The commercial development of space: is an international regulatory framework needed?

The commercial space sector to date has failed to develop comprehensive regulations--"rules of the road"--for its international activities. Within the next 5 years, conflicts with respect to international trade in satellite sales and launch services could emerge, highlighting the need for such a regulatory framework. If the commercial space sector is to continue to develop, it is important to begin discussions now, before these conflicts become significant, on the elements of an appropriate international regulatory framework. The existing framework for space activities was developed when government, not commercial, space activities were dominant, or was adapted from regulations in other sectors such as terrestrial telecommunications.     

Autonomous orbit maintenance system

Orbit maintenance is a major cost factor for Earth satellites in specialized orbits, such as a repeating ground track, or in formations. While autonomous attitude control is well established, the spacecraft's orbit is usually uncontrolled or maintained by ground station commands. For small, lower cost satellites, operations costs can be a dominant element of both cost and risk. This implies a need for low-cost autonomous orbit maintenance in order to allow such systems to be economically viable, particularly in today's constrained budget environment.

In addition, if the position of the spacecraft is controlled, it is therefore known in advance. Thus, mission planning can be done as far in advance as desired, without the need for replanning and frequent updating due to unpredictable orbit decay. An interesting characteristic of autonomous orbit maintenance is that it typically requires less software, and less complex software, than does orbit control from the ground. In many cases, an onboard orbit propagator is not needed.     

Space visions from a new generation

Through experiences at the International Space University's 1995 Summer Session, the authors became aware of generational differences of opinion with regard to visions for future space activities. The faculty members had expansionary visions of space exploration and colonization, while the students, having grown up in a very different environment, had concerns which centered around using space to improve life on Earth. This paper addresses possible explanations for these different perspectives. The visions of this younger generation are those which will shape the space policy of the future and are even beginning to shape it today.     

2010: The Symbionic Cockpit

The cockpit of the year 2010 is described in terms of both the capabilities and systems it contains and how the pilot interacts with it. A brief mission narrative is provided describing seveal hours in the life of the Manta air superiority fighter. This is followed by a discussion of the pilot interface components employed in the cockpit including hueristic voice, instrument panel display, canopy display, and holographic display systems. The concept of a ``symbionic' system is then introduced, describing in some detail the capabilities and features of a cockpit system that senses the physiological and mental state of the pilot and responds accrodingly. Finally, conclusions and predictions are made that summarize and emphasize the points made in the paper.     

Chemical evolution on the giant planets and Titan

We summarize the current status of atmospheric chemistry in the atmospheres of the outer solar system with special emphasis on the question of HCN formation on Jupiter, differences between polar and equatorial compositions on Jupiter, the coloration of the Great Red Spot, and the unique environment of Titan.     

New information on Saturn and its rings from multi-frequency VLA data

High resolution radio data of Saturn have been obtained at 1.3, 2, 6, and 21 cm, at different inclination angles of the ring plane. Preliminary results of limb darkening curves on the planet and optical depth measurements in the rings are described.     

Laser Doppler Velocimeter Development

A new two-channel laser Doppler velocimeter developed for the Ames High Reynolds Channel No. II is described. Design features required for the satisfactory operation of the optical system in the channel environment are discussed. Fiber optics are used to transmit the megahertz Doppler signal to the photodetectors located outside the channel pressure vessel, and provision is made to isolate the optical system from pressure and thermal strain effects. Computer-controlled scanning mirrors are used to psoition the laser beams in the channel flow. Techniques used to seed the flow with 0.5-?-diam polystyrene spheres avoiding deposition on the test-section windows and porous boundary-layer removal panels are described. Preliminary results are presented with a discussion of several of the factors affecting accuracy.     

Computational prediction of airfoil dynamic stall

The term dynamic stall refers to unsteady flow separation occurring on aerodynamic bodies, such as airfoils and wings, which execute an unsteady motion. The prediction of dynamic stall is important for flight vehicle, turbomachinery, and wind turbine applications. Due to the complicated flow physics of the dynamic stall phenomenon the industry has been forced to use empirical methods for its prediction. However, recent progress in computational methods and the tremendous increase in computing power has made possible the use of the full fluid dynamic governing equations for dynamic stall investigation and prediction in the design process. It is the objective of this review to present the major approaches and results obtained in recent years and to point out existing deficiencies and possibilities for improvements. To this end, potential flow, boundary layer, viscous–inviscid interaction, and Navier–Stokes methods are described. The most commonly used numerical schemes for their solution are briefly described. Turbulence models used for the computation of high Reynolds number turbulent flows, which are of primary interest to industry, are presented. The impact of transition from laminar to turbulent flow on the dynamic stall phenomenon is discussed and currently available methods for its prediction are summarized. The main computational results obtained for airfoil and wing dynamic stall and comparisons with available experimental measurements are presented. The review concludes with a discussion of existing deficiencies and possibilities for future improvements.