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The study of high speed growth of silicon sheet in inclined-meniscus configurations is discussed. It was concluded that the maximum growth rates in vertical and inclined growth are set by thermal-capillary limits. Also, the melt/crystal interface was determined to be flat. And, vertical growth is qualitatively modelled by one dimensional heat transfer.
The possibility that variable linear polarization in massive X-ray binaries is produced by electron scattering in an asymmetric stellar wind is investigated. The stellar wind is asymmetric because of the gravitational field of the secondary (X-ray source). The degree of asymmetry and the magnitude of the linear polarization are controlled by the degree to which the primary star fills its Roche lobe. For the well-observed X-ray binary Cyg X-1, the present model can produce the correct magnitude for the polarization. Provided that the inclination of the system is less than about 20 deg, the present model should also predict the correct phase dependence of the polarization. Modifications to the model are described which would enable it to apply to systems with higher inclination.
IUE observations of dwarf novae at maximum at quiescence and novalike objects at the high brightness state are analyzed for effects of the inclination angle on the emitted continuum and line radiation. A clear pattern in the continuum flux distribution is exhibited only by dwarf novae at maximum where some 80 percent of the non-double-eclipsing systems show essentially identical distributions. This result is not in disagreement with theoretical expectations. All classes of objects exhibit a clear, but in each case different, dependence of the line radiation on the inclination angle.
We analyze the Kitt Peak magnetograms and find that the distribution function of magnetic field strengths is given by a power law, with an index that depends on the mean absolute magnetic flux. We also find that weak (measured) magnetic fields - but not strong ones - are significantly inclined to the vertical. We argue that this inclination is produced by convective motions at the top of the convection zone.
An experimental investigation was conducted to determine the aerodynamic characteristics of a store as it was separated from the lee side of a flat plate inclined at 15 deg to the free-stream flow at Mach 6. Two store models were tested: a cone cylinder and a roof delta. Force and moment data were obtained for both stores as they were moved in 0.5-in. increments away from the flat plate lee-side separated flow region into the free-stream flow while the store angle of attack was held constant at either 0 deg or 15 deg. The results indicate that both stores had adverse separation characteristics (i.e., negative normal force and pitching moment) at an angle of attack of 0 deg, and the cone cylinder had favorable separation characteristics (i.e., positive normal force and pitching moment) at an angle of attack of 15 deg. At an angle of attack of 15 deg, the separation characteristics of the roof delta are indeterminate at small separation distances and favorable at greater separation distances. These characteristics are the result of the local flow inclination relative to the stores as they traversed through the flat plate lee-side flow field. In addition to plotted data, force and moment data are tabulated and schlieren photographs of the stores and flat plate are presented.
The shear-sensitive liquid crystal coating (SSLCC) method is an image-based technique for both visualizing dynamic surface-flow phenomena, such as transition and separation, and for measuring the continuous shear-stress vector distribution acting on an aerodynamic surface. Under proper lighting and viewing conditions (discussed below), the coating changes color in response to an applied aerodynamic shear. This color-change response is continuous and reversible, with a response time of milliseconds, and is a function of both the shear magnitude and the shear vector orientation relative to the observer. The liquid crystal phase of matter is a weakly-ordered, viscous, non-Newtonian fluid state that exists between the nonuniform liquid phase and the ordered solid phase of certain organic compounds. Cholesteric liquid crystal compounds possess a helical molecular arrangement that selectively scatters white light, incident along the helical axis, as a three-dimensional spectrum. This property is linked to the helical pitch length, which is within the range of wavelengths in the visible spectrum. The pitch length, and hence the wavelength of the scattered light, is influenced by shear stress normal to the helical axis. This unique optical property produces a measurable color change in response to an applied shearing force. The full-surface shear stress vector measurement method, developed at NASA-Ames, is schematically illustrated. As with the visualization method, the coated test surface is illuminated from the normal direction with white light and the camera is positioned at an above-plane view angle of approximately 30 deg. Experiments have been initiated at NASA Ames to begin the process of quantifying surface-inclination (surface-curvature) effects on shear vector measurement accuracy. In preliminary experiments, surface-inclination angles theta(sub x), theta(sub y) of 0, +/-5, +/-10, and +/-15 deg were employed. In this arrangement, white-light illumination was positioned normal to the untilted test surface, and the camera above-plane view angle was set at 30 deg relative to the untilted test surface. As can be seen, vector-aligned lambda(sub d) values showed no dependence on theta(sub x) or theta(sub y) for absolute values of these tilt angles is less than or equal to 15 deg. Acquisition and analyses of full-surface color images are presently underway to definitively document the insensitivity limits of the shear vector measurement methodology to surface-slope variations.
