Breathing oxygen supply for long-duration manned space missions such as the NASA Space Station may be generated by electrolysis of water produced by the reaction of metabolic carbon dioxide and hydrogen in a Sabatier Methanation Reactor (SMR). A Space Station probable restriction on venting of carbonaceous gases to space will require onboard management of SMR product methane. This may be accomplished via methane decomposition to hydrogen and carbon. The hydrogen could be recycled to the SMR and the carbon would be stored onboard. Under contract with the NASA Johnson Space Center (JSC), Hamilton Standard is currently developing a Carbon Formation Reactor (CFR) that decomposes methane to gaseous hydrogen and dense solid carbon via high temperature pyrolysis. In this paper, the fundamentals of methane pyrolysis to carbon are described and the results of CFR development efforts to date are presented. Based on these results, the performance of a full scale SMR-CFR Carbon Reactor Subsystem (CRS) is projected.