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At least 199 records · Page 11

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NASA NTRS1992

Micro Electric Propulsion Feasibility

Miniature, 50 kg class, strategic satellites intended for extended deployment in space require an on-board propulsion capability to perform needed attitude control adjustments and drag compensation maneuvers. Even on such very small spacecraft, these orbit maintenance functions can be significant and result in a substantial propellant mass requirement. Development of advanced propulsion technology could reduce this propellant mass significantly, and thereby maximize the payload capability of these spacecraft. In addition, spacecraft maneuverability could be enhanced and/or multi-year mission lifetimes realized. These benefits cut spacecraft replacement costs, and reduce services needed to maintain the launch vehicles. For SDIO brilliant pebble spacecraft, a miniaturized hydrazine propulsion system provides both boost and divert thrust control. This type of propulsion system is highly integrated and is capable of delivering large thrust levels for short time periods. However, orbit maintenance functions such as drag make-up require only very small velocity corrections. Using the boost and/or divert thrusters for these small corrections exposes this highly integrated propulsion system to continuous on/off cycling and thereby increases the risk of system failure. Furthermore, since drag compensation velocity corrections would be orders of magnitude less than these thrusters were designed to deliver, their effective specific impulse would be expected to be lower when operated at very short pulse lengths. The net result of these effects would be a significant depletion of the on-board hydrazine propellant supply throughout the mission, and a reduced propulsion system reliability, both of which would degrade the interceptors usefulness. In addition to SDIO brilliant pebble spacecraft, comparably small spacecraft can be anticipated for other future strategic defense applications such as surveillance and communication. For such spacecraft, high capability and reliability, minimal detectability and low cost are requirements. All these miniature spacecraft share a common characteristic: because of their on-board electronic equipment they have, by design, solar order 50-100 W. In a relative sense, such spacecraft are power rich when compared to other larger spacecraft. This power rich situation is offset by very tight mass budgets, which make reductions in propellant mass requirements a key issue in meeting overall spacecraft minimum mass goals. In principle, power rich and propellant poor brilliant pebbles class spacecraft can benefit from using high specific impulse electric propulsion to reduce chemical propellant mass requirements. However, at power levels of order 50 W, arcjets cannot be made to function, ion thrusters are too complex and heavy and resistojets have too low a specific impulse. Recognizing these capability limitations in existing electric propulsion technology, the SDIO/IST sponsored the Phase I SBIR Micro Electric Propulsion (MEP) thruster study described in this report. The objective of this study was to examine the feasibility of developing a very simple, low mass and small volume, electric thruster for operation on hydrazine at less than 100 W of input power. The feasibility of developing such a MEP thruster was successfully demonstrated by EPL by the discovery of a novel plasma acceleration process. The sections in this report summarize the approach, test results and major accomplishments of this proof-of-concept program.

Aston, Graeme↗

NASA NTRS1989

Feasibility study of a single, elliptical heliocentric Earth-Mars trajectory

The initial intent of this design project was to evaluate the existence and feasibility of a single elliptical heliocentric Earth/Mars trajectory. This trajectory was constrained to encounter Mars twice in its orbit, within a time interval of 15 to 180 Earth days between encounters. The single ellipse restriction was soon found to be prohibitive for reasons shown later. Therefore, the approach taken in the design of the round-trip mission to Mars was to construct single-leg trajectories which connected two planets on two prescribed dates. Three methods of trajectory design were developed. Method 1 is an eclectic approach and employs Gaussian Orbit Determination (Method 1A) and Lambert-Euler Preliminary Orbit Determination (Method 1B) in conjunction with each other. Method 2 is an additional version of Lambert's Solution to orbit determination, and both a coplanar and a noncoplanar solution were developed within Method 2. In each of these methods, the fundamental variables are two position vectors and the time between the position vectors. In all methods, the motion was considered Keplerian motion and the reference frame origin was located at the sun. Perturbative effects were not considered in Method 1. The feasibility study of round-trip Earth/Mars trajectories maintains generality by considering only heliocentric trajectory parameters and planetary approach conditions. The coordinates and velocity components of the planets, for the standard epoch J2000, were computed from an approximate set of osculating elements by the procedure outlined in an ephemeris of coordinates.

