Use of a single CO₂ coolant in a Cascade manner for thermal protection of hypersonic vehicles

To address the thermal protection of hot-end components in hypersonic vehicles under extreme high-enthalpy aerodynamic heating, this study proposes and experimentally validates a channel–film combined cooling scheme based on the cascaded use of a single CO₂ coolant. Tests were conducted on a direct-connect high-enthalpy supersonic ground-test platform, where a liquid oxygen–alcohol gas generator produced a mainstream with a total temperature of approximately 3300 K and a Mach number of 2.2. Channel cooling, film cooling, and channel–film combined cooling were comparatively evaluated under the same nominal mainstream and coolant-supply conditions. In the combined configuration, CO₂ first absorbs heat in the internal channels and is then injected to form an external cooling film, thereby integrating internal heat absorption and external thermal shielding within a single-coolant system. Channel cooling alone exhibited upstream heat accumulation, whereas film cooling alone showed downstream deterioration caused by mainstream mixing. In contrast, the combined configuration provided more stable thermal protection through the synergistic effect of the two cooling mechanisms. At a CO₂ mass flow rate of 100 g/s and a heating duration of 23 s, the representative late-stage wall temperatures were maintained within 254–274 K, compared with maximum wall temperatures of 1051 K for channel cooling and 557 K for film cooling. These results demonstrate the effectiveness of cascaded single-CO₂ channel–film cooling for local thermal protection of hypersonic vehicle seekers.