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At least 541 records · Page 30

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NASA NTRS1987

Project CONDOR: Middle atmosphere wind structure obtained with lightweight inflatable spheres near the equatorial electrojet

Observed correlations between the atmospheric electric field and the neutral wind were studied using additional atmospheric measurements during Project CONDOR. Project CONDOR obtained measurements near the equatorial electrojet (12 S) during March 1983. Neutral atmosphere wind measurements were obtained using lightweight inflatable spheres and temperatures were obtained using a datasonde. The lightweight sphere technology, the wind structure, and temperature structure are described. Results show that the lightweight sphere gives higher vertical resolution of winds below 75 km compared with the standard sphere, but gives little or no improvement above 80 km, and no usable temperature and density data.

Schmidlin, F. J.↗

NASA NTRS1988

String-driven inflation

It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation.

Turok, Neil↗

NASA NTRS1988

Inflation in a renormalizable cosmological model and the cosmic no hair conjecture

The possibility of having inflation in a renormalizable cosmological model is investigated. The Cosmic No Hair Conjecture is proved to hold for all Bianchi types except Bianchi IX. By the use of a conformal transformation on the metric it is shown that these models are equivalent to the ones described by the Einstein-Hilbert action for gravity minimally coupled to a set of scalar fields with inflationary potentials. Henceforth, it is proven that inflationary solutions behave as attractors in solution space, making it a natural event in the evolution of such models.

Maeda, Kei-Ichi↗

NASA NTRS1989

Evidence for accurate temperatures from the inflatable falling sphere

The experiments performed with the inflatable falling sphere technique, for middle atmosphere studies, are reported. It is shown to be a potentially high accurate and independent source of temperature measurement and an intrinsic method for establishing accuracy of other atmospheric measurement techniques. Theoretical derivation, simulations, and actual measurements show that the sphere's temperature data are accurate. It is demonstrated that retrieved temperatures from falling spheres are not significantly affected by linear bias in density caused by uncertainties in sphere mass, volume, or cross sectional area. Case studies illustrate the sphere's capability to produce accurate temperatures. Comparisons with Datasonde temperature measurements obtained close in time and space are in agreement below 60 km.

Schmidlin, F. J.↗

NASA NTRS1989

A preliminary design of interior structure and foundation of an inflatable lunar habitat

A preliminary structural design and analysis of an inflatable habitat for installation on the moon was completed. The concept takes the shape of a sphere with a diameter of approximately 16 meters. The interior framing provides five floor levels and is enclosed by a spherical air-tight membrane holding an interior pressure of 14.7 psi (101.4kpa). The spherical habitat is to be erected on the lunar surface with the lower one third below grade and the upper two thirds covered with a layer of lunar regolith for thermal insulation and shielding against radiation and meteoroids. The total dead weight (earth weight) of the structural aluminum, which is of vital interest for the costly space transportation, is presented. This structural dead weight represents a preliminary estimate without including structural details. The design results in two versions: one supports the weight of the radiation shielding in case of deflation of the fabric enclosure and the other assumes that the radiation shielding is self supporting. To gain some indication of the amount of structural materials needed if the identical habitat were installed on Mars and Earth, three additional design versions were generated where the only difference is in gravity. These additional design versions are highly academic since the difference will be much more than in gravity alone. The lateral loading due to dust storms on Mars and wind loads on Earth are some examples. The designs under the lunar gravity are realistic. They may not be adequate for final material procurement and fabrication, however, as the connection details, among other reasons, may effect the sizes of the structural members.

Yin, Paul K.↗

NASA NTRS1989

The use of inflatable habitation on the moon and Mars

A recurring element in futuristic lunar and Mars base scenarios, the inflatable dome has some clear advantages over rigid modules: low mass, high volume, and good packing efficiency at launch. This paper explores some of the engineering issues involved in designing such a structure.

Roberts, Michael↗

NASA NTRS1990

False-vacuum decay in generalized extended inflation

False-vacuum decay was studied in context of generalized extended inflationary theories, and the bubble nucleation rates was computed for these theories in the limit of G(sub N) yields 0. It was found that the time dependence of the nucleation rate can be exponentially strong through the time dependence of the Jordan-Brans-Dicke field. This can have a pronounced effect on whether extended inflation can be successfully implemented.

Holman, Richard↗

NASA NTRS1990

Inflated speedups in parallel simulations via malloc()

Discrete-event simulation programs make heavy use of dynamic memory allocation in order to support simulation's very dynamic space requirements. When programming in C one is likely to use the malloc() routine. However, a parallel simulation which uses the standard Unix System V malloc() implementation may achieve an overly optimistic speedup, possibly superlinear. An alternate implementation provided on some (but not all systems) can avoid the speedup anomaly, but at the price of significantly reduced available free space. This is especially severe on most parallel architectures, which tend not to support virtual memory. It is shown how a simply implemented user-constructed interface to malloc() can both avoid artificially inflated speedups, and make efficient use of the dynamic memory space. The interface simply catches blocks on the basis of their size. The problem is demonstrated empirically, and the effectiveness of the solution is shown both empirically and analytically.

Nicol, David M.↗

NASA NTRS1991

The inflatable sphere - A technique for the accurate measurement of middle atmosphere temperatures

The present study illustrates the inflatable sphere's capability to produce accurate temperatures up to 85 km and higher, given that the necessary reduction initialization conditions are met. At heights below 60 km, comparison of sphere temperatures with in situ thermistor measurements obtained close in space and time shows good agreement. Comparison with OH-radical rotational temperatures also confirms excellent agreement at 86 km. It is concluded that the sphere technique is an independent and highly accurate source of temperature measurement, is unique in being the only low-cost source of in situ measurement of temperature throughout the mesosphere and lower thermosphere, and qualifies as an intrinsic method to establish the accuracy of other atmosphere measurement systems.

