Wernher von Braun would be disappointed that we still haven’t landed a manned mission on Mars, but Mars is hard — and expensive:
In his novel [Project Mars], von Braun figured that a Mars expedition would cost US $2 billion — about $18 billion in today’s dollars. By 1989, NASA estimated such a trip would come to half a trillion dollars; if you correct that figure for inflation, you get the current U.S. fiscal stimulus package, give or take a hundred million.
It’s a long trip:
If going to the moon is a day hike, going to Mars is the Lewis and Clark expedition — a journey too long and too complex to carry everything that’s needed. Earth and Mars ride along in their concentric orbits, getting within striking distance of each other only for a brief window every two years. The shortest one-way trip, using conventional chemical propulsion, would take six months. If you include the time spent on Mars waiting for the two planets to move back into optimal alignment and also the trip home, the total mission would last at least two and a half years. The crew would have to endure extremes of boredom, isolation, and radiation, and they would require a vast amount of fuel and rations packed into a vessel sturdy enough to shield them from the harshness of space. Simply landing a spacecraft safely on a planet with an atmosphere and substantial gravity poses stunning challenges. And then there’s the matter of keeping the crew alive on the Martian surface.
The list of challenges is long and sobering, and it starts with propulsion:
Chemical rockets are only marginally capable of getting people to Mars and back, but the main alternative, the plasma drive, is at least a couple of decades away from the day when it’ll be ready to ferry folks to that red dot in the sky.Even after the propulsion problem is solved, there are at least five other really big ones: cosmic rays, muscle and bone loss, psychological stress, landing on the planet, and feeding the crew for the long haul. All of those challenges are harder with chemical rockets, because a chemically fueled trip would last much longer than one with a more advanced propulsion technology.