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The translational effects of gas streams, which form after the triple-shock configurations at Mach reflection of blast waves with normal main shock (so-called stationary Mach configurations), were analyzed. Unlike in the case of an elevated explosions of fuel as rocket starts in initially stagnant air, which is considered here as a private case, it was supposed that this shock-wave structure moves in a preceding flow with arbitrary velocity (and corresponding flow Mach number). Analyzing relations of the dynamic pressures across the slipstream, which emanates from the triple point of the Mach reflection, it was shown that the flows after the triple-shock configuration usually differ much in their translational action on surrounding objects. It was found and discussed that some configurations drag the objects initially situated above and below the triple-point trajectory in opposite directions. Moreover, the "trigger" structure was found that remains previous flow drag action on the object above the triple-point trajectory, but switches it to exactly opposite one, if the object is situated below the triple point. • Triple-shock configurations appear at the internal blast inside of a spaceship. • They divide gas stream into two regions with very different velocity pressures. • Blast safety of an object aboard depends on its position above or below triple point. • Triple configurations are found with extreme drag force above or below the slipstream. • Some of them drag objects above and below the slipstream in opposite directions. [ABSTRACT FROM AUTHOR]

The theory of interaction of stationary gasodynamic discontinuities points to existence of Mach shock reflection with negative slope angle of the reflected shock. It forms in steady gas flows with large Mach numbers and small adiabatic index. Feasibility of such ("negative") triple-shock configurations, their stability and unambiguity of corresponding solutions seem traditionally doubtful. In the present study, conditions of existence and solution's unambiguity regarding "negative" configurations are analyzed. In addition, the possibilities of having other shock-wave structures, which can appear at the same parameters of supersonic steady flow and incident shock, are determined analytically. • Triple-shock structures with negative reflected shock slope angle are formally possible. • They appear at Mach reflection in high supersonic gas flows having small adiabatic index. • The feasibility and stability of observing such reflections in steady flows looks doubtful. • Solutions corresponding to Mach reflection with negative slope angle are ambiguous. • Regions of solution ambiguity and types of "alternatives" are found analytically. [ABSTRACT FROM AUTHOR]

The regular reflection of oblique steady and unsteady shocks in a perfect gas is considered. Non-monotonic variation of the mechanical and thermal loads on the obstacle with respect to shock/blast wave incidence angle is shown; the obstacle slope angles that correspond to pressure and temperature minima downwards of both steady and unsteady shock reflection point are determined analytically. Achieved minimization of dynamical and thermal loads at shock/blast wave reflection can be of use in space flight safety problems as blast safety onboard a spaceship, protection of spaceport facilities from blast of rocket carrier, prevention of fire onboard, and stable functioning of rocket engines, including ones based on detonation effects. • Regular reflection of steady and unsteady shocks is studied analytically. • General criteria of pressure and temperature extremums are derived. • Dynamic and thermal loads in shock reflection were optimized. • Damage in emergencies onboard space vehicle and outside it was minimized. [ABSTRACT FROM AUTHOR]

Relation between blast wave parameters resulted from a condensed high explosive (HE) charge detonation and a surrounding gas (air) pressure has been studied. Blast wave pressure and impulse differences at compression and rarefaction phases, which traditionally determine damage explosive effect, has been analyzed. An initial pressure effect on a post-explosion quasi-static component of the blast load has been investigated. The analysis is based on empirical relations between blast parameters and non-dimensional similarity criteria. The results can be directly applied to flying vehicle (aircraft or spacecraft) blast safety analysis. [ABSTRACT FROM AUTHOR]

A mathematical model for the interaction between a Prandtl–Meyer flow and a quasi-one-dimensional subsonic or supersonic stream is developed. The analytical description of the shape of the slipstream dividing two interacting streams is achieved, and its parametrical analysis is performed. The results of the study may be of practical use in supersonic jet flow–obstacle interaction analysis, which is important for the safety of space vehicle launches. [ABSTRACT FROM AUTHOR]

Abstract: The interaction between oblique shock and preceding expansion or compression Prandtl–Meyer wave of the same direction are studied theoretically. Two reliable analytical solutions for overtaking Prandtl–Meyer wave–oblique shock interaction were obtained. The criteria of reflected wave type change, shock inflection and degeneration, occurrence of subsonic flow pockets and influence of ratio of gas specific heats are established analytically. The results obtained can be used for the design of re-entry capsules, supersonic inlets, and supersonic nozzles, where wave interactions considered in the present paper take place. [Copyright &y& Elsevier]

