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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Analysis of operator participation

The problem of providing a psychological conception of the analysis of operator participation in a form that will allow the qualitative approach to be combined with the quantitative approach is examined. This conception is based on an understanding of the essence of human endeavor in automated control systems that now determine the development of society's productive forces and that are the main object of ergonomic research. Two main types of operator participation were examined; information retrieval with immediate service and information retrieval with delayed service.

Zarakovskiy, G. M.↗
NASA NTRS1972

Mini-arc orbit determination for the Geos C altimetry experiment.

The problem is, given simultaneous observations of an altimeter-bearing geodetic satellite, from three or more high-precision radar stations, to determine its orbit to submeter accuracy in the presence of perturbations arising from strong, localized gravitational anomalies. A new solution to this problem involves the use of an f and g series specialized to the determination of radial distance (pertinent to the satellite altimeter experiment) to process data over a very short arc (e.g., 6 sec to 10 min). Such a short arc is termed a 'mini-arc.' In this approach, the data batches are connected by dynamics, rather than by the usual curve fit to a power series in time. A nonunity value of the mass factor is introduced to serve as an 'alias' for the perturbations that affect the satellite's path during the mini arc. The essence of the mini-arc approach is to include the influence of the far, or relatively lower-order, force field analytically and to solve for the remaining fine structure with accuracies that can approach a few centimeters.

Baker, R. M. L., Jr.↗
NASA NTRS1973

Mathematical modeling of spinning elastic bodies for modal analysis.

The problem of modal analysis of an elastic appendage on a rotating base is examined to establish the relative advantages of various mathematical models of elastic structures and to extract general inferences concerning the magnitude and character of the influence of spin on the natural frequencies and mode shapes of rotating structures. In realization of the first objective, it is concluded that except for a small class of very special cases the elastic continuum model is devoid of useful results, while for constant nominal spin rate the distributed-mass finite-element model is quite generally tractable, since in the latter case the governing equations are always linear, constant-coefficient, ordinary differential equations. Although with both of these alternatives the details of the formulation generally obscure the essence of the problem and permit very little engineering insight to be gained without extensive computation, this difficulty is not encountered when dealing with simple concentrated mass models.

Likins, P. W.↗
NASA NTRS1974

Origin of QSO absorption lines

Consideration of the origin of the absorption lines in QSOs with observed absolute redshifts much less than the empirical values. As a possible alternative to the plasmoid mechanism for decreasing the relatively large possible macroscopic or bulk motions in QSO clouds, it is shown that certain large relative bulk motions in QSO clouds can be dissipated without the presence of strong magnetic fields and without large adiabatic expansions. The essence of the argument is that a cloud with convergent internal velocities can coalesce inelastically, because the internal kinetic energy can be dissipated and radiated away. There are thus indications that observed QSO absorption clouds may have their origin in clouds with internal velocities which are convergent.

Opher, R.↗
NASA NTRS1974

Determining spacecraft and airplane angular orientation from star photographs

The advantages of determining spacecraft angular orientation from star photographs include the documental nature and objectivity of the photographic image and also the high accuracy of construction of the reference system based on the stars. Use of the method presupposes installation aboard the vehicle of a specialized photographic camera adapted for photographing the stellar sky. From the mathematical viewpoint, the essence of the method amounts to: (1) Certain directions in space are identified and their direction cosines are determined in a specified coordinate system. (2) The direction cosines of these same directions are determined relative to a coordinate system fixed with the vehicle. (3) The sought angular orientation of the vehicle is calculated using the coupling equations between the specified and vehicle-fixed coordinate systems. In principle, vehicle angular orientation can be determined relative to any given reference system.

Elbakyan, K. I.↗
NASA NTRS1974

Origins of biological information and the genetic code

Information, defined as the capacity of a molecule or system for selective interactions with other molecules or systems, is followed through its evolution from prebiological information to protoribosomes. Emphasis is on proteins and protein-like polymers, and later on ATP. The research will contribute more to the understanding of the essence of the genetic mechanism.

Fox, S. W.↗
NASA NTRS1977

Two phase choke flow in tubes with very large L/D

Data were obtained for two phase and gaseous choked flow nitrogen in a long constant area duct of 16200 L/D with a diverging diffuser attached to the exit. Flow rate data were taken along five isotherms (reduced temperature of 0.81, 0.96, 1.06, 1.12, and 2.34) for reduced pressures to 3. The flow rate data were mapped in the usual manner using stagnation conditions at the inlet mixing chamber upstream of the entrance length. The results are predictable by a two phase homogeneous equilibrium choking flow model which includes wall friction. A simplified theory which in essence decouples the long tube region from the high acceleration choking region also appears to predict the data resonably well, but about 15 percent low.

