| Acquisition Program: | |
| | The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation. |
Objective: | Determine the differences and similarities of the hypergolic reaction mechanisms for gas/gas, liquid/liquid, and gel/gel bipropellant systems.
| Description: | Gelled hypergolic propellants offer safety advantages inherent to solid phase systems (good handling and storage characteristics, temperature stability, low vapor pressure) while offering performance characteristics similar to liquid phase systems (variable thrust, ability to throttle and turn on and off).
However, recent testing of liquid and gelled hypergolic propulsion systems has shown marked differences in ignition delay. Longer than anticipated ignition delays have been associated with engine failure.
The goal of this program is to elucidate the underlying physics and chemistry associated with ignition delay in hypergolic propulsion systems. More specifically, we are interested in determining if the differences observed in ignition delay for liquid and gelled hypergolic propulsion systems are due to mainly physical and/or chemical effects. We are also interested in the chemistry occurring during the initial mixing, and how the physical state influences early-time chemical reaction kinetics.
This information is crucial to understanding the overall hypergolic reaction mechanism of gelled propellants and to effectively design bipropellant engines.
Early bipropellant research suggested that physical state of hypergols may have an important effect upon the onset of chemical reaction. When liquid fuel and oxidizer drops approach each other, reaction occurs initially in the vapor phase exterior to the liquid propellant, and this early time vapor phase reaction may inhibit mixing by providing and expanding gas layer between droplets. Gelled fuel and oxidizer droplets/particles exhibit liquid like viscosities and transport, but because of their lower vapor pressures, gas phase reactions exterior to the gel may not provide enough energy to inhibit mixing. We would like to understand how this observed behavior influences ignition delay, and ultimately, engine performance.
This program has three parts. The first part will be to propose, after a thorough literature search, a detailed reaction mechanism for gaseous, liquid, and gelled hypergolic systems using Monomethyl Hydrazine (MMH) as the fuel and Inhibited Red Fuming Nitric Acid (IRFNA) as the oxidizer. Each mechanism should include the affect of the initial physical state of reactants (including gelling agents) upon chemical reaction rates important to ignition delay. Following the compilation of a proposed mechanism, a series of experiments will be designed to validate/invalidate all or part of the proposed mechanisms, especially those aspects that influence ignition delay.
The second part will be the identification of test methods and the design of the corresponding apparatus suited to measuring physical and chemical parameters important to mechanism validation, and to ignition delay, and the incorporation and benchmarking of analytical techniques to measure these physical and chemical parameters (e.g., time histories of combustor temperature, pressure, radical and permanent gases, etc.)
The third part will be to experimentally measure parameters during combustion, and compare the ignition transients of gas/gas, liquid/liquid and gel/gel propellants using MMH and IRFNA as the propellants and modify the mechanisms as experiment suggests. Ideally, we wish to understand how the proposed mechanism may be used to predict ignition delay in new gelled hypergolic propellant systems now under development.
| | PHASE I: Proposed mechanisms will be developed for the gas/gas, liquid/liquid/ and gel/gel hypergolic reactions of MMH and IRFNA based on literature search, previous research, thermochemistry predictions, and engine test results. Reaction mechanisms must include both physical and chemical effects so as to enable prediction of changing ignition delays for the different hypergolic systems being considered.
Following mechanism compilation, a set of test methods and apparatus will be devised that provides the best way forward in validating/invalidating the proposed mechanisms. Deliverables for the Phase 1 will be a summary of the known chemical kinetic information on reacting hypergolic systems, a proposed reaction mechanism for the gas/gas, liquid/liquid and gel/gel systems, and a summary of rate constants, thermodynamic parameters, and transport parameters (when known) for each step in the proposed mechanism. Additionally, a summary of analytical techniques, static and dynamic, that have been applied to hypergolic combustion studies will be used to propose a suite of instrumentation that will be used to validate the proposed reaction mechanisms. Finally, a design of recommended test systems suitable to the investigation of hypergolic reactions important to the proposed mechanism, and to ignition delay, shall be provided.
