Human space exploration has had its share of successes, with our probes going far into interstellar space. But humans themselves haven’t made it past the Moon yet. If we're ever to find other Earth-like planets or alien civilizations we have to be able to traverse the immense span of space much quicker. One potential invention that could make this a reality is a theoretical space drive known as the “Bussard collector” or “Ramjet propulsion”. A recent physics paper published in the journal Acta Astronautica considers the feasibility of this technology.
In broad terms, a Bussard ramjet for a spacecraft would work by using enormous magnetic fields to trap hydrogen protons found in interstellar space, compressing the reactive mass into a progressively constricted magnetic field until thermonuclear fusion occurs. The magnetic field then directs the energy into rocket exhaust, providing thrust.
The thrust from the jet would theoretically allow the ship to reach relativistic speeds, while carrying no onboard fuel. The concept is based on the presence of high-energy particles in space, with hydrogen especially existing in an ionized state that can be affected by magnetic fields. If one could “scoop” up this hydrogen, as Bussard imagined, it could be channeled into a reactor, where the exhaust from the reactor would provide the thrust necessary for high-speed travel. As science writer Ella Anderson notes, a space drive like that would make it possible for humans to reach its nearest star system in under 4 years, and the nearest galaxy in less than 30.
What’s also remarkable is that such a spacecraft would not need to be carrying fuel, instead, it'd feed on the refuse of the cosmos to propel itself. However, it is likely it would need a sizable amount of initial fuel to reach the speeds necessary for the collection of enough hydrogen to power its engine.
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