Mars is, if you have a low energy trajectory, like a minimum energy trajectory is about 6 months. I think that can be compressed down to about 3 months, and it gets exponentially harder as you go lower than that - 3 to 4. It's important to actually be at that level because then you can send your spaceship to Mars and then bring it back on the same orbital synchronization. Earth and Mars synch up every two years and then they're only kinda in synch for about 6 months. Then, ya know, they're really too far apart. So you've got to be able to go there and back in one go. That's important for making the cost of traveling to Mars an affordable amount.
What I don't understand is why it is so important to get your spacecraft immediately, vs. getting it on the next cycle. In the latter case you still get your spacecraft back, but only later, so you need maybe 2x as many spacecraft. Sounds equivalent to taking a 50% payload penalty, for example.
Quote from: meekGee on 12/13/2013 03:16 amWhat I don't understand is why it is so important to get your spacecraft immediately, vs. getting it on the next cycle. In the latter case you still get your spacecraft back, but only later, so you need maybe 2x as many spacecraft. Sounds equivalent to taking a 50% payload penalty, for example.I don't get that either. Especially when you consider the massive delta-v penalty of trying to get there and back in a single window.
I'd say it's not about the spacecraft, but the people inside it. 6 months is a long, long time in tight confines, and the radiation and zero-g are going to make a mess of people by the time they get to Mars.
My guess is that he's been hacking at this for how many years now? He probably got further along than we did in the last 20 minutes.
I'd say it's not about the spacecraft, but the people inside it. 6 months is a long, long time in tight confines, and the radiation and zero-g are going to make a mess of people by the time they get to Mars.faster means less exposure to radiation, and less zero-G bone loss/muscle loss etc. remember these are not intended to be high-function astronauts (at least: not when it comes to colony time). they're not going to deal with long space travel as well as hand-picked astros.there are going to be people going to Mars AND returning - not necessarily the same people in the same window, but you do need the fast transit in both directions.
Quote from: starsilk on 12/13/2013 03:28 amI'd say it's not about the spacecraft, but the people inside it. 6 months is a long, long time in tight confines, and the radiation and zero-g are going to make a mess of people by the time they get to Mars.Nope, he specifically says the fast transit is to get the spacecraft back in the same window to reduce the cost. Don't tell me you didn't even read the transcript I painstakingly typed out for you.
Quote from: starsilk on 12/13/2013 03:28 amI'd say it's not about the spacecraft, but the people inside it. 6 months is a long, long time in tight confines, and the radiation and zero-g are going to make a mess of people by the time they get to Mars.faster means less exposure to radiation, and less zero-G bone loss/muscle loss etc. remember these are not intended to be high-function astronauts (at least: not when it comes to colony time). they're not going to deal with long space travel as well as hand-picked astros.there are going to be people going to Mars AND returning - not necessarily the same people in the same window, but you do need the fast transit in both directions.That's true, but if that was the primary consideration, you could optimize for an even faster transit, if you're willing to let the spacecraft wait at Mars for another cycle.There's more to this story...
Quote from: meekGee on 12/13/2013 03:35 amQuote from: starsilk on 12/13/2013 03:28 amI'd say it's not about the spacecraft, but the people inside it. 6 months is a long, long time in tight confines, and the radiation and zero-g are going to make a mess of people by the time they get to Mars.faster means less exposure to radiation, and less zero-G bone loss/muscle loss etc. remember these are not intended to be high-function astronauts (at least: not when it comes to colony time). they're not going to deal with long space travel as well as hand-picked astros.there are going to be people going to Mars AND returning - not necessarily the same people in the same window, but you do need the fast transit in both directions.That's true, but if that was the primary consideration, you could optimize for an even faster transit, if you're willing to let the spacecraft wait at Mars for another cycle.There's more to this story...I think the "more" is that the MCT can be used on the Earth-side for more regular launch operations.
QG - can you copy over more data on dV requirements for different transit times?
Quote from: Robotbeat on 12/13/2013 03:40 amQuote from: meekGee on 12/13/2013 03:35 amQuote from: starsilk on 12/13/2013 03:28 amI'd say it's not about the spacecraft, but the people inside it. 6 months is a long, long time in tight confines, and the radiation and zero-g are going to make a mess of people by the time they get to Mars.faster means less exposure to radiation, and less zero-G bone loss/muscle loss etc. remember these are not intended to be high-function astronauts (at least: not when it comes to colony time). they're not going to deal with long space travel as well as hand-picked astros.there are going to be people going to Mars AND returning - not necessarily the same people in the same window, but you do need the fast transit in both directions.That's true, but if that was the primary consideration, you could optimize for an even faster transit, if you're willing to let the spacecraft wait at Mars for another cycle.There's more to this story...I think the "more" is that the MCT can be used on the Earth-side for more regular launch operations.Maybe.Also, in my mind, I always see a prolonged "equipment only" campaign before there's a people campaign.However, Elon may be thinking that each MCT is 95% equipment and 5% people, and they build the infrastructure as they get there (well, each group build the infrastructure hauled over by the previous MCT) - and so the "tie breaker" is significant.QG - can you copy over more data on dV requirements for different transit times? Also - isn't there another transfer orbit (not as low-dV as Hohmann) that is open in the "other" years?
I really wonder if the payloads actually need to travel along with the MCT.