18-month Mars500 mission has begun

[PeZook]

If anything, the travel time is not significantly longer.
Columbus took about 8 months to reach America (IIRC). Longer sea travels were nothing extraordinary later on.
While this might be longer, if you can mange a year you should manage 18 months.

Whalers usually spent 2 years or so at sea per cruise, with crews that could be as small as 20 men, and without military discipline. It's entirely doable, but I agree more experiments is better, since it giver us more data to analyze - especially since they took some pains to recreate the probable environment of a Mars mission.

I fail to really see the point in this experiment for a couple of reasons.

This has been done before. (biosphere experiment + others)

This is being done every day at various locations. (submarines + artic /antarctic locations)

What they are trying to discover is already known? Isn't it?

This is the same as moon hoax conspiracy theorists going "Hey, they already knew there was water on the Moon...what's the point of smashing probes into it? They already know! They must be bullshitting in some way, it doesn't make any sense!!!".

You didn't make the final leap, but it's the same mentality. Additional data is always good.

[Cykeisme]

Oops, just realized this experiment was going to be performed terrestial with normal surface gravity.

Wondering, it's outside of the scope of this experiment, but what sort of acceleration will a Mars-bound craft be travelling at? Is the burn likely to be constant?

[Junghalli]

Wondering, it's outside of the scope of this experiment, but what sort of acceleration will a Mars-bound craft be travelling at? Is the burn likely to be constant?

Doing a very quick napkin calc, a day of acceleration at 1 G gets you sufficient speed to reach Mars in 24 hours (when it's at its closest approach to Earth), at a speed of 847 km/s. That's quite insane for most remotely presently feasible rockets. Realistically almost certainly either they'd do short burns with most of the trip coasting in microgravity or they'd do long burns with very low thrust rockets at a small fraction of 1 G. Either way they wouldn't experience anything remotely close to Earth normal gravity for most of a multi-month trip.

This is not counting the possibility of using centrifugal gravity.

[Sky Captain]

I think it is most likely the Mars spacecraft will have some sort of highly efficient electric rocket propulsion to reduce time in transit and needed propellant mass to be launched in LEO so it will remain under constant, but very low thrust all the time.