I. Introduction

Gasdynamic facilities with heavy free pistons were constructed in TsNIIMASH in the late 1950s by Rachmatulline.1 The principal objective for their construction was the reproduction of real flight conditions of hypersonic ballistic vehicular flows at M ? 20, Re _L ? 10 ⁷ 10 ⁸ and flow velocities of V _? ? 8 km/s for several seconds using scaled models. To achieve these values, a store of air (with a volume ~ 0.1 m ³ at temperatures of T ₀ ? 6000 K or higher, pressures of P ₀ ? 5000 atm, and total enthalpies of h ₀ ? 20 MJ/kg within the plenum) was required. Optimistic predictions on the possibility of achieving these values by adiabatic, isentropic compression and production of the hypersonic test flows with a duration of several seconds in the large U-11 facility and in the facilities of other countries, which were built between 1950 1960, did not materialize. The reasons for that situation were the lack of an adequate theory for real gas phenomena2 ^, 3 when those facilities were built, the problem of heat protection of the plenum chamber elements, and others. Even now, these problems are far from a complete solution.

The development of piston units in TsNIIMASH centers on their application to solving particular problems connected to spacecraft development in the...