The evolution of low-thrust propulsion technologies has reached a point where such systems have become an economical option for many space missions. The development of efficient, low trip time control laws has received an increasing amount of attention in recent years, though few studies have examined the subject of inclination changing maneuvers in detail. A method for performing economical inclination changes through the use of an efficiency factor is derived front Lagrange's planetary equations. The efficiency factor can be used to regulate propellant expenditure at the expense of trip time. Such a method can be used for discontinuous-thrust transfers that offer reduced propellant masses and trip-times in comparison to continuous thrust transfers, while utilizing thrusters that operate at a lower specific impulse. Performance comparisons of transfers utilizing this approach with continuous-thrust transfers are generated through trajectory simulation and are presented in this paper.
It has been shown that the circumferential pressure distributions for the inclined body and circular cylinder deviate from their respective theoretical inviscid distributions on the lee or downstream side in the same manner. With the aid of visual flow techniques, it has been shown that there is a shedding of vortices within the crossflow field of the inclined body. It has also been found that the vortex configuration depoends to a large extent on the shape of the nose of the body. To illustrate this, vapor screen pictures were made and results are discussed.
A method for calculating the induced velocities at the blades of an inclined propeller is presented. The calculations are based upon an assumed wake consisting of one skewed helical vortex per blade. The blade circulation is assumed constant with respect to both radial and azimuth positions. The restriction of uniform radial circulation can be removed by superposition; however, the assumption of constant azimuth-wise circulation restricts the analysis to small propeller inclinations. Numerical values have been obtained for one wake skew angle. These values indicate large effects due to wake vortex spacing and to the number of blades.
Two theoretical procedures are developed for designing asymmetric supersonic nozzles for which the calculated exit flow is nearly uniform over a range of Mach numbers. One procedure is applicable at Mach numbers less than approximately 3. This approach yields, without iteration, a nozzle for which the calculated exit flow is uniform at two Mach numbers and, with proper design, is nearly uniform at Mach numbers between, slightly above, and slightly below these two. The use of an inclined and curved sonic line is an essential feature of this approach, The second procedure requires iteration and is used far designs at Mach numbers exceeding 3. Although it is not a necessary feature, an inclined and curved sonic line is also used in this procedure. In both approaches the flow field dawn stream of the sonic line is determined using the method of characteristics.
The Advanced Communications Technology Satellite (ACTS) system has been modified to support operation in an inclined orbit that is virtually transparent to users, and plans are to continue this final phase of its operation through September 2000. The next 2 years of ACTS will provide a new opportunity for using the technologies that this system brought online over 5 years ago and that are still being used to resolve the technical issues that face NASA and the satellite industry in the area of seamless networking and interoperability with terrestrial systems. New goals for ACTS have been defined that align the program with recent changes in NASA and industry. ACTS will be used as a testbed to: Show how NASA and other Government agencies can use commercial systems for 1. future support of their operations Test, characterize, and resolve technical issues in using advanced communications 2. protocols such as asynchronous transfer mode (ATM) and transmission control protocol/Internet protocol (TCP/IP) over long latency links as found when interoperating satellites with terrestrial systems Evaluate narrow-spot-beam Ka-band satellite operation in an inclined orbit 3. Verify Ka-band satellite technologies since no other Ka-band system is yet 4. available in the United States
During the Fall 2006 inclination campaign for the Aqua spacecraft it was discovered that there was significant uncertainty in the prediction of the semimajor axis change during a maneuver. The low atmospheric drag environment at the time of the maneuvers amplified the effects of this uncertainty leading to a potential violation of the spacecraft ground-track requirements. In order to understand the uncertainty, a Monte Carlo simulation was developed to characterize the expected semi-major axis change uncertainty given the observed behavior of the spacecraft propulsion and attitude control systems during a maneuver. This expected uncertainty was then used to develop new analysis tools to ensure that future inclination maneuver plans will .meet ground-track control requirements in the presence of the error.
