The aim of  the CaRu experiment  is  to  investigate  the  influence of milligravity on  the  so  called  Runge-Instability  that  leads  to  development  of  Runge Pictures.  Runge-Instability is deeply connected to the field of capillarity  as  it  describes  the  unsteady  spreading  of  the  color  appearances that come to existence when a fluid A spreads through a porous structure and this fluid A chemically reacts with a fluid B which the porous structure has been impregnated with before. Capillarity under low gravity is of interest because it can be used to transport fluid fuel in spacecrafts. Therefore there  have  been  studies  on  this  topic  for  years  -  recently  ZARM  from Germany started an experiment on  the space station. Despite of  the  interest in capillarity as such  there has not  yet been an experiment centered on  the Runge-Instability and  the  influence of milligravity or a  throughout exploration of  the  effect.  Scientific  research  in  that  direction  is  relevant,  too,  because there is an interesting connection between science and art. CaRu would result in production of art in space next to the scientific achievements. 

CaRu  is  going  to  find  out  how  gravity  influences  the  climb  of  the  Runge-Instability  in the direction  of  the  gravitational  force.  A  connection  between  flow velocity  and  existence/development  of  the  instability  is  being  expected, as 

diffusion  is  acting  against  it  and  grows more  important  as  the  fluid  moves slower. This  leads Dr. Kuhnert  to anticipate a critical  flow velocity or rather a dimensionless characteristic number. CaRu  is going  to  trace  the  flow velocity 

and  the  fractal dimension at  the spreading  rim of  the picture  to characterize the Runge-instability, which has not been done before.