The effects of target and missile characteristics on theoretical minimum miss distance for a beam-rider guidance system in the presence of noise
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Stewart, Elwood C↗
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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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The Minimum Induced Drag of Aerofoils
This report helps explain the phenomenon of flight. It contains some theorems concerning the arrangement of airplane wings which are of considerable practical interest. In particular, it shows the theoretical reasons for the decrease of drag which accompanies all increase in the aspect ratio or lateral extension of a wing. The efficiency of a given arrangement of wings may be calculated from the formulae derived in this paper.
Munk, Max M↗
Charts for the minimum-weight design of 24s-t aluminum-alloy flat compression panels with longitudinal z-section stiffeners
Design charts are developed for 24s-t aluminum-alloy flat compression panels with longitudinal z-section stiffeners. These charts make possible the design of the lightest panels of this type for a wide range of design requirements. Examples of the use of the charts are given and it is pointed out on the basis of these examples that, over a wide range of design conditions, the maintenance of buckle-free surfaces does not conflict with the achievement of high structural efficiency. The achievement of the maximum possible structural efficiency with 24s-t aluminum-alloy panels, however, requires closer stiffener spacings than those now in common use.
Schuette, Evan H↗
Axially symmetric shapes with minimum wave drag
The external wave drag of bodies of revolution moving at supersonic speeds can be expressed either in terms of the geometry of the body, or in terms of the body-simulating axial source distribution. For purposes of deriving optimum bodies under various given conditions, it is found that the second of the methods mentioned is the more tractable. By use of a quasi-cylindrical theory, that is, the boundary conditions are applied on the surface of a cylinder rather than on the body itself, the variational problems of the optimum bodies having prescribed volume or caliber are solved. The streamline variations of cross-sectional area and drags of the bodies are exhibited, and some numerical results are given.
Heaslet, Max A↗
Charts for the minimum-weight design of 24S-T aluminum-alloy flat compression panels with longitudinal Z-section stiffeners
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ALUMINUM ALLOYS - ALCOA 24ST - COMPRESSION↗
Intercooler cooling-air weight flow and pressure drop for minimum drag loss
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ENGINES-COOLING↗
Method of Estimating the Minimum Size of a Tail or Wing-tip Parachute for Emergency Spin Recovery of an Airplane
Paper presents a method for estimating the size of a tail or wing-tip parachute required for satisfactory emergency recovery of airplanes during spin demonstrations.
Malvestuto, Frank S , Jr↗
Minimum accommodation for aerobrake assembly. Phase 2: Structural concepts for a lunar transfer vehicle aerobrake which can be assembled on orbit
A multidisciplinary conceptual study was conducted to define a reusable lunar transfer vehicle (LTV) aerobrake which could be launched on a Space Shuttle of Titan 4 and assembled on orbit at Space Station Freedom. A major objective was to design an aerobrake, with integrated structure and thermal protection systems, which has a mass less than 20 percent (9040 lb) of the LTV lunar return mass. The aerobrake segmentation concepts, the structural concepts, a joint concept for assembly, and a structural design with analysis of the aerobrake are described. Results show that a 50-foot diameter LTV aerobrake can be designed for on-orbit assembly which will achieve the 20 percent mass budget.
Dorsey, John T.↗
Minimum accommodation for aerobrake assembly, phase 2
A multi-element study was done to assess the practicality of a Space Station Freedom-based aerobrake system for the Space Exploration Initiative. The study was organized into six parts related to structure, aerodynamics, robotics and assembly, thermal protection system, inspection, and verification, all tied together by an integration study. The integration activity managed the broad issues related to meeting mission requirements. This report is a summary of the issues addressed by the integration team.
Katzberg, Stephen J.↗
A PC program to optimize system configuration for desired reliability at minimum cost
High reliability is desired in all engineered systems. One way to improve system reliability is to use redundant components. When redundant components are used, the problem becomes one of allocating them to achieve the best reliability without exceeding other design constraints such as cost, weight, or volume. Systems with few components can be optimized by simply examining every possible combination but the number of combinations for most systems is prohibitive. A computerized iteration of the process is possible but anything short of a super computer requires too much time to be practical. Many researchers have derived mathematical formulations for calculating the optimum configuration directly. However, most of the derivations are based on continuous functions whereas the real system is composed of discrete entities. Therefore, these techniques are approximations of the true optimum solution. This paper describes a computer program that will determine the optimum configuration of a system of multiple redundancy of both standard and optional components. The algorithm is a pair-wise comparative progression technique which can derive the true optimum by calculating only a small fraction of the total number of combinations. A designer can quickly analyze a system with this program on a personal computer.
Hills, Steven W.↗
Optimal realizable filters and the minimum Euclidean distance principle
Minimizing a Euclidean distance in the complex plane optimizes a wide class of correlation metrics for filters implemented on realistic devices. The algorithm searches over no more than two real scalars (gain and phase). It unifies a variety of previous solutions for special cases (e.g., a maximum signal-to-noise ratio with colored noise and a real filter and a maximum correlation intensity with no noise and a coupled filter). It extends optimal partial information filter theory to arbitrary spatial light modulators (fully complex, coupled, discrete, finite contrast ratio, and so forth), additive input noise (white or colored), spatially nonuniform filter modulators, and additive correlation detection noise (including signal dependent noise).
Juday, Richard D.↗
Minimum-exposure near-terrain flight trajectories for rotorcraft
The paper presents methodologies for constructing optimal trajectories for rotorcraft executing nap-of-the-earth flight over known terrain. Unlike the standard techniques, the present approaches require only a one-dimensional numerical search for determining optimal trajectories. Numerical algorithms are developed using two kinematic vehicle models in conjunction with optimal control theory.
