The LEO Archipelago: A system of earth-rings for communications,mass-transport to space,solar power,and control of global warming

Man's quest to get into space is hindered by major problems (e.g., system-development and capital costs, expense of putting mass into orbit, trapped-radiation belts, and environmental impact of a large increase in rocket launches). A multi-purpose low-earth-orbit system of rings circling the earth – the “LEO ARCHIPELAGO^TM” – is proposed as a means of solving or bypassing many of them. A fiber-optic ring about the earth would be an initial testing and developmental stage for the Ring Systems, while providing cash-flow through a LEO-based, high-band-width, world-wide communication system. A low-earth-orbit-based space-elevator system, “Sling-on-a-Ring^TM”, is proposed as the crucial developmental stage of the LEO Archipelago. Being a LEO-based heavy-mass lifter, rather than earth- or GEO-based, it is much less massive and therefore less costly than other proposed space-elevators. With the advent of lower-cost, higher-mass transport to orbit, the options for further space development (e.g., space solar power, radiation, and space-debris dampers, sun shades, and permanent LEO habitation) are greatly expanded.This paper provides an update of the Sling-on-a-Ring concept in terms of new materials, potential applications, and trade-offs associated with an earlier model. The impact of Colossal Carbon Tubes, CCT, a new material with high tensile strength, extremely-low density, and other favorable properties, and other new technologies (e.g., solar-powered lasers, power beaming to near-space and earth, and thermal-control systems) on the development of associated LEO-Ring systems is also explored. The material's effect on the timeline for the system development indicates the feasibility of near-term implementation of the system (possibly within the decade). The Sling-on-a-Ring can provide a less-expensive, environment-friendly mode of access to space. This would pave the way (via eventual operation at >1000 t per day by 2050) for large scale development of space-based technologies.     

Multimode adaptive signal processing: a new approach to GMTI radar

We show how a single reflector antenna with a multimode feed horn can be used in a ground moving target indication (GMTI) radar. In particular, we demonstrate the simultaneous detection and estimation of angular location of a ground moving target via adaptive cancellation of ground clutter     

Modeling of dielectric barrier discharge-induced fluid dynamics and heat transfer

A dielectric barrier discharge, operating at kHz and kV conditions, can generate largely isothermal surface plasma and induce wall-jet-like fluid flow. It can serve as an aerodynamic actuator, and has advantages of no moving parts. In order to better understand the mechanism of the momentum coupling between the plasma and the fluid flow, both computational modeling and experimental information are presented. Furthermore, the impact of such athermal, non-equilibrium plasma discharges on low-speed aerodynamics and heat transfer is discussed. The plasma and fluid species are treated as a two-fluid system exhibiting decades of length and time-scale disparities. For Reynolds numbers of 10⁴–10⁵, the time-scales ratios between those characterizing the discharge physics (convection, diffusion, and reaction/ionization) and the fluid flow mechanisms are separated by several decades, allowing the effect of plasma on the fluid dynamics modeled via a one-way body force treatment. At a phenomenological level, the plasma model can be established using a linearized force distribution to approximate the discharge structure. A high-fidelity approach using a first-principle-based hydrodynamic-plasma model is also reviewed. Numerical techniques such as operating splitting are introduced in order to handle the computational stiffness resulting from the time and length scale variations. The goal is to use time-step sizes in the range of the fluid dynamics level while treating the fast varying ones statistically. The momentum coupling is discussed in the context of discharge chemistry; species transport properties, insulator and electrode materials, and dielectric barrier discharge (DBD) geometry. Parametric studies conducted on the operating variables such as voltage, frequency and geometric arrangements offer substantial insight into the plasma physics, as well as a basis to explore thermal management and flow control applications.