Going green with dry ice

CO2 dry ice pellets just a few millimeters in size remove dirt in engines

The new process is called Cyclean dry ice. A mobile cleaning system is backed up to the engine – no matter where the aircraft is standing – and sprays pellets of CO2 dry ice a few millimeters in size at high pressure into the turbine. On impact, the -78,5 (-109.3 °F) cold pellets release kinetic energy, removing impurities.

Faster cleaning, less resource consumption

The new cleaning process has enormous advantages. Since the cleaning system does not have to be attached to the engine as in previous processes, the cleaning time is halved to just 30 minutes. The consumption of resources is also reduced, as water no longer has to be used. The CO2 applied is a byproduct of the fertilizer industry and does not have to be generated for this purpose. And the pellets vaporize after cleaning, so there are no residues.

The process is a further development of the Cyclean® cleaning process, which Lufthansa Technik has been using worldwide since 2007. Since it works with water, however, it cannot be used at temperatures below 5 °C (41 °F). There would then be a risk of cleaning water accumulating and freezing in the core engine. Cyclean dry ice, on the other hand, can be used at sub-zero temperatures. This means that engines can be cleaned anywhere in the world 365 days a year – even in permafrost regions.

The effect on the environment is also enormous: a clean engine saves up to 80 tons of CO2 emissions per year. In total, clean engines reduce CO2 emissions in civil aviation by several hundred thousand tons per year.

Lufthansa Technik developed the new process together with Darmstadt University of Applied Sciences. The development tests are currently in the final phase, and several patents have been filed. The new process is expected to be applied in addition to the water-based Cyclean engine washing from 2020 – and will make a significant contribution to "green MRO" in aviation.


Fueling sun

Solar installation for the solar production of kerosene

The advantages of fuel from renewable energies are enormous. For example, solar kerosene reduces CO2 emissions by more than 90% compared to fossil fuel, as the plant pulls the raw material CO2 from the atmosphere. In contrast to biofuel, there is no competition with food production during the process.

A process unique in the world

For the project, the seven partners have installed a unique solar plant in Móstoles, Spain. A heliostat field consisting of almost 170 focusing mirrors collects the sunlight and concentrates it 2,500 times. This produces temperatures of over 1,500 °C (2,732 °F), which are required for the subsequent process. The basic idea is to reverse the combustion process. The process uses carbon dioxide and water as raw materials, draws energy from sunlight and thus produces fuel.

In detail, the corresponding thermochemical process consists of two steps. First, oxygen is released in a specially developed reactor made from a metal oxide, which serves as a reactant, at around 1,500 °C (2,732 °F). The researchers then pass carbon dioxide and water vapor through the reactor at around 700 °C (1,292 °F). Both react with the oxygen-deficient metal oxide and release oxygen. The result is a synthesis gas – a mixture of hydrogen and carbon monoxide, each with a very high degree of purity.

The synthesis gas is then converted into kerosene using the Fischer–Tropsch process. The use of Fischer–Tropsch kerosene is already permitted today, allowing the solar fuel to be blended with conventional turbo-combustion engine fuels without any further approval procedures.

Solar kerosene is possible

The project partners in the predecessing SOLAR-JET project showed that the process works – but only under laboratory conditions. In June, for the very first time, solar kerosene was produced under real conditions in a pilot project.

The SUN-to-LIQUID project brings together leading European research institutions and companies in the field of thermochemical solar research: ETH Zurich, IMDEA Energy, DLR, Abengoa Energía and HyGear Technology & Services B.V. The coordinator Bauhaus Luftfahrt e.V. is responsible for the technology and systems analysis. ARTTIC supports the research consortium in terms of project management and communication.

SUN-to-LIQUID is funded under Horizon 2020 and will be continued until December 2019. Until then, the plant will be subjected to a continuous load during production operation and will provide valuable insights for future reactor and plant developments during research operation. These will be incorporated into future projects in order to achieve the goal of commercial production of solar kerosene.

Pocked-sized space

The conditions inside are controlled and results are evaluated via software.

From the outside, the facilities look like large steel pipes, several meters high and long. At the front they are locked with a thick door. The massive exterior, however, conceals the high-tech interior of the system.

The universe in miniature

Inside the tube is a small version of the universe. Scenarios with different extreme temperatures and pressures can be simulated and controlled in detail via software. Individual components, subsystems and entire satellites are exposed to these conditions in the cylindrical chamber – sometimes in 2,000-hour tests for almost two months. This involves testing whether the material can withstand the conditions or whether the technical systems are overheating.

