High Impulse Research Articles

Dielectric properties of hafnium oxide film prepared by HiPIMS at different O2/Ar ratios and their influences on TFT performance

High-k hafnium oxide (HfO2) film was prepared by high power impulse magnetron sputtering (HiPIMS). The influences of oxygen supply on the plasma state, film properties and TFT performance were investigated. The films are near-stoichiometric and preferentially (−1 1 1)-orientated. When the oxygen supply increased from 1% to 3%, the excitation/ionization rate of the plasma species increased, leading to higher crystallinity, higher density, and lower oxygen vacancy defect concentration of the film, therefore improving the dielectric properties of the film. When the oxygen supply further increased to 5%, the excitation/ionization rate decreased, thereby leading to lower crystallinity, lower density, and higher oxygen vacancy defect concentration of the film, therefore deteriorating the dielectric properties of the film. The film deposited at 3% oxygen supply exhibited the best dielectric properties with the highest k value of 24 and the highest breakdown-electric field (4.7 MV/cm), which should be attributed to the high crystallinity, high density and low oxygen vacancy defect concentration of the film. Finally, transparent thin film transistors (TFTs) with ITO gate electrode, HfO2 gate dielectric layer and indium-gallium-zinc oxide channel were fabricated on flexible colorless polyimide substrate at full room temperature by all HiPIMS process. The fixed positive charges and k value of HfO2 film have significant effects on the TFT performance. The best TFT exhibited good electrical performance, featuring a remarkably low subthreshold swing of 0.13 V/decade. It also exhibited fair stability against bending and gate bias stress.

Monoethanolamine-Based Fuels Hypergolic with Rocket-Grade Hydrogen Peroxide

The object of this work is to study the ignition performances of promising catalytically promoted amino-based green fuels to be used in combination with rocket-grade hydrogen peroxide. The main hypergolic parameter, the ignition delay time, was experimentally determined with an automated drop test setup. Additionally, the kinematic viscosity was experimentally measured, while the CEA2 software was used to determine the ideal rocket performances of the propellants. Three inorganic copper salts were selected as catalysts to be used in combination with monoethanolamine in concentrations ranging from 0.5 wt% to 20 wt%. Then, N,N-dimethylethylenediamine was introduced as part of a blend with monoethanolamine to target the high viscosity and low gravimetric specific impulse of the fuel for the pure monoethanolamine case. Due to the reduced monoethanolamine and low additive content, some formulations were observed to be characterized by gravimetric specific impulse higher than 320 s, and kinematic viscosity lower than 5 cSt while retaining ignition delay times shorter than 30 ms with 98 wt% HTP. Finally, the addition of ethanol to the blend was preliminarily investigated to improve the additive solubility. The effects on the ignition delay time were found to depend on the concentration ratio of the two amines.

Materials’ properties of low temperature deposited Cu/W and Cu/Cr multilayer thin films using high power impulse magnetron sputtering

In this study, copper/tungsten (Cu/W) and copper/chromium (Cu/Cr) multilayers were created by stacking bilayer films in a 3:1 ratio, with layer thicknesses ranging from 400 to 800 nm, deposited on Si (100) substrates using high power impulse magnetron sputtering (HiPIMS). The microstructural and surface properties of these films were examined through x-ray diffraction, atomic force microscopy, and scanning electron microscopy. Electrical properties were assessed using a four-point probe, while mechanical properties were measured via nanoindentation. Both multilayer systems showed a decrease in the hardness accompanied by an increase in the elastic modulus with each stacking bilayer. The Cu/W system experienced a gradual hardness reduction (down to 19%), compared to the Cu/Cr system, which exhibited a similar decrease (14.5%). The Cu/W and Cu/Cr multilayer film samples consistently demonstrate a softer nature compared to their bilayer counterparts due to the influence of the underlying Cu soft layers. A distinctive surface smoothness in these multilayer systems correlates with the elastic modulus in a manner unlike that with hardness. These multilayer films also demonstrated altered electrical resistivity, enhancing our understanding and capabilities in fabricating films with an increased number of layers.