Blake, M.↗

NASA NTRS1993

Investigation of the feasibility of optical diagnostic measurements at the exit of the SSME

Under Contract NAS8-36861 sponsored by NASA Marshall Space Flight Center, the United Technologies Research Center is conducting an investigation of the feasibility of remote optical diagnostics to measure temperature, species concentration and velocity at the exit of the Space Shuttle Main Engine (SSME). This is a two phase study consisting of a conceptual design phase followed by a laboratory experimental investigation. The first task of the conceptual design studies is to screen and evaluate the techniques which can be used for the measurements. The second task is to select the most promising technique or techniques, if as expected, more than one type of measurement must be used to measure all the flow variables of interest. The third task is to examine in detail analytically the capabilities and limitations of the selected technique(s). The results of this study are described in the section of this report entitled Conceptual Design Investigations. The conceptual design studies identified spontaneous Raman scattering and photodissociative flow-tagging for measurements respectively of gas temperature and major species concentration and for velocity. These techniques and others that were considered are described in the section describing the conceptual design. The objective of the second phase of investigations was to investigate experimentally the techniques identified in the first phase. The first task of the experimental feasibility study is to design and assemble laboratory scale experimental apparatus to evaluate the best approaches for SSME exit optical diagnostics for temperature, species concentrations and velocity, as selected in the Phase I conceptual design study. The second task is to evaluate performance, investigate limitations, and establish actual diagnostic capabilities, accuracies and precision for the selected optical systems. The third task is to evaluate design requirements and system trade-offs of conceptual instruments. Spontaneous Raman scattering excited by a KrF excimer laser pulse was investigated for SSME exit plane temperature and major species concentration measurements. The relative concentrations of molecular hydrogen and water vapor would be determined by measuring the integrated Q-branch scattering signals through narrow bandpass filters in front of photomultipliers. The temperature would be determined by comparing the signal from a single hydrogen rotational Raman line to the total hydrogen Q-branch signal. The rotational Raman line would be isolated by a monochromator and detected with a PMT.

Shirley, John A.↗

NASA NTRS1992

Direct solar pumping of semiconductor lasers: A feasibility study

This report describes results of NASA Grant NAG-1-1148, entitled Direct Solar Pumping of Semiconductor Lasers: A Feasibility Study. The goals of this study were to provide a preliminary assessment of the feasibility of pumping semiconductor lasers in space with directly focused sunlight and to identify semiconductor laser structures expected to operate at the lowest possible focusing intensities. It should be emphasized that the structures under consideration would provide direct optical-to-optical conversion of sunlight into laser light in a single crystal, in contrast to a configuration consisting of a solar cell or storage battery electrically pumping a current injection laser. With external modulation, such lasers could perhaps be efficient sources for intersatellite communications. We proposed specifically to develop a theoretical model of semiconductor quantum-well lasers photopumped by a broadband source, test it against existing experimental data where possible, and apply it to estimating solar pumping requirements and identifying optimum structures for operation at low pump intensities. These tasks have been accomplished, as described in this report of our completed project. The report is organized as follows: Some general considerations relevant to the solar-pumped semiconductor laser problem are discussed in Section 2, and the types of structures chosen for specific investigation are described. The details of the laser model we developed for this work are then outlined in Section 3. In Section 4, results of our study are presented, including designs for optimum lattice-matched and strained-layer solar-pumped quantum-well lasers and threshold pumping estimates for these structures. It was hoped at the outset of this work that structures could be identified which could be expected to operate continuously at solar photoexcitation intensities of several thousand suns, and this indeed turned out to be the case as described in this section. Our project is summarized in Section 5, and information on publications resulting from this work is provided in Section 6.

Anderson, Neal G.↗

NASA NTRS1994

An optimization program based on the method of feasible directions: Theory and users guide

The theory and user instructions for an optimization code based on the method of feasible directions are presented. The code was written for wide distribution and ease of attachment to other simulation software. Although the theory of the method of feasible direction was developed in the 1960's, many considerations are involved in its actual implementation as a computer code. Included in the code are a number of features to improve robustness in optimization. The search direction is obtained by solving a quadratic program using an interior method based on Karmarkar's algorithm. The theory is discussed, focusing on the important and often overlooked role played by the various parameters guiding the iterations within the program. Also discussed is a robust approach for handling infeasible starting points. The code was validated by solving a variety of structural optimization test problems that have known solutions obtained by other optimization codes. It has been observed that this code is accurate and robust: it has solved a variety of problems from different starting points. However, the code is inefficient in that it takes considerable CPU time as compared with certain other available codes. Further work is required to improve its efficiency while retaining its robustness.

