Hypersonic flows over slender circular cones at small angles of attack

This paper presents a perturbation theory for hypersonic flows past pointed-nose slender bodies of revolution at small angles of attack. The theory presents the counter part of other theories on two-dimensional flow, axisymmetric flow, and flow past delta wings, in the case of bodies of revolution. Further restricting the analysis to Newtonian flow, a straightforward perturbation in the angle of attack is applied to the equations obtained and the resulting equations are solved only for circular cones. A striking feature of this approach is the absence of a vortical layer and a uniformally valid solution at body surface and all over the flowfield. In spite of the yaw angle, conical streamlines at cone surface are predicted which bend around towards the leeward plane. Results obtained for the surface pressure and the shock wave of a circular cone compare very well with other approximate calculations and experiment.     

A passive tracking filter for missile capture

A practical filter is suggested for ground-based missile tracking in a capture-guidance mode utilizing angle-only measurements from a passive missile sensor, and its performance is evaluated by a realistic system-simulation study. A missile-acceleration model that provides inputs to the filter is also suggested. The filter has a decoupled structure of independent azimuth and elevation channels, which requires fewer computations in solving the filter gain compared to a coupled structure. Simulation results show good tracking performance of the filter when used in association with the proposed missile-acceleration model     

Low Energy Particles in the Global Heliosphere 2001–2004: 1 to 90 AU

Charged particle instrumentation that will be flying on six spacecraft in the heliosphere between 1 and 90 AU during 2001–2004 will provide a global view of the interplanetary medium that has not heretofore been available. Comparative analyses of the data that will be obtained will provide new understanding of the global evolution of heliospheric features such as traveling shock waves, coronal mass ejections, solar activity-produced particle injections, and anomalous cosmic rays. This revised version was published online in August 2006 with corrections to the Cover Date.     

Dynamics of magnetospheric ion Composition as observed by the GEOS mass spectrometer

After one year of operation the GEOS-1 Ion Composition Experiment has surveyed plasma composition at all local times in the L range 3 8 and the energy per charge range from thermal to 16 keV/e. From measurements made in the keV range during eleven magnetic storms we find that the percentage of heavy (M/Q > 1) ions present in the outer magnetosphere increases by a factor of 3 to 10 during disturbances. We conclude that two independent sources (solar wind, characterized by ⁴He²⁺, and ionosphere, characterized by O⁺) give on the average comparable contributions to injected populations, although in a single event one or the other source may dominate. However, in magnetically quiet periods protons are the dominant species with a few percent of heavy ions. With the help of special satellite manoeuvres magnetic field aligned fluxes of 0.05-3 keV/e H⁺, He⁺, O⁺ with traces of O²⁺ have been observed which may be related to ion beams found previously at lower altitudes in the auroral zone. At still lower energies ( 1 eV/e) the thermal plasma population is found to be made up of six ion species, three of which, D⁺, He²⁺ and O²⁺, were unknown in the magnetosphere prior to the GEOS-1 measurements. We present here a study of the evolution of doubly charged ions and their parent populations over four consecutive days. Various production mechanisms for doubly charged ions are discussed. We argue that ionization of singly charged ions by UV and energetic electrons and protons is the dominant process for plasmasphere production. Furthermore, the observed high concentrations of O²⁺ at high altitudes are a result of production in the upper ionosphere and plasmasphere combined with upward transport by thermal diffusion. Throughout the 1 year lifetime of GEOS-1 the ICE functioned perfectly and, because of its novel design, a short review of technical performance is included here.     

Atmospheric dynamics and bioregenerative technologies in a soil-based ecological life support system: initial results from Biosphere 2.