ATT Umweltsimulationen is constantly developing new and improved test systems to test new types of satellites of all sizes. In addition to standard systems, individual designs are also possible. Their customers are the world's major space agencies. One of the world's largest simulators is located at the European Space Research and Technology Centre (ESTEC) of the European Space Agency.

From the outside, the facilities look like large steel pipes, several meters high and long. At the front they are locked with a thick door. The massive exterior, however, conceals the high-tech interior of the system. The universe in miniature Inside the tube is a small version of the universe. Scenarios with different extreme temperatures and pressures can be simulated and controlled in detail via software. Individual components, subsystems and entire satellites are exposed to these conditions in the cylindrical chamber – sometimes in 2,000-hour tests for almost two months. This involves testing whether the material can withstand the conditions or whether the technical systems are overheating. ATT Umweltsimulationen is constantly developing new and improved test systems to test new types of satellites of all sizes. In addition to standard systems, individual designs are also possible. Their customers are the world's major space agencies. One of the world's largest simulators is located at the European Space Research and Technology Centre (ESTEC) of the European Space Agency. ATT Umweltsimulationen is currently creating a novel simulator for the National Satellite Test Facility of the Science and Technology Facilities Council in Great Britain. A new building will be erected for this purpose, which will be completed in spring 2020. With a diameter of seven meters and a length of 12 meters, the test facility is the largest to date in the United Kingdom and one of the largest in Europe.

Explosion force against wear

The LSP system at the ZAL TechCenter – one of only three machines worldwide.

The new technique is called laser shock peening, LSP for short. In the process, a metal component is coated with a lightproof film which is covered with a fine film of water. The area to be treated is then subjected to a high-energy laser. The resulting plasma literally explodes on the surface of the component, and the explosion wave causes deformation in the material – unfailingly contained by the water layer. One can imagine it like a New Year's Eve firecracker over which a blanket is put before it is ignited, limiting the explosion. These locally introduced small deformations generate inherent compressive stresses in the material, which have a positive effect on the fatigue properties of the component.

High precision

The process is suitable for making surfaces more resistant to fatigue after having passed through production processes. One example is the engine blades, which often wear out at the joint: due to the high permanent load, tiny cracks develop there over time. If the surface is treated with LSP, the signs of wear are delayed or completely avoided.

LSP has considerable advantages over the process previously used, known as shot peening: Despite the martial-looking energy discharge, it is much more precise. It also scores in terms of environmental friendliness, as it mainly uses light and water. Compared to shot peening, LSP treatment can achieve up to 20 times the penetration depth.

One of only three plants worldwide at ZAL

Until now, there have only been two machines worldwide for the LSP process from LSP Technologies, neither of them in Europe. With the installation of a third machine at the ZAL TechCenter, LSP can now for the first time also be used extensively in the research environment in Europe. With a total of 2.6 million euros, it is the largest single investment in the history of ZAL to date. The machine is available to aircraft manufacturers for the treatment of ready-to-use components. It is also used as a test infrastructure for research purposes.

The process is a prime example of successful spill-over effects from military aviation. LSP has been used in the US military sector since the 1990s. For some years now, civil aviation has also been benefiting from the advantages, and now it has come to Europe. With the new facility, ZAL and thus German aeronautical research will rise to become part of the leading international group in this field.


From droplet to new engine design

Project manager Florian Meyer shows the experimental setup.

The process seems basically simple: liquid oxygen is injected into the combustion chamber of the rocket engine and burns there with the hydrogen present. The injected oxygen must be divided into as many tiny droplets as possible – in the end it is more like a spray – in order to obtain the largest possible surface area. This makes combustion faster and more efficient.

The exact way the chemical and physical processes interact is not yet known. The complexity is high: several million tiny droplets react with each other within a few seconds and at high speed. How do the individual droplets evaporate? Which pressures occur when and where? What are the interactions between the individual droplets? Even the most powerful computer today does not have the capacity to calculate this in this dimension.

Basic research for tomorrow's spaceflight

The HYDRA research project at ZARM investigates these processes using the simplest element: a single drop. In the 146-meter-high Bremen drop tower, the scientists generate a drop of oxygen and drop it down in a combustion chamber for five seconds. There it reacts with gaseous hydrogen, which is located in the combustion chamber. The reaction is ignited with a laser. Using special cameras and sensors, the scientists record exactly what is happening.

