Dinitrogen Tetroxide Research Articles

Analysis of unstable combustion caused by the Gas–Liquid two-phase flow in small hypergolic propellant engines

Hypergolic bipropellant engines are extensively used in spacecraft operations. In these engines, the combustion reaction is initiated by the impinging jets of the oxidizer and fuel in the liquid phase. The most commonly used hypergolic fuels, hydrazine and monomethylhydrazine, as well as the oxidizer, nitrogen tetroxide, are all in liquid state under room temperature and atmospheric pressure conditions. However, as these engines are operated in a space vacuum, a portion of the propellant inevitably evaporates because of low-pressure boiling immediately after engine start-up. The mixing of gas with liquid propellant results in unstable combustion, and minimizing this effect is critical for the engine design. Particularly, preventing high-frequency combustion instability is essential as it can be detrimental to the engine. This paper presents a mechanism that activates high-frequency combustion instability, realized by analyzing the pressure within the combustion chamber during artificially induced unstable combustion. Furthermore, the methodology for establishing operational constraints based on the proposed mechanism is clarified, along with the method for collecting test data. The study findings provide important indicators for the design criteria of bipropellant engines, contributing to the diversification and complexity of space development programs.

Forecast of emergency situations with the spillage of liquid rocket fuel components in the territory for the disposal of chemically hazardous substances

Introduction. Liquid fuel includes two main components – fuel and oxidizer. Common liquid rocket fuels components are highly toxic compounds – heptyl (asymmetric dimethylhydrazine) and amyl (nitrogen tetraoxide). The calculation of emergency scenarios with the spill of liquid rocket fuel components on the terrain is intended for operational forecasting of the scale of pollution, optimization of work in the zone of chemical contamination and the development of a system for providing medical care to the population in case of an extreme situation. Material and methods. The article presents scenarios of emergency situations with the spill of liquid rocket fuel components on the territory of chemically hazardous facilities and during transportation. Results. The calculation of the distribution of approximate concentrations at spills in an open area of nitrogen tetroxide (NT) and asymmetric dimethylhydrazine (UDMH) is investigated. The received scenarios of emergency situations indicate the possibility of distribution of toxic concentrations: at the level of CL50 within 1 km at the UDMH spill from 0.5 to 10 tons, NT – from 0.1 to 5 tons; at the level of 1/10 CL50 – threshold toxodose (concentration) at a distance of 0.5–0.7 km at the UDMH spill 0.5–1.0 t, and NT – up to 1 t. Limitations. When studying emergency scenarios with the spillage of liquid rocket fuel components in the territory, an assessment was made of the distribution of approximate concentrations of components according to the regulatory document on the methodology for predicting the extent of contamination of highly toxic substances in accidents (destruction) at chemically hazardous facilities and transportation. Conclusion. As a result of the study, it was revealed that the population living within a radius of more than 2 km from the accident site may suffer from the spread of liquid rocket fuel components, which depends on the volume of the spill, the type of emergency hazardous chemicals and the wind direction in the chemical damage zone.

Consideration of fuel and oxidizer combinations for mass and volume limited hybrid rocket motors

AbstractThis research considers different storable oxidizer and fuel combinations for hybrid propulsion, looking for the most adequate candidates for mass and volume limited systems. High specific impulse Isp is the main indication for minimum mass, whereas high density specific impulse ρIsp is a good measure for smaller volume. Other aspects such as safety, handling, toxicity, burn rate, hypergolicity, and the oxidizer to fuel O/F ratio, may affect the final choice of propellant ingredient combination. For mass‐limited systems hydrogen peroxide H2O2 or nitrogen tetroxide N2O4 (the latter is toxic and hard to handle) oxidizers give the best results with most solid fuels (mainly hydroxyl‐terminated polybutadiene HTPB). For volume‐limited systems the same combinations may apply; however, in that case polyester fuel may be an adequate choice as well because of its high density. Nitrous oxide N2O is the most inadequate oxidizer for volume‐limited systems, yielding ρIsp lower by about 40 % compared to other oxidizers. Reducing the structure and insulation mass may result from decreasing the high‐pressure, high‐temperature section (the combustion chamber) and can be achieved from high O/F combinations employing N2O or H2O2 oxidizers. N2O gives relatively safe system, H2O2 enables hypergolic combinations, HNO3 is good for long‐term storage, whereas paraffin wax and expandable graphite additive yield high fuel regression rate and thrust. Overall, H2O2 oxidizer seems optimal for many operational aspects, but it should be chemically stabilized to minimize decomposition.

