Space weapons have been debated intensely in the past. The latest instance of prominent debate is over their use for ballistic missile defense. But this is not the only possible role for space weapons, and that fact raises a further concern: What if an adversary were to develop such weapons? Could one? Why would it? It is time for broader public discussion of the issues. Before deciding to acquire or forgo space weapons for terrestrial confict, the United States should fully discuss what such weapons can do, what they will cost, and the likely consequences of acquiring them. The authors of this report seek to aid this discussion not by arguing for or against space weapons but by describing their attributes, classifying and comparing them, and explaining how each might be used. The authors also explore how a nation might decide to acquire such weapons and how other nations might react.