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Hydroxylammonium nitrate(HAN)-based thrusters have been continuously researched as a replacement for conventional hydrazine thrusters. At present, catalytic ignition starting is the most commonly used starting method for hydroxylammonium nitrate-based thrusters, and it is also the most reliable and effective starting method. During the catalytic ignition and start-up process of hydroxylammonium nitrate-based thruster, the catalytic decomposition reaction of hydroxylammonium nitrate always affects the state of the thruster. It is worth noting that the catalytic bed is the key structure of the hydroxylammonium nitrate-based thruster to achieve catalytic ignition. It is necessary to optimize the performance of the hydroxylammonium nitrate-based thruster by optimizing the structure of the catalytic bed. However, there are some limitations to study the working process of hydroxylammonium nitrate-based thruster by experiment. Therefore, the working process of 150N-class hydroxylammonium nitrate-based thruster by numerical simulation was studied in this paper. Then, under the condition that the inlet mass flow rate of the monopropellant was consistent, simulation calculations were carried out on hydroxylammonium nitrate-based thrusters with different catalytic bed structures based on the studied simulation method. Finally, with thrust as the evaluation parameter, the structural parameters of the catalytic bed of the hydroxylammonium nitrate-based thruster were optimized based on the response surface method. After optimized calculation, the hydroxylammonium nitrate-based thruster with a catalytic bed length of 72.43mm, a catalytic bed diameter of 74mm, and a catalytic bed porosity of 0.6 has better performance, which provides a reference for the design of hydroxylammonium nitrate-based thrusters.

We investigated the influence of a copper loading strategy over a honeycomb structure on the catalytic performance during the decomposition of a hydroxylammonium nitrate (HAN) aqueous solution. Copper was supported on the honeycomb surface by means of a metal coating method (MC), i.e., a method of directly coating a metal, and a metal alumina coating method (MAC), i.e., a method of coating a mixture of metal and alumina. The properties of the catalysts were analyzed by N2 adsorption, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The Cu(16.8)/honeycomb-MC catalyst showed a lower decomposition onset temperature during the decomposition of the HAN aqueous solution compared to that over the Cu(7.0)/honeycomb- MAC catalyst, an outcome ascribed to the higher copper loading and the higher dispersion of copper in the Cu(16.8)/honeycomb-MC catalyst compared to that in the other catalyst. The Cu(16.8)/honeycomb-MC catalyst was confirmed to have both excellent activity and heat resistance during the decomposition of a HAN aqueous solution.

A MoSi2 coating was prepared on the Mo1 wire mesh via pack cementation method, and its failure mechanisms under isothermal oxidation and hot-fire test using a hydroxylammonium nitrate based monopropellant were comparatively studied. Under isothermal oxidation at 1300 °C and 1400 °C, degradation of MoSi2 into Mo5Si3 caused failure of the coating, and interdiffusion made a much larger effect relative to oxidation. However, the MoSi2 coating failed because of the synergy of oxidation, ablation, and interdiffusion under hot-fire test. Besides, dissolution of mullite into SiO2 and ablation of high velocity flame contributed to the failure of the coating as well.

Hydroxylammonium nitrate (HAN) monopropellant with its low sensitivity, volatility and toxicity, not only promises a safer substitute to hydrazine but also offers a higher specific impulse and a positive oxygen balance. This study primarily explores the decomposition mechanism and underlying kinetics for a newly developed cerium oxide-based catalyst. The chemical kinetics involved in the thermal and catalytic decomposition was examined through an isoconversional method using thermogravimetric analysis (TG) data. The activation energy (Ea) was evaluated using differential isoconversional method (Friedman's method) and advanced integral isoconversional method (Popescu-Ortega's method). To find frequency factor, compensation effect method (ACE) and intercept method (A0) were used. Advanced integral method could not provide realistic kinetic parameters while differential method predicted values similar to reported values for thermal decomposition. The values obtained for thermal decomposition were found matching with reported values obtained by other techniques which validated the methodology adopted. The reaction mechanism for both thermal and catalytic decomposition were proposed based on evolved gas analysis. The mechanism proposed was able to describe the variable kinetic parameters extracted from isoconversional method. Overall Ea of thermal decomposition of HAN was �95 kJ/mol. The decomposition over ceria-based catalyst was distributed over three stages namely inception, peak and decay with Ea of �33 kJ/mol, �170 kJ/mol and �130 kJ/mol, respectively. Under identical conditions, iridium-based catalyst show two decomposition stages with Ea of �65 kJ/mol and �120 kJ/mol while final stage being evaporation of HNO3. The ceria catalyst favoured N2 formation, increased decomposition of HNO3 and enhanced decomposition enthalpy. © 2021 Wiley-VCH GmbH

