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Results for “stabilization method”

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.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

End-to-End System Test of the Relative Precision and Stability of the Photometric Method for Detecting Earth-Size Extrasolar Planets

We developed the CCD camera system for the laboratory test demonstration and designed the optical system for this test. The camera system was delivered to Ames in April, 1999 with continuing support mostly in the software area as the test progressed. The camera system has been operating successfully since delivery. The optical system performed well during the test. The laboratory demonstration activity is now nearly complete and is considered to be successful by the Technical Advisory Group, which met on 8 February, 2000 at the SETI Institute. A final report for the Technical Advisory Group and NASA Headquarters will be produced in the next few months. This report will be a comprehensive report on all facets of the test including those covered under this grant. A copy will be forwarded, if desired, when it is complete.

Dunham, Edward W.↗
NASA NTRS1996

New Method Developed for Aeroelastic Stability Analysis

The development of advanced-design ultrahigh bypass ratio engines has led to renewed interest in the study of the flutter of bladed disks. Previously, two fundamental approaches were used in flutter calculations: frequency domain analysis and time-domain analysis. With the development of time-marching computational fluid dynamics (CFD) flow solvers, both approaches have been used with equal ease. In the present work at the NASA Lewis Research Center, substantial computational savings have been achieved by applying a numerical eigensolver to a nonlinear, time-marching fluid-structure interaction system solver for flutter prediction.

Source record↗
NASA NTRSDate not supplied

Passive Stabilization of Rotating Tethered Spacecraft

Rotating Spacecrafts can provide artificial gravity for long-term space missions, but the design of a Guidance and Control scheme for these vehicles is nuanced. For a three-segment vehicle with the propulsion element located at the center of mass, the vehicle must stabilize itself about this point even in the event of various off-nominal circumstances. Thus, a robust and passive spin stabilization system is needed. In this paper, various methods for stabilizing the system to allow for the exchange of mass and air between elements are explored and simulated.

Dynamics↗
NASA NTRS1989

Beat to beat variability in cardiovascular variables: noise or music?

Cardiovascular variables such as heart rate, arterial blood pressure, stroke volume and the shape of electrocardiographic complexes all fluctuate on a beat to beat basis. These fluctuations have traditionally been ignored or, at best, treated as noise to be averaged out. The variability in cardiovascular signals reflects the homeodynamic interplay between perturbations to cardiovascular function and the dynamic response of the cardiovascular regulatory systems. Modern signal processing techniques provide a means of analyzing beat to beat fluctuations in cardiovascular signals, so as to permit a quantitative, noninvasive or minimally invasive method of assessing closed loop hemodynamic regulation and cardiac electrical stability. This method promises to provide a new approach to the clinical diagnosis and management of alterations in cardiovascular regulation and stability.

Non-NASA Center↗
NASA NTRS2003

The Langley Stability and Transition Analysis Code (LASTRAC) : LST, Linear and Nonlinear PSE for 2-D, Axisymmetric, and Infinite Swept Wing Boundary Layers

During the past two decades, our understanding of laminar-turbulent transition flow physics has advanced significantly owing to, in a large part, the NASA program support such as the National Aerospace Plane (NASP), High-speed Civil Transport (HSCT), and Advanced Subsonic Technology (AST). Experimental, theoretical, as well as computational efforts on various issues such as receptivity and linear and nonlinear evolution of instability waves take part in broadening our knowledge base for this intricate flow phenomenon. Despite all these advances, transition prediction remains a nontrivial task for engineers due to the lack of a widely available, robust, and efficient prediction tool. The design and development of the LASTRAC code is aimed at providing one such engineering tool that is easy to use and yet capable of dealing with a broad range of transition related issues. LASTRAC was written from scratch based on the state-of-the-art numerical methods for stability analysis and modem software technologies. At low fidelity, it allows users to perform linear stability analysis and N-factor transition correlation for a broad range of flow regimes and configurations by using either the linear stability theory (LST) or linear parabolized stability equations (LPSE) method. At high fidelity, users may use nonlinear PSE to track finite-amplitude disturbances until the skin friction rise. Coupled with the built-in receptivity model that is currently under development, the nonlinear PSE method offers a synergistic approach to predict transition onset for a given disturbance environment based on first principles. This paper describes the governing equations, numerical methods, code development, and case studies for the current release of LASTRAC. Practical applications of LASTRAC are demonstrated for linear stability calculations, N-factor transition correlation, non-linear breakdown simulations, and controls of stationary crossflow instability in supersonic swept wing boundary layers.

Chang, Chau-Lyan↗
NASA NTRS1982

Modal control of relaxed static stability aircraft

A method is developed that assigns a selected portion of a closed loop system eigenstructure in accordance with certain desirable criteria. The method is applied here to a relaxed static stability aircraft, the goal being to synthesize a control law that provides the unstable aircraft with handling qualities equal to or better than those of a comparable statically stable aircraft. It is shown that by using the target system eigenstructure, good flight characteristics are achieved by the unstable aircraft. It is also shown that improved characteristics can be obtained by assigning an orthogonal eigenvector structure.

Rooney, R. H.↗
NASA NTRS1938

Generalized analysis of experimental observations in problems of elastic stability

A generalized method of analyzing experimental observations in problems of elastic stability is presented in which the initial readings of load and deflection may be taken at any load less the critical load. The analysis is an extension of a method published by Southwell in 1932, in which it was assumed that the initial readings are taken at zero load.

Lundquist, Eugene E↗
NASA NTRS1974

Method and apparatus for checking the stability of a setup for making reflection type holograms

A method and apparatus are described for checking the stability of a setup for recording reflection-type (white light) holograms. Two sets of interference fringes are simultaneously obtained, one giving information about coherence and stability of the setup alone and the other demonstrating coherence of the entire system, including the holographic recording plate. Special emphasis is given to the stability of the plate, due to the fact that any minute vibration might severely degrade or completely destroy the recording.

Lackner, H. G.↗