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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Study on utilization of advanced composites in fuselage structures of large transports

The potential for utilizing advanced composites in fuselage structures of large transports was assessed. Six fuselage design concepts were selected and evaluated in terms of structural performance, weight, and manufacturing development and costs. Two concepts were selected that merit further consideration for composite fuselage application. These concepts are: (1) a full depth honeycomb design with no stringers, and (2) an I section stringer stiffened laminate skin design. Weight reductions due to applying composites to the fuselages of commercial and military transports were calculated. The benefits of applying composites to a fleet of military transports were determined. Significant technology issues pertinent to composite fuselage structures were identified and evaluated. Program plans for resolving the technology issues were developed.

Johnson, R. W.↗
DOE OSTI2025

Cosmological perturbation theory for large scale structure in phase space

We develop a framework for Large Scale Structure (LSS) perturbation theory, that solves the Vlasov-Poisson system of equations for the distribution function in full phase space. This approach relaxes the usual apriori assumption of negligible velocity dispersion underlying the Standard Perturbation Theory (SPT). We apply the new method to rederive the usual SPT kernels up to third order in the perturbative expansion. We also show that a counterterm, identical to the one introduced by standard Effective Field Theory (EFT) methods, naturally arises within our framework. We finish by making a precise connection to EFT techniques, which reveals the necessity of the EFTofLSS to self-consistently model the long-wavelength fluid, and illustrates the importance of having theoretical control over short distance fluctuations.

Cosmological perturbation theory in GR and beyond↗
NASA NTRS1979

Gyrodampers for large space structures

The problem of controlling the vibrations of a large space structures by the use of actively augmented damping devices distributed throughout the structure is addressed. The gyrodamper which consists of a set of single gimbal control moment gyros which are actively controlled to extract the structural vibratory energy through the local rotational deformations of the structure, is described and analyzed. Various linear and nonlinear dynamic simulations of gyrodamped beams are shown, including results on self-induced vibrations due to sensor noise and rotor imbalance. The complete nonlinear dynamic equations are included. The problem of designing and sizing a system of gyrodampers for a given structure, or extrapolating results for one gyrodamped structure to another is solved in terms of scaling laws. Novel scaling laws for gyro systems are derived, based upon fundamental physical principles, and various examples are given.

Aubrun, J. N.↗
NASA NTRS1980

The control and estimation of large space structures

A shape control or estimation problem for a large space structure can be modeled by a partial differential equation which represents changes in shape with respect to space and time, together with spatially discrete forcing functions or observations which represent the placement of actuators or sensors at discrete points along the structure. The use of Green's functions to convert boundary value problems into integral equations provides a convenient treatment of this mixture of continuous and discrete mathematics. Control and estimation algorithms are developed for the one-dimensional static beam to illustrate this technique.

Weeks, C.↗
NASA NTRS1982

Adaptive identification for the dynamics of large space structures

A new approach for identifying the dynamics of large space structures using noisy measurements is presented. In this approach, a modal system description is avoided and, hence, the a priori specification of model order. Instead, the system's order is recursively determined on-line, along with its parameters, using recursive lattice filters which are widely used in adaptive signal processing. The order determination is carried out based on statistical hypothesis testing theory. The approach is illustrated for the problem of identifying the structural dynamic characteristics of a free-free beam. Results on the effectiveness and accuracy of the identification scheme with respect to noise levels, sampling rates, and data window sizes are presented

Sundararajan, N.↗
NASA NTRS1984

Ground test experiment for large space structures, appendix I

Marshall Space Flight Center has developed a Large Space Structure (LSS) ground test verification experiment facility having adequate fidelity and flexibility to accommodate the demands of LSS control theory testing. The first experiment is in the subsystem verification and integration phase. This test employs the ASTROMAST, a lightweight S glass composite deployable beam structure, as the test article and is cited to prove out centralized and distributed sensor control strategies.

Tollison, D. K.↗
NASA NTRS1985

Active control of large space structures: An introduction and overview

An overview of the large space structure (LSS) control system design problem is presented. The LSS is defined as a class of system, and LSS modeling techniques are discussed. Model truncation, control system objectives, current control law design techniques, and particular problem areas are discussed.

Doane, G. B., III↗
NASA NTRS1985

Verification of large space structures using scale modelling laws

The feasibility of testing large space structures in 1-g environment for the purpose of verifying its performance requirement is considered. Because of the difference in test objectives as compared to the conventional structural systems, the scale modelling laws are examined. The investigation is performed on a generic structural element, a space beam. A preliminary conclusion is obtained based on the results.

Chen, J.-C.↗
NASA NTRS1986

The galaxy distribution and the large-scale structure of the universe

Data related to the large-scale galaxy distribution are discussed. The galaxy counts of Shane-Wirtanen (1967) are analyzed; the effects of residual systematic errors on the galaxy distribution measurements are considered. The analysis reveals that the Shane-Wirtanen data are not applicable to the study of large-scale structure. A model which is capable of measuring galaxy correlation functions on scales greater than about 10 Mpc is evaluated.

