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The ESTHER shock tube is a new state-of-the-art facility at InstitutoSuperior T\'ecnico designed to support future ESA planetary explorationmissions. Its driver is a high-pressure combustion chamber using a mixture ofHe:H2:O2 ignited by a high-power Nd:YAG laser. Both hydrogen as an energyvector and laser ignition are promising techniques with applications inhigh-pressure combustion. The influence of gas mixture and laser parameters,namely the air:fuel ratio, filling pressure, inert gas dilution and ignitionmode, on the combustion and thus shock tube performance were extensivelystudied. A second, low-velocity driver mixture with nitrogen in place of heliumas a dilutant was also studied and experimental shots are done.  Our results show that the filling pressure and helium dilution are the mostdominant parameters in both peak pressure, acoustic oscillation and combustionvelocity. The gas mixture peak pressure and acoustic wave amplitude increasewith the increased filling pressure. Yet, the increased filling pressure lowersthe combustion velocity. The helium in the mixture had a dilution effect, withit lowering the overall effectiveness of combustion. Having higher dilutionfactors lowers the combustion compression ratio, acoustic waves amplitude andflame velocity. The air:fuel equivalence ratio influence was expected withfaster flame and peak pressures at the stoichiometric region. Nitrogen dilutedshots have drastically lower compression ratios and flame velocity whencompared to the helium ones, besides it, the acoustic perturbation wasstronger. ``tulip" flames and deflagration to detonation transitions phenomenawere identified in some of the experiments.

European Shock-Tube for High-Enthalpy Research Combustion Driver Qualification