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  • Other Sources  (333)
  • SPACECRAFT PROPULSION AND POWER  (193)
  • COMPOSITE MATERIALS
  • 1980-1984  (333)
  • 1981  (333)
  • 1
    Publication Date: 2006-01-16
    Description: The hydraulic actuation system of the space shuttle main engine is discussed. The system consists of five electrohydraulic actuators and a single engine filter used to control the five different propellant valves, which in turn control thrust and mixture ratio of the space shuttle main engine. The hydraulic actuation system provides this control with a precision of 98.7 percent or an error in position no greater than 1.3 percent of full scale rotational travel for critical positions.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: the 15th Aerospace Mech. Symp.; p 291-301
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  • 2
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    In:  CASI
    Publication Date: 2006-01-16
    Description: The system components and operation of the space shuttle solid rocket booster (SRB) dewatering set are described. The SRB dewatering set consists of a nozzle plug, control console, remote control unit, power distribution unit, umbilical cable, interconnect cables, and various handling and storage items. The nozzle plug (NP) is a remotely controlled, tethered underwater vehicle that is launched from the retrieval vessel (RV) by a crane, descends down the side of the SRB, and is positioned below the SRB nozzle. A TV camera mounted at the top of the NP central core is used by the control console operator to visually guide the NP during descent and docking. The NP is then driven up and locked into the nozzle. Compressed air is passed through the umbilical from the RV, through the NP and into the SRB motor. The water inside the SRB is expelled causing the SRB to rotate to a near horizontal attitude on the surface of the water.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA. Marshall Space Flight Center The 15th Aerospace Mech. Symp.; p 279-289
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  • 3
    Publication Date: 2006-01-16
    Description: Zero gravity testing in the KC-135 aircraft of flat fold flexible solar array test specimens sufficiently demonstrated the adequacy of the panel design. The aircraft flight crew provided invaluable assistance and significantly contributed to the design and development of the flexible solar array, and ultimately to the potential success of the solar electric propulsion solar array shuttle flight experiment program.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: The 15th Aerospace Mech. Symp.; p 115-136
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  • 4
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 13 p
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  • 5
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 19 p
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  • 6
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 19 p
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  • 7
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 11 p
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  • 8
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 22 p
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  • 9
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 15 p
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  • 10
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 5 p
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  • 11
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 16 p
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  • 12
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 5 p
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  • 13
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 21 p
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  • 14
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 13 p
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  • 15
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 6 p
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  • 16
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 4 p
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  • 17
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 7 p
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  • 18
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 10 p
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  • 19
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 16 p
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  • 20
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 25 p
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  • 21
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 7 p
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  • 22
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 33 p
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  • 23
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 100 p
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  • 24
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 13 p
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  • 25
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 109 p
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  • 26
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 39 p
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  • 27
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 12 p
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  • 28
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 13 p
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  • 29
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 19 p
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  • 30
    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 27 p
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  • 31
    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAFF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 5 p
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  • 32
    Publication Date: 2011-08-19
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JANNAFF Handbook: Rocket Exhaust Plume Technol., Chapter 5; 5 p
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  • 33
    Publication Date: 2011-08-18
    Description: The feasibility of modifying resin matrix composites to reduce the potential of electrical shorting from fire released fiber was explored. The effort included modifications to or coatings for graphite fibers, alternative fibers, modifications to matrix materials, and hybrid composites. The objectives included reduction of the conductivity of the graphite fiber, char formation to reduce fiber release, glass formation to prevent fiber release, catalysis to assure fiber consumption in a fire, and replacement of the graphite fibers with nonconductive fibers of similar mechanical potential.
    Keywords: COMPOSITE MATERIALS
    Type: Executive Office of the President Carbon(Graphite Composite Material Study; p 101-105
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  • 34
    Publication Date: 2011-08-18
    Description: The subject interface measurements are described for the Ion Auxiliary Propulsion System (IAPS) flight test of two 8-cm thrusters. The diagnostic devices and the effects to be measured include: 1) quartz crystal microbalances to detect nonvolatile deposition due to thruster operation; 2) warm and cold solar cell monitors for nonvolatile and volatile (mercury) deposition; 3) retarding potential ion collectors to characterize the low energy thruster ionic efflux; and 4) a probe to measure the spacecraft potential and thruster generated electron currents to biased spacecraft surfaces. The diagnostics will also assess space environmental interactions of the spacecraft and thrusters. The diagnostic data will characterize mercury thruster interfaces and provide data useful for future applications.
    Keywords: SPACECRAFT PROPULSION AND POWER
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  • 35
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    Publication Date: 2011-08-18
    Description: A comprehensive assessment of the possible damage to electrical and electronic equipment caused by accidental release of carbon fibers from burning civil aircraft with carbon composite parts was completed. The study concluded that the amount of fiber likely to be released is much lower than initially predicted. Carbon fiber released from an aircraft crash fire was found (from atmospheric dissemination models) to disperse over a much larger area than originally estimated, with correspondingly lower fiber concentrations. Long term redissemination of fiber was shown to be insignificant if reasonable care is exercised in accident cleanup. The vulnerability of electrical equipment to structural fibers in current use was low. Consumer appliances, industrial electronics, and avionics were essentially invulnerable to carbon fibers. Shock hazards (and thus potential injury or death) were found to be extremely unlikely.
    Keywords: COMPOSITE MATERIALS
    Type: Executive Office of the President Carbon(Graphite Composite Material Study; p 48-100
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  • 36
    Publication Date: 2011-08-18
    Description: The accidental release of carbon fibers from civil aircraft and the need for protection of civil aircraft systems from such fibers were studied. It was concluded that the electrical hazard from carbon fibers accidentally released in an aircraft crash fire pose no threat to human life. Overall costs associated with carbon fiber release are predicted to be extremely low. The risk of electrical or electronic failures due to carbon fibers is so minimal that future exploitation of carbon composites in aircraft should be continued. Additional protection of aircraft avionics to guard against carbon fibers is unnecessary. A program to develop alternate materials specifically to overcome the potential electrical hazard is not justified.
