Jet Propulsion Research Articles

The contractile efficiency of the mantle muscle of European common cuttlefish (Sepia officinalis) during cyclical contractions.

Escape jet propulsion swimming in cuttlefish (Sepia officinalis) is powered by the circular muscles surrounding the mantle cavity. This mode of locomotion is energetically costly compared with undulatory swimming. The energetic cost of swimming is determined by the mechanical power requirements and the efficiency with which chemical energy is transferred into useful mechanical work. One step in this energy transduction process is the transfer of energy from ATP hydrolysis into mechanical work by the muscles. Here, we determined the efficiency of this step, termed the contractile efficiency. Muscle preparations from the circular muscles of the mantle cavity were subjected to sinusoidal length changes at different cycle frequencies, and stimulated with a phase and duration that maximised initial net work. Changes in ATP, arginine phosphate and octopine content between control and exercised muscles were determined and used to calculate the energy released from ATP hydrolysis (Emet). The maximum contractile efficiency (the ratio of net work to Emet) was 0.37, occurring at the same cycle frequency at which mechanical power was maximal and that was used during jet propulsion swimming, suggesting that cuttlefish muscle is adapted to generate muscular power efficiently. The overall efficiency of cuttlefish jet propulsion swimming was estimated to be 0.17, which is broadly comparable to that measured during animal flight and human-powered pedalled locomotion, indicating the high energetic costs of jet propulsion swimming are not due to inefficient locomotion per se; instead, they result from the relatively high mechanical power requirements.

Research on Aircraft Engines and Advanced Power in Land, Sea and Air

This paper provides a comprehensive overview of advanced propulsion technologies in military applications across land, sea, and air domains. It examines the theoretical foundations of propulsion systems, tracing the evolution of aircraft engines from early piston designs to modern jet propulsion. The study explores current state-of-the-art technologies, including advanced turbofan engines, hybrid electric systems, and nuclear propulsion for naval vessels. Special attention is given to emerging fields such as unmanned aerial vehicle propulsion, hypersonic technologies, and stealth engine designs. The research also delves into futuristic concepts like magnetohydrodynamic propulsion and pulse detonation engines. Throughout the analysis, common themes of improved efficiency, enhanced power-to-weight ratios, and increased operational capabilities are highlighted. This paper aims to provide a holistic view of the current landscape and future trajectory of military propulsion technologies, underlining their critical role in shaping modern warfare capabilities.

Investigation of microstructural and thermal stability of Ni-Y-Zr ternary nanocrystalline alloy

This investigation focused on the thermal stability of nanocrystalline (NC) binary and ternary Ni-Y-Zr alloys synthesized through ball-milling. The microstructural changes following annealing, conducted up to 1200 °C, were studied using various techniques, including X-ray-line-broadening, micro-hardness, and transmission electron microscopy. The results revealed that the rate of grain growth observed in the Ni-Y-Zr ternary alloy at 600 °C resembled that in pure NC-Ni at 100 °C. Moreover, the Ni-1.4Y-1.1Zr ternary system exhibited a maximum hardness of 753 HV (average) at 600 °C, which was approximately 60 HV higher than the Ni-1.2Y/1.9Y and Ni-1.5Zr/2.7Zr binary alloys and more than double that of pure NC-Ni for similar grain sizes. These characteristics were linked to the formation of nano-sized oxides and nitrides of Y and Zr within the microstructure. In summary, this study emphasizes the notable high-temperature microstructure stability of Ni-based ternary alloys, attributed to the additive effects of Y and Zr. Due to this extended stability, this ternary system could find potential applications at elevated temperatures in areas such as jet engine turbine blades and power plants.

