Cold Gas Jets Research Articles

Aerodynamic characteristics of the retro propulsion landing burn of vertically landing launchers

In the frame of the European funded H2020 project RETALT (retro propulsion-assisted landing technologies), the unsteady aerodynamics of vertically descending and landing launchers have been investigated. In this paper, experimental data of the landing burn tested in the Vertical Free-Jet Facility Cologne at DLR in Cologne are presented. The landing burn was simulated with a cold gas jet of pressurized air opposing the wind tunnel free stream. Tests with several jet conditions were compared to results without active jet. Proper orthogonal decomposition of schlieren recordings and spectral analyses of their time histories are performed and are compared to frequencies in pressure measurements. Dominant frequencies were found, which are strongest at Mach 0.8. Especially, a Strouhal number of 0.2 was found to be most dominant. The intensity of the dominant frequencies can be lowered if the engine is active. The normalized root mean square pressure fluctuations are between 0.1 and 0.3 during the landing maneuver. Additionally, the steady flow features scale well with the ambient pressure ratio and the momentum flux ratio. The unsteady flow field dynamics of the subsonic retro propulsion flow field can likely be linked to large-scale turbulent structures in the supersonic jet, triggering large-scale pressure fluctuations and altering the overall flow field.

Trajectory design and dispersion analysis of nano moon lander OMOTENASHI

OMOTENASHI is a CubeSat that was launched by a NASA SLS rocket. Its mission was to demonstrate that a CubeSat could make a semi-hard landing on the Moon. A chemical propulsion system which provides high thrust and can be re-ignited is large and difficult to install on a CubeSat. Therefore, a small cold-gas jet makes orbit corrections with only a small ΔV. Moreover, a rocket motor with a high Isp and structural mass ratio is used for a lunar landing deceleration. The spacecraft consists of an orbiting module, a rocket motor, and a surface probe. This paper analyzes the trajectory design of the Moon landing and a method that increases the landing success rate under the tight constraints of the CubeSat. To reduce fuel and power consumption, the maneuver conditions during the lunar transition to reach the target landing site are evaluated based on several error factors. This study considers the trade-off between vertical and horizontal landings. Because active control is not possible for decelerating a rocket motor for the lunar landing, the optimal altitude at the starting maneuver is determined by considering such errors as attitude and timing. Finally, the paper discusses mission feasibility and the landing success rate.

Laser ionization scheme development for in-gas-jet spectroscopy studies of Th+

The in-gas laser ionization and spectroscopy (IGLIS) technique has been a cornerstone in the study of heavy elements. The addition of a convergent–divergent (de Laval) nozzle to perform laser ionization in a cold hypersonic gas jet greatly improves the achievable resolution. Recent efforts have focused on preparing the in-gas-jet method for the study of the low-lying 229Th isomer. Tailor-made recoil sources of 233U are installed inside a fast extraction gas cell to provide the (isomeric) thorium ions. A level search above the second ionization potential (IP) uncovered several auto-ionizing states, greatly improving the laser ionization efficiency of singly charged thorium ions.

Jet-supercavity interaction and instability mechanism analysis

In this research, an experimental system that couples the supercavity and the tail jet was established, aiming at exploring on the cavity instability mechanism. Both high pressure gas tank and solid rocket motor were used to generate the tail jet. The model shape and the jet rate were all varied to investigate different flow patterns. Experiments for the cold gas jet were first carried out, obtaining the variation of the flow pattern with the jet strength and the relative location. With strong jet intensity, the supercavity could lose instability by the re-entrained liquid jet, which was mainly generated by the back attack of the tail jet. Furthermore, the effect of the rearward facing step structure on the cavity instability was investigated, validating that the re-entrained jet could be successfully suppressed by this structure. However, when the cavity contacts with the wall surface, another kind of instability induced by cavity/body interaction could be induced. Subsequently, experiments were carried out for the hot jet generated by the solid rocket motor. A new kind of cavity instability at the moment of ignition was observed. The cavity shrinking and collapse processes were compared between different cases. When the ignition process finished, the hot jet transited into a continuous free expansion mode with weak entrainment of liquid. Finally, the cavity instability mechanisms were summarized and compared. Spectral analysis was carried out for different cases. An obvious larger Strouhal number exists for the pressure pulse induced instability.

