NASA Propulsion Engineering Research Center, volume 2

On 8-9 Sep. 1993, the Propulsion Engineering Research Center (PERC) at The Pennsylvania State University held its Fifth Annual Symposium. PERC was initiated in 1988 by a grant from the NASA Office of Aeronautics and Space Technology as a part of the University Space Engineering Research Center (USERC) program; the purpose of the USERC program is to replenish and enhance the capabilities of our Nation's engineering community to meet its future space technology needs. The Centers are designed to advance the state-of-the-art in key space-related engineering disciplines and to promote and support engineering education for the next generation of engineers for the national space program and related commercial space endeavors. Research on the following areas was initiated: liquid, solid, and hybrid chemical propulsion, nuclear propulsion, electrical propulsion, and advanced propulsion concepts

Real-time dynamic model learning and adaptation for underwater vehicles

Precision control of unmanned underwater vehicles (UUVs) requires accurate knowledge of the dynamic characteristics of the vehicles. However, developing such models are time and resource intensive. The problem is further exacerbated by the sensitivity of the dynamic model to vehicle configuration. This is particularly true for hovering-class UUVs since sensor payloads are often mounted outside the vehicle body. Methods are investigated in this thesis to learn the dynamic model for such a hovering-class UUV in real time from motion and position measurements. Several system identification techniques, including gradient estimation, Bayesian estimation, neural network estimation, and recursive linear least square estimation, are employed to estimate equations of motion coefficients. Experimental values are obtained for the surge, sway, heave, and yaw degrees of freedom. Theoretical results are obtained for the roll and pitch degrees of freedom. The experimentally obtained model is then compared to the true vehicle behavior.http://archive.org/details/realtimedynamicm1094537741Lieutenant, United States NavyApproved for public release; distribution is unlimited

Research reports: 1994 NASA/ASEE Summer Faculty Fellowship Program

For the 30th consecutive year, a NASA/ASEE Summer Faculty Fellowship Program was conducted at the Marshall Space Flight Center (MSFC). The basic objectives of the programs, which are in the 31st year of operation nationally, are (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate an exchange of ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of participants' institutions; and (4) to contribute to the research objectives of the NASA centers. The Faculty Fellows spent 10 weeks at MSFC engaged in a research project compatible with their interests and background and worked in collaboration with a NASA/MSFC colleague. This document is a compilation of Fellows' reports on their research during the summer of 1994

INVESTIGATION OF OCEAN ACOUSTICS USING AUTONOMOUS INSTRUMENTATION TO QUANTIFY THE WATER-SEDIMENT BOUNDARY PROPERTIES

Sound propagation in shallow water is characterized by interaction with the oceans surface, volume, and bottom. In many coastal margin regions, including the Eastern U.S. continental shelf and the coastal seas of China, the bottom is composed of a depositional sandy-silty top layer. Previous measurements of narrow and broadband sound transmission at frequencies from 100 Hz to 1 kHz in these regions are consistent with waveguide calculations based on depth and frequency dependent sound speed, attenuation and density profiles. Theoretical predictions for the frequency dependence of attenuation vary from quadratic for the porous media model of M.A. Biot to linear for various competing models. Results from experiments performed under known conditions with sandy bottoms, however, have agreed with attenuation proportional to f1.84, which is slightly less than the theoretical value of f2 [Zhou and Zhang, J. Acoust. Soc. Am. 117, 2494]. This dissertation presents a reexamination of the fundamental considerations in the Biot derivation and leads to a simplification of the theory that can be coupled with site-specific, depth dependent attenuation and sound speed profiles to explain the observed frequency dependence. Long-range sound transmission measurements in a known waveguide can be used to estimate the site-specific sediment attenuation properties, but the costs and time associated with such at-sea experiments using traditional measurement techniques can be prohibitive. Here a new measurement tool consisting of an autonomous underwater vehicle and a small, low noise, towed hydrophone array was developed and used to obtain accurate long-range sound transmission measurements efficiently and cost effectively. To demonstrate this capability and to determine the modal and intrinsic attenuation characteristics, experiments were conducted in a carefully surveyed area in Nantucket Sound. A best-fit comparison between measured results and calculated results, while varying attenuation parameters, revealed the estimated power law exponent to be 1.87 between 220.5 and 1228 Hz. These results demonstrate the utility of this new cost effective and accurate measurement system. The sound transmission results, when compared with calculations based on the modified Biot theory, are shown to explain the observed frequency dependence.National Defense Science and Engineering Graduate Fellowship through the American Society for Engineering Education, the Office of Naval Research, and the Woods Hole Oceanographic Institution

JPL Quarterly Technical Review, Volume 2, No. 1, April 1972

Mariner spacecraft equipment, propulsion systems, telemetry, and spacecraft trackin

Bibliography of Lewis Research Center technical publications announced in 1989

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1989. All the publications were announced in the 1989 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Bibliography of Lewis Research Center technical publications announced in 1985

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1985. All the publications were announced in the 1985 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