“Green” monopropellants based on hydroxylammonium nitrate (HAN) are of interest for replacing highly toxic hydrazine in space propulsion systems and for other applications. However, their combustion mechanisms at high pressures are not well understood. In the present paper, decomposition of HAN at pressures up to 15 MPa was studied with differential scanning calorimetry, while combustion of an aqueous HAN/methanol solution (70.1 wt% HAN and 14.9 wt% methanol) was studied in a strand burner at pressures up to 30 MPa. The experiments in both setups were conducted in a nitrogen environment. It has been shown that the decomposition temperature of HAN significantly decreases with increasing pressure from atmospheric to 2 MPa and remains virtually constant with further increasing pressure to 15 MPa. The decrease with pressure is explained by suppressing evaporation of HNO3 and H2O formed during the decomposition process. The strand burner experiments have revealed an increase in the linear burning rate by over 50% at 12−14 MPa, explained by reaching the critical pressure of the liquid. Other observed pressure dependencies of the burning rate include a decrease at 9–12 MPa, a plateau at 14–19 MPa, a decrease at 20 MPa, and an increase at 22–30 MPa.

This paper presents the initial development and characterization of a novel micropropulsion system for nanosatellite applications: a liquid-fed pulsed plasma thruster (LF-PPT) comprising a Lorentz-...

Electric solid propellants are advanced solid chemical rocket propellants controlled by electric current. An electric solid propellant may also be used in an electric propulsion system: specificall...

Hydroxylammonium nitrate (HAN) is a promising green propellant because of its low toxicity, high volumetric specific impulse, and reduced development cost. Electrolytic decomposition of HAN is an efficient approach to prepare it for further ignition and combustion. This paper describes the investigation of a co-electrolysis effect on electrolytic decomposition of HAN-fuel mixtures using stainless steel-platinum (SS-Pt) electrodes. For the first time, different materials were utilized as electrodes to alter the cathodic reaction, which eliminated the inhibition effect and achieved a repeatable and consistent electrolytic decomposition of HAN solution. Urea and methanol were added as fuel components in the HAN-fuel mixtures. When the mass ratio of added urea ≥20%, the electrolytic decomposition of a HAN-urea ternary mixture achieved 67% increment in maximum gas temperature (T gmax) and 185% increment in overall temperature increasing rate over the benchmark case of HAN solution. The co-electrolysis of urea released additional electrons into the mixtures and enhanced the overall electrolytic decomposition of HAN. In contrast, the addition of methanol did not improve the T gmax but only increased the overall temperature increasing rate. This work has important implications in the development of an efficient and reliable electrolytic decomposition system of HAN and its mixtures for propulsion applications.

Hydroxylammonium nitrate (HAN) is an energetic salt used in flight-proven green monopropellants such as ASCENT (formerly AF-M315E), flown in NASA’s 2019 Green Propellant Infusion Mission, and SHP163, flown in JAXA’s Rapid Innovative Satellite Technology Demonstration-1. The decomposition of HAN is catalyzed by metals commonly found in storage tanks, a factor limiting its use. This work investigates the ability of metal-sequestering chelating agents to inhibit the decomposition of HAN. Isothermal and dynamic thermogravimetric analysis (TGA) were used to find isothermal decomposition rates, decomposition onset temperatures, and first-order Arrhenius reaction rate parameters. In the present research, 2,2′-bipyridine (Bipy), triethanolamine (TEA), and ethylenediaminetetraacetic acid (EDTA) were studied as 0.05, 0.1, 0.5, 1, and 5% by weight additives in 90% aqueous HAN. An isothermal decomposition rate of 0.137%/h at 348 K was observed for HAN. The addition of 1% Bipy and 1% TEA reduced the isothermal decomposition rate by 20.4% to 0.109%/h, and by 3.65% to 0.132%/h, respectively, showing that Bipy can inhibit decomposition. The addition of 1% EDTA increased the isothermal decomposition rate by 12.4% to 0.154%/h. Bipy was found to increase the decomposition onset temperature from 454.8 K to 461.8 K, while the results for TEA and EDTA were inconclusive. First order reaction rates calculated by the Ozawa-Flynn-Wall method were found to be insufficient to capture the effects of the tested additives. Bipy was found to inhibit the decomposition of HAN, while TEA and EDTA produced little or negative effect, a result believed to be due to poor metal complex stability at low pH and high acidity, respectively. Spectrophotometry, used for colorimetric analysis of Bipy+iron complexes, showed that Bipy forms chelate complexes with trace iron impurities when added to HAN solutions.

