Have you considered a Tesla turbine at all? Its kinda the same only the casing is stationary with the impeller (a simple set of disks) spins. Both designs rely on surface friction and i would not know what kind of efficiency you would get with a Pitot design. The army did a study on the Tesla design for small turbines (aka about the same size) and got a efficiency in the 20% region. plenty good enough for a fun rocket!.
Greg