Hendricks, R. C.↗
NASA NTRS1977

A new method for predicting response in complex linear systems. II

The paper describes convergence and response studies in the low frequency range of complex systems, particularly with low values of damping of different distributions, and reports on the modification of the relaxation procedure required under these conditions. A new method is presented for response estimation in complex lumped parameter linear systems under random or deterministic steady state excitation. The essence of the method is the use of relaxation procedures with a suitable error function to find the estimated response; natural frequencies and normal modes are not computed. For a 45 degree of freedom system, and two relaxation procedures, convergence studies and frequency response estimates were performed. The low frequency studies are considered in the framework of earlier studies (Kayser and Bogdanoff, 1975) involving the mid to high frequency range.

Bogdanoff, J. L.↗
NASA NTRS1978

Preliminary study of a large span-distributed-load flying-wing cargo airplane concept

An aircraft capable of transporting containerized cargo over intercontinental distances is analyzed. The specifications for payload weight, density, and dimensions in essence configure the wing and establish unusually low values of wing loading and aspect ratio. The structural weight comprises only about 18 percent of the design maximum gross weight. Although the geometric aspect ratio is 4.53, the winglet effect of the wing-tip-mounted vertical tails, increase the effective aspect ratio to approximately 7.9. Sufficient control power to handle the large rolling moment of inertia dictates a relatively high minimum approach velocity of 315 km/hr (170 knots). The airplane has acceptable spiral, Dutch roll, and roll-damping modes. A hardened stability augmentation system is required. The most significant noise source is that of the airframe. However, for both take-off and approach, the levels are below the FAR-36 limit of 108 db. The design mission fuel efficiency is approximately 50 percent greater than that of the most advanced, currently operational, large freighter aircraft. The direct operating cost is significantly lower than that of current freighters, the advantage increasing as fuel price increases.

Jernell, L. S.↗
NASA NTRS1977

Two phase choke flow in tubes with very large L/D

Two phase and gaseous choked flow data for fluid nitrogen were obtained for a test section which was a long constant area duct of 16 200 L/D with a diverging diffuser attached to the exit. Flow rate data were taken along five isotherms (reduced temperature of 0.81, 0.96, 1.06, 1.12, and 2.34) for reduced pressures to 3. The flow rate data were mapped in the usual manner using stagnation conditions at the inlet mixing chamber upstream of the entrance length. The results are predictable by a two-phase homogeneous equilibrium choking flow model which includes wall fraction. A simplified theory which in essence decouples the long tube region from the high acceleration choking region also appears to predict the data reasonably well, but about 15 percent low.

Hendricks, R. C.↗
NASA NTRS1977

Magma oceanography. I - Thermal evolution

Fractional crystallization and flotation of cumulate plagioclase in a cooling 'magma ocean' provides the simplest explanation for early emplacement of a thick feldspar-rich lunar crust. The complementary mafic cumulates resulting from the differentiation of such a magma ocean have been identified as the ultimate source of mare basalt liquids on the basis or rare-earth abundance patterns and experimental petrology studies. A study is conducted concerning the thermal evolution of the early differentiation processes. A range of models of increasing sophistication are considered. The models developed contain the essence of the energetics and the time scale for magma ocean differentiation. Attention is given to constraints on a magma ocean, modeling procedures, single-component magma oceans, fractionating magma oceans, and evolving magma oceans.

Solomon, S. C.↗
NASA NTRS1977

Minimax decoding of cyclic block codes

A minimax decoding algorithm utilizing soft bit detection of an (n,k) cyclic block code is described which will permit the correction of up to n-k bit errors interspersed at random locations throughout the block. The decoding solution consists of: (1) identifying the ordered soft bit set and, (2) finding the minimum order solution to the resulting syndrome equations where the nonzero error vector components are constrained to be a subset of the soft bit set. An efficient implementation of the decoding operation is described. In essence, this algorithm focuses the correction capability of the code on those bit positions which have the lowest a posteriori probabilities of correct detection.

Greene, E. P.↗
NASA NTRS1979

A dynamic integrated test for the Space Shuttle

The dynamic integrated test (DIT) has been designed to perform a final checkout of the assembled Space Shuttle vehicle at Kennedy Space Center. The fact that the vehicle is not in a laboratory environment for the test represents a significant constraint in that the use of test equipment is extremely limited, and environment models cannot be used. In essence, the DIT causes the vehicle to believe that it is flying, so that hardware and software systems are exercised much as they would be for a real flight. This technique provides a tool for verifying such items as data bus activity patterns, critical timing sequences, software and hardware moding as a function of flight parameters, absence of EMI problems and other systems interactions which cannot be tested fully in the laboratory.

