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The flow enthalpy of an arc-heated wind tunnel is an important parameter for reproducing planetary entry and performing heating tests. However, its distribution is insufficiently clarified owing to complicated phenomena, such as arc discharge and supersonic expansion. In this study, we assess the enthalpy of an arc-heated flow in a large-scale facility based on measurements and computational results. The flow enthalpy of high-temperature gases, which comprised thermal, chemical, kinetic, and pressure components, was reconstructed based on the measured rotational temperature, heat flux, and impact pressure, in addition to the computational science approach. The rotational temperature of nitric oxide molecules was obtained using emission spectroscopic measurements of band spectra in the near-ultraviolet range. A numerical model was developed and validated based on measured data. The results indicated that the model efficiently reproduced the arc discharge behavior in the heating section and the thermochemical non-equilibrium in the expansion section. It was discovered that the dominant components of the arc-heated flow in the test section were the chemical and kinetic components. The flow enthalpy exhibited a non-uniform distribution in the radial direction. We conclude that the flow enthalpy of the core is approximately 28 MJ/kg at the nozzle exit.

Two liner-less CFRP concept tanks were prepared for internal pressurization tests at liquefied nitrogen (LN 2 ) temperature. The tanks were designed in two patterns of eight-ply UD quasi-isotropic lay-up, in the shape as a cylinder of 600 mm in diameter and 1200 mm in length, covered with an aluminum flange at one end and with a CFRP hemisphere dome at the other. The maximum strain was applied as the damage onset condition so that the internal pressurization at LN 2 temperature did not damage them up to 1.1 MPa. Damage onsets, such as transverse cracking and leak path formation, were monitored during the tests using helium flow detection, acoustic emission, and pressure-strain monitoring. The CFRP concept tanks showed no damage in the 1.1 mm thick cylindrical gauge section under pressurization up to 1.1 MPa at LN 2 temperature. The design was thus shown to be successful in keeping the CFRP tanks intact.

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