Power generation in the 22nd century
Nuclear fusion is the dominant form of power generation and propulsion in the 22nd century, producing vast amounts of non-polluting energy from astronomically-abundant fuel sources. A series of innovations in the late 21st century, including the discovery of room-temperature superconductivity, paved the way for the creation of the first viable fusion reactor, which in turn led to the flight of the first fusion torch engine spacecraft, the Prometheus, in 2093.
Modern fusion reactors operate on the principle of magnetically-insulated inertial confinement fusion (MICF). Fuel pellets composed of deuterium and helium-3, surrounded by a shell of lead and lithium, are injected into the reactor chamber and ignited by a laser. A spherical magnetic field captures and sustains the fusion reaction. The D-3He reaction produces roughly 75% thermal radiation and 20% charged particles, the remainder being neutron radiation produced by “stray” deuterium-deuterium reactions. These neutrons are absorbed by the fuel pellet’s metallic shell. Energy capture is through a combination of direct energy conversion of charged particles and thermocouples. Heat is removed by water, eutectic metal alloy, or molten salt coolants, depending on the reactor’s power. Surface-based fusion reactors use their coolant to heat a working fluid to drive a turbine for further energy production, though this is generally too heavy and complex for integration aboard spacecraft. The reaction’s by-products, comprising helium nuclei and the residue of the metallic shell, known as fusion ash, are evacuated through the base of the reactor.
A less-common form of fusion power is lattice confinement fusion (LCF), in which an erbium-titanium alloy saturated with deuterium is exposed to ionising radiation, triggering fusion reactions in the spaces between the alloy’s atoms. LCF is considerably less energetic than MICF, but has the advantage of being a far more compact, solid-state system that does not rely on powerful magnetic fields, laser ignition, or extreme temperatures. Such “fusion batteries” are therefore ideal for emergency power supplies or prolonged operation in remote, austere environments. Long-range space probes deployed to the Kuiper Belt and Oort Cloud make use of LCF generators. So-called “battery bots”, effectively LCF generators on a pair of caterpillar tracks like the Hyneman Corporation’s Gram and Industrial Robotics’ PWR series, are common sites on scientific expeditions and military camps.
The foundation and expansion of the World Union for Space Policy has seen fusion technology proliferate across the globe. Cheap, safe, and reliable fusion power has replaced virtually all other forms of energy generation, liberating humanity from polluting, greenhouse gas-producing fossil fuels. Fossil fuels still see use in a handful of niche applications such as power and transport for extremely isolated communities, but their consumption has fallen dramatically since their peak use in the early 21st century. Most jurisdictions retain wind and solar farms to diversify their energy grids, while World Union regulations require all modern buildings to be fitted with solar panels as standard. Superconducting magnetic energy storage is the dominant form of grid-scale storage for industrial and commercial applications.
In personal electronics, robotics, and vehicles, lithium-oxygen batteries predominate. These have a much higher specific energy compared to earlier lithium-ion batteries and have supported the proliferation of battery electric vehicles and domestic and municipal robots. Where lithium-oxygen batteries are impractical or unusable, graphene and nanowire technology has substantially increased the performance of traditional lithium-ion batteries. Ubiquitous wireless inductive charging points in modern cities mean that electric vehicles have supplanted the internal combustion engine across most of Earth. Off-road vehicles, exploration rovers, and military vehicles, by contrast, typically rely on banks of hydrogen fuel cells, which convert a reaction of hydrogen and oxygen into electricity with water as a byproduct. While somewhat less efficient than lithium-oxygen batteries, fuel cells have the advantage of greater reliability in the field and greater ease of refuelling: while hydrogen typically has complex, delicate storage requirements, modern fuel cells vehicles rely on a non-volatile magnesium hydride paste, which releases hydrogen when introduced to water. The hydrogen is then diverted to the fuel cell, leaving magnesium hydroxide as a waste product. A fuel cell vehicle therefore has significantly reduced fuelling time compared to charging a battery electric vehicle and can carry additional containers of hydrogen paste and water for wilderness refuelling.