Modeling trans- and supersonic viscid flow over a cone on a ballistic range

The possibilities of ballistic-range experimentation in determining the influence of compressibility and viscosity on the flow over cone-shaped parts of flying vehicles are considered. A nonmonotonic character of the dependence of the near wake flow over cone on the Reynolds number is revealed, which is an important factor under natural flight conditions. Tests have been performed for a right circular cone with a half-angle of 15°. The drag coefficients (C _x ) for acute and blunt cones with an aspect ratio of L/D = 1 at a zero attack angle have been determined. Near wake flow parameters (base pressure p _b and base density ρ _b ) have been experimentally studied in a range of Mach numbers M_∞ = 0.5?4 and at a fixed value of M_∞ = 2.3, but with Reynolds numbers Re_∞D varied from 6 × 10⁴ to 1.5 × 10⁶.     

Hydrolysis of Tc(CO) 6 + cation in aqueous solutions. Crystal and molecular structures of the identified products: Tc2(CO)10 and Tc3H3(CO)12

Hexacarbonyltechnetium(I) cation undergoes rapid hydrolysis in aqueous solutions at pH ≥ 7 with the formation of an unidentified carbonyl compound or mixture of compounds in the form of a pale yellow precipitate. Two crystalline fractions were isolated in the course of vacuum sublimation of the precipitate and were identified by single crystal X-ray diffraction as Tc₂(CO)₁₀ and Tc₃H₃(CO)₁₂. The crystal and molecular structures of these compounds were described. The mechanism of their formation in the course of hydrolysis of [Tc(CO)₆]⁺ cation is discussed.     

An analysis of the efficiency gained with replacement of the traditional lining of bell and chamber metallurgical furnaces by lining made of refractory ceramic fiber

In theory, there exist two methods of replacement of traditional lining made of fireclay insulation articles by lining made of OKB Cerablanket refractory ceramic fiber. The first method consists in production of lining made of OKB Cerablanket rolled material with the material being formed in undulating fashion into sections with height of a wave equal to the thickness of the lining. In the second method, the lining is fabricated from ready-made modular Z-blok sections with integrated anchors made of stainless steel. Sections fabricated from OKB Cerablanket rolled material is arranged in a linear or checkerboard arrangement. The operating life of lining fabricated from refractory fiber is practically unlimited. Anumber of conditions that guarantee long and effective service of the materials must be fulfilled, for example, the furnace temperature must not exceed 1170°C, rate of gas flow must not be greater than 20 – 30 m/sec, and the lining must not be subjected to mechanical loads.     

Complexation of Tricarbonyltechnetium(I) Ion with Halide and Thiocyanate Ions in Aqueous Solution: 9 9Tc NMR Study

Complexation of the Tc(CO)₃(H₂O)₃ ⁺ ion with halide (F^-, Cl^-, Br^-, I^-) and thiocyanate ions in aqueous solutions was studied by ^{9 9}Tc NMR spectroscopy. The stability constants of the mono-, di-, and tri- substituted complexes were calculated. The stability of halide (Cl^-, Br^-, I^-) complexes grows as the ionic radius of the halogen increases and its electronegativity decreases. For halide complexes of similar composi- tion, the ^{9 9}Tc chemical shift correlates with the stability of the complexes. The fluoride ion, most probably, does not coordinate with the Tc(CO)₃ ⁺ ion, in contrast to its close analog, hydroxide ion. Among the ligands studied, the pseudohalide anion NCS^- forms the most stable complexes with the Tc(CO)₃ ⁺ ion.     

Effect of Low Temperatures on Mechanical and Physical Properties of High-Strength Nickel Alloy ÉK61-ID and Stainless Maraging Steel ÉK49-VD

Physical and mechanical properties of high-strength nickel alloy ÉK61-ID and stainless maraging steel ÉK49-VD with reduced carbon content, which are used for fabrication of metallic seals of detachable joints (DJ) of re-usable liquid-propellant engines (LPE), are studied at cryogenic temperatures (20 – 293 K). Tests of DJ simulators with seals from these materials and subsequent field tests of LPE confirm the high operational properties of the structures.