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  • 11
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    Apollo space crew cardiovascular evaluations (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Cardiovascular responses associated with pre- and postflight orthostatic tolerance evaluations of Apollo crewmen are presented with a brief historical survey and a discussion of their implications for future manned space flight. Heart rates were increased while systolic and pulse pressures were decreased during the immediate postflight orthostatic evaluation. A postflight elevation in resting heart rate was a less frequent finding.
    Keywords: BIOSCIENCES
    Type: Aerospace Medicine; 45; Aug. 197
    Format: text
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  • 12
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    Lubrication with solids. (1972)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Brief discussion of the historical background, variety range, chemistry, physics, and other properties of solid lubricants, and review of their current uses. The widespread use of solid lubricants did not occur until about 1947. At present, they are the object of such interest that a special international conference on their subject was held in 1971. They are used at temperatures beyond the useful range of conventional lubricating oils and greases. Their low volatility provides them with the capability of functioning effectively in vacuum and invites their use in space applications. Their high load carrying ability makes them useful with heavily loaded components. Solid lubricants, however, do lack some of the desirable properties of conventional lubricants. Unlike oils and greases, which have fluidity and can continuously be carried back into contact with lubricated surfaces, solid lubricants, because of their immobility, have finite lives. Also, oils and greases can carry away frictional heat from contacting surfaces, while solid lubricants cannot.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: Chem Tech; May 1972
    Format: text
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  • 13
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    Determination of cardiac size from chest roentgenograms following Skylab missions (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Decreased cardiothoracic transverse diameter ratios following Mercury, Gemini and Apollo space flights have been reported previously. To evaluate further changes in cardiac size, standard posteroanterior chest films in systole and diastole were obtained before flight and within a few hours after recovery on each of the Skylab astronauts. Postflight chest X-rays were visually compared to the preflight roentgenograms for possible changes in pulmonary vasculature, lung parenchyma, bony or soft tissue structures. From these roentgenograms the following measurements were obtained: cardiac and thoracic transverse diameters, cardiothoracic transverse diameter ratio, cardiac area from the product of both diagonal diameters, cardiac silhouette area by planimetry, thoracic cage area and cardiothoracic area ratio. The postflight frontal cardiac silhouette sizes were significantly decreased when compared with the respective preflight values (P0.05 or 0.01). The observed changes are thought to be related to postflight decrease in the intracardiac chamber volume.
    Keywords: AEROSPACE MEDICINE
    Type: Proc. of the Skylab Life Sci. Symp., Vol. 2; p 785-793
    Format: application/pdf
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  • 14
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    Evaluation of the electromechanical properties of the cardiovascular system (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Cardiovascular electromechanical measurements were collected on returning Skylab crewmembers at rest and during both lower body negative pressure and exercise stress testing. These data were compared with averaged responses from multiple preflight tests. Systolic time intervals and first heart sound amplitude changes were measured. Clinical cardiovascular examinations and clinical phonocardiograms were evaluated. All changes noted returned to normal within 30 days postflight so that the processes appear to be transient and self limited. The cardiovascular system seems to adapt quite readily to zero-g, and more importantly it is capable of readaptation to one-g after long duration space flight. Repeated exposures to zero-g also appear to have no detrimental effects on the cardiovascular system.
    Keywords: AEROSPACE MEDICINE
    Type: Proc. of the Skylab Life Sci. Symp., Vol. 2; p 681-709
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  • 15
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    Vectorcardiographic results from Skylab medical experiment M092: Lower body negative pressure (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Vectorcardiograms were recorded via a modified Frank lead system from all crewmen of the three Skylab missions in conjuction with the Lower Body Negative Pressure - M092 Experiment. Data were analyzed by a specially developed computer program (VECTAN). Design of the test sequences allowed direct comparisons of supine resting, Earth based (reference) vectorcardiograms with those taken during lower body negative pressure stress and those obtained at rest in orbit, as well as combinations of these conditions. Results revealed several statistically significant space flight related changes; namely, increased testing and lower body negative pressure stressed heart rates, modestly increased PR interval and corrected QTC interval, and greatly increased P and QPS loop maximal amplitudes. In addition, orientation changes in the QRS maximum vector and the J-vector at rest in space seem quite consistent among crewmen and different from those caused by the application of lower body negative pressure. No clinical abnormalities were observed. Etiology of these findings is conjectured to be, at least in part, related to fluid mass shifts occurring in weightlessness and attendant alterations in cardiovascular dynamics and myocardial autonomic control mechanisms.