Biomimetic Soft Robotic Jellyfish for Lentic Ecosystem Monitoring

Environmental monitoring of lentic ecosystems is well suited for swarm robotics applications since they can operate autonomously and cover large regions. For such a task, a locomotion mechanism is necessary for traversal. Due to the challenging nature of underwater environments, researchers often draw inspiration from nature to improve robot mechanical performance. A box jellyfish in a good inspiration due to their efficient jet propulsion. Soft and smart materials are helpful in mimicking their propulsion because they can perform flexible and complex movement. Shape memory alloy (SMA) springs have been used for this purpose, but their slow actuation rate is a well-known disadvantage. This project aims to improve cycle rate and thus swim speed by implementing a bistable spring configuration into a soft robotic jellyfish. The bistable mechanism stores energy slowly in the expansion of the elastic silicone bell, then releases it suddenly in a contraction which propels the robot forwards with a higher force than would be possible with direct SMA actuation. Additionally, the antagonistic arrangement of SMA springs reset each other and produce the same outward expansion on both up and down stroke, improving cycles speeds by removing the need for a dedicated reset stroke which is typically required before using the springs again. Also, increasing the number of spring pairs does not interfere with the actuation, meaning cycle rates can be further improved by cycling which pair of springs is active. The proof-of-concept device operates at a frequency of 0.4 Hz, and produces enough thrust while tethered to swim through a tank. Future work involves performing fluid visualization tests to validate a simple mathematical model of flow through the bell, as well as optimize the design, integrate onboard environment sensors and implement autonomy to allow operation in a larger swarm.

Observed jet power and radiative efficiency of black hole candidates in the Kerr+PFDM model

In this research, we explore the electromagnetic energy emitted by astrophysical black holes within the Kerr+PFDM (Kerr + perfect fluid dark matter) spacetime, a model comprising rotating black holes surrounded by dark matter. Our investigation focuses on black holes within X-ray binary systems, namely GRS 1915+105, GRO J1655-40, XTE J1550-564, A0620-00, H1743-322, and GRS 1124-683. Our findings indicate that the Kerr+PFDM spacetime can account for the radiative efficiency of these sources as determined through the continuum-fitting method (CFM). Additionally, employing the Blandford–Znajek mechanism, we demonstrate the ability to replicate the observed jet power. By combining the outcomes of both analyses for the selected objects, we establish more rigorous constraints on the spacetime parameters. Notably, our results reveal that, similar to the Kerr spacetime, the Kerr+PFDM spacetime cannot simultaneously account for the observed jet power and radiative efficiency of GRS 1915+105.

Automated Identification of Outgassed Chemical Species Using Mass Spectrometry for Scientific Space Missions

Current and planned space exploration and life detection missions such as NASA Jet Propulsion Laboratory’s Mars 2020, Mars Sample Return, and Europa Clipper require record-low contamination levels. In this work, we develop a novel automated outgassing contamination species identification method using mass spectrometry data. Thanks to the existing knowledge of ASTM-E1559 and direct analysis in real-time mass spectrometry material testing methods, we improved species outgassing deconvolution and physical characterization techniques. We developed a brand-new combined approach that leverages both tests’ complementary insights into contaminants’ chemical identities. Namely, we rely on the Dromey–Foyster algorithm and the Seven Golden Rules of mass spectrometry analysis to narrow down the probable identified molecules by a factor of 10 compared to the sole use of ASTM-E1559. Furthermore, thanks to recent advances in machine learning spectral analysis, we developed a composite spectral score that ranks all candidate contaminants based on their similarity to the measurements. Ultimately, we validated an automated species identification algorithm on samples of NuSil CV4-2946, Dacron, and a spacecraft cable component. The techniques established in this work enable accurate estimations of outgassed contaminant species’ chemical structure, leading to a comprehensive understanding of the effects of outgassing on scientific objectives.

Constraining the physical properties of large-scale jets from black hole X-ray binaries and their impact on the local environment with blast-wave dynamical models