A case of acute inhalation dinitrogen tetroxide poisoning

Dinitrogen tetroxide is often used as an oxidant in rocket propellant and has strong irritant and corrosive properties. This paper analyzes the clinical data of a patient with dinitrogen tetroxide poisoning admitted in the 63710 Army Hospital of Chinese People's Liberation Army, so as to further explore the poisoning mechanism, clinical characteristics and key points of acute inhaled dinitrogen tetroxide poisoning.

Investigating the potential of carbon nitride as a new sensing material for NOx (N2O, N2O3, N2O4, and N2O5): a DFT study

Herein, DFT study was used to investigate the carbon nitride C6N8 as a potential detector of noxious gases, specifically nitrous oxide (N2O), dinitrogen tri-oxide (N2O3), dinitrogen tetra-oxide (N2O4), and dinitrogen penta-oxide. (N2O5). The Physiosorption process was notified after the adsorption of N2O (−12.6463 kJ mol–1), N2O3 (−40.1466 kJ mol–1), N2O4 (−23.8512 kJ mol–1), and N2O5 (−29.7947 kJ mol−1) on C6N8. The adsorption behavior shows weak interactions in the complexes which depicts the stability trend as N2O3@C6N8 > N2O5@C6N8 > N2O4@C6N8 > N2O@C6N8. Various analyses and techniques were employed to evaluate the sensing capability. Electronic parameters such as FMO, ELF, NBO, UV-visible spectrum, and DOS were performed to notify the detectable change in the sensing surface after the adsorption of the gases being studied. The existence of non-covalent interactions was confirmed by Symmetry Adopted Perturbation Theory (SAPT0), QTAIM, NCI, and IRI plots. Moreover, SAPT0 confirmed the greater contribution of Edispersion in N2O@C6N8. ESP (MEPs) visualization confirmed the interactions, as the nitrogen atoms of the surface are electron dense regions for the analytes to attack. Chemical stability and selectivity were evidenced by the stability parameters and the formation of new states in the DOS spectrum, respectively. Significant recovery time performance was observed after evaluating the recovery of analyte@C6N8 complexes at an appropriate temperature. These results suggest C6N8 theoretically as a potentially active sensing surface and it will enhance the interest of the experimental researchers in fabricating a sensing device using this material for the determination of even minute concentrations of the toxic gases.

Understanding the thermodynamic effects of chemically reactive working fluids in the Stirling engine

The Stirling engine, renowned for its high theoretical efficiency, is capable of partaking an active role in the current energy transition. Given its closed-cycle operation, the choice of the working fluid is pivotal in designing the Stirling engine. Dinitrogen tetroxide N2O4 has been extensively investigated in the past, based on the ideal gas thermodynamic model, as a chemically reactive working fluid for Stirling cycles. This molecule reversibly and rapidly dissociates into nitrogen dioxide NO2–and recombines into N2O4–under the influence of thermodynamic transformations throughout the cycle, in accordance with chemical equilibrium. Addressing discrepancies in previous studies, this work aims at assessing a wide range of theoretical chemically reactive gases as working fluids in a Stirling cycle, employing the ideal gas mixture model. The behavior of each reactive fluid is examined throughout the cycle, and the thermodynamic performance is evaluated. Therefore, this work quantifies and analyzes the thermodynamic performance of a chemically reactive Stirling engine. Results indicate a slight increase in the net specific work output with certain reactive fluids, offering a thermal efficiency comparable to that of inert working fluids. In addition, it is emphasized that for chemically reactive working fluids, the isochoric heat exchange within the internal regenerator is incomplete due to chemical reactions, in contrast to the case of inert fluids. To address this, either a supplementary heat source, heat sink, or both are required during the isochoric processes. Furthermore, chemically reactive fluids in the Stirling engine induce irreversibility in the internal regenerator, stemming from heat exchange across a finite temperature difference, penalizing the thermal efficiency of the engine for the majority of reactive fluids studied.

