How long does it take to get to Mars? Yet another in a long list of excellent questions. The time to travel to Mars is approximately 214 days (Earth days of course). The answer is simple enough and the question allows us to explore Hohmann transfer orbits.
First off, it would take quite a bit less time if we had the technology to carry enough fuel to travel directly. Take off would not be so fuel intensive, it would be slowing down enough to enter Martian orbit. Trajectory adjustments and braking maneuvers would use too much fuel to allow for a return to Earth. So, Hohmann transfer orbits are used.
A Hohmann transfer orbit is an elliptical orbit used to transfer between two coplaner, circular orbits. It typically requires two engine impulses to move a spacecraft on and off the transfer orbit. The maneuver is named after Walter Hohmann who published the first description of the maneuver in 1925. As it applies directly to the problem of a spaceflight from Earth to Mars, a Hohmann transfer would look like this: The spacecraft would have a certain velocity from its initial orbit around Earth. At the end of the transfer orbit(which is around the Sun) the craft will need another velocity to enter Mars orbit. The velocity to enter Mars orbit will have to be less than the velocity needed to continue in the transfer orbit, so the craft will have to decelerate enough for Martian gravity to capture it. Relatively small bursts from high thrust engines are required to alter the velocity; therefore, saving fuel and lowering the capacity as well as the weight requirements of the spacecraft. Calculating fuel and burst durations are the simple parts. Timing the launch of the craft so that it exits the transfer orbit at the same time as Mars is arriving in that part of the orbit is the trick. As you can see, the narrow launch window becomes the trick.
Using a nuclear powered rocket would significantly shorten the trip, since Hohmann transfer orbits would be bypassed. The more direct route would cut the time from a little over 7 months to about 4 months. This time savings is crucial if humans are to ever explore the planet. It is hard to imagine nearly a year in space, let alone the nearly 2 years it would take using current combustible fuel technology.
Currently, the answer to ”how long does it take to get to Mars?” is about 214 days or a little over 7 months. Scientists are constantly exploring ways to travel between planets in a more efficient way. Who knows when it will be possible to visit a planet and return in less than a few months.
This detailed article explains how difficult it is to land on Mars. And then, there’s always the Mars curse. Why have so many missions to Mars failed?
Want to learn more about orbits? NASA has information about interplanetary orbits. Here’s a Wikipedia article about the nuclear thermal rocket.
Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars. We also discussed orbits in Episode 84: Getting Around the Solar System.
Sources:
http://image.gsfc.nasa.gov/poetry/venus/q2811.html
http://www-istp.gsfc.nasa.gov/stargaze/Smars1.htm
http://www2.jpl.nasa.gov/basics/bsf4-1.php
