Impulse Transfer Research Articles

Optimization of MMX relative quasi-satellite transfer trajectories using primer vector theory

Quasi-satellite orbits (QSO) are stable retrograde parking orbits around Phobos that are currently being considered for JAXA’s upcoming robotic sample return mission Maritan Moons Exploration (MMX). During the proximity operations of MMX, the spacecraft inserted in a high altitude QSO will gradually descend to lower altitude QSOs with suitable transfer and station-keeping techniques between different relative QSOs. Preliminary analysis of two-impulsive planar transfers between relative retrograde orbits utilizing the bifurcated QSOs families is studied to estimate the ΔV costs and time of flights of the transfers. In this paper, differently from previous works, we utilize the initial guesses found through the preliminary results that provide two-impulsive transfer ΔV execution points and optimize the transfers between relative QSOs around Phobos. Primer vector theory is applied to investigate the primer vector of the MMX transfer trajectories to evaluate whether intermediate maneuver or initial/final coasting times along the trajectories can minimize the total ΔV cost between the transfers. Based on the primer vector analysis of the impulse transfer trajectories, it is found that departing and arriving at the same periphobian sides with an additional mid-course impulse results in the optimal impulse solution.

On the Impulse Response of Singular Discrete LTI Systems and Three Fourier Transform Pairs

A basic tenet of linear invariant systems is that they are sufficiently described by either the impulse response function or the frequency transfer function. This implies that we can always obtain one from the other. However, when the transfer function contains uncanceled poles, the impulse function cannot be obtained by the standard inverse Fourier transform method. Specifically, when the input consists of a uniform train of pulses and the output sequence has a finite duration, the transfer function contains multiple poles on the unit cycle. We show how the impulse function can be obtained from the frequency transfer function for such marginally stable systems. We discuss three interesting discrete Fourier transform pairs that are used in demonstrating the equivalence of the impulse response and transfer functions for such systems. The Fourier transform pairs can be used to yield various trigonometric sums involving sin⁡πk/Nsin⁡πLk/N, where k is the integer summing variable and N is a multiple of integer L.

Mirror-Image Pain Update: Complex Interactions Between Central and Peripheral Mechanisms.

The appearance of contralateral effects after unilateral injury has been shown in various experimental pain models, as well as in clinics. They consist of a diversity of phenomena in contralateral peripheral nerves, sensory ganglia, or spinal cord: from structural changes and altered gene or protein expression to functional consequences such as the development of mirror-image pain (MP). Although MP is a well-documented phenomenon, the exact molecular mechanism underlying the induction and maintenance of mirror-like spread of pain is still an unresolved challenge. MP has generally been explained by central sensitization mechanisms leading to facilitation of pain impulse transfer through neural connections between the two sides of the central nervous system. On the contrary, the peripheral nervous system (PNS) was usually regarded unlikely to evoke such a symmetrical phenomenon. However, recent findings provided evidence that events in the PNS could play a significant role in MP induction. This manuscript provides an updated and comprehensive synthesis of the MP phenomenon and summarizes the available data on the mechanisms. A more detailed focus is placed on reported evidence for peripheral mechanisms behind the MP phenomenon, which were not reviewed up to now.

Energy exchange mechanism between blast wave and expansion tube

The mechanical response and energy absorption characteristics of the energy-absorbing structure under blast loading are widely concerned in engineering protection, while the energy exchange mechanism remains poorly understood, thereby limiting improvements in energy absorption performance under blast loading. This paper utilizes the expansion tube structure (ETS) as a typical energy-absorbing structure to investigate the energy exchange mechanism under blast loading. Following an experimental verification, numerical simulations are conducted to investigate the effect of relevant parameters on the energy exchange characteristics. A theoretical model based on the strong-shock hypothesis is developed and validated against numerical results to predict the energy absorption efficiency of ETS under blast loading. The findings reveal that increasing the areal density of ETS positively impacts impulse transfer, but does not contribute significantly to energy exchange between the blast wave and ETS. Notably, there exists a significant negative correlation between the energy exchange efficiency and areal density. An approximately linear positive correlation is observed between the energy exchange efficiency and both peak overpressure and specific impulse of the reflected wave due to an enhanced reflection coefficient of the blast wave. Moreover, increasing equivalent strength leads to a decrease in energy exchange efficiency as it negatively correlates with effective impulse of the reflected wave. This study elucidates the underlying mechanisms governing energy exchange in expansion tube under blast loading, providing valuable insights for optimizing designs of energy-absorbing structures.

