Interstellar travel is the hypothetical travel of spacecraft between star systems. Due to the vast distances between the Solar System and nearby stars, interstellar travel is not practicable with current propulsion technologies.
Beam-powered propulsion, also known as directed energy propulsion, is a class of aircraft or spacecraft propulsion that uses energy beamed to the spacecraft from a remote power plant to provide energy. The beam is typically either a microwave or a laser beam, and it is either pulsed or continuous. A continuous beam lends itself to thermal rockets, photonic thrusters, and light sails. In contrast, a pulsed beam lends itself to ablative thrusters and pulse detonation engines.
A fusion rocket is a theoretical design for a rocket driven by fusion propulsion that could provide efficient and sustained acceleration in space without the need to carry a large fuel supply. The design requires fusion power technology beyond current capabilities, and much larger and more complex rockets.
The Bussard ramjet is a theoretical method of spacecraft propulsion for interstellar travel. A fast moving spacecraft scoops up hydrogen from the interstellar medium using an enormous funnel-shaped magnetic field ; the hydrogen is compressed until thermonuclear fusion occurs, which provides thrust to counter the drag created by the funnel and energy to power the magnetic field. The Bussard ramjet can thus be seen as a ramjet variant of a fusion rocket.
A starship, starcraft, or interstellar spacecraft is a theoretical spacecraft designed for traveling between planetary systems. The term is mostly found in science fiction. Reference to a "star-ship" appears as early as 1882 in Oahspe: A New Bible.
Nuclear pulse propulsion or external pulsed plasma propulsion is a hypothetical method of spacecraft propulsion that uses nuclear explosions for thrust. It originated as Project Orion with support from DARPA, after a suggestion by Stanislaw Ulam in 1947. Newer designs using inertial confinement fusion have been the baseline for most later designs, including Project Daedalus and Project Longshot.
A generation ship, generation starship or world ship, is a hypothetical type of interstellar ark starship that travels at sub-light speed. Since such a ship might require hundreds to thousands of years to reach nearby stars, the original occupants of a generation ship would grow old and die, leaving their descendants to continue traveling.
An interstellar ark is a conceptual starship designed for interstellar travel. Interstellar arks may be the most economically feasible method of traveling such distances. The ark has also been proposed as a potential habitat to preserve civilization and knowledge in the event of a global catastrophe.
Eugen Sänger was an Austrian aerospace engineer best known for his contributions to lifting body and ramjet technology.
Laser propulsion is a form of beam-powered propulsion where the energy source is a remote laser system and separate from the reaction mass. This form of propulsion differs from a conventional chemical rocket where both energy and reaction mass come from the solid or liquid propellants carried on board the vehicle.
Project Daedalus was a study conducted between 1973 and 1978 by the British Interplanetary Society to design a plausible uncrewed interstellar probe. Intended mainly as a scientific probe, the design criteria specified that the spacecraft had to use existing or near-future technology and had to be able to reach its destination within a human lifetime. Alan Bond led a team of scientists and engineers who proposed using a fusion rocket to reach Barnard's Star 5.9 light years away. The trip was estimated to take 50 years, but the design was required to be flexible enough that it could be sent to any other target star.
Project Longshot was a conceptual interstellar spacecraft design. It would have been an uncrewed starship, intended to fly to and enter orbit around Alpha Centauri B powered by nuclear pulse propulsion.
An interstellar probe is a space probe that has left—or is expected to leave—the Solar System and enter interstellar space, which is typically defined as the region beyond the heliopause. It also refers to probes capable of reaching other star systems.
An electric sail is a proposed form of spacecraft propulsion using the dynamic pressure of the solar wind as a source of thrust. It creates a "virtual" sail by using small wires to form an electric field that deflects solar wind protons and extracts their momentum. The idea was first conceptualised by Pekka Janhunen in 2006 at the Finnish Meteorological Institute.
Project Icarus is a theoretical engineering design study aimed at designing a credible, mainly nuclear fusion-based, unmanned interstellar space probe. Project Icarus was an initiative of members of the British Interplanetary Society (BIS) and the Tau Zero Foundation (TZF) started in 2009. The project was under the stewardship of Icarus Interstellar until 2019. It remains a BIS project.
The Initiative for Interstellar Studies (i4is) is a UK-registered not-for-profit company, whose objectives are education and research into the challenges of Interstellar Travel. It pioneered small-scale laser sail interstellar probes and missions to interstellar objects. Several of its principals were involved in the 100 Year Starship winning team originated by NASA and DARPA.
Breakthrough Initiatives is a science-based program founded in 2015 and funded by Julia and Yuri Milner, also of Breakthrough Prize, to search for extraterrestrial intelligence over a span of at least 10 years. The program is divided into multiple projects. Breakthrough Listen will comprise an effort to search over 1,000,000 stars for artificial radio or laser signals. A parallel project called Breakthrough Message is an effort to create a message "representative of humanity and planet Earth". The project Breakthrough Starshot, co-founded with Mark Zuckerberg, aims to send a swarm of probes to the nearest star at about 20% the speed of light. The project Breakthrough Watch aims to identify and characterize Earth-sized, rocky planets around Alpha Centauri and other stars within 20 light years of Earth. Breakthrough plans to send a mission to Saturn's moon Enceladus, in search for life in its warm ocean, and in 2018 signed a partnership agreement with NASA for the project.
Breakthrough Starshot is a research and engineering project by the Breakthrough Initiatives to develop a proof-of-concept fleet of light sail interstellar probes named Starchip, to be capable of making the journey to the Alpha Centauri star system 4.34 light-years away. It was founded in 2016 by Yuri Milner, Stephen Hawking, and Mark Zuckerberg.
Project Lyra is a feasibility study of a mission to interstellar objects such as ʻOumuamua and 2I/Borisov, initiated on 30 October 2017 by the Initiative for Interstellar Studies (i4is). In January 2022, researchers proposed that a spacecraft launched from Earth could catch up to 'Oumuamua in 26 years for further close-up studies.
Project Hyperion, launched in December 2011 by Andreas M. Hein in the context of Icarus Interstellar, is a project aimed at performing a preliminary study that defined integrated concepts for a crewed interstellar starship or generation ship. This is a study mainly based out of the WARR student group at the Technical University of Munich (TUM). The study aims to provide an assessment of the feasibility of crewed interstellar flight using current and near-future technologies. It also aims to guide future research and technology development plans as well as to inform the public about crewed interstellar travel.
