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Author: Chapman208 Big gold star, 5000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: of 27  
Subject: Re: Space elevators Date: 2/21/2006 10:14 AM
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>>>>One other thing: congrats on the superconductor angle; we're closer to that (IMO) than you might think. Japan's 70-km superconductor maglev train test track has always been regular superconductors; but last year, for the first time, they got into high-temperature superoconductor testing, with HTS wire from American Superconductor in Massachusets.

JP: That's good news. I hadn't heard. My story is set ~170 years in the future, so that allowed me to declare that all these mundane "picks and shovels" types of problems have long since been overcome. Here's how I describe the basics of the space elevator. (Each chapter of the book begins with a fictional encyclopedia entry about some aspect of what happens in that chapter.)

Chapter 1.
Engineering Marvels: Space Elevator
– A space elevator consists of three sections: 1) A GEOSTATIONARY space station, called an ORBITAL DOCKING FACILITY (ODF); 2) A base platform, which serves to anchor the ODF on or near the equator of Earth or another planet; and 3) Multiple ribbon cables and elevator cars connecting the two. Each cable is formed from a high-tensile composite consisting primarily of dozens of micron-thick bonded layers of MULTIWALLED CARBON NANOTUBES (CNTs). CNTs have a strength-to-weight ratio hundreds of times superior to that of steel. Elevator cars operating on the principles of MAGNETIC LEVITATION (MAGLEV) ride along these cables at high rates of speed.
-- Excerpt from Encyclopedia Solaris, 2176.

Chapter 2.
Engineering Marvels: Space Elevator
– Up to six MAGNETIC LEVITATION (MAGLEV) elevator cars travel up and down each ribbon cable, transporting both passengers and cargo. The cars differ in many ways from traditional land-based maglev trains. Rather than riding atop a narrow horizontal rail, the elevator car is suspended alongside a vertical flat ribbon cable. The ribbon passes between two sets of magnets, on the front and back sides of the cable. This arrangement prevents the train from drifting away from the ribbon. An elevator car has to travel tens of thousands of kilometers nonstop. Therefore, it is impractical for an elevator car to be self-powered. Instead, the motive force is provided by the ribbon cable.

The cables could not be made of copper for several reasons: 1) copper is far too bulky and heavy, 2) it was in short supply, and 3) too much power would dissipate along the way. Some sort of lightweight superconductor was required. The cable is composed primarily of MULTIWALLED CARBON NANOTUBES (CNTs), reinforced with BORON NITRIDE NANOTUBES. However, the outer courses of the ribbon, front and back, also contain a thin layer of HIGH-Tc superconducting material. These layers act as power conduits, reaching all the way from the ground platform to the ORBITAL DOCKING FACILITY. Woven transversely across the ribbon, in strips, are threads made of superconducting magnets that tap into the power source. As a result, the elevator cars need only enough internal power to maintain the onboard magnets and life support. The cable itself provides the motive force.

The strips are pulsed in series, like theater marquee lights that chase themselves in a loop. Strips in front of the car magnetically draw the car forward, while others push the car from behind. Then, as the car approaches its destination, the pulses reverse themselves to slow the car for docking.
-- Excerpt from Encyclopedia Solaris, 2176.


(Note: The part about High Tc superconducting materials came from Dr. Edwards.)

What I like about formatting the story this way is that those people who like hard SF can read the technical descriptions at the beginning of each chapter. Those who prefer soft SF can skip over the "boring details". This way it doesn't bog down the story with a lot of exposition in the middle of chapters.

Mark.
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