Electrolytic decomposition of hydroxylammonium nitrate (HAN) is appealing for development of chemical micropropulsion system due to its effectiveness in thermal management. In this paper we present the decomposition characteristics and behaviour of various HAN ternary mixtures prepared according to 0 Oxygen Balance (0 OB). There are multiple stages of decomposition depending on the type of fuels added into the HAN solution. While concentrated HAN solution (73 wt%) has only single stage of decomposition, the saccharides-based HAN ternary mixtures has three stages reaction with increased energy release. The addition of nitrogen-rich compounds has sustained the electrolytic decomposition process into the second stage of reaction, which produced the highest decomposition temperature. The study also reveals a linear relationship between the electrical resistivity of HAN ternary mixture and reaction rate in the first stage of reaction, indicating the presence of Joule heating in the process. The influence of electrical resistivity of the ternary mixture became negligible in the second stage of reaction. This work concludes the importance of combined electrical and thermal energy in the first stage decomposition of HAN ternary mixtures.

This article gives a short review on compatibility and chemical stability of selected aqueous ADN and HAN‐based energetic formulations. A brief introduction will outline Energetic Ionic Liquids (EILs) as a new class of energetic materials with beneficial physical‐chemical properties which make them valuable for application in propulsion technologies. EILs combine the advantages of e. g. low toxicity, showing equal or superior propulsion power compared to the state‐of‐the‐art monopropellant hydrazine. Focus is set on open access ADN and HAN‐based monopropellant formulations that are e. g. realized in the advanced blends LMP‐103S, FLP‐106 or LGP 1845.

Constellation formation flying of nanosatellites (

A novel thruster concept for CubeSats and other small satellites using hydrogen peroxide vapor as a propellant is presented and evaluated. This concept leads to the highest theoretical vacuum speci...

The thermal decomposition of hydroxylamine nitrate (HAN) 95% water solution, a “green” alternative of fuel/oxidizer formulation to hydrazine nitrate, as a rocket propellant in the presence of the h...

The most prominent modes of propulsion for spacecraft are chemical and electric propulsion, and missions that require maneuvering need to select one mode over the other, or in some cases need to carry two separate propulsion subsystems, including management of incompatible propellants. This is particularly limiting for small spacecraft, which lack the volume, mass and power resources to accommodate high-performance propulsion components. Most systems are then confined to either the chemical mode (typically high thrust, low specific impulse) or the electric mode (typically low thrust, high specific impulse). However, recent development of green monopropellants as replacements to hydrazine in chemical thrusters has created a family of propellants that are also compatible with electric thrusters. Notably, the monopropellant AF-M315E/ASCENT and other hydroxylammonium nitrate (HAN) based ionic liquids can be used in electrospray thrusters. This work proposes a bimodal propulsion system that integrates a chemical mono-propellant thruster with electrospray thrusters into a unified system with common propellant. The design, fabrication, and validation of a propellant feed line connecting the central tank to electrospray thrusters is presented here. Key elements of this design include solenoid valves for flow control and capillary tubes for pressure conditioning. A subsequent section of nonconductive tubing allows for water (present in the composition of many HAN-based propellants) to evaporate at its vapor pressure and form bubbles in the propellant line. These bubbles physically segment the conductive ionic liquid and provide electrical isolation between the electrospray thruster and the central tank; this is required to apply high voltage to operate the electrospray thrusters without current leaks or shorts. A prototype propellant line was fabricated and its flow characteristics and electrical impedance were measured in a series of tests to validate the design. These tests successfully demonstrated the feasibility of this design for a bimodal spacecraft propulsion system.

The objective of this study is to elucidate the influence of a loading procedure of iridium and copper oxides over cordierite honeycomb support on catalytic performance during the decomposition of a hydroxylammonium nitrate (HAN) solution. Iridium and copper composite oxides were successfully supported on the cordierite honeycomb at the same time by repeating the wash coating process more than 2 times. Through the wash coating process, Cu and Ir were supported up to 43.4% and 4.9%, respectively. The cordierite honeycomb without active metal plays little role as a catalyst to lower the decomposition temperature. It was found that IrCu/honeycomb-2 catalyst, which was prepared by repeating the wash coating procedure twice, is an optimal catalyst for the decomposition of HAN solution. The IrCu/honeycomb-2 catalyst had the effect of lowering the decomposition onset temperature by 27.1°C compared to thermal decomposition.

