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Mars colonization
On 3/4/2021 2:30 AM, Frank Scrooby wrote:
If and when colonists want to move to soil based agriculture there is a simple-ish solution to the perchlorate problem: H2O. Enough warm water will dissolve and or reactive with the perchlorates, allowing for simple mechanical methods like filtering or evaporation to remove and isolate the offending compounds. If water is not readily available in sufficient quantities good ol' bakin' and shakin' will do to. Setup a solar thermal concentrator that can heat your reaction chamber up to a few hundred odd degrees Kelvin (1000 would be a nice round number) with an extremely high atmospheric pressure (like a few Earth atmosphere equivalents). Expose soil, give it some time to get hot and shake it around to loosen up things. Then reduce the atmosphere pressure via release valve. Between the photons and the rush for lighter elements' atoms to fill the 'vacuum'. What is left behind will be dead and dry, but at least it won't be toxic anymore. And you now have a pressure vessel somewhere filled with the baked off volatiles. Any long term colony is going have uses for those. For the curious: NASA cooperated with another Organisation on a study called MAGIC (which stands for Mars AGricultural something something). It proposes an automated hydroponic greenhouse as a supplement to crew meals. Anyway. Regards Frank Came to this posting late. Threaded out of order in my news client. This makes sense, but in the short term I suspect hydroponics will be the first setup to grow food, since that is a much simpler setup and conserves precious water until adequate Martian sources can be secured. Soil isn't needed to start out. Dave |
#12
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Mars colonization
Le 01/03/2021 Ã* 01:27, Alain Fournier a écritÂ*:
SpaceX plans on building Starship to transport Mars colonist and equipment for a Mars colony. But they mostly expect other companies and organizations to handle the actual establishment of a base on Mars : habitats, greenhouses... Starship seems to be advancing well, but I haven't heard much about others working on the necessities for living on Mars. Have any of you heard about others having such plans? Alain Fournier All this "To mars" stuff is just vaporwware. Humans have no technology to send any of hem to mars now, and (luckily) they will not have it in the next 20 years. |
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Mars colonization
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#14
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Mars colonization
On Mar/8/2021 at 14:19, Jeff Findley wrote :
In article , says... Le 01/03/2021 à 01:27, Alain Fournier a écrit*: SpaceX plans on building Starship to transport Mars colonist and equipment for a Mars colony. But they mostly expect other companies and organizations to handle the actual establishment of a base on Mars : habitats, greenhouses... Starship seems to be advancing well, but I haven't heard much about others working on the necessities for living on Mars. Have any of you heard about others having such plans? All this "To mars" stuff is just vaporwware. Humans have no technology to send any of hem to mars now, and (luckily) they will not have it in the next 20 years. I personally think we'll see humans set foot on Mars in less than 20 years. Actual colonies on Mars will take a bit longer. ;-) Depending on what is your definition of a colony, the first one could very well be in less than 20 years. I personally think that in less than 20 years there will be some people living on Mars and considering Mars as their home or some people living on Mars with no planed date for their return to Earth. That is a rather weak definition of what is a colony, and even so, it is not a sure thing that it will happen within 20 years, but I think it will happen. For a stronger definition of a colony, such as a group living on Mars and capable of growing and surviving indefinitely without receiving supplies from Earth, yes I would say that will take more than 20 years. Alain Fournier |
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Mars colonization
Greetings all,
On Tuesday, March 9, 2021 at 12:14:43 AM UTC+2, Alain Fournier wrote: much snipped For a stronger definition of a colony, such as a group living on Mars and capable of growing and surviving indefinitely without receiving supplies from Earth, yes I would say that will take more than 20 years. Even with the great strides made by SpaceX I'm still somewhat cynical of the 20-ish year deadline for Humans on Mars. Let's just put it down to me having been disappointed by lack of progress in the past (NASA and Washington, I'm talking about you, and Apollo and Skylab, and the X-33 and the whole damn Shuttle program). I'm forgetting who did it but one of the historical colony leaders got where they were going, unloaded and then torched the ships (i'm not thinking of William I, it might be Cortez, or one of his contemporaries. Not necessarily smart, but it gives people a definite message: You are not going home the same way you came. The equivalent on Mars would sending your Mars Habitat to Mars and instead of sending your Mars Ascent vehicle (or Mars Return Vehicle) sending another Mars Hab packed with supplies. No MAV/MRV no way home for another 18 months (it is 18 months). Better get that hydroponic greenhouse deployed, and find the best water containing regolith to mine. Alain Fournier Regards Frank |
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Mars colonization
On Mar/11/2021 at 14:11, JF Mezei wrote :
