Rocket Exhaust Research Articles

Generalized inverse matrix - long short-term memory neural network data processing algorithm for multi-wavelength pyrometry.

The data processing of multi-wavelength pyrometry (MWP) is faced with the problem of solving N equations and N+1 unknown underdetermined equations. The traditional iterative optimization methods are difficult to meet the actual measurement requirements in terms of accuracy and efficiency. With the development of artificial intelligence technology in the field of data processing, it is expected to solve this problem. A generalized inverse matrix (GIM) is combined with a long short-term memory (LSTM) neural network algorithm for data processing of MWP is proposed, which emissivity influence is dispensed completely. Firstly, GIM is used for classification of the emissivity. Furthermore, inputting to the LSTM network not only ensures the accuracy of temperature measurement but also greatly improves the efficiency. The simulation results demonstrated that the accuracy of the GIM-LSTM algorithm was superior to that of the GIM-EPF and BP methods. After random noise was added, the relative error was still less than that for the GIM-EPF and BP methods, and the algorithm exhibited excellent anti-noise performance. Publicly available temperature data for the exhaust plume of a rocket engine were processed by the GIM-LSTM method, and the average relative error was less than the traditional method. Especially, in terms of inversion speed, the operational time of the GIM-LSTM algorithm was at the millisecond level, which is of great significance for the real-time monitoring of rocket exhaust plumes. The proposed GIM-LSTM data processing algorithm affords high accuracy and speed and is suitable for practical measurement of high-emissivity objects in real-time via MWP.

Annular Dump Diffuser and Deswirl System for Back-Pressure Control in Engine-Scale Transonic Annular Cascade

Abstract A common requirement for turbomachinery testing facilities is the ability to independently control Mach number and Reynolds number. In practice, this means independent control of the inlet total pressure and exit static pressure in a test facility. In this paper, we present a solution to this problem with particular applicability to large-scale annular test facilities. We describe the design and commissioning of a combined annular dump diffuser and deswirl system for back-pressure control in environments with high-whirl transonic flow. The particular application was an annular cascade of nozzle guide vanes from a current civil engine. The purpose was to provide independent control of Mach number and Reynolds number, by controlling the back-pressure in the intermediate annular plenum which forms the dump diffuser. The dump diffuser is necessary to facilitate optical and probe access (without interaction effects) and to reduce the risk of exit static pressure disturbances (due to particular duct design). The system has been installed and validated in the engine component aerothermal (ECAT) facility at the University of Oxford. In this implementation of the system, the high-whirl transonic flow from the nozzle guide vanes passes through a short, parallel annular duct, and is dumped into an annular plenum, before being re-accelerated into a deswirl vane ring. The deswirl ring turns the flow to the axial direction. The flow is then discharged through a variable choke plate into a silencer. Conditioning the flow to have zero whirl at the choke plate reduces the sensitivity of the choke plate effective blockage to the whirl angle. The design, deswirl vane aerodynamic performance, and overall system performance are assessed with detailed experiments and 3D unsteady computational fluid dynamics predictions. The control of high-whirl transonic flow is notoriously challenging, and the deswirl system has application to exhaust conditioning in a number of applications including annular cascade experiments and rocket turbo-pump exhaust systems.

Underexpanded gas jets of Mach 2: the changing physical structure and power transmission

ABSTRACT Supersonic jets with excess gas pressure are associated with many phenomena including radio galaxies, protostars, volcanic plumes, rocket exhausts, and champagne cork popping. Some common properties are derived here based on steady uniform hydrodynamic flow from a circular orifice. We present a systematic numerical study over a wide range of parameters for Mach 2 jets, concentrating on simulations of jets with pressures exceeding the ambient pressure. With cylindrical symmetry, we show how the location of the stand-off and following downstream shocks depend not only on the overpressure but also on the density due to a feedback loop, which results in an oscillatory flow pattern. We conclude that rapidly varying and gradually evolving shock patterns arise even from steady uniform jets. This can take the form of turbulent plumes at high overpressures and regular oscillations at low overpressures. We identify where this screeching contributes to noise and sound wave generation, which may aid the regulation of star and galaxy formation. However, the main effect for such low Mach number jets is to drive a circulatory motion in which the ambient medium is driven out along the axial direction while mass and energy flow laterally inwards, setting up a large advection pattern. Once the initial bow shock has propagated out, the noise from the jet is insufficient to significantly alter the environment. High Mach number jets do not follow these conclusions and will be treated separately.

