Ignition or thermal explosion in an oxidizing porous body of material call be described by a dimensionless reaction-diffusion equation of the form partial derivative(t)u = del(2)u + lambda e(-1/u). Here such equations will be formulated in symmetrically shaped bounded regions Q, effectively reducing the mathematical formulation to that of one dimension. This is critically re-examined from a modern perspective using numerical methods. A computer algorithm is constructed and used to carry out a broad-ranging evaluation of the watershed critical initial temperature conditions for thermal ignition of nonuniform assemblies. It is then shown how the resulting mathematical structure for the ignition threshold Curves can be correlated by a hyperbolic conic section with a high degree of accuracy over the full range of positive ambient temperature values. However, this sometimes over-predicts (which is bad) and sometimes under-predicts (which is good) the critical initial condition. The definition of additional dimensionless parameters is found to generate further simplification, leading to a universal correlating form capable of collapsing the entire solution space onto a single line in the plane of the new variables. In addition, this study considers the physically intuitive conjecture that spatial moments of the initial temperature profile ought to possess a direct mathematical link to the critical ignition threshold. As such, the mth-order spatial moment of the critical total energy content integrals is defined, and an empirical result is derived stating that certain orders of this moment should be insensitive to changes in ambient temperature and initial shape profile and may be considered functionally dependent on the dimensionless eigenvalue only, within some quantifiable error hand. Spatial moment integrals, based On Computed critical threshold conditions, are found to support this conjecture, with the best accuracy obtained for the second-order moments.

The University of Alabama in Huntsville s Propulsion Research Center has teamed with NASA's Marshall Space Flight Center (MSFC) to research the effects of atomic oxygen (AO) bombardment on coated tether materials. Tethers Unlimited Inc. has provided several candidate tether materials with various coatings for AO exposure in MSFC s Atomic Oxygen Beam Facility. Additional samples were exposed to ultraviolet (UV) radiation at MSFC. AO erodes most organic materials, and ultraviolet radiation embrittles polymers. This test series was performed to determine the effect of AO and UV on the mechanical integrity of tether materials that were treated with AO-protective coatings, such as polyhedral oligomeric silsesquioxane (POSS) or metallization. Both TUI's Multi-Application Survivable Tether (MAST) Experiment and Marshall Space Flight Center s Momentum Exchange Electrodynamic Reboost (MXER) programs will benefit from this research by helping to determine tether materials and coatings that give the longest life with the lowest mass penalty.

The University of Alabama in Huntsville s Propulsion Research Center has teamed with NASA's Marshall Space Flight Center (MSFC) to research the effects of atomic oxygen (AO) bombardment on coated tether materials. Tethers Unlimited Inc. has provided several candidate tether materials with various coatings for (AO) exposure in MSFC's Atomic Oxygen Beam Facility. Additional samples were exposed to ultraviolet (UV) radiation at MSFC. AO erodes most organic materials, and ultraviolet radiation embrittles polymers. This test series was performed to determine the effect of AO and UV on the mechanical integrity of tether materials that were treated with AO-protective coatings, such as Photosil or metallization. Both TUI's Multi-Application Survivable Tether (MAST) Experiment and Marshall Space Flight Center's Momentum Exchange Electrodynamic Reboost (MXER) programs will benefit from this research by helping to determine tether materials and coatings that give the longest life with the lowest mass penalty.

Results of tests characterizing an 8-cm diameter ion source are presented. The tests were conducted in three separate vacuum test facilities at the University of Alabama-Huntsville, Colorado State University, and L3 Communications' ETI division. Standard ion optics tests describing electron backstreaming and total-voltage-limited impingement current behavior as a function of beam current were used as guidelines for selecting operating conditions where more detailed ion beam measurements were performed. The ion beam was profiled using an in-vacuum actuating probe system to determine the total ion current density and the ion charge state distribution variation across the face of the ion source. Both current density and ExB probes were utilized. The ion current density data were used to obtain integrated beam current, beam flatness parameters, and general beam profile shapes. The ExB probe data were used to determine the ratio of doubly to singly charged ion current. The ion beam profile tests were performed at over six different operating points that spanned the expected operating range of the DAWN thrusters being developed at L3. The characterization tests described herein reveal that the 8-cm ion source is suitable for use in (a) validating plasma diagnostic equipment, (b) xenon ion sputtering and etching studies of spacecraft materials, (c) plasma physics research, and (d) the study of ion thruster optics at varying conditions.

