Alfven wave refraction by interplanetary inhomogeneities

Pioneer 6 magnetic data reveals that the propagation direction of Alfven waves in the interplanetary medium is strongly oriented along the ambient field. Magnetic fluctuations of frequencies up to 1/30 sec in the spacecraft frame are shown to satisfy a necessary condition for Alfven wave normal. It appears from this analysis that geometrical hydromagnetics may satisfactorily describe deviation of the wave normal from the background field. The rotational discontinuity is likely also to propagate along the field lines

Force and cavitation characteristics of the NACA 4412 hydrofoil

This report covers Water Tunnel measurements of the infinite aspect ratio characteristics and cavitation characteristics of a hydrofoil section. The profile tested is identical to the 4412 airfoil section of the National Advisory Committee for Aeronautics and is called the NACA 4412 hydrofoil in this report. Measurements and observations include lift, drag, and pitching moment and the inception and development of cavitation as functions of the angle of attack, velocity, and pressure of the flow. The purpose of this report is to present these measurements of the characteristics of this section in water, to compare the results with other available information on this shape, and to evaluate the Water Tunnel method for obtaining the complte hydrodynamic characteristics of hydrofoils

Iron abundance and magnetic permeability of the moon

A larger set of simultaneous data from the Apollo 12 lunar surface magnetometer and the Explorer 35 Ames magnetometer are used to construct a whole-moon hysteresis curve, from which a new value of global lunar permeability is determined to be mu = 1.012 + or - 0.006. The corresponding global induced dipole moment is 2.1 x 10 to the 18th power gauss-cu cm for typical inducing fields of .0001 gauss in the lunar environment. From the permeability measurement, lunar free iron abundance is determined to be 2.5 + or - 2.0 wt. %. Total iron abundance (sum of iron in the ferromagnetic and paramagnetic states) is calculated for two assumed compositional models of the lunar interior: a free iron/orthopyroxene lunar composition and a free iron/olivine composition. The overall lunar total iron abundance is determined to be 9.0 + or - 4.7 wt. %. Other lunar models with a small iron core and with a shallow iron-rich layer are discussed in light of the measured global permeability

Magnetism and the interior of the moon

The application of lunar magnetic field measurements to the study of properties of the lunar crust and deep interior is reviewed. Following a brief description of lunar magnetometers and the lunar magnetic environment, measurements of lunar remanent fields and their interaction with the solar plasma are discussed. The magnetization induction mode is considered with reference to lunar magnetic permeability and iron abundance calculations. Finally, electrical conductivity and temperature calculations from analyses of poloidal induction, for data taken in both the solar wind and in the geomagnetic tail, are reviewed

Lunar electrical conductivity, permeability,and temperature from Apollo magnetometer experiments

Magnetometers were deployed at four Apollo sites on the moon to measure remanent and induced lunar magnetic fields. Measurements from this network of instruments were used to calculate the electrical conductivity, temperature, magnetic permeability, and iron abundance of the lunar interior. Global lunar fields due to eddy currents, induced in the lunar interior by magnetic transients, were analyzed to calculate and electrical conductivity profile for the moon, and those profiles were used to calculate the lunar temperature for an assumed lunar material of olivine. Simultaneous measurements by magnetometers on the lunar surface and in orbit around the moon were use to construct a whole-moon hysteresis curve, from which the global lunar magnetic permeability is determined. Total iron abundance (sum of iron in the ferromagnetic and paramagnetic states) was calculated for two assumed compositional models of the lunar interior. Other lunar models with an iron core and with a shallow iron-rich layer also discussed in light of the measured global lunar permeability. Simultaneous magnetic field and solar plasma pressure measurements show that the remanent fields at the Apollo 12 and 16 sites interact with, and are compressed by, the solar wind. Velocities and thicknesses of the earth's magnetopause and bow shock were also estimated from simultaneous magnetometer measurements

Temperature and electrical conductivity of the lunar interior from magnetic transient measurements in the geomagnetic tail

Magnetometers were deployed at four Apollo sites on the moon to measure remanent and induced lunar magnetic fields. Measurements from this network of instruments were used to calculate the electrical conductivity, temperature, magnetic permeability, and iron abundance of the lunar interior. Global lunar fields due to eddy currents, induced in the lunar interior by magnetic transients in the geomagnetic tail field, were analyzed to calculate an electrical conductivity profile for the moon: the conductivity increases rapidly with depth from 10 to the minus 9 power mhos/meter at the lunar surface to .0001 mhos/meter at 200 km depth, then less rapidly to .02 mhos/meter at 1000 km depth. A temperature profile is calculated from conductivity: temperature rises rapidly with depth to 1100 K at 200 km depth, then less rapidly to 1800 K at 1000 km depth. Velocities and thicknesses of the earth's magnetopause and bow shock are estimated from simultaneous magnetometer measurements. Average speeds are determined to be about 50 km/sec for the magnetopause and 70 km/sec for the bow shock, although there are large variations in the measurements for any particular boundary crossing

