Editing Interstellar travel (section)

==== Interstellar ramjets ====
In 1960, [[Robert W. Bussard]] proposed the [[Bussard ramjet]], a fusion rocket in which a huge scoop would collect the diffuse hydrogen in interstellar space, "burn" it on the fly using a [[proton–proton chain reaction]], and expel it out of the back. Later calculations with more accurate estimates suggest that the thrust generated would be less than the drag caused by any conceivable scoop design.{{citation needed|date=May 2016}} Yet the idea is attractive because the fuel would be collected ''en route'' (commensurate with the concept of ''energy harvesting''), so the craft could theoretically accelerate to near the speed of light. The limitation is due to the fact that the reaction can only accelerate the propellant to 0.12c. Thus the drag of catching interstellar dust and the thrust of accelerating that same dust to 0.12c would be the same when the speed is 0.12c, preventing further acceleration.