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At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

The inclusion of rotor dynamics in controller design for helicopters.

State-feedback-controllers and state-estimators (filters) are designed for the roll-pitch-horizontal motions of a helicopter near hover, using a new quadratic synthesis technique. One model (tenth order) uses a dynamic model of the rotor, whereas the other model (sixth order) assumes the rotor can be tilted instantaneously. It is shown that, for tight control, neglecting the rotor dynamics in designing the autopilot can produce unstable closed-loop response on the model that includes rotor dynamics. Two filters are designed to use only fuselage sensors and two are designed to use both fuselage and rotor sensors. It is shown that rotor states can be estimated with sufficient accuracy using only fuselage sensors so that it does not seem worthwhile to use rotor sensors. The mean square response of the vehicle to a gusty, random wind, using several different filter/state-feedback compensators, is shown to be satisfactory.

Hall, W. E., Jr.↗
NASA NTRS1972

The Oro Grande, New Mexico, chondrite and its lithic inclusion.

The Oro Grande, New Mexico, U.S.A., chondrite was found in 1971. Electron microprobe analyses and microscopic examination show the following mineralogy: olivine (Fa 19.3 mole %), orthopyroxene (Fs 16.2 mole %), diopside, feldspar (An 13.6 mole %), chlorapatite, whitlockite, kamacite, taenite, troilite, chromite, and an iron-bearing terrestrial weathering product. A bulk chemical analysis of the meteorite shows the following results (weight %): Fe 0.84, Ni 1.46, Co 0.07, FeS 3.62, SiO2 34.18, TiO2 0.14, Al2O3 1.83, Cr2O3 0.55, Fe2O3 21.25, FeO 9.13, MnO 0.31, MgO 21.52, CaO 1.72, Na2O 0.70, K2O 0.08, P2O5 0.25, H2O(+) 2.14, H2O(-) 0.40, C 0.22, sum 100.41. On the basis of composition and texture the Oro Grande meteorite is classified as an H5 chondrite.

Fodor, R. V.↗
NASA NTRS1972

Organic inclusions within hydrothermal minerals from S.W. Africa and elsewhere.

It was observed that quartz crystals from veins within a diabase dike of precambrian age from S.W. Africa contain organic particles which closely resemble, in detailed morphology, coacervates, proteinoid microspheres or fossil and recent microorganisms. The microphotospectrographs in visible and near-ultraviolet light of these minute particles revealed a strong absorption peak at the vicinity of 4000 A, which is indicative of lipids. Hydrothermal mineral from veins from a number of other localities proved to contain the biomorphic organic particles. The theoretical significance of these organic particles is discussed with reference to problems of origin of life.

Mueller, G.↗
NASA NTRS1974

Inclusion of known integrals in the optimal trajectory problem

The classical problem of determination of the rocket trajectory which minimizes mass expenditure during motion between two points in the field of a single gravitating body is analyzed. The known integrals of the system are incorporated into the adjoint equations resulting in a reduction from a seventh-order adjoint system to a third-order adjoint system. The first case which is treated in that of planar motion under specific end conditions. In this case a regularization of the recently derived equations is achieved. The general three-dimensional case is also reduced from a seventh-order adjoint system to a third-order adjoint system. In this case a regularization has not been found.

Burns, R. E.↗
NASA NTRS1974

Plastic flow around rigid spherical inclusions

The extent of plastic flow in a spherical solid (assumed to be homogeneous and elastically and plastically isotropic), surrounding a concentric rigid sphere was calculated as a function of applied external pressure. The applied pressure necessary to cause plastic deformation throughout the solid was obtained.

Ruoff, A. L.↗
NASA NTRS1974

Inclusion of transverse shear deformation in finite element displacement formulations

A stiffness matrix is derived for a beam element with transverse shear deformation. It is shown that straightforward energy minimization yields the correct stiffness matrix in displacement formulations when transverse shear effects are considered. Since the TIM4 beam element does not represent the geometric boundary conditions for a cantilever beam the rotation of the normal must be retained as a grid point degree of freedom.

Narayanaswami, R.↗