Stability of nonlinear attitude control systems, including particularly effect of large deflection of space vehicles.
Stability of nonlinear attitude control system coupled to flexible spacecraft under large deflection
Yu, Y.-Y.↗
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Startup testing of the SNAP-8 power conversion system
Startup testing of SNAP 8 power conversion system coupled with nuclear reactor simulator
Boecker, F., Jr.↗
Computer program for afterheat temperature distribution for mobile nuclear power plant
ESATA computer program was developed to analyze thermal safety aspects of post-impacted mobile nuclear power plants. Program is written in FORTRAN 4 and designed for IBM 7094/7044 direct coupled system.
Parker, W. G.↗
Flight loads and control
The prediction of flight loads and their potential reduction, using various control logics for the space shuttle vehicles, is very complex. Some factors, not found on previous launch vehicles, that increase the complexity are large lifting surfaces, unsymmetrical structure, unsymmetrical aerodynamics, trajectory control system coupling, and large aeroelastic effects. Discussed are these load producing factors and load reducing techniques. Identification of potential technology areas is included.
Mowery, D. K.↗
Fundamental concepts of structural loading and load relief techniques for the space shuttle
The prediction of flight loads and their potential reduction, using various control system logics for the space shuttle vehicles, is discussed. Some factors not found on previous launch vehicles that increase the complexity are large lifting surfaces, unsymmetrical structure, unsymmetrical aerodynamics, trajectory control system coupling, and large aeroelastic effects. These load-producing factors and load-reducing techniques are analyzed.
Ryan, R. S.↗
Generation and development of a viscous vortex ring.
The vorticity transport and definition of vorticity equations are derived for an axisymmetric incompressible viscous vortex ring. The coupled system is solved numerically by the Peaceman-Rachford method and the method of successive over-relaxation. Instantaneous streaklines, velocity vector fields, vorticity contours, and streamline patterns offer a detailed picture of vortex ring generation. Results compare well with experimental observations of the behavior of viscous vortex rings. The radius, trajectory, and velocity of the ring are calculated and employed to predict the propagation velocity of the vortex ring using the vortex models of Helmholtz and Hill.
Whitehead, K. D.↗
Some problems in astroelasticity.
The author's studies in astroelasticity are reviewed, covering the dynamics of coupled systems of dynamic solids, the vibrations of a paraboloidal antenna, the thermal flutter of spacecraft boom and the effect of large structural deflection on control stability. A method proposed by Popov in nonlinear automatic control theory (1961) is used as the basis of the studies.
Yu, Y.-Y.↗
Interdiffusion behavior of tungsten or rhenium and group 5 and 6 elements and alloys of the periodic table, part 1
Arc cast W, CVD W, CVD Re, and powder metallurgy Re materials were hot isostatically pressure welded to ten different refractory metals and alloys (Cb, Cb-1Zr, Ta, Ta-10W, T-111, ASTAR-811C, W-25Re, Mo-50Re, W-30Re-20Mo, ect.) and thermally aged at 10 to the minus 8th power torr at 1200, 1500, 1630, 1800, and 2000 C for 100 to 2000 hours. Electron beam microprobe analysis was used to characterize the interdiffusion zone width of each couple system as a function of age time and temperature. Extrapolations of interdiffusion zone thickness to 10,000 hours were made. Classic interdiffusion analysis was performed for several of the systems by Boltzmann-Matano analysis. A method of inhibiting Kirkendall voids from forming during thermal ageing of dissimilar metal junctions was devised and experimentally demonstrated. An electron beam weld study of Cb-1Zr to Re and W-25Re demonstrated the limited acceptability of these welds.
Arcella, F. G.↗
Feasibility study of a swept frequency electromagnetic probe (SWEEP) using inductive coupling for the determination of subsurface conductivity of the earth and water prospecting in arid regions
Techniques developed for electromagnetic probing of the lunar interior, and techniques developed for the generation of high power audio frequencies were combined to make practical a magnetic inductive coupling system for the rapid measurement of ground conductivity profiles which are helpful when prospecting for the presence and quality of subsurface water. A system which involves the measurement of the direction, intensity, and time phase of the magnetic field observed near the surface of the earth at a distance from a horizontal coil energized so as to create a field that penetrates the earth was designed and studied to deduce the conductivity and stratification of the subsurface. Theoretical studies and a rudimentary experiment in an arid region showed that the approach is conceptually valid and that this geophysical prospecting technique can be developed for the economical exploration of subterranean water resources.
Latorraca, G. A.↗
Interdiffusion behavior of tungsten or rhenium and group 5 and 6 elements and alloys of the periodic table. Part 2A: Appendices A-G
Arc cast W, CVD, W, CVD Re, and powder metallurgy Re materials were hot isostatically pressure welded to ten different refractory metals and alloys and thermally aged at 10 to the minus 8th power torr at 1200 C, 1500 C, 1630 C, 1800 C, and 2000 C for 100 hours to 2000 hours. Electron beam microprobe analysis was used to characterize the interdiffusion zone width of each couple system as a function of age time and temperature. Each system was least squares fitted to the equation: In (delta X sq/t) = B/T + A, where delta X is net interdiffusion zone width, t is age time, and T is age temperature. Detailed descriptions of experimental and analytical procedures utilized in conducting the experimental program are provided. For Vol. 1, see N74-34046.