Ashok D. Belegundu↗

NASA NTRS1994

Feasibility study, software design, layout and simulation of a two-dimensional Fast Fourier Transform machine for use in optical array interferometry

The goal of this project was the feasibility study of a particular architecture of a digital signal processing machine operating in real time which could do in a pipeline fashion the computation of the fast Fourier transform (FFT) of a time-domain sampled complex digital data stream. The particular architecture makes use of simple identical processors (called inner product processors) in a linear organization called a systolic array. Through computer simulation the new architecture to compute the FFT with systolic arrays was proved to be viable, and computed the FFT correctly and with the predicted particulars of operation. Integrated circuits to compute the operations expected of the vital node of the systolic architecture were proven feasible, and even with a 2 micron VLSI technology can execute the required operations in the required time. Actual construction of the integrated circuits was successful in one variant (fixed point) and unsuccessful in the other (floating point).

Boriakoff, Valentin↗

NASA NTRS1995

Feasibility of flywheel energy storage systems for applications in future space missions

The objective of this study was to examine the overall feasibility of deploying electromechanical flywheel systems in space used for excess energy storage. Results of previous Rocketdyne studies have shown that the flywheel concept has a number of advantages over the NiH2 battery, including higher specific energy, longer life and high roundtrip efficiency. Based on this prior work, this current study was broken into four subtasks. The first subtask investigated the feasibility of replacing the NiH2 battery orbital replacement unit (ORU) on the international space station (ISSA) with a flywheel ORU. In addition, a conceptual design of a generic flywheel demonstrator experiment implemented on the ISSA was completed. An assessment of the life cycle cost benefits of replacing the station battery energy storage ORU's with flywheel ORU's was performed. A fourth task generated a top-level development plan for critical flywheel technologies, the flywheel demonstrator experiments and its evolution into the production unit flywheel replacement ORU.

Santo, G. Espiritu↗

NASA NTRS1996

Feasibility Study of a Rotorcraft Health and Usage Monitoring System (HUMS): Results of Operator's Evaluation

The objective was to evaluate the feasibility of a state-of-the-art health and usage monitoring system (HUMS) to provide monitoring of critical mechanical systems on the helicopter, including motors, drive train, engines, and life-limited components. The implementation of HUMS and cost integration with current maintenance procedures was assessed from the operator's viewpoint in order to achieve expected benefits from these systems, such as enhanced safety, reduced maintenance cost, and increased availability. An operational HUMS that was installed and operated under an independent flight trial program was used as a basis for this study. The HUMS equipment and software were commercially available. Based on the results of the feasibility study, the HUMS used in the flight trial program generally demonstrated a high level of reliability in monitoring the rotor system, engines, drive train, and life-limited components. The system acted as a sentinel to warn of impending failures. A worn tail rotor pitch bearing was detected by HUMS, which had the capability for self testing to diagnose system and sensor faults. Examples of potential payback to the operator with HUMS were identified, including reduced insurance cost through enhanced safety, lower operating costs derived from maintenance credits, increased aircraft availability, and improved operating efficiency. The interfacing of HUMS with current operational procedures was assessed to require only minimal revisions to the operator's maintenance manuals. Finally the success in realizing the potential benefits from HUMS technology was found to depend on the operator, helicopter manufacturer, regulator (FAA), and HUMS supplier working together.

Romero, Raylund↗

NASA NTRS1998

The Feasibility of Bulk Crystallization as an Industrial Purification and Production Technique for Proteins

Bulk crystallization in stirred vessels is used industrially for the recovery and purification of many inorganic and organic materials. Although much has been written on the crystallization of proteins for X-ray diffraction analysis, very little has been reported on the application of bulk crystallization in stirred vessels. In this study, a 1-liter, seeded, stirred, batch crystallizer was used with ovalbumin as a model protein to test the feasibility of this crystallization method as a recovery and purification process for proteins. Results were obtained for ovalbumin solubility, nucleation thresholds, crystal breakage and crystal growth kinetics in bulk solution under a range of operating conditions of pH and ammonium sulphate concentration (Judge et al., 1996). Experiments were also performed to determine the degree of purification that can be achieved by the crystallization of ovalbumin from a mixture of proteins. The effect of the presence of these proteins upon the ovalbumin crystal growth kinetics was also investigated (Judge et al., 1995). All of these aspects are essential for the design of bulk crystallization processes which have not previously been reported for proteins. Results from a second study that investigated the effect of structurally different proteins on the solubility, crystal growth rates and crystal purity of chicken egg white lysozyme are also presented (Judge et al., 1997). In this case face growth rates were measured using lysozyme purified by liquid chromatography and the effect of the addition of specific protein impurities were observed on the (110) and (101) crystal faces. In these two studies the results are presented to show the feasibility and purifying ability of crystallization as a production process for proteins.