Anisotropic dielectric dispersions and thermal behaviors in highly textured BN thin films for heat self-dissipating electronics

Mainstream high-k gate materials, such as SiO2, Al2O3, and HfZrO2, are in demand for modern electronics. However, these dielectrics possess lower thermal conductivity, significantly limiting thermal dissipation in electronic devices. Herein, we propose the utilization of complementary metal-oxide semiconductor- (CMOS) compatible high power impulse magnetron sputtering (HiPIMS) for the mass production of highly textured hexagonal boron nitride (h-BN) on (100)-, (110)-, and (111)-oriented SrTiO3 substrates. The as-prepared films exhibit distinct vertical alignments, as evidenced by HRTEM and FTIR analysis. Notably, the R value, ranging from 0.46 to 0.50, is associated with the stress in the film. Importantly, distinct anisotropies in thermal conductivity, dielectric constant, and optical band gap are observed. Furthermore, the values of thermal conductivity in these highly textured h-BN films are 4.5, 5.7, and 5.3 Wm−1K−1, which is almost three times larger than those of SiO2 (1.4 Wm−1K−1) and Al2O3 (1.35 Wm−1K−1), and even an order of magnitude larger than that of HfZrO2 (0.67 Wm−1K−1). The combination of excellent dielectric characteristics, favorable thermal conductivity, and superior stability over a broad temperature range makes this novel material outperform conventional dielectric gate materials in high-power electronics applications.

Fabrication of (TiZrNbSiMo)1-xNx high entropy alloy coatings using a high power impulse magnetron sputtering technique: Effects of nitrogen addition

Due to the outstanding mechanical and physical properties of high entropy alloy (HEA) coatings, the global academic and industrial communities have made significant research efforts in recent years, aiming to expand their industrial applications. In this study, TiZrNbSiMo and (TiZrNbSiMo)1-xNx HEA nitride coatings with different nitrogen contents were fabricated using a high power impulse magnetron sputtering (HiPIMS) system. By varying the nitrogen flow rates, the nitrogen contents of coatings increased from 0 to 48.8 at. %. The deposition rate decreased with increasing nitrogen content due to the target poisoning effect. Very fine and dense microstructure can be seen for each coating. The amorphous structure was obtained as the nitrogen content was lower than 19.1 at.%, whereas a nanocrystalline FCC structure was formed when the nitrogen content reached 34.9 at. %. Furthermore, the corrosion resistance of TiZrNbSiMo and four TiZrNbSiMoN HEA coatings in 0.5 M H2SO4 aqueous solution were superior to uncoated 304 stainless steel. We can conclude that the nanocrystalline TiZrNbSiMoN HEA coatings with a nitrogen content of 34.9 at. % exhibited a high hardness of 15.6 GPa, an electrical resistivity of 766.5 μΩ·cm, and an excellent corrosion polarization resistance of 9.71 × 105 Ω·cm2, 610.7 times higher than 304SS. This study provides valuable insights for future promising applications of (TiZrNbSiMo)1-xNx HEA nitride coatings in severely corrosive environments, such as the protective coatings on stainless steel bipolar plates in proton exchange membrane fuel cells.

Cognitive Impulsivity in Anorexia Nervosa in Correlation with Eating and Obsessive Symptoms: A Comparison with Healthy Controls.

