Arkhipov P. A., Bulat P. V., Dudnikov S. Yu., Kuznetsov P. N.
For transport unmanned aerial vehicles, selecting propulsion characteristics is a key consideration. A distinction must be made between lift propulsors, which must provide sufficient thrust within limited dimensions, and cruise propulsors, which primarily require high efficiency in both hover and forward flight. The results of developing a numerical simulation methodology for isolated propellers and ducted fans are presented, including the selection of turbulence models under conditions of a potential laminar-turbulent transition. The studied objects include K184V propellers and VK1 ducted fans, developed at the Central Aerohydrodynamic Institute (TsAGI) for hovercraft propulsion systems. The one-equation Spalart-Allmaras model and two-equation models based on k-ε and k-ω variables are investigated. The turbulence models are verified against benchmark data to account for the laminar-turbulent transition and the presence of separation bubbles on the blade and duct surfaces. One method for dividing the flow region into laminar, turbulent, and transitional zones is introducing the intermittency parameter γ into the turbulence model equations, where γ is equal to unity in fully developed turbulent flow and zero in laminar flow. The Langtry-Menter k-ω SST Reθ-γ transition model is one such turbulence model that uses the intermittency parameter and accounts for the laminar flow region effect. A geometric multigrid method is used to solve the difference equations. The numerical simulation yields pressure and velocity fields both in the computational domain and directly on the blade and duct surfaces, allowing the determination of aerodynamic characteristics of the ducted fan under various operating conditions. For hover and forward-flight conditions, the calculated dependencies of thrust and power coefficients, as well as propulsive efficiency, are obtained for a wide range of rotational speeds and engine power inputs. The results are compared with benchmark experimental data from TsAGI. Accounting for the laminar-turbulent transition and the associated formation of thin laminar separation bubbles significantly improves the agreement between the computational results and experimental data.
Nilov A. S., Butorina I. A., Mokhova E. A.
Methods are presented for calculating the geometric parameters of evolving porous media in composite materials (CMs) produced via various gas-phase technologies with common multi-directional and randomly reinforced structures. An analytical calculation of porous media geometric parameters was performed for both multi-directional (2D, 3D, 4D, and 5D) structures, consisting of continuous fiber elements idealized as straight cylindrical rods (or fiber bundles) with circular cross-sections, and randomly reinforced composites based on discrete fiber fillers. The random structure of such porous media is approximated as a regular structure formed by a system of cylindrical rods. Models of porous preforms (aligned and randomly reinforced) and corresponding composites are proposed, alongside methods for describing the CM structure during the simulation of gas-phase infiltration of fibrous preforms for carbon-carbon and ceramic-matrix materials. Key parameters of the evolving porous media were determined, including initial, instantaneous [current], and ultimate values for porosity, specific surface area, and reinforcing fiber radii. The proposed calculation methods serve as structural description elements for developing software to simulate isothermal and thermal-gradient chemical vapor infiltration of fibrous preforms to produce carbon-carbon and ceramic-matrix composites with minimal or specified porosity. This methodology is applicable as a computational component for modeling and determining the thermal conductivity of the considered structures. Furthermore, the initial porosity calculations can be used to optimize the liquid-phase infiltration of porous preforms in the manufacturing of CM components.
Gusev D. V., Rasulov Z. N., Remsheva A. E.
Development and experimental validation of a novel technology for fabricating polymer composite coatings (PCCs) intended for load-bearing and drive assemblies of aerospace systems are presented. The relevance of the study is driven by the need to increase the service life and reliability of components operating under high dynamic, vibratory, and impact loads, exposure to aggressive environments, wide temperature ranges, and strict weight constraints. The coating material is based on an epoxy matrix modified with antifriction and reinforcing components, ensuring wear resistance, corrosion protection, a low coefficient of friction, and damping properties. A two-stage PCC deposition process is proposed using a custom automated deposition system that ensures structural uniformity of the coating, thickness repeatability, and optimal orientation of the modifying phases. Laboratory tribological tests were conducted on a custom-built tribometer, and full-scale tests were performed on a dynamic load test rig utilizing a roller-on-wheel configuration simulating real operating conditions. Finite element analysis of contact stresses and dynamic loads in friction units was carried out using ANSYS and SolidWorks Simulation, enabling the prediction of coating performance under various service conditions. The results show that the developed coatings provide a coefficient of friction of 0,0015–0,008, reduce vibration amplitude by 20–30 %, withstand more than 100,000 load cycles without degradation, and significantly increase corrosion resistance compared with metallic and conventionally used protective coatings. The findings confirm the feasibility of practical application of the proposed technology in the development of highly efficient damping and antifriction units for aerospace systems, as well as for heavy-duty ground and marine equipment.
