The Department of Transport and Propulsion Systems researches and develops transport and propulsion technologies for spacecraft systems.

Key research areas include fuel handling in fuel-storing and components and supply components such as the tanks and pipes, most notably for the cryogenic upper stage systems. The efficient management and successful control of the fuel in the cryogenic upper stage systems is key for achieving development goals such as carrying out missions with long ballistic free-flight phases and multiple re-ignitions of the engine. 

The main areas of research include cryogenic tank systems, handling systems for flight phases with little acceleration, cryogenic fuel transfer, handling technologies and the long-term storage of cryogenics.

The Institute of Space Systems has all the equipment needed to research and develop these technologies, with its unique cryogenic laboratory, which includes special test rigs. The cryogenic laboratory provides a place to carry out experiments on cryogenically cooled liquefied gases, real fuel in launcher systems, or even on liquid hydrogen at temperatures down to -253 degrees Celsius.

The Department also develops numerical simulation tools for explaining and analysing the behaviour of the fuel as well as designing the systems themselves.

The Department is leading the 'Research Association Upper Stage' project in cooperation with other DLR Institutes, the University of Bremen and the national space industry, whose aim is to research the key technologies identified. The overall aim is to strengthen national competency in upper stages. The knowledge gained in the cryogenic laboratory is of significant importance.