Impulsivity in eating disorders (ED) has been historically focused on bingeing-purging symptoms, evidencing lower levels in restricting subtypes. In the recent literature, obsessive-compulsive disorder (OCD) has been described as characterized by high cognitive impulsivity. This specific impulsivity factor has been rarely studied in anorexia nervosa (AN). In this study, 53 inpatients with anorexia nervosa and 59 healthy controls completed the following questionnaires: the Barratt Impulsiveness Scale (BIS-11), the Obsessive-Compulsive Inventory (OCI), the Eating Disorders Inventory-2 (EDI-2), the State-Trait Anxiety Inventory (STAI), and the Beck Depression Inventory (BDI). AN individuals showed significantly increased levels of cognitive instability but no difference in global score and other subscales of impulsivity compared to the healthy controls. Among AN individuals, cognitive instability emerged as being associated with the global score and obsession subscale of the OCI. It was also significantly associated with interoceptive awareness and impulse regulation. Cognitive instability was the main predictor of obsessive thoughts and behaviors in AN. Our study supports the hypothesis of AN as being characterized by high cognitive instability and adds the result that the cognitive domain of impulsivity may be associated with the presence of obsessive symptoms, specifically obsessive thoughts.

Simulation of liquid cone formation on the tip apex of indium field emission electric propulsion thrusters

Field emission electric propulsion (FEEP) thrusters possess excellent characteristics, such as high specific impulse, low power requirements, compact size and precise pointing capabilities, making them ideal propulsion devices for micro-nano satellites. However, the detection of certain aspects, such as the evolution process of the liquid cone and the physical quantities at the cone apex, proves challenging due to the minute size of the needle tip and the vacuum environment in which they operate. Consequently, this paper introduces a computational fluid dynamics (CFD) model to gain insight into the formation process of the liquid cone on the tip apex of indium FEEP. The CFD model is based on electrohydrodynamic (EHD) equations and the volume of fluid (VOF) method. The entire cone formation process can be divided into three stages, and the time-dependent characteristics of the physical quantities at the cone apex are investigated. The influences of film thickness, apex radius size and applied voltage are compared. The results indicate a gradual increase in the values of electrostatic stress and surface tension stress at the cone apex over an initial period, followed by a rapid escalation within a short duration. Apex configurations featuring a small radius, thick film and high voltage exhibit a propensity for liquid cone formation, and the cone growth time decreases as the film thickness increases. Moreover, some unstable behavior is observed during the cone formation process.

A Wideband Circularly Polarized Antenna With High Impulse Signal Fidelity for IR-UWB Positioning Applications

A Wideband Circularly Polarized Antenna With High Impulse Signal Fidelity for IR-UWB Positioning Applications

A man stitches his mouth in the context of a personality disorder

IntroductionA 28 year old patient will be presented. This paramilitary man was brought to the Emergency Room due to an autolytic attempt with Benzodiazepines, along with a mouth suture, in the context of a soon to be resolved problematic ankle osteosynthesis procedure. The patient claimed to be suffering pain, furthermore struggling due to the fact he could not be working due to his ankle issue. Language barrier was a problem during the interview.ObjectivesThe objetives of this case is to try to explain the issues that may arise in patients with personality disorders in the context of an autolytic attemptMethodsThis patient will be presented, along with systematic bibliography review of the topic.ResultsThe following results were extracted upon the attention given to this patient which was admitted to the Psychiatric Unit.First of all, the mouth stitches were removed, along with a petition for toxicological analysis. The results gave positive for cannabis and benzodiazepines. The patient was also brought previously this year with another autolytic attempt, this time on cocaine consumption too. Furthermore, a thorough review was made of the other autolytic attempts, including those which happened in his country of origin. The patient has hundreds of small cuts among his arms, from previews cuts made in the past. Furthermore, subcutaneous wounds were auto inflicted in the ER, with a small blade.Among the whole interview, it was clear he had a personality disorder, with high impulsivity levels and lack of control once the situation overflows.We also tried to understand the outcome of suturing his mouth. The patient referred his acts of impulsiveness due to his overwhelming situation of both having no job at this moment and the pain he was suffering due to his ankle procedure.The patient was admitted to our Unit due to the high risk he could repeat this act. Upon arrival, the same day he was admitted, the patient asked if he had to stay at the unit. When explaining the following already told event, furthermore insisting in the possibility of been evaluated by the Traumatology team, he proceeded to try and hang himself with his medical-hospital clothing.The patient was treated with antipsychotics. Along with Lormetazepam at night. At the end of the hospitalization, and after been evaluated by the Psychiatrist of this Unit, the patient was also treated with Lithium due to its effectiveness in the treatment of autolytic attempts.ConclusionsPersonality disorders are one of the psychiatric pathologies that prevail with greater frequency in autolytic attempts 1. Additionally, it should be taken into account the possible ongoing consumption of psychoactive drugs that could also derive in psychopathological decompensation. On top of the following, the use of antipsychotic treatment is indicated for the managing of conduction altercations 2, besides Lithium being a great option in managing suicidal temptations 3.Disclosure of InterestNone Declared

