Despite what Star Trek’s warp-speed journeys would have us believe, interplanetary travel is quite the hike. Take getting to Mars. Probes sent to the Red Planet by NASA and other space agencies spend about seven months in space before they arrive at their destination. A trip for humans would probably be longer—likely on the timescale of a few years.
There are a lot of things that a human crew needs to survive that robots don’t, such as food, water, oxygen, and enough supplies for a return—the weight of which can slow down a spacecraft. With current technology, NASA calculations estimate a crewed mission to Mars and back, plus time on the surface, could take somewhere between two and three years. “Three years we know for sure is feasible,” says Michelle Rucker, who leads NASA’s Mars Architecture Team in the agency’s Human Exploration and Operations Mission Directorate.
But NASA aims to shorten that timeline, in part because it would make a Mars mission safer for humans—we still don’t know how well the human body can withstand the environment of space for an extended period. (The record for most consecutive days in space is 437.) The agency is investing in projects to develop new propulsion technologies that might enable more expeditious space travel.
A crooked path to Mars
In a science-fictional world, a spacecraft would blast off Earth and head directly to Mars. That trajectory would certainly make for a speedier trip. But real space travel is a lot more complicated than going from point A to point B.
“If you had all the thrust you want, you could ignore the fact that there happens to be gravity in our universe and just plow all the way through the solar system,” says Mason Peck, a professor of astronautics at