Parabolic flights - short time mug-flights of 25 a each - are used to deter
mine the parameter ranges for the upcoming long term experiment an complex
plasmas on the International Space Station (ISS) - the Plasma Crystal-Exper
iment (PKE). The experimental results of approximately 170 parabolic flight
s conducted in 1999 are summarised. As an example, the interaction of micro
particles of two different sizes in an rf-discharge is investigated on para
bolic flights under microgravity conditions.