A concept spacecraft designed to carry humans and cargo from Earth to Mars in mere days could help mankind colonize the stars, but there’s just one problem: it never stops.

The most difficult problem of traveling through space is when the craft accelerates and decelerates, especially if there’s a lot of cargo or people traveling around the solar system.

That’s why the Solar Express space train engineers designed their craft to run-nonstop between designated stops on planets and space stations, according to ImaginActive.

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