    Keywords: COMPOSITE MATERIALS
    Type: Executive Office of the President Carbon(Graphite Composite Material Study; p 6-10
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  • 37
    Publication Date: 2011-08-18
    Description: An orthotropic double cantilever beam (DCB) model is used to study dynamic crack propagation and arrest in 90 deg unidirectional Hercules AS/3501-6 graphite fiber epoxy composites. The dynamic fracture toughness of the composite is determined from tests performed on the long-strip specimen and DCB crack arrest experiments are conducted. By using the dynamic fracture toughness in a finite-difference solution of the DCB governing partial differential equations, a numerical solution of the crack propagation and arrest events is computed. Excellent agreement between the experimental and numerical crack arrest results are obtained.
    Keywords: COMPOSITE MATERIALS
    Type: Engineering Fracture Mechanics; 14; 2, 19; 1981
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  • 38
    Publication Date: 2011-08-18
    Description: A charge-exchange plasma, generated by an ion thruster, is capable of flowing upstream from the ion thruster and therefore represents a source of contamination to a spacecraft. An analytical model of the charge-exchange plasma density around a spacecraft was used to estimate the contamination which various spacecraft materials may be exposed to. Measurements of plasma density around an ion thruster were compared to this model. Results of experimental studied regarding the effects on various spacecraft materials' properties due to exposure to expected mercury contamination levels are presented.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Exptl. and Anal. Evaluation of Ion Thruster(Spacecraft Interactions; p 231-241
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  • 39
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    Publication Date: 2011-08-18
    Description: A study was performed to determine the effects of a mercury ion thruster plume on an S-band telecommunication carrier. Experiments were carried out on a 30 cm thruster in a JPL test chamber. Results from simple analytical models were compared with the above measurements and major discrepancies were discovered. Modifications to the electron density model provided a qualitative explanation, but further work is necessary for a quantitative answer. The results indicate the effects of the plume, on S and X Band telecommunications will be minor, with the possible exception of critical angle blockage.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Exptl. and Anal. Evaluation of Ion Thruster(Spacecraft Interactions; p 191-215
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  • 40
    Publication Date: 2011-08-18
    Description: An electric propulsion thrust system has the capability of providing a high specific impulse for long duration scientific missions in space. The EMI from the elements of an ion engine was characterized. The compatibility of ion drive electric propulsion systems with typical interplanetary spacecraft engineering was predicted.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Exptl. and Anal. Evaluation of Ion Thruster(Spacecraft Interactions; p 185-190
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  • 41
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    Publication Date: 2011-08-18
    Description: In order to properly assess the interaction of a spacecraft with the EMI environment produced by an ion thruster, the EMI environment was characterized. Therefore, radiated and conducted emissions were measured from a 30-cm mercury ion thruster. The ion thruster beam current varied from zero to 2.0 amperes and the emissions were measured from 5 KHz to 200 MHz. Several different types of antennas were used to obtain the measurements. The various measurements that were made included: magnetic field due to neutralizer/beam current loop; radiated electric fields of thruster and plume; and conducted emissions on arc discharge, neutralizer keeper and magnetic baffle lines.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Exptl. and Anal. Evaluation of Ion Thruster(Spacecraft Interactions; p 167-183
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  • 42
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    Publication Date: 2011-08-18
    Description: These facility produced ions are created by charge-exchange collisions between neutral atoms and energetic thruster beam ions. The result of the electron transfer is an energetic neutral atom and an ion of only thermal energy. There are true charge-exchange ions produced by collisions with neutrals escaping from the ion thruster and being charge-exchange ionized before the neutral intercepts the tank wall. The facility produced charge-exchange ions will not exist in space and therefore, represent a source of error where measurements involving ion thruster plasmas and their density are involved. The quantity of facility produced ions in a test chamber with a 30 cm mercury ion thruster was determined.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Exptl. and Anal. Evaluation of Ion Thruster(Spacecraft Interactions; p 147-166
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  • 43
    Publication Date: 2011-08-18
    Description: Under the proper conditions there is an end-effect of a long, cylindrical Langmuir probe which allows a significant increase in collected ion current when the probe is aligned with a flowing plasma. This effect was used to determine the charge-exchange plasma flow direction at various locations relative to the ion thruster. The ion current collected by the probe as a function of its angle with respect to the plasma flow allows determination of the plasma density and plasma flow velocity at the probe's location upstream of the ion thruster optics. The density values obtained from the ion current agreed to within a factor of two of density values obtained by typical voltage-current Langmuir probe characteristics.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Exptl. and Anal. Evaluation of Ion Thruster(Spacecraft Interactions; p 67-72
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  • 44
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    Publication Date: 2011-08-18
    Description: Biasing techniques and their application to the control of spacecraft potential is discussed. Normally when a spacecraft is operated with ion thrusters, the spacecraft will be 10-20 volts negative of the surrounding plasma. This will affect scientific measurements and will allow ions from the charge-exchange plasma to bombard the spacecraft surfaces with a few tens of volts of energy. This condition may not be tolerable. A proper bias system is described that can bring the spacecraft to or near the potential of the surrounding plasma.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Exptl. and Anal. Evaluation of Ion Thruster(Spacecraft Interactions; p 11-28
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  • 45
    Publication Date: 2011-08-18
    Description: The strain sensitivity of an optical fiber interferometer developed for the detection of pulsed ultrasonic waves in solids was calibrated. Light from the output ends of both fibers was superimposed to form an interference fringe pattern that was interrogated in the far field to give a signal proportional to the differential optical fiber path length. Strain sensitivity is determined by comparing data obtained by clamping and bending the bar at different lengths to simple cantilever beam theory. A minimum theoretical detectable strain of less than 10 to the minus 10th power is indicated.
    Keywords: COMPOSITE MATERIALS
    Type: Va. Polytech. Inst. and State Univ. Opt. Fiber Interferometer for the Study of Ultrasonic Waves in Composite Mater.; p 13-15
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  • 46
    Publication Date: 2011-08-18
    Description: An optical fiber interferometer was developed for the detection of ultrasonic waves in solids. The optical paths in both the signal and reference arms of the Mach-Zehnder interferometer are through the cores of similar lengths of single mode fiber mode stripped at both input and output. Instantaneous translation of the pattern is proportional to the localized strain produced by ultrasonic bulk waves generated in the disc and integrated along the fiber path. By spatially filtering the moving fringe pattern and synchronously demodulating the filtered optical intensity distirbution, a signal proportional to the integrated strain is obtained.