Patterns of Internet Addiction in an Italian sample: 100% of the sample experience Nomophobia

Introduction Internet Addiction Disorder, a concept introduced for the first time by Ivan Goldberg in 1995, is one of the most recently identified forms of addiction, but already considered a real psychosocial phenomenon, capable of having a profound impact on different aspects of social and psychological life of individuals. One of its most recently identified manifestations is Nomophobia, a neologism formed from the combination of terms such as “no mobile”, “phone” and “phobia”, which can be understood as the fear of feeling disconnected. It is today considered a situational phobia, characteristic of contemporary times. The most common symptoms include excessive cell phone use and constant anxiety at the thought of losing the internet connection. Others are, for example, “Ringxiety”, ringing anxiety, or the “phantom vibration syndrome”.ObjectivesThis study aims to examine the spread of Nomophobia in the Italian population, evaluating psychopathological correlations that can explain its diffusion.Methods Between January and May 2023, an anonymous online questionnaire was randomly sent to the general population. Alongside with tests to evaluate psycho-social features, the instrument used to study Nomophobia was the Nomophobia Questionnaire (NMP-Q) (Yildrim et al. Comput Hum Behav. 2015; 49:130–7), in its Italian version (Adawi et al. JMIR MHealth UHealth. 2018;6:e24).ResultsThe sample consists of 308 people (189 F, 119 M), with an average age of 32 years (sd 14). In our sample, 100% of the subjects tested positive for Nomophobia. Values indicating a state of severe Nomophobia are found in 12.3% of the sample (F 15.9%, M 6.7%). The young population, between 18 and 25 years old, represents 54% of the affected population, but more than 60% of severe cases (95% confidence interval 50-65%). The severe cases correlate positively (p<0,05) with findings of high impulsiveness. There are no other studies that investigate the psychopathological correlates of Nomophobia among Italians.ConclusionsDespite possible biases, the data obtained are an alarming sign of the spread of internet addiction that characterizes our times, of which the excessive use of cell phones in the form of Nomophobia is an expression. Despite their now undisputed usefulness, mobile devices are capable of causing the onset of serious health problems, starting from exposure to radiation capable of causing dermatitis, tumors, and infertility. Furthermore, they dramatically interfere with driving safety, becoming a major cause of road accidents. Considering these consequences, it appears to be extremely important to characterize the phenomenon, as well as its psychosocial determinants, in order to proceed with its better definition and prevention.Disclosure of InterestNone Declared

Interactions between anxiety and impulsive dimensions are differentially associated with experiential avoidance

Anxiety and impulsivity often co-occur, but due to broad conceptualizations of impulsive behavior, it remains unclear whether anxiety could be positively associated with global impulsivity or specific facets of impulsivity. Negative urgency, or rash behavior that specifically occurs during negative emotional states, may provide common ground to examine the overlap between high anxiety and high impulsivity. Limited work has examined relationships between negative urgency and behavioral processes that are often associated with both anxiety and global impulsivity, such as experiential avoidance. In this study, we examined self-report data collected from a non-clinical sample of adult participants (n = 589) to test relationships between anxiety and experiential avoidance through both negative urgency and global impulsivity. Contrary to hypotheses, we found that negative urgency alone did not alter the relationship between anxiety and experiential avoidance. However, follow-up analyses including data-driven factors of impulsivity revealed that in combination, anxiety and both emotion-based impulsivity (i.e. negative and positive urgency) and hyperactivity were linked to greater experiential avoidance. By contrast, anxiety and non-planning were associated with lower experiential avoidance. These results provide targets for future studies to examine individual differences in profiles of co-occurring anxiety and impulsivity.