Menon, P. K. A.↗
On the minimum fluxes of low-energy ions (0.5 MeV/NUC - 8 MeV/NUC) at high heliospheric latitudes
The quiet-time fluxes of ions from 0.5 MeV/nuc to 7 MeV/nuc (for oxygen) have been studied for the time period between mid-1993 through the first 104 days of 1994. During this time period, Ulysses was below the heliographic current sheet. We find that at the quietest times, the ion population is dominated by the anomalous cosmic ray (ACR) component. For more active times, but still avoiding the most active time periods, the population below 3 MeV/nuc contains a CIR component as well as ACR ions.
Blake, J. B.↗
What determines the direction of minimum variance of the magnetic field fluctuations in the solar wind?
The solar wind is not an isotropic medium; two symmetry axis are provided, first the radial direction (because the mean wind is radial) and second the spiral direction of the mean magnetic field, which depends on heliocentric distance. Observations show very different anisotropy directions, depending on the frequency waveband; while the large-scale velocity fluctuations are essentially radial, the smaller scale magnetic field fluctuations are mostly perpendicular to the mean field direction, which is not the expected linear (WkB) result. We attempt to explain how these properties are related, with the help of numerical simulations.
Grappin, R.↗
Design of a Minimum Surface-Effect Tendon-Based Microactuator for Micromanipulation
A piezoelectric (PZT) stack-based actuator was developed to provide a means of actuation with dynamic characteristics appropriate for small-scale manipulation. In particular, the design incorporates a highly nonlinear, large-ratio transmission that provides approximately two orders of magnitude motion amplification from the PZT stack. In addition to motion amplification, the nonlinear transmission was designed via optimization methods to distort the highly non-uniform properties of a piezoelectric actuator so that the achievable actuation force is nearly constant throughout the actuator workspace. The package also includes sensors that independently measure actuator output force and displacement, so that a manipulator structure need not incorporate sensors nor the associated wires. Specifically, the actuator was designed to output a maximum force of at least one Newton through a stroke of at least one millimeter. For purposes of small-scale precision position and/or force control, the actuator/sensor package was designed to eliminate stick-slip friction and backlash. The overall dimensions of the actuator/sensor package are approximately 40 x 65 x 25 mm.
Goldfarb, Michael↗
The Achievement of Near-Theoretical-Minimum Contact Resistance to InP
We have investigated the electrical and metallurgical behavior of the InP/Au/Ni contact system. We show that when a layer of Au, 100 A or more in thickness, is introduced between n-InP and Ni contact metallization, specific contact resistivity R, values in the low 10(exp -8) Omega cm(exp 2) range are achieved after sintering. It is suggested that these ultralow values of R(sub c) are due to the presence, at the metal-InP interface, of a Ni3P layer combined with a stoichiometry change in the InP surface. We show, in addition, that it is possible to achieve very low R(sub c) values with this system without incurring device destroying sinter-induced metallurgical interdiffusion.
Fatemi, Navid S.↗
Characterization of the Minimum Energy Paths for the Ring Closure Reactions of C4H3 with Acetylene
The ring closure reaction of C4H3 with acetylene to give phenyl radical is one proposed mechanism for the formation of the first aromatic ring in hydrocarbon combustion. There are two low-lying isomers of C4H3; 1-dehydro-buta-l-ene-3-yne (n-C4H3) and 2-dehydro-buta-l-ene-3-yne (iso-C4H3). It has been proposed that only n-C4H3 reacts with acetylene to give phenyl radical, and since iso-C4H3 is more stable than n-C4H3, formation of phenyl radical by this mechanism is unlikely. We report restricted Hartree-Fock (RHF) plus singles and doubles configuration interaction calculations with a Davidson's correction (RHF+1+2+Q) using the Dunning correlation consistent polarized valence double zeta basis set (cc-pVDZ) for stationary point structures along the reaction pathway for the reactions of n-C4H3 and iso-C4H3 with acetylene. n-C4H3 plus acetylene (9.4) has a small entrance channel barrier (17.7) (all energetics in parentheses are in kcal/mol with respect to iso-C4H3 plus acetylene) and the subsequent closure steps leading to phenyl radical (-91.9) are downhill with respect to the entrance channel barrier. Iso-C4H3 Plus acetylene also has an entrance channel barrier (14.9) and there is a downhill pathway to 1-dehydro-fulvene (-55.0). 1-dehydro-fulvene can rearrange to 6-dehydro-fulvene (-60.3) by a 1,3-hydrogen shift over a barrier (4.0), which is still below the entrance channel barrier, from which rearrangement to phenyl radical can occur by a downhill pathway. Thus, both n-C4H3 and iso-C4H3 can react with acetylene to give phenyl radical with small barriers.
Walch, Stephen P.↗
Flight Performance of a Transonic Turbine-Driven Propeller Designed for Minimum Noise
Results are presented of a flight investigation to determine the aerodynamic characteristics of a transonic-type propeller. This propeller was designed for an advance ratio of 4.0 at a forward Mach number of 0.82 in an effort to limit the noise production. The measured efficiency of the propeller was 68 percent at the design Mach number of 0.82. This value compares with an efficiency as much as 15 percent higher with the same Mach number for a propeller designed for an optimum advance ratio of about 3.0. This penalty in efficiency must be considered in light of the resulting noise reduction. The noise under static and take-off conditions was measured to be 117.5 decibels, which represents a noise reduction of about 5 decibels (at 1,400 horsepower) compared with the advance-ratio-3 -design.
OBryan, Thomas C.↗