РАЗРАБОТКА СТЕНДА ИЗМЕРЕНИЯ ТЯГИ НА ОСНОВЕ АЭРОДИНАМИЧЕСКОГО МЕТОДА ДЛЯ ЭЛЕКТРОРАКЕТНЫХ ДВИГАТЕЛЕЙ МАЛЫХ КОСМИЧЕСКИХ АППАРАТОВ

A traction measurement stand based on the aerodynamic method has been developed. To test the stand, a prototype electric rocket engine was used as a cold gas engine. The working medium was nitrogen gas. At a flow rate of 1.2 mg/s, the thrust value was from 0.674 to 0.736 mN, at a flow rate of 1.7 mg/s, the thrust value was 0.934-1 mN and at a flow rate of 2.6 mg/s, the thrust value was from 1.59 to 1.634 mN. The experimental specific thrust impulse was at a flow rate of 1.2 mg/s from 574 to 613 m/s, at a flow rate of 1.7 mg/s from 549 to 588 m/s and at a flow rate of 2.6 mg/s from 612 to 623 m/s. According to the measured pressure values in the chamber of the prototype electric rocket engine, the values of the ideal flow rate of the working fluid from the nozzle were obtained, which amounted to 661 m/s at a flow rate of 1.2 mg/s, 667 m/s at a flow rate of 1.7 mg/s and 674 m/s at a flow rate of 2.6 mg/s. The obtained values of the specific thrust impulse do not contradict the previously obtained experimental data on cold gas jet engines using nitrogen as the working fluid, and also do not exceed the ideal design flow rate

Numerical Simulation of Orbit Controlled Hot-gas Lateral Jet of the triangular plate with rudder

Hypersonic interception weapons have high requirements for the efficiency and accuracy of the control system. As an effective control approach, the thermochemical non-equilibrium effect of jet flow must be considered in order to accurately predict the aerodynamic characteristic. At present, relevant researches are mostly focused on the low-flow rate hot jet, while numerical simulation and wind tunnel test studies on high-flow rate hot jet are rare. In this paper, the interaction flow field of the rail-controlled jet at the altitude of 60Km and 70Km has been simulated by solving the three-dimensional viscous fluid governing equations. The influence of the thermalchemical non-equilibrium effect of the jet interaction on the flow field characteristics and aerodynamic characteristics of the aircraft was analyzed. The primary results show that: (1) The flow fields of the cold-gas jet, frozen-gas jet and hot-gas jet have significant differences under the high-flow rate jet condition, which is mainly reflected the size and the pressure value of the separation region before the nozzle. The separation region length of the cold-gas jet is approximately twice that of the hot-gas jet and the length of the frozen-gas jet is between them; (2)Jet interaction will increase the surface pressure of the aircraft and reduce the skin-friction. When Ma=25, the aerodynamic interaction of hot jet is only about 30% of that of cold jet; (3) Jet interaction on aerodynamic characteristics increases with altitudes. With the increase of Mach number, the difference between the predicted results of hot jet and cold jet is enlarged because of the enhancement of the thermochemical non-equilibrium effect.

Large eddy simulation on the flow characteristics of an argon thermal plasma jet

Large eddy simulations based on the CFD software OpenFOAM have been used to study the effect of Reynolds number and turbulence intensity on the flow and mixing characteristics of an argon thermal plasma jet. Detailed analysis was carried out with respect to four aspects: the average flow field, the instantaneous flow field, turbulence statistical characteristics and the self-similarity. It was shown that for the argon thermal plasma jet with low Reynolds number, increasing the turbulence intensity will increase the turbulent transport mechanism in the mixing layer rather than in the jet axis, leading to the faster development of turbulence. The effect of the turbulent transport mechanism increases with increasing Reynolds number. However, the characteristics of flow and mixing are not affected by turbulence intensity for high Reynolds number situations. It was also found that the mean axial velocity and mean temperature in the axis of the turbulent thermal plasma jet satisfy the self-similarity aspects downstream. In addition, decay constant K is 1.25, which is much smaller than that (5.7–6.1) of the turbulent cold gas jet and has nothing to do with the Reynolds number or turbulence intensity in the jet inlet.