Uncontrolled eating is associated with higher impulsiveness, risk taking and novelty-seeking

Previous studies suggest that trait disinhibition as measured by the Three Factor eating Questionnaire (TFEQ) is related to selected measures of impulsivity and risk taking. However, the factor validity of the original trait disinhibition measure has been questioned, and a revised scale of uncontrolled eating consequently developed. To date few studies have revisited the relationship between impulsivity and the uncontrolled and emotional eating scales of the revised TFEQ. In the present study, 283 participants (208 women) completed the revised TFEQ alongside a battery of measures of impulsivity and risk taking in an online study. The total and all subscale scores on the Barratt Impulsiveness Scale were significantly associated with scores on the uncontrolled, but not emotional or restrained, TFEQ scale. Likewise, risky behaviour indexed by the average number of pumps per trial on the Balloon Analogue Risk Task were also associated with uncontrolled, but not emotional or restrained, eating, and the same pattern of associations were also found for the novelty, but not intensity, subscales of the Arnetts Inventory of Sensation Seeking. Overall these data suggest that uncontrolled eating is related to wider personality traits of risky decision making, novelty seeking and wider cognitive impulsivity, which may in turn increase of future weight gain.

Adhesive properties of deposited Cu films on colorless polyimide using high power impulse magnetron sputtering system

This study explores the deposition of copper (Cu) films onto colorless polyimides (PIs) using the High Power Impulse Magnetron Sputtering (HiPIMS) technique. The impact of varying operating duty cycles and frequencies on sheet resistance, the deposition rate of Cu films, and the adhesion strength between Cu and PI is examined. Adjusting the HiPIMS parameters aims to achieve superior film quality with reduced sheet resistance. Furthermore, post-thermal treatment significantly improves the adhesion of the Cu layer to the PI substrate due to the mechanical interlocking mechanism created by the surface roughness of the PI and the chemical bonding between the two components.

Effects of titanium and boron alloying with non-equimolar AlCrNbSiTi high entropy alloy nitride coatings

Among various fabrication technologies for high entropy alloy coatings, high power impulse magnetron sputtering (HiPIMS) technologies have been utilized to synthesize dense microstructure and high hardness coatings with enhanced mechanical and chemical properties. Mid-frequency (MF) pulses have been introduced in the off-time of HiPIMS pulses of the superimposed HiPIMS-MF system to improve the deposition rate. In this study, AlCrNbSiTiBN coatings were deposited using a superimposed HiPIMS-MF system connected to an Al4Cr2NbSiTi2 high entropy alloy target and a direct current (DC) power source for TiB2 target in a reactive Ar and N2 gas mixture. The DC power of the TiB2 target was varied to increase the titanium and boron contents. With increasing Ti and B contents, the microstructure transforms from loose granular and crystalline structure to denser and refined nanocrystalline phases. A residual stress-free coating with a B content of 4.2 at.%. and a hardness of 16.2 GPa was achieved without intentional heating and substrate bias. The poor corrosion resistance of the coatings with lower B contents can be enhanced with a further increase of B content up to 6.4 at.% and reaching a maximum of 10.3 times improvement than that of AISI 304 stainless steel.