    Keywords: COMPOSITE MATERIALS
    Type: Va. Polytech. Inst. and State Univ. Opt. Fiber Interferometer for the Study of Ultrasonic Waves in Composite Mater.; p 7-11
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  • 47
    Publication Date: 2011-08-18
    Description: Ultrasonic waves in composite materials using optical fiber waveguide as the detecting device were studied. The possibility of using embedded probes in composites for nondestructive evaluation is discussed. It is found that interferometric system is sensitive but requires accurate optical positioning at both fiber input and output.
    Keywords: COMPOSITE MATERIALS
    Type: Opt. Fiber Interferometer for the Study of Ultrasonic Waves in Composite Mater.; p 2-6
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  • 48
    Publication Date: 2011-08-18
    Description: Instability-related growth of through-width delaminations in laminated coupons was investigated analytically and experimentally. In the analytical effort, a geometrically nonlinear finite-element stress analysis was used, and the numerical results were compared with exact solutions. In addition, measured lateral deflections of postbuckled through-width delaminations were compared with predicted deflections. Lateral deflections, stress distributions, and strain energy release rates were calculated for various delamination lengths, delamination depths, and applied loads. Delamination growth rates observed for unidirectional graphite/epoxy bonded to aluminum were qualitatively correlated with calculated strain-energy release rates and it was found that the Mode I component of energy release dominates the growth process.
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Composite Materials; 15; Sept
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  • 49
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    Publication Date: 2011-08-18
    Description: Micro-area Auger electron spectroscopy with a spatial resolution of less than 50 nm has been used to study the concentration of elements across the reaction zone of a W-reinforced SiC fiber in a titanium matrix. Although the elemental concentrations obtained by this technique are affected by the reaction zone morphology to a greater extent than in the case of X-ray microprobe analysis, the proposed technique has the advantage of a much higher spatial resolution and avoids the problems of bulk averaging that characterize the X-ray technique.
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Materials Science; 16; Nov. 198
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  • 50
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    Publication Date: 2019-06-28
    Description: The intensification of stresses near a through crack in the laminate that suddenly undergoes bending is investigated. A dynamic plate theory is developed which includes the effects of material inhomogeneity in the thickness direction and realistic crack edge stress singularity and distribution. Numerical examples indicate that (1) the crack moment intensity tends to decrease as the crack length to laminate thickness is increased, and (2) the average load intensity transmitted to a through crack can be reduced by making the inner layers to be stiffer than the outer layers.
    Keywords: COMPOSITE MATERIALS
    Type: International Journal of Engineering Science; 19; 7, 19; 1981
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  • 51
    Publication Date: 2019-06-28
    Description: Computerized infrared analysis is applied to the characterization of a glass-reinforced crosslinked polyester. The method of factor analysis determines the number of independent components which constitute the polymeric matrix. Subsequently, the spectra of those components are fitted by a least-squares criterion to spectra of the multicomponent matrix, or, if the glass spectrum is included as an additional component, to the spectra of composites. The least-squares coefficients yield the matrix composition in terms of the initial reactant composition and the extent of crosslinking.
    Keywords: COMPOSITE MATERIALS
    Type: Polymer Composites; 2; Apr. 198
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  • 52
    Publication Date: 2019-06-28
    Description: The sensitivity of the impact characteristics of typical polymeric composite fan blade materials to potential limiting combinations of moisture, temperature level and temperature transients was established. The following four technical tasks are reported: (1) evaluation and characterization of constituent blade materials; (2) ballistic impact tests; (3) leading edge impact protection systems; and (4) simulated blade spin impact tests.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-165211 , R81AEG694
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  • 53
    Publication Date: 2019-06-28
    Description: A liquid injection thrust vector control (LITVC) system for the shuttle solid rocket booster (SRB) was analyzed. The LITVC was compared with the SRB baseline flexible seal. A table of LITVC advantages and disadvantages is presented. It is concluded that the LITVC performs well at low to moderate duty cycles, but not for high duty cycle requirements.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TP-1912 , M-354
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  • 54
    Publication Date: 2019-06-28
    Description: A porous tooling system was selected for the processing of Graphite/PMR-15 Polyimide laminates in thickness up to 3.2 mm. (0.125 inch). This tool system must have a reasonable strength, permeability dimensional stability, and thermal conductivity to accomplish curing at 600 F and 200 psi and 200 psi autoclave temperature and pressure. A permeability measuring apparatus was constructed and permeability vs. casting water level determined to produce tools at three different permeability levels. On these tools, laminates of 5, 11, and 22 plies (.027, .060, and 0.121 inch) were produced and evaluated by ultrasonic, mechanical, and thermal tests to determine the effect of the tool permeability on the cured laminates. All tools produced acceptable laminates at 5 and 11 plies but only the highest permeability produced acceptable clear ultrasonic C-Scans. Recommendations are made for future investigations of design geometry, and strengthening techniques for porous ceramic tooling.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-165633 , SSG-80-0005
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  • 55
    Publication Date: 2019-06-28
    Description: Because of the advantage of the Advanced Expander Cycle Engine brought out in initial studies, further design optimization and comparative analyses were undertaken. The major results and conclusion derived are summarized. The primary areas covered are (1) thrust chamber geometry optimization, (2) expander cycle optimization, (3) alternate low thrust capability, (4) safety and reliability, (5) development risk comparison, and (6) cost comparisons. All of the results obtained were used to baseline the initial design concept for the OTV Advanced Expander Cycle Engine Point Design Study.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-161699 , REPT-32999-F-E1
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  • 56
    Publication Date: 2019-06-28
    Description: A theoretical model was established to predict the fatigue behavior of composite materials, with emphasis placed on predictions of the degradation of residual strength and residual stiffness during fatigue cycling. The model parameters were evaluated from three test series including static strength fatigue life and residual strength tests. The tests were applied to two graphite/epoxy laminates. Load sequence effects were emphasized for both laminates and the predicted results agreed quite well with subsequent verification tests. Dynamic as well as static stiffness reduction data were collected by use of a PDP11-03 computer, which performed quite satisfactorily and permitted the recording of a substantial amount of dynamic stiffness reduction data.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-164065
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  • 57
    Publication Date: 2019-06-28