Mineralogy and regolith maturity at the Chang'E-5 landing site inferred from the Lunar Mineralogical Spectrometer

Chang'E-5 (CE-5) landed in the northeast of the Oceanus Procellarum and successfully returned ∼1.73 kg lunar samples from a distinctively young mare basalt unit. The reflectance spectra between 0.45 μm to 3.20 μm at the landing site were acquired by the onboard Lunar Mineralogical Spectrometer before and after the sampling. The results from the spectral parameter analysis show the regolith is dominated by clinopyroxene, consistent with both orbital observations and laboratory analyses of the returned CE-5 samples. Optical maturity (OMAT) of regolith in the landing region of CE-5, Chang'E-4 (CE-4), and Chang'E-3 (CE-3) was analyzed, and the results show that the regoliths at CE-5 and CE-3 sites sitting on the ejecta blanket of the relatively young impact craters are both less mature than that at the CE-4 landing site. The OMAT and estimated content of submicroscopic metallic iron (SMFe) in the regolith show no obvious variations between the rock-shielded and unshielded regolith during the CE-5 descent, indicating the disturbance from rocket exhaust did not affect regolith maturity. Similar results on the effects of rocket exhaust were obtained from analyzing the regolith maturity along the CE-4 rover's traverse. Additionally, the surficial regolith and the scooped underlying layer in the centimeter-depth at CE-5 landing area exhibit similar maturities, suggestive of rapid gardening despite the geologically young age of the region. The results presented in this work shed light on the regolith evolution on the Moon and provide vital geological context for the analysis of the returned CE-5 samples.

Mie–Debye–Monte Carlo Method to Analyze the Transmission Characteristics of Electromagnetic Waves in Dusty Plasma

Dusty plasma environments, such as aircraft sheaths and rocket exhaust plumes, significantly affect the propagation of electromagnetic (EM) waves. In this study, the Mie theory and the dyadic Green method were used to calculate the Mie scattering cross section, Debye scattering cross section of the surrounding Debye cloud, and Mie–Debye coherence cross section formed by the two scattering fields. We propose that the Mie–Debye model should be regarded as a whole particle, and the dusty plasma can be simplified by assuming that it is composed of Mie–Debye spherical models of different densities. These assumptions were combined with the scattering characteristics of the microscopic Mie–Debye model and Monte Carlo method to analyze the propagation characteristics of EM waves in dusty plasma.

Using 3D Ray Tracing Technology to Study the Disturbance Effect of Rocket Plume on Ionosphere

In this paper, the initial neutral atmospheric parameters, background ionospheric parameters and geomagnetic field parameters of the ionosphere are obtained by NRLMSISE-00 model, IRI-2016 model and IGRF-13 model, respectively. Considering the neutral gas diffusion process, ion chemical reaction and plasma diffusion process, a three-dimensional dynamic model of chemical substances released by rocket plume disturbing the ionosphere is constructed. The influence of the disturbance on the echo path of high frequency radio waves with different incident frequencies is simulated by using three-dimensional digital ray-tracing technology. Using this model, the process of ionospheric disturbance caused by the main chemical substances H2 and H2O in the rocket plume under three different release conditions: fixed-point release at 300 km, vertical path at 250–350 km and parabolic path at 250–350 km, and the influence of the ionospheric cavity on the radio wave propagation of high frequency radio waves at different frequencies are simulated. The main purpose of the article is to focus on the effect of the cavity generated by the rocket exhaust on the propagation of radio waves. It mainly studies the perturbation effect on the ionosphere under different release conditions, considers the neutral gas diffusion process, ion chemical reaction and plasma diffusion process, and establishes the three-dimensional dynamics of the ionospheric electron density and the spatiotemporal distribution of the plume plasma learning model. Finally, the three-dimensional ray-tracing algorithm is used to simulate the propagation path of the radio wave through the disturbance area. We considered three different release conditions, including fixed-point release, vertical path and parabolic path. The ionospheric disturbances produced by these different releases are compared and analyzed, and their effects on the propagation path of radio waves are studied.