Shadowgraph techniques were applied to the cold flow ejector facility at the Propulsion Research Center at the University of Alabama in Huntsville. The setup for the experiments was relatively simple and was accomplished at very little cost. Series of shadowgraph images were taken of both dual nozzle and single nozzle strut based ejectors operating over a range of chamber pressures. The density gradient patterns in the shadowgraphs were compared to pressure data measured along the top and side walls of the mixing duct. The shadowgraph images showed the presence of barrel shocks emanating from the nozzles which at low pressures terminated in Mach disks and at higher pressures extended beyond the barrel shape and reflected off the walls of the duct. Based on pressure data from previous testing, reflected shocks were expected on the walls of the duct. The shadowgraph images confirmed the locations of these reflected shocks on the top wall of the duct. The shadowgraph images also showed the structure change which correlated to a change in pitch of the ejector noise, and corresponded to a change in trend of the duct wall pressure ratio distributions. The images produced from the setup provided insight into the complex flow behavior inside the ejector duct. In addition, the techniques were a valuable tool as an educational device for students.

The Rocket Engine Advancement Program (REAP) 2 program is being conducted by a university propulsion consortium consisting of the University of Alabama in Huntsville, Penn State University, Purdue University, Tuskegee University and Auburn University. It has been created to bring their combined skills to bear on liquid rocket combustion stability and thrust chamber cooling. The research team involves well established and known researchers in the propulsion community. The cure team provides the knowledge base, research skills, and commitment to achieve an immediate and continuing impact on present and future propulsion issues. through integrated research teams composed of analysts, diagnosticians, and experimentalists working together in an integrated multi-disciplinary program. This paper provides an overview of the program, its objectives and technical approaches. Research on combustion instability and thrust chamber cooling are being accomplished

The Propulsion Research Center at the University of Alabama in Huntsville (UAH) came into being on February 1, 1991. This paper chronicles the growth of the Center, its contribution to the propulsion community and its impact on propulsion education at UAH. The Center mission was formulated with an eye toward educating students in the research process with an emphasis on problems associated with the propulsion community. The unique structure of UAH with separate and distinct research and academic functions posed an interesting set of challenges that had to be met in order to implement a program that bridged the gap between the two. Whereas most university research centers have been organizationally located in a given college, school or department, the UAH Propulsion Research Center is located within the research side of the University and provides an “umbrella” organization under which faculty from various colleges and departments can function. As such, the Center has affiliations with a number of academic departments and centers within UAH. Both graduate and undergraduate academic programs in propulsion were instituted within the Department of Mechanical and Aerospace Engineering concurrently with the establishment of the research program to achieve the mission goal. This paper explores the functioning of the UAH Propulsion Research Center and highlights some of the current research efforts. I. Background A. Purpose: The UAH Propulsion Research Center was originally created to serve the needs of both Alabama students interested in propulsion and the local propulsion community. That local community consisted primarily of the NASA Marshall Space Flight Center (MSFC) and the U. S. Army Aviation and Missile Command (AMCOM) and supporting industry. That role has been expanded in the 13 years of our existence to embrace students from across the United States and provide service to the propulsion community as a whole. B. Goals: The goals of the Center are captured in the Mission Statement that has provided the guiding principles since its inception in 1991. • Educate Students in the research process • Provide new knowledge/leading edge research in propulsion & related topics • Serve as a prime propulsion engineering resource for Alabama, the southeastern U.S. and as a leading resource for the nation. Over the first 13 years of operation, the faculty and students of the Propulsion Research Center have uncovered new ideas in their research and continued to contribute to the propulsion community. A short resume of the PRC achievements is now presented in terms of research achievements and ongoing contributions of our graduates. C. Expenditures: The primary support for the PRC efforts comes from external grants and contracts. Figure 1 shows the expenditures per year of the PRC from its inception in 1991. The PRC stated with investment from state of Alabama, through the UAH Office of the Vice President, Research. The Center achieved the one million dollar per year mark in the first 7 years and will surpass the two million dollar per year mark at 14 years. Total income (including state support) to date is $16,000,000 with $11,200,000 of expenditures through FY03. Figure 2 shows the types of agencies that provided the funds. The state of Alabama has provided 21% of the funds expended to date. This money supports the administration of the PRC through partial support of the Director and a staff assistant. NASA support comprises 34% of the expenditures with major programs in chemical and advanced propulsion. Some of the NASA money is “passed through” to

