Mars: Now's a good time to go

Fifty years ago the first “moonwalkers” were heralded as heroes. But in an age of space tourism the Moon is more holiday destination that unfathomable fantasy. Nowadays there are bigger fish to fry, one giant red one in particular, I am of course talking about Mars.

This week, NASA confirmed the launch date, 26/11/11,  for their next ambitious mission to Mars, Curiosity, and by no means is this date a result of chance. There is in fact an optimum time to send a probe to the red planet.

Every 780 days, a minimum-energy launch window opens. It is the perfect time to launch a rocket to Mars as it requires the least amount of fuel to propel the rocket on its course. These launch windows are based on the Hohmann transfer orbit, in this case, that is when the earth is at its closest point to the sun during orbit and Mars at its furthest.

The spacecraft must be propelled around the sun and the Hohmann transfer orbit calculates that the spacecraft will meet the trajectory of the Martian orbit, eventually catching up with it.

Unfortunately, the opportunity for a manned flight to Mars doesn't pop up so frequently. The best time to send humans to Mars is when the planet is closest to Earth, something that only happens once every 15-17 years.