a straight cable with no variations in its cross section area, and found that the strength required would be twice that of any then-existing material including graphite, quartz, and diamond. In 1975, an American scientist, Jerome Pearson, reinvented the concept, publishing his analysis in the journal Acta Astronautica. He designed a cross-section-area altitude profile that tapered and would be better suited to building the elevator. The completed cable would be thickest at the geostationary orbit, where the tension was greatest, and would be narrowest at the tips to reduce the amount of weight per unit area of cross section that any point on the cable would have to bear. He suggested using a counterweight that would be slowly extended out to (almost half the distance to the Moon) as the lower sections of the elevator were built. Without a large counterweight, the upper portion of the cable would have to be longer than the lower due to the way gravitational and centrifugal forces change with distance from Earth. His analysis included disturbances such as the gravitation of the Moon, wind and moving payloads up and down the cable. The weight of the material needed to build the elevator would have required thousands of Space Shuttle trips, although part of the material could be transported up the elevator when a minimum strength strand reached the ground or be manufactured in space from asteroidal or lunar ore. After the development of carbon nanotubes in the 1990s, engineer David Smitherman of NASA/Marshall's Advanced Projects Office realized that the high strength of these materials might make the concept of a space elevator feasible, and put together a workshop at the Marshall Space Flight Center, inviting many scientists and engineers to discuss concepts and compile plans for an elevator to turn the concept into a reality. In 2000, another American scientist, Bradley C. Edwards, suggested creating a long paper-thin ribbon using a carbon nanotube composite material. He chose the wide-thin ribbon-like cross-section shape rather than earlier circular cross-section concepts because that shape would stand a greater chance of surviving impacts by meteoroids. The ribbon cross-section shape also provided large surface area for climbers to climb with simple rollers. Supported by the NASA Institute for Advanced Concepts, Edwards' work was expanded to cover the deployment scenario, climber design, power delivery system, orbital debris avoidance, anchor system, surviving atomic oxygen, avoiding lightning and hurricanes by locating the