Slender fast-response static pressure probes are tested in the Longshot hypersonic wind-tunnel with free-stream Mach number larger than 10 and Reynolds number 30000 approx＜ Re_D approx＜ 60000 based on the probe diameter. They aim at improving the characterization of the free-stream. Numerical simulations predict the wall pressure measured to be within 5% of the free-stream static pressure. The viscous effects along the probes are found experimentally to be limited for L/D ＞ 16.5 in agreement with numerical results. Limited influence of the angle of attack of the probes is found for α ＜ 2 ° thanks to the probing geometry used. The free-stream quantities at the nozzle exit (Mach, Reynolds...) are derived from the static pressure measurements and compared to those estimated assuming an isentropic nozzle flow expansion. The usefulness of static pressure probes is demonstrated through their ability to detect possible non-isentropic nozzle flow expansions which do not influence traditional measurements such as the test section stagnation pressure. This direct access to free-stream quantities allows to significantly improve the accuracy on the free-stream quantities and benefits to the characterization of hypersonic wind-tunnel flowfields.
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