Optimal Liquid Engine Architecture by Performance-Cooling Tradeoff Analysis

We perform physics-based theoretical analyses on the tradeoff between the overall performance of specific impulse and the thermal protection ability of a coolant liquid film to identify the optimal configuration of a liquid rocket engine. A bipropellant thruster is set as the target, which uses a hypergolic propellant mixture of nitrogen tetroxide as the oxidant and monomethyl hydrazine as the fuel. By considering the practical nonuniform distribution of the local mixture ratio produced in the thrust chamber, the maximum specific impulse is achieved when the fuel and oxidizer spray widths become identical, allowing for the specification of the diameter of the impinging-type injector. The heat balance between the convective heat transfer from the combustion gas and the latent heat of the three-dimensionally wavy liquid film provides the optimal diameter of the combustion chamber. The longest liquid film is found to be achieved when half of the initial film is entrained by the fast gas, correspondingly mitigating the heat transfer area due to the liquid film waviness. We successfully demonstrate the optimal architecture of the liquid engine based on the tradeoff, in which an improvement of specific impulse by 1 s shortens the film length by 2 mm.

Визначення швидкості корозії основного конструкційного матеріалу сіток капілярних розділювачів фаз

The subject of this study is the corrosion processes that occur in the fuel tanks of spacecraft with a long service life, the engines of which operate on chemically aggressive fuel components (FC): nitrogen tetroxide (NT) and asymmetric dimethylhydrazine (NDMH). The goal is to determine the reduction of wire diameters and the increase of cell sizes of capillary phase separator grids (PSG) because of the corrosion effect of the main structural material of the 12X18H10T stainless steel grid. Task: establishing the presence, type, and rate of corrosion of the main structural material of the PSG nets. The methods used are as follows: to determine the presence of corrosion by studying the composition of substances found on the surface of the grids – X- ray fluorescence, X- ray structural, atomic absorption, potentiometric, turbodimetric, infrared spectroscopy, and chromato-mass spectrometry; to determine the type of corrosion-metallographic studies of mesh samples; to determine the rate of corrosion-measuring the geometric dimensions of mesh samples. The following results were obtained. The metal cations detected on the surface of the mesh samples correspond to the elements that make up the alloy of aluminum and steel - the main structural materials of the fuel tanks of launch vehicles; 12Х18Н10Т steel is not susceptible to local types of corrosion (pitting, intercrystalline, dot, contact, crevice, and stress corrosion cracking) in high-pressure and low-pressure tanks; the presence of a continuous (uniform) corrosion effect on the surface of the grid wires was established; dependences of changes in the main geometric parameters of the grids (wire diameters and cell sizes) over time were obtained, according to which the limits of the corrosion rates of stainless steel grade 12X18N10T in the liquid phase of NT and NDMG and in the gas phase were established; and coefficients of the maximum corrosion rate were calculated. Conclusions. The scientific novelty of the obtained results is as follows: for the first time, the presence, type, and rate of corrosion of the main structural material of the PSG grids because of their long-term operation (14...31 years) in the liquid phase of AT and NDMH and in the gas phase were determined using cross-methods.

Novel Hypergolic Green Fuels with Hydrogen Peroxide for Propulsion Systems

By combining the advantages of chemicals from two different classes, a series of catalytically promoted green hypergolic fuels named polyamine/alkanolamine-based hypergolics (PAHyp) with highly concentrated hydrogen peroxide (96%) as an oxidizer was developed. In this paper, a novel recipe based on N,N,N′N′-tetramethylethylenediamine (TMEDA) and N-methyldiethanolamine (MDEA), named PAHyp 1, is characterized. Samples with different volume proportions of TMEDA and MDEA catalyzed with 0.5–4 wt% of copper salts were prepared. It was demonstrated that, by adding low catalyst loadings of 1–2 wt%, ultrafast ignition (as low as 8 ms) can be measured. Fast ignition is important to avoid a hard start in the startup phase, and reduced catalyst loading is important to avoid loss of performance in terms of specific impulse. To evaluate the system’s performance, an orbital transfer maneuver of a geostationary satellite that burns monomethylhydrazine with nitrogen tetroxide was considered. It was demonstrated that when using green formulations based on TMEDA/MDEA, smaller propellant tanks are required (because of the higher density of the green propellants), though more propellant mass is required due to a slightly low specific impulse. Besides good performance and reliable ignition, good storability is crucial for long-term space applications. Remarkably, although TMEDA is sensitive to air, visual inspection, ignition tests, and Fourier-transformed infrared spectroscopy analysis revealed that formulations with volume proportions of at least 60% of MDEA stored in vials filled with air survived with no signs of degradation after 14 months. Finally, to meet the requirement of long-term missions of several years in space, a hypergolic tripropellant feed system was proposed.

