Particle Streak Velocimetry of Supersonic Nozzle Flows

A novel velocimetry technique to probe the exhaust flow of a laboratory scale combustor is being developed. The technique combines the advantages of standard particle velocimetry techniques and the ultra-fast imaging capabilities of a streak camera to probe high speed flows near continuously with improved spatial and velocity resolution. This "Particle Streak Velocimetry" technique tracks laser illuminated seed particles at up to 236 picosecond temporal resolution allowing time-resolved measurement of one-dimensional flows exceeding 2000 m/s as are found in rocket nozzles and many other applications. Developmental tests with cold nitrogen have been performed to validate and troubleshoot the technique with supersonic flows of much lower velocity and without background noise due to combusting flow. Flow velocities on the order of 500 m/s have been probed with titanium dioxide particles and a continuous-wave laser diode. Single frame images containing multiple streaks are analyzed to find the average slope of all incident particles corresponding to the centerline axial flow velocity. Long term objectives for these tests are correlation of specific impulse to theoretical combustion predictions and direct comparisons between candidate green fuels and the industry standard, monomethylhydrazine, each tested under identical conditions

Colloidal synthesis and characterization of monocrystalline apatite nanophosphors

Here, we report the synthesis and characterization of 12 nm long, ultrafine, individualized calcium phosphate nanorods. Synthesis of these nanobuilding blocks involved the preparation of a calcium phosphate hybrid precursor containing an aminophosphate ligand. Colloidal calcium phosphate nanoparticles were achieved through the reorganization of an amorphous hybrid precursor at high temperature during a post-ageing step. These nanoparticles can be described as monocrystalline deficient calcium hydroxyapatite Ca102x(PO4)62x(HPO4)x(OH)22x, with surfaces stabilized by [PO3 22–O(CH2)2NH3 +] groups. A model is proposed in which the [ab] plane of the nanoparticles is formed by 9 unit cells surrounded by a peripheral layer composed of twelve aminoethyl phosphate (AEP)-calcium phosphate (xCa9(PO4)6 2 yCa-(AEP)2) hybrid units. Our ultrafine individualized calcium phosphate nanophosphors, synthesized in aqueous medium and displaying amino groups on their surface, are good candidates for use as fluorescent probes in biological imaging

First Principles NMR Study of Fluorapatite under Pressure

NMR is the technique of election to probe the local properties of materials. Herein we present the results of density functional theory (DFT) \textit{ab initio} calculations of the NMR parameters for fluorapatite (FAp), a calcium orthophosphate mineral belonging to the apatite family, by using the GIPAW method [Pickard and Mauri, 2001]. Understanding the local effects of pressure on apatites is particularly relevant because of their important role in many solid state and biomedical applications. Apatites are open structures, which can undergo complex anisotropic deformations, and the response of NMR can elucidate the microscopic changes induced by an applied pressure. The computed NMR parameters proved to be in good agreement with the available experimental data. The structural evaluation of the material behavior under hydrostatic pressure (from --5 to +100 kbar) indicated a shrinkage of the diameter of the apatitic channel, and a strong correlation between NMR shielding and pressure, proving the sensitivity of this technique to even small changes in the chemical environment around the nuclei. This theoretical approach allows the exploration of all the different nuclei composing the material, thus providing a very useful guidance in the interpretation of experimental results, particularly valuable for the more challenging nuclei such as $^{43}$Ca and $^{17}$O.Comment: 8 pages, 2 figures, 3 table

