Interplanetary spaceflight or interplanetary travel is the crewed or uncrewed travel between stars and planets, usually within a single planetary system. In practice, spaceflights of this type are confined to travel between the planets of the Solar System. Uncrewed space probes have flown to all the observed planets in the Solar System as well as to dwarf planets Pluto and Ceres, and several asteroids. Orbiters and landers return more information than fly-by missions. Crewed flights have landed on the Moon and have been planned, from time to time, for Mars, Venus and Mercury. While many scientists appreciate the knowledge value that uncrewed flights provide, the value of crewed missions is more controversial. Science fiction writers propose a number of benefits, including the mining of asteroids, access to solar power, and room for colonization in the event of an Earth catastrophe.
In celestial mechanics, the Lagrange points are points of equilibrium for small-mass objects under the gravitational influence of two massive orbiting bodies. Mathematically, this involves the solution of the restricted three-body problem.
Space colonization is the use of outer space for colonization, such as permanent habitation, exploitation or territorial claims. Extraterrestrial colonization is its broader form, including the use of celestial bodies, other than Earth, for colonization.
A Bernal sphere is a type of space settlement intended as a long-term home for permanent residents, first proposed in 1929 by John Desmond Bernal.
A space settlement is a more advanced form of habitation in outer space than a space station or habitation module, in that it is intended as a permanent settlement or green habitat rather than as a simple way-station or other specialized facility. No space settlement has been constructed yet, but many design concepts, with varying degrees of realism, have come both from engineers and from science-fiction authors.
Gerard Kitchen O'Neill was an American physicist and space activist. As a faculty member of Princeton University, he invented a device called the particle storage ring for high-energy physics experiments. Later, he invented a magnetic launcher called the mass driver. In the 1970s, he developed a plan to build human settlements in outer space, including a space habitat design known as the O'Neill cylinder. He founded the Space Studies Institute, an organization devoted to funding research into space manufacturing and colonization.
Colonization of the Moon is a process or concept employed by some proposals for robotic or human exploitation and settlement endeavours on the Moon. Settling of the Moon is, therefore, a more specific concept of lunar habitation, for which the broader concept of colonization is often used as a synonym, a use that is contested in the light of colonialism.
A megastructure is a very large artificial object, although the limits of precisely how large vary considerably. Some apply the term to any especially large or tall building. Some sources define a megastructure as an enormous self-supporting artificial construct. The products of megascale engineering or astroengineering are megastructures.
Artificial gravity is the creation of an inertial force that mimics the effects of a gravitational force, usually by rotation. Artificial gravity, or rotational gravity, is thus the appearance of a centrifugal force in a rotating frame of reference, as opposed to the force experienced in linear acceleration, which by the equivalence principle is indistinguishable from gravity. In a more general sense, "artificial gravity" may also refer to the effect of linear acceleration, e.g. by means of a rocket engine.
Asteroid mining is the hypothetical extraction of materials from asteroids and other minor planets, including near-Earth objects.
Colonization or settlement of Mars is the theoretical migration of humans to Mars and the establishment of long-term human presence on the planet. The prospect has garnered interest from public space agencies and private corporations and has been extensively explored in science fiction writing, film, and art. Organizations have proposed plans for a human mission to Mars, the first step towards any colonization effort, but thus far no person has set foot on the planet, and there have been no return missions. However, landers and rovers have successfully explored the planetary surface and delivered information about conditions on the ground.
The L5 Society was founded in 1975 by Carolyn Meinel and Keith Henson to promote the space colony ideas of Gerard K. O'Neill.
Asteroids, including those in the asteroid belt, have been suggested as possible sites of space colonization. Motives include the survival of humanity, and the specific economic opportunity for asteroid mining. Obstacles include transportation distance, temperature, radiation, lack of gravity, and psychological issues.
Space-based solar power is the concept of collecting solar power in outer space with solar power satellites (SPS) and distributing it to Earth. Its advantages include a higher collection of energy due to the lack of reflection and absorption by the atmosphere, the possibility of very little night, and a better ability to orient to face the Sun. Space-based solar power systems convert sunlight to some other form of energy which can be transmitted through the atmosphere to receivers on the Earth's surface.
The High Frontier: Human Colonies in Space is a 1976 book by Gerard K. O'Neill, a road map for what the United States might do in outer space after the Apollo program, the drive to place a human on the Moon and beyond. It envisions large human occupied habitats in the Earth-Moon system, especially near stable Lagrangian points. Three designs are proposed: Island one, Island two, and Island 3. These would be constructed using raw materials from the lunar surface launched into space using a mass driver and from near-Earth asteroids. The habitats were to spin for simulated gravity and be illuminated and powered by the Sun. Solar power satellites were proposed as a possible industry to support the habitats.
Lagrange point colonization is a proposed form of space colonization of the five equilibrium points in the orbit of a planet or its primary moon, called Lagrange points.
Inflatable habitats or expandable habitats are pressurized tent-like structures capable of supporting life in outer space whose internal volume increases after launch. They have frequently been proposed for use in space applications to provide a greater volume of living space for a given mass.
A rotating wheel space station, also known as a von Braun wheel, is a concept for a hypothetical wheel-shaped space station. Originally proposed by Konstantin Tsiolkovsky in 1903, the idea was expanded by Herman Potočnik in 1929.
A Bishop Ring is a type of hypothetical rotating space habitat originally proposed in 1997 by Forrest Bishop of the Institute of Atomic-Scale Engineering. The concept is a smaller scale version of the Banks Orbital, which itself is a smaller version of the Niven ring. Like other space habitat designs, the Bishop Ring would spin to produce artificial gravity by way of centrifugal force. The design differs from the classical designs produced in the 1970s by Gerard K. O'Neill and NASA in that it would use carbon nanotubes instead of steel, allowing the habitat to be built much larger. In the original proposal, the habitat would be approximately 1,000 km (620 mi) in radius and 500 km (310 mi) in width, containing 3 million square kilometers of living space, comparable to the area of Argentina or India.
An O'Neill cylinder is a space settlement concept proposed by American physicist Gerard K. O'Neill in his 1976 book The High Frontier: Human Colonies in Space. O'Neill proposed the colonization of space for the 21st century, using materials extracted from the Moon and later from asteroids.
