We introduce the DLR institute “Simulation and Software Technology” (SC) and present current activities regarding software engineering and high performance computing (HPC) in German or international projects. Software engineering at SC focusses on data and knowledge management as well as tools for studies and experiments. We discuss how we apply software configuration management, validation and verification in our projects. Concrete research topics are traceability of (software development) processes, development in distributed teams, automated software engineering, knowledge management for software development and usability. A further important topic is the development of software and data integration frameworks. HPC research at SC focusses on parallel algorithms and data structures for numerical libraries, optimization tools and pre- and post-processing. For HPC simulation codes, we apply modern parallelization techniques like hybrid programming, OpenCL or OpenACC to exploit many-core or GPGPU hardware efficiently. We present results from current German and European extreme computing projects regarding eigensolver and pre- and post-processing developments. Algorithmic optimization developments play an important role in a DLR project on thermal management of spacecraft. OpenACC programming is employed to accelerate helicopter simulation. For cataloging space debris, we develop parallel and distributed sensor network and data base technology.