Effect of peak discharge current on the ion current density on the substrate in the short-pulse HiPIMS

The bombardment of the substrate with accelerated ions from the plasma during the magnetron sputtering process is an effective way of controlling the energy transfer to the coating. One of the ways to increase the ion flux on the substrate is to change the parameters of the discharge power supply pulses. This work investigates the effect of the discharge current pulse amplitude on the average ion current density on the substrate in short-pulse high power impulse magnetron sputtering (s-HiPIMS). During sputtering, the peak discharge current varied from 25 to 250 A with a fixed pulse duration of 6 μs and an average discharge power of 1 kW. Experimental results and theoretical calculations show that the average ion current density on the substrate increases twofold when the amplitude of the discharge current pulses is increased from 25 to 60 A. As the amplitude of the discharge current pulses is further increased, the average ion current density on the substrate stops growing and begins to decrease at currents above 150 A. The paper discusses the reasons for the nonlinear dependence of the average ion current density on the substrate on the amplitude of the discharge current pulses.

Optimizing Propellant Distribution for Interorbital Transfers

The advent of space exploration missions, especially those aimed at establishing a sustainable presence on the Moon and beyond, necessitates the development of efficient propulsion and mission planning techniques. This study presents a comprehensive analysis of chemical and electric propulsion systems for spacecraft, focusing on optimizing propellant distribution for missions involving transfers from Low-Earth Orbit (LEO) to Geostationary Orbit (GEO) and the Lunar surface. Using mathematical modeling and optimization algorithms, we calculate the delta-v requirements for key mission segments and determine the propellant mass required for each propulsion method. The results highlight the trade-offs between the high thrust of chemical propulsion and the high specific impulse of electric propulsion. An optimization model is developed to minimize the total propellant mass, considering a hybrid approach that leverages the advantages of both propulsion types. This research contributes to the field of aerospace engineering by providing insights into propulsion system selection and mission planning for future exploration missions to the Moon, Mars, and Venus.

Direct fusion drive based on centrifugal mirror confinement

A concept for direct fusion drive based on centrifugal mirror (CM) confinement of thermonuclear plasmas (DFD-CM) is described. In centrifugal mirrors, electric and magnetic fields are combined to confine the plasma within a rapidly rotating annulus of burning plasma fixed between two mirror magnets. High energy fusion products leave the reactor core at a rate determined by the velocity of plasma rotation and the strength of the mirrors. Those departing through the jet-side mirror deposit their energy in a “warm” plasma that then expands through a magnetic nozzle to deliver jet power in the 100–1000 kW range. Fusion products departing through the power-side mirror are converted to electricity to power the reactor. Moderate thrusts at attractive specific impulses (10,000+ seconds) are possible. Findings are presented on CM reactor dynamics in propulsion applications, to include new insights into the relationship between mirror and centrifugal components of plasma confinement. Additionally, analysis will be presented on reactor operability limits and characterization of viable configurations based on power density, technology constraints, and the ability to self-power. Ongoing research into the physics of the warm plasma will be discussed, to include description of improved fidelity estimates for fusion energy deposition. Finally, considerations for Alfvén’s frozen-in theorem relative to fusion plasmas and magnetic nozzle performance will be outlined.Viable space commerce and future space exploration will require advanced power and propulsion technologies capable of multi-MW power generation with high specific impulse, moderate thrust levels, and low system specific mass. DFD could make a round trip to Mars in 3 months, and to Saturn, in less than 3 years. A DFD-CM powered mission could deliver an orbiter and 4 atmospheric probes to Neptune in four years. A second-generation Interstellar Probe powered by DFD-CM could reach the edge of the heliosphere (1000 astronomical units) in 25 years.

Executive functioning, behavior, and white matter microstructure in the chronic phase after pediatric mild traumatic brain injury: results from the adolescent brain cognitive development study.

