The design of aerospace vehicles has required the solution of radically new scientific and technological problems. One of the important problems has been to create reusable heat shield materials. In [1, 2] information concerning the methods and results of solving these problems, including the development of composites from ultrathin quartz fibers and carbon-carbon materials for the “Buran” orbital vehicle heat shield, was presented. The basic thermophysical characteristics of these materials include both the rate or probability coefficients of heterogeneous nitrogen and oxygen atom recombination and the accommodation coefficients of energy recombination at high surface temperatures. In the present paper the experimental and computational aspects of determining these parameters, which are also of interest for new heat shield materials for future space transport systems, are discussed.

Experimental and Theoretical Simulation of Heterogeneous Catalysis in Aerothermochemistry (a Review)

: A method of solution of the laminar boundary layer equations for dissociating and ionizing air in chemical nonequilibrium is formulated for arbitrary pressure gradients and body geometry A nonsimilar, multistrip integral technique is employed in conjunction with previously derived transport and thermodynamic properties for the multicomponent mixture Several numerical examples are carried out for sharp conical bodies (assuming a fully catalytic cold wall) at reentry velocities and altitudes between 115 and 200 kilofeet The results are used to demonstrate a number of salient features of the flow fields; among these are the dominant role of diffusion in counterbalancing the production of dissociated and ionized species, the relative importance of accurate transport properties in the momentum and energy equations (as reflected in the species production), and the persistence of chemical nonequilibrium to relatively low altitudes (below 15 kilofeet) for slender, sharp vehicles at reentry velocities (Author)

Nonequilibrium, nonsimilar solutions of the laminar boundary layer equations (task 3.1. flow-field analyses. rest project),

It is shown that the heterogeneous recombination of nitrogen atoms on a catalytically active surface in a stream of dissociated air is accompanied by intense gas-phase recombination of the nitrogen in exchange reactions whose rate is determined by the rate of heterogeneous recombination of atomic oxygen.

On the recombination mechanism of atomic nitrogen near a catalytic surface in a stream of dissociated air

Within the framework of the theory of a hypersonic viscous shock layer a study is made of flow round wings of infinite span with blunt leading edges at various angles of attack and slip. Account is taken of multicomponent diffusion, and homogeneous chemical reactions, including dissociation-recombination reactions and exchange reactions. On the shock wave the generalized Rankine-Hugoniot conditions are given, and on the surface of the body conditions which allow for heterogeneous catalytic reactions of the first order with reaction rate constants depending [1] or not depending [2] on the temperature. The cases of an ideally catalytic and a noncatalytic surface are also considered. The surface of the body is assumed to be heatinsulated. A numerical study was made of the problem in a broad range of variation in the angles of attack and slip for different cases of prescribed constants representing the rates of the heterogeneous reactions. The conditions of the flow corresponded to the motion of a body which possess a lifting force along the trajectory of entry into the Earth's atmosphere [3]. The dependences are given of the equilibrium temperature of the surface along the stagnation line of the wing on the height of the flight and the distribution of this temperature along the surface of wings with parabolic and hyperbolic contours. It is shown that for flow regimes with a relatively high degree of dissociation in cases when the proportion of atoms recombined on the surface of the body is small, the dependences of the heat flow and the temperature of the surface on the angle of slip are of a nonmonotonic nature.

A hypersonic chemically nonequilibrium viscous shock layer oh wings with a catalytic surface

This paper gives the results of numerical calculations characterizing the effect of variation of the shock layer parameters on the heat transfer in the case of a multicomponent nonequilibrium-dissociating air on a wall with finite catalycity in the vicinity of the stagnation point of a spherical blunt body. Similar results for the case of a binary mixture can be found in [1–3]. It is shown that a consideration of the variation of the parameters in the nonequilibrium shock layer leads to a significant increase in heat flux to the noncatalytic wall in comparison with the theory of an asymptotically thin nonequilibrium boundary layer with equilibrium parameters on its outer boundary.

Nonequilibrium viscous flow of a multicomponent gas in the vicinity of the stagnation point of a blunt body

Results are presented of numerical calculations of a nonequilibrium laminar boundary layer on axisymmetric bodies whose surface has arbitrary catalytic activity using a proposed technique. In the published studies devoted to the exact numerical methods for calculating the boundary layer with chemical reactions, it is assumed that the surface of the body is either noncatalytic or has infinite catalytic activity [1], that thermochemical equilibrium exists at the surface [2], or that the temperature and composition of the gas at the surface are given [3, 4]. This problem has been examined in the approximate formulation in several papers, specifically [5].

Nonequilibrium laminar boundary layer of dissociating air on axisymmetric bodies

Article presents the results of the development, creation and research of a pulsed 3D-lidar, based on an 8x16 avalanche photodiodes (APD) array operating in the Geiger mode. Pixel size 30µ at fill factor 70%. Control electronics are integrated on the array. Measured time resolution is 0.5 ns. On the laboratory tests at a distance 5 - 10 m accuracy is 3 - 5 cm. The distance of operation was limited by laser pulse energy and efficiency of the receiving optical system. Such devices can have a wide range of possible applications, ranging from unmanned vehicles (UV) to space navigation, in particular, to ensure the safe landing of automatic spacecraft on the surface of planets.

V. G. Voronkin

Papers

Nonequilibrium laminar boundary layer of dissociating air on axisymmetric bodies

Development, creation and research of a laboratory model of a pulsed 3D-lidar based on the SPAD array