    Description: The deformation process observed in the hot gas side wall of rocket combustion chambers was investigaged for three different liner materials. Five thrust chambers were cycled to failure by using hydrogen and oxygen as propellants at a chamber pressure of 4.14 MN/cu m. The deformation was observed nondestructively at midlife points and destructively after failure occurred. The cyclic life results are presented with an accompanying discussion about the problems of life prediction associated with the types of failures encountered in the present work. Data indicating the deformation of the thrust chamber liner as cycles are accumulated are presented for each of the test thrust chambers. From these deformation data and observation of the failure sites it is evident that modeling the failure process as classic low cycle thermal fatigue is inadequate as a life prediction method.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TP-1834 , E-553
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  • 58
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-28
    Description: Analytical models to predict performance and operating characteristics of dual nozzle concepts were developed and improved. Aerodynamic models are available to define flow characteristics and bleed requirements for both the dual throat and dual expander concepts. Advanced analytical techniques were utilized to provide quantitative estimates of the bleed flow, boundary layer, and shock effects within dual nozzle engines. Thermal analyses were performed to define cooling requirements for baseline configurations, and special studies of unique dual nozzle cooling problems defined feasible means of achieving adequate cooling.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-161677 , REPT-33553F
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  • 59
    Publication Date: 2019-06-28
    Description: Results of an experimental study of the influence of strain rate, temperature and humidity on the mechanical behavior of a graphite/epoxy fiber composite are presented. Three principal strengths (longitudinal, transverse and shear) and four basic moduli (E1, E2, G12 and U12) of a unidirectional graphite/epoxy composite were followed as a function of strain rate, temperature and humidity. Each test was performed at a constant tensile strain rate in an environmental chamber providing simultaneous temperature and humidity control. Prior to testing, specimens were given a moisture preconditioning treatment at 60 C. Values for the matrix dominated moduli and strength were significantly influenced by both environmental and rate parameters, whereas the fiber dominated moduli were not. However, the longitudinal strength was significantly influenced by temperature and moisture content. A qualitative explanation for these observations is presented.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-81247 , A-8381
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  • 60
    Publication Date: 2019-06-28
    Description: The influence of the coefficient of mutal influence, Poisson's ratio and coefficients of thermal and moisture expansion on delamination is studied. Engineering theories are compared to finite element and experimental results. It is shown that the mismatch in coefficients of mutual influence can have a strong influence on delamination with fiber angles in the 10-15 degree range being critical for adjacent layer combinations. The mismatch in coefficient of mutual influence is reduced by a factor of two and the interlaminar shear stress is reduced significantly when the + or - adjacent layers are interspersed between 0 and 90 degree layers. It is shown how the results can be used for design of composite laminates.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-163956 , VPI-E-81-2 , PB-81-161747
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  • 61
    Publication Date: 2019-06-28
    Description: The primary mode of moisture ingress into bonded composite joints is determined using a nuclear probe for deuterium (NPD) to measure the localized D2O content along the length of the adhesive (FM-300 and EA-9601) and through the thickness of bonded composite speciments. Calculated diffusivities and NPD measured equilibrium moisture contents are used to predict the moisture profiles along the length of the adhesives as a function of exposure time, temperature, and relative humidity. These results are compared with the observed moisture profiles to evaluate the extent of enhanced edge diffusion. The FM-300 adhesive exhibits good agreement between measured and predicted profiles at 49 C, 70% and 90% RH, and 77 C, 70% RH. At 77 C, 90% RH, the measured moisture content near the adhesive edge is substantially larger than the predicted level. The EA-9601 adhesive also shows good agreement at 49 C, 70% and 90% RH, but at 77 C, the concentration of D20 near the edges is enhanced at each humidity level. The effect of moisture content on the bond shear strength at room temperature and at elevated temperature is evaluated.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-3387 , RE-610
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  • 62
    Publication Date: 2019-06-28
    Description: The propagation of the charge-exchange plasma from an electrostatic ion thruster is crucial in determining the interaction of that plasma with the associated spacecraft. A model that describes this plasma and its propagation is described, together with a computer code based on this model. The structure and calling sequence of the code, named PLASIM, is described. An explanation of the program's input and output is included, together with samples of both. The code is written in ASNI Standard FORTRAN.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Exptl. and Anal. Evaluation of Ion Thruster(Spacecraft Interactions; p 73-145
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  • 63
    Publication Date: 2019-06-28
    Description: A model was reviewed which describes the propagation of the mercury charge-exchange plasma and extended to describe the flow of the molybdenum component of the charge-exchange plasma. The uncertainties in the models for various conditions are discussed. Such topics as current drain to the solar array, charge-exchange plasma material deposition, and the effects of space plasma on the charge-exchange plasma propagation are addressed.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: JPL-PUB-79-90 , Exptl. and Anal. Evaluation of Ion Thruster(Spacecraft Interactions; p 29-66
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  • 64
    Publication Date: 2019-06-28
    Description: Studies were conducted to both identify the environment produced by ion thrusters and to assess the interaction of this environment on a typical spacecraft and typical science instruments. Spacecraft charging and the charge exchange that accompanies it is discussed in detail. Electromagnetic interference was characterized for ion engines. The electromagnetic compatibility of ion thrusters with spacecraft instruments was determined. The effects of ion thruster plumes on spacecraft were studied with particular emphasis on external surface currents.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-163975 , JPL-PUB-80-92
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  • 65
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-06-28
    Description: The physical processes governing ion extraction from a plasma have been examined experimentally. The screen hole plasma sheath (the transition region wherein significant ion acceleration and complete electron retardation occurs) has been defined by equipotential plots for a variety of ion accelerator system geometries and operating conditions. It was found that the screen hole plasma sheath extends over a large distance, and influences ion and electron trajectories at least 15 Debye lengths within the discharge chamber. The electron density variation within the screen hole plasma sheath satisfied a Maxwell-Boltzmann density distribution at an effective electron temperature dependent on the discharge plasma primary-to-Maxwellian electron density ratio. Plasma ion flow up to and through the sheath was predominantly one-dimensional, and the ions entered the sheath region with a modified Bohm velocity. Low values of the screen grid thickness to screen hole diameter ratio were found to give good ion focusing and high extracted ion currents because of the effect of screen webbing on ion focusing.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Journal of Applied Physics; 52; Apr. 198