Numerical Simulation of the Cooling of Melt Droplets as Applied to the Technology of Production of Metal Powders

Problems on the development of mathematical models for control of the technological processes of producing powders of metals from their melts and for optimization of these processes were considered. A numerical simulation of the solidification of melt droplets in a turbulent cold-gas jet has been performed with the use of a complex mathematical model, and results of this simulation were used for estimating the influence of different factors on the flying of a melt droplet in a gas flow until it is solidified.

Exhaust CO emissions of a laminar premixed propane–air flame interacting with cold gas jets

This study investigates a laminar premixed flame interacting with cold gas jets, at different cooling jet mass flow fractions (m˙jet*) and diluent types, namely air and N2. A novel burner and wall configuration is used to experimentally induce flame-cooling-air interaction (FCAI). Flame chemiluminescence imaging, exhaust temperature (Texh) and exhaust CO emissions ([CO]exh) measurements are conducted to characterise the flame shape and [CO]exh response to the cooling jets. Flame imaging reveals that the cooling jets greatly affect the flame shape. Measurements of [CO]exh demonstrate a direct correlation with Texh, as decreasing Texh is observed to occur with decreasing [CO]exh. Additionally, the air diluent case shows consistently lower [CO]exh values, relative to the N2 diluent case.Using a novel modelling approach, the cooling jets are simulated using one-dimensional (1D) fully resolved simulations (FRS). The effect of jet dilution, jet cooling and exhaust gas cooling are independently and jointly investigated in these simulations. The FRS results support the experimentally observed behaviour, and show that exhaust gas cooling and exhaust gas oxygenation produce decreased CO concentrations. Using a chemical reactor network (CRN), the jet mixing process is modelled by a perfectly stirred reactor (PSR), while the exhaust gas cooling process is modelled by a plug flow reactor (PFR). The CRN modelling shows that the jet mass flow rates dictated by m˙jet*, the dilution time (tdil) assumed for cooling jet mixing, and the exhaust gas cooling residence time (tcool), play an important role in determining the [CO]exh. An equilibrium analysis illustrates that the relationship between [CO]exh, Texh and exhaust O2, is due to the thermodynamically favoured equilibrium states. Timescale analyses demonstrate that appropriate modelling of jet mixing, and accounting for the rate of exhaust gas cooling, are important for estimations of [CO]exh.

How martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion

Araneiforms are radially converging systems of branching troughs exhibiting fractal properties. They are found exclusively in the Southern polar regions of Mars and believed to be result of multiple repetitions of cold CO2 gas jets eruptions. Araneiform troughs get carved by the overpressurized gas rushing underneath a seasonal ice layer towards a newly created opening. Current work is an attempt to quantitatively analyze araneiforms patterns and model their formation mechanism. Araneiform shapes range from small and simple structures of one or two connected branches to intricate dendritic patterns several kilometers across. The dendritic quality of most araneiforms are suggestive that they can be described in terms commonly applied to terrestrial rivers. The main difference between rivers and araneiforms from the morphological point of view is that araneiform patterns are not directed or in any way influenced by the local gravitational gradient. We have adapted and for the first time applied to Martian araneiforms qualitative morphological analysis typically used for terrestrial rivers. For several locations in the Martian Southern polar regions we have calculated the largest order of tributaries, tributary densities, and bifurcation ratios. We have shown that the large and well-developed araneiforms (with tributary orders larger than 4) closely follow Horton's law of tributary orders and have bifurcation ratio that falls well inside the range of terrestrial rivers. We have implemented a two-dimensional Diffusion-Limited Aggregation (DLA) model that describes formation of dendrite shapes by mathematical probabilistic means. We compared modeled dendrite shapes to the araneiform shapes observed in the Martian polar regions and evaluated their similarity using the morphological analysis of araneiforms. We showed that DLA model can successfully recreate 2D shapes of different observed araneiforms. To simulate the patterns that deviate from central symmetry it is required to modify the main governing parameter of DLA model: its two-dimensional probability field. An analog to the governing probability field in the case of araneiforms is the gas pressure in the cavity underneath the ice layer right before the gas starts moving towards the newly created escape vent. Thus modeling the creation of araneiform patterns with DLA leads to better understanding of seasonal processes that create them.

