Reentry Research Articles

Optimization of Mechanical Deployable Reentry Vehicle based on Multi-Fidelity Aerodynamic-Trajectory Coupling Model

As the aerospace industry continues to advance, the demand for round-trip transportation between Earth and space, as well as deep space exploration missions, is increasing. The mechanical deployable reentry vehicle, a complex multidisciplinary system, experiences parameter coupling between trajectory design and aerodynamic simulation. The calculation of trajectory and the design of aerodynamic layout directly impact the flight process. To address issues such as biased trajectory data obtained without considering disciplinary coupling and the high computational costs associated with overall aerodynamic layout optimization, this paper fully considers the impact of global aerodynamic drag on the flight trajectory. A multi-fidelity optimization model for reentry vehicles, named Multi-Fidelity Aerodynamics-Trajectory Coupling (MF-ATC), is proposed. The model uses a large number of low-accuracy model samples to control computational costs, without considering the coupling relationship, and a small number of high-accuracy model samples to ensure approximation accuracy, achieving fast and precise prediction of flight trajectories. The results demonstrate that the MF-ATC model improves trajectory prediction accuracy and efficiently accomplishes aerodynamic shape optimization, effectively enhancing the vehicle's performance. The model shows great potential for engineering applications.

Robust attitude control for hypersonic reentry vehicle via composite fixed-time stable control method

A novel adaptive nonsingular fixed-time converged terminal sliding mode control method is proposed for a standard nonlinear system suffering from uncertainties and disturbance. The obtained results are applied to attitude maneuver controller design for hypersonic reentry vehicles (HRV). First, an adaptive disturbance observer with fixed-time stability is introduced to cope with the total disturbance consisting of uncertainties and disturbance. Considering the singularity issue inherent in classical fixed-time converged terminal sliding mode, an improved nonsingular fixed-time terminal sliding mode(NFxTSM) is designed by implementing the switching function, ensuring faster convergence and singularity-free. The adaptive technique is also incorporated with the controller design to enhance the robustness of the NFxTSM. Then, considering the inherent time-scale separation feature, the composite attitude maneuver controller is further designed for HRV based on the backstepping technique. The outer loop generates the desired angle rate command, and the inner loop is designed to track the outer loop command. Finally, the numerical simulations are established to verify the effectiveness of the proposed controller.

Design and characteristic analysis of a high-performance deformable piezoelectric wind energy harvester based on coupled vibrations

The current vortex-induced vibration piezoelectric wind energy harvesters have a narrow operating wind speed range, while galloping piezoelectric energy harvesters are at risk of damage from excessive amplitude at high wind speeds, a novel high-performance deformable piezoelectric wind energy harvester based on coupled vibrations (DPWEH) has been proposed. The alteration of the compound blunt body shape effectively modifies the shedding characteristics and intensity of vortices, subsequently influencing the vibration mode and output voltage of the system. The vibration mode transitions from galloping to coupled vibration, ultimately to vortex-induced vibration. The rigid wing and long elastic beam suppress galloping at high wind speeds. A thinner flexible wing can extend the duration of coupled vibration. A smaller wing width ratio and larger Y-type base wing width are beneficial for increasing the output voltage. By optimizing the parameters of the compound blunt body, the onset wind speed can be effectively reduced, the effective wind speed bandwidth can be expanded, and the DPWEH can undergo coupled vibration for an extended duration while stably generating electricity. The peak output power is 0.36 mW at a load of 150 kΩ. Moreover, the energy harvester demonstrates the prolonged power generation capability of signal transmitters and 100 LED lights.

Development and demonstration of a two-color nitric oxide vibrational temperature diagnostic using spectrally-resolved ultraviolet laser absorption