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  • 66
    Publication Date: 2019-06-28
    Description: A rational methodology of modelling both nonlinear and elastic dissipative response of transversely isotropic fibrous composites is developed and illustrated with the aid of the observed response of graphite-polyimide off-axis coupons. The methodology is based on the internal variable formalism employed within the text of classical irreversible thermodynamics and entails extension of Valanis' endochronic theory to transversely isotropic media. Applicability of the theory to prediction of various response characteristics of fibrous composites is illustrated by accurately modelling such often observed phenomena as: stiffening reversible behavior along fiber direction; dissipative response in shear and transverse tension characterized by power-laws with different hardening exponents; permanent strain accumulation; nonlinear unloading and reloading; and stress-interaction effects.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-164747 , VPI-E-81-27 , IR-25
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  • 67
    Publication Date: 2019-06-28
    Description: A non-specular silver-Teflon tape thermal control coating was tested to provide the data necessary to qualify it for use on the Space Shuttle Orbiter radiators. Effects of cure cycle temperature and pressure on optical and mechanical properties on the silver-Teflon tape were evaluated. The baseline Permacel P-223 adhesive, used with the specular silver-Teflon tape initially qualified for the Orbiter radiators, and four alternate metal-filled and unfilled adhesives were evaluated. Tests showed the cure process has no effect on the silver-Teflon optical properties, and that the baseline adhesive cure cycle gives best results. In addition the P-223 adhesive bond is more reproducible than the alternates, and the non-specular tape meets both the mechanical and the optical requirements of the Orbiter radiator coating specification. Existing Orbiter coating techniques were demonstrated to be effective in aplying the non-specular tape to a curved panel simulating the radiators. Author
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-165657
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  • 68
    Publication Date: 2019-06-28
    Description: The compressive behavior of T300/5208 graphite-epoxy laminates containing circular delaminations was studied to determine the flaw criticality of two types of implanted defect, Kapton bag and Teflon film, on several laminate configurations. Defect size was varied. Results, presented in the form of residual strength curves, indicate that the Teflon film defect reduced strength more than the Kapton bad defect in 12-ply samples, but that two laminates (+ or - 45) sub 2s and (90/+ or - 45) sub s were insensitive to any implanted defect. A clear thickness effect was shown to exist for the (o/+ pr 45) sub ns laminate and was attributed to failure mode transition. The analytically predicted buckling loads show excellent agreement with experimental results and are useful in predicting failure mode transition.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-164830 , CCM-81-03
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  • 69
    Publication Date: 2019-06-28
    Description: Optical and scanning electron microscopy were used to investigate the failure morphology of graphite/epoxy specimens which had been tested until tensile failure. Failure morphology was studied as a function of the quality control variables of specimen preparation technique, prepreg batch, and cure condition, and also as a function of the environmental parameters of temperature and moisture content. Defective specimens were found to exhibit a low energy failure morphology. Poor specimen edge preparation and one batch of prepreg when tested at elevated temperature or moisture content also exhibited energy failure morphology. Postcuring had no effect on strength but did slightly alter failure morphology. Temperature or moisture appeared to decrease flaw sensitivity and thus increase strength; however, moisture also appeared to increase interfacial debonding between filament and matrix. When combined moisture and temperature increased interfacial debonding and made the epoxy matrix more prone to fracture.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-81318 , A-8684
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  • 70
    Publication Date: 2019-06-28
    Description: The results of a program designed to determine the extent to which elemental boron and boron containing fillers added to the matrix resin of graphite/epoxy composites prevent the release of graphite fibers when the composites are exposed to fire and impact conditions are described. The fillers evaluated were boron, boron carbide and aluminum boride. The conditions evaluated were laboratory simulations of those that could exist in the event of an aircraft crash and burn situation. The baseline (i.e., unfilled) laminates evaluated were prepared from commercially available graphite/epoxy. The baseline and filled laminates' mechanical properties, before and after isothermal and humidity aging, also were compared. It was found that a small amount of graphite fiber was released from the baseline graphite/epoxy laminates during the burn and impact conditions used in this program. However, the extent to which the fibers were released is not considered a severe enough problem to preclude the use of graphite reinforced composites in civil aircraft structure. It also was found that the addition of boron and boron containing fillers to the resin matrix eliminated this fiber release. Mechanical properties of laminates containing the boron and boron containing fillers were lower than those of the baseline laminates. These property degradations for two systems: boron (5 micron) at 2.5 percent filler loading, and boron (5 micron) at 5.0 percent filler loading do not appear severe enough to preclude their use in structural composite applications.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-165437
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  • 71
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-28
    Description: A sequence of events, occurring over the last 25 years, are described that chronicle the evolution of ion-bombardment electric propulsion technology. Emphasis is placed on the latter phases of this evolution, where special efforts were made to pave the way toward the use of this technology in operational space flight systems. These efforts consisted of a planned program to focus the technology toward its end applications and an organized process that was followed to transfer the technology from the research-technology NASA Center to the user-development NASA Center and its industry team. Major milestones in this evolution, which are described, include the development of thruster technology across a large size range, the successful completion of two space electric rocket tests, SERT I and SERT II, development of power-processing technology for electric propulsion, completion of a program to make the technology ready for flight system development, and finally the technology transfer events.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-82618 , E-870
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  • 72
    Publication Date: 2019-06-28
    Description: The engine requirements are emphasized and include: high specific impulse within a restricted installed length constraint, long life, multiple starts, different thrust levels, and man-rated reliability. The engine operating characteristics and the major component analytical design are summarized.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-161832 , FR-14615-VOL-2
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  • 73
    Publication Date: 2019-06-28
