From February to March 2025, postdoctoral researcher Constantin Traub completed a four-week research stay at the University of Manchester with Dr. Nicholas H. Crisp (https://www.linkedin.com/in/nhcrisp/) as part of the Space Systems Research Group (https://uk.linkedin.com/company/space-systems-engineering).
Together, the two researchers worked on gaining deeper insights into the dynamic behavior of spacecraft in Very Low Earth Orbit (VLEO, approx. 200 km to 450 km altitude), which are equipped with Atmosphere-Breathing Electric Propulsion (ABEP). This regime promises enormous advantages for both commercial and scientific applications, but its realization is associated with enormous technological challenges.
The stay was made possible by an ‘Early Career Outgoing Fellowship’ for C. Traub as part of the ‘Global Glimpse Funding Programme’ of the University of Stuttgart (https://www.beschaeftigte.uni-stuttgart.de/weiterbildung/auslandsaufenthalt/global-glimpse/). This programme supports professional and institutional networking, the development of scientific projects and publications with an international focus and partners and therefore offered an ideal funding opportunity for this stay.
Both institutions have already been cooperating in this area for some time and want to further intensify this cooperation in the long term.
Collaboration background
The University of Stuttgart and the University of Manchester were already collaborating intensively on the Disruptive Technologies for Very Low Earth Orbit Platforms (DISCOVERER) project, which was funded by the European Union's Horizon 2020 research and innovation programme (2017-2022) and represented the largest concentrated research effort to date on VLEO satellite concepts focused on Earth observation missions. The project was led by Dr. Peter Roberts (https://uk.linkedin.com/in/peterceroberts) from the University of Manchester. This joint project work has resulted in a large number of high-quality joint publications.
In 2023, the German Research Foundation (DFG) approved the Collaborative Research Centre (CRC) 1667 ‘Advancing Technologies of Very Low Altitude Satellites’ (ATLAS) (https://www.sfb1667.uni-stuttgart.de/), which addresses the fundamental scientific and engineering challenges associated with the accessibility of VLEO. To foster collaboration between the research institutions and due to his unique experience in this field, Dr. Roberts serves as one of the Scientific Advisors and also as Co-Chair of the 2nd International Symposium on Very Low Earth Orbit Missions and Technologies (https://www.sfb1667.uni-stuttgart.de/news/2nd-VLEO-Symposium-2025-concludes/), a follow-up event sponsored and organised by ATLAS to the first VLEO Symposium hosted by the DISCOVERER team in June 2021.
For Dr. Crisp and Dr. Traub, it is of great interest to promote the research community in this field. For this reason, Dr. Crisp organized a special session on VLEO at the International Astronautical Congress (IAC) 2024 in Milan, in which Dr Traub participated as one of the keynote speakers. A similar session was also held at the 2nd VLEO Symposium, which was very well received. A corresponding application has already been submitted for the International Astronautical Congress 2025 (https://www.iac2025.org/) in Sydney, Australia, in September in order to drive the initiated process forward in the long term.
Current research
ABEP is a key technology for enabling sustainable exploitation of the VLEO regime. Various research groups worldwide are working on the development of these systems and their key components. In addition to these practical activities, the successful realisation of this technology also requires in-depth theoretical analyses that map the dynamic interaction of the individual components. To date, however, such studies have been largely absent from the literature. The results of the stay should help to close this gap.
Although in theory an ABEP system has no need for fuel replenishment, its power requirements are enormous. This is usually the limiting factor for possible orbital manoeuvres or the lowest achievable altitude. For satellites in VLEO, the power is usually realised via solar cells and thus scales with the area that is aligned to the Sun. Even with the best possible orientation of these solar cells, larger solar cell areas inevitably lead to higher aerodynamic drag, which in turn must be compensated for by the propulsion system. This varies dynamically due to very complex and diverse interactions.
In order to be able to analyse the effects of different parameters and concepts on the resulting optimal manoeuvre strategy in the long term, an efficient simulation infrastructure is required that adequately depicts these dynamic relationships. The foundation for this was laid during the research stay.
This cooperation is the ideal prerequisite for achieving this ambitious goal. IRS has many years of experience in ABEP engine development (Dr. Herdrich's research group (https://www.irs.uni-stuttgart.de/forschung/raumtransporttechnologie/raumfahrtantriebe/)) and the dynamic modelling of complex systems, which could be incorporated into the project. Conversely, through the ADBSat tool (https://github.com/nhcrisp/ADBSat), the University of Manchester has contributed a globally recognised and used tool for the efficient dynamic determination of aerodynamic coefficients of satellites in VLEO and experience with the effect of ABEP systems on the design and layout of spacecraft.
The results of this work will be presented at the International Astronautical Congress 2025.
Life beyond work
In addition to gaining scientific knowledge, a research stay also serves to get to know the people and culture of the host country, to exchange ideas and to learn from each other. Manchester has proved to be extremely open and friendly in this respect. Manchester is a vibrant city, known for its industrial past, its legendary music scene (including Oasis and The Smiths) and its world-famous football clubs Manchester United and Manchester City. Today, it is a modern cultural and economic centre with impressive architecture, creative districts and a lively pub and art scene. The campus is a mix of historic buildings and modern facilities that stretch along Oxford Road - one of the busiest university streets in Europe. It is home to impressive Gothic buildings such as the John Rylands Library and state-of-the-art research centres. The campus offers numerous green spaces, libraries, cafés and student facilities that create a lively academic atmosphere. Thanks to its central location, the city centre with its shops, museums and bars is easily accessible. In addition, the Manchester Aquatics Centre is less than a minute's walk from the Nancy Rothwell Building, where the group is based. This made it possible to do regular sport before work. In addition, he and Dr Crisp went to the ‘Manchester Road Runners’ running club on Wednesdays.
Special highlights included a visit to the English Track Cycling Championships, Manchester City home games at the Etihad Stadium, Manchester United at Old Trafford and a trip to Liverpool, which will certainly be remembered for a long time to come.
Personal conclusion
The everyday life of a postdoc is often dominated by day-to-day business so that it is sometimes difficult to keep an eye on or pursue the overarching research goal. Due to the change of working environment and the multitude of new impressions, such a research stay helps to refocus, motivate and concentrate on the essentials again. Even though it involves a considerable amount of preparation and follow-up work, it is a unique opportunity for personal and professional development that far outweighs the costs (both in terms of time and money). Overall, it really was a great experience for me and I hope to do it again in due course.
The University of Manchester and Dr. Nicholas Crisp in particular were very welcoming and warm and I am very grateful for that. I would very much like a return visit in the foreseeable future. I am also looking forward to working with you in the future!
I am also grateful to my professor Stefanos Fasoulas, who has supported and encouraged this stay from the very beginning. Last but not least, I would like to thank the Global Glimpse funding programme of the University of Stuttgart for its support, without which the stay would not have been possible.