Development of a new ultraviolet (UV) laser absorption diagnostic has enabled the probing of nitric oxide (NO) in the second excited vibrational state (v” = 2) for inferences of quantum-state-specific number density and vibrational temperature time-histories. Spectroscopic modeling informed the selection of the new 246.3222 nm wavelength, as this wavelength exhibits high sensitivity for thermometry in the 2000 – 8000 K temperature range. This 246.3222 nm absorption feature consists of contributions from the R12(24.5), R11(15.5), Q22(24.5), and Q21(15.5) transitions all originating in the v” = 2 state. Absorption cross-sections at this selected wavelength were measured in reflected shock experiments for sweeps of both wavelength and temperature. The wavelength sweep investigated cross-sections over a 246.3202 – 246.3246 nm range at 4590 K, and the temperature sweep measured cross-sections over a 2500 – 7500 K range at the peak of the absorption feature (246.3222 nm). Cross-section results agree with the Stanford NO gamma-band model to within ±5%, confirming the use of the model for subsequent thermometry studies. Thermometry was demonstrated in reflected shock experiments probing the vibrational relaxation and chemical reactions in 2% NO diluted in either argon (Ar) or nitrogen (N2). These experiments leverage previous UV laser absorption diagnostics that probe NO in the ground vibrational state (v” = 0) using the R11(26.5), R12(34.5), Q21(26.5) , and Q22(34.5) transitions near 224.8155 nm and the Q11(12.5) , R12(19.5) , P21(12.5) , and Q22(19.5) transitions near 226.1026 nm, which were studied in Ref. [1]. The combination of the new diagnostic wavelength with previously validated diagnostics yields low-uncertainty vibrational temperature time-histories that are in excellent agreement with previously inferred vibrational relaxation time results from Refs. [2] and [3]. Future work will apply this two-color nitric oxide vibrational temperature diagnostic to probe the vibrational temperature of NO formed in high-temperature, shock-heated air at conditions relevant to hypersonic and reentry vehicles.

Clinical presentation, investigation findings, and treatment outcomes of intraluminal small intestinal obstruction by bezoars and other materials in adult cows– a retrospective study of 110 cases

BackgroundSmall intestinal obstruction (SIO) is a blockage of the intestinal lumen by blunt foreign bodies, neoplasms originating from the intestinal wall or thick chyme. This study analysed the medical records (only data) of 110 cattle with SIO and described the clinical findings, treatment and outcome. These findings were compared between surviving and non-surviving cattle, and among the affected regions such as the duodenum, jejunum and ileum.ResultsColic occurred in 42.7% (47/110) of the cattle. Rumen motility was absent in all cattle and intestinal motility was reduced or absent in 82.6% (90/109). Ballottement and/or percussion and simultaneous auscultation were positive on the right side in 63.3% (69/109). Little or no faeces in the rectum occurred in 93.6% (102/109) of the cattle. Dilated loops of small intestines could be palpated transrectally in 46.8% (51/109) and the actual obstruction (palpated as a firm mass in the small intestine) in 5.5% (6/109) of the cattle. The main laboratory changes were hypokalaemia (80.9%, 89/110), hypermagnesaemia (75.3% 58/77), hypocalcaemia (71.8%, 56/78), haemoconcentration (66.4%, 73/110), azotaemia (66.4%, 73/110) and positive base excess (63.3%, 62/98). Abnormal ultrasonographic findings included dilated loops of small intestines (94.3%, 83/88) and subjectively reduced or absent small intestinal motility (85.4%, 70/82). The actual obstruction could be visualised in 3.4% (3/89) of the cattle by ultrasonography. In the 14 non-surviving and the 96 surviving cattle the frequencies of abdominal dilatation (57.1%, 8/14 vs. 22.1%, 21/95) and the presence of blood, mucus and/or fibrin in the rectum (92.9%, 13/14 vs. 63.2%, 60/95) were significantly different. Abomasal reflux syndrome was significantly worse in the cattle with duodenal obstruction (26/110) than in those with jejunal (51/110) or ileal obstruction (33/110). A total of 107 cattle underwent right flank laparotomy, and the obstruction was resolved by massaging the affected area or it was removed via enterotomy. Of the 110 cattle, 14 (12.7%) were euthanized and 96 (87.3%) were discharged 3 to 10 days after surgery.ConclusionsTransrectal and/or ultrasonographic diagnosis is the exception, and in almost all cases laparotomy, was required. The prognosis is good provided that surgical treatment is carried out promptly.

Autonomous numerical predictor-corrector guidance for human Mars landing missions

The numerical predictor-corrector guidance method with a linear bank angle parameterization has been widely applied to various atmospheric entry guidance problems. However, it has been found that the linear bank angle approach has limitations in satisfying the final state requirement of a specific type of atmospheric entry mission. In response, this paper proposes a novel bank angle parameterization based on a logistic function, which improves the energy preservation capability and increases the potential final altitude at the end of the entry phase. The paper also suggests a guideline to determine a guidance law activation point for better entry performance. Numerical simulations demonstrate that the proposed guidance scheme outperforms the linear bank profile approach and is suitable for future human Mars landing missions.

