of mental demand and the impact on their performance, with the aviation industry being the main application of my research. However my industrial sponsor, Airbus, offered me the unique opportunity of joining them on an important study. The main aim of the study was to learn more about deploying the physiological monitoring techniques for pilots, that Airbus and I are using as part of our research, to an environment as similar as possible to the real one.

We spent one week at Airbus Helicopters in Aberdeen, each day performing measurements and observations on training pilots; the physiological monitoring consisted of collecting data on heart rate, breathing rate, pupil diameter variation and facial thermography (Figure 3). Setting up some of the devices, especially the thermal camera, presented both challenges and valuable lessons for the future.

Figure 2 Helicopter simulator cockpit

The most exciting part of the study was joining the pilots on the jump seat and going through their training, experiencing the most unlikely failures that could occur during flight, all of them in different combinations: engine failure, double engine failure, engine fire, tail rotor cable failure, gearbox failure, autopilot failure and all instrumentation failure at night and in low visibility. Most of the scenarios, after going through the diagnosis stage and discussing the best practices for dealing with the event, ended up with performing autorotations (maneuver for landing a helicopter without the use of engine power, relying only on the flow of air through the blades) and sometimes ditching the helicopter in the sea, both options being bumpy to say the least.

Figure 3 Thermal image sample with tracked features

One of the most impressive things that I had the opportunity of observing is the crucial role of communication between the pilots and the need to achieve a high level of trust as some very demanding situations require the sharing of responsibility and fully relying on the other person. Communication is sometimes mediated through procedures and best practices, whilst as for trust it probably requires some more work.

Even though I do not usually fly on helicopters, it was extremely comforting to see the thorough training that the pilots go through and the ability they have to take split second decisions and perform seemingly impossible landings.

After one week of taking part in simulated flights, I was back to my usual office, missing the excitement of emergency situations but happy to be on stable ground.

The post A human factors study on helicopter pilot performance appeared first on INNOVATE - Novel Aerospace Technologies.

INNOVATE is a University of Nottingham European-funded doctoral training program that offers a researcher the opportunity to study for a PhD as well as spending a minimum period of six months in a company. Here INNOVATE Early Stage Researcher (ESR), Sara Roggia, talks about her role as part of the INNOVATE project and her secondment at Avio Aero in Italy.

Working within industry is an invaluable opportunity for PhD student. It’s a common idea to consider the research world as distant from the business reality. More often PhD students are focused on their own research work without considering the feasibility and the potential real-world impact of their ideas. Questions they should ask themselves include “is my idea feasible?”, “is it affordable?”, “how long would it take to be realised?” and are inquires a PhD student will never answer if they do not develop a commercial understanding of research. Industry, on the other hand, doesn’t always know what research is being invested in and which scientific direction has been chosen by the academic world. The conceivable mistake is they will keep on walking two parallel routes.

In Italy, the company Avio Aero is trying to converge the two paths. In Southern Italy, in Bari to be precise, an official collaboration was agreed between Avio Aero and Politecnico di Bari, a Technical University located in the same city. A bilateral accord was signed in 2010, in which Avio Aero gave guaranty of investing its own resources until 2020, mainly in five research areas, employing several university’s researches and PhD students for each area.

Taking advantage of the local presence of such a noteworthy university (Politecnico di Bari – First Italian University in research in the 2012 and 2013 SIR World Report (Scimago)), Avio Aero decided to develop a multidisciplinary lab, in which activities will be led by five researchers of Politecnico di Bari, with suggestions and directions provided by nine Avio Aero leading researchers. This centre is known under the acronym of EFB (Energy Factory Bari).

Avio Aero is a company that works in the field of aviation. Previously named simply as Avio, it was born in 1908, funded by FIAT group. Recently (2013), it became part of GE (General Electric) and it was re-baptised under the name of Avio Aero, because of its specific applications in aeronautics.

