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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Relation of a contracting earth to the apparent accelerations of the sun and moon

It has been concluded that the theoretical ratio of the apparent secular accelerations of the moon and the sun implied by tidal theory is far higher than the ratio of observed values. This paper shows that the discrepancy can be entirely removed within the range of uncertainty of the various quantities involved if terms making allowance for a secularly decreasing terrestrial moment of inertia are included in the dynamical equations for the apparent secular accelerations. Such a decrease has already been predicted on the basis of the phase-change hypothesis for the nature of earth's core. The development of this hypothesis is reviewed, the modified dynamical equations are derived, and values of tidal couples implied by existing observational data are examined. The numerically determined rate of decrease of earth's moment of inertia is found to be in close agreement with that predicted by the phase-change hypothesis. The results indicate that a diminishing gravitational constant is unlikely, that the moon would have been in close proximity to earth only 1 billion years ago, and that earth's rotation period at that time would have been about 5 hr.

Lyttleton, R. A.↗
NASA NTRS1977

NASA's university program: Active grants and research contracts, fiscal year 1977

As basic policy NASA believes that colleges and universities should be encouraged to participate in the nation's space and aeronautics program to the maximum extent practicable. The Office of University Affairs (OUA) serves as a focal point for NASA's relationships with colleges and universities. One of its roles is to provide information on the NASA University Program. The present document is designed to serve several purposes and a wide range of audiences from private individuals to NASA employees. The emphasis is on the technical content of the program, rather than on fiscal data, which is available separately from OUA. As some terminology will not be familiar to all readers, a User's Guide is included to facilitate the fullest use of the material related to the interests of any particular reader.

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NASA NTRS1978

NASA's university program: Active grants and research contracts, fiscal year 1978

As basic policy NASA believes that colleges and universities should be encouraged to participate in the space and aeronautics program to the maximum extent practicable. The NASA objective is to have them bring their scientific, engineering, and social research competence to bear on aerospace problems and on the broader social, economic, and international implications of NASA technical and scientific programs. This annual report is one means of documenting the NASA-university relationship, frequently denoted, collectively, as NASA University Program.

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NASA NTRS1979

Analytic theory of orbit contraction due to atmospheric drag

Theory of space vehicle flight in near vacuum and in a planetary atmosphere is unified for the case of a spherically symmetric atmosphere with exponential variation of density with height. Dimensionless equations of motion are established that bridge the gap between satellite theory and entry theory. Integration is done by Poincare's method of perturbations. Solutions for the dimensionless semimajor axis are numerically obtained.

Vinh, N. X.↗
NASA NTRS1980

The contraction and disappearance of the polar coronal holes

He I 10830 A spectroheliograms obtained during 1974-1979 were used to study the evolution of the Sun's polar coronal holes. Synoptic polar plots show that the holes have decreased in size to the point that only vestigual holes remain and even these remnants fluctuate with detailed sunspot activity.

Sheeley, N. R., Jr.↗
NASA NTRS1981

Transfer of line radiation in differentially expanding atmospheres. VI The plane parallel atmosphere with expanding and contracting regions

The non-LTE radiative transfer problem for a two level atom with complete redistribution over a Doppler profile is solved for a plane parallel slab (overlying a radiating photosphere) that has a velocity field which rises symmetrically from zero at either face to a central maximum. Since the velocity gradient reverses, distant layers of the slab become coupled by radiation that jumps intervening layers. The Feautrier method is used, but an iterative variant is also employed as a check in cases where poorly conditioned matrices are encountered. Approximations are developed to explain some of the principal features. It is found that the source function S tends to have two plateaus with values near 2/3 I sub 0 and 1/3 I sub 0, where I sub 0 is the photospheric continuum incident from below; the larger value lies nearer the photosphere. The upper layers sometimes exhibit a rise in S owing to interconnection by radiation to the base. It is noted that the radiation force is largest at the two faces and the midplane. Some line profiles are found to have unusually steep absorptions at rest frequency because of the low excitation in the uppermost, stationary layers.

Noerdlinger, P. D.↗
NASA NTRS1982

Experiments on identification and control of inflow disturbances in contracting streams

Vorticity from all surfaces and isolated objects in the vicinity of the fan intake, including the outside surfaces of the fan housing, were identified as the major sources for disturbances leading to blade passing frequency noise. The previously proposed mechanism based on atmospheric turbulence is refuted. Flow visualization and hot wire techniques were used in three different facilities to document the evolution of various types of disturbances, including the details of the mean flow and turbulence characteristics. The results suggest that special attention must be devoted to the design of the inlet and that geometric modeling may not lead to adequate simulation of the in flight characteristics. While honeycomb type flow manipulators appear to be effective in reducing some of the disturbances, higher pressure drop devices that generate adequate turbulence, for mixing of isolated nonuniformities, may be necessary to suppress the remaining disturbances. The results are also applicable to the design of inlets of open return wind tunnels and similar flow facilities.

Lee, A. H.↗
NASA NTRS1985

Fatigue and contraction of slow and fast muscles in hypokinetic/hypodynamic rats

The effects of hypokinesia/hypodynamia (H/H) on the fatigability and contractile properties of the rat soleus (S) and gastrocnemius (G) muscles have been investigated experimentally. Whole body suspension for one week was used to induce H/H, and fatigue was brought on by train stimulation for periods of 45 and 16 minutes. Following stimulation, rapid rates of fatigue were observed in the G-muscles of the suspended rats, while minimal fatigue was observed in the S-muscles. The twitch and tetanic contractile properties of the muscles were measured before and after train stimulation. It is found that H/H suspension increased twitch tension in the G-muscles, but did not change any contractile properties in the S-muscles. The peak twitch, train, tetanic tensions and time to peak were unchanged in the S-muscles of the suspended rats. On the basis of the experimental results, it is concluded that 1 wk of muscle atropy induced by H/H significantly increases fatigability in G-muscles, but does not affect the contractile properties of fast-twitch and slow-twitch muscles.

Fell, R. D.↗
NASA NTRS1987

High temperature static strain gage development contract, tasks 1 and 2

Results are presented for the first two tasks to develop resistive strain gage systems for use up to 1250 K on blades and vanes in gas turbine engines under tests. The objective of these two tasks was to further improve and evaluate two static strain gage alloys identified as candidates in a previous program. Improved compositions were not found for either alloy. Further efforts on the Fe-11.9Al-10.6Cr weigth percent alloy were discontinued because of time dependent drift problems at 1250 K in air. When produced as a 6.5 micrometer thick sputtered film, the Pd-13Cr weight percent alloys is not sufficiently stable for this use in air at 1250 K and a protective overcoat system will need to be developed.

Hulse, C. O.↗
NASA NTRS1986

Government conceptual estimating for contracting and management

The use of the Aerospace Price Book, a cost index, and conceptual cost estimating for cost-effective design and construction of space facilities is discussed. The price book consists of over 200 commonly used conceptual elements and 100 systems summaries of projects such as launch pads, processing facilities, and air locks. The cost index is composed of three divisions: (1) bid summaries of major Shuttle projects, (2) budget cost data sheets, and (3) cost management summaries; each of these divisions is described. Conceptual estimates of facilities and ground support equipment are required to provide the most probable project cost for budget, funding, and project approval purposes. Similar buildings, systems, and elements already designed are located in the cost index in order to make the best rough order of magnitude conceptual estimates for development of Space Shuttle facilities. An example displaying the applicability of the conceptual cost estimating procedure for the development of the KSC facilities is presented.

Brown, J. A.↗