Hydrazine Replacement Research Articles

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.

Experimental studies on flame propagation and detonation characteristics of premixed nitrous oxide, ammonia, and propane in cylindrical channel

Nitrous oxide fuel blends have been identifiedas a promising propellant to be used as a hydrazine replacement. In this study, the flame propagation and detonation characteristics of nitrous oxide, ammonia, and propane mixtures were investigated experimentally in a cylindrical channel (length, 2000 mm; inner diameter, 15 mm). Tests were performed for five propane mass fractions (0, 2.0, 3.8, 5.7, and 7.4 wt%) to investigate flame behavior and determine the suitablepropellant formulation. The results demonstrated that the flame acceleration rate first increased and then decreased with additional increases of propane. The overpressures and shock velocities exhibited a similar trend and achieved the steady detonation stage except for the mixture with propane fraction of 7.4 wt%. Propane outperformed ammonia as an additive to nitrous oxide, and the addition of 2.0 wt% propane had a positive influence on the flame acceleration process, pressure, and shock buildup for premixed nitrous oxide and ammonia. However, for lower concentrations of nitrous oxide with the addition of excessive propane, a decrease in the aforementioned parameters was observed in the doped flames.

To Infinity and Beyond: An Optimization Study of Kerosene and Hydrogen Peroxide Bipropellant Fuels

Currently, hydrazine fuels are grossly inefficient in terms of environmentally friendliness and handling costs. Hydrogen peroxide (H2O2) and kerosene bipropellants have recently shown promise as a fuel that is similar in efficiency to hydrazine yet superior in cost and environmentally friendliness. Previous research on H2O2/kerosene bipropellants view environmentally friendliness, cost effectiveness, and fuel efficiency separately, making comparison between these properties difficult. This research uses calorimetry to provide a new method of quickly and precisely finding optimal ratios of fuels in bipropellants. For different ratios of fuel, efficiency was measured by finding the fuel mixture’s specific energy, environmentally friendliness was measured by finding the fuel mixture’s efficiency per carbon released into the atmosphere, and cost effectiveness was measured by finding the fuel mixture’s efficiency per unit fuel cost. The Cobb-Douglas function was used to optimize for multiple fuel properties at the same time: environmentally friendliness and efficiency, cost effectiveness and efficiency, and environmentally friendliness and cost effectiveness. These double optimizations brought new properties of H2O2/kerosene bipropellant fuels to light, notably that the optimal ratio of fuel for environmentally friendliness coincides with the optimal ratio for fuel efficiency, and the bipropellant remains efficacious in terms of efficiency even while operating at the optimal quantity for cost effectiveness. In short, these findings reaffirm H2O2 and kerosene bipropellants as great potential candidates for an eco-friendly and cost effective replacement of hydrazine because of their unique potential to remain environmentally friendly even at optimally efficient ratios.

Theoretical Performance and Application Cases of Water Electrolysis Propulsion

Water Electrolysis Propulsion offers a clean alternative to current toxic and detonable spacecraft propellants. Beyond the potential replacement of hydrazine as propellant, water based propulsion can be highly attractive for future exploration missions, since the availability of water on many potential landing sites offers the opportunity of refueling. The paper discusses components and state of the art of water propulsion and lists possible variants. A performance analysis is made by use of the chemical equilibrium code CEA. Trade-offs and comparisons are performed with conventional chemical and electric propulsion systems.

The auto-ignition boundary of ethylene/nitrous oxide as a promising monopropellant

C2H4/N2O has recently been proposed as a promising monopropellant for hydrazine replacement. In this work, the auto-ignition capability of argon diluted C2H4/N2O was experimentally investigated firstly in a rapid compression machine by detecting the light emission and the pressure evolution profiles. The auto-ignition boundary temperature which separates the non-ignition and successful ignition cases was then determined and modeled as a function of pressure and mixture composition. Results show that the auto-ignition temperature decreases with the increase of pressure and increases with the argon dilution fraction and fuel oxidizer ratio. In addition, for successful auto-ignition cases, the ignition delay times were measured and used to validate several recently developed kinetic mechanisms. A mechanism was developed and showed good agreement with the measured ignition delay time as well as the auto-ignition boundary temperature at all test conditions. Finally, the auto-ignition boundary temperatures at practical rocket engine conditions (without dilution) were numerically predicted at various pressure and fuel oxidizer ratio conditions. The model is of merit for designing the cooling system and the local flow residence time to reduce the risk of fuel line explosion and the resonance acoustic induced combustion instability in practical rocket engine.