Namely, Avio Aero is a GE Aviation business, working on the design, production and maintenance of components and systems for the civil and military aeronautics industry. Nowadays, 80% of commercial aircrafts utilise Avio Aero components. Its head office is in Turin, Italy, and its production plants are spread worldwide: Netherlands, USA, Brazil, China, Poland, Italy.

One of the Italian headquarters is in Bari. Here, the proximity of Avio Aero employees to the students and researchers, inside EFB labs, enlarge the possibility of exploring additional scientific subjects.

The aforementioned five sectors under investigation are:

• High speed electrical machines;
• High Frequency Power Converters;
• Control Systems;
• Thermal fluid dynamics of machines and energy systems;
• Mechanical machine design.

The main aim is to develop new technologies and architectures for reducing aircraft weight, thereby improving aircraft performance and moving towards more electric aircraft.

The same collaborative spirit drives the INNOVATE Project, led by Professor Hervé Morvan and the Institute for Aerospace Technology (IAT), as a multidisciplinary project in which PhD students are expected to bring different expertise to the field of aerospace field in order to enhance the state of the art and find “more electric” solutions to air travel.

Both of them, Avio Aero and the IAT, understand the importance of having people from different backgrounds working at the same time in the same environment, creating connections and enabling a transverse flow of information between mechanical, electrical, and aerospace engineers.

Furthermore, they equally appreciate the importance of collaboration between research and industry. Avio Aero built a dedicated conjoined lab in Bari whereas the IAT invited companies to be part of the INNOVATE project.

Several companies, during the development of the INNOVATE program, were chosen in order to collaborate with each of the INNOVATE Early Stage Researches (ESR). Avio Aero was selected as industrial partner for me, ESR9 (Sara Roggia), working on ground operation electrical systems, i.e. electric motors for Green Taxiing (GT) application.

When he first met the INNOVATE Team, Professor Francesco Cupertino (Deputy Director of department of Electrical and Electronic Engineering of Politecnico di Bari and Avio Aero INNOVATE delegate), he could immediately see the industry-focus of the INNOVATE Project. He took part at the INNOVATE Launch event where our first team project – the development of two unmanned UAVs – was showcased.

Prof. Cupertino (Avio Aero representative) and other industrial partners attending INNOVATE Launch Event.

MALET: a) electrical motor coupled with compressor; b) 3D model of the motor

A similar project is now ongoing in Avio Aero labs. Named MALET, this activity regards the development of hybrid propulsion system for UAV’s application. Specifically, an aeronautic propulsion system, in which turbines and compressor are electrically actuated, will be designed and built.

I am now spending my secondment in Avio Aero – Bari, working on the experimental part of GT Project.

Avio Aero gave me the possibility of establishing a test rig in order to develop the control of a conical actuator (based on principle of sliding rotor) that will be utilized for GT application.

EFB Labs: several test-rigs designed for standard motor testing and experiments on high-speed machine for propulsive applications.

At the same time, due to the great interest of Avio Aero in high speed electrical machines, I have been involved in several on-going studies regarding this topology of motors. The aerospace industry is investing a lot of resources in this kind of motors, because of the advantages they could offer. The possibility to remove mechanical gear, meaning less noise, and the chance to have a smaller motor size for a given power are just two such advantages.

Avio Aero and Politecnico di Bari are distinguished in terms of the investigation and publication about this topic. Together with “Politecnico di Torino” (a worldwide recognized university in the field electrical machines, strongly connected with both “Politecnico di Bari” and The University of Nottingham), they developed a design tool for High Speed Synchronous Reluctance machines (SyRe), thereby contributing to the development of state-of-the-art aerospace technologies.

Having looked at the above mentioned initiatives, it is easy to see that there are impressive quantities of industrial projects in which PhD students can easily fit, contributing to the development of the actual technologies whilst improving their capability for doing research. Fortunately, things are evolving in this sense thanks to such kinds of collaborations, in which both Avio Aero and the IAT strongly believe.

