This paper addresses a methodology to parametrically size thermal control subsystems for high-speed transportation systems during the conceptual design phase. This methodology should be sufficiently general to be exploited for the derivation of Estimation Relationships (ERs) for geometrically sizing characteristics as well as mass, volume and power budgets both for active (turbopumps, turbines and compressors) and passive components (heat exchangers, tanks and pipes). Following this approach, ad-hoc semi-empirical models relating the geometrical sizing, mass, volume and power features of each component to the operating conditions have been derived. As a specific case, a semi-empirical parametric model for turbopumps sizing is derived. In addition, the Thermal and Energy Management Subsystem (TEMS) for the LAPCAT MR2 vehicle is used as an example of a highly integrated multifunctional subsystem. The TEMS is based on the exploitation of liquid hydrogen boil-off in the cryogenic tanks generated by the heat load penetrating the aeroshell throughout the point-to-point hypersonic mission. Eventually, specific comments about the results will be provided together with suggestions for future improvements.