Experimental determination of momentum transfer coefficients in hypersonic free molecular flow and distribution function recovery of reflected molecules

This paper investigates the nitrogen molecule interaction with surfaces at 2eV for a developed adsorbed layer. A molecular beam is obtained by exhausting nitrogen of 6000 K into vacuum. The momentum transfer coefficients are obtained by means of measuring the forces on plates of different materials in a flow. The mass flux indicatrices are measured, the surface roughness being measured electrochemically. The momentum transfere coefficients are shown to be stable with time, within the measured error. The simultaneous handling of the force and indicatrix data show their consitency. A model funciton of reflected molecules distribution is proposed on the basis of these measurements. The surface roughness increase results in a fall of the momentum transferred to the surface by reflected molecules. A number of approximate formulae is given