The deep space network, volume 15

The DSN progress is reported in flight project support, TDA research and technology, network engineering, hardware and software implementation, and operations. Topics discussed include: DSN functions and facilities, planetary flight projects, tracking and ground-based navigation, communications, data processing, network control system, and deep space stations

Numerical and Experimental Characterization of Throttleable Hybrid Propulsion Systems. Caratterizzazione Numerica e Sperimentale di Sistemi Propulsivi Ibridi a Spinta Variabile

The 1960s have been flourishing years for hybrid rocket propulsion: the thirst for knowledge pushed the engineers of those years to design and test any kind of motor configuration, and for several possible applications. Many projects of those years are fascinating and outstanding still nowadays. The cold war era had extinguished any enthusiasm and interest for hybrids for years. It is approximately at the beginning of the '90s that a renew interest for hybrids has come alive, since, besides the pure performance, affordability and safety have become a must. Hybrids are safe, simple, reliable, low cost and throttleable. All these characteristics make them suitable for several applications, not necessarily in replacement of solids and liquids, but possibly complementary. The TRL of hybrids has still to be improved in order to put hybrids on the market. Among the aforementioned peculiarities of hybrids, their throttleability is the object of the present research. This work is focused on the investigation of a high performing throttleable hybrid motor, conceived for soft-landing applications. The main purpose of the research is to develop and characterize a motor in the 1kN-class, with characteristics like: high performance at different operative conditions, both in terms of regression rate and combustion efficiency enhancement, safety and simplicity, reliability. The research is part of a wider framework: a EU FP7 granted project, called ``SPARTAN'', leaded by Thales Alenia Space, and aimed at developing a soft-lander demonstrator for planetary exploration, provided by a hybrid propulsion system. The University of Padova is partner of the project, so the preliminary design guidelines of the motor have been defined according to the requirements of the SPARTAN consortium. The motor considered burns HTPB as fuel and 87.5%H2O2. High performance is expected to be achieved by means of vortex injection. The selection of H2O2 as oxidizer has been made to take advantage from its many qualities, like high density and high OF ratio, non-toxicity, possibility to decompose it through a catalyst. Thanks to this last aspect, fuel ignition is expected to be accomplished thanks to the hot gases resulting from oxidizer decomposition. The doctoral research has been conducted combining several tools in synergy: analytic models, CFD simulations and experimental tests. The analytic models have supported the comprehension of the physical processes involved. The numerical simulations have been useful tools both to provide indications for final design purposes and to investigate in detail aspects of the internal ballistic of the motor, which were difficult to be observed in experimental tests. Finally, experimental tests have been conducted to validate the numerical prediction and assess the achievement of the desired and expected results. As a first step, once defined the preliminary design of the motor according to the SPARTAN requirements, a deep CFD investigation has been performed, in order to finalize the design. Preliminary CFD simulations have been carried out on a motor configuration already developed and tested at UPD, in order to study and characterize the physics beyond vortex injection, and thus assess its effectiveness in enhancing the hybrid motor performance. The numerical results have been compared with an analytic model of the vortex flowfield. The outcome of this phase has been compared with the experimental data available. In a second phase, the preliminary design produced within SPARTAN has been simulated to predict its performance and its sensitivity to some changes in the motor configuration and operative conditions. A prediction of the expected performance and some useful indications for the experimental tests are the main output of this second phase. Then experimental tests of the motor have been performed to evaluate the actual performance at different throttling levels. In order to overcome the issues related to handle and store hydrogen peroxide in high concentration, the design of the experimental test-bed foresaw the integration of the hybrid motor with a gas generator, responsible of reproducing 87.5% H2O2 in decomposed condition, as it would be passing through a catalyst. The mixture produced inside the gas generator is then injected as oxidizer into the combustion chamber of the hybrid motor. The experimental test-bed has been integrated and a preliminary phase of calibrations has been required to assess the correct functioning of the feed lines. Moreover a complete diagnostic system has been defined and installed, in order to have a full and accurate monitoring of the interesting parameters. Many tests have been performed at the beginning, to optimize the functioning of each subsystem composing the test-bed, and in order to obtain the correct oxidizer mixture and to assure HTPB ignition. Finally, the hybrid motor has been successfully tested at three different fixed throttling levels: full thrust, 75% thrust and 50% thrust. Fuel ignition has been achieved at each throttling level, and the dependency of the ignition delay from the throttling level has been considered. The performance of the motor has been analyzed at each level, in terms of: resulting regression rate, as a function of the oxidizer flux; combustion efficiency; combustion stability. A comparison between the performance obtained at each level has been performed. Any possible evidence of nozzle throat erosion has been monitored. Finally, the results have been compared with the reference regression rate law, proper of 87.5%H2O2-HTPB, in order to demonstrate the effectiveness of the gas generator in simulating decomposed hydrogen peroxide in high concentration. The actual mixture composition has also been estimated

Bibliography of Lewis Research Center technical publications announced in 1986

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1986. All the publications were announced in the 1986 issues of Scientific and Technical Aerospace Reports (STAR) and/or International Aerospace Abstracts (IAA). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses