This paper presents an experimental study of the influence of viscous flows on the aerodynamic behaviour of waveriders. This investigation was carried out in the MARHy facility, under supersonic and rarefied flow conditions. Three supersonic and low density flow conditions were tested operating at Mach 2 and 4 with free stream pressures of 8 Pa and 2.67 Pa giving slip regime flows. Knudsen numbers associated with these flow conditions and this test model are between 2.79 10-3 and 7.33 10-4. In terms of pressure, these conditions are similar at altitudes between 50 km and 80 km. The studied waverider has a geometry proposed in the literature and optimised for a Mach 10 flow and an altitude of 50 km. The purpose of this work is to experimentally analyse how viscous effects will affect the aerodynamic performances of the waverider in off-design conditions. This work is based on the analysis of the upper and lower shock wave angles obtained from glow discharge imaging technique for different angles of attack and the three operating conditions. Results showed that the evolution of shock wave angles are Mach number dependent, as predicted by the inviscid shock relations, but also strongly depends on the flow pressure. From these experimental results, fitting equations have been established to predict the variation of upper and lower shock angles with the flow density, Mach number as a function of the angle of attack in continuum and especially in slip regime. Shock wave angles behaviour are compared to measured Lift-to-Drag ratio. Comparison presents a similar behaviour with flows conditions and shows that viscous layers appearing at low densities have a great influence on aerodynamic forces.