ABSTRACT Relativistic discrete ejecta launched by black hole X-ray binaries (BH XRBs) can be observed to propagate up to parsec-scales from the central object. Observing the final deceleration phase of these jets is crucial to estimate their physical parameters and to reconstruct their full trajectory, with implications for the jet powering mechanism, composition, and formation. In this paper, we present the results of the modelling of the motion of the ejecta from three BH XRBs: MAXI J1820$+$070, MAXI J1535–571, and XTE J1752–223, for which high-resolution radio and X-ray observations of jets propagating up to $\sim$15 arcsec ($\sim$0.6 pc at 3 kpc) from the core have been published in the recent years. For each jet, we modelled its entire motion with a dynamical blast-wave model, inferring robust values for the jet Lorentz factor, inclination angle and ejection time. Under several assumptions associated to the ejection duration, the jet opening angle and the available accretion power, we are able to derive stringent constraints on the maximum jet kinetic energy for each source (between $10^{43}$ and $10^{44}$ erg, including also H1743–322), as well as placing interesting upper limits on the density of the ISM through which the jets are propagating (from $n_{\rm ISM} \lesssim 0.4$ cm$^{-3}$ down to $n_{\rm ISM} \lesssim 10^{-4}$ cm$^{-3}$). Overall, our results highlight the potential of applying models derived from gamma-ray bursts to the physics of jets from BH XRBs and support the emerging picture of these sources as preferentially embedded in low-density environments.

Climate Change and Vegetation Greening Jointly Promote the Increase in Evapotranspiration in the Jing River Basin

Within the Earth’s terrestrial environment, evapotranspiration significantly contributes to the hydrological cycle, accounting for around 80% of the precipitation on landmasses to be reintroduced into the atmosphere. This mechanism profoundly affects the distribution and availability of surface water resources throughout the ecosystem. Gaining insight into the factors influencing local evapotranspiration fluctuations in response to varying climatic and vegetative scenarios is crucial for effective water management strategies and rehabilitating ecosystem resilience. To this end, our study focuses on the Jing River Basin in the Loess Plateau, utilizing multi-source remote sensing data and climatic information to investigate the spatiotemporal dynamics of evapotranspiration from 1984 to 2018 through the application of the Priestley–Taylor Jet Propulsion Laboratory (PT-JPL) model. Our research results indicate a general ascending tendency in evapotranspiration across the investigated region, demonstrating a notably discernible escalation at a pace of approximately 3.11 mm/year (p < 0.01), with an annual vegetation ET volume reaching 533.88 mm. Across different vegetation types in the Jing River Basin between 1984 and 2018, the mean yearly ET was observed to be highest in forests (572.88 mm), followed by croplands (564.74 mm), shrublands (536.43 mm), and grasslands (503.42 mm). The leaf area index (LAI) demonstrated the strongest partial correlation with ET (r = 0.35) and contributed the most significantly to the variation in ET within the Jing River Basin (0.41 mm/year). Additionally, LAI indirectly influences ET through its impact on vapor pressure deficit (VPD), precipitation (Pre), and temperature (Temp). Radiation is found to govern most ET changes across the region, while radiation and precipitation notably affected ET by modulating air temperature. In summary, these radiant energy changes directly affect the evaporation rate and total evapotranspiration of surface water. It provides important support for understanding how evapotranspiration in the Jing River Basin is adjusting to climate change and increased vegetation cover. These findings serve as a theoretical foundation for devising sustainable vegetation restoration strategies to optimize water resource utilization within the region.

Miniature Modular Reconfigurable Underwater Robot Based on Synthetic Jet.

Modular reconfigurable robots exhibit prominent advantages in the reconnaissance and exploration tasks within unstructured environments for their characteristics of high adaptability and high robustness. However, due to the limitations in locomotion mechanism and integration requirements, the modular design of miniature robots in the aquatic environment encounters significant challenges. Here, a modular strategy based on the synthetic jet principle is proposed, and a modular reconfigurable robot system is developed. Specialized bottom and side jet actuators are designed with vibration motors as excitation sources, and a motion module is developed incorporating the jet actuators to realize three-dimensional agile motion. Its linear, rotational, and ascending motion speeds reach 70.7mms-1, 3.3rads-1, and 28.7mms-1, respectively. The module integrates the power supply, communication, and control system with a small size of 48mm × 38mm × 38mm, which ensures a wireless controllable motion. Then, various configurations of the multi-module robot system are established with corresponding motion schemes, and the experiments with replaceable intermediate modules are further conducted to verify the transportation and image-capturing functions. This work demonstrates the effectiveness of synthetic jet propulsion for aquatic modular reconfigurable robot systems, and it exhibits profound potential in future underwater applications.

