People have already spent over a year in space. Russian cosmonaut Valery Polyakov holds the record for the longest continuous time in space, at 438 days. This is not a problem.
Very few people have logged the flight time he has, in fact, only about a dozen people have logged the same amount of
cumulative flight time as would be required for a Mars mission, let alone
continuous flight time!
We are talking about pushing the limits of human endurance, and requiring at least six people to be able to achieve that, more would need to be sent as backup.
And it's possible to use teathered masses to create artificial spin gravity. This hasn't been tried yet, but 20 years is more than enough time to work it out.
We haven't even got plans to deploy that in Earth Orbit within the next ten years afaik.
Why do you think so? We're talking about over 20 years here, and most of the technology already exists.
Hmm, no it doesn't. We can recycle water and air fairly well, but Mir and the ISS were still resupplied with both. There is a very limited resupply option on a Mars trip, so basic life support systems need to be improved vastly or;
Clearly a very large heavy-lift rocket would be needed,
A vast rocket would be needed to take a crew of six, and everything they need to survive. How much water does a person need for a year in space? I have various hobbies which require me to carry everything I need for a period of time. Once you start monitoring your consumption of basics like water, or notice the degradation of lifestyle once you can't just turn on a tap and take a shower you understand the enormous difficulties of surviving in inhospitable terrain.
Resupply, is limited, because we just don't have a good record of landing robotic missions on Mars, just check out the failure rate. Not good if you are relying on those packages for basic survival.
but it only took about 6 years to develope and build the Saturn 5 from initial concept to first launch.
And at present a replacement for the Shuttle, Orion, is scheduled to send humans back to the Moon, by 2020. You really think firstly that we are going to hit that deadline, and then achieve Mars just a decade later? Even with International co-operation that sounds doubtful to me.
A heavy-lift rocket in the same class as the Saturn V could launch direct-to-mars flights in one go, especially if nuclear engines (that we already know how to build) are used.
Nuclear engines? That have not been built, tested for such payloads, or type approved for manned flight, ... hmmm, keep chuffing on that pipe.
It would just be a matter of sending a few unmanned cargo shipments ahead of the crew so that they have something to live in/eat/etc when they get there.
Like I said earlier, we don't have a good record of landing robotic missions on Mars, so resupply missions would have to have that factored in.
Running a nuclear reactor isn't any harder than doing anything else in space. The nuclear reactor is a non-issue.
Hand waving over the detail doesn't take it away. Take something we know about, and extrapolate, .. say, a Nuclear Submarine. It takes up about half the volume of a submarine, requires a fairly substantial crew, and can use sea water as a coolant. Now, take that to Mars, it has to be far more compact, self contained, use minimal coolant, and be able to be staffed by just six people. That rather limits the size, and utility.
Both Russia and the U.S. have already launched nuclear reactors into space that ran for years without ever being serviced by anyone.
Rather simple nuclear thermocouples, with very limited output. IIRC of the order of tens to a few hundred watts in general, with the odd large version having limited lifespan. There are limits as to how much fissionable material you are allowed to launch on manned missions, btw, and limits on how much toxic metal, I recall having to dispose of a cryostat once because it used beryllium and was no longer flight worthy.
The reactor would probably be launched in one piece, ready to go. The crew would simply have to plug it in and hit the "start" button.
Would Geordie La Forge, or Commander Data do that?