    Keywords: AEROSPACE MEDICINE
    Type: Proc. of the Skylab Life Sci. Symp., Vol. 2; p 597-621
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  • 16
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    Lower body negative pressure: Third manned Skylab mission (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The crew of the Skylab 4 Mission exhibited physiological changes during their 84-day mission that resembled but in several important areas did not reach the magnitude of changes exhibited in crewmen of the two earlier Skylab flights. At rest all three crewmen showed, in comparison to preflight levels, elevated mean systolic and pulse pressures and decreased mean diastolic and mean arterial pressures. Similar changes were seen in most Skylab 2 and Skylab 3 crewmen. While mean resting heart rates of both the Skylab 3 and Skylab 4 crews were elevated, those of the Skylab 2 crew were, however, lower than during preflight tests. Stressed heart rates followed previous patterns in being consistently elevated over preflight values. Postflight changes in cardiovascular parameters for the most part resembled those seen in previous crewmen of space missions. Their recovery to preflight limits occurred rapidly. In-flight data and subjective impressions of the crewmen confirmed that lower body negative pressure in weightlessness imposed a greater stress upon the cardiovascular system than in earth's gravity.
    Keywords: AEROSPACE MEDICINE
    Type: Proc. of the Skylab Life Sci. Symp., Vol. 2; p 545-595
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  • 17
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    Graphite fiber polyimide composites for spherical bearings to 340 C (650 F) (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Journal bearings with self-alining spherical elements of graphite-fiber-reinforced-polyimide composites were tested from 24 to 340 C (75 to 650 F) at unit loads up to 3.5 times 10 to the 7th power N/sq m (5000 psi). The journal oscillated in the cylindrical bore of the composite element + or - 15 deg at 1 hertz. Outer races and journals were metal hardened of Rockwell C-32 and finished to 10 to the minus 7th power m. A 45 wt. percent graphite-fiber composite gave low friction (0.08 to 0.13), low wear, and almost no plastic deformation under any of the test conditions. Composites with 15 and 25 wt. percent graphite fiber failed by plastic deformation at 315 C (600 F) and 3.5 times 10 to the 7th power N/sq m (5000 psi). A composite with 60 wt. percent graphite fiber failed by brittle fracture under the same conditions, but had very low friction coefficients (0.05 to 0.10) and may be a good bearing material at lighter loads.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-7078 , E-7063
    Format: application/pdf
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  • 18
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    Quasi-one-dimensional compressible flow across face seals and narrow slots. 1: Analysis (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An analysis is presented for compressible fluid flow across shaft face seals and narrow slots. The analysis includes fluid inertia, viscous friction, and entrance losses. Subsonic and choked flow conditions can be predicted and analyzed. The model is valid for both laminar and turbulent flows. Results agree with experiment and with solutions which are more limited in applicability. Results show that a parallel film can have a positive film stiffness under choked flow conditions.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-6668 , E-6819
    Format: application/pdf
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  • 19
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    Design study of shaft face seal with self-acting lift augmentation. 5: Performance in simulated gas turbine engine operation (1971)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The feasibility and the noncontact operation of the self-acting seal was demonstrated over a range of simulated gas turbine engine conditions from 200 to 500 ft/sec sliding speed. Sealed pressure differentials were 50 to 300 psi and sealed temperatures were 150 to 1200 F. Low leakage (about 1/10 that of conventional labyrinth seals) was exhibited in two endurance runs (200 and 338 hr) at 400 ft/sec, 200 psi and 1000 F (gas temperature). For these endurance runs, the self-acting pad wear was less than 3.8 micrometers (0.00015 in.); this low wear was attributed to the noncontact operation of the primary seal. Operating problems identified were fretting wear of the secondary seal and erosion of the primary seal by hard particles.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-6563 , E-6312
    Format: application/pdf
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  • 20
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    Design study of shaft face seal with self-acting lift augmentation. 4: Force balance (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A method for predicting the operating film thickness of self-acting seals is described. The analysis considers a 16.76-cm mean diameter seal that is typical of large gas turbines for aircraft. Four design points were selected to cover a wide range of operation for advanced engines. This operating range covered sliding speeds of 61 to 153 m/sec, sealed pressures of 45 to 217 N/sq cm abs, and gas temperatures of 311 to 977 K. The force balance analysis revealed that the seal operated without contact over the operating range with gas film thicknesses ranging between 0.00046 to 0.00119 cm, and with gas leakage rates between 0.01 to 0.39 scmm.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-6568 , E-6458
    Format: application/pdf
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