High Velocity Flight Research Articles

A Hypersonic Flow Effect on the Melting Rate of a Heat-Protective Surface under Degradation Conditions

The paper presents the results obtained for the distribution of heat flux incident upon a refractory plate of a hypersonic flight vehicle moving at space velocities at various distances from the Earth’s surface. The paper also provides the results of studying phase transitions in the near-wall boundary layer occurring during the hypersonic flow over the ablating surface. The effect of the catalytic wall on heat flux is analyzed. The emphasis is on the analysis of mass loss from the surface of high-velocity flight vehicles based on detailed consideration of the mechanism of heterogeneous catalytic reactions taking place under the surface mass transfer conditions. A temperature distribution is provided across the thickness of the boundary layer at the stagnation point of a blunt-nosed body with a refractory coating for a specific section of the flight path. The mass loss from the surface of crystalline refractory bodies is determined.

Investigation of the oxidative resistance of high-temperature coating on a SiC material under exposure to high-enthalpy flow

The method, procedure, and results of the investigation of a high-speed air plasma flow effect on the structure of an ultrahigh-temperature coating made for a composite silicon carbide material are considered. The coating is based on hafnium diboride, silicon carbide, and oxides of hafnium, yttrium, and zirconium. The effect of a high-speed plasma flow on the samples was studied in a VAT-104 wind tunnel (Central Aerohydrodynamic Institute); this facility enables simulation of the conditions of high-velocity flight in the upper atmosphere. During the tests, the main parameters of the plasma flow were recorded, and the temperature distribution of the sample was measured. The weight loss of the samples was determined. Using the results of numerical parametric simulation of flow past and heat transfer of the samples, the catalytic activity of the coating was determined. After testing in a high-enthalpy flow, X-ray diffraction analysis and X-ray phase analysis of the samples were performed, and their surface microstructure was analyzed.

Thermal and force loads on the vehicle surface in high-velocity motion in the earth’s atmosphere

Consideration has been given to a number of aspects of mathematical modeling of a high-velocity flight in the earth’s atmosphere in a wide range of variation of the determining parameters. Super-and hypersonic gas flow past flying vehicles has been investigated based on computer-aided calculations with allowance for its actual properties. Data on the distribution of gasdynamic parameters in the flow field, including thermal and force loads on the surface, have been obtained and analyzed. The issues of applying today’s information technologies to archiving scientific knowledge obtained in electronic databases of a specialized Internet center and their dissemination via the Global Network have been discussed.

L.A. Orbeli - Outstanding Physiologist and Science Leader of the Twentieth Century

L.A. Orbeli and his school developed new directions in physiology: evolutionary physiology, the theory of adaptational-trophic functions of the sympathetic nervous system, the theory of coordination of functions, and neuroendocrine regulations in the body. Orbeli enriched the study of the physiology of the cerebellum, the sensory organs, the kidneys, and the study of pain. His name is associated with the development of the foundation of physiology of extreme states (the physiology of deep-sea exploration, high altitude, and high velocity flight).

Influence of reentry turbulent plasma fluctuation on EM wave propagation

Electromagnetic wave propagation in turbulent plasma media during reentry is being investigated. Emphasis is placed on the effects of electron density fluctuations on electromagnetic wave propagation. The objective of this paper is to specify the source of noise in electromagnetic signal reception due to turbulence in the flow about a high velocity flight vehicle. A review of existing ground and flight test data is conducted, including electron density fluctuation measurements. Analytical algorithms deduced from first principles are being developed and validated with experimental measurements. A Navier–Stokes model, three-dimensional parabolized Navier–Stokes, and a coupled boundary-layer and inviscid flow codes are used to estimate the mean and variance of the electron density on the frustum and at the vehicle’s base region. Analytical and numerical solutions solving Maxwell’s equations and a commercial off the shelf code are used to estimate the phenomena of electromagnetic wave propagation in inhomogeneous plasma media. Results include the estimation of signal attenuation and phase shift induced by the mean electron density and by electron density fluctuations in the flowfield. Comparisons are made between the predictions and available data.

Damage threshold velocities for liquid impact

Rain erosion is a major cause of strength and transmission loss in IR ‘windows’ in high velocity flight. The Cavendish Laboratory's Multiple Impact Jet Apparatus (MIJA) is able to simulate high velocity rain impact accurately and reproducibly under laboratory conditions using a series of discrete water jets. Quantitative erosion data in the form of Damage Threshold Velocity (DTV) curves can be obtained, giving the lower limit of damage to the material under study. Damage threshold curves are presented for five different materials carried out using three different nozzle orifice diameters to create the impacting jet. Two approaches are made to predicting the DTV value for each specimen using only data from the standard 0.8 mm nozzle: (i) the ‘cylindrical jet’ approach, in which the impacting jet is considered to have a flat front, and (ii) the drop (‘round-fronted jet’) model. Both methods are found to give predictions well within the bounds of experimental error. The former predicts the damage threshold better when the smaller (0.6 mm) nozzle is used and the drop model the threshold when the larger (1.2 mm) nozzle is used. High-speed photographs of jets from differently-sized orifices are presented validating the use of models for the various nozzle diameters.

