Combined electro-discharge launcher working on hydrogen

The light-gas gun (LGG) is a standard tool for achieving high velocities. Its performance depends on the sound speed of a working gas, determined by its molecular weight and operational temperature. High temperature can be achieved by either adiabatic compression of the gas, or by electric arc heating. For high performance, the first requires seriously high pressure (more than 2000 MPa). The second has to heat the working gas to several thousands of degrees Kelvin, which can cause thermal erosion of launcher elements. We report new progress on a combined launcher, which employs a powder charge for first-stage adiabatic compression of a working gas, and subsequent electric arc heating. This operational mode provides higher system efficiency, and also reduced maximum gas temperature and pressure. A new model for the combined launcher, with improved mechanical strength and optical measurement windows, is described. Experiments employed a range of conditions: 10-15 MPa initial working gas pressure, 150-200 MPa predischarge pressure, maximum pulse pressure up to 500 MPa, and discharge currents of 300-500 kA at rates of dl/dt ∼10¹⁰A/s. Our best ballistic results were 2.5 km/s for a 7.5 gm projectile, and 4.2 km/s for a 1.7 gm projectile. Characteristics of electric discharge at hydrogen concentrations of (1.5-3.3)×10²²cm^-3, and other test data, are presented.