A permanent presence in orbit and, as consequence, the storage of fluids in space makes it necessary to provide a qualified mean which is used for search and localisation of leakages in space. In this paper, dominating flow regimes are explained of leaking gases and liquids in vacuum which are dependent on their physical properties and on leak geometry. A large number of different mechanical, thermal, electrical, physical and laser optical methods have been assessed and traded which potentially are suited for design of a proper leakage detection system in space. Particularly one laser optical technique was found to best meet the requirements for leakage detection in space combined with thermographic image analysis. The working principle of the proposed laser optical method is based on remote sensing of a leakage flow by the aid of a scanning laser beam.