Phase II data results of the Fundamental Inlet Bleed Experiments study at NASA Glenn Research Center are presented which include flow coefficient behavior for 21 bleed hole configurations. The bleed configurations are all round holes with hole diameters ranging from 0.795 to 6.35 mm, hole inclination angles from 20deg to 90deg, and thickness-to-diameter ratios from 0.25 to 2.0. All configurations were tested at a unit Reynolds number of 2.46 10(exp 7)/m and at discrete local Mach numbers of 1.33, 1.62, 1.98, 2.46, and 2.92. Interactions between the design parameters of hole diameter, hole inclination angle, and thickness-to-diameter as well as the interactions between the flow parameters of pressure ratio and Mach number upon the flow coefficient are examined, and a preliminary statistical model is proposed. An existing correlation is also examined with respect to this data.
We introduce and discuss two approaches to presenting assurance arguments. One approach is based on a monograph structure, while the other is based on a tabular structure. In today's research and academic setting, assurance cases often use a graphical notation; however for people who are not graphically inclined, these notations can be difficult to read. This document proposes, outlines, explains, and presents examples of two non-graphical assurance argument notations that may be appropriate for non-graphically-inclined readers and also provide argument writers with freedom to add details and manipulate an argument in multiple ways.
This presentation will discuss the results of an investigation looking into the physical causes of the observed annual variations in Aqua's mean local time and inclination. This provides a deeper insight into the forces driving Aqua's orbit. It was found that the Sun and the Moon's gravitational effects combine to cause Aqua's inclination rate to vary, peaking around December of each year, and reaching a minimum around August of each year.
Our current understanding of the Sun, its atmosphere, and the heliosphere is severely limited by a lack of good observations of the Sun’s polar regions. A High Inclination Solar Mission (HISM) mission would go into a 0.48-AU circular solar orbit with at least a 60° inclination to conduct long-term observations of the Sun’s poles using both situ and remote-sensing instruments to study the connections between the Sun, the solar wind, and solar energetic particle events. The propulsion requirements to implement HISM are beyond the capability of conventional chemical propulsion and extremely challenging even for highly efficient solar electric propulsion. To enable HISM and a host of other propulsion-intense space science missions, NASA is actively developing solar sail propulsion, capable of continuous low thrust for the extended periods of time required to meet the delta V requirements of HISM. Upcoming solar sail missions include the Near Earth Asteroid (NEA) Scout (2021 planned launch) and Solar Cruiser (candidate for flight in 2024).Solar sails use sunlight to propel vehicles through space by reflecting solar photons from a large, highly-reflective sail. This continuous photon pressure provides propellantless thrust, allowing for very high delta V maneuvers on long-duration, deep-space exploration. Since the Sun supplies the necessary propulsive energy, solar sails require no onboard propellant, thereby potentially increasing useful payload mass. The NASA MSFC Advanced Concepts Office recently completed a detailed mission concept study of HISM based on the solar sail propulsion technologies being developed for NEA Scout and Solar Cruiser. The HISM spacecraft concept envisions carrying a Doppler & Stokes Imager, a coronagraph, magnetometer, Faraday Cup, a plasma spectrometer, and a radio and plasma wave package to meet the science objectives established for a solar polar orbiting mission in the Heliophysics Decadal Survey. This paper will describe the mission concept and its solar sail propulsion system
A hypothesis for the low inclination of the orbits of the Martian moons following capture is presented, in which the inclination is reduced by the cumulative effect of ejection and re-accretion of material from the surfaces.
A distant, massive planet in the outer solar system has recently been proposed to explain some observed features of extreme trans-Neptunian objects (TNOs). Here we use N-body simulations of the formation of the Kuiper Belt and Oort cloud as well as a survey simulator to compare models of the solar system with and without a ninth planet to one another as well as to observations. The main mechanism for TNOs to be deposited into the distant (a > 50 au), detached (q > 40 au) region of the Kuiper Belt in the eight-planet model is Kozai–Lidov oscillation of objects in mean motion resonances (MMR) with Neptune. This effect does not deposit low-inclination (i ≲ 20°) objects into this region. However, we find that the ninth planet generates a group of distant, detached TNOs at low inclinations that are not present in the eight-planet model. This disparity between the eight-planet and nine-planet models could provide a strong constraint on a possible planet nine with further detections of TNOs in the distant, detached region of the Kuiper Belt.