Rychkova A. D.
With the rapid expansion of CubeSat small satellite constellations, the problem of anthropogenic contamination of near-Earth space is becoming increasingly relevant. Current international standards and space agency initiatives are tightening the requirements for the post-mission disposal timelines of end-of-life spacecraft. This necessitates developing structures that combine high operational performance with controlled disposal capabilities after the end of operational life. A computational and analytical justification for applying an aramid fiber-reinforced polymer composite in the load-bearing structure of a 12U CubeSat is presented. A three-layer wall configuration with a total thickness of 2.0–3.0 mm is proposed, comprising an outer layer modified with silica or alumina nanoparticles, a primary load-bearing layer with an epoxy matrix, and an inner trigger layer designed to initiate structural fragmentation upon mission completion. To assess structural durability, a mathematical model of atomic oxygen linear erosion has been developed, based on data from the SPENVIS orbital environment database, the MET-V 2.0 and IRI2001 atmospheric models, and post-flight data from the LDEF and MISSE missions. Structural analysis was performed using the Tsai-Wu failure criterion, which accounts for composite anisotropy and the combined effects of space environment factors, including thermal cycling, radiation exposure, moisture absorption, and manufacturing defects. A system of structural knockdown factors was introduced, with the total knockdown factor KΣ taken as 0.62. Erosion calculations indicate that thickness recession over a five-year period amounts to 0.160 mm at an altitude of 500 km and 0.559 mm at 400 km. It was established that structural integrity is maintained with an initial wall thickness of at least 2.5 mm, while the factor of safety according to the Tsai-Wu criterion ranges from 1.24 to 1.48. The aramid-epoxy composite enables a 25–32 % reduction in structural mass, accounting for design constraints, compared to the V95 aluminum alloy. Economic assessment indicates that, despite the increased production cost of the composite bus, the cumulative economic benefit resulting from increased allowable payload mass and the reduced volume of active deorbiting systems amounts to 928,000–1,036,000 rubles. The results confirm the potential technical and economic feasibility of applying polymer matrix composites in CubeSat structures, provided that reliability requirements and international standards are met.
Vashchenko А. N., Grigoriev M. N.
Development of civil unmanned aerial vehicles (UAVs) during the first quarter of the 21st century is analyzed. Particular attention is paid to electric propulsion in aircraft designed for passenger transportation in urban environments, in accordance with the Low Altitude Economy (LAE) development program. Potential capabilities and practical steps of leading innovative entities in the People’s Republic of China aimed at achieving global leadership in the LAE sector by 2030 are examined, thereby ensuring a dominant role in the formation of a new global techno-economic paradigm. Activities of EHang, a private company that became the first in the world to receive a production certificate for serial production of vertical take-off and landing (VTOL) UAVs for urban air mobility (UAM), often-though somewhat inaccurately-referred to as unmanned air taxis, are analyzed in detail. Design evolution is traced from the Ghost quadcopter (the world’s first lightweight smartphone-controlled UAV) to the production single-seat EHang 116 and two-seat EHang 216 models. Technical specifications of all UAVs mentioned are presented and evaluated. Time stages of the formation of unmanned aviation for domestic air mobility in China are identified at a systemic level. The role of the Government of the People’s Republic of China and relevant state authorities in the development and manufacturing organization of unmanned systems for UAM is reflected. Potential for international cooperation between the Russian Federation and the People’s Republic of China in local air mobility using unmanned transport is considered. Specifically, at the initial stage of interaction, the possibility of conducting joint R&D between the Ustinov Baltic State Technical University “VOENMEH” (Russia) and the recently established Joint Institute for Low Altitude Aviation Technology (JILAAT) (China) is proposed, aiming at the redesign of the EH216-S multicopter into a flying stretcher for rescue operations.
Andryushkin A. Yu., Kazakova A. O., Romanat N. I.
