ALBERT

Description: Bottom sediment resuspension frequency, duration and extent (% of bottom sediments affected) were characterized for the fifteen month period from September 1995 to January 1997 for the Barataria Basin, LA. An empirical model of sediment resuspension as a function of wind speed, direction, fetch and water depth was derived from wave theory. Water column turbidity was examined by processing remotely sensed radiance information from visible and near-IR AVHRR imagery. Based on model predictions, wind induced resuspension occurred during all seasons of this study. Seasonal characteristics for resuspension reveal that late fall, winter and early spring are the periods of most frequent and intense resuspension. Model predictions of the critical wind speed required to induce resuspension indicate that winds of 4 m/s (averaged over all wind directions resuspend approximately 50% of bottom sediments in the water bodies examined. Winds of this magnitude (4 m/s) occurred for 80% of the time during the late fall, winter and early spring and for approximately 30% of the time during the summer. More than 50% of the bottom sedimets are resuspended throughout the year, indicating the importance of resuspension as a process affecting sediment and biogeochemical fluxes in the Barataria Basin.

Description: Propellent injector development at MSFC includes experimental analysis using optical techniques, such as Raman, fluorescence, or Mie scattering. For the application of spontaneous Raman scattering to hydrocarbon-fueled flows a technique needs to be developed to remove the interfering polycyclic aromatic hydrocarbon fluorescence from the relatively weak Raman signals. A current application of such a technique is to the analysis of the mixing and combustion performance of multijet, impinging-jet candidate fuel injectors for the baseline Mars ascent engine, which will bum methane and liquid oxygen produced in-situ on Mars to reduce the propellent mass transported to Mars for future manned Mars missions. The present technique takes advantage of the strongly polarized nature of Raman scattering. It is shown to be discernable from unpolarized fluorescence interference by subtracting one polarized image from another. Both of these polarized images are obtained from a single laser pulse by using a polarization-separating calcite rhomb mounted in the imaging spectrograph. A demonstration in a propane-air flame is presented.

Description: Changes in the ocean angular momentum (OAM) components about the equatorial axes, either due to fluctuations in currents or bottom pressure (mass redistribution), can induce movements of the Earth's pole of rotation, commonly referred to as polar motion or wobble. Output from a 1 deg resolution ocean model is used to calculate the effective equatorial OAM functions chi(sub 1, sup O) and chi(sub 2, sup O), corresponding to polar motion excitation about the equatorial axis pointing to the Greenwich and 90 deg E meridians, respectively. Time series of chi(sup O) are combined with similar atmospheric series chi(sup A), computed from the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalyses, to interpret the observed low-frequency polar motion excitation for the period 1985-1996. Results indicate that the oceans are a very important excitation source for the Chandler (approximately 433 days), annual, and semiannual wobbles, providing for much better amplitude and phase agreement with the observed excitation at these periods, in comparison with what is obtained when only the atmosphere is considered. Both oceanic mass and motion terms are found to be important but with mass signals having somewhat larger amplitudes. The role of regional variability in ocean currents and bottom pressure in contributing to chi(sup O) signals is quantified. Midlatitude regions (approximately 30 deg - 70 deg) figure prominently as places of strong local oceanic excitation signals. The North Pacific basin is found to be generally important for chi(sup O) excitation, while the Southern Ocean is important for both chi(sub 1, sup O) and chi(sub 2, sup O). The largest positive covariances of local with global chi(sup O) signals occur in the Kuroshio region near the western boundary of the North Pacific for chi(sub 1, sup O) and southwest of Australia for chi(sub 2, sup O).

Description: An Inertial-Electrostatic Confinement (IEC) device was assembled at the Marshall Space Flight Center (MSFC) Propulsion Research Center (PRC) to study the possibility of using EEC technology for deep space propulsion and power. Inertial-Electrostatic Confinement is capable of containing a nuclear fusion plasma in a series of virtual potential wells. These wells would substantially increase plasma confinement, possibly leading towards a high-gain, breakthrough fusion device. A one-foot in diameter IEC vessel was borrowed from the Fusion Studies Laboratory at the University of Illinois@Urbana-Champaign for the summer. This device was used in initial parameterization studies in order to design a larger, actively cooled device for permanent use at the PRC.

Description: The Fastrac rocket engine is currently being developed for the X-34 technology demonstrator vehicle. The engine performance model must be calibrated to support accurate performance prediction. Data reduction is the process of estimating hardware characteristics from available test data, and is essential for effective performance model calibration and prediction. A new data reduction procedure was developed, implemented, and tested using data from Fastrac engine tests. The procedure selects hardware and test measurements to use in the reduction process based on examination of the model influence matrix condition number. Predicted hardware characteristics are recovered from the solution of a quadratic programming problem. Computational tests indicate that the new procedure provides a significant improvement in test data reduction capability. Enhancements include improved test data utilization and time history data reduction capability. The new method is generically applicable to other systems.

