References and footnotes:
 Leslie White, The Evolution of Culture: The Development of Civilization to the Fall of Rome (New York: McGraw Hill, 1959), 3.
 Leslie White, “Energy and the Evolution of Culture,” American Anthropologist 45, no. 3 (July-September, 1943): 335.
 White, Energy and the Evolution of Culture (New York: Grove Press, 1949), 111.
 Britain, as an island nation with an increasing population, was an exception, switching to coal in the 1500s because of shortages of wood fuel well before it industrialized with steam power.
 Carl E. Behrens et al., US Fossil Fuel Resources: Terminology, Reporting, and Summary, 7-5700, December 28, 2011 (Washington, DC: Congressional Research Service, 2011), Table 4, pp. 15-16.
 Decision Demographics, Inc.
 The coming humanoid robotic revolution will likely substantially increase the human per-capita energy use. These robots will require energy for operation, transportation, housing, manufacturing, etc.
 Hydrogen is very difficult to store and handle in the general consumer market. It is quite likely that carbon will be extracted from the CO2 in the atmosphere and combined with the hydrogen to produce methane, the primary component of natural gas. The technology for handling, storing, and using methane is well established. The carbon released into the atmosphere, from the combustion of this methane, will be recycled back into plants and more methane. It is quite possible that some of this artificial methane will be pumped back underground into depleted oil and gas wells for long-term storage, essentially returning to the earth what was extracted this past century. In this manner, a substantial portion of the “excess” carbon currently in the atmosphere can be captured and removed from the atmosphere—provided sufficient sustainable electricity is available to produce the hydrogen.
 Currently, the gross thermal energy equivalent used by the United States is about 18 billion BOE/year. Of this total, historically about 40% has been used to generate electricity, with the remainder being carbon fuels used directly for transportation, heating, etc. In the all-nuclear energy infrastructure, to meet the historical 60% fuel needs, the hydrogen fuel must be produced using nuclear electricity. Using projected future electrolysis efficiencies, around 0.002443 GWh will be needed to produce one BOE of hydrogen. Thus, for providing both nuclear electricity (directly) and hydrogen fuel (indirectly), it works out that each 1-GW nuclear plant provides the equivalent of 5 million BOE of gross thermal energy. About 85% of the total nuclear electricity produced each year by the nuclear power plant would be used to produce hydrogen.
 While many elements and many isotopes of these elements are radioactive—meaning that they undergo spontaneous nuclear decay—only three isotopes are capable of being used in a nuclear fission reactor or weapon. These are uranium-233, uranium-235, and plutonium-239. “Breeding” is where another isotope is artificially transmuted, in a nuclear reactor, into one of these three fissionable isotopes.
 Nuclear reactor designs using nuclear waste as fuel are being developed. These generally involve breeding U-233 or Pu-239. This technology is in a very early stage of development, with China leading much of this effort.
 The overall 46% efficiency takes into account a loss of 5% for the transmission of the wind-electricity to the electrolysis plants, a 20% loss for the conversion of the wind-electricity into hydrogen fuel, and a 40% loss for the generation of electricity using the hydrogen: (1 – .05) ´ (1 – .20) ´ (1 – .40) = 0.46.
 The wind’s speed falls as it passes through the rotating blades of the wind turbine because the turbine is extracting power from the wind to turn the generator. As this happens, the wind picks up a rotational velocity that causes the lower-speed winds to mix with higher-speed winds at higher elevation. Due to this mixing, the wind’s speed close to the ground increases back to its original speed. This occurs over a distance downwind of the turbine. Thus, if the next turbine is placed too close, the incoming wind speed is lower, producing less electrical power.
 By their design, wind turbines produce alternating current or AC electrical power. Ground solar photovoltaic panels produce direct current or DC power. This must be converted to AC power before sending the electricity into the power grid. This DC-AC conversion is about 78% efficient. Thus, the nameplate power rating of solar farms must be stated in terms of the AC power produced.
 The space-based solar arrays will be in continuous sunlight 365 days a year, 24 hours a day, except when these arrays pass into the Earth’s shadow. This only happens near the spring and fall equinoxes and happens for only a couple of hours a day at local midnight, at a time when power demand is reduced. Gas turbine generators would provide electricity during this period.
