SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
We describe the use and appropriateness of antiorthostatic suspension in immunological investigations. This manuscript describes the model and discusses how well data obtained by using the model correlate with spaceflight data. This review concludes with some suggestions for future experiments using antiorthostatic suspension.
Results from previous studies have shown that the reduction in maximal oxygen consumption (VO2max) with simulated microgravity is attenuated in chemically sympathectomized rats. To determine the contributions of the catecholamines from the adrenal medulla in this process, investigations were conducted with 65 saline injected (SAL) and chemically sympathectomized (SX) female rats that were either surgically demedullated (DM), or intact (IN). Microgravity conditions were simulated by head-down suspension (HDS) while controls were assigned to individual cages (CC). The experimental period was 14 d. The rats were tested for VO2max, treadmill run time (RT), and submaximal mechanical efficiency (ME) prior to suspension and on days 7 and 14. Saline injected rats that had intact adrenal medullas (SAL-IN) exhibited significantly reduced measures of VO2max after 7 and 14 d by 15% and 21%, respectively. No significant reduction in VO2max was observed with HDS in the SX-IN animals. Sympathectomized rats that were demedullated (SX-DM) also exhibited a significant reduction in VO2max (12%). In addition, HDS was associated with a marked and significant reduction in RT in all groups. ME for submaximal exercise was significantly reduced after HDS in SAL-IN rats but not in the SX-IN rats. SX-DM rats experienced significant reductions in ME similar in magnitude to the SAL-IN rats. These results confirm that chemical sympathectomy attenuates the expected decrease in VO2max with HDS and suggests that circulating epinephrine contributes to this response.
The purpose of this study was to compare the effects of two different recovery modes from hind-limb suspension-induced hypodynamia on whole body and muscle (soleus) growth as well as soleus composition and size changes of different fiber types within this same muscle. Following 28 days of tail-suspension, rats were returned to their cages and sedentarily recovered (HS), or were exercised by running on a treadmill 5 days/wk, at progressively increasing workloads (HR) for one month. Sedentary and running control groups of animals (CS, CR) were also evaluated for comparative purposes. The exercise program, which was identical for CR and HR groups, had no effect on body wt., soleus wt., soleus muscle composition or fiber size in CR rats. Atrophied soleus muscle and reduced soleus wt./body wt. ratio (both 60% of control) had returned to control values by day 7 of recovery in both suspended groups despite the fact that whole body wt. gain was significantly reduced (p less than 0.05) in HR as compared to HS rats. Atrophied soleus Type I fiber mean cross-sectional area in both HR and HS groups demonstrated similar and significant (p less than 0.01) increases during recovery. Increases in Type IIa and IIc fiber area during this same period were significant only in the HR group. While the percentage area of muscle composed of Type I fibers increased in both hypodynamic groups during recovery, the reduction in area percentage of muscle made up of Type IIa fibers was again only significant in the HR group.(ABSTRACT TRUNCATED AT 250 WORDS).
The NASA Glenn Research Center at Lewis Field and Texas A&M University are developing techniques for accommodating certain types of failures in magnetic suspension systems used in rotating machinery. In recent years, magnetic bearings have become a viable alternative to rolling element bearings for many applications. For example, industrial machinery such as machine tool spindles and turbomolecular pumps can today be bought off the shelf with magnetically supported rotating components. Nova Gas Transmission Ltd. has large gas compressors in Canada that have been running flawlessly for years on magnetic bearings. To help mature this technology and quiet concerns over the reliability of magnetic bearings, NASA researchers have been investigating ways of making the bearing system tolerant to faults. Since the potential benefits from an oil-free, actively controlled bearing system are so attractive, research that is focused on assuring system reliability and safety is justifiable. With support from the Fast Quiet Engine program, Glenn's Structural Mechanics and Dynamics Branch is working to demonstrate fault-tolerant magnetic suspension systems targeted for aerospace engine applications. The Flywheel Energy Storage Program is also helping to fund this research.
Colloidal suspensions of monodisperse spheres are used as physical models of thermodynamic phase transitions and as precursors to photonic band gap materials. However, current image analysis techniques are not able to distinguish between densely packed phases within conventional microscope images, which are mainly characterized by degrees of randomness or order with similar grayscale value properties. Current techniques for identifying the phase boundaries involve manually identifying the phase transitions, which is very tedious and time consuming. We have developed an intelligent machine vision technique that automatically identifies colloidal phase boundaries. The algorithm utilizes intelligent image processing techniques that accurately identify and track phase changes vertically or horizontally for a sequence of colloidal hard sphere suspension images. This technique is readily adaptable to any imaging application where regions of interest are distinguished from the background by differing patterns of motion over time.
This publication, containing 206 entries, supersedes an earlier bibliography, NASA TM-80225 (April 1980). Citations for 18 documents have been added in this updated version. Most of the additions report results of recent studies aimed at increasing the research capabilities of magnetic suspension and balance systems, e.g., increasing force and torque capability, increasing angle of attack capability, and increasing overall system reliability. Some of the additions address the problem of scaling from the relatively small size of existing systems to much larger sizes. The purpose of this bibliography is to provide an up-to-date list of publications that might be helpful to persons interested in magnetic suspension and balance systems for use in wind tunnels. The arrangement is generally chronological by date of publication. However, papers presented at conferences or meetings are placed under dates of presentation. The numbers assigned to many of the citations have been changed from those used in the previous bibliography. This has been done in order to allow outdated citations to be removed and some recently discovered older works to be included in their proper chronological order.
