GAS DYNAMIC ASPECTS OF AN ENCLOSED HYPEONIC TEST TRACK

The gas dynamics related to the movement of a track-guided test vehicle through an evacuated tube are considered preliminarily. Values of pressure, temperature, density, and drag are computed for perfect piston action and for partial piston action at speeds up to the hypersonic. The effects of gas imperfections, viscosity, and wave reflection are explored. The limiting conditions at which a body in a tube ceases to behave like a piston are defined. At the lower limit of piston action, pressures, temperatures, and densities ahead of the vehicle are the same as for a flat-faced body in free air, and skin friction effects along the tube wall are negligible. At the upper limit of piston action, pressures in frictionless air range from about 44 greater above Mach 8.0 to more than 80 greater below Mach 2.0 than at the lower limit of piston action, and drag and heating due to friction pre dominate over shock effects frictional heating in particular becomes large. The relative effects of piston action as compared to flow in free air are greater at low Mach numbers than at high Mach numbers. Pressures are ample at all speeds for effective braking by piston action, but high temperatures exist at all but the lowest speeds.