Schmidlin, F. J.↗

NASA NTRS1992

IN-STEP inflatable antenna experiment

The objectives of the NASA In-Space Technology Experiments Program (IN-STEP) are to validate the deployment of a 14-m inflatable parabolic reflector structure, measure the reflector surface accuracy, and investigate structural damping characteristics under operational conditions. Here, the accomplishment to date and the approach planned for the remainder of the experiment are discussed. In particular, attention is given to the experiment subsystems, the mechanical thermal, and structural characteristics of the reflector, and the ground-based test program.

Freeland, R. E.↗

NASA NTRS1993

Inflatable Habitat Structure

Report describes proposed inflatable habitat structure used during exploration of Moon or Mars. Provides living and working space for 12 crewmembers and includes horizontal cylindrical skin 8 m in diameter and 45 m long. Skin encloses floors and arch frame, supported by exostructure on foundations.

Kennedy, Kriss J.↗

NASA NTRS1992

Cosmic microwave background probes models of inflation

Inflation creates both scalar (density) and tensor (gravity wave) metric perturbations. We find that the tensor-mode contribution to the cosmic microwave background anisotropy on large-angular scales can only exceed that of the scalar mode in models where the spectrum of perturbations deviates significantly from scale invariance. If the tensor mode dominates at large-angular scales, then the value of DeltaT/T predicted on 1 deg is less than if the scalar mode dominates, and, for cold-dark-matter models, bias factors greater than 1 can be made consistent with Cosmic Background Explorer (COBE) DMR results.

Davis, Richard L.↗

NASA NTRS1992

Latest COBE results, large-scale data, and predictions of inflation

One of the predictions of the inflationary scenario of cosmology is that the initial spectrum of primordial density fluctuations (PDFs) must have the Harrison-Zeldovich (HZ) form. Here, in order to test the inflationary scenario, predictions of the microwave background radiation (MBR) anisotropies measured by COBE are computed based on large-scale data for the universe and assuming Omega-1 and the HZ spectrum on large scales. It is found that the minimal scale where the spectrum can first enter the HZ regime is found, constraining the power spectrum of the mass distribution to within the bias factor b. This factor is determined and used to predict parameters of the MBR anisotropy field. For the spectrum of PDFs that reaches the HZ regime immediately after the scale accessible to the APM catalog, the numbers on MBR anisotropies are consistent with the COBE detections and thus the standard inflation can indeed be considered a viable theory for the origin of the large-scale structure in the universe.

Kashlinsky, A.↗

NASA NTRS1991

Stochastic inflation lattice simulations - Ultra-large scale structure of the universe

Non-Gaussian fluctuations for structure formation may arise in inflation from the nonlinear interaction of long wavelength gravitational and scalar fields. Long wavelength fields have spatial gradients, a (exp -1), small compared to the Hubble radius, and they are described in terms of classical random fields that are fed by short wavelength quantum noise. Lattice Langevin calculations are given for a toy model with a scalar field interacting with an exponential potential where one can obtain exact analytic solutions of the Fokker-Planck equation. For single scalar field models that are consistent with current microwave background fluctuations, the fluctuations are Gaussian. However, for scales much larger than our observable Universe, one expects large metric fluctuations that are non-Gaussian. This example illuminates non-Gaussian models involving multiple scalar fields which are consistent with current microwave background limits.

Salopek, D. S.↗

NASA NTRS1938

The drag of inflatable rubber de-icers

Force tests on rubber de-icer models of several different profiles, at approximately one-third full scale, been carried out in the NACA 8-foot high speed wind tunnel. The conventional de-icer installation, deflated, added about 15 percent to the smooth-wing drag and, inflated, added about 100 percent. An improved installation with flash attaching strips added about 10 percent, deflated. The bulging, or ballooning, of de-icers from the wing surface is described and some remedies are discussed.

Robinson, Russell G↗

NASA NTRS1994

Cosmic background radiation anisotropy in an open inflation, cold dark matter cosmogony

We compute the cosmic background radiation anisotropy, produced by energy-density fluctuations generated during an early epoch of inflation, in an open cosmological model based on the cold dark matter scenario. At Omega(sub 0) is approximately 0.3-0.4, the Cosmic Background Explorer (COBE) normalized open model appears to be consistent with most observations.

Kamionkowski, Marc↗

NASA NTRS1995

COBE DMR-normalized open inflation cold dark matter cosmogony

A cut-sky orthogonal mode analysis of the 2 year COBE DMR 53 and 90 GHz sky maps (in Galactic coordinates) is used to determine the normalization of an open inflation model based on the cold dark matter (CDM) scenario. The normalized model is compared to measures of large-scale structure in the universe. Although the DMR data alone does not provide sufficient discriminative power to prefer a particular value of the mass density parameter, the open model appears to be reasonably consistent with observations when Omega(sub 0) is approximately 0.3-0.4 and merits further study.

Gorski, Krzysztof M.↗

NASA NTRS1995

Inflatable Reflector For Solar Power And Radio Communication

Report proposes installation of lightweight inflatable reflector structure aboard spacecraft required to both derive power from sunlight and communicate with Earth by radio when apparent position of Earth is at manageably small angle from line of sight to Sun. Structure contains large-aperture paraboloidal reflector aimed toward Sun and concentrates sunlight onto photovoltaic power converter and acts as main reflector of spacecraft radio-communication system.

Sercel, Joel↗