Modeling the angular motion dynamics of spacecraft with a magnetic attitude control system based on experimental studies and dynamic similarity

The problem of spacecraft attitude control using electromagnetic systems interacting with the Earth’s magnetic field is considered. A set of dimensionless parameters has been formed to investigate the spacecraft orientation regimes based on dynamically similar models. The results of experimental studies of small spacecraft with a magnetic attitude control system can be extrapolated to the in-orbit spacecraft motion control regimes by using the methods of the dimensional and similarity theory.     

Spectral Characteristics of an Oblique-Incidence Reflection Interferometer as a Refractive Index Sensor

Optics and Spectroscopy - A sensor of refractive index of analytical liquid operating in the Kretschmann geometry and based on an oblique-incidence reflection interferometer (RI) is simulated for...     

Modeling the Angular Motion Dynamics of Small Spacecraft with a Magnetic Attitude Control System in a Three-Axis Stabilization Mode

Doklady Physics - The problem of modeling the attitude control modes of small spacecraft using electromagnetic systems interacting with the Earth’s magnetic field is considered. A...     

Atomistic simulation of the interaction between mobile edge dislocations and radiation-induced defects in Fe-Ni-Cr austenitic alloys

The classical molecular dynamics method is employed to simulate the interaction of edge dislocations with interstitial Frank loops (2 and 5 nm in diameter) in the Fe-Ni₁₀-Cr₂₀ model alloy at the temperatures T = 300–900 K. The examined Frank loops are typical extended radiation-induced defects in austenitic steels adapted to nuclear reactors, while the chosen triple alloy (Fe-Ni₁₀-Cr₂₀) has the alloying element concentration maximally resembling these steels. The dislocation-defect interaction mechanisms are ascertained and classified, and their comparison with the previously published data concerning screw dislocations is carried out. The detachment stress needed for a dislocation to overcome the defect acting as an obstacle is calculated depending on the material temperature, defect size, and interaction geometry. It is revealed that edge dislocations more efficiently absorb small loops than screw ones. It is demonstrated that, in the case of small loops, the number of reactions accompanied by loop absorption increases with temperature upon interaction with both edge and screw dislocations. It is established that Frank loops are stronger obstacles to the movement of screw dislocations than to the movement of edge ones.     

Interpretation and Simulation of Negative Ion Mass Spectra of Some Phosphorus Organoelement Compounds

Negative ion mass spectra for a series of organophosphorus compounds were obtained and negative ion fragmentation processes were treated theoretically. Using O-isopropyl and O-pinacolyl methylphosphonofluoridates as examples, electron affinities of molecules and their fragments were estimated using the UB3LYP/6-311+G(d,p) quantum-chemical approach and energetically more favorable and characteristic routes of dissociative electron attachment, including simple bond cleavage and rearrangements, were determined. Based on the obtained experimental and theoretical data, hypothetic fragmentation patterns were proposed and a special algorithm was compiled to predict negative ion mass spectra for some groups of organophosphorus compounds, such as О-alkyl methylphosphonofluoridates, О,О-alkyl phosphonodichloridates, and О,О′-dialkyl phosphonochloridates. The simulated mass spectra showed a good agreement with the experimental ones, confirming reasonable reliability of the proposed algorithm.     

Optimization of Steel-Surface Hardening by Carbon Nanostructures Followed by Treatment with High-Intensity Energy Sources

The effect whereby a steel surface is modified by its covering with a nanocarbon material followed by fast electron- or laser-beam irradiation is studied. The initial material is low-carbon steel. Soot produced via the thermal sputtering of graphite electrodes in an electric arc with the subsequent extraction of fullerenes is used as the nanocarbon coating. Due to the fact that nanocarbon-coated samples are irradiated with a 60-keV electron beam, the material microhardness enhances considerably. The dependence between the microhardness and the irradiation energy is nonmonotonic and reaches its maximum (about 600 ± 20 HV) under the condition that the electron-irradiation energy is 460 J/cm² and the intensity is 1.53 kW/cm². This corresponds to a fourfold increase in the microhardness. Electron-beam irradiation of the treated surface is accompanied by a 1.5–2-fold decrease in the friction coefficient. Experimental results are compared with data obtained under laser irradiation of the nanocarbon-coated steel surface.