This report presents an argument for reenergizing U. S. space nuclear reactor development. Over the next 10 to 20 years, missions with high power requirements (200 kWe or greater) will be essential to maintaining U.S. freedom of action in space. Nuclear power provides the only practical method of achieving such power levels in the requisite timeframe. Specifically, this report presents two rapid prototyping approaches for fabricating and testing complete 200 kWe nuclear electric propulsion (NEP) systems in a non-nuclear simulated space environment. Both approaches involve heat-pipe-cooled reactors with direct energy extraction to minimize moving components. System operation would occur in a thermal vacuum chamber and include a high-fidelity reactor control simulator developed from zero-power tests. Either approach would provide the detailed systems engineering data necessary to project the performance, cost, and schedule accurately for a future program and would also redevelop U.S. nuclear design and manufacturing talent bases and reestablish space nuclear reactor development facilities. Application of lessons learned from previous failed development attempts and the adoption of a rapid prototyping approach would mitigate development risks while gradually eroding the negative political environment associated with space nuclear power.