The design of a nuclear rocket vehicle requires a thorough understanding of the fluid and thermodynamic behavior of the liquid-hydrogen propellant under severe environmental conditions, including nuclear radiation. To gain a better understanding of this behavior, ground testing under simulated conditions is required. Adequate simulation of most individual phenomena can be achieved by careful selection of test conditions. This selection is based on derived nondimensional groups.Similarity analyses were performed to define the nondimensional groups and boundary conditions necessary for simulating the liquid-hydrogen-propellant behavior of a nuclear rocket vehicle. The modeling techniques -- dimenstional analyses and normalization of governing equations -- are described in detail, and the use of the derived scaling groups in developing a test design is demonstrated.