New area rules for penetrating impactors

Area rules are established for a high-velocity normal penetration of a sharp and undeformable impactor into a ductile target under a condition of a localized impactor-target interaction. An impactor with a polygonal form of cross sections and a three-dimensional impactor of a close shape with the same distribution of the cross-sectional area along the longitudinal axis are considered. It is shown that under some additional requirements the difference in the ballistic limits of these two impactors is of the order of ϵ 2 where ϵ is of the order of the difference in their shapes. The established area rule is valid also for the drag force applied to flying projectiles under a wide range of conditions of high velocity flight.

Aerospace erosion of diamond and diamond coatings

The erosive hazard experienced by diamond during high velocity flight has been investigated. Impact with rain drops is simulated using a high-velocity jet technique (the multiple-impact jet apparatus or MIJA) which allows threshold velocities for damage to be accurately determined. This technique has been used to assess natural and synthetic diamond (both chemical vapour deposited (CVD) and high-temperature, high-pressure (HTHP)), as well as CVD coatings on a range of IR-transparent substrates. The solid particle erosion hazard is assessed using a specially designed sand blasting rig which is capable of achieving velocities up to 250 m s −1. This apparatus has been used to study natural and CVD diamond and their erosion resistance is compared with that of currently used IR window materials. The results show that the superior mechanical properties of diamond make it an ideal candidate material for IR-transparent windows in an aerospace environment.

Mechanical Properties and Thermal Stability of Ti- and Al-Based Amorphous Wires Prepared by a Melt Extraction Method

The application of a melt extraction method to Ti- and Al-based alloys with highly reactive molten states was found to cause the formation of continuous amorphous alloy wires with good bending ductility. The wire diameter is in the range of 40 to 150 μm for Ti 40 Zr 10 Cu 50 and 40 to 100 μm for Al 85 Ni 10 Ce 5 and the difference reflects the difference in the glass-forming ability between both alloys. The glass transition temperature, crystallization temperature and heat of crystallization are 629 K, 691 K and 1.71 kJ/mol, respectively, for the Ti-based wire with the diameter of 100 μm and 530 K, 546 K and 0.37 kJ/mol for the Al-based wire with the diameter of 50 μm. The tensile strength is 2000 MPa for the former wire and 930 MPa for the latter wire. The thermal stability and mechanical strength are nearly the same as those for the melt-spun amorphous ribbons with the thickness of 15 μm. No appreciable concave resulting from the use of the copper wheel with a steep edge is seen in the cross section and the solidification is completed during the flight after extraction. The cooling rate of the Al-based wire with the diameter of 70 μm is estimated to be of the order 6 x 10 4 K/s. Thus, the formation of the amorphous alloy wires with a circular cross section is due to the rapid solidification of the fine supercooled liquid stream in the suppression of heterogeneous nucleation during the high-velocity flight in the argon atmosphere. The combination of the solidification process with high cooling rate and the good formability into the wire shape allows us to expect that the present process develops as an alternative method to produce amorphous alloy wires in various kinds of alloy systems including reactive elements as main components.

Tektites

Tektites are small, generally rounded, silicate glass bodies found in several widely separated areas of the Earth's surface called strewn fields. Four strewn fields are recognized: (1) Australasian, (2) Ivory Coast, (3) Czechoslovakian, and (4) North American. Tektites from the four known strewn fields were formed approximately 0.7, 1, 15 and 35 million years (m.y.) ago, respectively. Tektites are generally black, but those from Czechoslovakia and Georgia are translucent green or brown in color. Most tektites occur as splash forms, but some are blocky with a layered structure (Muong Nong-type); and some of the splash forms have been remelted or ablated by high velocity flight down through the Earth's atmosphere. Although they superficially resemble obsidian, they can be distinguished from obsidian by their petrography and compositions. Tektites, unlike obsidians, contain ubiquitous lechatelierite (SiO2 glass) particles and are generally completely devoid of microlites or crystallites. Tektites are drier than obsidians and have higher FeO/Fe2O3 ratios. Although some researchers favor a lunar volcanic origin for tektites, most of the chemical, isotopic, and petrographic studies seem to support a terrestrial impact origin. The presence of lechatelierite, coesite, shock relict inclusions, and Ni-Fe spherules favors an impact origin; and chemical and isotopic data indicate that the parent material was a terrestrial sedimentary deposit. The Czechoslovakian and Ivory Coast tektites have been associated with the Ries crater (in Germany) and the Bosumtwi crater (in Ghana), respectively.