Abstract: The mathematical model for two-dimensional (plane or axis-symmetric) over-expanded jet flow parameters analysis in the vicinity of supersonic nozzle lip is proposed. The variation of the key parameters of this problem (e.g., the geometrical curvature of oblique shock emanating from the nozzle edge) is studied parametrically depending of jet flow parameters, such as Mach number, jet incalculability, and the ratio of gas specific heats. It was proved that differential parameters of the flow field crucially depend not only of the key parameters, but on the symmetry type as well. [Copyright &y& Elsevier]

A robust blast inhibiting bin is the most often used device for damage blast effects suppression. In particular, a top open cylindrical bin significantly reduces a fragmentation effect resulted from a detonation of an explosive device placed inside the bin. However, reduction of blast wave overpressure and impulse by such cylindrical bins is not sufficient [1] . A reasonable alternative to endless increase of height and thickness of robust blast inhibiting bins is a development of destructible inhibitors having no solid elements in their structure and, therefore, excluding secondary fragmentation. So, the family of “Fountain” inhibitors [2,3] localizes and suppresses damaging blast effects due to multiphase working system. The present study is analyzing data obtained in testing of prototypes of new combined inhibitors. Their structure combines robust elements (bottoms, side surfaces) with elements responsible for blast loads reduction due to multi-phase working system (top and low transverse embeddings) and fairings impeding wave propagation in undesirable directions. [ABSTRACT FROM AUTHOR]

Laboratory modelling of active space experiments is described. To accelerate an impactor, a specially developed electromagnetic railgun capable of accelerating 10-mg cubic impactors to velocities of up to 5.5 km/s was used. As targets, different materials, such as ice and moon-like regolith, were employed. To simulate a collision with a comet, a hypervelocity impact on water ice targets with different densities was performed. To simulate an impact on the Moon's surface, a special method for preparation of regolith targets with the compositions corresponding to the Moon's surface materials was developed. The impact experiments with regoliths of different densities were carried out. [ABSTRACT FROM AUTHOR]

Physical details regarding base pressure low-frequency oscillations between rocket nozzles, their excitation and maintenance, are considered. Amplitude – frequency characteristics of these oscillations, as well as sequence of their type change, are studied. A single nozzle, a two-nozzle unit and a ring nozzle imitating multi-nozzle unit, are investigated in the present study. [ABSTRACT FROM AUTHOR]

Two-phase systems that involve gas-particle or gas-droplet flows are widely used in aerospace and power engineering. The problems of weakening and suppression of detonation during saturation of a gas or liquid flow with the array of solid particles are considered. The tasks, associated with the formation of particles arrays, dust lifting behind a travelling shock wave, ignition of particles in high-speed and high-temperature gas flows are adjoined to safety of space flight. The mathematical models of shock wave interaction with the array of solid particles are discussed, and numerical methods are briefly described. The numerical simulations of interaction between sub- and supersonic flows and an array of particles being in motionless state at the initial time are performed. Calculations are carried out taking into account the influence that the particles cause on the flow of carrier gas. The results obtained show that inert particles significantly weaken the shock waves up to their suppression, which can be used to enhance the explosion safety of spacecrafts. [ABSTRACT FROM AUTHOR]

The process of uranium stripping from tri- n -butyl phosphate by hydrofluoric acid solutions with the addition of hydrazine was investigated in the temperature range of 20 to 60 °C. Uranium was selectively precipitated in the form of a hydrazine uranyl fluoride complex when stripped from TBP by HF solutions with the addition of hydrazine. The uranium precipitation increased with increasing N 2 H 4 /U molar ratio in the range of 1 to 3 and with increasing holding time. Uranium tetrafluoride was obtained by the thermal decomposition of the hydrazine uranyl fluoride complex in a hydrogen stream. The uranium content in UF 4 is 76%. The obtained uranium tetrafluoride is a high-purity product and meets all requirements imposed on UF 4 at conversion plants. Thus, the stripping method provides a reduction of uranium processing operations to uranium tetrafluoride. [ABSTRACT FROM AUTHOR]