Mild traumatic brain injury (mTBI) is common in children. Long-term cognitive and behavioral outcomes as well as underlying structural brain alterations following pediatric mTBI have yet to be determined. In addition, the effect of age-at-injury on long-term outcomes is largely unknown. Children with a history of mTBI (n = 406; Mage = 10 years, SDage = 0.63 years) who participated in the Adolescent Brain Cognitive Development (ABCD) study were matched (1:2 ratio) with typically developing children (TDC; n = 812) and orthopedic injury (OI) controls (n = 812). Task-based executive functioning, parent-rated executive functioning and emotion-regulation, and self-reported impulsivity were assessed cross-sectionally. Regression models were used to examine the effect of mTBI on these domains. The effect of age-at-injury was assessed by comparing children with their first mTBI at either 0-3, 4-7, or 8-10 years to the respective matched TDC controls. Fractional anisotropy (FA) and mean diffusivity (MD), both MRI-based measures of white matter microstructure, were compared between children with mTBI and controls. Children with a history of mTBI displayed higher parent-rated executive dysfunction, higher impulsivity, and poorer self-regulation compared to both control groups. At closer investigation, these differences to TDC were only present in one respective age-at-injury group. No alterations were found in task-based executive functioning or white matter microstructure. Findings suggest that everyday executive function, impulsivity, and emotion-regulation are affected years after pediatric mTBI. Outcomes were specific to the age at which the injury occurred, suggesting that functioning is differently affected by pediatric mTBI during vulnerable periods. Groups did not differ in white matter microstructure.

Multiphysics and multi-scale design and analysis of nuclear thermal propulsion pellet bed reactor based on spherical cermet fuel element

Due to the advantages of high thrust and high specific impulse, nuclear thermal propulsion (NTP) is a preferred near-term rocket engine technology for future Mars missions. This article introduces the reactor design based on spherical cermet fuel element, with the aim of studying the feasibility of applying this new fuel in NTP system. First, design requirements are determined based on the unique features of NTP. In terms of neutronics, the effect of rocket launch accidents and fuel loss caused by high-temperature hydrogen are considered. Thermal hydraulics refer to the requirements of NASA's Mars Design Reference Architecture 5.0 (DRA 5.0) for impulse, thrust, and thrust to weight ratio. Second, based on the requirements above, the optimal reactor configuration parameters are obtained with the goal of maximizing the thrust to weight ratio: reactor radius 51.1 cm, height 106 cm, aspect ratio 1.04, reflector 13 cm, and reactor mass 3940 kg. Finally, the performances of the optimal reactor design are analyzed. The neutron spectrum shows a characteristic of fast neutron spectrum, and fuel loss analysis shows that the core can withstand a fuel mass loss of about 4 wt%. In addition, the core axial and radial power distribution are calculated, with an overall power peak factor of 1.26. The thermal hydraulic calculation provides a range of core operating conditions that satisfy the design requirements of DRA 5.0 and temperature, with power of 620 ∼ 950 MW and flow rate of 16 ∼ 24 kg/s. Compared with the ANL200/2000 reactor using prismatic cermet, it has the advantage of higher specific impulse. The main disadvantage is the large pressure drop, which prevents it from being applied to the scenarios of high power and high thrust. Therefore, for NTP reactor using spherical cermet elements, it should be applied to low to medium power scenarios.

A novel calculation method for low-thrust transfer trajectories in the Earth-Moon restricted three-body problem

This paper introduces a novel trajectory calculation method for achieving continuous low-thrust transfers from the geostationary orbit to libration point orbits within the Earth-Moon restricted three-body framework. Low-thrust engines can offer benefits such as high specific impulse and long operating lifetimes, making them suitable for deep space exploration. However, the primary challenge lies in the low thrust level, leading to prolonged flight duration for spacecraft to overcome Earth's gravitational pull. Furthermore, the transfer trajectories exhibit multiple revolutions around the Earth, adding complexity to the calculations. To solve these difficulties, a novel trajectory computation method is presented, which for the first time discusses dynamical evolution beyond a predefined time interval in the context of an optimal control problem specific to low-thrust engines. This method employs a backward integration technique applied to the known optimized solution, coupled with a deliberate extension of the flight time to generate an initial guess for subsequent trajectory optimization, significantly simplifying the computational procedure. Several application scenarios involving transfer from the geostationary orbit to libration point orbits are demonstrated. The results confirm the effectiveness of this method, providing a rapid computational strategy for similar low-thrust transfer missions.