A carbon dioxide reduction system is being developed for long-duration manned space missions. The system incorporates a Sabatier methanation reactor, utilizing previously developed catalyst materials, and a hollow fiber membrane unit to separate the products of reaction. Heat produced by the exothermic Sabatier reaction is absorbed by an air stream, which also regulates the reactor temperature to maximize yield. This absorbed heat can be utilized elsewhere in the carbon dioxide management system to reduce power requirements. The Sabatier process combines carbon dioxide and hydrogen to form methane and water. In a manned space environnent, the water is then either electrolyzed to form oxygen for breathing and hydrogen to drive the reaction, or recycled to the potable water system.A computer-based performance model using finite elements has been developed to evaluate reactor design and catalyst performance. Laboratory testing of the Sabatier reaction using various catalyst materials is ongoing, with preliminary results reported in this paper.