Numerical Simulation of Ionospheric Disturbances Due to Rocket Plume and Its Influence on HF Radio Waves Propagation

In this paper, the ionospheric disturbances of CO2, which is released by rocket exhaust plumes, was simulated. The effect of this disturbance on the propagation of high-frequency (HF) radio waves at different incident frequencies was also simulated by using three-dimensional digital ray tracing technique. The results show that CO2 can effectively dissipate the background electrons and form ionospheric holes after being released in the ionosphere. At the peak height of ionospheric electron density (about 300 km), the electrons are dissipated fastest and the radius of ionospheric hole is also largest. This is due to the fact that the diffusion coefficient of CO2 usually increases with height while the electron density just increases before reaching its peak height and then decreases with height, and the chemical reaction rate between ions and CO2 also becomes largest at the peak height of electron density (about 300 km). Around 100 s after the release of CO2, when the radio waves at a frequency of 8 MHz pass through the ionosphere with an elevation range of 85~95°, the “secondary focusing effect” can occur, and we believe that this is due to the reflection of HF shortwaves on the walls of the ionospheric holes. With time going on, this phenomenon disappears at 300 s and only one focus is left at this time. For the HF shortwaves at same incident frequency, the focusing effect of waves displays a weakening trend with time increasing, and the height of focus center also ascends gradually. At the same time after CO2 releasing, with the increasing of radio waves frequency, the focusing effect also becomes weaker and the focus center displays an ascending trend.

Narrow-band infrared radiation characteristics of rocket exhaust plume by using correction function related to thermodynamic state

Modeling of plume infrared radiation requires the accurate calculation of gas radiation properties of the plume non-uniform flow field. Aiming at the problem that the Curtis-Godson approximation (CGA) method can give the exact result in the limits of weak lines and strong lines, but overestimates the absorption of the optical intermediates path. This study develops an accurate model to study the infrared radiation of rocket plume. This model calculates narrow-band radiation properties using an equivalent half-width corrected by a correction function, which relates to the thermodynamic state of the no-uniform plume and is followed by radiative transfer calculations. Several Lorentz single lines were adopted to evaluate this correction function by the equivalent width of a fictitious non-uniform gas column, results showed high accuracy, especially at optical intermediates. Simulation of plume reaction flow was implemented by a refined 11-species, 17-reaction chemistry scheme, which can describe the afterburning between the multi-component fuel injected from the nozzle and ambient air. Then, adopting the temperature, pressure and radiating species distribution of the plume flow field, the model can predict accurate spectra that fit the experimental spectrometer data well. Finally, the effects of propellant formulation and flight conditions on plume infrared radiation were investigated: (a) hydroxyl-terminated polybutadiene (HTPB) and nitrate ester plasticized polyether (NEPE); (b) flight altitude; (c) flight Mach number. Results show that the composition of the propellant has a significant effect on the plume afterburning, NEPE plume afterburning effect is stronger, and the total radiation intensity is 61.5% higher than HTPB in 1.5–6.0 μm. The increase of flight altitude weakens the radiation, while due to the expansion of the radiant area, the spectral radiation intensity increases significantly. With the increase of Mach number, the band intensity decreases exponentially, and the plume structure gradually develops into a slender shape, the radiation decreases significantly. The research has significance for the application of target early warning, detection and identification.

