MLS: a total system approach

A typical approach and landing operation is described. The microwave landing system (MLS) is then examined, its design characteristics and how it works are shown, and how the MLS design fulfils the user's operational requirements by protecting the guidance signal from reflected signal interference is highlighted. MLS angle system accuracy is discussed in great detail, and its reliability, integrity, and coverage volume are briefly considered. MLS availability at any runway to all aircraft types and their landing scenarios, which is accomplished using narrow scanning beam antennas, is examined     

The role of repair in the survival of mammalian cells from heavy ion irradiation: approximation to the ideal case of target theory.

Theories of cellular radiation sensitivity that preclude a significant role for cellular repair processes in the final biological expression of cellular damage induced by ionizing radiation are unsound. Experiments are discussed here in which the cell-cycle dependency of the repair deficiency of the S/S variant, of the L5178Y murine leukemic lymphoblast was examined by treatment with the heavy ions, 20Ne, 28Si, 40Ar, 56Fe and 93Nb. Evidence from those studies, which will be described in detail elsewhere, provide support for the notion that as the linear energy transfer (LET infinity) of the incident radiation increases the ability of the S/S cell to repair radiation damage decreases until effectively it is eliminated around 500 keV/micrometer. In the region of the latter LET infinity value, the behavior of the S/S cell approximates the ideal case of target theory where post-irradiation metabolism (repair) does not influence cell survival. The expression of this phenomenon among different cell types and tissues will depend upon the actual repair systems involved and other considerations.     

Stationary Motions of a Homogeneous Meteor Ring in the Gravitational Field of a Center

The problem of studying a ring in the gravitational field of a center arose after the discovery of Saturn's rings by Galileo and subsequent discovery of the rings of other planets of the Solar System. Modern theoretical investigations of the existence and stability of planetary rings are mostly related to studies of plane differentially rotating discs [1]. As opposed to this line of research, this paper follows the approach established in classical works [2–4].     

Pilots for space tourism

This article sheds light on the key player needed for any space tourism adventure: the pilot who flies the spacecraft. The paper addresses the potential benefits of including a pilot at the controls when designing a space tourism spacecraft. It examines the basic qualifications and advanced skills required of space tourism pilots and discusses key training requirements for selected pilots and space pilots' pay and benefits. In addition, the research concludes that, just as the pioneers of passenger transport in aviation entertained and captured the interest of their passengers, the space pilot should have the skills of a tour guide.     

Mercury’s Weather-Beaten Surface: Understanding Mercury in the Context of Lunar and Asteroidal Space Weathering Studies

Mercury’s regolith, derived from the crustal bedrock, has been altered by a set of space weathering processes. Before we can interpret crustal composition, it is necessary to understand the nature of these surface alterations. The processes that space weather the surface are the same as those that form Mercury’s exosphere (micrometeoroid flux and solar wind interactions) and are moderated by the local space environment and the presence of a global magnetic field. To comprehend how space weathering acts on Mercury’s regolith, an understanding is needed of how contributing processes act as an interactive system. As no direct information (e.g., from returned samples) is available about how the system of space weathering affects Mercury’s regolith, we use as a basis for comparison the current understanding of these same processes on lunar and asteroidal regoliths as well as laboratory simulations. These comparisons suggest that Mercury’s regolith is overturned more frequently (though the characteristic surface time for a grain is unknown even relative to the lunar case), more than an order of magnitude more melt and vapor per unit time and unit area is produced by impact processes than on the Moon (creating a higher glass content via grain coatings and agglutinates), the degree of surface irradiation is comparable to or greater than that on the Moon, and photon irradiation is up to an order of magnitude greater (creating amorphous grain rims, chemically reducing the upper layers of grains to produce nanometer-scale particles of metallic iron, and depleting surface grains in volatile elements and alkali metals). The processes that chemically reduce the surface and produce nanometer-scale particles on Mercury are suggested to be more effective than similar processes on the Moon. Estimated abundances of nanometer-scale particles can account for Mercury’s dark surface relative to that of the Moon without requiring macroscopic grains of opaque minerals. The presence of nanometer-scale particles may also account for Mercury’s relatively featureless visible–near-infrared reflectance spectra. Characteristics of material returned from asteroid 25143 Itokawa demonstrate that this nanometer-scale material need not be pure iron, raising the possibility that the nanometer-scale material on Mercury may have a composition different from iron metal [such as (Fe,Mg)S]. The expected depletion of volatiles and particularly alkali metals from solar-wind interaction processes are inconsistent with the detection of sodium, potassium, and sulfur within the regolith. One plausible explanation invokes a larger fine fraction (grain size <45 μm) and more radiation-damaged grains than in the lunar surface material to create a regolith that is a more efficient reservoir for these volatiles. By this view the volatile elements detected are present not only within the grain structures, but also as adsorbates within the regolith and deposits on the surfaces of the regolith grains. The comparisons with findings from the Moon and asteroids provide a basis for predicting how compositional modifications induced by space weathering have affected Mercury’s surface composition.     

Propagating MHD Waves in Coronal Holes

Coronal holes are the coolest and darkest regions of the upper solar atmosphere, as observed both on the solar disk and above the solar limb. Coronal holes are associated with rapidly expanding open magnetic fields and the acceleration of the high-speed solar wind. During the years of the solar minima, coronal holes are generally confined to the Sun??s polar regions, while at solar maxima they can also be found at lower latitudes. Waves, observed via remote sensing and detected in-situ in the wind streams, are most likely responsible for the wind and several theoretical models describe the role of MHD waves in the acceleration of the fast solar wind. This paper reviews the observational evidences of detection of propagating waves in these regions. The characteristics of the waves, like periodicities, amplitude, speed provide input parameters and also act as constraints on theoretical models of coronal heating and solar wind acceleration.     

Optimum parameters of a gravitational satellite-stabilizer system

Dynamics of a satellite-stabilizer system is studied. It is supposed that there is a viscous friction in a hinge connecting two bodies, but there is no elasticity. The attitude motion in a plane of circular orbit is considered, and parameters are determined, at which natural oscillations near a stable equilibrium position in the orbital coordinate system are damped out most rapidly. The rate of transient processes is estimated by a value of the degree of stability of linearized equations of motion. The optimization of the degree of stability is sequentially performed in dimensionless damping coefficient (the first stage) and in inertial system parameters (the second stage). The result of the first stage is the partition of system parameter space into the regions, in each of which the maximum of the degree of stability is reached on a particular configuration of roots of the characteristic equation. It is shown at the second stage that the global maximum is reached at two points of parameter space, where one of system bodies degenerates into a plate, and the characteristic equation has four equal real roots.