Photo Credit: Chiara Stomati

The post INNOVATE and AVIO AERO: Bringing Industry and Academia Together appeared first on INNOVATE - Novel Aerospace Technologies.

The well-established success of the Rapid Prototyping technologies derives from the possibility of creating parts with almost any shape at no added costs. However, in order for a part to be functional (i.e., with good mechanical properties), high density and tailored material properties are desired. In the past few years, Additive Manufacturing (AM) technologies such as Selective Laser Melting (SLM, shown in Fig. 1) have been proving more valuable than Rapid Prototyping in that they can achieve densities comparable to those obtained through classical subtractive and formative processes. Thus, AM is showing great potential for moving from Rapid Prototyping to Rapid Manufacturing. For this reason, SLM is emerging across a broad range of sectors, including automotive, medical and aerospace, for the creation of functional parts. It is of public domain that one of the most prominent aerospace names regularly associated with AM is GE Aviation, which already in 2013 was leading the way with its plans to produce a fuel nozzle using SLM. A little more than two years have gone by, and GE best-selling engine of all times (the LEAP engine) is set to enter into production by end 2015. Indeed, it will feature the 3D-Printed fuel nozzles that have been making the headlines in 2013.

Fig.1: The SLM process starts with the wiper distributing a layer of powder from the supply chamber onto the build platform. A high-power laser beam is then applied selectively on the powder surface, according to the .stl file of the part. The energy fully melts the powders together before the build platform descends by one layer thickness along the z-axis. The process is repeated until completion of the final part

Despite the use of AM and SLM in a range of metallic materials, including Stainless and Carbon Steels, and a few Titanium, Cobalt and Aluminum alloys, the potential of this manufacturing technology for functionalities other thanpurely structural seems pretty much unexplored. A significant example in this regard is represented by those materials with ferromagnetic properties, such assoft and permanent magnets. Applications that rely upon such materials include the large family of devices that transform electrical energy into mechanical energy, such as loudspeakers and motors, and from mechanical to electrical, such as microphones and AC generators.

Until now the design of standard magnetic devices has not gone much beyond the two-dimensions, especially due to constraints imposed by the (mainly subtractive and formative) manufacturing processes employed. Arguably, this imposes limitations in terms of the performance, let this be of acoustic or electromechanical nature, or in terms of the weight.  A very interesting example is that of electrical motors, whose application to the transportation industry is seen as the most promising alternative to fossil fuel engines and mechanical actuators to cut the emissions of green-house gases and thus limit the impact on the environment.  The possibility offered by AM to extend the design of components to three-dimensional space without the constraints of traditional manufacturing introduces new opportunities towards the production of highly power-dense electrical machines, where the core magnetic material is added only where it is actually needed. The impact of such innovative devices would be highly beneficialespecially for transport applications, where weight is the primary determinant of vehicle efficiency.

Modern Permanent Magnet machines for transport applications rely upon two types of ferromagnetic materials for energy conversion: soft magnets and hard – or permanent –  magnets. The alloys belonging to the former type have the property of magnetising when immersed in a magnetic field, and lose their magnetisation upon field removal. Hence, soft magnets are used to ”amplify” and guide the magnetic field through space. Both the stator and the rotor cores of electrical machines are soft magnetic. Among the most popular soft magnetic materials, we find Silicon Steel, Cobalt Steel, the Nickel-Iron family of alloys (a.k.a., Permalloys), and a class of soft magnetic ceramics (soft Ferrites). On the other hand, permanent magnets retain their magnetisation in the absence of a magnetic field, therefore effectively producing their own magnetic field. Materials with permanent magnetic properties are a class of Iron ceramics (hard Ferrites) and, most importantly, the family of alloys based on the rare-earth minerals Samarium and Neodymium. The latter are a major concern for western producers across a broad range of hi-tech industries, due to their limited availability outside of China, which effectively controls the worldwide distribution by producing over 90% of global rare-earth minerals needs. Being able to minimise the need for rare-earth material by optimising the shape of the magnets, by exploring substitutes (e.g., hard Ferrites), or even through recycle and reuse of old magnets are all very attractive options, which a technology like AM could enable.