Concealment of aircraft at basing locations through camouflage is a relevant problem. Precision-guided munitions (cruise missiles, guided bombs, and unmanned aerial vehicles) are widely used to engage aircraft at their basing locations. Precision-guided munitions strike aircraft at basing locations with a probability of 0.5 or higher. The signatures of aircraft at basing locations are examined. Ensuring aircraft survivability against precision-guided munitions of the attacking side by means of various camouflage measures is relevant. Increasing aircraft survivability at basing locations is achieved through camouflage in the optical, radar, and thermal bands. “Active” and “passive” camouflage measures are distinguished. The first group includes measures that affect detection and targeting systems, as well as munitions. The second group includes measures that reduce the signatures of the concealed aircraft. A methodology is proposed for assessing the survivability of an aircraft concealed by various camouflage measures at a basing location under the impact of precision-guided munitions of the threat source. The methodology accounts for the use of both “active” and “passive” camouflage measures, including aerosol dispersion, decoys, mock-ups, radar-absorbent
coatings, camouflage nets, light discipline, and others. The proposed methodology accounts for the probability of aircraft detection under specific weather conditions during reconnaissance, the probability of a munition hitting the aircraft, and the probability of munition interception. The effectiveness of each camouflage measure is characterized by a quantitative metric, and the cumulative metric for the combined use of several measures equals the sum of their individual metrics. Using the developed methodology, the survivability of an aircraft concealed by “active” and “passive” camouflage at a basing location under the impact of precision-guided munitions was calculated. The calculation results demonstrate the practical value of the developed methodology. Preservation of aircraft at basing locations through camouflage and concealment from reconnaissance assets significantly affects the effectiveness of combat operations.
Baranov I. Ya., Koptev A. V.
Over 1 million tons of depleted UF6 (tails) containing up to 0.3 % of 235UF6 have been accumulated in Russia. Tails represent a high-purity and cost-intensive product from which extracting the remaining 0.3 % of 235UF6 is currently economically unviable. These tails can be utilized for nuclear fuel production to generate high profit and resolve storage issues. However, separating depleted UF6 via gas centrifuges doubles the nuclear fuel cost, rendering this method practically unused. Low-cost laser isotope separation (LIS) with dimer formation suppression in a free jet via multiphoton excitation is well-studied and utilized for light and medium-mass molecules. But low-cost laser separation of heavy molecules remains unrealized. The multiphoton dissociation (MPD) method requires over 45 photons at a 16 μm wavelength per UF6 molecule, with a laser efficiency of 0.5 % and a pulse intensity of 108 W/cm2. Experimental realization of UF6 molecule excitation is highly complicated by the absence of lasers whose emission lines coincide with the center of the 235UF6 vibrational absorption band. The application of UV lasers is hindered by high costs and low efficiency. As for IR radiation, it can be generated either with an efficiency not exceeding 0.5%, or via para-hydrogen Raman lasers providing an average power of 100 W at a 2 % efficiency; however, this approach involves substantial technical difficulties. An enhancement of the laser method with van der Waals dimer formation suppression in a free jet is proposed for separating depleted UF6 by placing the molecules inside the cavity of a mode-locked CO laser with a power under 1 kW and a 30 % efficiency for nuclear fuel production. The dimer binding energy is tens of times lower than the UF6 dissociation energy, and a CO laser radiation intensity of approximately 105 W/cm2 is sufficient for molecular excitation without requiring high power. The use of a single photon to separate one 235UF6 molecule is proposed, enabling the processing of accumulated tails into nuclear fuel via a mode-locked CO laser more efficiently than by centrifuges. This approach yields high returns and environmental benefits by eliminating natural uranium mining, transportation, processing, and fluorination, while resolving the tails storage problem.
Tazba A. M., Shevchik A. A., Aleksandrov A. A.
Navigation satellite signals play a key role in determining the spatial position of moving objects and in refining the outputs of inertial navigation systems. In recent years, it has become increasingly necessary to solve motion control problems under conditions of weak or unstable navigation satellite signals. Unstable signals from navigation satellites can be caused by natural and artificial interference, environmental factors such as dense urban environments, powerful electromagnetic sources such as power lines, and other factors. The historical development of navigation systems, which contributes in particular to improving the quality of the navigation solution, involves a progressive increase in the degree of integration between inertial and satellite navigation systems. Loosely coupled, tightly coupled, and ultra-tightly coupled navigation systems have long been successfully used in practice. The problem of deep integration of inertial and satellite navigation systems to improve the quality of the navigation solution under interference is considered. The feasibility of a linear navigation filter for a correction system that is invariant to vehicle motion is demonstrated, on the basis of which a computationally distributed, deeply integrated radio-inertial-satellite navigation system can be built. The block diagram of a computationally distributed, deeply integrated radio-inertial-satellite navigation system is presented, and a list of parameters that must additionally be supplied by the GNSS receiver to the navigation filter, compared to existing solutions, is defined. A method for high-rate conversion of raw radio navigation observables in the GNSS receiver software is proposed. A model for reference signal errors is proposed, including the variable and constant phase components as well as the frequency of the reference signals. Formulas for calculating estimation of pseudorange, pseudorange rate, and pseudorange acceleration are derived for generating corrections in the filter, which should, among other things, improve the quality of the navigation solution obtained from satellite observations under conditions of unstable satellite signals.
