The launch of Cassini, on October 15, 1997. This spectacular streak shot was taken from Hangar AF on Cape Canaveral Air Force Station, with a solid rocket booster retrieval ship in the foreground. For all of our history on Earth, the only way we’ve ever reached space is through the use of chemical-based fuels. (NASA)

Could We Achieve Interstellar Travel Using Only Known Physics?

It doesn’t have to be a science-fiction dream.

For as long as human beings have been watching the night sky, we’ve dreamed of visiting other worlds and truly seeing what’s out there in the Universe. While our chemical-based rockets have taken us to a myriad of planets, moons, and other bodies in the Solar System, the farthest spacecraft ever launched by humanity — — is only 22.3 billion kilometers (13.9 billion miles) from Earth: just 0.056% of the distance to the closest known star system. With current technology, it would take close to 100,000 years to travel to another star system.

But there’s no need to restrict ourselves to doing things the way we’re doing them right now. With the right technology, we could vastly improve how efficient it is to get a large-payload mass, perhaps even one that carried humans on board, to unprecedented distances across the Universe. In particular, there are four technologies that have the potential to take us to the stars on much shorter timescales. Here’s how.

A nuclear-powered rocket engine, preparing for testing in 1967. This rocket is powered by Mass/Energy conversion, and is underpinned by the famous equation E=mc². Although this concept has never led to a successful rocket, it could be the future of interstellar space travel. (ECF (EXPERIMENTAL ENGINE COLD FLOW) EXPERIMENTAL NUCLEAR ROCKET ENGINE, NASA, 1967)

1.) The nuclear option. At this point in human history, every rocket we’ve ever…