 This is the cost of building 6,180 new plants. With a projected nuclear plant lifetime of 60 years, about 1000 early plants would need to be replaced by 2100. This replacement cost is not included. Also, plant maintenance, fueling, nuclear waste disposal, and other such costs are not included.
 The rest of the world will likely need to expend $5-6 trillion each year to have their space-based power systems built—a substantial percentage of this could be undertaken by US companies.
 Building and operating this new spacefaring enterprise will require a significant step forward in design sophistication and standardization, product quality, manufacturing, robotic and tele-presence capabilities, software, etc. This new engineering expertise will filter into everything else as it sets the new standard.
 That the Soviet Union launched the first satellite was an intentional US foreign policy objective. By letting the Soviets launch first, they established, rather than opposed, the legal precedent of the freedom of orbiting satellites to pass over another country. They reinforced this with the first orbiting manned mission.
 The manned DynaSoar reusable spaceplane—about the size of small fighter jet—was to be launched on an expendable launch vehicle. This is being done today, although unmanned, with the Boeing X-40 spaceplane.
 President Kennedy was first and foremost a politician. He had no particular interest in space. The manned lunar landing goal was a 1961 political response to the Soviet Union’s then lead in manned space operations coupled with the failure of the American CIA’s Bay of Pigs invasion of Cuba just weeks earlier. After the Cuban Missile crisis that almost brought nuclear war, and shortly before he was killed in 1963, Kennedy appeared to be ready to roll back the lunar landing goal. In a speech at the United Nations he proposed a joint expedition to the Moon with the Soviet Union and was having policy analysts evaluate the projected costs of the Apollo Program. The key point is that the Apollo Program was pursuing political goals, not spacefaring operational goals. After Kennedy’s death, it became his legacy. This is why this program left little useful post-Apollo spacefaring infrastructure. The need for America to become energy secure with sustainable space-based power is a clear operational goal rather than merely a “feel good” political goal.
 A safety risk assessment performed by NASA after Space Shuttle operations ended, using safety assessment tools not available 30 years ago, found that the early Shuttle flights had a likely probability of failure of about 1:12. By the end of the program, this had only improved to about 1:100.
 An employee of a company traveling to a destination on a company-owned system is not a passenger in the legal sense of the word. Employees accept the safety risk of the transportation used by willingly being employees. Employee safety is governed by other laws and regulations. NASA astronauts, as employees, are not passengers when they travel on NASA-provided spaceflight systems like the Space Shuttle. However, when the company sends the employee on a trip using a commercial carrier with a purchased fare, the employee becomes a passenger.
 These decisions were made prior to the first oil supply crisis—an important event in triggering the initial interest in space-based power undertaken in the late 1970s and early 1980s.
 A quasi-SSTO approach used some form of launch assistance such as droppable rocket packs.
 A decision to start the conceptual assessment of a new military weapon system follows the preparation and approval of a formal statement of need, citing a military mission deficiency and the lack of an existing solution. This is how the military TAV studies began.
 One quasi-SSTO approach was the Boeing Reusable Aerospace Vehicle (RASV). This concept emerged in the late 1970s from Air Force studies. It used then-available rocket, structures, and materials concepts. In 1982, the chairman of Boeing gave the internal company go-ahead to propose to the Air Force building a prototype RASV. This indicates the level of maturity of these primarily rocket-powered systems in the 1980s was sufficient for a major aerospace contractor to support program initiation. The RASV was one of several TAV concepts studied as part of the TAV studies.
 See Boeing’s patent, US4802639, Horizontal-takeoff transatmospheric launch system, originally filed on September 28, 1984, during the time the Air Force TAV studies were underway. This patent was granted in 1989. This patent is for a fully reusable, two-stage, horizontal takeoff and landing manned space access system.
 The concept of a scramjet-powered SSTO came out of the first aerospaceplane studies of the early 1960s.
 To achieve a stable LEO, the space flight system must reach the required orbital velocity—a function of orbital altitude—which is not dependent on the design of the flight system. Whether the system is one-stage or two-stage, is rocket-powered or uses airbreathing propulsion, the necessary orbital velocity is the same. Design closure is when a design is predicted to be able to reach this orbital velocity. Only designs that close, with reasonable margins for shortfalls in design and performance, are considered viable.