Study of Hedge Ignition and Flame Propagation Characteristics of Unsymmetrical Dimethylhydrazine and Its Metamorphosed Mixtures in a Nitrogen Tetroxide Atmosphere

Unsymmetrical dimethylhydrazine (UDMH) is a common liquid propellant widely used in rocket engines and other applications. The safety of UDMH in service is affected by its slow oxidation during long-term storage to form impurities such as dimethylamine (DMA) and formaldehyde dimethylhydrazone (FDH). How these impurities affect combustion performance is not known, and in order to assess these effects, the present experiments investigated the combustion characteristics of self-igniting fuels and carried out ignition delay time measurements and flame propagation velocity measurements of pure UDMH and its denatured mixtures in a nitrogen tetroxide (NTO) atmosphere. This experiment was carried out to measure the delay time of hedge ignition of pure UDMH and qualitative analysis of its flame propagation properties under vacuum conditions at room temperature (T = 293 K). Ignition delay time measurements and flame propagation characterization were performed under the same experimental conditions for UDMH mixed with 1%, 5% and 10% FDH, UDMH mixed with 1%, 5% and 10% H2O, UDMH mixed with 1%, 5% and 10% DMA, as well as for UDMH mixed with the same proportions of the three substances (1%, 5% and 10%). The flame propagation characteristics were analyzed. The results showed that the incorporation of DMA, H2O and FDH in different proportions could inhibit the combustion of UDMH to varying degrees and prolong its ignition delay time. It is worth noting that the introduction of FDH had the least effect on it, and the least effect was observed at a concentration of 1%. In contrast, the effect of DMA on UDMH is more obvious, and the addition of H2O has the largest increase in the ignition delay time of UDMH. In the flame propagation experiment, the flame of the experimental group adding H2O can no longer fill the whole experimental window, while the other experimental groups can still make the window full of flame. Combined with the measurements of the ignition delay time, it can be seen that the moisture content has the greatest effect on the combustion characteristics.

Експериментальне визначення зміни капілярної утримної здатності сітчастих розділювачів фаз

The subject of this study is the process of loss of capillary holding capacity (CHC) as a result of a violation of the balance of external and internal forces on the phase interface (PI) "liquid - gas" of the capillary in the cell of the mesh phase separator (MPS) of the capillary means for ensuring the integrity of the fuel (CMEIF) with a long service life in chemically aggressive fuel components (FP): nitrogen tetroxide (NT) and asymmetric dimethylhydrazine (NDMH). The goal is to improve the selection of design parameters of the CMEIF through the refinement of traditional approaches to the calculation of the CHC MPS depending on the term of their operation. Task: to determine the rate of corrosion of the main structural material of the MPS - steel nets of the twill weave type, and its effect on the structural and geometric characteristics of the nets; to perform an experimental determination of the change in the MPS CHC; to improve the mathematical model for determining the MPS CHC, considering the term of their operation as part of the fuel system of space flight vehicles (SFV). The methods used are as follows: to determine the rate of corrosion - metallographic studies and measurement of the geometric dimensions of mesh samples; to determine the change in CHC - the bubble method. The following results were obtained. The coefficient of the maximum corrosion rate was determined. A new, refined dependence of the average value of Bo cr on the temperature of the FP was obtained. Linear regressions of changes in the approximated values of CHC MPS depending on the duration of their operation were obtained. An increase in the average arithmetic value of the wetting contact angle θ in the NDMG over 31 years of MPS operation was determined. An improved mathematical model for determining the CHC of MPS was obtained, considering the period of their operation in JSC and NDMH. Conclusions. The scientific novelty of the obtained results is as follows: for the first time, comprehensive studies were carried out to determine the rate of corrosion of the main structural material of MPS after a long period of their stay (from 14 to 31 years) in FP (NT and NDMG) and under their pairs, the results of which revealed regularities of flow corrosion processes in the liquid and gas phase, established corrosion rates and deduced coefficients, the application of which improves the engineering methods of calculating the main parameters of MPS; the physical model for calculating Bo kr received further development; the physical model for calculating the CHC has been improved, which makes it possible to calculate the value of the static CHC of the MPS with greater accuracy than it was before and to make the final design of the designed CMEIF more perfect and reliable.