LARGE-SCALE REDUCTIONS IN THE ELECTRON DENSITY OF IONOSPHERIC F-REGION, OBSERVABLE ALONG ROCKET TRAJECTORIES AT LAUNCH

Purpose. The object of the study are electron density depletions (‘holes’) occurring in the ionospheric F-region under the action of rocket exhaust products. The purpose is to present and discuss the results of observations concerning the ionospheric holes that were detected in the course of a number of launches of medium-lift Kosmos vehicles from the Kapustin Yar spaceport. Nei- ther that cosmodrome, nor the rocket type had been subjects of similar analysis before. Design/methodology/approach. The observations at the Kapustin Yar cosmodrome were performed with a portable vertical Doppler sounder. The beats between a reference signal and the one reflected from the ionosphere were subjected to spectral analysis, which allowed identifying the principal mode of the Doppler frequency shift and establishing time dependences of that frequency shift. An ionosonde located nearby was used for monitoring the underlying state of the ionosphere. Findings. The measurements performed with the vertical Doppler sounder near the launch site of the medium-lift Kosmos rocket have allowed obtaining first estimates for the principal parameters of the ionospheric holes arising in the F-region along the vehicle trajectory, as well as for the accompanying quasi-periodic variations in the electron density. The spatial scale sizes of the holes have been found to be in excess of 300 km, while the electron density reductions may attain » 50 %. These results are in agreement with the data obtained by international researchers for effects from heavy- and super heavy-lift launch vehicles. Also, note that the types of propellant differed significantly. The propagation velocity of the hole’s front edge was estimated to be » 140 m/s. The hole formation was accompanied by quasi-periodic variations in the Doppler frequency shift as a result of radar signal scattering from the electron density fluctuations produced by propagating atmospheric gravity- and infrasonic waves. The atmospheric gravity waves showed periods in the range from 7 to 20 minutes, and the infrasonic waves had a period close to 2 min. The amplitudes of quasi-periodic electron density variations were estimated for the two modes to be » 0.3 ¸1.5 % and » 0.02 ¸ 0.03 %, respectively. Conclusions. Medium-lift launch vehicles (mass of a few hundred tons) are capable of forming ionospheric ‘holes’ of several hundred kilometers in size and of reducing the electron density in the F-region by a factor greater than 2.

Active Precipitation of Radiation Belt Electrons Using Rocket Exhaust Driven Amplification (REDA) of Man-Made Whistlers.

Ground‐based very low frequency (VLF) transmitters located around the world generate signals that leak through the bottom side of the ionosphere in the form of whistler mode waves. Wave and particle measurements on satellites have observed that these man‐made VLF waves can be strong enough to scatter trapped energetic electrons into low pitch angle orbits, causing loss by absorption in the lower atmosphere. This precipitation loss process is greatly enhanced by intentional amplification of the whistler waves using a newly discovered process called rocket exhaust driven amplification (REDA). Satellite measurements of REDA have shown between 30 and 50 dB intensification of VLF waves in space using a 60 s burn of the 150 g/s thruster on the Cygnus satellite that services the International Space Station. This controlled amplification process is adequate to deplete the energetic particle population on the affected field lines in a few minutes rather than the multi‐day period it would take naturally. Numerical simulations of the pitch angle diffusion for radiation belt particles use the UCLA quasi‐linear Fokker Planck model to assess the impact of REDA on radiation belt remediation of newly injected energetic electrons. The simulated precipitation fluxes of energetic electrons are applied to models of D‐region electron density and bremsstrahlung X‐rays for predictions of the modified environment that can be observed with satellite and ground‐based sensors.

Radiation Belt Electron Acceleration Driven by Very‐Low‐Frequency Transmitter Waves in Near‐Earth Space

AbstractWe perform two‐dimensional Fokker–Planck diffusion simulations to quantify the role of Very‐Low‐Frequency (VLF) transmitter waves and other naturally occurring plasma waves in electron acceleration over L = 1.5–3.0. VLF transmitter waves play a dual role in electron acceleration at higher energies from ∼200 to ∼700 keV through energy diffusion, and losses at lower energies below ∼100 keV through pitch angle scattering. Due to the now‐achievable rocket exhaust driven amplification (REDA) of VLF waves suggested by recent studies, control of wave‐induced acceleration can be actively tested with various VLF wave intensities in space. With amplification by a factor of 5, the acceleration by VLF transmitters can overcome the losses by lightning‐generated whistlers and plasmaspheric hiss, leading to net acceleration in the combined scattering. The acceleration occurs within 1 min with amplification factor of 50 dB, which is promising to be observable in the future REDA experiment, representing a feasible test of the theory.