Superior Control of Spacecraft Re-Entry Trajectory

This paper focuses on the re-entry phase of lunar return spacecraft and addresses the design optimization of their re-entry trajectories in real-world conditions. Considering various constraints of re-entry flights, this study introduces a refined superior control theory, drawing from Xuesen Qian’s descriptions in engineering control theory, and presents a specific superior control algorithm. The designed superior control algorithm and the traditional weighted optimal control algorithm were employed to simulate the lunar return and re-entry processes. Two representative trajectories were selected for a comparative analysis to obtain various parameters. Results indicate that the trajectory optimized using the weighted optimal control algorithm can only ensure that multiple performance indexes are optimized according to preset weights but cannot achieve superior performance in all metrics. In contrast, trajectories optimized using the superior control algorithm effectively leverage the permissible floating range of performance indexes without exceeding the maximum limit, thereby ensuring superior performance in all metrics. This paper is the first to refine the superior control theory proposed by Xuesen Qian, to design a specific algorithm theory for superior control, and to apply it to aerospace re-entry trajectory optimization—providing a theoretical foundation for future non-weighted control algorithm developments.

Laboratory Simulations of Plasma Generated Around the Atmospheric Reentry Spacecraft

In this paper, plasma will be generated in a laboratory as a simulation of what happens to spacecraft when they enter the atmosphere of Earth. Parameters of plasma generation were determined in terms of pressures of 0.1, 0.2, 0.3, 0.4, and 0.5 mbar and generation energy 200 W. The parameters of the generated plasma were calculated using the optical emission spectroscopy two intensity ratio method, and the electron temperature, electron density, Debye length, and plasma frequency were calculated. Compare the results with the actual results, electron temperatures were 2.26–1.71 eV and plasma frequency 8.09 x1011-6.7x1011 at 0.1-0.5 mbar pressure.

A fully coupled multiscale phase-change model at the porous interface for transpiration cooling: coupling dynamics pore-scale networks to continuum-scale free flow

Being a promising method for thermal protection system, transpiration cooling has received wide interest recently. Numerical simulation for transpiration cooling, however, has been limited due to the mis-matching between the pore-scale two-phase flow and external high-temperature aerothermodynamic environment, which induced by conventional decoupled or iterative one-way coupled simplification methods. In this work, a fully coupled continuum-scale and pore-scale model is established for transient transpiration cooling at the interface between boundary layer flow and porous medium through coupling Computational Fluid Dynamics (CFD) and Pore-Network Model (PNM), termed as the multiscale CFD-PNM coupled method. The coupled method allows to capture detailed displacement and phase change of two-phase flow at pore-scale, revealing the strong interaction of the water vapor with the external free flow within a high temperature boundary layer. After successfully validating the new coupled model by comparing with the Two-Phase Mixture Model (TPMM) solution, a number of cases mimicking the cooling at the interface of typical blunt bodies are simulated. The results show that the multiscale CFD-PNM coupled method can not only provide the thermal protection effect prediction, but also reveal many critical features that beyond the reach of continuum-scale studies. Some pore-scale phenomena that are important to the overall transpiration cooling effects are revealed, including transient phase change and composition variation of water vapor, imbibition and drainage of two-phase flow related to pore-scale capillary thresholds and applied boundary pressures, as well as the two-way mass transfer at the interface, such as the invasion of external hot air.

Study on the aerodynamic characteristics of reentry capsule with obtuse head inverted cone under hypersonic chemical nonequilibrium flow

Abstract During spacecraft reentry, the aerodynamic characteristics of the reentry capsule with a sizeable obtuse head inverted cone (OBHIC) in a hypersonic state are the key factors in the design of controlled reentry trajectory, the design of trim angle of attack (AoA), and the accuracy of fall point of capsules. This paper establishes a numerical simulation algorithm of a hypersonic chemical nonequilibrium flow field by considering high-temperature real gas effects. The reentry capsule’s aerodynamic and flow field characteristics are predicted and analyzed. The component transport equations for chemical reactions are added to the Navier-Stokes equations, enabling precise modeling of gas molecule vibrational excitation and ionization processes. A half-model multi-block structured mesh is employed to construct the aerodynamic profile of the reentry capsule with OBHIC. The aerodynamic characteristics and pressure distribution of the reentry capsule were calculated and analyzed under the typical conditions of flight altitude of 40~80 km, flight velocity of 6~27 Ma, and AoA of 15°~24°. The results of the aerodynamic characteristics prediction show that the aerodynamic characteristics of the reentry capsule are little affected by the incoming flow velocity in a hypersonic state but significantly affected by the AoA. As the AoA increases, the lift coefficient CL increases linearly, the drag coefficient CD decreases linearly, the lift-to-drag ratio K rises linearly, and K increases from 0.19 to 0.29. In its hypersonic state, the reentry capsule exhibits a low lift-to-drag ratio, characterized by high drag and low lift coefficients. The results of this paper play an essential role in the reentry flight dynamics and reentry trajectory design of the reentry capsule. Moreover, it can further ensure the safety and reliability of the reentry flight of spacecraft.