Hydrodynamic performance evaluation of pump-jet propulsion based on the toroidal propeller

Pump jet propulsion (PJP) is a widely used propulsion method for underwater vehicles. Compared with traditional propeller propulsions, it has the characteristics of higher propulsion efficiency, lower noise, and better performance. A novel propeller with annular blades, named as ‘the toroidal propeller’, is designed and discussed with its characteristic parameters. Then the novel propeller is installed to the PJP and Suboff submarine to evaluate its performance with Computational Fluid Dynamics (CFD) simulations. The high-speed range of modified submarine with the toroidal propeller is also predicted and analyzed through propulsion parameters. The results indicate that when the toroidal propeller is applied to the PJP of underwater vehicle, its propulsion efficiency can reach 0.88 at the speed coefficient of 1.2. When the rotator speed is 5000 RPM, the pump jet thruster with toroidal propellers can continue to provide effective thrust, which will easily cause the speed of submarine to exceed 60 kn.

Gdcov2sinex: a Python conversion tool from GipsyX’s gdcov file to SINEX file

The Solution INdependent EXchange (SINEX) file format, an international standard for the exchange of information, is essential in the Global Navigation Satellite System (GNSS) processing strategies that integrate different software applications. GNSS data processing using Jet Propulsion Laboratory’s (JPL) GipsyX software, which employs the Precise Point Positioning (PPP) technique, generates positions and covariance matrices in gdcov files, a GipsyX file format specific for storing this information. GipsyX software provides a tool, named mkDailySinex.py, to convert from gdcov file to SINEX file, but it is designed specifically for creating daily JPL SINEX files and does not function properly for non-JPL GipsyX users. I have developed a Python 3 program, named gdcov2sinex.py, which solves this problem, enabling any user to perform the SINEX conversion and, therefore, apply the processing strategies that integrate GipsyX with other software, such as GAMIT/GLOBK. The new python tool presented herein takes advantage of the capabilities of mkDailySinex.py and provides all its default options, but also expands the number of selectable options, which can be useful to the user. The source code, user manual, and a sample dataset of gdcov2sinex.py are provided as electronic supplementary material of this paper.

Estimation and spatiotemporal analysis of actual evapotranspiration over Qinghai-Tibet Plateau using an Alpine Grassland-Adapted Priestley-Taylor model

Evapotranspiration (ET) is a crucial process in the land water cycle, energy balance, and carbon cycle, making it essential for understanding ecosystem health and climate change. The Qinghai-Tibet Plateau (QTP) is a vital contributor to the global water cycle and ecosystem, and its water resources and ecological environment are of great significance to the development and survival of Asia. To accurately estimate ET on the QTP, this paper proposes an improved Priestley-Taylor (PT) model based on shortwave infrared soil moisture index (SIMI). The model is applied to estimate ET on the QTP from 2011 to 2020, allowing for a comprehensive spatiotemporal analysis. The findings indicate that, (1) The PT-SIMI model has higher estimation accuracy than both the Modified Satellite-Based Priestley-Taylor (MS-PT) model and the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model at most sites, particularly in alpine grasslands sites, and demonstrates a greater sensitivity in capturing changes in soil moisture; (2) the spatial distribution of ET on the QTP demonstrates a declining pattern from southeast to northwest; (3) the average ET from 2011 to 2020 remains relatively stable at 478 mm/year; (4) notable spatial variations in ET are observed across the plateau, with noticeable upward trends observed in the central and western regions, while the south central region experiencing a decreasing trend. This study provides valuable insights into the water cycle and ecological environment of the QTP and its findings can support sustainable development in the region.

Gravitational decoupling and aerodynamics: black holes and analog gravity in a jet propulsion lab

A connection is established between transonic sound waves propagating along a de Laval nozzle and quasinormal modes emitted from hairy black holes obtained with the gravitational decoupling method applied to the Reissner–Nordström geometry. Aerodynamical features provide an analogue setup to test experimentally perturbations of fluid flows in a de Laval nozzle producing quasinormal modes. In particular, nozzle shape, pressure, Mach number, temperature, density, and thrust coefficient profiles are determined as functions of the black hole parameters for several multipole numbers. The black hole quasinormal mode frequencies are also investigated for different overtones, evaluating the quality factor of the nozzle.