Atmospheric pollution from rockets

We address the impact of rocket exhaust gases on atmospheric pollution through high-resolution computational fluid dynamics simulations. We have modeled the exhaust gases and developing plume at several altitudes along a typical trajectory of a standard present-day rocket, as a prototypical example of a two-stage rocket to transport people and payloads into Earth's orbit and beyond. The modeled rocket uses RP-1 as the propellant and liquid oxygen as the oxidizer to generate ∼6806 kN of thrust via a total of nine nozzles, matching—as closely as possible based on available data—the specifications to the Thaicom 8 launch mission of the Falcon 9 rocket manufactured by SpaceX. We have used high-order discretization methods, 11th-order accurate, in conjunction with implicit large eddy simulations to model exhaust gas mixing, dispersion, and heat transfer into the atmosphere at altitudes up to 67 km. We show that pollution from rockets should not be underestimated as frequent future rocket launches could have a significant cumulative effect on climate. The production of thermal nitrogen oxides can remain considerable up to altitudes with an ambient atmospheric pressure below but of the same order of magnitude as the nozzles exit pressure. At the same time, the emitted mass of carbon dioxide in the mesosphere is equivalent to that contained in 26 km3 of atmospheric air at the same altitude.

Comparison of rocket launch data to empirical models for overall level and peak directivity angle

With increasing frequency in global rocket launches, it is important to assess the effects of liftoff noise. Understanding of the fundamental physics of the sound radiation from rocket exhaust plumes remains limited. Some empirical predictive models, derived from plume parameters, cover aspects of the sound radiation, such as convective Mach number, peak directivity angle, and overall sound pressure level in the direction of maximum emission. These are evaluated using high-fidelity noise data from a number of different launches from Vandenberg Space Force Base. Initial results of the model comparisons will be presented.

Cooling rocket nozzle extensions with supersonic gas injection

Supersonic helium injected into the rocket exhaust boundary layer protects components from extremely hot gas.

Modeling high-speed gas–particle flows relevant to spacecraft landings

The interactions between rocket exhaust plumes and the surface of extraterrestrial bodies during spacecraft landings involve complex multiphase flow dynamics that pose significant risk to space exploration missions. The two-phase flow is characterized by high Reynolds and Mach number conditions with particle concentrations ranging from dilute to close-packing. Low atmospheric pressure and gravity typically encountered in landing environments combined with reduced optical access by the granular material pose significant challenges for experimental investigations. Consequently, numerical modeling is expected to play an increasingly important role for future missions. This article presents a review and perspectives on modeling high-speed disperse two-phase flows relevant to plume–surface interactions (PSI). We present an overview of existing drag laws, with origins from 18th-century cannon fire experiments and new insights from particle-resolved numerical simulations. While the focus here is on multiphase flows relevant to PSI, much of the same physics are shared by other compressible gas–particle flows, such as coal-dust explosions, volcanic eruptions, and detonation of solid material.

Coordinated Observations of Rocket Exhaust Depletion: GOLD, Madrigal TEC, and Multiple Low‐Earth‐Orbit Satellites

AbstractA plasma density hole was created in the ionosphere by a rocket launch from Cape Canaveral, Florida near local sunset on 30 August 2020, which is called rocket exhaust depletion (RED). The hole persisted for several hours into the night and was observed in total electron content (TEC) maps, the Global‐scale Observations of the Limb and Disk (GOLD) imager, and multiple low‐earth‐orbit satellites. The RED created a nightglow pit in the GOLD 135.6 nm image. Swarm satellites found that the RED exhibited insignificant changes in electron/ion temperature and field‐aligned currents. On the other hand, magnetic field strength was enhanced inside the RED by a few tenths of a nanotesla. Assimilation data products of the Constellation Observing System for Meteorology, Ionosphere, and Climate 2 (COSMIC‐2) mission reveal that ionospheric slab thickness increased at the center of the RED, which is supported by combined analyses of the GOLD and TEC data. The RED did not host conspicuous substructures that are stronger and longer‐lasting than the ambient plasma did.