The idea of processing electrical machines using laser-based additive technologies has been around for at least one year now , when an article appeared on the blog of the CAFE Foundation (link here) presented the $2.7 million project ”Additive Manufacturing of Optimized Ultra-High Efficiency Electric Machines”, which the Connecticut-based United Technologies Research Centre will be launching in early 2016. However, the project targets the direct manufacturing of copper and insulation, layer-by-layer, as opposed to the traditional wire winding technique. By optimising the placement of the electrically conducting material, the team hopes to be able to minimise the quantity of core magnetic material within the device.

But what about the possibility of printing the magnetic material itself into soft and permanent magnets?

On the permanent magnet front, the Critical Materials Institute (CMI) in Ames, Iowa, has been established by the US Advanced Manufacturing Office with the purpose of overcoming the shortage of critical materials (link here). As part of this mission, the CMI is addressing the opportunity offered by AM to process high-performance permanent magnets without needing estensive use of rare-earths.

Fig.2: An ABB Synchronous Reluctance motor. Modified from http://quintecgmbh.com/us/news/161-news-abb-synchronour-reluctance-motor.html

As regards to the soft magnetic materials, the potential for improvement through AM seems pretty much unexplored, as testifies the complete absence of coverage in the media. As part of the EC-funded, €3.8 million programme INNOVATE (more info about the programme here), the IAT and the Additive Manufacturing and 3D-Printing Research Group at the University of Nottingham are working on a project aimed at investigating the very potential of soft magnetic material development through SLM for rotating electrical machinery applications. At the More Electric Aircraft Conference in Toulouse earlier this year (manuscript can be found here), we presented the idea that the Synchronous Reluctance rotor (Figure 2) could be the good candidate for processing using SLM. The rotor of this machine is characterised by a very simple structure, composed entirely of soft magnetic material. Neither conducting material (e.g., the copper/aluminium bars used in Squirrel Cage Induction Machines) nor permanent magnets are involved. Therefore, the performance of the Syncronous Reluctance Motor mainly relies on rotor core geometry and the capability of the material to conduct magnetic flux.   Furthermore, as the Synchronous Reluctance Motor operates at synchronous speeds, the rotor flux variation is minimal and its fabrication as a solid structure can be envisaged without incurring in detrimental eddy current losses. The employment of AM/SLM, alongside advanced design tools like Topology Optimisation, may enable the creation of innovative three-dimensional designs for reluctance rotor structures that are free from the constraints of classical manufacturing. Improvements might include the conception of continously skewed rotors and unconventional saliencies/flux barrier designs.

But the advantages of SLM are not restricted to geometrical considerations. As an example, soft magnetic Silicon Iron alloys represent excellent candidates for processing using SLM. In particular, SLM might foster the employment of 6.5%Si steels, which are known for their good magnetic properties such as high permeability, low hysteresis losses, high electrical resistivity, and low magnetostriction. The commercial application of these alloys has been limited due to their poor ductility, which makes their processing difficult. Owing to the powder-based, layer manufacturing approach of SLM, the employment of 6.5%Si steels for machine cores can now be envisaged indeed.

Given all of these premises, and seen the success that laser- and electron-based AM technologies have recently deserved for structural applications, it is safe to claim we won’t have to wait too long before witnessing the world of electromagnetics benefiting from the ground-breaking manufacturing technology of the digital era.

The post Can we “3D-Print” an Electric Motor? appeared first on INNOVATE - Novel Aerospace Technologies.

Since the beginning of time humans have dreamed of possessing great magical powers. The power of casting fire, strong winds and many other traits which are supposedly possessed by divinities, heroes and magicians of the saintly days of yore.  One of them is the art of making objects float in the air.