The catalytic decomposition of hydroxylammonium nitrate (HAN) was investigated using a series of platinum and iridium supported on mesoporous materials. In this study, MMZY, KIT-6, and SBA-15 were used as supports. The effects of the active metal and the pore structure of the catalysts on decomposition of HAN solution were studied. The activity of the platinum catalysts supported on mesoporous material is much superior to that of the iridium catalysts on the same support. The Pt(10)/SBA-15 catalyst showed excellent decomposition activity and was the best among the catalysts tested here, which seemed to be because of the pore structure of Pt(10)/SBA-15. Because the pore size of Pt(10)/SBA-15 is larger than that of Pt(10)/MMZY and Pt(10)/KIT-6, it is more advantageous for diffusion of reactant and product gas. The activity of the catalyst increased as the amount of Pt loaded on the SBA-15 support increased.

This work presents experimental results on thermal decomposition and combustion of hydroxylammonium nitrate (HAN)-based propellant (HAN—95 wt% water solution) in the presence of nanoporous activated carbon with a high specific surface area (SSA) up to 3000 m2/g. The activated carbon AC was obtained by primary carbonization of rice husk (RH) and subsequent activation of carbonized rice husk (CRH) with potassium hydroxide at the temperature of 700 °C in a rotating spherical furnace. Combustion of HAN in the presence of activated carbon (AC) was investigated in a constant-pressure bomb within the initial pressure range of 1–6 MPa. The linear burning rate (rb) increased for the system of HAN admixed with AC compared to those of the HAN alone. The rb of HAN with AC was equal to 400 mm s−1 at an initial pressure of 6 MPa. It was shown that nonporous AC is a good candidate as an additive for increasing the productivity (high burning rate, high gas exhaust, low initial pressure value for combustion propagation, and low commercial cost of the additive) of HAN-based propellants. Thermal decomposition of HAN-based propellant admixed with AC was assessed by DTA–TG method. Addition of AC reduces the temperature of the onset of HAN decomposition from 185 to 86 ± 0.5 °C. The obtained results allow to assume that addition of just 1% AC affects both the temperature of the onset of complete decomposition and maximum temperature of HAN decomposition. The increase in AC concentration up to 10% leads to a significant decrease in the temperature of HAN complete decomposition. The volatile products emitted during thermal decomposition of HAN doped with AC were characterized by electron ionization mass spectrometry analysis. The primary products of HAN decomposition at different heating rates (m/z = 33 (NH2OH), m/z = 63 (HNO3), etc.) were determined. Significant reduction of NOx emissions during thermal decomposition of HAN was observed. It is shown that addition of AC reduces the amount of NOx gases up to 30%.

Green liquid monopropellant thrusters provide an alternative to toxic hydrazine. A premixed liquid monopropellant based on hydrogen peroxide with ethanol blending was suggested to replace hydrazine...

This Paper suggests two speculations on the nontoxic hypergolic propulsion using hydrogen peroxide as an oxidizer based on the experimental data. Drop tests were repeatedly performed with the nonto...

Conventional chemical propellants such as hydrazine and ammonium perchlorate have been used within the realm of contemporary space propulsion devices and are well established owing to their rich heritage. However, their limitations such as toxicity, difficulty in operational handling and environmental impacts have raised concerns. In view of these limitations, the significance of green propellants such as hydroxylammonium nitrate, hydrogen peroxide (H2O2) and ammonium dinitramide has become more pronounced. In this paper, recent developments in ceramic microthrusters and the associated ceramic microfabrication techniques are reviewed. The characteristics of green propellants are examined, followed by the evaluation of previous attempts to incorporate green propellants into ceramic microthrusters. This has further unveiled the possibilities of green and clean space missions in the future.

Hydroxylammonium-nitrate-based monopropellant thrusters have been continuously researched as a replacement for conventional hydrazine thrusters. An ignition system using the discharge plasma of nob...

