Dear Fu-Kwun,<br />thank you for info and applet. I try to look on it. Now I am in review of my article to Physics Education about the astroblaster, where I try to explain collisions for rather coefficient of restitutions between the balls, it can be an idea for improvment of the applet....tha mass ratio it can be calculated for specific coefficient of restitution, (ideal case e=1) but in real conditions, if somebody would like to create own one and has the real balls, the exact mass for maximum height can be calculated.... I can show you...if you wish...we can implemented it into the applet...<br />Marián