In the Necronomicon of the electrical engineer there are three ways to make objects float. The first one consist of the use electrostatic, which deals with slow-moving electrical charges. Like your hair being attracted to a balloon that you a rubbed on your woolen pullover (I hope everybody knows that magic trick … If not, you have had a sad childhood). The twain others belong to the nebulous realms of magnetism.  One is only narrated in the Kabbalah and the Faustus legends of physics: the usage of superconductors to achieve diamagnetic levitation and flux trapping (more info about superconductors: here. A cool video of levitation with superconductor: here). But to be honest with you, I don’t dare myself to wander into this domain for this short introduction of Levitation spells.

At last one that I wish to highlight here is magnetic levitation. Even here there are two major schools: by using diamagnetic properties of an object with a very strong magnetic field you could levitate many kinds of objects, like a frog (how crazy is that!) but high are the efforts needed to make this exercise a success. Don’t believe me, watch it by yourself: here

The other one uses electromagnets. The levitation is made with quite some ease but the catch is that the material has to posses  ferromagnetic properties (darn, but nothing is perfect!).   The easy way to check if something is ferromagnetic is to bring a magnet close to it, and if it sticks (without glue obviously) it is ferromagnetic. The levitation is based on this attraction of magnets and Iron. But most of you will have realized that this doesn’t really work for making objects levitate. Therefore from my spell book of electrical engineering I will teach you a new spell “electromagnets”.  The magic is that you can create a magnet using a coil of wires by supplying it with a current. The great part is you can change the strength of the attraction between the electromagnet and the Iron by changing the current.

I will now clearly show how the levitation works, with the help of an old electrical wizard (Teguas Lass):

Teguas Lass holds on his electrical staff a coil, with his ancient power he can change the current in the coil. He is able to maintain the ball floating in the air by changing the current in the coil. Teguas Lass observes the ball. When the ball is getting close to the coil he will reduce the power in his staff however if the ball starts to fall he will increase the power of his staff. This way the ball can float in the air.

Sadly our current world has lost the ways of ancient magic. But this doesn’t mean that it makes the actions of the wise Teguas Lass impossible to us.  In our now magic less world, some solutions were found to replace the old powers. Instead of using a power staff, we are using a power supply, that will feed current to the coil in order to generate the force. We could try to regulate that force manually with someone changing the power supply as the ball is getting closer or further from the coil. That would be very containing and might not always work. Therefore we use  a controller (some sort of computer) that with the help of a position sensor, will automatically change the current from the power supply to maintain the Iron ball in a certain position.

Levitating a Iron ball is obviously fantastic, but there is not to much use in this. The main advantage of the levitation is that an object can be maintained in a position without any need for a contact. , therefore if they are moving they subject to much less friction in their motion. Which means that we can make objects move faster. As crazy that it might sound some trains are magnetically levitated ( they are called maglev trains). Like the record breaking Japanese Lo series that reached 603 km/h on the 21^st April 2015 (more info here ). For rotating shafts magnetic bearings  and bearingless machine where developed. They maintain the shaft in a certain position while still allowing it to rotate freely. Which leads to possibility of higher rotational speed and a much long durability. The absence of friction reduces the wear of the machinery  and the lubrication is no longer needed. I would recommend you to visit the website http://www.magneticbearings.org/ that will give you a lot of insight on the magnetic levitation and it’s uses. (For even more information here and here) In  aerospace we dream of a turbo engine without any oil, and magnetic levitation could be one solution to this. One other great features of magnetic bearings is that since you can control quite precisely the position of the shaft. You can therefore reduce vibration and reduce unwanted rotodynamic effects.

I personally work on bearingless machine: Those are electrical machine that rotate a shaft while magnetically levitating it. It’s like a two in one device. The aim off my work is to use this type of machine to reduce vibration and try to avoid some rotodynamic challenges. At the end look at how this could be integrated to an aero-engine.

The post Levitation spell (magnetic levitation technology) appeared first on INNOVATE - Novel Aerospace Technologies.