Virtual environmens(VE) technology is expected to make a big impact on future training and simulation systems. Direct stimulation of human senses (eyesight, auditory, tactile) and new paradigms for user input will improve the realism of simulations and thereby the effectiveness of training and simulation systems. After briefly summarising earlier work done at TNO-FEL, a definition of virtual environment simulations is proposed, along with a classification of various types of VE systems. This classification then proves helpful in assessing the applicability of VE technology to trainers and simulators. Next, a prototype system for training EVA procedures is described. Finally, the conclusions from this work are drawn, and directions for future research and development activities at TNO-FEL are given.