Thermal Ignition of ADN‐Based Propellants

AbstractAmmonium dinitramide (ADN, NH4+ N(NO2)2−) based monopropellants are extremely promising as hydrazine replacement. Thermal igniters are attractive for ADN thrusters as they allow a more prompt ignition and may be better suited for larger engines (100‐500 N) compared to the currently used preheated catalysts. The results of an experimental campaign conducted on the ignition of two ADN‐based monopropellants (LMP‐103S and FLP‐106) with a torch igniter are presented. Several combustion chamber configurations have been tested to facilitate the ignition. Through the use of porous inlays in the chamber, ignition of both propellants was achieved. It was not possible, however, to achieve sustained combustion under the chosen test conditions.

The ignition process measurements and performance evaluations for hypergolic ionic liquid fuels: [EMIm][DCA] and [BMIm][DCA

Bipropellant liquid rocket engines are typically fueled by hydrazines that exhibit extreme toxicity and carcinogenity. Recently hypergolic ionic liquids (HILs) have been emerging as environmentally friendly propellant that holds the potential for hydrazine replacement due to their low volatility, easy and safe storage and handling. The HIL is a novel concept both for chemistry community and for combustion community, and plenty of research waits to be initiated to promote practical propulsion application, especially for comprehensive understanding on their fundamental combustion. In this work, hypergolic ignition of two HILs (1-ethyl-3-methylimidazolium dicyanamide([EMIm][DCA]) and 1-butyl-3-methyl-imidazolium dicyanamide ([BMIm][DCA]) were tested with three oxidizers (white fuming nitric acid (WFNA), red fuming nitric acid(RFNA), and nitrogen tetroxide). A drop test system was designed to control the collision event of a single droplet of fuel with an oxidizer pool. Two independent high speed cameras were spontaneously employed to capture the self-luminous images of the whole hypergolic ignition process as well as the initial impact process. The results showed that hypergolic ignition process of [EMIm][DCA]-WFNA is quite similar to that of monomethyl hydrazine-WFNA. Combined with thermo physical properties of HILs, hypergolic ignition process of [EMIm][DCA]-WFNA is proposed. To qualitatively demonstrate the overall hypergolic ignition and reactivity, the explosion delay time and the ignition delay times of various combinations of the fuel-oxidizer pairs were determined. The effects of the Weber number on the explosion delay time and the ignition delay time of [EMIm][DCA]-WFNA are quantitatively investigated. Hypergolicity of different propellant combinations is tested to investigate the influence of oxidizer’s oxidative capacity and HILs’ cation structure. Additionally, the propulsive performance of the two dicyanamide-based IL fuels was evaluated and compared with traditional hydrazine-based fuels, based on a steady rocket model under the same initial conditions. Results show that using WFNA as the oxidizer, BMIM DCA and EMIM DCA presented a comparable propulsive performance to that of UDMH.

New technologies for ammonium dinitramide based monopropellant thrusters – The project RHEFORM

New technologies are developed in the project RHEFORM to enable the replacement of hydrazine with liquid propellants based on ammonium dinitramide (ADN). The replacement of hydrazine with green propellants will make space propulsion more sustainable and better suitable for the requirements of future missions. In the RHEFORM project investigation on the composition of the propellants are conducted to enable the use of materials for catalysts and combustion chambers which are not subject to the International Traffic in Arms Regulations (ITAR). New igniters are under development aiming at a reduction of required energy and a more prompt ignition. Two different types of igniters are considered: improved catalytic igniters and thermal igniters. The technologies developed in RHEFORM will be implemented in two thruster demonstrators, aiming at a technology readiness level (TRL) of 5. In the present work the results obtained in the first half of the project are presented.

ChemInform Abstract: Isolation and Structural Characterization of the Elusive 1:1 Adduct of Hydrazine and Carbon Dioxide.

