Synchronous acceleration of two millimeter-sized bodies up to hypersonic velocities in a multichannel railgun

A two-channel electromagnetic railgun accelerator of bodies of original design is described. Using this device, synchronous group flight in the atmosphere has been realized for two plastic cubes with a 2-mm edge length and $\sim$ 0.01-g mass each at a velocity exceeding 4 km/s. The flight and related gas-flow patterns have been monitored by high-speed photography using a double-frame schlieren system.