Well on the timing, it took the entire Gemini series of space missions and then the first 10 missions of the Apollo before they got to the Moon. Mars is far harder than the Moon. I think we've done the equivalent of the Gemini for Mars so far but not the equivalent of the Apollo precursors.
So - would expect perhaps 10 manned missions precursors before a successful Mars mission. And as for Apollo towards the end several of those would be the same duration as the Mars mission.
That could be as quickly as 10 years if you had a truly massive program behind it as for Apollo. Or - perhaps a bit more as the precursor full length missions would be two or three years each - especially if they turned up issues (which is why you do them of course) and you needed to do several before you end up with a situation that brings the crew back alive at distance of Mars - then that could easily add another decade.
Leave it to Mars One or even SpaceX - I think several decades. There are several major new technologies needed, not just able to deliver mass to Mars, but to do with keeping crew alive, and new spaceship to be tested and to be shown reliable enough for humans to stay in for years on end.
I think mission to Mars orbit is the way to go rather than to the surface so we don't contaminate it with Earth life when we don't know what is there yet - as some of you may know from my other answers here.
And I think for such an expensive mission - don't think colonization makes sense at all as Mars is not a great place to colonize, is not a useful escape at all from asteroid impact on Earth and not a good place for humans to live.
The only way we could make places in space that are worth colonizing is if they could be huge, low maintenance structures - like the Stanford Torus or the O'Neil cylinder - where you build your houses and live your lives inside - if the entire structure can be reasonably low maintenance - then inside it's as pleasant and easy to live as living in the tropics.
But to live on a surface or in small habitats - where each habitat requires multiple tons per square meter pressure, and meters of cosmic radiation shielding - can't see that working economically or practically - always far easier to build a house on Earth than one of those. And big city domes on a planet or moon surface aren't that practical especially when you realize it would also need to be covered all over with a few meters thickness of cosmic radiation shielding. While in space - is reasonably practical - could be done even with 1970s technology so we could do it now.
But for a fair while into future I think it will, and should be, small settlements a bit like Antarctica. And those would be driven by scientific interest - at distance of Mars. Doubt if you could get enough paying tourists - at least until you get transit times down into weeks instead of years to go there and back.
And main thing that would really drive scientific interest and get countries to want to do mega expeditions to Mars - and make it economically worthwhile for the returns - would be discovery of interestingly different life on Mars. Which would mean you need to keep it contamination free for longer, possibly indefinitely - but makes it a far more interesting planet -which you can visit via virtual reality - eventually things like the Virtuix Omni treadmill and the Oculus rift - to explore from orbit - actually in many ways a more direct experience of Mars than you could get with a spacesuit and our limited vision capabilities in the dull light of Mars - and limited mobility - unable to breath the air or even expose skin to it - and having to cart tons of equipment around wherever you go just to stay alive - instead in orbit explore mars with fast agile lightweight telerobotic avatars. I think that's the future for Mars if it does turn out to be biologically fascinating - as I think is quite likely to happen.
Oh, and though it sounds good in a speech - really - I don't think it is wise to do things in space because they are hard. Not if you interpret that as doing the most dangerous of two options when you have the choice. Space missions are dangerous enough already. We should be adventurous but also cautious or we will just get deaths as could have happened on Apollo many more times if they had been faster and more reckless. They were quite cautious and careful and we should be too.
So - I'd definitely do a lot more at the distance of the Moon before sending humans to Mars. Is a major step up from LEO which we've been doing for decades, and a long mission to the Moon is far harder than the few days of Apollo - and lots of interesting stuff to do there with new understanding of the Moon and we haven't yet sent a good science mission to the Moon except Apollo 17 and that was a single geologist - only trained scientist to go to the Moon and study it close up. With water at poles and many other new things to discover, plenty to do there - in orbit in L2 would be best way as a precursor for Mars because the isolation makes it very similar - and scientifically useful also - but that's going a bit afield here to go into details, but - need to do long missions close to Earth first and Moon, especially L2 is an ideal way to do that also of great interest in its own right.
