Silent Air Taxi - Fraunhofer IPT - Christoph Baum - Drive technology - propulsion technology

Interview with Fraunhofer IPT – Trends in Propulsion Technology in Aviation

Jennifer Weitbrecht
29.10.2019
4 pictures
5 minutes

As we previously reported, we attended the unveiling of the Silent Air Taxi in Merzbrück, Aachen. In so doing, we took the opportunity to touch base with Dr Christoph Baum, managing director of Fraunhofer IPT (Institute for Production Technology) as well as Dr.-Ing. Sascha Gierlings, head of the turbomachinery technology transfer department and head of the turbomachinery BU, and discuss the future of drive technology in aviation.

Interview with Dr Christoph Baum

WingMag: What is Fraunhofer IPT’s contribution to the Silent Air Taxi project?

Fraunhofer IPT: Fraunhofer IPT is delivering ideas first and foremost:

Mr Wellensiek, who is driving the project forward operationally, continues to be on the staff at Fraunhofer IPT. In the meantime, he is of course primarily working for e.SAT GmbH. In the course of this, above all many organisational basic ideas for the project have stemmed from Fraunhofer IPT. Furthermore, Fraunhofer IPT has led the way in subject areas such as selecting technology and road mapping. IPT is able to derive a range of relevant research issues, particularly in the context of future mobility, thanks to the close collaboration with e.SAT GmbH.

Prof Dr Günther Schuh is not only CFO of e.SAT GmbH and CEO of e.GO Mobile AG, but also one of the four directors of Fraunhofer IPT. He is therefore able to harness our technical expertise, particularly in terms of electromobility.

WingMag: What makes aviation technologically interesting for Fraunhofer IPT?

Fraunhofer IPT: We have many cross-over points with the conventional aviation industry. This concerns structural components, such as fibre composite plastics and aluminium components, which we are able to manufacture and are the aim of our product technology research.

Moreover, we are at the forefront of developing manufacturing technologies for engine components – something that has already been an area of focus for Fraunhofer IPT for many years. This concerns predominantly very demanding components, such as highly efficient integral compressor rotors (Blisk), as well as extremely safety-critical parts too such as turbine blades. In these fields, we cover a very large range of technology readiness and employ fundamental knowledge on prototypes for use in test rigs. This is a large, important area in which we are operating together with leading manufacturers in the industry.

WingMag: Why a project like the Silent Air Taxi?

Fraunhofer IPT: The hybridisation of the Silent Air Taxi drive train throws up complex challenges to the individual components and how they are integrated into an holistic system. It is very demanding to take the correct technology decisions in terms of quality and cost based on the project’s ambitious timescale and low target prices.

We are manufacturing engine components and undertaking research in production technology. We would like to continue to harness our capabilities in this field for the research work in developing the Silent Air Taxi. The special requirements of the SAT hybrid drive train enable Fraunhofer IPT to continue to advance its existing capabilities and thus to set itself up for the future mobility market in a future-appropriate manner.

The issues arising from alternative drive technologies are thus the logical continuation of our research activities to date.

WingMag: In other words, Fraunhofer IPT is currently focussing on the field of ‘drives’?

Fraunhofer IPT: That is exactly right. In future, that will presumably also lead us into further research areas. For example, we are already getting to grips with hydrogen mobility; in other words: with the subject area of aircraft fuel cells. On this project, we have primarily joined forces with e.GO Mobile AG. We are constructing in-house research and production facilities for researching aircraft fuel cell drives. We are especially interested in researching scalable production methods for fuel cells as energy converters in aircraft.

WingMag: How far advanced is the research in the field of fuel cells? How realistic is it that the technology will take to the skies in five to ten years?

Fraunhofer IPT: I think that in five years we will continue to be focusing research on hybrid systems, such as on the Silent Air Taxi. Such systems work on battery electricity and with a combustion system.

In a timeframe of ten years, I could conceive that the hydrogen-powered fuel cell will assume increasing currency as an energy converter. This is mainly due to the fact that batteries, as being increasingly used in cars, are not so suited to storage on aircraft due to their poor weight ratio.

WingMag: Is it realistic that hydrogen technology will also be deployed for large passenger aircraft, or will it rather remain a technology for small aircraft?

Fraunhofer IPT: It is expected that hydrogen will be used directly as a fuel only for short-range and medium-range routes. A transatlantic flight with hydrogen as energy storage is not expected to be possible even in 30 years’ time.

Whereas hydrogen is very light and the amount of energy that can be stored in relation to weight is very high, the volume of the required hydrogen is also very high.

You will encounter issues with this when you come to long ranges. There are many studies proving that ranges of 1,000 to 1,500 kilometres are able to be covered very effectively with this technology. When it comes to longer ranges, it is questionable whether hydrogen is directly suitable for storage. However, hydrogen can be used in turn to generate synthetic fuels. Hydrogen is thus essential as a secondary energy carrier to achieve CO2 neutrality with synthetic fuels even for longer ranges.

WingMag: Which further trends are under development in terms of drive technology?

Fraunhofer IPT: In aviation, you can see a clear trend towards fully electric drives based on batteries and electric motors particularly for applications with short ranges for Urban Air Mobility. The ranges are mostly 20 to 30 kilometres and therefore can be executed on battery electricity. The fully electric configuration moreover enables entirely new aircraft designs, enabling even closer collaboration between aircraft design and drive train development.

The concepts being discussed in the field of aviation for long distances are otherwise principally based on optimising gas turbines as we know them today. Next generation turbo fans then initially include geared turbofanswith various optimisation levels. When they will be able to be operated with synthetic fuels is highly dependent on the politicians and regulatory framework conditions. We do not expect that there will be a shift any time soon to entirely different drive concepts, that is: away from gas turbines, for aircraft with long ranges.

by Jennifer Weitbrecht

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