Study on prediction method of controlled re-entry landing area of large spacecraft

Abstract The present paper proposes a calculation method for predicting the dispersion area of debris during the controlled re-entry of a large spacecraft, aiming to determine the controlled re-entry area accurately. This method involves analyzing the overall re-entry trajectory of the spacecraft as a priority, followed by ablation and disintegration analysis, and subsequently simulating the equipment-level trajectories of potential ground-falling components to obtain the final landing area envelope. Simulation results demonstrate that this approach effectively determines the controlled re-entry area, providing essential technical support for formulating implementation plans while ensuring safe and reliable reentries of large spacecraft into predetermined areas. Notably, this method has been successfully applied in previous missions such as Tianzhou-1 to Tianzhou 6 and can be further extended to subsequent controlled reentries involving Tianzhou-series cargo spacecraft and other low-orbit satellites.

Direct energy deposition of TiC/Ti6Al4V graded materials and heat resistance improvement during the ablation process

A reusable reentry vehicle requires a thermal protection structure with high strength and heat resistance for repeated traveling between the Earth and space. In this study, various transition modes of TiC/Ti6Al4V graded materials were designed and fabricated by direct energy deposition, and then ablation tests were conducted to simulate the service environment. The influence of microstructure morphology on the heat resistance of the graded materials was revealed by analyzing the changes in the internal microstructure, element distribution, and microcrack. Compared with Ti6Al4V titanium alloy, TiC/Ti6Al4V graded materials show almost no mass loss or ablation pits, indicating a significant improvement in heat resistance. The Ti6Al4V titanium alloy exhibited macroscopic cracks up to 700 μm in length on the surface after the ablation test; as a contrast, the surface area of the TiC/Ti6Al4V graded materials exhibited fine microcracks, and there were no significant changes in the internal structure. The improvement in the heat resistance of TiC/Ti6Al4V graded materials is attributed to the combined effects of the interface heat resistance between the TiC and Ti6Al4V and the change of heat conduction path within the matrix.

Machine learning-based quasi-optimal feedback control for a propellantless re-entry

Atmospheric re-entry includes all the activities ensuring the safety of individuals and ground assets, with potential implications for the controlled landing of humans and payloads on planetary surfaces. A robust system for controlled re-entry is imperative for space missions requiring the retrieval of samples. Initially developed for large vehicles, the re-entry technologies evolved to encompass compact capsules capable of retrieving small satellites on Earth, driven by the increasing interest in SmallSats. In this context, the current work proposes an aerodynamic-based approach to ensure an optimal controlled re-entry up to a desired target point in terms of altitude, latitude, and longitude. Furthermore, a novel closed-loop feedback control system based on Deep Neural Networks (DNNs) is proposed to face the unpredictable perturbations that can affect the re-entry. The aerodynamic force modulation can be accomplished by changing the aerodynamic angles. After an initial passive descent, a subsequent phase starts, during which active control is performed to ensure precise targeting. Formulated as a single-stage optimal control problem, the algorithm focuses on this second phase, exploiting the angle of attack and the bank angle as control variables to reach the desired target point in the minimum time. A set of 750 optimal control trajectories is generated to constitute the training set for the DNN. The successful outcome of the optimal control algorithm and the closed-loop feedback controller is demonstrated by different Monte Carlo analyses. The proposed work offers a noteworthy alternative for real applications, allowing propellantless devices to perform a safe and controlled re-entry.

Research on Load Correlation of Blunt Headed Aircraft

Abstract In order to study the influencing factors of static and dynamic loads on short blunt body balanced wing structures in the external atmospheric environment, and to avoid and prevent structural overload and damage, this paper conducted load tests on short blunt body structures and conducted load correlation analysis. This article establishes a dynamic load testing method for internal excitation and measurement, which is more suitable for dynamic load measurement of small structures compared to traditional wind tunnel testing techniques. On this basis, the influencing factors of dynamic loads were studied. By measuring and changing the Mach number, angle of attack, model frequency, and aerodynamic damping data of the model flight, the influence of the above variables on the static and dynamic loads of the model was obtained. The experimental results indicate that the established measurement technique can accurately and effectively obtain static and dynamic test results of the structure. Pneumatic damping is negatively correlated with dynamic loads, with a correlation coefficient of around -0.8. The Mach number and angle of attack are positively correlated with dynamic loads, with a correlation coefficient of around 0.98. This article establishes a new wind tunnel testing and measurement method, analyzes the influencing factors of dynamic loads, and is of great significance for dynamic load measurement and the design of new aircraft.

