A gas-arc discharge is strongly influenced by the force of gravity. In this study, endohedral metallo-fullerenes and single-wall carbon nanotubes are produced by means of a gravity-free gas-arc discharge and their production efficiencies are compared with those produced by the conventional gravity method. As a result, their production rates are found to dramatically increase. The reason is conjectured to be stabilization of the arc and the longer reaction time of the cluster production under the gravity-free and convection-free conditions.This article was due to appear in issue 5 of Plasma Physics and Controlled Fusion. To access this special issue please follow this link: http://www.iop.org/EJ/toc/0741-3335/45/5.