AbstractThe zwitterionic form of carbazic acid is isolated as a stable solid and successfully used as a hydrazine replacement in the synthesis of azines (II) and (IV).

Inorganic or Organic Azide-Containing Hypergolic Ionic Liquids⊥⊥ As poster published in 1st Korean International Symposium on High Energy Materials, Incheon, Korea, October 6−9, 2009.

Recently extensive research has focused on replacing toxic hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine as liquid propellant fuels. 2-Azido-N,N-dimethylethylamine (1) is a good candidate to replace hydrazine derivatives in certain hypergolic fuel applications. Energetic ionic liquids that contain the 2-azido-N,N,N-trimethylethylammonium cation with nitrocyanamide, dicyanamide, dinitramide, or azide anion have been successfully synthesized in good yields by metathesis reactions. Ionic liquids have received considerable attention as energetic materials. The replacement of hydrazine with tertiary ammonium salts is especially attractive since many ionic liquids are models for green chemistry. In this work, new azide-functionalized ionic liquids are demonstrated to exhibit hypergolic activity with such oxidizers as 100% nitric acid or nitrogen tetraoxide (NTO).

Overview of the Development of Hydrazinium Nitroformate-Based Propellants

Recent improvements in thequality ofhydrazinium nitroformate (HNF)and binderpolymerdevelopmentshave shown that it is possible to produce HNF-based propellants with hydroxyl-terminated polybutadiene (HTPB), glycidylazidepolymer (GAP),andpoly3‐nitromethoxy ‐3‐methyloxetane[polynimmo (PNM)]asbinders.Especially when considering space applications, HNF-based propellants show results that encourage further research and development. An alternative method to cure GAP has been evaluated. This curing method eliminates the use of isocyanates, which always require special attention when used together with HNF. Combustion studies, experimental and theoretical, led to a good understanding of the steady-state combustion of HNF/GAP sandwiches and HNF/GAP propellants. Burning-rate modie ers have been identie ed, which lower the burning-rate exponent in GAP/HNF propellants by at least 25%. HNF/GAP and HNF/PNM propellants have a low temperature sensitivity. Liquid HNF monopropellants look attractive as a hydrazine replacement. They offer the same or a substantially higher Isp, combined with a 30 ‐40% higher density. The progress made in the manufacture of HNF and the HNF-based propellants (solid and liquid ) was possible through extensive international cooperation.

Studies on the nucleotide arrangement in deoxyribonucleic acids IX. Selective degradation of pyrimidine deoxyribonucleotides

The study of the sequence of purine nucleotides in deoxyribonucleic acids requires the availability of suitable preparations of apyrimidinic acid, i.e., of polydeoxyribophosphate chains retaining the purines of the parent DNA in unchanged sequence and proportions. For an understanding of the degradation of DNA a detailed knowledge and a complete balance of the hydrazinolysis of pyrimidine deoxyribomononucleotides were required. The course and the rate of the degradation by hydrazine of thymidylic and deoxycytidylic acids were studied under a variety of conditions. These nucleotides, when treated with anhydrous hydrazine, give rise to stoichiometric amounts of (a) urea; (b) the hydrazone of 2-deoxyribophosphate; and (c) a heterocyclic compound. The latter is 4-methyl-5-pyrazolone in the case of thymidylic acid, and 3(5)-amino-pyrazole in the case of deoxycytidylic acid. The hydrazone of the sugar phosphate is cleaved quantitatively with benzaldehyde to yield 2-deoxyribophosphate and benzalazine. The various breakdown products were identified by comparison with authentic preparations. The first-order reaction of the degradation with anhydrous hydrazine is completed at 60° within 1.5 h for deoxycytidylic acid and within 4 h for thymidylic acid. At 40°, the time required for completion is about 4 times as long. Other orienting experiments demonstrated that purine deoxyribonucleotides withstand the treatment with hydrazine; that aqueous hydrazine solutions at various pH values effect a slower and irregular degradation; and that the replacement of hydrazine by monosubstituted hydrazine derivatives, such as phenyl- or methylhydrazine does not yield the desired results.