Vol.:(0123456789) 1 3 Experiments in Fluids (2021) 62:135 https://doi.org/10.1007/s00348-021-03225-4 RESEARCH ARTICLE Shock/shock interferences in a supersonic rarefied flow: experimental investigation Vincente Cardona 1  · Romain Joussot 1  · Viviana Lago 1 Received: 18 January 2021 / Revised: 25 March 2021 / Accepted: 7 May 2021 / Published online: 7 June 2021 © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021 Abstract The interaction of two spheres immersed in a Mach 4 flow is experimentally studied at a static pressure of 2.666 Pa, repre- senting 80 km in altitude. This work was carried out in the hypersonic and rarefied facility MARHy, and aims to investigate the rarefaction effects on the fragmentation of space debris, and their becoming during atmospheric re-entry. Indeed, after fragmentation, the new debris will, in turn, interact with each other, which can lead to a change in their trajectory. The purpose is to investigate some interactions that can occur during high altitude phase of the atmospheric re-entry. This paper is focused on the analysis of shock/shock interference between two similar spheres interacting in a rarefied supersonic flow, where the second sphere is displaced in the wake of a first sphere, considered as the parent debris. The flow field was examined using the glow discharge technique. An adapted image processing was applied to the detailed analysis of shock wave interactions. Edney-type interactions were identified and discussed as rarefied experimental conditions introduce viscous effects. Compared to continuum regime, the thickness of the shock wave shapes modifies the shock wave interactions. Graphical abstract List of symbols  Mean free path (m)  Dynamic viscosity (Pa s)  Density (kg m −3 )  Similarity number D Sphere diameter (m) Kn Knudsen number Ma Mach number p Pressure (Pa) Re Reynolds number R m Specific gas constant = 287.058 m 2 s −2 K −1 * Vincente Cardona vincente.cardona@cnrs-orleans.fr Extended author information available on the last page of the article