    Description: The engine operating characteristics were examined. Inlet pressure effects, tank pressurization effects, steady-state specific impulse, and the steady-state cycle were studied. The propellant flow schematic and operating sequence are presented. Engine hardware drawings are included.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-161833 , FR-14615-VOL-3
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  • 74
    Publication Date: 2019-06-28
    Description: The objective of the study was to generate the system design of a performance-optimized, advanced LOX/hydrogen expander cycle space engine. The engine requirements are summarized, and the development and operational experience with the expander cycle RL10 engine were reviewed. The engine development program is outlined.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-161831 , FR-14615-VOL-1
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  • 75
    Publication Date: 2019-06-28
    Description: A review of some approximate analytical models for damaged, fiber reinforced composite materials is presented. Using the classical shear lag stress displacement assumption, solutions are presented for a unidirectional laminate containing a notch, a rectangular cut-out, and a circular hole. The models account for longitudinal matrix yielding and splitting as well as transverse matrix yielding and fiber breakage. The constraining influence of a cover sheet on the unidirectional laminate is also modeled.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-3453
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  • 76
    Publication Date: 2019-06-28
    Description: An approximate analysis was developed to analyze the postbuckling behavior of through-width delaminations in a laminated coupon. The analysis contains two parameters which are determined using a finite element analysis. After calculating the parameters for a few configurations, the approximate analysis was used to analyze many other configurations. Lateral deflections and mode I strain-energy release rates obtained with the approximate analysis were compared with results from the finite element analysis. For the configurations analyzed, the approximate analysis agreed very well with the finite element results.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-83147
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  • 77
    Publication Date: 2019-06-28
    Description: Analytical results are presented which predict cumulative plastic deformation characteristic of damage observed in coolant channel walls of regeneratively cooled rocket thrust chambers. The damage consists of bulging and plastic flow which leads to thinout and rupture of the channel wall under the combined effects of high pressures, high temperatures and temperature gradients experienced during cyclic firings of actual test chambers. Analytical predictions correlate with test results.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-165241 , LMSC-HREC-TR-D698400-VOL-2
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  • 78
    Publication Date: 2019-06-28
    Description: The liquid rocket propulsion technology needs to support anticipated future space vehicles were examined including any special action needs to be taken to assure that an industrial base in substained. Propulsion system requirements of Earth-to-orbit vehicles, orbital transfer vehicles, and planetary missions were evaluated. Areas of the fundamental technology program undertaking these needs discussed include: pumps and pump drives; combustion heat transfer; nozzle aerodynamics; low gravity cryogenic fluid management; and component and system life reliability, and maintenance. The primary conclusion is that continued development of the shuttle main engine system to achieve design performance and life should be the highest priority in the rocket engine program.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-164550
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  • 79
    Publication Date: 2019-06-28
    Description: A numerical procedure was developed for minimizing the structural mass of an aircraft structure which must have a specified minimum flutter velocity or divergence velocity. During the optimization process the arrangement of the structural members remains fixed, while the stiffness parameters of the structure are varied.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-164536
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  • 80
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-28
    Description: High char yield epoxy using novel bisimide amines (BIA's) as curing agents with a state of the art epoxy resin was developed. Stoichiometric quantities of the epoxy resin and the BIA's were studied to determine the cure cycle required for preparation of resin specimens. The bisimide cured epoxies were designated IME's (imide modified epoxy). The physical, thermal and mechanical properties of these novel resins were determined. The levels of moisture absorption exhibited by the bisimide amine cured expoxies (IME's) were considerably lower than the state of the art epoxies. The strain-to-failure of the control resin system was improved 25% by replacement of DDS with 6F-DDS. Each BIA containing resin exhibited twice the char yield of the control resin MY 720/DDS. Graphite fiber reinforced control (C) and IME resins were fabricated and characterized. Two of the composite systems showed superior properties compared to the other Celion 6000/IME composite systems and state of the art graphite epoxy systems. The two systems exhibited excellent wet shear and flexural strengths and moduli at 300 and 350 F.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-165229 , R80-914770-12
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  • 81
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-28
    Description: The matrix dominated mechanical behavior of a graphite epoxy composite was found to be affected by sub Tg annealing. Postcured + or - 45 deg 4S specimens of Thornel 300 graphite/Narmco 5208 epoxy were quenched from above Tg and given a sub Tg annealing at 140 C for times up to 10 to the 5th power min. The ultimate tensile strength, strain to break, and toughness of the composite material were found to decrease as functions of sub Tg annealing time. No weight loss was observed during the sub Tg annealing. The time dependent change in mechanical behavior is explained on the basis of free volume changes that are related to the physical aging of the nonequilibrium glassy network epoxy. The results imply possible changes in composite properties with service time.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-81273 , A-8495
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  • 82
    Publication Date: 2019-06-28
    Description: An experimental organic fiber, designated Fiber D, was characterized, and its performance as a reinforcement for composites was investigated. The fiber has a modulus of 172 GPa, tensile strength of 3.14 GPa, and density of 1.46 gm/cu cm. Unidirectional Fiber D/epoxy laminates containing 60 percent fiber by volume were evaluated in flexure, shear, and compression, at room temperature and 121 C in both the as fabricated condition and after humidity aging for 14 days at 95 percent RH and 82 C. A modulus of 94.1 GPa, flexure strength of 700 MPa, shear strength of 54 MPa, and compressive strength of 232 MPa were observed at room temperature. The as-fabricated composites at elevated temperature and humidity aged material at room temperature had properties 1 to 20 percent below these values. Combined humidity aging plus evaluated temperature testing resulted in even lower mechanical properties. Hybrid composite laminates of Fiber D with Fiber FP alumina or Thornel 300 graphite fiber were also evaluated and significant increases in modulus, flexure, and compressive strengths were observed.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-165228 , RSC-3697-6
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  • 83
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-28