The Plasmoid Thruster Experiment (PTX) operates by inductively producing plasmoids in a conical theta-pinch coil and subsequently ejecting them at high velocity. An overview of PTX is described in a companion paper. The shape and magnetic field structure of the translating plasmoids will be measured with of an array of inductive magnetic field probes. Six sets of two B-dot probes (for a total of twelve probes) have been constructed for measuring B(sub z) and B(sub theta), the axial and azimuthal components of the magnetic field. The probes were calibrated with a Helmholtz coil, driven alternately by a high-voltage pulser or a signal generator. The probes are wound on a G-10 form, and have an average (calibrated) NA of 9.37 x 10(exp -5) square meters, where N is the number of turns and A is cross-sectional area. The frequency response of the probes was measured over the range from 1 kHz to 10 MHZ. The electron number density n(sub e), electron temperature T(sub e) and velocity v will be determined from measurements taken with a quadruple Langmuir probe, situated in the exhaust chamber. Three of the four probes on the quadruple probe sample the current-voltage characteristic, and from this yield measurements of T(sub e) and n(sub e). The fourth probe provides a measurement of plasma flow velocity. A 6-inch long alumina rod, hollowed with four holes to house the probe wires, is being used to construct the quadruple probe. A variety of propellants will be used, including hydrogen, nitrogen and argon. From the measurements of the plasmoid mass, density, temperature, and velocity, the basic propulsion characteristics of PTX will be evaluated.

An optical plasma jet velocimetry method was developed by monitoring the plasma oscillations within the plasma jet. The natural plasma emission fluctuations within the plasma jet due to the thruster discharge power ripples were recorded in two positions using optical detectors, upstream and downstream in the plasma jet plume. Crosscorrelation of the recorded signals in those two positions are performed. By the study of the peak displacement of the cross-correlation curves, the plasma fluctuation propagation time between the two positions can be found. Hence given the knowledge of distance, the plasma jet velocity can be determined by assuming the fluctuation travels with the flow. Proof of concept tests were conducted to validate this velocimetry method in the plume of a crossed-field MHD accelerator. The MHD accelerator was run at two power levels, about 2kW and 7kW, to provide different plasma jet velocities. The results show this technique gives stable plasma jet velocity measurements. Further validation of the feasibility and accuracy of this technique by comparing with other proven plasma jet velocity measurement techniques are required.

A rocket is defined as an “engine or motor that develops thrust by ejecting a stream of matter rearward, or the missile or vehicle powered by such an engine.” Since the reaction principle involved assumes a self-contained source of energy, a rocket can operate in any medium including space outside the earth's atmosphere, where there is no oxygen to support combustion. This article gives the history of the use of rockets. The laws governing these operations are discussed. The rocket is an energy conversion device that converts potential energy to thermal energy. The energy source can be chemical, electrical, beamed (solar or laser), or nuclear. Nozzle theory is described. Keywords: laws of motion; history; definitions; energy; energy conversion; chemical rockets; rockets; nonchemical rockets; thermodynamics; nozzle theory; efficiency

A report discusses a new multi-turn, multi-lead design for the first generation PT-1 (Plasmoid Thruster) that produces thrust by expelling plasmas with embedded magnetic fields (plasmoids) at high velocities. This thruster is completely electrodeless, capable of using in-situ resources, and offers efficiencies as high as 70 percent at a specific impulse, I(sub sp), of up to 8,000 s. This unit consists of drive and bias coils wound around a ceramic form, and the capacitor bank and switches are an integral part of the assembly. Multiple thrusters may be gauged to inductively recapture unused energy to boost efficiency and to increase the repetition rate, which, in turn increases the average thrust of the system. The thruster assembly can use storable propellants such as H2O, ammonia, and NO, among others. Any available propellant gases can be used to produce an I(sub sp) in the range of 2,000 to 8,000 s with a single-stage thruster. These capabilities will allow the transport of greater payloads to outer planets, especially in the case of an I(sub sp) greater than 6,000 s.