Integral equations of the second kind in dynamic analysis of nonlinear systems with a finite number of degrees of freedom under arbitrary dynamic loading and material dependencies

Introduction. Development of computational methods for nonlinear systems possesses a significant potential, considering that linear theory sometimes fails to accurately describe the properties of dynamic systems, and the linear approximation gives only a very rough idea of real processes for a number of cases.Aim. Calculating linear systems and deriving the resulting equations for nonlinear systems involves impulse response and transfer functions of linear “generating” systems of differential equations. Such an approach in comparison with the traditional method of the so-called normal forms enables the calculation algorithm to be simplified considerably, avoiding several stages and presenting the solution by means of the normal mode method for linear systems directly with respect to the generalized coordinates.Materials and methods. The paper presents a method and an algorithm developed for the calculation of nonlinear systems with a finite number of degrees of freedom under arbitrary dynamic loading and material nonlinearity. Systems of nonlinear differential equations were reduced to nonlinear integral equations of the second kind, considered as resulting equations. The solution was developed in time steps, the value of which, among other things, determines the accuracy of the solution and the nature of the computational algorithm.Results. The paper presents main computational dependencies in a generalized form, convenient for numerical simulation. The author provides solutions for a nonlinear system with one degree of freedom and a cubic reactiondisplacement relation, as well as for a system with one and two degrees of freedom with a viscous damper. In both cases, the developed solution contains all properties of nonlinear systems, including the jump (transition) from the upper ascending branch to the lower, stable one, and the associated excitation of free oscillations.Conclusions. According to the calculations, the occurrence of nonlinear effects in oscillating systems makes positive impact on their behavior, in resonant modes in particular.

Effect of Double Impulse Trajectory Transfer from Earth to Mars Mission

The interplanetary mission from Earth to Mars takes at minimum energy launch opportunity with a single impulse transfer. Due to some unavoidable circumstances, if the launch takes at a later date, other than the minimum energy launch opportunity then the energy requirement increases. Also if the terminal states, approach the condition of opposition, the energy requirements rapidly increase and become infeasible too, resulting in restrictions on the launch window. This is due to the relative inclinations of the two planets. To overcome this situation, the possibility of applying an intermediatory impulse between the two terminals, named as double or two impulse transfers is considered. This paper gives the necessary details for the double impulse transfer and draw attention to its advantages.

Study on the impulse mechanism of optical films formed by laser plasma shock waves

Abstract In a high-power laser system, when the surface pressure of the optical film caused by laser plasma shock wave is greater than the adhesion per unit area of the film layer, the film will produce mechanical damage, and in serious cases, the whole system may not work. Therefore, studying the formation mechanism of optical film surface pressure and impulse caused by laser plasma shock wave is the key to ensure the normal operation of the high-power laser system. In this article, by studying the relaxation process of laser plasma shock wave on the surface pressure of optical film, and using the time accumulation effect of various pressures on the surface of the optical film, the calculation model of impulse on the optical film’s surface formed by laser plasma shock waves was established, and the variation rules of the impulse I st {I}_{\text{st}} and impulse coefficient j j on the unit area of single-layer Al2O3 and HfO2 optical films with different parameters were obtained. When the incident laser wavelength λ \lambda was 1,064 nm, the energy E E was 0.1 J 0.1\hspace{.1em}\text{J} , the pulse width t p {t}_{\text{p}} was 10 ns 10\hspace{.25em}\text{ns} , the focal length of the focusing lens f f was 350 mm 350\hspace{.25em}\text{mm} , the distance between the film surface and the focal plane of the focusing lens z 0 {z}_{0} was 5 mm 5\hspace{.5em}\text{mm} , and the film radius R R was 5 mm 5\hspace{.5em}\text{mm} , the calculation and simulation results show that the impulse I st {I}_{\text{st}} of the two films was 1 0 − 4 N s 1{0}^{-4}\hspace{.5em}\text{N}\hspace{.5em}\text{s} order of magnitude, the impulse coefficient j of the two films was 1 0 − 5 N s/J 1{0}^{-5}\hspace{.5em}\text{N}\hspace{.5em}\text{s/J} , the Al2O3 film with small atomic number will obtain larger I st {I}_{\text{st}} and j j , I st {I}_{\text{st}} and j j of the two films increase with the increase of E E and f f , and I st {I}_{\text{st}} and j j of the two films decrease with the increase of z 0 {z}_{0} and t p {t}_{\text{p}} . In the total impulse transfer time ( t 0 {t}_{0} ), I st {I}_{\text{st}} and j j both increase with the increase of R R .