Biosphere 2 is the first man-made, soil-based, bioregenerative life support system to be developed and tested. The utilization and amendment of local space resources, e.g. martian soil or lunar regolith, for agricultural and other purposes will be necessary if we are to minimize the requirement for Earth materials in the creation of long-term off-planet bases and habitations. Several of the roles soil plays in Biosphere 2 are 1) for air purification 2) as a key component in created wetland systems to recycle human and animal wastes and 3) as nutrient base for a sustainable agricultural cropping program. Initial results from the Biosphere 2 closure experiment are presented. These include the accelerated cycling rates due to small reservoir sizes, strong diurnal and seasonal fluxes in atmospheric CO2, an unexpected and continuing decline in atmospheric oxygen, overall maintenance of low levels of trace gases, recycling of waste waters through biological regeneration systems, and operation of an agriculture designed to provide diverse and nutritionally adequate diets for the crew members.     

Some practical strategies for reducing intermodulation in satellitecommunications

Various heuristic procedures for obtaining practical solutions to the general one-level carrier frequency assignment problem are described. The problem treated is general in the sense that it accommodates the case where L of the N slots may be explicitly designated as prohibited and unavailable for assignment. This problem occurs in satellite transmission with many small carriers accessing the same transponder where, due to multipath and TV interference from crosspolarized transponders of the same satellite and from copolarized transponders of the adjacent satellites, some portions of the bandwidth of the considered transponder cannot be used. To permit comparison with respect to the intermodulation advantage and central-processing-unit time required, the case without prohibited slots is considered. The sequential insertion procedure in which, starting with two carriers at the two end slots, one additional carrier at a time is optimally inserted into one of the unassigned slots is found best when the ratio between the available bandwidth and the total carrier bandwidth is greater than about 125%. All the heuristic procedures produced assignments whose intermodulation advantages are all greater than the bandwidth ratio     

The benefits of using ATE systems in the testing of printed circuitboards

An industry-based pragmatic review is provided of the economic and product-quality consequences of automatic test equipment (ATE) usage in printed circuit board testing. The company selection process, the nature of the industrial participants, and the data collection process are described. The benefits obtained by users are identified. It is demonstrated that the use of ATE systems does result in definable economic and quality-level benefits     

Detection of Projectiles by Electric Field Measurements

A number of various physical mechanisms cause aircraft, missiles, and projectiles to he electrically charged during free flight. The electric charge is in the 10-6 C range for aircraft and in the 10-10 C range for projectiles. The electric field thus transported provides information by which measuring the position and velocity of a projectile is possible. A measuring device is described to determine the position of a projectile in free flight while it is passing a target plane. The electric field distribution is measured by means of three electrodes in the manner of metal plates which are positioned in the proximity of the trajectory of the projectile. A mathematical formula can be derived to describe the coherence between the values measured of the electric field strength and the coordinates of the projectile. This measuring device consists of the target plane, 1 × 1 m2 in size, and the electric device controlled by a microprocessor. The measuring system has been tested with projectiles of the 4-30 mm caliber range and at velocities within the 50-1100 m/s range. The accuracy of the coordinates measured was found to be ± 7.5 mm.     

10. The surface and interior of venus

Present ideas about the surface and interior of Venus are based on data obtained from (1) Earth-based radio and radar: temperature, rotation, shape, and topography; (2) fly-by and orbiting spacecraft: gravity and magnetic fields; and (3) landers: winds, local structure, gamma radiation. Surface features, including large basins, crater-like depressions, and a linear valley, have been recognized from recent ground-based radar images. Pictures of the surface acquired by the USSR's Venera 9 and 10 show abundant boulders and apparent wind erosion.On the Pioneer Venus 1978 Orbiter mission, the radar mapper experiment will determine surface heights, dielectric constant values and small-scale slope values along the sub-orbital track between 50°S and 75°N. This experiment will also estimate the global shape and provide coarse radar images (40–80 km identification resolution) of part of the surface. Gravity data will be obtained by radio tracking. Maps combining radar altimetry with spacecraft and ground-based images will be made. A fluxgate magnetometer will measure the magnetic fields around Venus.The radar and gravity data will provide clues to the level of crustal differentiation and tectonic activity. The magnetometer will determine the field variations accurately. Data from the combined experiments may constrain the dynamo mechanism; if so, a deeper understanding of both Venus and Earth will be gained.