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NASA NTRS1989

Advantages of a round-body shuttle

A cylindrical fuselage cross-section SSTOV representing the design generation beyond the current NASA Space Shuttle has been projected capable of reducing the cost of payload delivery to orbit while increasing mission scope. Due to its intrinsically greater wetted-area and structural weight efficiencies, this cylindrical vehicle would carry 40 percent greater payload than the Space Shuttle system despite a 20-percent lower gross liftoff weight. A LOX/hydrocarbon fuel combination would be employed during the early portion of flight, thereupon shifting to LOX/hydrogen. The cylindrical SSTOV would have eight times the volume of the Space Shuttle Orbiter.

Arrington, James P.↗

NASA NTRS1983

Nucleon and deuteron scattering cross sections from 25 MV/Nucleon to 22.5 GeV/Nucleon

Within the context of a double-folding optical potential approximation to the exact nucleus-nucleus multiple-scattering series, eikonal scattering theory is used to generate tables of nucleon and deuteron total and absorption cross sections at kinetic energies between 25 MeV/nucleon and 22.5 GeV/nucleon for use in cosmic-ray transport and shielding studies. Comparisons of predictions for nucleon-nucleus and deuteron-nucleus absorption and total cross sections with experimental data are also made.

Townsend, L. W.↗

NASA NTRS1989

HOMAR: A computer code for generating homotopic grids using algebraic relations: User's manual

A computer code for fast automatic generation of quasi-three-dimensional grid systems for aerospace configurations is described. The code employs a homotopic method to algebraically generate two-dimensional grids in cross-sectional planes, which are stacked to produce a three-dimensional grid system. Implementation of the algebraic equivalents of the homotopic relations for generating body geometries and grids are explained. Procedures for controlling grid orthogonality and distortion are described. Test cases with description and specification of inputs are presented in detail. The FORTRAN computer program and notes on implementation and use are included.

Moitra, Anutosh↗

NASA NTRS2016

Average Cross-Sectional Area of DebriSat Fragments Using Volumetrically Constructed 3D Representations

Debris fragments from the hypervelocity impact testing of DebriSat are being collected and characterized for use in updating existing satellite breakup models. One of the key parameters utilized in these models is the ballistic coefficient of the fragment which is directly related to its area‐to‐mass ratio. However, since the attitude of fragments varies during their orbital lifetime, it is customary to use the average cross‐sectional area in the calculation of the area‐to‐mass ratio. The average cross‐sectional area is defined as the average of the projected surface areas perpendicular to the direction of motion and has been shown to be equal to one‐fourth of the total surface area of a convex object. Unfortunately, numerous fragments obtained from the DebriSat experiment show significant concavity (i.e., shadowing) and thus we have explored alternate methods for computing the average cross‐sectional area of the fragments. An imaging system based on the volumetric reconstruction of a 3D object from multiple 2D photographs of the object was developed for use in determining the size characteristic (i.e., characteristics length) of the DebriSat fragments. For each fragment, the imaging system generates N number of images from varied azimuth and elevation angles and processes them using a space‐carving algorithm to construct a 3D point cloud of the fragment. This paper describes two approaches for calculating the average cross‐sectional area of debris fragments based on the 3D imager. Approach A utilizes the constructed 3D object to generate equally distributed cross‐sectional area projections and then averages them to determine the average cross‐sectional area. Approach B utilizes a weighted average of the area of the 2D photographs to directly compute the average cross‐sectional area. A comparison of the accuracy and computational needs of each approach is described as well as preliminary results of an analysis to determine the "optimal" number of images needed for the 3D imager to accurately measure the average cross sectional area of objects with known dimensions.

Scruggs, T.↗

NASA NTRS1981

Study of high speed complex number algorithms

A method of evaluating the radiation integral on the curved surface of a reflecting antenna is presented. A three dimensional Fourier transform approach is used to generate a two dimensional radiation cross-section along a planer cut at any angle phi through the far field pattern. Salient to the method is an algorithm for evaluating a subset of the total three dimensional discrete Fourier transform results. The subset elements are selectively evaluated to yield data along a geometric plane of constant. The algorithm is extremely efficient so that computation of the induced surface currents via the physical optics approximation dominates the computer time required to compute a radiation pattern. Application to paraboloid reflectors with off-focus feeds in presented, but the method is easily extended to offset antenna systems and reflectors of arbitrary shapes. Numerical results were computed for both gain and phase and are compared with other published work.

Heisler, R.↗

NASA NTRS1984

QUICK Interactive Graphics Analysis

Cross-section and body-line plots generated for error detection and analysis. FORTRAN 77 version of QUICK Interactive Graphics Analysis program QUIAGA, performs same operations as FORTRAN IV counterpart. QUIAGA displays aircraft QUICK geometry data to aid in detection and analysis of errors. QUICK-geometry data used to generate completelyanalytical aircraft geometry description for finite difference flow codes. QUIAGA program written in FORTRAN 77.

