Plastic nuclear track detectors were used to measure the contribution of Hi
gh charge Z and energy E (HZE) particles to the radiation exposure of manne
d space missions. Results from numerous space missions in the orbit planned
for the International Space Station are compared. The measurements cover t
he declining phase of the last solar cycle during the past 7 years and vari
ous shielding conditions inside the US Space Shuttle and the Russian MIR-st
ation.