Martian Vacation, Part One (Opposition-class Missions)

Planning a vacation to Mars? Wondering when is the best time to go? Here’s one option:

Once every 26 months, while Earth and Mars are on the same side of the Sun, the two planets line up just right for a launch. Although Mars is not necessarily in opposition at this time, it’s close to it, so your flight is known as an opposition-class mission.

Your journey will take several months (exact time estimates vary depending on spaceship design and other mission parameters). Keep in mind that during your voyage, both Earth and Mars continue moving through their orbits. In fact, Earth will rapidly move ahead of you, so you’ll only be able to stay on the surface of Mars for a short time before you have to come home. For this reason, opposition-class missions are also known as short-stay missions.

On your return flight, Earth is still moving away from you, so to catch up, your spacecraft will have to cut through the inner Solar System, swinging in a wide arc around the Sun, possibly utilizing a difficult and dangerous gravity assist maneuver at Venus.

Opposition-class missions aren’t the only way to get to Mars, but they do offer some advantages:

  • You get to Mars faster.
  • You get home faster.
  • Some argue the trip is safer. Since you spend less time in space, you should suffer less radiation exposure and less bone-loss due to zero-gravity.

However, there are some noteworthy disadvantages too:

  • Opposition-class missions require a whole lot of fuel, significantly more than alternative conjunction-class missions.
  • You only get to spend a few weeks on Mars. Depending again on mission parameters, you might get a little over a month.
  • About that safety thing… some argue opposition-class missions aren’t so safe after all because more things can go wrong, especially during your return flight.

I’d guess that the first manned mission to Mars may well be opposition-class. I think humanity might prefer to dip its toe in the water, so to speak, with a short-stay mission.

Subsequent missions (and vacations) will probably be conjunction-class, long-stay missions, for reasons that we’ll examine on Wednesday.

P.S.: It’s difficult to find reliable information about opposition- and conjunction-class missions online, so for further research, I recommend The Case for Mars by Robert Zubrin. Zubrin, a former aerospace engineer for Lockheed Martin and founder of the Mars Society, lays out one of the most believable and compelling plans for Mars exploration and eventual colonization that I’ve ever seen. If you have any interest in going to Mars (or writing science fiction about Martian colonists), you should read Zubrin’s book.

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Today’s post is part of Mars month for the 2015 Mission to the Solar System.

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