In a 2013 book chapter, Blake Messer investigated whether the United States, the E.U., Japan, Russia, or China intended to launch a space reactor.  He concluded that no launches were planned at that time. The following updates Messer’s findings by providing a global watch list of states that have planned SNR launches or are poised to do so. The list is meant to track countries that might compete in an HEU space race. Countries are broken up into three tiers. Tier 1 states have planned or previously launched HEU-fueled space reactors. Tier 2 states have actively researched or indicated interest in HEU space reactors. Tier 3 states have the necessary components to develop either HEU- or LEU-fueled space reactors, but have not yet demonstrated an interest. The necessary components include (1) having a national space program that has satellite launch capabilities, and (2) having either an HEU or LEU stockpile, or a demonstrated enrichment capability.
 Blake Messer, “Space Reactors,” in Nuclear Terrorism and Global Security: The Challenge of Phasing out Highly Enriched Uranium, ed. Alan J. Kuperman (New York: Routledge, 2013): 217.