Townsend, J. C.↗

NASA NTRS1987

Design Improvement for Airplane-Engine Nacelles

Advanced three-dimensional transonic design routine for wingmounted engine nacelles modified to include effects of propellers and wing sweep. Resulting new nacelle shapes introduce less airflow disturbance and less drag. Improvement consists of introduction of boundary conditions in form of nonuniform onset flow in area of wing washed by propeller slipstream. Routine generates nacelle shape as series of cross sections swept, relatively to unperturbed flow, as function of wing shape.

Vernon, D. F.↗

NASA NTRS1986

Gross-merchantable timber volume estimation using an airborne lidar system

A preliminary study to determine the utility of an airborne laser as a tool for use by forest managers to estimate gross-merchantable timber volume was conducted near the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center, Wallops Flight Facility utilizing the NASA Airborne Oceanographic Lidar (AOL) system. Measured timber volume was regressed against the cross-sectional area of an AOL-generated profile of forest at the same location. The AOL profile area was found to be a very significant variable in the estimation of gross-merchantable timber volume. Significant improvements were obtained when the data were stratified by species. The overall R-squared value obtained was 0.921 with the regression significant at the one percent level.

Maclean, G. A.↗

NASA NTRS1988

Rainfall on microwave return from the sea surface

The long range goal remains unchanged; to conduct experiments and develop/test theoretical models to permit useful algorithms to be constructed for microwave systems that observe oceanic processes. This topic is relevant to altimeters, scatterometers, and rain rate measurements. The current focus is attention to scatterometer wind velocity measurement. One component of the laboratory efforts is an experiment conducted, in the wind wave tank at the GSFC/WFF, to quantify the effect of rain-generated surface wave brightening of radar cross section. Laboratory conditions can be characterized as light wind, functional rain rates, a single drop size, and a 36 GHz radar system at 30 degrees inclination.

Bliven, L. F.↗

NASA NTRS1991

Method and apparatus for sensor fusion

Method and apparatus for fusion of data from optical and radar sensors by error minimization procedure is presented. The method was applied to the problem of shape reconstruction of an unknown surface at a distance. The method involves deriving an incomplete surface model from an optical sensor. The unknown characteristics of the surface are represented by some parameter. The correct value of the parameter is computed by iteratively generating theoretical predictions of the radar cross sections (RCS) of the surface, comparing the predicted and the observed values for the RCS, and improving the surface model from results of the comparison. Theoretical RCS may be computed from the surface model in several ways. One RCS prediction technique is the method of moments. The method of moments can be applied to an unknown surface only if some shape information is available from an independent source. The optical image provides the independent information.

Krishen, Kumar↗

NASA NTRS2015

Nanowire Photovoltaic Devices

Firefly Technologies, in collaboration with the Rochester Institute of Technology and the University of Wisconsin-Madison, developed synthesis methods for highly strained nanowires. Two synthesis routes resulted in successful nanowire epitaxy: direct nucleation and growth on the substrate and a novel selective-epitaxy route based on nanolithography using diblock copolymers. The indium-arsenide (InAs) nanowires are implemented in situ within the epitaxy environment-a significant innovation relative to conventional semiconductor nanowire generation using ex situ gold nanoparticles. The introduction of these nanoscale features may enable an intermediate band solar cell while simultaneously increasing the effective absorption volume that can otherwise limit short-circuit current generated by thin quantized layers. The use of nanowires for photovoltaics decouples the absorption process from the current extraction process by virtue of the high aspect ratio. While no functional solar cells resulted from this effort, considerable fundamental understanding of the nanowire epitaxy kinetics and nanopatterning process was developed. This approach could, in principle, be an enabling technology for heterointegration of dissimilar materials. The technology also is applicable to virtual substrates. Incorporating nanowires onto a recrystallized germanium/metal foil substrate would potentially solve the problem of grain boundary shunting of generated carriers by restricting the cross-sectional area of the nanowire (tens of nanometers in diameter) to sizes smaller than the recrystallized grains (0.5 to 1 micron(exp 2).

Forbes, David↗

NASA NTRS2016

IN31A-1734 Development and Evaluation of a Gridded CrIS/ATMS Visualization for Operational Forecasting

A collaborative effort between SPoRT, CIMSS, CIRA, GINA, and NOAA has produced a unique gridded visualization of real-time CrIS/ATMS sounding products. This product uses the NUCAPS retrieval algorithm and polar2grid software to generate plan-view and cross-section visualization for forecast challenges associated with cold air aloft and convective potential. Forecasters at select partner offices have been able to view the Gridded NUCAPS products in AWIPS alongside other operational data products with generally favorable feedback.

aviation↗

NASA NTRS1985

Tables of nuclear cross sections for galactic cosmic rays: Absorption cross sections

A simple but comprehensive theory of nuclear reactions is presented. Extensive tables of nucleon, deuteron, and heavy-ion absorption cross sections over a broad range of energies are generated for use in cosmic ray shielding studies. Numerous comparisons of the calculated values with available experimental data show agreement to within 3 percent for energies above 80 MeV/nucleon and within approximately 10 percent for energies as low as 30 MeV/nucleon. These tables represent the culmination of the development of the absorption cross section formalism and supersede the preliminary absorption cross sections published previously in NASA TN D-8107, NASA TP-2138, and NASA TM-84636.