A salt pill and some parts of a thermally insulating, kinematic suspension system that holds the salt pill rigidly in an adiabatic-demagnetization refrigerator (ADR) is presented. "Salt pill" in this context denotes a unit comprising a cylindrical container, a matrix of gold wires in the container, and a cylinder of ferric ammonium alum (a paramagnetic salt) that has been deposited on the wires. The structural members used in this system for both thermal insulation and positioning are aromatic polyamide fibers (Kevlar(R) or equivalent) under tension. This suspension system is designed to satisfy several special requirements to ensure the proper operation of the ADR. These requirements are to (1) maintain the salt pill at a specified position within the cylindrical bore of an electromagnet; (2) prevent vibrations, which would cause dissipation of heat in the salt pill; and (3) minimize the conduction of heat from the electromagnet bore and other neighboring objects to the salt pill; all while (4) protecting the salt pill (which is fragile) against all tensile and bending loads other than those attributable to its own weight. In addition, the system is required to consist of two subsystems -- one for the top end and one for the bottom end of the salt pill -- that can be assembled and tensioned separately from each other and from the salt pill, then later attached to the salt pill.
Advances in mirror fabrication is making very large space based telescopes possible. In the many applications, only monolithic mirrors meet the performance requirements. The existing and near-term planned heavy launch vehicles place a premium on lowest possible mass. Again, available and planned payload shroud size limits near term designs to 4 meter class mirror. Practical 8 meter and beyond designs could encourage planners to include larger shrouds if it can be proven that such mirrors can be manufactured. These two factors lower mass and larger mirrors, presents the classic optimization problem. There is a practical upper limit to how large a mirror can be supported by a purely kinematic mount system and be launched. This paper shows how the design of the suspension system and mirror blank needs to be designed simultaneously. We will also explore the concepts of auxiliary support systems, which act only during launch and disengage on orbit. We will define required characteristics of these systems and show how they can substantially reduce the mirror mass. The AMTD project is developing and maturing the processes for future replacements for HUBBLE, creating the design tools, validating the methods and techniques necessary to manufacture, test and launch extremely large optical missions. This paper will use the AMTD 4 meter "design point" as an illustration of the typical use of the modeler in generating the multiple models of mirror and suspension systems used during the conceptual design phase of most projects. The influence of Hexapod geometry, mirror depth, cell size and construction techniques (Exelsis Deep Core Low Temperature Fusion (c) versus Corning Frit Bonded (c) versus Schott Pocket Milled Zerodur (c) in this particular study) are being evaluated. Due to space and time consideration we will only be able to present snippets of the study in this paper. The advances in manufacturing techniques for lightweight mirrors, such as EXELSIS deep core low temperature fusion, Corning's continued improvements in the Frit bonding process and the ability to cast large complex designs, combined with water-jet and conventional diamond.
The MIT 6-inch magnetic suspension wind tunnel is used in two configurations to measure lift forces of two blunt bodies and produce free-to-pitch oscillations driven by capsule static stability and dynamic instabilities. Lift tests show that static aerodynamic data can be measured on a magnetically levitated model without moment control. Free-to- oscillate results show that magnetic suspension balance system (MSBS) can produce capsule dynamics suitable for extracting static and dynamic stability data.
A Kalman filter tool has been created for processing data from NASA Langley’s Magnetic Suspension and Balance System. The filter is formulated to estimate aerodynamic parameters of a model that is levitated magnetically in the test section of the wind tunnel. The Kalman filter tool is a modification of an existing code that has been in use for solving trajectory reconstruction problems and has been validated through previous use supporting many flight projects. Modifications to the code were implemented to add the capability to process data from the magnetic suspension wind tunnel. In particular, the main modifications were to the equations of motion to add models for magnetic and aerodynamic forces and moments. The code has been tested using simulation data to provide a known truth for verification.
This paper presents some of the technical aspects in the development at the Langley Research Center of an air-cove, dual-wound, single-coil, magnetic-suspension system with one-dimensional control. Overall electrical system design features and techniques are discussed in addition to the problems of control and stability. Special treatment is given to the operation of a dual-wound, high-current support coil which provides the bias fields and superimposed modulated field. Other designs features include a six-phase, solid-state power stage for modulation of the relatively large magnitude control current, and an associated six-phase trigger circuit.
Hansen suspension for millipound thrust measurement
Problems encountered in the measurement of millipound thrust, and the use of the hansen suspension system
High frequency hydrostatic pump suspension system for gimbal support for space gyros
Permanent magnet suspension over superconducting surface used as linear bearing for low level accelerometer
Automatically controlled air spring suspension system for longitudinal vibration testing of large launch vehicles
Heat transfer coefficient, friction factor, and pressure drop analyzed in flow of gas - solid dilute suspension
Magnetic suspension and balance system for use in hypersonic flow apparatus