Iron abundance in the moon from magnetometer measurements

Apollo 12 and 15 lunar surface magnetometer data with simultaneous lunar orbiting Explorer 35 data are used to plot hysteresis curves for the whole moon. From these curves a whole-moon permeability mu = 1.029 + 0.024 or - 0.019 is calculated. This result implies that the moon is not composed entirely of paramagnetic material, but that ferromagnetic material such as free iron exists in sufficient amounts to dominate the bulk lunar susceptibility. From the magnetic data the ferromagnetic free iron abundance is calculated. Then for assumed compositional models of the moon the additional paramagnetic iron is determined, yielding total lunar iron content. The calculated abundances are as follows: ferromagnetic free iron = 5 + or - 4 wt. percent, and total iron in the moon = 9 + or - 4 wt. percent

Crustal evolution inferred from Apollo magnetic measurements

Magnetic field and solar wind plasma density measurements were analyzed to determine the scale size characteristics of remanent fields at the Apollo 12, 15, and 16 landing sites. Theoretical model calculations of the field-plasma interaction, involving diffusion of the remanent field into the solar plasma, were compared to the data. The information provided by all these experiments shows that remanent fields over most of the lunar surface are characterized by spatial variations as small as a few kilometers. Large regions (50 to 100 km) of the lunar crust were probably uniformly magnetized during early crustal evolution. Bombardment and subsequent gardening of the upper layers of these magnetized regions left randomly oriented, smaller scale (5 to 10 km) magnetic sources close to the surface. The larger scale size fields of magnitude approximately 0.1 gammas are measured by the orbiting subsatellite experiments and the small scale sized remanent fields of magnitude approximately 100 gammas are measured by the surface experiments

Cavitation Characteristics and Infinite Aspect Ratio Characteristics of a Hydrofoil Section

This paper describes "two-dimensional" tests in a water tunnel of a profile identical to the 4412 airfoil section of the National Advisory Committee for Aeronautics. The tests included photographic observations of the inception and growth of cavitation as influenced by velocity, pressure (submergence) and angle of attack, and measurements, during cavitation-free operation, of the hydrodynamic forces and moments as functions of Reynolds number and angle of attack. The relation between the angle of attack and the value of the cavitation parameter at which inception occurs is shown for each face of the hydrofoil. The effect of profile geometry in causing cavitation, and the significance of distinct~y different types of cavitation obtained with change in variables are discussed. Convenient curves are given showing the submergence required to avoid cavitation for different velocities and angles of attack. The measured hydrodynamic characteristics are presented in graphical form and are also compared with previously existing data from wind tunnel tests of a finite aspect ratio span. The experimental procedure and its reliability in indicating true infinite aspect ratio characteristics is discussed

Water Tunnel Tests of the 2 1/4" AA Rocket Projectile

The High Speed Water Tunnel is operated by the California Institute of Technology under Contract OEMsr-207 with the Office of Scientific Research and Development, and is sponsored by Division Six, Section 6.1, of the National Defense Research Committee. The report covers Water Tunnel tests of 1 - 1/2 " and 2" diameter models of the 2-1/4" AA Rocket Projectile. The drag, cross force, and moment acting on the models were measured and the position of the center of pressure relative to the center of gravity was calculated for various yaw angles. These results were compared with prototype field test data. The main findings are summarized as follows: i. The rocket is statically stable as indicated by a stabilizing moment coefficient and a center-of-pressure eccentricity of more than 0.26. Furthermore, the large area of 1he tail fins will probably provide sufficient damping to make it dynamically stable also. 2. The tail fins cause very large cross force coefficients compared to values for other cylindrical projectiles with folding fin or ring tails. Consequently, unless the rocket is rotated in flight, small misalignments of the tail fins can cause drifting and increase the dispersion seriously . 3. Both the cross force and moment coefficients increase with yaw at a greater than linear rate. 4. Comparison of Water Tunnel and field test data shows good agreement for the moment coefficient 5. The drag coefficient from Water Tunnel tests is 9% lower than the value of 0.46 measured during field tests in air. Scale effects, oscillation of the projectile during free flight tests, and compressibility effects on the drag in air are factors that could account for this difference. 6. The drag is nearly independent of yaw for small angles and increases rapidly for angles greater than about 4°. 7. The high drag coefficient for this projectile is caused by skin friction on the relatively large area of the body and fins and by pressure drag due primarily to a large eddying wake behind the blunt body