The 146-meter-high drop tower at ZARM – unique in Europe.

During the free fall in the tower, the experiment is in weightlessness, which among other things leads to the drop not having the usual elongated shape but being perfectly round. This makes calculations easier in this first step. In the course of the experiments, different concentrations of hydrogen as a fuel and different pressures will also be experimented with.

By observing the individual drops, the researchers hope to gain insights into the overall system. The next step could be to add a second drop to see how the two drops interact during combustion. The long-term vision: to one day understand and optimize the entire process.

Getting the most out of the rocket engine

The researchers want to gain insights into how the combustion process in rocket engines can be made more efficient. As a result, the combustion chambers, for example, could one day be made smaller. The consequence: the rocket as a whole can be made smaller, lighter and produced more cheaply. In view of new developments and increasing commercialization in space travel – keyword: New Space – that could be a decisive advantage and give European space travel an important edge.

ZARM is collaborating on the project with several partners, including the Leibniz Institute of Photonic Technology at the University of Jena and the University of Washington in the USA. The project is also financially supported by the German Aerospace Center (DLR). It runs until the end of 2019.


Three in one – for leaner production

OSFIT rib demonstrator in front of production line

For decades, the European and American aviation industries have dominated worldwide aircraft construction. Stars like the Airbus A320 or the Boeing 777 characterize modern air traffic. However, new competitors are now entering the market. China’s Comac and Russia’s Irkut want to deliver their own aircraft with more than 150 seats by 2021 at the latest. The German aviation industry accepts the challenge. See Premium AEROTEC: the component manufacturer is working at a great pace to be able to produce the components of the future more efficiently and cost-effectively – and thus keep well out in front of the competition.

New process with significant advantages

One example is the so-called ribs. They form the skeleton of an airplane, so to speak. Like the bones in the human body, they ensure that the aircraft remains stable – regardless of the stresses it is exposed to during takeoff, landing or flight. In an Airbus A350, for example, around 100 ribs extend from the cockpit to the end of the aircraft, spanning a fuselage over 70 meters long. The ribs run all around the body of the plane, similar to ribs in a human body.

Today, the ribs are attached to the aircraft skin with a kind of L-angle, the clip. Currently these clips are made of special carbon-fiber-reinforced plastics (CFRP). CFRP is lighter than metal and this special thermoplastic variant can also be processed quickly and cost-effectively. So far, each clip is fastened individually to the ribs by rivets. In Bremen, Premium AEROTEC has now developed a new process for manufacturing ribs from this material as well. Thus, it is possible to integrate the clips directly into rib production. Several components become one, assembly times are reduced and the process is made more efficient.

Costs are halved

In the long term, Premium AEROTEC wants to integrate yet another element into the ribs, the so-called Stabilo. This supports the ribs in the direction of flight, prevents tilting and ensures that the structure of the aircraft remains stable, even when exposed to extreme forces – such as during takeoff or landing. So far, the Stabilo has also been made of thermoplastic CFRP and attached separately to the ribs. By combining the three elements – rib, clip and Stabilo – into one component, the new process halves the manufacturing and assembly costs compared to today's construction method.

The first airworthy components will be available in around two years. The new three-in-one component will be tested on the A350, but the process might be applied to the integral ribs of all aircraft models.

The company has been developing the process since 2018 along with four partners, including two Fraunhofer Institutes. Premium AEROTEC's Hamburg location is also involved alongside Bremen. Through cooperation and networking with its partners, the company is expanding its own know-how in the field of fiber composites, thus consolidating Germany's pioneering role in the aviation industry.

Research location moon – for a better life on Earth

Design of the first operational habitat on the moon

Not an easy undertaking

The technical demands in this hostile environment are enormous: the station on the moon must be able to withstand the ultra-high vacuum and temperature fluctuations from -160 °C to +130 °C (-256 °F to +266 °F). It must protect its inhabitants from the dangerous cosmic rays and at the same time enable a self-sufficient life-support and energy supply – for several months or even years. What's more, in order for astronauts to be able to live and work on the station for a long time, it must also offer a space worth living in. Otherwise, there is an increased risk that people there will develop psychological problems.