Effect of attack angle on the electromagnetic wave transmission characteristics in the hypersonic plasma sheath of a re-entry vehicle

The attack angle may greatly affect the hypersonic plasma sheaths around the re-entry vehicle, thereby affecting the transmission characteristics of electromagnetic (EM) waves in the sheaths. In this paper, we propose an integrated three-dimensional (3D) model with various attack angles and realistic flying conditions of radio attenuation measurement C-II (RAM C-II) re-entry tasks for analyzing the effect of the attack angle on the transmission characteristics of EM waves in the sheaths. It is shown that the electron density and collision frequency of the sheath on the windward side can be increased by an order of magnitude with the increase of the attack angle. Meanwhile, the thickness of the sheath on the leeward side is increased where the electron density and collision frequency are reduced. The EM waves are mainly reflected on the windward plasma sheath due to the cutoff effect, and the radio-frequency (RF) blackout is mitigated if the antenna is positioned on the leeward side. Thus, by planning the trajectory properly and installing the antenna accordingly during the re-entry, it is possible to provide an approach for mitigation of the RF blackout problem to an extent.

Triple-oxygen isotopes of stony micrometeorites by secondary ion mass spectrometry (SIMS): Olivine, basaltic glass and iron oxide matrix effects for sensitive high-mass resolution ion microprobe-stable isotope (SHRIMP-SI).

Micrometeorites are extraterrestrial particles smaller than ~2mm in diameter, most of which melted during atmospheric entry and crystallised or quenched to form 'cosmic spherules'. Their parentage among meteorite groups can be inferred from triple-oxygen isotope compositions, for example, by secondary ion mass spectrometry (SIMS). This method uses sample efficiently, preserving spherules for other investigations. While SIMS precisions are improving steadily, application requires assumptions about instrumental mass fractionation, which is controlled by sample chemistry and mineralogy (matrix effects). We have developed a generic SIMS method using sensitive high-mass resolution ion micro probe-stable isotope (SHRIMP-SI) that can be applied to finely crystalline igneous textures as in cosmic spherules. We correct for oxygen isotope matrix effects using the bulk chemistry of samples obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and model bulk chemical compositions as three-component mixtures of olivine, basaltic glass and Fe-oxide (magnetite), finding a unique matrix correction for each target. Our first results for cosmic spherules from East Antarctica compare favourably with established micrometeorite groups defined by precise and accurate but consumptive bulk oxygen isotope methods. The Fe-oxide content of each spherule is the main control on magnitude of oxygen isotope ratio bias, with effects on δ18O up to ~6‰. Our main peak in compositions closely coincides with so-called 'Group 1' objects identified by consumptive methods. The magnitude of SIMS matrix effects we find is similar to the previous intraspherule variations, which are now the limiting factor in understanding their compositions. The matrix effect for each spherule should be assessed quantitatively and individually, especially addressing Fe-oxide content. We expect micrometeorite triple-oxygen isotope compositions obtained by SIMS to converge on the main clusters (Groups 1 to 4) after correction firstly for magnetite content and secondarily for other phases (e.g., basaltic glass) in each target.

Influence of Silicon Carbide Incorporation on Thermal and Ablation Properties of Carbon Fabric-Phenolic Resin Composites

To shield re-entry spacecraft from the extreme heat experienced during hypersonic flight through a planet's or the earth's atmosphere, thermal protection systems (TPS) were developed. This work involved the fabrication of composites using a polyacrylonitrile (PAN) based carbon fabric (Cf)-phenolic resin matrix (PR) modified with different weight percentages (wt.%) of silicon carbide (SiC), namely 0 wt.% (Cf/PR), 1wt.%, 3wt.%, and 5wt.%. The composites were prepared using the hydraulic hot press method. The manufactured composites were analyzed for their thermal conductivity and resistance to ablation using an oxyacetylene torch test. Furthermore, the ablated composites underwent X-ray diffraction (XRD), revealing a SiO2 compound layer on the ablated composite surface. The experimental results demonstrated that the Cf/PR composites modified with 3wt.% of SiC exhibited superior characteristics. The composites consist of 3wt.% Cf/PR-SiC exhibited a thermal conductivity value of 0.57 W/m K. Additionally, these composites showed a noticeable decrease in the mass ablation rate (MAR) at 0.0052 mm/sec and linear ablation rates (LAR) at 0.025061 gm/sec. This study proposed an effective way to improve the thermal and ablation characteristics of TPS materials.