Judge, Russell A.↗

NASA NTRS1999

Performance and Feasibility Analysis of a Wind Turbine Power System for Use on Mars

A wind turbine power system for future missions to the Martian surface was studied for performance and feasibility. A C++ program was developed from existing FORTRAN code to analyze the power capabilities of wind turbines under different environments and design philosophies. Power output, efficiency, torque, thrust, and other performance criteria could be computed given design geometries, atmospheric conditions, and airfoil behavior. After reviewing performance of such a wind turbine, a conceptual system design was modeled to evaluate feasibility. More analysis code was developed to study and optimize the overall structural design. Findings of this preliminary study show that turbine power output on Mars could be as high as several hundred kilowatts. The optimized conceptual design examined here would have a power output of 104 kW, total mass of 1910 kg, and specific power of 54.6 W/kg.

Lichter, Matthew D.↗

NASA NTRS1998

Feasibility Study for Casting of High Temperature Refractory Superalloy Composites

Abstract This study investigated the feasibility of using conventional casting technique to fabricate refractory wires reinforced superalloy composites. These composites were being developed for advanced rocket engine turbine blades and other high temperature applications operating up to 2000 F. Several types of refractory metal wires such as W- Th, W-Re, Mo-Hf-C and W-HF-C reinforced waspaloy were experimentally cast and heat treated at 2000 F up to 48 hrs. Scanning electron microscope analysis was conducted in regions adjacent to the wire-matrix interface to determine the reaction zone and chemical compatibility resulting from material interdiffusion. It was concluded that fabrication using conventional casting may be feasible because the wire-matrix reaction zone thickness was comparable to similar composites produced by arc-sprayed monotape with hot isostatic pressing technique, Moreover, it was also found that the chemical compatibility could be improved significantly through a slight modification of the superalloy matrix compositions.

Lee, Jonathan A.↗

NASA NTRS2000

Lack of Penetration in Friction Stir Welds: Effects on Mechanical Properties and NDE Feasibility

This presentation reviews the issue of lack of penetration (LOP) in Friction Stir Welding and the feasibility of using non-destructive tests to detect . Friction Stir Welding takes place in the solid phase below the melting point of the materials to be joined. It thus gives the ability to join materials which are difficult to fusion weld, for example 2000 and 7000 aluminium alloys. This process though can result in a lack of penetration, due to an incomplete penetration of the DXZ. This is frequently referred to as a "kissing bond", which requires micro examination to detect. The presentation then discusses the surface crack tension tests. It then reviews the simulated service test and results. It then discusses the feasibility of using non-destructive examination to detect LOP, the forms of test which can be used, and the results the tests.

Kinchen, David G.↗

NASA NTRS1998

A Feasibility Study of Synthesizing Subsurfaces Modeled with Computational Neural Networks

This paper investigates the feasibility of synthesizing substructures modeled with computational neural networks. Substructures are modeled individually with computational neural networks and the response of the assembled structure is predicted by synthesizing the neural networks. A superposition approach is applied to synthesize models for statically determinate substructures while an interface displacement collocation approach is used to synthesize statically indeterminate substructure models. Beam and plate substructures along with components of a complicated Next Generation Space Telescope (NGST) model are used in this feasibility study. In this paper, the limitations and difficulties of synthesizing substructures modeled with neural networks are also discussed.

Wang, John T.↗

NASA NTRS2004

Pilot In Command: A Feasibility Assessment of Autonomous Flight Management Operations

Several years of NASA research have produced the air traffic management operational concept of Autonomous Flight Management with high potential for operational feasibility, significant system and user benefits, and safety. Among the chief potential benefits are demand-adaptive or scalable capacity, user flexibility and autonomy that may finally enable truly successful business strategies, and compatibility with current-day operations such that the implementation rate can be driven from within the user community. A concept summary of Autonomous Flight Management is provided, including a description of how these operations would integrate in shared airspace with existing ground-controlled flight operations. The mechanisms enabling the primary benefits are discussed, and key findings of a feasibility assessment of airborne autonomous operations are summarized. Concept characteristics that impact safety are presented, and the potential for initially implementing Autonomous Flight Management is discussed.