Development of solid-gas equilibrium propulsion system for small spacecraft

A phase equilibrium propulsion system is a kind of cold-gas jet in which the phase equilibrium state of the fuel is maintained in a tank and its vapor is ejected when a valve is opened. One such example is a gas-liquid equilibrium propulsion system that uses liquefied gas as fuel. This system was mounted on the IKAROS solar sail and has been demonstrated in orbit. The system has a higher storage efficiency and a lighter configuration than a high-pressure cold-gas jet because the vapor pressure is lower, and is suitable for small spacecraft. However, the system requires a gas-liquid separation device in order to avoid leakage of the liquid, which makes the system complex. As another example of a phase equilibrium propulsion system, we introduce a solid-gas equilibrium propulsion system, which uses a sublimable substance as fuel and ejects its vapor. This system has an even lower vapor pressure and does not require such a separation device, instead requiring only a filter to keep the solid inside the tank. Moreover, the system is much simpler and lighter, making it more suitable for small spacecraft, especially CubeSat-class spacecraft, and the low thrust of the system allows spacecraft motion to be controlled precisely. In addition, the thrust level can be controlled by controlling the temperature of the fuel, which changes the vapor pressure. The present paper introduces the concept of the proposed system, and describes ejection experiments and its evaluation. The basic function of the proposed system is demonstrated in order to verify its usefulness.

COOL CORE CYCLES: COLD GAS AND AGN JET FEEDBACK IN CLUSTER CORES

Using high-resolution 3-D and 2-D (axisymmetric) hydrodynamic simulations in spherical geometry, we study the evolution of cool cluster cores heated by feedback-driven bipolar active galactic nuclei (AGN) jets. Condensation of cold gas, and the consequent enhanced accretion, is required for AGN feedback to balance radiative cooling with reasonable efficiencies, and to match the observed cool core properties. A feedback efficiency (mechanical luminosity $\approx \epsilon \dot{M}_{\rm acc} c^2$; where $\dot{M}_{\rm acc}$ is the mass accretion rate at 1 kpc) as small as $5 \times 10^{-5}$ is sufficient to reduce the cooling/accretion rate by $\sim 10$ compared to a pure cooling flow. This value is smaller compared to the ones considered earlier, and is consistent with the jet efficiency and the fact that only a small fraction of gas at 1 kpc is accreted on to the supermassive black hole (SMBH). We find hysteresis cycles in all our simulations with cold mode feedback: {\em condensation} of cold gas when the ratio of the cooling-time to the free-fall time ($t_{\rm cool}/t_{\rm ff}$) is $\lesssim 10$ leads to a sudden enhancement in the accretion rate; a large accretion rate causes strong jets and {\em overheating} of the hot ICM such that $t_{\rm cool}/t_{\rm ff} > 10$; further condensation of cold gas is suppressed and the accretion rate falls, leading to slow cooling of the core and condensation of cold gas, restarting the cycle. Therefore, there is a spread in core properties, such as the jet power, accretion rate, for the same value of core entropy or $t_{\rm cool}/t_{\rm ff}$. A fewer number of cycles are observed for higher efficiencies and for lower mass halos because the core is overheated to a longer cooling time. The 3-D simulations show the formation of a few-kpc scale, rotationally-supported, massive ($\sim 10^{11} M_\odot$) cold gas torus. (abstract abridged)

Thruster Plume Surface Interactions: Applications for Spacecraft Landings on Planetary Bodies

Numerical and experimental investigations of supersonic jet interactions with a flat surface at various atmospheric pressures are presented in this paper. These studies were done in assessing the landing hazards of both the NASA Mars Science Laboratory and the Phoenix Mars spacecraft. Temporal and spatial ground pressure measurements in conjunction with numerical solutions at altitudes of nozzle exit diameters and jet expansion ratios between 0.02 and 100 are used. This study shows that, for typical landing spacecraft engine parameters, thruster plumes exhausting into Martian environments create the largest surface pressure loads and can occur at high spacecraft altitudes in contrast to the jet interactions, which occur in terrestrial and lunar atmospheres. These differences are dependent on the stability and dynamics of the plate shock, the length of the supersonic core, and plume decay due to shear layer instability, all of which are functions of the jet expansion ratio. Theoretical, experimental, and analytical results show that subscale supersonic cold gas jets adequately simulate the flowfield and loads due to rocket plume impingement, provided important scaling parameters are in agreement. These studies indicate the critical importance of testing and modeling plume–surface interactions for descent and ascent of spacecraft and launch vehicles.

