Abstract: An apparatus includes an energy source and an expansion structure. The energy source is configured to convey an amount of energy operable to increase a pressure of a compressible gas disposed in a chamber. The expansion structure is configured to be placed in fluid communication with the chamber and to receive a flow of the compressible gas in response to the increase in pressure. The expansion structure includes an inlet having a first diameter and an outlet having a second diameter greater than the first diameter and is configured to allow the compressible gas to expand as the compressible gas flows from the inlet to the outlet such that a supersonic free jet of the compressible gas exits the outlet. In some instances, the supersonic free jet of the compressible gas can accelerate, relative to the expansion structure, a projectile disposed outside of the expansion structure.

Abstract: An apparatus includes an energy source and an expansion structure. The energy source is configured to convey an amount of energy operable to increase a pressure of a compressible gas disposed in a chamber. The expansion structure is configured to be placed in fluid communication with the chamber and to receive a flow of the compressible gas in response to the increase in pressure. The expansion structure includes an inlet having a first diameter and an outlet having a second diameter greater than the first diameter and is configured to allow the compressible gas to expand as the compressible gas flows from the inlet to the outlet such that a supersonic free jet of the compressible gas exits the outlet. In some instances, the supersonic free jet of the compressible gas can accelerate, relative to the expansion structure, a projectile disposed outside of the expansion structure.

Abstract: An apparatus includes an energy source and an expansion structure. The energy source is configured to convey an amount of energy operable to increase a pressure of a compressible gas disposed in a chamber. The expansion structure is configured to be placed in fluid communication with the chamber and to receive a flow of the compressible gas in response to the increase in pressure. The expansion structure includes an inlet having a first diameter and an outlet having a second diameter greater than the first diameter and is configured to allow the compressible gas to expand as the compressible gas flows from the inlet to the outlet such that a supersonic free jet of the compressible gas exits the outlet. In some instances, the supersonic free jet of the compressible gas can accelerate, relative to the expansion structure, a projectile disposed outside of the expansion structure.