Description: A status of MEMS-based micropropulsion activities conducted at JPL will be given. These activities include work conducted on the so called Vaporizing Liquid Micro-Thruster (VLM) which recently underwent proof-of-concept testing, demonstrating the ability to vaporize water propellant at 2 W and 2 V. Micro-ion engine technologies, such m field emitter arrays and micro-grids are being studied. Focus in the field emitter area is on arrays able to survive in thruster plumes and micro-ion engine plasmas to serve as neutralizers aW engine cathodes. Integrated, batch-fabricated Ion repeller grid structures are being studied as well as different emitter tip materials are being investigated to meet these goals. A micro-isolation valve is being studied to isolate microspacecraft feed system during long interplanetary cruises, avoiding leakage and prolonging lifetime and reliability of such systems. This concept relies on the melting of a thin silicon barrier. Burst pressure values as high as 2,900 psig were obtained for these valves and power requirements to melt barriers ranging between 10 - 50 microns in thickness, as determined through thermal finite element calculations, varied between 10 - 30 W to be applied over a duration of merely 0.5 ms.

Description: Portable electromagnetic antiproton traps are now in a state of realization. This allows facilities like NASA Marshall Space Flight Center to conduct antimatter research remote to production sites. MSFC is currently developing a trap to store 10(exp 12) antiprotons for a twenty-day half-life period to be used in future experiments including antimatter plasma guns, antimatter-initiated microfusion, and the synthesis of antihydrogen for space propulsion applications. In 1998, issues including design, safety and transportation were considered for the MSFC High Performance Antimatter Trap (HiPAT). Radial diffusion and annihilation losses of antiprotons prompted the use of a 4 Tesla superconducting magnet and a 20 KV electrostatic potential at 10(exp -12) Torr pressure. Cryogenic fluids used to maintain a trap temperature of 4K were sized accordingly to provide twenty days of stand-alone storage time (half-life). Procurement of the superconducting magnet with associated cryostat has been completed. The inner, ultra-high vacuum system with electrode structures has been fabricated, tested and delivered to MSFC along with the magnet and cryostat. Assembly of these systems is currently in progress. Testing under high vacuum conditions, using electrons and hydrogen ions will follow in the months ahead.

Description: Scientific exploration beyond the confines of our solar system has recently become a near-term goal for NASA. Early robotic probes beyond the Sun's heliopause [a few hundred Astronomical Units (AU) from the Sun] are planned for the first decade of the 21st century. A leading propulsion system for these early interstellar efforts is the solar sail unfurled as close to the Sun as possible. This report discusses the basic physics of the solar sail, the rationale for interstellar exploration, a recent materials breakthrough influencing solar-sail design concepts, and solar sail kinematics (for the case of sail unfurlment at perihelion from an initially parabolic solar orbit and sail orientation normal to the Sun). A number of possible mission scenarios to distances up to 1,000 AU are presented as is a short discussion of what we must learn to extend our exploratory reach to 10,000 AU.

Description: Support of microgravity research on the 89th flight of the Space Transportation System (STS-89) and a continued effort to characterize the acceleration environment of the Space Shuttle Orbiter and the Mir Space Station form the basis for this report. For the STS-89 mission, the Space Shuttle Endeavour was equipped with a Space Acceleration Measurement System (SAMS) unit, which collected more than a week's worth of data. During docked operations with Mir, a second SAMS unit collected approximately a day's worth of data yielding the only set of acceleration measurements recorded simultaneously on the two spacecraft. Based on the data acquired by these SAMS units, this report serves to characterize a number of acceleration events and quantify their impact on the local nature of the accelerations experienced at the Mechanics of Granular Materials (MGM) experiment location. Crew activity was shown to nearly double the median root-mean-square (RMS) acceleration level calculated below 10 Hz, while the Enhanced Orbiter Refrigerator/Freezer operating at about 22 Hz was a strong acceleration source in the vicinity of the MGM location. The MGM science requirement that the acceleration not exceed plus or minus 1 mg was violated numerous times during their experiment runs; however, no correlation with sample instability has been found to this point. Synchronization between the SAMS data from Endeavour and from Mir was shown to be close much of the time, but caution with respect to exact timing should be exercised when comparing these data. When orbiting as a separate vehicle prior to docking, Endeavour had prominent structural modes above 3 Hz, while Mir exhibited a cluster of modes around 1 Hz. When mated, a transition to common modes was apparent in the two SAMS data sets. This report is not a comprehensive analysis of the acceleration data, so those interested in further details should contact the Principal Investigator Microgravity Services team at the National Aeronautics and Space Administration's John H. Glenn Research Center.

Description: This presentation discusses the work towards a second generation reusable launch vehicle (RLV). The goals of the second generation RLV program are reviewed. These include cost, safety, and propulsion advances. The Fluid dynamics technologies under development are discussed. These include the altitude compensating nozzle technology, the Aerospike plume induced base heating, the inducer testing technology. Pictures of altitude compensating nozzles Aerospike Plume Induced Base Heating results and Inducer testing technologies are included. Further goals of the program are to improve the methodology for optimizing design of the injectors, to improve the optimization of the turbopump and improvement of the methodology to analyze the engine performance. This presentation consists of outline view slides