Salpot: A Jet Propulsion Swimmer With Scissor Structure and Bilateral Apertures

Salpot: A Jet Propulsion Swimmer With Scissor Structure and Bilateral Apertures

Prediction of steady hydrodynamic performance of pump jet propulsion based on free wake vortex model

Due to mutual interference between various components, the transitional motion of fluid particles in the flow field of pump jet propulsion becomes more complex and variable. Additionally, the vortex structure at the wake can undergo severe contraction and deformation. To further improve the accuracy of predicting the hydrodynamic performance of pump jet propulsion, this paper proposes a time-varying, space-varying, and induced velocity-varying free wake numerical calculation model based on potential flow theory. A set of hydrodynamic performance prediction methods that consider the interference of the free wake model is also established. Furthermore, a velocity smoothing model based on time reversal is constructed based on the distribution pattern of numerical singularity points during the induced velocity calculation process, which enhances the robustness of the calculation program. By comparing and analyzing the numerical calculation results with experimental results, including pressure, circulation distribution, and hydrodynamic performance, the accuracy of the free wake model proposed in this paper is verified. The results also demonstrate that the free wake model proposed in this paper can effectively improve the prediction accuracy of the hydrodynamic performance of the pump jet propulsion.

Characterizing the γ-Ray Emission from FR0 Radio Galaxies

FR0 galaxies constitute the most abundant jet population in the local Universe. With their compact jet structure, they are broadband photon emitters and have been proposed as multimessenger sources. Recently, these sources have been detected for the first time in γ rays. Using a revised FR0 catalog, we confirm that the FR0 population as a whole are γ-ray emitters, and we also identify two significant sources. For the first time, we find a correlation between the 5 GHz core radio luminosity and γ-ray luminosity in the 1–800 GeV band, having a 4.8σ statistical significance. This is clear evidence that the jet emission mechanism is similar in nature for FR0s and the well-studied canonical FR (FRI and FRII) radio galaxies. Furthermore, we perform broadband spectral energy distribution modeling for the significantly detected sources as well as the subthreshold source population using a one-zone synchrotron self-Compton model. Within the maximum jet power budget, our modeling shows that the detected γ rays from the jet can be explained as inverse Compton photons. To explain the multiwavelength observations for these galaxies, the modeling results stipulate a low bulk Lorentz factor and a jet composition far from equipartition, with the particle energy density dominating over the magnetic field energy density.

Jellyfish-Inspired Soft Robot Driven by Pneumatic Bistable Actuators.

Soft actuators offer numerous potential applications; however, challenges persist in achieving a high driving force and fast response speed. In this work, we present the design, fabrication, and analysis of a soft pneumatic bistable actuator (PBA) mimicking jellyfish subumbrellar muscle motion for waterjet propulsion. Drawing inspiration from the jellyfish jet propulsion and the characteristics of bistable structure, we develop an elastic band stretch prebending PBA with a simple structure, low inflation cost, exceptional driving performance, and stable driving force output. Through a bionic analysis of jellyfish body structure and motion, we integrate the PBA into a jellyfish-like prototype, enabling it to achieve jet propulsion. To enhance the swimming performance, we introduce a skin-like structure for connecting the soft actuator to the jellyfish-like soft robot prototype. This skin-like structure optimizes the fluid dynamics during jet propulsion, resulting in improved efficiency and maneuverability. Our study further analyzes the swimming performance of the jellyfish-like prototype, demonstrating a swimming speed of 3.8 cm/s (0.32 body length/s, BL/s) for the tethered prototype and 4.7 cm/s (0.38 BL/s) for the untethered prototype. Moreover, we showcase the jellyfish-like prototype's notable load-bearing capacity and fast-forward swimming performance compared to other driving methods for underwater biomimetic robots. This work provides valuable insights for the development of highly agile and fast responsive soft robots that imitate the subumbrellar muscle of jellyfish for efficient water-jet propulsion, utilizing skin-like structures to enhance swimming performance.