Active space debris removal by ion multi-beam shepherd spacecraft

Contactless transportation of a passive object by an ion beam generated by an active spacecraft's thruster is a promising way of space debris removal. The study proposes a modification of the ion beam shepherd concept using an array of impulse transfer thrusters. The multi-beam scheme provides significant increase the generated ion force, which reduces a space debris object deorbit time, thereby reducing the probability of its collision with other orbital objects. The aim of the work is to study the possibility of using several ion beams for effective contactless transportation of a space debris object. Controlling the angular motion of the object permits orientation of the object to maximize the generated ion force. The article proposes a control law for impulse transfer thrusters, which is based on the calculation of the energy of the object's unperturbed motion, and two control schemes that implement this law: (1) relay control, which implies turning the thruster on and off, and (2) ion beam axis direction control for one of the thrusters. For a space debris object of a cylindrical shape, a comparison of the time and fuel costs required for deorbiting the object using one, two, and three impulse transfer thrusters is made. It is shown that the addition of thrusters significantly reduces the descent time, but has little effect on the mass of required fuel. For the case of two engines, the best angle of ion beams axes direction and the most preferable angular motion mode are determined. Numerical simulation of space debris removal is carried out for the case when the space debris object is in the least favorable mode of angular motion and the proposed control schemes are used. The ion beam direction control scheme showed better results than the relay scheme. The use of multiple ion beams opens up new possibilities for creating new ion beam shepherd spacecraft design and developing new control methods and laws.

Impulse Transfer Matrix of a Time-Varying System of Differential-Algebraic Equations

Impulse Transfer Matrix of a Time-Varying System of Differential-Algebraic Equations

The Damage and Impulse Transfer Characteristics of Flexible Steel V-Structures with Large Bend Radii

This paper reports results from an experimental and computational study on the influence of bend radius and internal angle on the damage and impulse transfer characteristics of flexible steel V-structures subjected to localized explosion loading. This issue has bearing on the manufacturing of V-hulls used for Mine Resistant Ambush Protected vehicles used around the world. Global impulse transfer, damage and transient deformation were measured during small-scale explosive detonations on 1:8-scale V-structures. The work found that increasing the bend radius to values that can be used in practical manufacturing generated damage that was less localized than the damage observed in V-structures with tighter bend radii. High-speed imaging was able to measure transient deformation that was maximal in the centre, and lower elastic post-peak vibration magnitudes at high charge masses. The impulse transfer increased as the bend radius increased and the internal V-angle increased. Since V-structures with tighter bend radii exhibit less permanent deformation and higher deformation gradients, they will be more prone to localized ruptures when deployed for blast protection, whereas structures with larger tip radii will need a larger region of the V-structure repaired after a blast event but may be less prone to rupturing when the blast loading is localized.

Impulse Transfer Matrix of a Time-Varying System of Differential-Algebraic Equations

A range of issues related to the impulse transfer matrix of a system of linear differential-algebraic equations is considered. For systems with infinitely differentiable coefficients, it is shown that this matrix can be represented as the sum of the impulse transfer matrices of its differential and algebraic subsystems. A form of a nondegenerate change of variables is found, which does not affect the form of the impulse transfer matrix. It is proposed to search for realizations of this matrix in the class of differential-algebraic equations of index 1 with separated differential and algebraic components. Necessary and sufficient conditions for the realizability of an impulse transfer matrix in the class of algebraic systems are obtained. The problem of construction methods and the dimension of minimal realizations of such a matrix is discussed under various assumptions.

