in early 2030s. Just my amateurish opinin.
1)The 1st chinese unmanned mars probe could be launched in 2013
2)Chinese Manned moon mission 2020
3)Chinese Manned mars mission early 2030s.
There will be a min energy launching windows around that time.
A martian spaceship could be module assembled in LEO using CZ--9 rockets.
The unknown is whether nuclear propulsion could be used.
I think an all chemical rocket ship is feasible but it will be big in LEO.
Could unmanned propellent plants be sent to mars to make propellent for the home trip?
One of the considerations when traveling to Mars from Earth or vice versa is that the energy needed to transfer between their orbits hits a low point every 26 Earth months (2 years and 2 months). So missions are typically planned to coincide with one of these windows. In addition, the energy needed in the low-energy windows varies on roughly a 15 year cycle. The easiest windows only need half the energy of the peaks.
In the 20th century, there was a minimum in the 1969 and 1971 launch windows and another low in 1986 and 1988, then the cycle repeated...."