A relatively low drag, completely free-flying, tubular vehicle comprises a body that defines a leading edge and a trailing edge and includes an external surface and an internal surface each extending from the leading to the trailing edge. The internal surface has an axially converging upstream section extending from the leading edge to a discontinuity that constitutes a throat in the vehicle. The internal surface also has an axially diverging downstream section extending from the throat to the trailing edge. The internal surface is configured to enable introduction and mixing of fuel into an airstream flowing therethrough, and to generate a shock wave when in flight. The shock wave is of such magnitude and direction as to create a hot spot that subsequently causes ignition and combustion of the fuel-air mixture. The combustion causes formation of a detonation bubble and migration of the associated wave front upstream to stabilize slightly downstream of the throat. The combustion of the fuel results in rapid expansion of combustion products, generating forward thrust against the internal surface of the vehicle.