Large inelastic response of polyurea-coated steel plates to confined blast loading

The large inelastic deformation performance of monolithic steel and polyurea–steel laminate plates to confined blast loading is investigated through a combination of experiments and finite-element modelling. Emphasis is placed on elucidating how the location of the polyurea coating(s) and steel substrate, relative to the direction of loading, affects their inelastic deformation and the impulse and energy transfer to the laminate plates. Experimental results show that monolithic steel plate outperforms – using the maximum central deflection as a criterion – its equivalent polyurea–steel laminate of equal mass in confined blasts. Results from finite element simulations, which will be shown to be in good agreement with the experiments, will reveal that a longer response time for the polyurea–steel laminate attributes to the greater saturation impulse and, in turn, the increased deformation over its monolithic counterpart of equal mass. The internal energy of a laminate plate, unlike its monolithic equivalent, is found to increase even after reaching its maximum central displacement through further out-of-plane deformation that spreads out laterally. The impedance mismatch between the elastomer and steel will be shown to play a key role in the amplification, or attenuation, of the blast wave depending on the placement of the elastomer. A parametric study is performed to elucidate the influence of thickness ratio and mass per unit area on the blast performance of the laminate plates.

The 21st Century Systems: An Updated Vision of Continuous-Time Fractional Models

This paper presents the continuous-time fractional linear systems and their main properties. Two particular classes of models are introduced: the fractional autoregressive-moving average type and the tempered linear system. For both classes, the computations of the impulse response, transfer function, and frequency response are discussed. It is shown that such systems can have integer and fractional components. From the integer component we deduce the stability. The fractional order component is always stable. The initial-condition problem is analyzed and it is verified that it depends on the structure of the system. For a correct definition and backward compatibility with classic systems, suitable fractional derivatives are also introduced. The Grünwald-Letnikov and Liouville derivatives, as well as the corresponding tempered versions, are formulated.

Temporal analysis of the heavy metal concentration in road sediment and dust using statistical models

The objective of this paper is to show a temporal analysis using autoregressive integrated moving average models of the heavy metal concentration in road sediment and dust of Soacha, a Colombian locality. The representative size fractions in the road sediment and dust were <250 μm and ⩽10 μm, respectively. The results suggest that lead is the best metallic element to study the relationship between the heavy metal concentration in the road sediment and dust (r-Pearson = 0.90). Univariate models (R2 ⩾ 0.58) suggest that the time series of lead concentrations in road sediment and dust have the same temporal structure. Namely, because they are first-order autoregressive processes, concentrations at a given moment of time are influenced by the immediately preceding concentrations. The transfer function model (R2 = 0.91) suggests that there is no delay in impulse transfer from road dust concentration to lead concentration in the road sediment. The effect is immediate for a sampling interval of 3 days. The results show that modeling has a better fit during the rainy season compared to the dry season. In the context of the simulation of physical phenomena in engineering, this study is relevant to deepen knowledge in relation to the use of autoregressive integrated moving average models.

Attempts to improve on the V‐hull structural design for air‐blast loading applications

AbstractMine resistant ambush protected vehicles often use mono‐V structures in the design of their hulls for blast protection purposes. These hulls deflect blast waves laterally in the event of a landmine detonation directly beneath the vehicle. Lower internal angles offer greater deflection capability, reducing the impulse transfer to the vehicles, but at the cost of increased ride height. This paper reports results of attempts to improve on V‐hull structural designs for air‐blast loading applications, where scaled blast tests are performed to evaluate the designs in terms of structural deformation, rupture and impulse transfer characteristics. Structures with double V and W profiles are compared to mono V structures with a 120° internal angle, such that the proposed designs do not increase the ride height. Results showed that the double V‐structures limit the central deformation, but some designs have severe deformation at the interface of the central V plate and the shallow base angle structure. W structures seem to be susceptible to rupture at low charge masses. There is no single answer to improved blast protection of vehicle hulls, as design choices must be driven by the anticipated threat range, the important performance metrics and other operational considerations.

Transfer between libration orbits through the outer branches of manifolds for Phobos exploration

The transfer between libration orbits in the Mars–Phobos system is challenging under the strong gravitational perturbation of Mars and Phobos. In this paper, the outer branches of manifolds of libration orbits around Phobos are employed for impulse and continuous thrust transfer between orbits, respectively. The 1:1 resonant orbits are found to be appropriate intermediate orbits for impulse transfer, which can connect the manifolds of various kinds of libration orbits. For the continuous thrust transfer, the convex optimization method is adopted to design the low-thrust trajectory in the three-body problem. The Poincaré section is established to find the best matching points on the outer manifolds. The L1/L2 homoclinic and L1−L2 heteroclinic transfer trajectories are designed and discussed. The simulations show the feasibility of the transfer by outer manifolds with both impulse and continuous thrust. The proposed method can avoid the potential hazard caused by the complicated dynamics near Phobos and provide a reliable transfer method, which can be used in future Phobos exploration missions.