Infrared spectroscopic and thermographic evidence for the interaction of ethylene and 1,3-butadiene with N2O4 at cryogenic temperatures

The possibility of the reaction of ethylene at cryogenic temperatures with dinitrogen tetroxide (N2O4), at least at –40 °C, has been demonstrated. An infrared (IR) spectroscopic analysis of the condensed reaction products was carried out, which showed the presence of substances containing organic nitro compounds and organic nitrates. The latter particularly means the possibility of the formation of explosive substances, as in the known explosive cryogenic reaction of N2O4 with butadiene. The fundamental possibility of such a reaction is of importance for the organization of cryogenic production of gases from raw materials containing ethylene and nitrogen oxide impurities. The sensitivity of the experimental setup was demonstrated by using the example of the known reaction of N2O4 with butadiene. The temperature and time characteristics of the latter reaction have been found. To determine the temperature range of possible reactions of ethylene with N2O4, thermograms of the process of heating the reactive mixture at a constant rate were analyzed. To ensure the sensitivity of the qualitative analysis of thermograms of the reaction of ethylene with N2O4 in the linear heating mode, a quasi-differential method was proposed that uses the temperature of the cryo-thermostat coolant, which varies linearly with time, as the reference temperature. Some recently published theoretical results concerning the mechanisms of N2O4 isomerization are discussed which may be useful for further studies in establishing the mechanisms and predicting the ratios of the products and their yields for the reaction of N2O4 with olefins under particular experimental conditions.

Experimental research on the detonation behavior in annular combustors utilizing liquid hypergolic propellants

The development of rotating detonation engine utilizing hypergolic propellants is necessary for practical application of detonation-based rocket engines, but this liquid-liquid rotating detonation has been rarely researched due to its difficulty of well atomization and mixing in very short time. This study aims to experimentally investigate the propagation characteristics of rotating detonations using non-premixed hypergolic propellants in annular combustors. Here the monomethyl hydrazine (MMH) and nitrogen tetroxide (NTO) have been used as oxidizer and fuel, respectively. Twenty-four unlike impinging elements have been used for injection and mixing of liquid propellants. The orifice diameter is 0.4 mm for oxidizer and 0.3 mm for fuel. Three typical combustion modes such as deflagration mode, one-wave rotating detonation mode and two-wave collision mode have been captured by dynamic pressure transducers and the high-speed camera. The influence of many factors, such as mass flow rate, mixing ratio, annular combustor width and chamber throat, on rotating detonation behaviors have been investigated. The propagation velocity of rotating detonations is around 1328 m/s∼1405 m/s, including one-wave rotating detonation mode and two-wave collision mode. When the mass flow rate and mixing ratio is not appropriate, the hypergolic combustion becomes obviously unstable and combustion modes vary very quickly, especially at the start-up stage. The chamber throat plays a negative role on rotating detonation which suppresses the detonation propagation and can lead to detonation fail. Besides, the wider annular combustor width is beneficial for rotating detonation propagating, which can eliminate the negative influence of the chamber throat on the detonation propagation. In addition, increasing mass flow rate would lead to higher injection velocity and thus better impinging injection, atomization and mixing, which is positive for increasing the stable operation range of mixing ratio for rotating detonations.