Research in a new dimension

There are currently about a dozen test stations around the world primarily used to examine the mental state of residents in extremely cramped rooms and to test organizational processes. However, they are not suitable for use outside the Earth. The researcher from Bremen wants to build a station in the MaMBA (Moon and Mars Base Analog) project over the next few years that will make it possible to spend several months on the moon. The focus of the project is on technological implementation, in particular on the interaction of the individual subsystems. The scientific module of the station is currently being developed; among other things, it will enable geological and material scientific investigations to be carried out directly on site. For example, samples of the moon rock will be examined in the laboratory in order to better understand the history of the formation of our satellite.

The lab will be part of an underground habitat on the moon. In total, it consists of five to six connected modules, supplemented by two airlocks through which inhabitants can get outside. Each module serves its own purpose; for example, there is a sleep module and a laboratory module. The modules are cylindrical with rounded corner pieces, measure five meters in diameter and are about six to seven meters high. While the working modules have two stories, leisure modules only have a single story, but with high ceilings. Up to six people will be able to work and live in the habitat.

Insights for life on Earth

The project will provide important insights for life on Earth. For a station on the moon worth living in, similar challenges have to be overcome as on Earth, such as limited resources and self-sufficient energy supply and storage. But under tougher conditions – which in turn will inspire new solutions on Earth.

By mid-2019, the first MaMBA module will be set up as a test version, but technically it will not yet be "moon-ready." Rather, a simulation with a crew is to investigate whether the architecture, the design and the arrangement of the laboratory workstations meet the requirements of the real processes of everyday research. The design of the airlock and the self-sufficient life-support system will be important further expansion steps in the years to come.

Christiane Heinicke heads the MaMBA project at ZARM


Extreme insulation for Ariane 6

Ariane 6

It takes 180 tons of fuel to launch an Ariane 6 rocket into space. The cryogenic fuel consists of high-energy liquid oxygen and liquid hydrogen. These substances maintain their aggregate state only at very low temperatures – minus 200 °C (-328 °F) and minus 253 °C (-423 °F) respectively. The challenge is to keep these temperatures constant during the rocket's ascent and mission – otherwise they become gas again and endanger the expedition. It is very difficult to maintain these very low temperatures inside the rocket because during flight in the Earth's atmosphere, the surface of the rocket sometimes is subject to extreme heat of several hundred degrees Celsius.

Two new processes in development

The ArianeGroup in Bremen has developed new insulation technologies that offer optimal thermal protection and at the same time can be applied to the tanks in a more environmentally friendly, faster and thus more cost-effective way. Two completely new processes are currently planned for Ariane 6. First, laser surface treatment (LSI): in this process, lasers clean and smooth the surface of the rocket tanks with unrivaled quality, so that insulation material applied later adheres perfectly to the tanks even under the extreme conditions in space. So far, solvents have been used for this in a chemical process.

Secondly, a newly developed thermal protection called external thermal insulation (ETI) will also be applied. Robots spray the special PU foam fully automatically onto the surfaces of the tanks, followed by milling work, which ensures accessibility for subsequent work inside the tanks.

Future of the European launch vehicle

The new insulation technologies play their part in making Ariane 6 much cheaper and faster to build. For example, ETI replaces several insulation materials previously used, which considerably reduces the number of work steps required. Both the foam used and the LSI process are environmentally friendly and generate virtually no industrial waste – expensive disposal is no longer necessary. Overall, insulation costs are reduced by about half compared to Ariane 5. And the new, significantly more efficient technologies will also help to ensure that 12 Ariane 6 rockets can be built each year in the future – a maximum of only seven Ariane 5 launch vehicles can be delivered annually.

The innovative insulation processes are also highly interesting for application in other areas. For shipping, for example: the first cruise ships are using an environmentally friendly liquefied natural gas (LNG) propulsion system that, like the Ariane 6, requires perfect, cost-effective insulation of their tanks that can be produced in series. In enabling this, the ArianeGroup developers also support the green revolution for the world's oceans.

The development of the new technology is currently nearing completion. A first Ariane 6 tank has already been subject to the process. Further pilot applications will follow soon before the processes are actually used in the production of the first Ariane 6.

Robots test cockpit devices

Thanks to RoCCET, consistent and reliable predictions about service life are possible.

So far, maintenance staff have decided whether lights or switches need to be replaced by looking and touching. But the optical and haptic sensation is very subjective. And it is impossible to predict whether a functional part will be worn out in a few days or weeks.