Wing, David J.↗

NASA NTRS2004

Spaceflight Operations Services Grid (SOSG) Prototype Implementation and Feasibility Study

Science Operations Services Grid is focusing on building a prototype grid-based environment that incorporates existing and new spaceflight services to enable current and future NASA programs with cost savings and new and evolvable methods to conduct science in a distributed environment. The Science Operations Services Grid (SOSG) will provide a distributed environment for widely disparate organizations to conduct their systems and processes in a more efficient and cost effective manner. These organizations include those that: 1) engage in space-based science and operations, 2) develop space-based systems and processes, and 3) conduct scientific research, bringing together disparate scientific disciplines like geology and oceanography to create new information. In addition educational outreach will be significantly enhanced by providing to schools the same tools used by NASA with the ability of the schools to actively participate on many levels in the science generated by NASA from space and on the ground. The services range from voice, video and telemetry processing and display to data mining, high level processing and visualization tools all accessible from a single portal. In this environment, users would not require high end systems or processes at their home locations to use these services. Also, the user would need to know minimal details about the applications in order to utilize the services. In addition, security at all levels is an underlying goal of the project. The Science Operations Services Grid will focus on four tools that are currently used by the ISS Payload community along with nine more that are new to the community. Under the prototype four Grid virtual organizations PO) will be developed to represent four types of users. They are a Payload (experimenters) VO, a Flight Controllers VO, an Engineering and Science Collaborators VO and an Education and Public Outreach VO. The User-based services will be implemented to replicate the operational voice, video, telemetry and commanding systems. Once the User-based services are in place, they will be analyzed to establish feasibility for Grid enabling. If feasible then each User-based service will be Grid enabled. The remaining non-Grid services if not already Web enabled will be so enabled. In the end, four portals will be developed one for each VO. Each portal will contain the appropriate User-based services required for that VO to operate.

Bradford, Robert N.↗

NASA NTRS2005

Preliminary Dynamic Feasibility and Analysis of a Spherical, Wind-Driven (Tumbleweed), Martian Rover

The process and findings are presented from a preliminary feasibility study examining the dynamics characteristics of a spherical wind-driven (or Tumbleweed) rover, which is intended for exploration of the Martian surface. The results of an initial feasibility study involving several worst-case mobility situations that a Tumbleweed rover might encounter on the surface of Mars are discussed. Additional topics include the evaluation of several commercially available analysis software packages that were examined as possible platforms for the development of a Monte Carlo Tumbleweed mission simulation tool. This evaluation lead to the development of the Mars Tumbleweed Monte Carlo Simulator (or Tumbleweed Simulator) using the Vortex physics software package from CM-Labs, Inc. Discussions regarding the development and evaluation of the Tumbleweed Simulator, as well as the results of a preliminary analysis using the tool are also presented. Finally, a brief conclusions section is presented.

Flick, John J.↗

NASA NTRS2005

Feasibility Assessment for Pressure Casting of Ceramic-Aluminum Composites for NASA's Propulsion Applications

Feasibility assessment of pressure casting of ceramic-aluminum composites for NASA% propulsion applications is summarized. A combination of several demonstration projects to produce three unique components for liquid hydrogen-oxygen rocket engine% flanges, valves and turbo-pump housing are conducted. These components are made from boron carbide, silicon carbide and alumina powders fabricated into complex net shaped parts using dry green powder compaction, slip casting or a novel 3D ink-jet printing process, followed by sintering to produce performs that can be pressure cast by infiltration with molten aluminum. I n addition, joining techniques are also explored to insure that these components can be assembled into a structure without degrading their highly tailored properties. The feasibility assessment was made to determine if these new materials could provide a significant weight savings, thereby reducing vehicle launch costs, while being durable materials to increase safety and performance for propulsion system.

Lee, Jonathan A.↗

NASA NTRS2004

REP Concept Feasibility Study

Radioisotope Electric Propulsion (REP) may have the potential to provide certain advantages, over conventional chemical propulsion, for outer planetary exploration involving small bodies and long term investigations for medium class missions requiring power comparable to past outer planetary exploration missions. This paper describes a study that investigates the concept s feasibility by performing a preliminary conceptual design of an REP-based spacecraft for a design reference mission. The mission utilizes a spacecraft with a radioisotope power supply less than one kilowatt while operating for a minimum of 10-years. A key element of the REP spacecraft is to ensure sustained science return by orbiting or flying in formation with selected targets. Utilizing current and impending technological advances, this study finds that at a conceptual design level a small body REP orbiter/explorer appears to be feasible for the design reference mission selected for this study.

Edwards, Daryl A.↗