A DFT mechanistic study on the N‐acyloxyamine‐initiated controlled degradation of polypropylene

AbstractN‐acyloxyamine is an excellent radical initiator for the controlled degradation of polypropylene (PP). Irgatec CR 76 (CR‐76) is one of the most important N‐acyloxyamines for the controlled degradation processes. The experiments show that 2 wt% CR‐76 caused a degradation and lowering of Mw to over 50% and of Mn in 10%–15%. The density functional theory (DFT) calculated results indicate that the NO bond cleavage of enol‐CR‐76 is the easiest to generate nitrogen (N˙) and ˙CH2COO radicals. In the controlled degradation process of PP, compared with the generated nitrogen (N˙), nitroxyl (NO˙), and nitrogen peroxide (NOO˙) radicals, the produced small molecule radicals such as CH3COO˙, (CH3)2CH˙, and (CH3)2CHCH2˙ radicals show better activity in the hydrogen abstraction process of PP. In addition, the NO˙, NOO˙, and ROO˙ (R = (CH3)2CH) radicals were proposed to be of importance in the radical coupling and β‐scission of PP˙ radical after the hydrogen abstraction in the controlled degradation of PP. This provide new insights into the controlled degradation of PP. Furthermore, thereby some theoretical guidance could be provided into the design of new N‐acyloxyamine radical initiator for the controlled degradation of polymers.

A Coupled Heat Transfer Calculation Strategy for Composite Cooling Liquid Rocket Engine

To better understand the characteristics of coupled heat transfer in liquid rocket engines, a calculation scheme is proposed in this paper. This scheme can simulate the coupled heat transfer processes, including combustion and flow in the thrust chamber, radiation heat transfer, heat conduction in the wall, heat transfer of coolant flow in the cooling channel, and gas film cooling in the thrust chamber wall. The numerical method used in each physical area, the data transfer method between each computing module, the strategy of data transfer on the coupling interface, the calculation process, and the convergence criterion are all introduced in detail. The calculation scheme was verified by analyzing a water-cooled nozzle. Then, the coupled heat transfer calculation was carried out for a liquid rocket engine using a propellant composed of unsymmetrical dimethylhydrazine and dinitrogen tetroxide. Two working conditions were analyzed: whether the gas film cooling was performed or not. The results showed that the algorithm successfully indicated the protective effect of the gas film on the wall surface, and the calculation results were reasonable. It played a guiding role for the coupled heat transfer of the liquid rocket engine using a composite cooling method.

Заправно-нейтралізаційна станція. Нові розробки та аспекти використання

The article dwells on development and study of the multifunctional operations while preparing propellant components for launch vehicle tank filling by high-boiling propellant components at the neutralization stations. The article considers the preparation of propellant for filling the launch vehicle stages with high-boiling propellant components of nitrogen tetroxide (oxidizer) and unsymmetrical dimethyl hydrazine (fuel) in terms of propellant saturation with helium and denitrogenation. Usually these issues refer to the common technology of propellant preparation and are tackled sequentially: first, propellant is drained into the filling tank of the filling system, then the propellant is denitrogened, for example purging the propellant by helium under atmospheric pressure in the tank, then propellant is saturated with helium to the given concentration by bubbling helium in the propellant, maintaining the set pressure of helium in the tank. This technology significantly complicates the process of propellant preparation, increases helium consumption, as well as the amount of the generated vapor, which requires recycling in the neutralization units. This article studies multifunctional operations, where the propellant is simultaneously drained from delivery vehicles, saturated with helium and denitrogenated. Amount of residual nitrogen in the propellant and the main direction of deep denitrogenation of the propellant are calculated. Amount of generated vapor and consumed helium are determined. The process of propellant draining by extrusion, maintaining the given pressure in the tank and alternating the propellant drain on the closed vent device (compression) and open vent device (decompression) is studied. As a result, the theoretical justification of multifunctional operations in preparation of high–boiling propellant components to fill the launch-vehicle stages is presented. Key words: saturation with helium and denitrogenation of the propellant, drain with closed vent device, excessive pressure draining, gas-vapor mixture, neutralization system.

