Whereas much attention is devoted to negotiating norms and formal agreements for the peaceful use of outer space, domestic factors that push for the development of space-based weapons receive minima! attention. Despite serious doubt about the effectiveness of missile defense and the technical feasibility of space-based weapons, the United States has spent well over $130 billion on research and development of them, including at least $10 billion currently. This article examines four domestic drivers that may explain why such investment persists: the defense perspective and ideology of the Republican Party; the belief that US satellites may require space-based protective weapons; the huge investment of the military contractor corporations, including their efforts to influence legislation and cultivate contacts; and the private advocacy groups that support US military domination of space. A number of countervailing drivers exist to mitigate against development of these weapons, with perhaps the most powerful factor restraining space-based weapons development being their wildly high costs.