A Study of Rocket Exhaust Plume in the Lower Atmosphere using Geo-Imaging High Resolution Camera (GHRC) On-board Indian Geostationary Satellite

A Study of Rocket Exhaust Plume in the Lower Atmosphere using Geo-Imaging High Resolution Camera (GHRC) On-board Indian Geostationary Satellite

The incoherent scattering of dust plasma produced by solid rocket exhaust

When the space shuttle passes though the ionosphere, the plume provides a high-speed neutral gas compared to the surrounding plasma. Simultaneously, the exhaust molecules exchange charge with the ambient O+ ions in the ionosphere, producing a ring-beam ion distribution(bump-on-tail distribution), which has an important effect on incoherent scattering radar(ISR) spectrum. Based on the theory of incoherent scattering of dust plasma, the incoherent scattering characteristics of the bump-on-tail distribution in the early stage of solid rocket exhaust are simulated. The influences of dust component and plasma distribution on the incoherent scattering spectrum are analyzed, and the mechanism of the influence is initially explained. The results show that the addition of dust enhances the ion spectrum, and the influence of distribution function on the ion spectrum is closely related to the resonant frequency of the generated plasma. The research on ISR characteristics of the plasma distributions is important to understand the physics of both nature and artificial plasma.

Analysis for design optimization of high thrust liquid engine hot test facility

A high thrust liquid oxygen-kerosene fuelled engine is being developed for future launch vehicle applications. Comprehensive hot testing of engine at sea level conditions is required for qualification and acceptance of flight engine and launch vehicle stage. The engine and stage will be tested in a specialized rocket engine and stage hot test facility which deflects the flame safely to avoid any hazard to engine and adjoining mechanical structures. The facility is equipped with water jets to sufficiently cool the rocket plume before impinging on deflector pit walls. The high temperature and high-pressure rocket exhaust jet is cooled with sufficient quantity of water to maintain the impingement wall temperature within safe working limits.In this study, a multi-phase computational fluid dynamics (CFD) methodology is developed for design of water-cooling jet configuration of deflector facility. Multi-phase model validation study using full phase treatment and droplet assumption for water injection is performed prior to water jet optimization analysis of high thrust LOX-kerosene test facility. Validation studies based on simulation and analysis of existing test stand is developed. A discrete particle (DPM) based two phase methodology is chosen to model water injection in RANS framework. The optimum cooling configuration is determined iteratively through numerous multi-phase simulations. The multi-phase analysis showed ineffectiveness of initial water injection scheme which results in facility wall temperature above safe limit. A multi-plane water injection scheme is devised there on with provision of water injection at two axial locations from the nozzle exit. A detailed parametric multi-phase analysis is carried out for design optimization of multi-plane water injection scheme and to determine thermal condition of the test facility. Analysis showed effective rocket plume cooling and lower facility wall temperature with two plane water injection schemes in comparison to initial single plane design configuration. The study highlights the role of CFD based methodology to formulate an engineering solution for design optimization of LOX-kerosene engine hot test facility.

Simulation of ionospheric depletions produced by rocket exhaust restricted by the trajectory

The rocket exhaust, as a source of the disturbance, provides a way to examine physical and chemical phenomena in the ionosphere. Since the disturbance morphological characteristics are closely related to rocket orbit, the ionospheric perturbation produced by the rocket exhaust considering the trajectory effect is simulated. The three-stage booster rocket trajectory is calculated, considering multi-stage thrust, aerodynamic drag, gravity and apparent force. Based on trajectory calculation and the electron density depletion theory of neutral gas injected into ionosphere, the exhaust is divided into a series of mass elements released at different time and different positions along the trajectory. The theory considers the charge exchange between the ambient O + ions and the high-speed exhaust molecules (primarily H 2 O) in the exhaust plume. The simulation results show that the depletion structure restricted by the trajectory are dramatically different from the structure produced by a point source release, meaning that it no longer appears as an isotropic quasi-symmetric distribution, but the overall orientation of the depletion structure is consistent with the trajectory direction. Furthermore, the ray tracing technique is used to simulate the propagation of radio waves passing through the depletion structures. Due to the steepness of the depletion boundary and the difference in the shape of the boundary, the “focusing” effect of the rays which though the disturbance structure restricted by the trajectory disappear. These characteristics results can be an important reference for rocket detection and identification.