Christopher Newton

Helvetica Chimica ActaVolume 106, Issue 3 e202300007 Author ProfileFree Access Christopher Newton First published: 31 January 2023 https://doi.org/10.1002/hlca.202300007AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract I chose chemistry as a career because I always loved building things (born largely out of a Lego obsession as a child). The secret to being a successful scientist…I don't know about THE secret (nor what constitutes successful for that matter), but I am confident I wouldn't be where I am today without strong and effective mentorship. I only hope I can pay it forward. A key experience in my career was trying (and failing) to reproduce an old synthesis of 1,2-dinitroethylene. … Position: Assistant Professor, University of Georgia, Athens, USA E-mail: [email protected] Twitter – Homepage: www.newton-lab.org ORCID: 0000-0002-8962-5917 Education: 2009 BSc (Chemistry), Victoria University of Wellington, New Zealand 2014 PhD with Michael Sherburn, Australian National University 2015–2018 Postdoc with Nicolai Cramer, EPFL, Switzerland 2018–2021 DECRA Fellow, University of Adelaide, Australia Research: Cycloaddition reactions, natural product synthesis Hobbies: According to my students it would be using ChemDraw… although I would argue enjoying good food, good wine, and watching live music. I chose chemistry as a career because I always loved building things (born largely out of a Lego obsession as a child). The secret to being a successful scientist… I don't know about THE secret (nor what constitutes successful for that matter), but I am confident I wouldn't be where I am today without strong and effective mentorship. I only hope I can pay it forward. A key experience in my career was trying (and failing) to reproduce an old synthesis of 1,2-dinitroethylene. The procedure required copious amounts of lead(II) nitrate, dinitrogen tetroxide, oxygen, ethylene, an open flame, and several dry ice/acetone baths. It's in those moments you gain a deep appreciation for the importance of developing user-friendly chemistry. A research group is successful, because of teamwork, comradery, diversity, creativity, inclusivity, hard work, high morale… the list goes on. I am incredibly lucky that my group has cultivated just such a working environment, largely of their own volition. It's now up to me not to mess it up! The biggest challenge facing my generation of scientists is administrative responsibilities (I kid, but still…). With my research, I want to achieve… I think the dream for many of us in the field is to develop chemistry that is adopted by industry for the synthesis of pharmaceuticals, agrochemicals, and materials. Valuable advice from a more senior colleague at the beginning of my career was ‘create your own luck by trying everything'. It's all too easy to talk yourself out of running that next experiment. If I were not a scientist, I would likely be a (failed) author, for I initially intended to pursue creative writing at university. I celebrate success by socializing (drinking) with friends. I process failure by socializing (drinking) with friends. One of my achievements was to receive the inaugural Mander award from the Royal Australian Chemical Institute. I was lucky enough to interact with the late Lew Mander on several occasions during my time as a PhD student (including boring him to sleep during a research seminar – a valuable lesson in audience engagement). Guaranteed to make me laugh is my research group (not always intentionally). In a spare hour I am often trawling through music blogs/websites/podcasts in search of new artists. My favorite way to spend a holiday is returning to New Zealand to spend quality time with friends and family. What I appreciate most about my friends is sharp wit. My favorite drink isa South Australian Shiraz (surprisingly easy to come by here in Athens, Georgia). My three top papers 1I. Dissanayake, J. D. Hart, E. C. Becroft, C. J. Sumby, C. G. Newton, ‘Bisketene Equivalents as Diels–Alder Dienes', J. Am. Chem. Soc. 2020, 142, 13328– 13333. 2C. G. Newton, S. L. Drew, A. L. Lawrence, A. C. Willis, M. N. Paddon-Row, M. S. Sherburn, ‘Pseudopterosin synthesis from a chiral cross-conjugated hydrocarbon through a series of cycloadditions', Nat. Chem. 2015, 7, 82– 86. 3C. G. Newton, D. N. Tran, M. D. Wodrich, N. Cramer, ‘One-Step Multigram-Scale Biomimetic Synthesis of Psiguadial B', Angew. Chem. Int. Ed. 2017, 56, 13776– 13780. Volume106, Issue3March 2023e202300007 ReferencesRelatedInformation

Thermal performance of MMH/NTO rocket thrust chamber based on pintle injector by using liquid film cooling

