Transition radiation mechanism for broad-band component of stimulated electromagnetic emission

As is well known in the F-region of the ionosphere modified by high power HF radio waves broad-band electromagnetic stimulated emission (SEE) is observed. It was discovered both the beams of superthermal electrons and intensive small-scale irregularities in modified region. These magnetic field aligned irregularities have caviton shape — deep electron density holes. The presence of such irregularities and superthermal electrons create conditions for generation of transition emission. We consider this radiation mechanism for interpretation the SEE broad-band component.     

Future fighter fable: a day in the life of a future fighter-how dowe get there from here?

The intent of this tongue-in-cheek paper is to stimulate thought about technologies that may be included in future weapons systems and how the weapon system developer is impacted today. It explores a day in the life of a future generation fighter aircraft (year 2015-2025 time-frame). The scenario starts from the perspective of the ground crew awaiting the return of their future fighters: the new A/F-2, “Thunderchief II”-to a dispersed operations location (DOL) from a combat air patrol (CAP) mission in the fictitious country of Crad. A nonrestrictive technology view is assumed, tempered with as much realism as one can logically include in the scenario, with some of today's evolving technology thrusts     

Realistic computerized human phantoms.

To estimate the risk resulting from exposures to ionizing radiation, the organ and tissue doses should be assessed. A convenient method is the calculation of these doses using representations of the human body, called models or phantoms, together with computer codes simulating the transport of radiation in the body. Most commonly used are mathematical phantoms whose external and internal volumes are defined by simple geometric bodies. More recently, phantoms constructed from computed tomographic data of real persons were introduced as an improvement. These phantoms present advantages concerning the location and shape of the organs, in particular the hard bone and bone marrow, whose distribution can be assessed with high resolution. So far, three of these phantoms were constructed at the GSF, a fourth is under process. The construction technique is described, and some calculational results of organ doses due to external photon irradiation are presented.     

Changes of cell-vascular complex in zones of adaptive remodeling of the bone tissue under microgravity conditions.

We examined the peculiarities of the structure of the blood-vascular bed and perivascular cells in zones of osteogenesis in the epiphyses and metaphises of femoral bones of rats, flown aboard the US laboratory SLS-2 for two weeks by electron microscopy and histochemistry. In zones of bone remodeling, there was a tendency for a reduction of sinusoid capillary specific volume. Endotheliocytes preserve the typical structure. In the population of perivascular cells, we discovered differentiating osteogenic cells that contained alkaline phosphomonoesterase as well as cells that don't contain this enzyme and differentiate into fibroblasts. The fibroblasts genesis in zones of adaptive remodeling of spongy bones leads to a further development of fibrous tissue that is not subject to mineralization.     

Systems of Gyrodynes with an Additional Degree of Freedom

The systems of gyrodynes installed on a spacecraft body on the one-axis controlled platform are considered. An algorithm to determine the special states and the special surfaces corresponding to them in the region of variation of the total angular momentum is obtained, as well as an algorithm to study the permeability of special surfaces. The results of calculation of the special surfaces for two types of gyro systems are presented.     

Anti-aircraft artillery simulator

Air defense systems protect land and maritime resources from air attack. Depending on the regional characteristics and type of conflicting forces, air defense threats vary considerably. In regional conflicts, where forces with similar capabilities are involved and no air-superiority can be achieved, the role of air defense systems becomes critical. In combat terrains containing mountains (in mainland or in small islands), the man-operated or computer-controlled (using passive sensors) anti-aircraft artillery can be highly effective. The simulator presented in this work aims to exploit the capabilities provided by current commercial-off-the-shelf (COTS) communication and multimedia technologies for providing a training environment that improves the personnel capability for effective use of man-controlled anti-aircraft weapons.     

Dynamic Modeling of Brushless dc Motors for Aerospace Actuation

A discrete time model for simulation of the dynamics of samarium cobalt-type permanent magnet brushless dc machines is presented. The similation model includes modeling of the interaction between these machines and their attached power conditioners. These are transistorized conditioner units. This model is part of an overall discrete-time analysis of the dynamic performance of electromechanical actuators, which was conducted as part of prototype development of such actuators studied and built for NASA-Johnson Space Center as a prospective alternative to hydraulic actuators presently used in shuttle orbiter applications. The resulting numerical simulations of the various machine and power conditioner current and voltage waveforms gave excellent correlation to the actual waveforms collected from actual hardware experimental testing. These results, numerical and experimental, are presented here for machine motoring, regeneration and dynamic braking modes. Application of the resulting model to the determination of machine current and torque profiles during closed-loop actuator operation were also analyzed and the results are given here. These results are given in light of an overall view of the actuator system components. The applicability of this method of analysis to design optimization and trouble-shooting in such prototype development is also discussed in light of the results at hand.     

Needs in space education for the 21st century

There is increasingly broad concern in the USA today about the quality, vibrancy and appeal of science and technical education in general and space education in particular. There needs to be a robust link between the educational community (i.e. the primary and secondary schools as well as colleges and universities) and a well-defined space research and exploration agenda that is strongly supported by the space industry, NASA and other relevant US governmental agencies. Without such a renewal of mission and new goals it will be difficult to re-invigorate and expand quality space education programs. A workshop was therefore convened in 2003 to analyze the problem, discuss new initiatives, organize a survey inviting suggestions from a range of relevant players and draw conclusions on what the USA needs to do to improve space education in the 21st century. Although the focus of this workshop was on space education in the USA the international dimensions of this problem were also addressed and the firm conclusion was reached that similar issues and concerns apply in Europe, Canada, Japan and other spacefaring nations. This article is an edited version of a White Paper subsequently produced to highlight the problem, summarize the proceedings of the workshop and present the results of the survey. Greater clarity in the definition of national space goals, the upgrading of teachers’ skills and an increase in technical scholarships are among the steps recommended.