On 2021-03-11 08:17, Jeff Findley wrote: Due to orbital mechanics, every couple of years there is a "window" when you can send spacecraft to Mars using a minimum amount of delta-V. And this is the problem. Not much point in sending fuel ahead if by the time you realise the fuel vehicle crashed, the crew are already on their way to Mars. And using different windows means a very long time between sending supplies and sending crew. No one is planning a mission the way you describe it here. You don't send fuel from Earth to Mars. You send some kind of apparatus that will make fuel on Mars using in situ resources (some mission architecture plan on sending hydrogen from Earth, but that is a small mass fraction of the oxidiser and fuel). You do that at least one launch window before sending humans. You don't send humans before your fuel factory on Mars has succeeded. Good question. I'm sure the mission planners at NASA know this answer. But, free return trajectories do exist for an earth-Mars-earth trip. Cite: https://en.wikipedia.org/wiki/Free-return_trajectory But that brings up ECLSS and food. If you have to slingshot and be autonomous for another year to get back to Earth, that means that when you leave earth, you leave with a hell of a lot of supplies and water. And it also means you need some pretty fancy ECLSS to reclaim as much as you can for water and oxygen. I have to wonder if SpaceX would take ISS system designs or make their own from scratch. In later case, they are a long way from having a Mars crewed mission. A mission profile with a free return (nearly free return) trajectory follows a path similar to a mission with a short stay on Mars. It wouldn't take a year. More like 7 months. But it is more energy expensive than a mission following a Hohmann transfer trajectory. Almost worth considering putting people in induced coma for 6 months with intravenous feeds to keep them alive followed by strong exercise regimen to bring them back to shape. That would be a whole new ballgame. Another consideration: you might need 2 starships to return from Mars. You send one from Earth to Mars solely with supplies needed for the return journey. Lands on Mars. Once the crewed vehicle comes in, they need to fuel both ships which take off and meet in space so the food/water can be transfered to the crewed vehicle. Coming from Earth, would landing and then taking off back to Earth end up requiring less food than entering Mars orbit and when the crewed vehicle takes off from Mars, it forst goes to orbit to meet with supply ship and then heads to Earth? (thsi woudld also allow refueling assuming both the tanker and the supply ship are in same orbit). A Starship should be able to take-off from Mars and go to Earth without in orbit resupply or refuel. Alain Fournier |
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Mars colonization
On Mar/11/2021 at 14:32, JF Mezei wrote :
Another question: Say you have decided your expedition will land at the equivalent of Greenwich on mars (0" longitude, 51° latitude N). How difficult is it to send multiple ships to that precise location so they land within walking distance from each other? Since Mars rotates, and since we're talking about a direct entry from your transit velocity vector doesn't that require that you arrive at atmosphere entry at a time where your destination (Greenwich) has rotated to be directly in your path? Is this accomplished with long term micro adjustements is speed for the whole transit so you arrive at the right time, or is transit speed pretty much precisely fixed due to orbital mechanics and you need to so a more significan speed adjustment as you near Mars to let Mars rotate a bit more or less so you have your target in your path ? Just curious on how much flexibility a fleet of Starships bringling supplies would have in terms of departing Earth and landing all at the same spot. Not a major issue. You make small adjustments when still far away from Mars to get at the right place at the right time. Even if you just want to reach Mars anywhere, you still do mid-course corrections because aiming for Mars from Earth would require to much precision without corrections. The fact that you want to adjust for the exact location (and therefore time of arrival) only slightly complicates the computations for your mid-course corrections. Alain Fournier |
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Mars colonization
On Thursday, Alain Fournier exclaimed wildly:
On Mar/11/2021 at 14:32, JF Mezei wrote : Another question: Say you have decided your expedition will land at the equivalent of Greenwich on mars (0" longitude, 51° latitude N). How difficult is it to send multiple ships to that precise location so they land within walking distance from each other? Since Mars rotates, and since we're talking about a direct entry from your transit velocity vector doesn't that require that you arrive at atmosphere entry at a time where your destination (Greenwich) has rotated to be directly in your path? Is this accomplished with long term micro adjustements is speed for the whole transit so you arrive at the right time, or is transit speed pretty much precisely fixed due to orbital mechanics and you need to so a more significan speed adjustment as you near Mars to let Mars rotate a bit more or less so you have your target in your path ? Just curious on how much flexibility a fleet of Starships bringling supplies would have in terms of departing Earth and landing all at the same spot. Not a major issue. You make small adjustments when still far away from Mars to get at the right place at the right time. Even if you just want to reach Mars anywhere, you still do mid-course corrections because aiming for Mars from Earth would require to much precision without corrections. The fact that you want to adjust for the exact location (and therefore time of arrival) only slightly complicates the computations for your mid-course corrections. And Perry was targeted pretty precisely, so the calculations are well understood in practice as well as in theory. /dps -- "What do you think of my cart, Miss Morland? A neat one, is not it? Well hung: curricle-hung in fact. Come sit by me and we'll test the springs." (Speculative fiction by H.Lacedaemonian.) |
