Interstellar travel refers to the travel by interstellar probes or crewed spacecraft between stars or planetary systems in a galaxy. Interstellar travel would be much more difficult than interplanetary spaceflight. Whereas the distances between the planets in the Solar System are less than 30 astronomical units (AU), the distances between stars are typically hundreds of thousands of AU, and usually expressed in light-years. Because of the vastness of those distances, practical interstellar travel based on known physics would need to occur at a high percentage of the speed of light; even so, travel times would be long, at least decades and perhaps millennia or longer.The speeds required for interstellar travel in a human lifetime far exceed what current methods of space travel can provide. Even with a hypothetically perfectly efficient propulsion system, the kinetic energy corresponding to those speeds is enormous by today's standards of energy development. Moreover, collisions by the spacecraft with cosmic dust and gas can be very dangerous for both passengers and the spacecraft itself.A number of strategies have been proposed to deal with these problems, ranging from giant arks that would carry entire societies and ecosystems, to microscopic space probes. Many different spacecraft propulsion systems have been proposed to give spacecraft the required speeds, including nuclear propulsion, beam-powered propulsion, and methods based on speculative physics.For both crewed and uncrewed interstellar travel, considerable technological and economic challenges need to be met. Even the most optimistic views about interstellar travel see it as only being feasible decades from now. However, in spite of the challenges, if or when interstellar travel is realized, a wide range of scientific benefits is expected.Most interstellar travel concepts require a developed space logistics system capable of moving millions of tonnes to a construction / operating location, and most would require gigawatt-scale power for construction or power (such as Star Wisp or Light Sail type concepts). Such a system could grow organically if space-based solar power became a significant component of Earth's energy mix. Consumer demand for a multi-terawatt system would create the necessary multi-million ton/year logistical system.
Source: Interstellar travel (wikipedia.org)
[1111.6131] The Fermi Paradox, Self-Replicating Probes, and the Interstellar Transportation Bandwidth
Title: The Fermi Paradox, Self-Replicating Probes, and the Interstellar Transportation Bandwidth Authors: Keith B. Wiley Abstract: It has been widely acknowledged that self-replicating space-probes (SRPs) could explore the galaxy very quickly relative to the age of the galaxy.
Since such a ship might take centuries to thousands of years to reach even nearby stars, the original occupants of a generation ship would grow old and die, leaving their descendants to continue traveling.
Humankind's most distant emissaries are flying through a turbulent sea of magnetism as they seek to break free of our Solar System.
The most distant spacecraft from Earth, Voyager 1, is executing a series of roll manoeuvres, proving the 33-year-old explorer is in great shape. The extraordinary Voyager 1 spacecraft is demonstrating its nimbleness more than 30 years after leaving Earth.
When I sat down with the mission's project scientist in California in August 2012, his response was much the same as always: "My best estimate is that it will be in the next couple of years, but it may be in the next couple of days. It's unknown." Not anymore.
Chemical factories around young stars may give rise to far more complex molecules than previously thought. Relatively complex, carbon-containing molecules are found in comets and on nearby planets, thought to have been made elsewhere in our Solar System.
Project Longshot was a conceptual interstellar spacecraft design. It would have been an unmanned probe, intended to fly to and enter orbit around Alpha Centauri B powered by nuclear pulse propulsion.
Project Daedalus was a study conducted between 1973 and 1978 by the British Interplanetary Society to design a plausible unmanned interstellar spacecraft.
Scientists may have identified the first specks of interstellar dust in material collected by the US space agency's Stardust spacecraft. The Nasa spacecraft was primarily sent to catch dust streaming from Comet Wild 2 and return it to Earth for analysis.
Scientists working on Voyager 1 are receiving further data suggesting the probe is close to crossing into interstellar space. The Nasa mission, which launched from Earth in 1977, could leave our Solar System at any time.
Japanese scientists are celebrating the successful deployment of their solar sail, Ikaros. The 200-sq-m (2,100-sq-ft) membrane is attached to a small disc-shaped spacecraft that was put in orbit last month by an H-IIA rocket.
Stephen Hawking is backing a project to send tiny spacecraft to another star system within a generation. They would travel trillions of miles; far further than any previous craft.
Spacecraft could one day navigate through the cosmos using a particular type of dead star as a kind of GPS. German scientists are developing a technique that allows for very precise positioning anywhere in space by picking up X-ray signals frompulsars.
Scientists have found the beginnings of life-bearing chemistry at the centre of the galaxy. Iso-propyl cyanide has been detected in a star-forming cloud 27,000 light-years from Earth.
Voyager 1, the most distant spacecraft from Earth, has reached a new milestone in its quest to leave the Solar System. Now 17.4bn km (10.8bn miles) from home, the veteran probe has detected a distinct change in the flow of particles that surround it.
The Pentagon's premiere research agency has chosen a former astronaut to lead a foundation that is designed to take humanity to the stars. The Defense Advanced Research Projects Agency (Darpa) and Nasa are sponsoring the project, known as the 100-Year Starship.
The human race must move to a planet beyond our Solar System to protect the future of the species, physicist Professor Stephen Hawking has warned. He told the BBC that life could be wiped out by a nuclear disaster or an asteroid hitting the planet.
Breakthrough Initiatives is a program founded in 2015 and funded by Yuri Milner to search for extraterrestrial intelligence over a span of at least 10 years. The program is divided into multiple projects.
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