[en] Use of materials that are subject to impact requires knowledge of their mechanical response to high-rate loading. Gas guns provide high impact velocities conveniently. A 2-in. (50.8-mm) gun (TIG) that provides 25- to 125-m/s impact velocities was designed and installed. One can test sheet specimens in uniaxial or biaxial tension at strain rates as high as 6000/s and can determine deformation distributions and fracture strains. At these rates, stress-wave propagation makes load measurement impossible. Special furnace designs permit testing at temperatures as high as 1500⁰C. The TIG was used to test noble-metal alloys for space nuclear power systems. One established the deformation and fracture behavior of Ir-0.3%W and Pt-30%Rh-8%W alloys at strain rates as high as 6000/s and temperatures as high as 1440⁰C. Simulated components of potential space nuclear power systems also were impact tested in several systems