Brody, S.↗
NASA NTRS1980

From inanimate matter to living systems

Since the early part of this century, the Genesis account of the origin and evolution of life has been explained as an extrapolation of astronomical and geochemical processes. The essence of the answer to date is a protoreproductive protocell of much biochemical and cytophysical competance. The processes of its origin, molecular ordering, and its functions are described. A crucial understanding is that of the nonrandomness of evolutionary processes at all stages (with perhaps a minor statistical component). In this way, evolution conflicts with statistical randomness; the latter is a favorite assumption of both scientific and creationistic critics of the proteinoid theory. The principle contribution of the proteinoid theory to the understanding of general biology is to particularize the view that evolutionary direction is rooted in the shapes of molecules, in stereochemistry. After molecules of the right kind first assembled to protocells, life in its various stages of evolution was an inevitable consequence. It is molecules that continue to assemble as part of living process and, in the role of enzymes, continue to direct life cycle of the cell.

Fox, S. W.↗
NASA NTRS1980

Numerical solution techniques for unsteady transonic aerodynamics problems

Basic concepts of finite difference solution techniques for unsteady transonic flows are presented. The hierarchy of mathematical forumulations that approximate the Navier-Stokes equations are reviewed. The basic concepts involved in constructing numerical algorthms to solve these formulations are given. Semi-implicit and implicit schemes are constructed and analyzed. The discussion focuses primarily on techniques for solving the low frequency transonic small disturbance equation. This is the simplest formulation that contains the essence of inviscid unsteady transonic flow physics. The low frequency formulation is emphasized here because codes based on this theory can be run in minutes of processor time on currently available computers. Furthermore, numerical techniques involved in solving this simple formulation also apply to the more complicated formulations. Extensions to these formulations are briefly described. An indication of the present capability for solving unsteady transonic flows is provided. Important areas of future research for the advancement of computational unsteady transonic aerodynamics are described.

Ballhaus, W. F.↗
NASA NTRS1980

Compliant surfaces - Introduction

It is noted that the essence of the compliant surface question is whether or not wall motion can provide a decrease in skin friction for either transitional or turbulent flows. This wall motion is capable of being externally excited or flow driven, with varying amounts of fluid motion-wall motion phasing (depending primarily upon wall structural configuration and damping). It is concluded that current research has eroded still further the experimental data base which indicates drag reduction on compliant surfaces under turbulent boundary layers in air. The need for further clarification and research is stressed for the small wavelength liquid case.

Bushnell, D. M.↗
NASA NTRS1981

Variable N-type negative resistance in an injection-gated double-injection diode

Double-injection (DI) switching devices consist of p+ and n+ contacts (for hole and electron injection, respectively), separated by a near intrinsic semiconductor region containing deep traps. Under proper conditions, these devices exhibit S-type differential negative resistance (DNR) similar to silicon-controlled rectifiers. With the added influence of a p+ gate appropriately placed between the anode (p+) and cathode (n+), the current-voltage characteristic of the device has been manipulated for the first time to exhibit a variable N-type DNR. The anode current and the anode-to-cathode voltage levels at which this N-type DNR is observed can be varied by changing the gate-to-cathode bias. In essence, the classical S-type DI diode can be electronically transformed into an N-type diode. A first-order phenomenological model is proposed for the N-type DNR.

Kapoor, A. K.↗
NASA NTRS1982

Concepted design of a surface measurement system for large deployable space antennas

The sensor system is in essence a point design, specifically interfacing with the Harris, Inc., 1000 meter deployable mesh communication antenna. The design can, without large modification, be adapted to other large deployable antennas such as the Lockheed Wrap-rib, the General Dynamics Precision Erectable Truss and the TRW Advanced Sunflower antennas. Measurements are optical displacements. The elements of the system are a central cluster of receivers near the apex of the antenna and active bright targets at the antenna. The cluster defines a single coordinate frame from which all surface positions are referenced. The receivers continuously observe an extended array of sample points located throughout the reflecting surface and its supporting structure. For the Harris antenna, the surface samples are at the mesh gore lines and at the supporting hoop. Output data is in real-time, compatible with on-board processing and active control of antenna figure. Lifetime of the system is at least 10 years continuous operation in space.

Neiswander, R. S.↗