Townsend, L. W.↗

NASA NTRS1997

High Resolution UV Emission Cross Section for Analysis of Satellite Observations of Aurora and Dayglow of Planetary Atmosphere

A new generation of high resolution UV imaging spacecraft (Polar, Galileo, HST) are studying the airglow and aurora of the Earth and the Jovian planets. To keep pace with these technological improvements we have developed a laboratory program to provide electron collision cross sections of the major molecular planetary gases (H (sub 2) , H, O, N (sub 2) , CO (sub 2) , SO (sub 2) , O (sub 2) , H (sub 2) O, and CO).

Polar Galileo airglow aurora Earth Jovian planets.↗

NASA NTRS1992

Cross-sections for electron impact ionization of O2

Using a crossed electron beam-molecular beam collision geometry and the relative flow technique measurements have been made to generate a uniform set of electron impact ionization cross-section data for O2 for electron impact energies from threshold to 1000 eV. Present values of total, partial and dissociative ionization cross-sections are compared with previously published data. Cross-sections for the formation of O2(+) from O2 have been measured for the first time.

Krishnakumar, E.↗

NASA NTRS1974

Surface fitting three-dimensional bodies

The geometry of general three-dimensional bodies is generated from coordinates of points in several cross sections. Since these points may not be smooth, they are divided into segments and general conic sections are curve fit in a least-squares sense to each segment of a cross section. The conic sections are then blended in the longitudinal direction by fitting parametric cubic-spline curves through coordinate points which define the conic sections in the cross-sectional planes. Both the cross-sectional and longitudinal curves may be modified by specifying particular segments as straight lines and slopes at selected points. Slopes may be continuous or discontinuous and finite or infinite. After a satisfactory surface fit has been obtained, cards may be punched with the data necessary to form a geometry subroutine package for use in other computer programs. At any position on the body, coordinates, slopes and second partial derivatives are calculated. The method is applied to a blunted 70 deg delta wing, and it was found to generate the geometry very well.

Dejarnette, F. R.↗

NASA NTRS2003

Laboratory Studies in UV and EUV Solar Physics

The Ion Beam Experiment at the Center for Astrophysics is dedicated to the study of ion-electron collision processes of importance in solar physics. A paper describing our most recent measurement 'Absolute cross section for Si(2+)(3s3p(sup 3)Rho (sup 0) yields 3s3p(sup 1)Rho(sup 0)) electron-impact excitation' was published during the past year. Dr. Paul Janzen received his PhD. from the Harvard Physics Department on the basis of this and other work, such as the new electron cyclotron resonance (ECR) ion source. The ion source is producing stable beams with large currents for our present work on C(2+), and it also produces stable beams with large currents of more highly charged systems, for future work on systems such as O(4+). The past year has been focussed on our current program to measure absolute cross sections for Electron Impact Excitation (EIE) in C(2+), one of the primary ions used for probing the solar transition region. C(2+) beams produced by the ion source have been transported to the interaction region of the experiment, where the collisions are studied, and Visiting Scientist Dr. Adrian Daw is currently collecting data to measure the C(2+)(2s2p(sup 3)Rho(sup 0) yields 2p(sup 2)(sup 3)Rho) EIE cross section as a function of collision energy, under the guidance of Drs. John Kohl, Larry Gardner and Bill Parkinson. Also this year, modifications were made to the ECR ion source in order to produce greater currents of highly charged ions. Testing of the ion source was completed. Modifications were designed to extend the photon detection capabilities of the apparatus to shorter UV wavelengths, or EUV. Following the work on C(2+)(2s2p(sup 3)Pho(sup 0) yields 2p(sup 2)(sup 3)Rho), the extended UV detection capabilities will be used to measure the C(2+)(2s(sup 2)(sup 1)S yields 2s2p(sup 1)Rho(sup 0)) EIE cross section. The EUV modifications complement those of the new ion source, by enabling detection of EUV light generated by high charge state ions and putting us in a position to measure the excitation cross sections for more highly charged ions as well.

Parkinson, William↗

NASA NTRS1984

Vortex-generating coolant-flow-passage design for increased film-cooling effectiveness and surface coverage

The thermal film-cooling footprints observed by infrared imagery for three coolant-passage configurations embedded in adiabatic-test plates are discussed. The configurations included a standard round-hole cross section and two orientations of a vortex-generating flow passage. Both orientations showed up to factors of four increases in both film-cooling effectiveness and surface coverage over that obtained with the round coolant passage. The crossflow data covered a range of tunnel velocities from 15.5 to 45 m/sec with blowing rates from 0.20 to 2.05. A photographic streakline flow visualization technique supported the concept of the counterrotating apability of the flow passage design and gave visual credence to its role in inhibiting flow separation.

Papell, S. S.↗