Non-axisymmetric ejector-based combined cycle propulsion systems have received renewed attention due to their potential applicability to next generation space transportation. However, fundamental fluid mechanical mechanisms in even a simple asymmetric ejector system are not well understood. The University of Alabama in Huntsville Propulsion Research Center has an ongoing research program to investigate the induced flow and mixing in rocket driven, non-axisymmetric ejectors. The facility consists of a high-pressure air feed system connected to supersonic nozzles embedded in struts. The struts are installed in a rectangular cross section duct with a contoured inlet. The chamber pressure inside the strut nozzle is varied, and the flow behavior in the duct is examined. This paper summarizes the UAH PRC cold flow ejector research. The paper presents significant results from recent tests on a single nozzle strut. The data from this research provides valuable insight into flow behavior in a non-axisymmetric ejector system. The data will also be valuable for computational fluid dynamic simulations of complex ejector systems. Nomenclature UAH University of Alabama in Huntsville PRC Propulsion Research Center CCP Combined Cycle Propulsion M Mach Number m& Mass Flow P Static Pressure Po Stagnation Pressure T Temperature To Stagnation Temperature A Area γ Ratio of Specific Heats R Specific gas constant ω Suction Ratio Subscripts s secondary flow p primary flow Introduction Combined Cycle Propulsion (CCP) technology shows promise for next generation launch vehicles. Since a combined cycle engine incorporates several modes of engine operation into the same flow path, the optimum performance mode can be utilized in each flight regime. A typical Rocket Based Combined Cycle (RBCC) engine would operate in a rocket or ducted rocket mode for takeoff and initial acceleration to about Mach 2-3, transition to ramjet mode until Mach 4-6, and then transition to scramjet operation. Above Mach 6-8, scramjet operation is unrealistic, and the engine would operate as a pure rocket to accelerate into orbit. The Strutjet is one of the RBCC systems under consideration. This engine consists of a variable geometry duct with vertical engine struts mounted internally. Each strut has several rocket nozzles embedded within it. The engine operates in the four modes discussed earlier: ducted rocket, ramjet, scramjet, and pure rocket. In the airbreathing modes, atmospheric air is ingested into the inlet and flows between the struts into the mixing section. The air oxidizer is mixed with the fuel rich rocket exhaust and combusted. The combustion products are accelerated through an exit nozzle to provide the thrust. Graduate Research Assistant. Student Member AIAA. Graduate Research Assistant, Currently Graduate Student at the University of Maryland. Student Member AIAA. Associate Professor, Mechanical and Aerospace Engineering Dept. Senior Member AIAA Director and Professor of Mechanical and Aerospace Engineering. Fellow AIAA. Copyright 2003 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. A fundamental understanding of ejector physics is an enabling technology to realize an operational RBCC propulsion system. Past theoretical and experimental ejector studies have considered one-dimensional, axisymmetric, or at best two-dimensional geometries. Concepts such as the Strutjet use a complex asymmetric, three-dimensional flow path. The University of Alabama in Huntsville (UAH) Propulsion Research Center (PRC) has an ongoing research program to characterize asymmetric ejector performance in terms of mass flow entrainment and American Institute of Aeronautics and Astronautics 1 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 20-23 July 2003, Huntsville, Alabama AIAA 2003-5231 Copyright © 2003 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

The Strutjet approach to Rocket Based Combined Cycle (RBCC) propulsion depends upon fuel-rich flows from the rocket nozzles and turbine exhaust products mixing with the ingested air for successful operation in the ramjet and scramjet modes. It is desirable to delay this mixing process in the air-augmented mode of operation present during take-off and low speed flight. A scale model of the Strutjet device was built and tested to investigate the mixing of the streams as a function of distance from the Strut exit plane in simulated sea level take-off conditions. The Planar Laser Induced Fluorescence (PLIF) diagnostic method has been employed to observe the mixing of the turbine exhaust gas with the gases from both the primary rockets and the ingested air. The ratio of the pressure in the turbine exhaust to that in the rocket nozzle wall at the point where the two jets meet, is the independent variable in these experiments. Tests were accomplished at values of 1.0 (the original design point), 1.5 and 2.0 for this parameter at 8 locations downstream of the rocket nozzle exit. The results illustrate the development of the mixing zone from the exit plane of the strut to a distance of about 18 equivalent rocket nozzle exit diameters downstream (18"). These images show the turbine exhaust to be confined until a short distance downstream. The expansion into the ingested air is more pronounced at a pressure ratio of 1.0 and 1.5 and shows that mixing with this air would likely begin at a distance of 2" downstream of the nozzle exit plane. Of the pressure ratios tested in this research, 2.0 is the best value for delaying the mixing at the operating conditions considered.

This technical publication (TP) examines performance and design issues associated with magnetic flux compression reactor concepts for nuclear/chemical pulse propulsion and power. Assuming that low-yield microfusion detonations or chemical detonations using high-energy density matter can eventually be realized in practice, various magnetic flux compression concepts are conceivable. In particular, reactors in which a magnetic field would be compressed between an expanding detonation-driven plasma cloud and a stationary structure formed from a high-temperature superconductor are envisioned. Primary interest is accomplishing two important functions: (1) Collimation and reflection of a hot diamagnetic plasma for direct thrust production, and (2) electric power generation for fusion standoff drivers and/or dense plasma formation. In this TP, performance potential is examined, major technical uncertainties related to this concept accessed, and a simple performance model for a radial-mode reactor developed. Flux trapping effectiveness is analyzed using a skin layer methodology, which accounts for magnetic diffusion losses into the plasma armature and the stationary stator. The results of laboratory-scale experiments on magnetic diffusion in bulk-processed type II superconductors are also presented.