Testing of Gelled and Neat Hypergolic Propellants

Hypergolic propellants (hypergols) are propellants that ignite shortly after contact. They omit the requirement of an ignition system, making hypergolic engines simple, reliable and capable of being throttled several times. These advantages make them desirable for deep space missions. However, the applications are severely limited by their toxicity and reactivity. In an effort to increase the safety of manufacturing, shipping, and storing, these propellants can be combined with different gelling agents. The focus of this project is to build an optically accessible combustion chamber pressurized at 200 psi to compare the performance of gelled and neat Monomethyl Hydrazine (MMH) and Red Fuming Nitric Acid (RFNA). The fuel samples of MMH will be gelled with either Hydroxypropyl Cellulose (HPC) or fumed silica at various weight percentages and oxidizer samples of RFNA will be gelled with fumed silica. The propellants will be injected at different mixture ratios into the combustion chamber, using an existing impinging jet mechanism, where the reaction will be recorded via high speed cameras focused on the incoming jets of propellants. Data acquired through testing the propellants in this system will allow for calculation of ignition characteristics, combustion efficiency, and specific impulse for both neat and gelled propellants. The final results will help in the further understanding of neat and gelled hypergolic propellants in terms of their performance and behavior in a high pressure environment. This project is a gateway into the testing of other gelled hypergols and applying the knowledge into building safer and more efficient hypergolic engines

Fluid Control in Rocket Injectors with the Use of Pressurized Systems for Throttling

Throttling a rocket is a necessary task that must be accomplished in order to achieve proper efficiency and performance over a desired thrust range. Simply put, throttling is achieved by managing the fluid flow in a rocket injector in order to insure proper functioning. There are several different methods on how to throttle rockets, but a simple and inexpensive method is desired in some applications, such as student built University projects. A hot fire test of a hybrid rocket motor was conducted at Purdue University in May 2013, after which a throttling method was desired. The method proposed in this document outlines the use of a pressurized system to deliver oxidizer fluid. A modified throttling valve is utilized to manage oxidizer flow rate in a hybrid rocket engine by altering the pressure gradient. The goal of throttling this rocket will be to maintain a proper oxidizer to fuel (O/F) ratio by decreasing the mass flow rate of the oxidizer in a pressurized nitrogen system. Upon cold flow and hot-fire testing, results and data will provide insight on further design modifications to insure proper performance of the hybrid rocket engine mentioned above. Additional work on this topic will need to be done after the planned tests of summer 2013

Metal Hydride Component Design (MHy-CoDe) Tool for the Selection of Hydrides in Thermal Systems

A system has been developed to enable the targeted down-selection of an extensive database of metal hydrides to identify the most promising materials for use in thermal systems. The materials’ database contains over 300 metal hydrides with various physical and thermodynamic properties included for each material. Submodels for equilibrium pressure, thermophysical data, and default properties are used to predict the behavior of each material within the given system. The application used at this time is a stationary combined heat and power system containing a hightemperature proton exchange membrane (PEM) fuel cell, a hot water tank, and two metal hydride beds used as a heat pump to increase the efficiency of a natural gas system. The targeted down-selection for this system focuses on the system’s coefficient of performance (COP) for each potential pair and the corresponding sensitivity of the COP and has been used to identify the top 20 pairs, with COPs \u3e1.3, for use in this application

Feasibility Study and Demonstration of an Aluminum and Ice Solid Propellant

Aluminum-water reactions have been proposed and studied for several decades for underwater propulsion systems and applications requiring hydrogen generation. Aluminum and water have also been proposed as a frozen propellant, and there have been proposals for other refrigerated propellants that could be mixed, frozen in situ, and used as solid propellants. However, little work has been done to determine the feasibility of these concepts. With the recent availability of nanoscale aluminum, a simple binary formulation with water is now feasible. Nanosized aluminum has a lower ignition temperature than micronsized aluminum particles, partly due to its high surface area, and burning times are much faster than micron aluminum. Frozen nanoscale aluminum and water mixtures are stable, as well as insensitive to electrostatic discharge, impact, and shock. Here we report a study of the feasibility of an nAl-ice propellant in small-scale rocket experiments. The focus here is not to develop an optimized propellant; however improved formulations are possible. Several static motor experiments have been conducted, including using a flight-weight casing. The flight weight casing was used in the first sounding rocket test of an aluminum-ice propellant, establishing a proof of concept for simple propellant mixtures making use of nanoscale particles