Sinitsyn V. A., Ivanov A. V., Sinitsyn E. A.
Research results are presented on substantiating the structure of transmitting and receiving channels for a multichannel two-coordinate primary coherent radar with multiple identical N-inputs and M-outputs of the MTx-NRx type. The radar utilizes continuous periodic linear frequency-modulated probing signals to detect and measure the polar coordinates of low-observable [low-RCS] targets in the short-range surrounding air and ground space. The advantages and design features of multichannel Multiple Input Multiple Output (MIMO) radars are noted, including modular design, low radiated power, low probability of intercept [LPI] operation, and the use of orthogonal probing signals emitted by the transmitting channels and reflected radar signals received by the receiving channels, as well as mobility, low weight, and compact dimensions. It is shown that the carrier frequency of an azimuthal multichannel two-coordinate coherent radar is determined by the partial beamwidth of a virtual fan-shaped transmit-receive radiation pattern in azimuth and the size of the azimuthal virtual aperture, considering its excess over a given maximum physical horizontal antenna aperture. It is noted that the number of transmitting (M) and receiving (N) channels of an azimuthal multichannel MIMO-type two-coordinate radar is determined by the required number of high-frequency transmitting radiators and receiving antenna elements. This configuration must ensure the formation of a virtual M×N-beam transmit-receive fan radiation pattern covering the operational zone in azimuth and elevation with a specified azimuthal resolution. A configuration for the mutual arrangement of M = 8 transmitting radiators and N = 8 receiving high-frequency antenna elements within the physical aperture of a multichannel transmit-receive antenna array, limited to a width of 1 m, is proposed. This variant provides the formation of an extended virtual aperture with a fan-shaped azimuthal transmit-receive radiation pattern in the radar coverage area, defined by a spatial sector of 60° in azimuth and 20° in elevation. It is shown that the proposed 8Tx-8Rx multichannel two-coordinate radar, emitting orthogonal probing signals at a carrier frequency of 15 GHz in the Ku-band via a 1-meter-wide planar antenna array with 10 mW of power per each of the 8 transmitting channels, ensures the detection and measurement of the polar coordinates of low-observable targets. For unmanned aerial vehicles with radar cross-sections of 0.01 m² and 0.1 m², detection is achieved at maximum ranges of 2.9 and 4.4 km, respectively (with an observation time of 1 s), and 5.1 and 7.6 km (with an observation time of 5 s).
Gessen P. A., Lizin A. I., Pavlova V. A., Saenko V. D., Tupikov V. A.
Matching images acquired from different sensing modalities, in particular infrared and visible-spectrum imaging, with three-dimensional geometric models of a scene is highly challenging because of fundamental differences in the physical mechanisms of data formation. This problem is particularly relevant to unmanned aerial vehicle (UAV) navigation, where information from heterogeneous onboard sensors must be fused to ensure reliable positioning and orientation. Modern UAVs are often equipped with visible-spectrum optical cameras, thermal imagers, and LiDAR systems, creating a need for efficient cross-modal matching algorithms. In this study, a modality is understood as a specific type of acquired information (in particular, RGB images, infrared imagery, and depth maps), and each of these types captures specific scene characteristics: texture features, thermal field distributions, surface reflectance properties, or the spatial geometry of objects. Since each sensing modality produces a fundamentally different set of features-textural, thermal, reflectance-related, or geometric-direct correspondence estimation between heterogeneous modalities is a nontrivial research problem. A methodological approach based on transforming multimodal data into a unified depth space, treated as an invariant representation of the scene, is proposed. By recovering depth information from source images of different modalities or mapping them to a common spatial geometric structure, cross-modal discrepancies can be reduced and correspondence estimation between heterogeneous data types can be substantially simplified. This approach can be applied in autonomous UAV navigation systems, where accurate and robust matching of multisensor information is important for safe mission execution. The architecture of the developed method is described in detail, the results of experimental validation of its performance and effectiveness on real multispectral datasets are presented, and the identified limitations of the proposed approach are critically analyzed together with a discussion of promising directions for its further improvement and development.