    Description: Engine data and information are presented to perform system studies on cargo orbit-transfer vehicles which would deliver large space structures to geosynchronous equatorial orbit. Low-thrust engine performance, weight, and envelope parametric data were established, preliminary design information was generated, and technologies for liquid rocket engines were identified. Two major engine design drivers were considered in the study: cooling and engine cycle options. Both film-cooled and regeneratively cooled engines were evaluated. The propellant combinations studied were hydrogen/oxygen, methane/oxygen, and kerosene/oxygen.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-165276
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  • 84
    Publication Date: 2019-06-28
    Description: A parametric analysis was performed to compare the costs of silicon and gallium arsenide arrays for Earth orbital missions. The missions included electric power in low Earth orbit (LEO), electric power in geosynchronous Earth orbit (GEO), and power for electric propulsion of a LEO to GEO orbit transfer mission. Inputs to the analysis for all missions included launch and purchase costs of the array. For the orbit transfer mission, the launch and purchase costs of the electric propulsion system were added. Radiation flux as a function of altitude and rediation tolerance as a function of cell type were used to determine power degradation for each mission. Curves were generated that show the sensitivity of launch-array cost and total mission cost to a variety of input parameters for each mission. These parameters included mission duration, cover glass thickness, array specific cost, array specific mass, and solar cell efficiency. Solar concentration was considered and the sensitivities of cost to concentration ratio, concentrator costs, and concentrator mass were also evaluated. Results indicate that solar cell development should give a high priority to reducing array costs and that the development of low cost, lightweight, solar concentrators should be pursued.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TP-1811 , E-536
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  • 85
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-28
    Description: A complete definition of the LBM plume is important for many Shuttle design criteria. The exhaust plume shape has a significant effect on the vehicle base pressure. The LBM definition is also important to the Shuttle base heating, aerodynamics and the influence of the exhaust plume on the launch stand and environment. For these reasons a knowledge of the LBM plume characteristics is necessary. A definition of the sea level LBM plume as well as at several points along the Shuttle trajectory to LBM, burnout is presented.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-161646 , LMSC-HREC-TR-D784066
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  • 86
    Publication Date: 2019-06-28
    Description: Inspections of the C-130 composite-reinforced center wings were conducted over the flight service monitoring period of more than six years. Twelve inspections were conducted on each of the two C-130H airplanes having composite reinforced center wing boxes. Each inspection consisted of visual and ultrasonic inspection of the selective boron-epoxy reinforced center wings which included the inspection of the boron-epoxy laminates and the boron-epoxy reinforcement/aluminum structure adhesive bondlines. During the flight service monitoring period, the two C-130H aircraft accumulated more than 10,000 flight hours and no defects were detected in the inspections over this period. The successful performance of the C-130H aircraft with composite-reinforced center wings allowed the transfer of the responsibilities of inspecting and maintaining these two aircraft to the U. S. Air Force.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-165770 , NAS 1.26:165770 , LG81340198
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  • 87
    Publication Date: 2019-06-28
    Description: The mechanical properties of FP-Al2O3 fiber reinforced composites prepared by liquid infiltration techniques are improved. A strengthening addition, magnesium, was incorporated with the aluminum-lithium matrix alloy usually selected for these composites because of its good wetting characteristics. This ternary composite, FP-Al2O3/Al-(2-3)Li-(3-5)Mg, showed improved transverse strength compared with FP-Al2O3/Al-(2-3)Li composites. The lower axial strengths found for the FP-Al2O3/Al-(2-3)Li-(3-5)Mg composites were attributed to fabrication related defects. Another technique was the use of Ti/B coated FP-Al2O3 fibers in the composites. This coating is readily wet by molten aluminum and permitted the use of more conventional aluminum alloys in the composites. However, the anticipated improvements in the axial and transverse strengths were not obtained due to poor bonding between the fiber coating and the matrix. A third approach studied to improve the strengths of FP-Al2O3 reinforced composites was the use of magnesium alloys as matrix materials. While these alloys wet fibers satisfactorily, the result indicated that the magnesium alloy composites used offered no axial strength or modulus advantage over FP-Al2O3/Al-(2-3)Li composites.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-82868 , E-1238 , NAS 1.15:82868 , AVRADCOM-TR-81-C-1
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  • 88
    Publication Date: 2019-06-28
    Description: Priorities for standard compression testing research in advanced laminated fibrous composite materials are presented along with a state of the art survey (completed in 1979) including history and commentary on industrial test methods. Historically apparent research priorities and consequent (lack of) progress are supporting evidence for newly derived priorities.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-165415 , NAS 1.26:165415 , SM-79-25B
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  • 89
    Publication Date: 2019-06-28
    Description: Moire interferometry by reflection has been demonstrated using a real reference grating of 1200 lines/mm. The method is shown to be well adapted to thermal environments. Thermal expansion coefficients of graphite-epoxy composites have been measured with high precision over a wide range from nearly zero to 3300 microstrains in the temperature range 297-422 K. Random errors characterized by one standard deviation can be as small as one microstrain.
    Keywords: COMPOSITE MATERIALS
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  • 90
    Publication Date: 2019-06-28
    Description: The effects of stresses induced by the lamination of off-axis plies to O-deg lamina on the development of damage during the fatigue loading of the O-deg plies are discussed. The transverse normal stresses in the plane of the laminae and the laminate created by the laminating constraints when an axial force is applied to the laminate are calculated in terms of a differential Poisson ratio between the ply in question in the unconstrained and constrained states, and significant differences in the constraint environments of an unnotched specimen joined to plies of 45 and 90 deg inclination are noted which correspond to an increase in longitudinal splitting in the 90 deg case and a marked decrease in longitudinal splitting in the 45 deg case. If a notch is present, shear and crack-opening damage is found to be very effectively suppressed in 45-deg laminates, and less so in the 90-deg case. It is pointed out that whereas the 45-deg laminate represents the least damage situation, it does not have the greatest notched strength. It is concluded that an understanding and prediction of damage development in laminates requires knowledge of the stress fields caused by the lamination constraints.
    Keywords: COMPOSITE MATERIALS
    Type: Composites Technology Review; 3; Spring 1
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  • 91
    Publication Date: 2019-06-28
    Description: The performance of quasisteady multimegawatt MPD thrusters is significantly affected by anode thickness, location, and orifice radius, and by cathode length. Terminal voltage oscillations and electrode erosion are deferred until higher currents by anodes at more downstream locations and of smaller orifice radius and by cathodes of greater length. Without an optimized geometry, specific impulses of 3300 s and thrust efficiencies up to 31% are implied by the best data.