A liquid rocket engine needs to be protected against damage of the combustion chamber wall during operation, being exposed to high temperature and pressure gas conditions. It is in urge to design a simple and efficient thermal protection method to cool the wall of the thrust chamber. In present study, a liquid rocket engine CFD model with cooling holes in the upstream side of the thrust chamber wall was established and the propellant combustion performance of monomethylhydrazine (MMH) and nitrogen tetroxide (NTO) was simulated by a simplified multi-step chemical reaction mechanism. The liquid cooling performance of thrust chamber wall was numerically investigated by using the discrete phase model coupled with the wave breakup model and the convection/diffusion controlled model, in which the liquid film coolant is regarded as the discrete phase particles by considering the entrainment and evaporation of liquid coolant droplets in hot combustion gas. The effects of pintle head diameter Dp, oxidant slot height h0 and coolant consumption ratio on liquid cooling performance were discussed. The results demonstrated that smaller Dp and h0 can help to improve the characteristic velocity of the thrust chamber. As the coolant ratio increases from 18% to 24%, the maximum wall temperature of the thrust chamber is reduced by 11% (212 K) with only a 1.3% reduction in characteristic velocity (combustion performance). The present numerical method and results can provide important guidance for liquid film cooling design of the liquid rocket engine based on pintle injector.

ATOMIZATION AND MIXING OF BLENDED ENERGETIC IONIC LIQUID HYDROXYETHYLHYDRAZINIUM NITRATE

Hypergolic propellants are widely used in liquid rocket propulsion. Instantaneous control of combustion, lack of requirement of an ignition system, and storability for long durations are the major advantages of hypergolic propellants. The propellant community is on the lookout for replacements for the currently utilized toxic hydrazine and its derivatives. Energetic hypergolic ionic liquids are excellent candidates for such replacement. However, their high viscosity and surface tension render atomization difficult, and hence, increase the ignition delays in the combustion chamber and reduce combustion efficiency. The current study focuses on the geometrical aspects of injector design and other injection conditions that control the ignition process and combustion efficiency. These mainly depend on the extent of mixing and atomization. Shadowgraphy and patternator-based experiments were performed on doublet and triplet impingement injectors under variable injection conditions, such as impingement angle, jet diameters, and injection velocities. A blend of 50% unsymmetrical dimethylhydrazine in the energetic ionic liquid hydroxyethylhydrazinium nitrate (UHN50) shows promise as a candidate for a hydrazine replacement. A blend of 38% ethanol in glycerol (GE6238) was used as a surrogate for UHN50, whereas water was used as a surrogate for nitrogen tetroxide. The effect of variation of injection conditions was found to be contradictory for achieving atomization and mixing. An optimum criterion was obtained for both atomization and mixing.

Simulation Study of the Swirl Spray Atomization of a Bipropellant Thruster under Low Temperature Conditions

The spray atomization of an injector significantly influences the performance and working life span of a bipropellant thruster of a spacecraft. Deep space exploration requires the thruster to be able to operate reliably at a low temperature range from −40 °C to 0 °C, so the effect of low temperature conditions on the atomization characteristics of injector spray is motivated to be comprehensively investigated. To study the swirl atomization characteristics of MMH (methylhydrazine), which is more difficult to atomize than NTO (nitrogen tetroxide), numerical simulations were conducted, employing the methods of VOF (volume of fluid) and LES (large eddy simulation) under low temperature conditions. The physical model with a nozzle size of 0.5 mm and boundary conditions with a velocity inlet of 3.89 m/s both follow the actual operation of thrusters. The development of spray atomization at low temperatures was observed through parametric comparisons, such as spray velocity, liquid total surface area, droplet particle size distribution, spray cone angle and breakup distance. When the temperature decreased from 20 °C to −40 °C at the same condition of flowrate inlet, those atomization characteristics of MMH propellant vary following these rules: the spray ejection velocity of MMH is significantly reduced by 7.7%, and gas-liquid disturbance sequentially decreases; the liquid film development is more stable, with a negative influence on atomization quality, causing difficulties for primary and secondary breakup, so the total surface area of droplets also decreases by 6.4%; the spatial distribution characteristics, spray cone angle and breakup distance vary less than 5%. Therefore, the low temperature condition can directly lower the combustion efficiency of thrusters with obvious performance degradation, but there are no significant changes in the propellant mixing and liquid film cooling. It is concluded that the bipropellant thruster can reliably work at low temperatures around −40 °C for deep space probe operation.