Arcella, F. G.↗
Determination of the landing point and orientation of a spacecraft on Mars
Formulas are presented to calculate the landing point of a spacecraft on Mars. The areographic latitude is taken as the angle between a plumb line at the landing point and the plane perpendicular to the axis of rotation of Mars relative to the sun. The ephemeral time of the upper culmination of the sun at the landing point is used to determine areographic longitude. A coupled system and a topocentric system of coordinates are introduced to develop the first series of equations. Both errors which are independent random quantities and systematic errors are considered, as well as the influence of the distance of the landing point from the boundary of the area of polar night.
Mersov, G. A.↗
Prepared to launch
The verification of the interface between the preflight prepare-to-launch and flight program, targeting load, and flight program initialization was described. This is done using the digital command system coupled with a flight program patch and a memory dump command, the 6D/LVDC simulator, and a program trace through phase 1 initialization.
Source record↗
Status of JPL solar powered experiments for terrestrial applications
Results of an ongoing program set up to evaluate solar terrestrial photovoltaic power sources. The results of this program, which now includes a solar array encapsulant and materials test and a solar-powered buoy study, are updated, and the results of efforts to study the dynamic interaction of a solar photovoltaic array and a water electrolysis system coupled to produce hydrogen are reported for the first time.
Yasui, R. K.↗
Chemical potential effects on neutrino diffusion in supernovae
The validity of imposing a zero chemical potential for neutrinos in hydrodynamic calculations of collapsing supernovae is investigated in the diffusion approximation of neutrino transport. A coupled system of equations is solved for neutrino and energy diffusion fluxes as well as lepton diffusion in a collapsing supernovae ambient medium, and the results indicate a substantial growth in the neutrino chemical potential for densities greater than 10 to the 12th power gm/cu cm. The rate of energy transport is shown to be significantly affected by increases in Fermi integrals and chemical-potential gradients accompanied by decreases in temperature, and the extent of neutrino particle/antiparticle reactions is found also to affect energy diffusion rates. It is concluded that the photon-like behavior usually assumed for neutrinos may be incorrect and that an extension of the Sn transport approximation to include lepton characteristics is necessary for a definitive answer to the question of neutrino transport in supernovae.
Mazurek, T. J.↗
Transient excitation and mechanical admittance test techniques for prediction of payload vibration environments
Transient excitation forces were applied separately to simple beam-and-mass launch vehicle and payload models to develop complex admittance functions for the interface and other appropriate points on the structures. These measured admittances were then analytically combined by a matrix representation to obtain a description of the coupled system dynamic characteristics. Response of the payload model to excitation of the launch vehicle model was predicted and compared with results measured on the combined models. These results are also compared with results of earlier work in which a similar procedure was employed except that steady-state sinusoidal excitation techniques were included. It is found that the method employing transient tests produces results that are better overall than the steady state methods. Furthermore, the transient method requires far less time to implement, and provides far better resolution in the data. However, the data acquisition and handling problem is more complex for this method. It is concluded that the transient test and admittance matrix prediction method can be a valuable tool for development of payload vibration tests.
Kana, D. D.↗
The solar-terrestrial observatory as a major module of a space station
The solar-terrestrial environment is a dynamic, tightly coupled system in which variable solar energy is transmitted through electromagnetic radiation and the solar wind to the earth's magnetosphere and atmosphere. The constantly changing solar input and the continuous redistribution of energy near the earth combine to determine the characteristics of our global environment. An understanding and subsequent management of this environment will require a coordinated set of observations of solar processes and the accompanying magnetospheric and atmospheric responses. A major element in this observational plan should be a Solar-Terrestrial Observatory module of a manned Space Station in which instruments and experimental techniques developed during short-duration Spacelab flights will be applied to extended missions in both low-altitude and geosynchronous orbits.
Chappell, C. R.↗
Design of noninteracting flight control systems in the presence of large parameter variations
The effects of system parameter variations on the over-all system stability were considered. Results from the application of numerical minimization to reduce system coupling are given and some future research directions are outlined.
Barnes, F. S.↗
Employing static excitation control and tie line reactance to stabilize wind turbine generators
An analytical representation of a wind turbine generator is presented which employs blade pitch angle feedback control. A mathematical model was formulated. With the functioning MOD-0 wind turbine serving as a practical case study, results of computer simulations of the model as applied to the problem of dynamic stability at rated load are also presented. The effect of the tower shadow was included in the input to the system. Different configurations of the drive train, and optimal values of the tie line reactance were used in the simulations. Computer results revealed that a static excitation control system coupled with optimal values of the tie line reactance would effectively reduce oscillations of the power output, without the use of a slip clutch.
Hwang, H. H.↗