Geller, M. J.↗
NASA NTRS1988

The large-scale structure of flare-associated interplanetary shocks

The large-scale structure of flare-associated interplanetary shocks is investigated by examining the properties of 116 shocks which originated in solar flare events during a 18.7-year period commencing mid-May 1967. The best average representation of these shocks is an expansion which is uniform over about 100 deg. The highest compression ratio across the shock is about 15 deg west of the radial from the flare site. The loose coupling of shocks and their drivers is supported by the observation that drivers are generally only detected for shocks originating near central meridian. A comparison of the numbers of shocks per year with the numbers of sudden commencement geomagnetic storms indicates that the percentage of shocks at 1 AU which originate in flare events is less than 50 percent. Many shock-flare associations made in the past are probably in error.

Cane, H. V.↗
NASA NTRS1984

Dynamics and control of large space structures

An attempt is made to gather data useful to investigators in the fields of large space structure dynamics and control modeling, design and testing. Attention is given to structural dynamics and its relationship to such allied engineering fields as flutter analysis, as well as to problems in the prediction of atmospheric density at orbital altitude. The first challenge posed by large space structure control is the design of control systems with natural frequencies above several major structural frequencies. The establishment of a sufficiently accurate structural model, plant excitation, and shape maintenance, are noted to be additional problems.

Nurre, G. S.↗
DOE OSTI2022

Forecasting the potential of weak lensing magnification to enhance LSST large-scale structure analyses

ABSTRACT Recent works have shown that weak lensing magnification must be included in upcoming large-scale structure analyses, such as for the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), to avoid biasing the cosmological results. In this work, we investigate whether including magnification has a positive impact on the precision of the cosmological constraints, as well as being necessary to avoid bias. We forecast this using an LSST mock catalogue and a halo model to calculate the galaxy power spectra. We find that including magnification has little effect on the precision of the cosmological parameter constraints for an LSST galaxy clustering analysis, where the halo model parameters are additionally constrained by the galaxy luminosity function. In particular, we find that for the LSST gold sample (i < 25.3) including weak lensing magnification only improves the galaxy clustering constraint on Ωm by a factor of 1.03, and when using a very deep LSST mock sample (i < 26.5) by a factor of 1.3. Since magnification predominantly contributes to the clustering measurement and provides similar information to that of cosmic shear, this improvement would be reduced for a combined galaxy clustering and shear analysis. We also confirm that not modelling weak lensing magnification will catastrophically bias the cosmological results from LSST. Magnification must therefore be included in LSST large-scale structure analyses even though it does not significantly enhance the precision of the cosmological constraints.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1979

Low-thrust chemical orbit transfer propulsion

The need for large structures in high orbit is reported in terms of the many mission opportunities which require such structures. Mission and transportation options for large structures are presented, and it is shown that low-thrust propulsion is an enabling requirement for some missions and greatly enhancing to many others. Electric and low-thrust chemical propulsion are compared, and the need for an requirements of low-thrust chemical propulsion are discussed in terms of the interactions that are perceived to exist between the propulsion system and the large structure.

Pelouch, J. J., Jr.↗
NASA NTRS1979

Low-thrust chemical orbit transfer propulsion

The need for large structures in high orbit is discussed in terms of the many mission opportunities which require such structures. Mission and transportation options for large structures are presented, and it is shown that low-thrust propulsion is an enabling requirement for some missions and greatly enhancing to many others. A general comparison of electric and low-thrust chemical propulsion is made and the need for and requirements of low-thrust chemical propulsion are discussed in terms of the interactions that are perceived to exist between the propulsion system and the large structure.

Pelouch, J. J., Jr.↗
NASA NTRS1990

Computational methods and software systems for dynamics and control of large space structures

This final report on computational methods and software systems for dynamics and control of large space structures covers progress to date, projected developments in the final months of the grant, and conclusions. Pertinent reports and papers that have not appeared in scientific journals (or have not yet appeared in final form) are enclosed. The grant has supported research in two key areas of crucial importance to the computer-based simulation of large space structure. The first area involves multibody dynamics (MBD) of flexible space structures, with applications directed to deployment, construction, and maneuvering. The second area deals with advanced software systems, with emphasis on parallel processing. The latest research thrust in the second area, as reported here, involves massively parallel computers.

Park, K. C.↗
NASA NTRS1981

A towing concept for orbital transfer of large space structures

Many studies are being made to determine the most efficient method for the transfer of large space structures from low earth orbits (LEO) to higher altitudes, principally geosynchronous orbits. In this paper, towing is proposed as a possible means of orbital transfer of large space structures. A potential towing arrangement is identified and some of the systems sized for the transfer of a 2460-ft (750 meter) diameter antenna weighing approximately 154,000 lbs (70 metric tons). A savings of approximately 23 metric tons in propellants and structure resulted from the use of a towing arrangement using six towlines in parallel when compared to the use of a single tug hard mounted to the structure being towed. The towing concept appears practical and affords a means of applying loads using multiple towlines to a wide variety of structures without special adaptors.

Macconochie, I. O.↗