はやぶさ小惑星探査機に用いられたマイクロ波放電式イオンエンジン

The Hayabusa spacecraft rendezvoused with the asteroid Itokawa in 2005 after the powered flight in the deep space by the μl0 cathode‐less electron cyclotron resonance ion engines. Though the spacecraft was seriously damaged after the successful soft‐landing and lift‐off, the xenon cold gas jets from the ion engines rescued it. New attitude stabilization method using a single reaction wheel, the ion beam jets, and the photon pressure was established and enabled the homeward journey from April 2007 aiming the Earth return on 2010. The total accumulated operational time of the ion engines reaches 31,400 hours at the end of 2007. One of four thrusters achieved 13,400‐hour space operation.

Attitude control of a satellite by using digital signal processing

This article has discussed the development of a three-axis attitude digital controller for an artificial satellite using a digital signal processor. The main motivation of this study is the attitude control system of the satellite Multi-Mission Platform, developed by the Brazilian National Institute for Space Research for application in different sort of missions. The controller design was based on the theory of the Linear Quadratic Gaussian Regulator, synthesized from the linearized model of the motion of the satellite, i.e., the kinematics and dynamics of attitude. The attitude actuators considered in this study are pairs of cold gas jets powered by a pulse width/pulse frequency modulator. In the first stage of the project development, a system controller for continuous time was studied with the aim of testing the adequacy of the adopted control. The next steps had included an analysis of discretization techniques, the setting time of sampling rate, and the testing of the digital version of the Linear Quadratic Gaussian Regulator controller in the MATLAB/SIMULINK. To fulfill the study, the controller was implemented in a digital signal processor, specifically the Blackfin BF537 from Analog Devices, along with the pulse width/pulse frequency modulator. The validation tests used a scheme of co-simulation, where the model of the satellite was simulated in MATLAB/SIMULINK, while the controller and modulator were processed in the digital signal processor with a tool called Processor-In-the-Loop, which acted as a data communication link between both environments.function and required time to achieve a given mission accuracy are determined, and results are provided as illustration.

Intravital Pathophysiologic Comparison of Frostbite and Burn Injury in a Murine Model

The breakdown of skin microcirculation and the leukocyte-endothelium interaction are assumed to play key roles in the pathophysiology of burn and frostbite injuries. Available data on frostbite and burn injuries were collected using different experimental models and setups, which limits direct comparisons of these thermal traumata significantly. To determine pathophysiologic similarities and differences, two comparable in vivo frostbite and burn models were used to assess microcirculatory and angiogenetic changes in burn and frostbite injuries. Either deep partial thickness no-touch burns or frostbite injuries were inflicted to the ears of hairless mice (n = 40) by a hot or cold gas jet (117.0 ± 2.1°C for 1 s and -195.8 ± 2.7°C for 1.5 s, respectively) resulting in a necrotic, nonperfused area of about 1.56 ± 0.28 mm2. Intravital fluorescent microscopy was used in combination with fluorescent dyes in order to assess the microcirculation, angiogenesis, and leukocyte-activity over a 12-d period. The angiogenesis occurred significantly faster after frostbite than after burn (16.4% ± 4.5% versus 30.6% ± 2.8% nonperfused area, compared with the baseline value on d 7 (P = 0.009)). The loss of functional vessel density was significantly more pronounced after frostbite (57.6% ± 2.2% versus 89.2% ± 4.9% (P < 0.001)). However, the area recovered faster. The edema formation, as a parameter for endothelial integrity, was significantly more pronounced and lasted longer after frostbite, compared with the burn injury, and reached its maximum level on d 7 after trauma (162.4% ± 4.2% versus 142.% ± 5.9%; P = 0.007). In contrast to the rolling leukocytes, which showed the same increase on d 1 and then a subsequent decrease in both groups, the number of adherent leukocytes after the burn was markedly higher on d 1 (480% versus 167%; P = 0.001) but decreased much faster. The number of adherent leukocytes after frostbite remained significantly higher than those of the burn group during the entire observation. The comparison of analogous intravital burn and frostbite models indicates that despite the similarities, decisive microcirculatory differences in extension and recovery from these two types of thermal trauma exist.

