In this paper we present the first exploration of detonation wave propagation dynamics in premixed supersonic flows using a novel rotating detonation engine (RDE) configuration. An RDE with a coupled linear extension, referred to as rho DE, is used to divide detonations traveling radially in the RDE into linearly propagating waves. A tangential propagating wave is directed down a modular tangential linearized extension to the engine for ease of optical diagnostics and hardware configuration investigations. A premixed Mach 2 supersonic linear extension is coupled to the rho DE to investigate the effects of varying crossflow configurations for detonation propagation, particularly the interaction between detonations and supersonic reactive mixtures. Detonation waves are generated at the steady operating frequency of the RDE and visualized using high speed schlieren and broadband OH* chemiluminescence imaging. The stagnation pressure was varied from over- to ideally-expanded supersonic regimes. Experimental analysis of detonation interaction with the supersonic regimes show that the detonation propagates freely in the ideally-expanded regime. Deflagration-to-detonation transition (DDT) occurs in the overexpanded regime. Based on the data collected, the DDT process favors supersonic flow with higher source pressures. 2019 Hydrogen Energy Publications LLC. (C) Published by Elsevier Ltd. All rights reserved.