The biggest technical stumbling block has been developing a material strong enough to be used for the cable. Engineers believe they have found a solution in carbon nanotubes, a synthetic material far stronger than steel now produced in the laboratory. That breakthrough leads some Space Elevator gurus, like Bradley Edwards of the Institute for Scientific Research to predict that simple elevators can be built in the near future with investments amounting to several billion dollars.
Solar farm/hydrogen fuel depot
The hydrogen economy doesn't begin to take off until the early 2000s, when the four-wheel automotive industry begins serious development of fuel cells and other systems to escape the cycle of combustion of hydrocarbon fuels, in which ancient methane, petroleum, and coal are burned, releasing unwanted atmospheric byproducts. Hydrogen is initially derived from methane and ethanol generated through 20th century processes. The bio-engineering of existing species of plants that can survive-and even thrive-in irrigation with sea water opens up vast desert areas to the restoration of biomass, and in the short term, eliminates concern about shortages of traditional hydrocarbons while virtually doubling the absorption of atmospheric carbon dioxide.
Moving in parallel with these events are incremental, compounding improvements in the non-dynamic generation of solar energy from static, solar cells, initially, and later, from the combining of quantum solar generation as provided by the original solar arrays of the 1900s with the bio-engineering of bacteria that work in conjunction with the electrical cell to improve efficiency by a factor of three. The steady progress in traditional solar generation is the "tortoise" to the thermonuclear-fusion movement's "hare." (A popular 2102 hologram reads, "Fusion power is 25 years away, and it always will be," as an arch comment on the long-illusive technology of fusion.)
Dynamic solar energy from the heating of various media by large complexes of focusing mirrors and lenses driving some fluid from liquid to high-energy gases to turn a rotating power generator is under continuous development, but offers only minor improvements decade on decade. It is unable to keep up with the advances in static cellular arrays generating direct current to inverters, which convert it to standard AC. Lack of efficiency gains combined with high capital costs lead to the gradual abandonment of "steam" plants in favor of the cells, with the eventual biological breakthrough merely serving to seal the coffin.
So the production of plentiful methane and ethanol from biomass, coupled with massive investment in the process of harvesting hydrogen from these sources, provides an initial impetus to the conversion to hydrogen infrastructure. At Neil Armstrong Intercontinental Airport, the majority of hydrogen is produced through boosted electrolysis that relies on the bio-solar process. Recent introductions of proprietary bacterial strains from a Brazil research laboratory have bumped up efficiency another 2.2 percent.
The result of a whole century of development and energy evolution is plentiful energy for the foreseeable future but at significant cost to users as the enormous capital investment in infrastructure cannot be recovered until 2140 at the earliest. And who knows what new investments may yet be needed?
The merging of the so-called "hard" and "soft" materials into bio-alloys that mix traditional metal alloys in matrix form with chemically and molecularly versatile elements such as carbon, silicon, and lithium in combination with synthetic cellular elements that mimic mitochondria, vacuoles, and microtubules in their interaction with the medium surrounding them has literally recast material sciences and altered design and manufacturing. By managing the properties of these alloys as well as distributing actuation at a molecular level, the old mechanical picture of everything from vehicles to building construction has become no more than a fond memory.
Two-century-old works of fiction that describe morphing vehicles do not get it all quite right, which is not so surprising considering the abrupt changes in direction the technology has taken.
Offshore international airports
To remove the noise of hypersonic aircraft from the settled areas of the mainland, nodes for hypersonic travel begin in 2040 to be located offshore near the major markets they serve. The first of these are built about 45 miles off the California coast of the United States and some 150 miles southeast of Okinawa-Japan doesn't want to hear the faintest rumbling of thrusters-and connected via high-speed magnetic levitation trains and aircraft to terminals on the mainland. This same model was repeated across the globe as former land-based international terminals for flagships of the fleet became secondary airports acting as distribution points for passengers and freight to inter-urban areas, and eventually to the metro-rurals as the population dispersed.
Older spanloaders mix somewhat awkwardly with the scampering hyperliners, but their low-cost inter-airport services are crucial to knitting the entire global system together. Nearly inaudible and completely automatic, the slower "spans" pioneers the pilotless massive-database systems that now also operates personal fliers.