Substitution of Hot-Gas Lateral Jets by Cold-Gas Jets in Supersonic Flows

C = wave celerity similarity number Cf = friction coefficient Cp = pressure coefficient Cp diff = differential pressure coefficient D = diameter of the body, m J = momentum flux similarity number JR = momentum flux ratio M = mass flux similarity number Mth = thruster ejection Mach number M1 = freestream Mach number NCR = nozzle celerity ratio NJR = nozzle momentum flux ratio NMR = nozzle mass flux ratio NPR = nozzle pressure ratio NrTR = nozzle temperature ratio P = pressure similarity number PR = total pressure ratio Pj = nozzle exit static pressure, Pa Po, P1 = freestream static pressure, Pa Pt = total pressure, Pa Pti = thruster stagnation pressure, Pa ReD = diameter-based Reynolds number rth = specific thruster gas constant, J kg 1 K 1 r1 = specific freestream gas constant, J kg 1 K 1 T = temperature similarity number Tj = nozzle exit static temperature, K Tt = total temperature, K Tti = thruster stagnation temperature, K T1 = freestream static temperature, K U = velocity component along the x axis, m s 1 Uo, U1 = freestream velocity component along the x axis, m s 1 uf = friction velocity component along the x axis, m s 1 W = velocity component along the mean ejection direction, m s 1 Wj = nozzle exit velocity component along the mean ejection direction, m s 1 x = horizontal coordinate along the body axis, m y = horizontal coordinate perpendicular to the body axis, m y = dimensionless wall distance z = vertical coordinate, m th = thruster gas isentropic coefficient 1 = freestream gas isentropic coefficient = kinematic viscosity, m s 1 = density, kg m 3 j = nozzle exit density, kg m 3 1 = freestream density, kg m 3 w = wall shear, Pa

Hot-Gas Side Jet in a Supersonic Freestream

The present paper reports on the interaction of a hot side jet in a supersonic freestream and compares the effects with results from cold-gas jet investigations. With high-speed schlieren videos, a significant enlargement of the separation area has been ascertained upstream from the hot-gas jet and quantitatively confirmed with wall pressure measurements. The schlieren videos also show a strong oscillation of the separation and bow shock. By using an algorithm that analyzes the similarity of neighboring images, the oscillation frequency of the separation and bow shock has been measured to be 11.3 kHz. As a consequence of the dominant shocks in the area in front of the jet, the hot jet plume is screened off strongly from the freestream, thus resulting in an upstream inclination. Finally, high-speed videos have revealed large-scale structures in the hot-gas jet and their convection velocities have been analyzed. According to the shocks, the large-scale structures oscillate at 11.3 kHz. Jet oscillation is thus excited by the interaction of the hot-gas jet with the freestream and not by resonances from the combustion chamber.

積極的COTSを導入した超小型推進系の開発とS-310-36号機による宇宙実証

The University of Tokyo, Kobe University and Vienna University of Technology conducted a set of experiments including large membrane “Furoshiki Satellite” extension and active phased array antenna operation in January 2006, by using ISAS/JAXA sounding rocket S-310-36, one of their purposes was to demonstrate a cold gasjet propulsion system for microsatellites which makes use of effective COTS. A series of verification tests concerning the propulsion were conducted on ground before the launch, and it resulted in confirmation of 70 seconds of specific impulse at 250mN of thrust with little leakage for 4 months and good resistance to vibration and shock environment of the launcher. Although specific impulse of the propulsion in orbit was not determined, the propulsion system worked very well and we acquired pressure history of its tank, and established the basis of moderate-priced propulsion system for microsatellites and are ready to salute the coming era of microsatellites equipped with propulsion.

1013 ワイヤアーク溶射における噴射ノズル形状の適正化 : 超音速ガスジェットを利用したワイヤアーク溶射装置の試作(G.S.7 加工工学)

1013 ワイヤアーク溶射における噴射ノズル形状の適正化 : 超音速ガスジェットを利用したワイヤアーク溶射装置の試作(G.S.7 加工工学)