Green monopropellants based on hydroxylammonium nitrate (HAN) are a promising alternative to hydrazine in space propulsion systems. In the present paper, thermal and catalytic decomposition of aqueous HAN solution was studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and mass spectrometry. The tests were conducted at heating rates of 1, 2.5, 5, and 10 K/min. The values of the apparent activation energy obtained for thermal decomposition using TGA and DSC are 62.2 ± 3.7 kJ/mol and 57.5 ± 3.5 kJ/mol, respectively, and they are in agreement with the literature data for solid HAN and solutions with high concentrations of HAN. The obtained values of the pre-exponential factor, 2.24 × 10 4 s −1 for TGA and 3.55 × 10 3 s −1 for DSC, are lower by six to seven orders of magnitude than those reported in the literature for aqueous HAN solutions, apparently because of full vaporization of water from the HAN solution at the beginning of the TGA and DSC tests. The use of an iridium/rhodium foam catalyst decreased the temperature of full decomposition by over 60 °C. The value of the apparent activation energy obtained for the catalytic decomposition using TGA is 63.9 ± 2.5 kJ/mol, while the obtained value of the pre-exponential factor is 3.31 × 10 5 s −1 .

Hydroxylammonium nitrate (HAN) is a potential monopropellant for plasma-based electric propulsion thrusters. However, little is known about the thermal decomposition of HAN at pressures typically encountered in aerospace applications. In this study, using residual gas analysis (RGA) we examine the production of nitrous oxide (N2O), nitrosamide (H2N2O), and nitroxyl (HNO) by thermally decomposing HAN exposed to pressures between 2 and 50 mTorr. Initial expectation was that NO and NO2 would be the primary species producing signal at 30 and 46 m/z respectively. Kinetic modeling studies of HAN solution, however, attributed these signals to HNO and H2N2O, respectively. Thermal decomposition was achieved by passively injecting an aqueous HAN solution into a flowing thermal capillary and detecting the gas products with mass spectrometry. N2O and H2N2O produced relatively small signal with a minor pressure dependence at low temperatures and no pressure dependence above ~460 K. HNO produced a much larger signal relative to N2O and H2N2O and exhibited a high level of pressure dependence as temperature increased above the onset of thermal decomposition, ~393 K. These results indicate that the formation of N2O, H2N2O, and HNO is occurring not only in the bulk solution but possibly on the surface of the aqueous HAN solution and in the vapor phase immediately above the solution surface. The kinetics and mechanism of possible decomposition pathways to form these species are discussed.

Hydroxylammonium nitrate (HAN) is an energetic ionic liquid which is fast emerging as a promising environmentally friendly, high performing monopropellant for space propulsion application. The high performance due to the higher adiabatic temperature for HAN based compositions also poses challenges as high temperature tolerant catalysts have to be developed for its decomposition. A novel cobalt doped cerium oxide based catalyst has been prepared by the co-precipitation route and characterized by SEM/EDS, XRD, and XPS. The effectiveness of the catalyst in decomposing HAN has been tested using thermo-analytical techniques. An evolved gas analysis (EGA) to examine decomposition products and the possible reaction mechanism was also performed using the hyphenated DTA-TG-FTIR technique. Formation of an in situ Ce3+/Ce4+ ion couple in ceria during co-precipitation was found to be critical in deciding the reactivity of HAN decomposition over the catalyst. The activity of the catalyst was also examined in a batch reactor for its longevity. The prepared catalyst was found to be more versatile and durable than a hitherto reported alumina supported iridium catalyst in the present studies.

Electrically controlled solid propellant (ECSP) is one promising solution for thrust adjustment and repeated ignition of conventional solid rocket motors (SRM). However, the widely studied ECSP based on hydroxylammonium nitrate (HAN) faces the problems of strong hygroscopicity and low thermal stability, which can lead to failure of ECSP. Inspired by polyethylene oxide-polyacrylonitrile (PEO-PAN) based solid polymer electrolyte, the new PEO-PAN based ion conductive energetic composites (ECs) have been designed and evaluated in this paper. The formulation was theoretically determined based on the energy content, and the samples were prepared by a conventional milling mixing method. The morphology, ionic conductivity, thermal reactivity, decomposition gaseous products and combustion behavior of these new ECs have been comprehensively studied. It has been shown that the initial decomposition temperature of PEO-PAN based ECs is around 243 °C with heat release of 1677.8–1873.9 J·g−1 depending on the oxidizer and polymer content. Meanwhile, the dependences of the ionic conductivity on the burning rate are evaluated. The results showed that the burning rate decreases as ionic conductivity increases. One of these ECs has a high ionic conductivity with a low burning rate under pressure, which is suitable for controllable ECSP.