The effect of explosive charge backing in close-proximity air-blast loading

This paper presents new insights into the influence of explosive charge backing on the impulse transfer and transient response characteristics of plates subjected to close-proximity air blast loading. The results of the combine experimental and computational studies show the critical influence of charge backing, which caused between a 3-5 times increase in the impulse transfer when the charge was metal-backed. The permanent deflections from the metal-backed detonations were larger than for air, but not to the same degree as the impulse increase. These findings demonstrate the important influence of charge backing, in close proximity detonations, which greatly exceeded anything previously measured. These valuable insights will assist blast protection engineers considering the effects of explosions in situations when the charge backing is something other than air, which is a frequent occurrence in explosion scenarios.

ДИФФЕРЕНЦИАЛЬНЫЕ УРАВНЕНИЯ ТРОГАНИЯ ПОЕЗДА С УПРУГИМИ СВЯЗЯМИ

The starting mode for the train is the most difficult. An effective method of pulling is the selection of coupling clearances. In this case, the cars are set in motion sequentially and the inert mass, as well as the static friction force immediately at the moment of starting, are minimal. This method has two significant drawbacks - a small fixed value of the gaps in the couplings and the shock nature of the impulse transfer. These disadvantages can be avoided by using elastically deformable couplings. The aim of this work is to construct a mathematical model of "easy" starting of a train with elastic couplings. The softening of the train start-off mode is essentially due to the replacement of the simultaneous start-off of the sections with alternate ones. To exclude longitudinal vibrations of the composition, after reaching the maximum tension of the coupling, the possibility of its harmonic compression should be mechanically blocked.

Feeling the heat: source-sink mismatch as a mechanism underlying the failure of thermal tolerance.

A mechanistic explanation for the tolerance limits of animals at high temperatures is still missing, but one potential target for thermal failure is the electrical signaling off cells and tissues. With this in mind, here I review the effects of high temperature on the electrical excitability of heart, muscle and nerves, and refine a hypothesis regarding high temperature-induced failure of electrical excitation and signal transfer [the temperature-dependent deterioration of electrical excitability (TDEE) hypothesis]. A central tenet of the hypothesis is temperature-dependent mismatch between the depolarizing ion current (i.e. source) of the signaling cell and the repolarizing ion current (i.e. sink) of the receiving cell, which prevents the generation of action potentials (APs) in the latter. A source-sink mismatch can develop in heart, muscles and nerves at high temperatures owing to opposite effects of temperature on source and sink currents. AP propagation is more likely to fail at the sites of structural discontinuities, including electrically coupled cells, synapses and branching points of nerves and muscle, which impose an increased demand of inward current. At these sites, temperature-induced source-sink mismatch can reduce AP frequency, resulting in low-pass filtering or a complete block of signal transmission. In principle, this hypothesis can explain a number of heat-induced effects, including reduced heart rate, reduced synaptic transmission between neurons and reduced impulse transfer from neurons to muscles. The hypothesis is equally valid for ectothermic and endothermic animals, and for both aquatic and terrestrial species. Importantly, the hypothesis is strictly mechanistic and lends itself to experimental falsification.

Design and Testing of a Double-Sided Ion Thruster for Ion-Beam Shepherd

The ion-beam shepherd (IBS) space debris removal method requires two thrusters: one for impulse transfer (IT) and one for impulse compensation (IC). This paper proposes a novel thruster concept for the IBS-type missions where a single double-sided thruster (DST) simultaneously producing ion beams for the IT and IC purposes is used. The advantage of the DST design is that it requires approximately half the radio-frequency power compared with two single-ended thrusters, and it has a much simpler subsystem architecture, lower cost, and lower total mass. Such a DST thruster was designed, built, and tested. During the experimental campaign, a successful extraction of two ion beams from a single discharge chamber was achieved. The paper shows that it is possible to control the thrust magnitudes from the IT and IC thruster sides by altering screen/accel grid voltages, radio-frequency generator power, and mass flow rate. This is achieved by designing the IT and IC ion optics geometries to be different. It is demonstrated that the IC side can produce 30% more thrust compared with the IT side, proving that the DST concept is a viable alternative for the IBS-type space debris removal missions.