Satellite-Based PT-SinRH Evapotranspiration Model: Development and Validation from AmeriFlux Data

The Priestley–Taylor model of the Jet Propulsion Laboratory (PT-JPL) evapotranspiration (ET) model is relatively simple and has been widely used based on meteorological and satellite data. However, soil moisture (SM) constraints include a vapor pressure deficit (VPD) that causes large uncertainty. In this study, we proposed a PT-SinRH model by introducing a sine function of air relative humidity (RH) to replace RHVPD to characterize SM constraints, which can improve the accuracy of ET estimations. The PT-SinRH model is validated by eddy covariance (EC) data from 2000–2020. These data were collected by AmeriFlux at 28 sites on the conterminous United States (CONUS), and the land cover types of the sites vary from croplands to wetlands, grasslands, shrub lands and forests. The validation results from daily scale-based on-site and satellite data inputs showed that the PT-SinRH model estimates fit the observations with a coefficient of determination (R2) of 0.55, root-mean-square error (RMSE) of 17.5 W/m2, bias of −1.2 W/m2 and Kling–Gupta efficiency (KGE) of 0.70. Additionally, the PT-SinRH model based on reanalysis and satellite data inputs has an R2 of 0.49, an RMSE of 20.3 W/m2, a bias of −8.6 W/m2 and a KGE of 0.55. The PT-SinRH model showed better accuracy when using the site-measured meteorological data than when using reanalysis meteorological data as inputs. Additionally, compared with the PT-JPL model, the results demonstrate that our approach, i.e., PT-SinRH, improved ET estimates, increasing the R2 and KGE by 0.02 and decreasing the RMSE by about 0.6 W/m2. This simple but accurate method permits us to investigate the decadal variation in regional ET over the land.

A physical model for radio and X-ray correlation in black hole X-ray binaries

ABSTRACT A tight correlation between the radio and X-ray emission in the hard state of black hole X-ray binaries (BHXRBs) indicates an intrinsic disc–jet connection in stellar black hole (BH) accretion systems, though the detailed physics processes at work are still quite unclear. A hot accretion flow is suggested to match the outer cold thin disc at a certain radius in the hard state, which may vary with the accretion rate. In this work, we assume that the magnetic field generated in the outer thin disc is advected inwards by the inner hot accretion flow, which is substantially enhanced near the BH. Such a strong field threading the horizon of a spinning BH is responsible for launching relativistic jets in BHXRBs via the Blandford–Znajek mechanism. Thus, both the jet power and the X-ray emission increase with the mass accretion rate, and we find that our model calculations are able to reproduce the observed radio/X-ray correlation quantitatively. For some individual BHXRBs, the slopes of the radio/X-ray correlations become steeper when the sources are brighter. Our model calculations show that this feature is due to the transition of the outer disc from gas pressure dominated to radiation pressure dominated, which leads to different accretion rate dependence of the field strength in the outer disc.

Simulations of pulsed overpressure jets: formation of bellows and ripples in galactic environments

ABSTRACT Jets from active nuclei may supply the heating which moderates cooling and accretion from the circum-galactic medium. While steady overpressured jets can drive a circulatory flow, lateral energy transfer rarely exceeds 3 per cent of jet power, after the initial bow shock has advanced. Here, we explore if pulses in high-pressure jets are capable of sufficient lateral energy transfer into the surrounding environment. We answer this by performing a systematic survey of numerical simulations in an axisymmetric hydrodynamic mode. Velocity pulses along low Mach jets are studied at various overpressures. We consider combinations of jet velocity pulse amplitude and frequency. We find three flow types corresponding to slow, intermediate, and fast pulsations. Rapid pulsations in light jets generate a series of travelling shocks in the jet. They also create ripples which propagate into the ambient medium while a slow convection flow brings in ambient gas which is expelled along the jet direction. Long period pulses produce slowly evolving patterns which have little external effect, while screeching persists as in non-pulsed jets. In addition, rapid pulses in jets denser than the ambient medium generate a novel breathing cavity analogous to a lung. Intermediate period pulses generate a series of bows via a bellows action which transfer energy into the ambient gas, reaching power efficiencies of over 30 per cent when the jet overpressure is sufficiently large. This may adequately inhibit galaxy gas accretion. In addition, such pulses enhance the axial out-flow of jet material, potentially polluting the circum-galactic gas with metal-enriched interstellar gas.