Evaluation of Reusable Thermal Protection System Materials Using a High-Velocity Oxygen Fuel Torch.

We studied a candidate TPS (thermal protection system) material for reusable re-entry space vehicle applications. The material was based on a high-temperature-resistant material called Cerakwool. A total of six specimens were fabricated with substrate densities of 0.45 g/cm3, 0.40 g/cm3, and 0.35 g/cm3, with two specimens for each density. All specimens were coated with high-emissivity TUFI (toughened unpiece fibrous insulation), with coating thicknesses ranging from 445 to 1606 µm. The specimens were tested using an HVOF (high-velocity oxygen fuel) material ablation test facility. For each density specimen pair, one specimen was tested at 1 MW/m2 and the remaining one was tested at 0.65 MW/m2. The average stagnation point temperature for specimens tested at 1 MW/m2 was ~893 °C, approximately 200 °C higher than those tested at 0.65 MW/m2. This suggests a ~200 °C increase in stagnation point temperature for a 0.35 MW/m2 rise in incident heat flux. During the tests, internal temperatures were measured at three locations. For all tested specimens, regardless of heat flux test conditions and density, the temperature at ~40 mm from each specimen's stagnation point remained around or below 50 °C, well within the 180 °C design limit set for the TPS back face temperature. Post-test visual inspections revealed no signs of ablation or internal damage, confirming the material's reusability.

Simulation and Experiments on Optimization of Vortex-Induced Vibration Power Generation System Based on Side-by-Side Double Blunt Bodies

In order to improve the utilization efficiency of converting low-flow current energy into electric energy for Reynolds number 10,000 ≤ Re ≤ 40,000, this paper proposes a vortex-induced vibration power generation system based on a side-by-side double blunt body. In this system, the side-by-side double blunt body structure is used in the current energy capture part to enhance the collection of low-flow current energy; the permanent magnet linear motor is used in the electric energy conversion part to improve the efficiency of electric energy conversion; and a laboratory device is constructed for testing. The effects of the blunt body structure parameters and the center spacing ratio on the energy harvesting performance of the system are qualitatively explained by constructing a simulation model. Compared with the single blunt body energy capture structure, the side-by-side double blunt body structure increases the vibration amplitude by 1.04 times and the lift by 1.14 times at the center spacing S/D = 2.4. Meanwhile, energy harvesting can be realized at a lower flow velocity, increasing the vortex-induced vibration’s energy capture range. Finally, the power generation system was experimentally verified in the laboratory, and the results showed that the vibration amplitude of the double blunt body structure was increased by 1.12 times compared to the single blunt body. The maximum output power of the generator is 10.55 W when the water velocity is 0.7 m/s. The energy conversion efficiency of the power generation system can reach a maximum of 52.93%, which is 12.33% higher than that of a single blunt body structure, which proves that the system has a higher power conversion efficiency than that of a conventional single conversion system.

Multiphysical description of atmospheric pressure interface chemical ionisation in MION2 and Eisele type inlets

Abstract. Chemical ionisation inlets are fundamental instrument components in chemical ionisation mass spectrometry (CIMS). However, the sample gas and reagent ion trajectories are often understood only in a general and qualitative manner. Here, we evaluate two atmospheric pressure interface chemical ionisation inlets (MION2 and Eisele type inlet) with 3D computational fluid dynamics physicochemical models regarding the reagent ion and sample gas trajectories and estimate their efficiencies of reagent ion production, reagent ion delivery from the ion source volume into the ion–molecule mixing region, and the interaction between reagent ions and target molecules. The models are validated by laboratory measurements and quantitatively reproduce observed sensitivities to tuning parameters, including ion currents and changes in mass spectra. The study elucidates how the different transport and chemical reactions proceed within the studied inlets, where space charge can already be relevant at ion concentrations as low as 107 cm−3, and compares the two investigated inlet models. The models provide insights into how to operate the inlets and will help in the development of future inlets that further enhance the capability of CIMS.