| | PHASE II: After selection of the test systems, a comprehensive test plan will be prepared for mechanism validation. This plan will include several test series. The initial test series will be used to benchmark the analytical instrumentation, and show the ability to measure ignition delay and chemical and physical parameters for a well characterized system. The first series will also be used to modify the test plan as needed. The second test series will be an initial attempt at measurements aimed at mechanism validation. The results of this first test series should comprise, at a minimum, a statistically significant set of time resolved measurements of ignition delay, temperatures, and chemical species important for each hypergolic system under consideration. Following these measurements, the final report will discuss whether the data support the proposed mechanisms for the MMH/IRFNA gas/gas, liquid/liquid/, and gel/gel systems. Using the experienced gained from the investigation of IRFNA and MMH, preliminary mechanisms will be proposed for the hypergolic reaction of IRFNA with an advanced fuel, currently being developed, in the gas/gas, liquid/liquid, and gel/gel states and a single experimental test series will be performed to provide data towards validation of the proposed mechanisms.
| | PHASE III
| | DUAL-USE APPLICATIONS: After a successful Phase II program, the small business can provide services to those companies who are developing liquid or gelled propellants and do not want to invest in building the capability to study hypergolic ignition and ignition delay themselves. This program is supporting the development of more effective and efficient gel propellant formulations; therefore, private industrial, NASA, and DoD propulsion applications would be ideal marketing targets. The emerging private space launch industry would be interested in this capability when evaluating novel ideas that would give them an advantage over traditional government launch services. This interest would be in actual space launch, satellite positioning, and, potentially, providing space travel to civilians. This emerging industry might be very interested in novel approaches to propulsion if they could be confident that their candidates would be hypergolic. Additionally, commercial and small businesses could take advantage of the physical properties of gelled propellants because of the much simpler, safer, and less costly issues associated with handling and transportation. The small business could commercialize this topic by offering testing services to either NASA or private liquid propulsion companies. DoD is interested in gel propulsion because of thrust management advantages and/or increased safety of gelled propellants. The small business could offer services to both government organizations and liquid propulsion companies. Universities could take advantage of this capability in applying for academic grants.
| References: | 1. Dieter K. Huzel and David H. Huang, “Modern Engineering for Design of Liquid-Propellant Rocket Engines,” progress in Astronautics and Aeronautics, A. Richard Seebas, Editor, Volume 147, American Institute of Aeronautics and Astronautics, Washington, DC 1992.
2. G. Nahamoni and B. Natan, “Combustion Characteristics of Gel Fuels,” AIAA/ASME/SAE/ASEE 33rd Joint Propulsion Conference and Exhibit, Seattle, WA, AIAA paper 97-2973.
3. D. C. Mueller and S. R. Turns, “Ignition and Combustion Characteristics of Metallized Propellants- Phase II, Annual Report,” NASA-LeRC, Grant NAG3-1044, January, 1994.
4. K. Kobaysi, “An Experimental Study on the Combustion of Fuel Droplet;,” Fifth Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, 1954, pp. 141-148.
5. J. D. Clark, “Ignition! An Informal History of Liquid Rocket Propellants, Rutgers University Press, 1972.
6. J. A. Blevins, R. Gostowski, and S. Chianese, “An Experimental Investigation of Hypergolic Ignition Delay of Hydrogen Peroxide With Fuel Mixtures,” AIAA Paper 2004-1335, January 2004.
7. L. Catoire, N. Chaumeix, and C. Paillard, “Chemical Kinetic Model for Monomethylhydrazine/Nitrogen Tetroxide Gas-Phase Combustion and Hyhpergolic Ignition,” Journal of Propulsion and Power, Vol. 20, No. 1, 2004, pp. 87 – 92.
| | Keywords: | fuel gel, oxidizer gel, monomethyl hydrazine, inhibited red fuming nitric acid, physical properties, ignition, hypergolic reactions, chemical kinetics. |