So - would expect perhaps 10 manned missions precursors before a successful Mars mission. And as for Apollo towards the end several of those would be the same duration as the Mars mission.
That could be as quickly as 10 years if you had a truly massive program behind it as for Apollo. Or - perhaps a bit more as the precursor full length missions would be two or three years each - especially if they turned up issues (which is why you do them of course) and you needed to do several before you end up with a situation that brings the crew back alive at distance of Mars - then that could easily add another decade.
Leave it to Mars One or even SpaceX - I think several decades. There are several major new technologies needed, not just able to deliver mass to Mars, but to do with keeping crew alive, and new spaceship to be tested and to be shown reliable enough for humans to stay in for years on end.
I think mission to Mars orbit is the way to go rather than to the surface so we don't contaminate it with Earth life when we don't know what is there yet - as some of you may know from my other answers here.
And I think for such an expensive mission - don't think colonization makes sense at all as Mars is not a great place to colonize, is not a useful escape at all from asteroid impact on Earth and not a good place for humans to live.
The only way we could make places in space that are worth colonizing is if they could be huge, low maintenance structures - like the Stanford Torus or the O'Neil cylinder - where you build your houses and live your lives inside - if the entire structure can be reasonably low maintenance - then inside it's as pleasant and easy to live as living in the tropics.
But to live on a surface or in small habitats - where each habitat requires multiple tons per square meter pressure, and meters of cosmic radiation shielding - can't see that working economically or practically - always far easier to build a house on Earth than one of those. And big city domes on a planet or moon surface aren't that practical especially when you realize it would also need to be covered all over with a few meters thickness of cosmic radiation shielding. While in space - is reasonably practical - could be done even with 1970s technology so we could do it now.
But for a fair while into future I think it will, and should be, small settlements a bit like Antarctica. And those would be driven by scientific interest - at distance of Mars. Doubt if you could get enough paying tourists - at least until you get transit times down into weeks instead of years to go there and back.
And main thing that would really drive scientific interest and get countries to want to do mega expeditions to Mars - and make it economically worthwhile for the returns - would be discovery of interestingly different life on Mars. Which would mean you need to keep it contamination free for longer, possibly indefinitely - but makes it a far more interesting planet -which you can visit via virtual reality - eventually things like the Virtuix Omni treadmill and the Oculus rift - to explore from orbit - actually in many ways a more direct experience of Mars than you could get with a spacesuit and our limited vision capabilities in the dull light of Mars - and limited mobility - unable to breath the air or even expose skin to it - and having to cart tons of equipment around wherever you go just to stay alive - instead in orbit explore mars with fast agile lightweight telerobotic avatars. I think that's the future for Mars if it does turn out to be biologically fascinating - as I think is quite likely to happen.
Oh, and though it sounds good in a speech - really - I don't think it is wise to do things in space because they are hard. Not if you interpret that as doing the most dangerous of two options when you have the choice. Space missions are dangerous enough already. We should be adventurous but also cautious or we will just get deaths as could have happened on Apollo many more times if they had been faster and more reckless. They were quite cautious and careful and we should be too.
So - I'd definitely do a lot more at the distance of the Moon before sending humans to Mars. Is a major step up from LEO which we've been doing for decades, and a long mission to the Moon is far harder than the few days of Apollo - and lots of interesting stuff to do there with new understanding of the Moon and we haven't yet sent a good science mission to the Moon except Apollo 17 and that was a single geologist - only trained scientist to go to the Moon and study it close up. With water at poles and many other new things to discover, plenty to do there - in orbit in L2 would be best way as a precursor for Mars because the isolation makes it very similar - and scientifically useful also - but that's going a bit afield here to go into details, but - need to do long missions close to Earth first and Moon, especially L2 is an ideal way to do that also of great interest in its own right.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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