Bussard ramjet

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 (ranging from kilometers to many thousands of kilometers in diameter); 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. The Bussard ramjet was proposed in 1960 by the physicist Robert W. Bussard. The concept was popularized by Poul Anderson in his novel Tau Zero, Larry Niven in his Known Space series of books, Vernor Vinge in his Zones of Thought series, and Carl Sagan, as referenced in the television series and book Cosmos.