Fully automated and always consistent

In the Robot-Controlled Cockpit Electronics Testing (RoCCET) project, Lufthansa Technik's Aircraft Component Services division has developed the world's first robot system for such tests. The robot uses a gripper arm to operate all switches on the operating units of a cockpit and measures the forces that are required. A camera simultaneously records the luminous intensity of all displays from different angles. And another camera looks for external damage to the instruments.

All this is done fully automatically and always according to uniform specifications. The system thus reduces the workload for employees and the maintenance effort per unit by up to two hours.

Looking to the future

What's more, the measurement data collected by the robot can be combined with existing aircraft data and analyzed alongside it. This makes it possible to determine exactly when the life cycle of a display or switch is coming to an end. This predictive maintenance enables the part to be replaced in good time before it fails. This increases the reliability of the equipment and reduces unplanned maintenance of the aircraft – their operational readiness increases accordingly.

Lufthansa Technik developed the robot-based test procedure from 2016 to 2018. It is currently in the integration phase and is to be used in 2019 for testing the first cockpit control units. In the future, the method can also be used for testing other control units in the cockpit or cabin.

Digital construction manual for the Ariane rocket

The ArianeGroup in Bremen will take over the entire integration of the Ariane 5 and Ariane 6 upper composites with mostly digital processes in the future.

The upper composite sits at the topmost tip of a launch vehicle. After launch, it is separated in orbit from the central stage and injects satellites into orbit. The ArianeGroup is assembling the upper composites for Ariane 5 and 6 in Bremen; in technical jargon, this is called integration. All components, large and small – such as tanks, the engine, the outer shell, electrical elements and piping – are assembled into a finished upper composite.

The process is highly complex. The integration of a single Ariane 5 upper composite takes an average of three months – provided no disruptions occur. A total of up to 60 employees are involved in the process. The ArianeGroup builds six Ariane 5 upper composites a year, always working on three models in parallel.

Digitizing complexity

So far, hard copy has prevailed. This means the mechanics and quality inspectors are provided with a printout of the work steps at the beginning of each workday. It's not ideal. For example, it is not very convenient to handle the papers in the very small installation space of the Ariane 5 upper composite, which has a diameter of only 5.40 meters.

In the Future Launcher Integration Concept (FLIC) project, the ArianeGroup is researching digital processes for the integration of the new Ariane 6 upper composite. Instead of printed documents, employees shall in future be provided with all important information in digital form on a tablet or data glasses. Smart monitors at fixed workstations, from which employees can access all data at any time, are also being considered.

The newly developed software transmits work instructions and 3D images of the components to the mechanics via tablet or data glasses. In addition, the mechanics can enter feedback, such as torque or other measured values, or report faults to the production system.


Unique in the world

A special highlight of the project and unique in the world so far are so-called intelligent network plans: The system monitors the strictly prescribed sequence of work steps and checks which employee can best be deployed to which position. If a work process comes to a standstill, the system automatically calculates where the mechanic concerned can continue to work most efficiently – taking into account, for example, whether the necessary materials are available. In the past, these decisions had to be made by the team leader on the basis of printed workflows. The efficiency gain is considerable.

No one-way street

The digital technologies developed in the FLIC project also facilitate complex and time-consuming documentation. During their work, employees have to record exactly which components they have installed where, using what methods. In the future, these data will be digitally recorded via tablet or data glasses. This saves time and reduces the likelihood of error. Handovers also become easier when digital. If, for example, an employee glues a part in his shift, he can electronically store how long the glue needs to dry. The colleague in the next shift can read this note and know when he can continue working on the component.

Demonstrator in use, industrialization in view

The FLIC project has been running since 2016 and will be completed in April 2019. The result is a demonstrator and software to display the digital processes on electronic devices such as tablets or data glasses. By 2023, the system should be suitable for industrial use, i.e., the upper composites of the future Ariane 6 will be built as standard using digital work processes. Ariane 6 is scheduled to launch in 2020 and be fully operational by 2023.

FLIC is part of a larger research project to develop new technologies for the Ariane upper composite. The project is financed in part by the German Aerospace Center (DLR). In addition to the DLR, the ArianeGroup also cooperates with the universities of Bremen and Wismar.

A demonstrator that resembles an Ariane 5 upper composite assembly can be used by integration staff and technology enthusiasts to test the electronic process.

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