    Keywords: SPACECRAFT PROPULSION AND POWER
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  • 92
    Publication Date: 2019-06-28
    Description: As a consequence of endurance and structural tests performed on 900-series engineering model thrusters (EMT), several modifications in design were found to be necessary for achieving performance goals. The modified thruster is known as the J-series EMT. The most important of the design modifications affect the accelerator grid, gimbal mount, cathode polepiece, and wiring harness. The paper discusses the design modifications incorporated, the condition(s) they corrected, and the characteristics of the modified thruster.
    Keywords: SPACECRAFT PROPULSION AND POWER
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  • 93
    Publication Date: 2019-06-28
    Description: The LeRC/Hughes 30-cm mercury ion thruster has been developed to a state of maturity such that is has become meaningful to formulate models for describing the performance characteristics of the major subassemblies. The thruster hollow cathode and the ion optics subassemblies have been investigated with this objective and conceptual, semiquantitative models have been formulated for relating lifetime and performance capabilities to design and operating parameters. This paper summarizes the investigations, discusses the factors considered for inclusion in the models, and describes the status of the models.
    Keywords: SPACECRAFT PROPULSION AND POWER
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  • 94
    Publication Date: 2019-06-28
    Description: The elevated-temperature mechanical behavior of two aligned eutectics (Ni-8.1 wt % Al-26.4 wt % Mo and Ni-6.3 wt % Al-31.2 wt % Mo) has been investigated utilizing monotonic and cyclic testing in vacuum. Tensile yield strength and fatigue resistance increased from 25 to 725 C, but then were reduced at 825 C. The fatigue lives of specimens tested at 725 C decreased sharply with decreasing frequency. A shift from surface to internal crack initiation was observed upon increasing the test temperature from 725 to 825 C. Stage II crack propagation was observed at both temperatures, in contrast to stage I cracking at 25 C. The test results are compared to those for other nickel and cobalt-base aligned eutectics to show that the frequency effect on fatigue life is not limited to the Ni-Al-Mo system.
    Keywords: COMPOSITE MATERIALS
    Type: Metallurgical Transactions A - Physical Metallurgy and Materials Science; 12A; Nov. 198
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  • 95
    Publication Date: 2019-06-28
    Description: Delamination of composite materials has been investigated with emphasis on the relationship between the engineering properties of the individual layers and edge effects. It is shown that interlaminar shear stresses are primarily a function of the mismatch in coefficients of mutual influence which can be as much as ten times greater than the mismatch in Poisson's ratio. The mismatch in coefficients of mutual influence has a high peak value in the 10-15 deg range for plus or minus theta laminates (where theta is the angle of fiber orientation measured from the axis of the coupon). This mismatch is reduced by a factor of two when the plus or minus theta layers are interspersed between 0 and 90 deg layers. Application of the results to composite design is illustrated by an example.
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Composite Materials; 15; July 198
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  • 96
    Publication Date: 2019-06-28
    Description: Annealing at temperatures below the glass transition temperature (sub-T/g/ annealing) in structural epoxy network glasses is found to affect long-term mechanical properties of symmetrically (+ or - 45 deg) reinforced 16-lamina graphite/epoxy composites. Post-cured specimens of Thornel 300 graphite/Narmco 5208 epoxy are sub-T(g) annealed at 140 C for about 10, 100, 1000, 10,000, and 100,000 min with a prior quenching above T(g). The ultimate tensile strength, strain-to-break, and static toughness of the composite materials are found to decrease as a function of sub-T(g) annealing time, while no weight loss is observed. Time-dependent changes in properties are explained by a physical aging concept based on free-volume decreases in the nonequilibrium glassy state of network epoxies, and results imply that changes in composite properties may occur with the service time.
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Applied Physics; 52; Oct. 198
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  • 97
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    Unknown
    In:  CASI
    Publication Date: 2019-06-28
    Description: The failure of two communication satellites during firing sequence were examined. The correlation/comparison of the circumstances of the Ayame incidents and the failure of the STAR 48 (DM-2) motor are reviewed. The massive nozzle failure of the AKM to determine the impact on spacecraft performance is examined. It is recommended that a closer watch is kept on systems techniques,
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-166735
    Format: application/pdf
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  • 98
    Publication Date: 2019-06-28
    Description: Coated, reinforced carbon-carbon (RCC) is used for the leading edges of the Space Shuttle. The mass loss characteristics of RCC specimens coated with tetra-ethyl-ortho-silicate (TEOS) were determined for conditions which simulated the entry environment expected at the stagnation area of the wing leading edge. Maximum specimen temperature was 1632 K. Specimens were exposed for up to 100 missions. Stress levels up to 8.274 MPa caused an average increase in oxidation of 6 percent over unstressed specimens. Experimentally determined mass losses were compared with those predicted by an existing empirical analysis.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-83203
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  • 99
    Publication Date: 2019-06-28
    Description: The critical evaluation and subsequent redesign of the power conversion subsystem of the spacecraft are covered. As part of that evaluation and redesign, prototype heat pipe components for the heat rejection system were designed fabricated and tested. Based on the results of these tests in conjunction with changing mission requirements and changing energy conversion devices, new system designs were investigated. The initial evaluation and redesign was based on state-of-the-art fabrication and assembly techniques for high temperature liquid metal heat pipes and energy conversion devices. The hardware evaluation demonstrated the validity of several complicated heat pipe geometries and wick structures, including an annular-to-circular transition, bends in the heat pipe, long heat pipe condensers and arterial wicks. Additionally, a heat pipe computer model was developed which describes the end point temperature profile of long radiator heat pipes to within several degrees celsius.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-164878
    Format: application/pdf
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  • 100
    Publication Date: 2019-06-28
    Description: A summary of the design analyses for a liquid rocket injector using oxygen and RP-1 propellants at high chamber pressures of 20,682 kPa (3000 psia) is presented. This analytical investigation includes combustion efficiency versus injector element type, combustion stability, and combustor cooling requirements. The design and fabrication of a subscale injector/acoustic resonantor assembly capable of providing a nominal thrust of 222K N (50,000 lbF) is presented.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-161877 , REPT-33651F
    Format: application/pdf
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