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Mars colonization
On Mar/11/2021 at 15:00, Alain Fournier wrote :
On Mar/11/2021 at 14:11, JF Mezei wrote : But that brings up ECLSS and food. If you have to slingshot and be autonomous for another year to get back to Earth, that means that when you leave earth, you leave with a hell of a lot of supplies and water. And it also means you need some pretty fancy ECLSS to reclaim as much as you can for water and oxygen.Â* I have to wonder if SpaceX would take ISS system designs or make their own from scratch.Â* In later case, they are a long way from having a Mars crewed mission. A mission profile with a free return (nearly free return) trajectory follows a path similar to a mission with a short stay on Mars. It wouldn't take a year. More like 7 months. But it is more energy expensive than a mission following a Hohmann transfer trajectory. I thought I could entertain you a little more about orbital mechanics. First, let's look at the base case. You want to go to Mars with the least energy expensive trajectory. That is a Hohmann transfer orbit. From Earth, you fire your rockets to increase your speed in the direction of Earth's orbit around the sun. After that burn you are in an orbit with its perihelion at Earth's orbital altitude and aphelion at Mars' orbit. You just need to time your departure so you arrive at aphelion when Mars happens to be at that same spot. That would be a trajectory you would use for a probe, not for humans because the trip from Earth to Mars takes 259 days (8.5 months). Your trip from Earth to Mars is half of an elliptical orbit. When you want to go back to Earth, you basically do the second half of that orbit, but once again you have to time your departure so Earth is at the right spot when you arrive at perihelion. So you have to stay about 9 months on Mars (or 9 months + n*26 months). If all you want to do on Mars is to plant the Canadian flag and come back, the trip with the Hohmann transfer orbits takes you 26 months. That is a little long for the five minutes it takes to actually plant the Mexican flag. So you might want to spend a little more fuel and do it faster. To see how you could do the trip faster it helps to imagine what would happen if an inhabitant of Mercury decided to go to Mars with a Hohmann transfer orbit. The elliptical orbit with perihelion at Mercury's altitude and aphelion at Mars' altitude has a semi-major axis of about 1 astronomical unit (more like 0.95, but to keep things simple let's assume it is 1). That means that the orbital period of that orbit is about 1 year. So if you are on such an elliptical orbit and you time it so it passes near Earth, then you will pass near Earth each year. Of course, if what you want to do is go from Earth to Mars, you don't need to time it so it passes near Mercury, you just depart from Earth on this trajectory at a time which is suitable so you arrive near Mars at aphelion. Now we know that on an elliptical orbit you have higher speed near periapsis and slower speed near apoapsis. So between Earth and Mars, your angular rate will be less than the average rate over a complete orbit of one revolution per year. So if you go to Mars and then try to come immediately back with such a trajectory, when you will reach Earth's orbit, Earth will be farther away and you won't like that. What you want to do is the opposite of an Hohmann transfer orbit from Mercury. Imagine this time that you leave Earth on a Hohmann transfer orbit for Neptune. In the lower part of the orbit (e.g. between Earth and Mars) your angular rate will be higher than that of Earth. So if you go to Mars with such a trajectory, plant the Kazakh flag (for Make Benefit Glorious Nation of Kazakhstan) and immediately come back to Earth with a trajectory again with periapsis at Earth orbit and apoapsis at Neptune orbit, then you will get to Earth orbit in front of Earth, since your angular rate is higher than that of Earth. You can easily solve that problem by staying on Mars for a while after having planted the flag of China. Since Mars' orbital angular rate is lower than that of Earth, Earth will catch up during your stay. The problem with that is that you spent enough fuel to reach Neptune just to get to Mars. So if you want to stay only five minutes on Mars to plant the flag of Zimbabwe, you choose a transfer orbit with an apoapsis at X, where X is a distance from the sun somewhere between Mars (which would return you behind Earth) and Neptune (which would return you in front of Earth) such that you return at Earth (X is in fact somewhere in the asteroid belt). If you want to go even faster than that, you can choose the trajectory of an orbit with periapsis lower than Earth and apoapsis higher than X mentioned above. But that will cost you in delta-V. Now, about the free return trajectory if you decide that you don't really want to plant the flag of [choose your country here] on Mars. When you reach Mars, you have the right speed to return to Earth, your only problem is that you are not going in the right direction. But by passing by Mars, gravity will change your direction, you just need to properly choose at what altitude you do your Mars flyby. Alain Fournier |
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