Quote from: cppetrie on 04/01/2018 08:01 pm And to your point 3T scanners aren’t even state of the art. 5T and 7T scanners are being used in research hospitals. They aren’t used routinely mostly because their greater expense isn’t worth it for routine clinical needs and also because those field strengths cause disorientation to patients that usually require sedation.Most MRI machines used in hospitals are slightly under several hundred kilometers in diameter.
And to your point 3T scanners aren’t even state of the art. 5T and 7T scanners are being used in research hospitals. They aren’t used routinely mostly because their greater expense isn’t worth it for routine clinical needs and also because those field strengths cause disorientation to patients that usually require sedation.
Quote from: speedevil on 04/01/2018 08:16 pmYou get very, very large currents flowing in the core, which act to cancel your imposed field essentially 'forever'.Not really. You charge it up over decades. That’s slow enough that the core doesnt cancel out the field. Additionally, core is above the curie point.
You get very, very large currents flowing in the core, which act to cancel your imposed field essentially 'forever'.
Quote from: Robotbeat on 04/01/2018 08:18 pmQuote from: speedevil on 04/01/2018 08:16 pmYou get very, very large currents flowing in the core, which act to cancel your imposed field essentially 'forever'.Not really. You charge it up over decades. That’s slow enough that the core doesnt cancel out the field. Additionally, core is above the curie point.Skin effect means 'slow enough' is many, many thousands of years, not decades unfortunately.
I doubt such a calculation, although I haven’t had time to calculate it myself (Mars core is about 10^6 S/m). But thousands of years is still just fine for stopping erosion. Beefing up the atmosphere is a much greater priority and it’ll make a much bigger difference in surface radiation levels than the magnetic field would.
Quote from: Robotbeat on 04/01/2018 08:43 pmI doubt such a calculation, although I haven’t had time to calculate it myself (Mars core is about 10^6 S/m). But thousands of years is still just fine for stopping erosion. Beefing up the atmosphere is a much greater priority and it’ll make a much bigger difference in surface radiation levels than the magnetic field would.That is - when you turn on your coil around Mars, you induce an equal and opposite current in the surface of the molten core of Mars, which almost perfectly cancels out your induced field.It takes longer than thousands of years for this cancellation to go away and your imposed field to be visible.(Local fields that don't touch the core are not affected)
Quote from: meekGee on 04/01/2018 12:51 pmQuote from: john smith 19 on 04/01/2018 09:49 amQuote from: Alkan on 04/01/2018 02:24 amSo, I'm interested in predicting some of the details of his colony. Each phase is looser and more speculative.Phase I: Fuel ProductionThe methane fuel will be created by the Sabatier reaction using CO2 and water. Welcome to the site. You're behind the curve here. Substantial Methane deposits have been found. JS19: Methane deposits? I missed that.Are they usable? What form do they take? Do you have references?-----ABCD: Always Be Counting DownElon Musk literally said they're going to use CO2 at ITS presentation, so that comment about me being behind is kind of funny. It's probably easier to find a lot of water.https://www.youtube.com/watch?v=8unI6KHAocU?t=14m43sThe presentation on radiation on Mars was released before Elon Musk's Mars architecture was outlined. It will be an issue, though I don't think Elon Musk seems to think of it as such a big deal. It is a bigger deal than I think that Elon Musk thinks, but the risk of increased cancer is just going to be part of it.
Quote from: john smith 19 on 04/01/2018 09:49 amQuote from: Alkan on 04/01/2018 02:24 amSo, I'm interested in predicting some of the details of his colony. Each phase is looser and more speculative.Phase I: Fuel ProductionThe methane fuel will be created by the Sabatier reaction using CO2 and water. Welcome to the site. You're behind the curve here. Substantial Methane deposits have been found. JS19: Methane deposits? I missed that.Are they usable? What form do they take? Do you have references?-----ABCD: Always Be Counting Down
Quote from: Alkan on 04/01/2018 02:24 amSo, I'm interested in predicting some of the details of his colony. Each phase is looser and more speculative.Phase I: Fuel ProductionThe methane fuel will be created by the Sabatier reaction using CO2 and water. Welcome to the site. You're behind the curve here. Substantial Methane deposits have been found.
So, I'm interested in predicting some of the details of his colony. Each phase is looser and more speculative.Phase I: Fuel ProductionThe methane fuel will be created by the Sabatier reaction using CO2 and water.
Quote from: speedevil on 04/01/2018 09:22 pmThat is - when you turn on your coil around Mars, you induce an equal and opposite current in the surface of the molten core of Mars, which almost perfectly cancels out your induced field.It takes longer than thousands of years for this cancellation to go away and your imposed field to be visible.(Local fields that don't touch the core are not affected)If it really took thousands of years to become negligible, then all you would have to do is turn the magnet on for a split second and the current induced in the core would keep up a strong enough magnetic field for a long time.It's kind of absurd, actually. Changing magnetic fields induce currents, steady magnetic fields do not. Currents decay almost instantaneously if nothing is driving it.https://en.wikipedia.org/wiki/Maxwell%27s_equations#Formulation_in_SI_units_conventionThe third one, Maxwell–Faraday equation. The second one is easier to understand (DelXE=-∂B/∂t).
That is - when you turn on your coil around Mars, you induce an equal and opposite current in the surface of the molten core of Mars, which almost perfectly cancels out your induced field.It takes longer than thousands of years for this cancellation to go away and your imposed field to be visible.(Local fields that don't touch the core are not affected)
Modifying the local field is of course possible.
Without being driven and with an extremely high resistivity (which is NOT resistance), each volume element of the planet makes up a resistor. The thing is, there's not even a closed loop inside Mars to induce a current in. Any established potential inside of the planet is what would cause the induced current in the first place, and there isn't a loop - the charge is free to move across the planet's presumably metal core. You need to be thinking about concepts like current density and resistivity before you're thinking about current and resistance.
Sorry to interrupt your doomsaying, but you can shield a habitat on the surface to lower than Earth levels of radiation. Heck, a big enough habitat with enough floors will have enough shielding in the structure itself that the lower levels will have Earth-like radiation levels. That’s where children and pregnant families can hang out.
Hi I couldn't find the mars agriculture thread for some reason.. just dumping this here.
People forget we actually have a larger forum outside of SpaceX...General Mars threads should go in the general Mars section, not in the SpaceX Mars section.
My theory is that we are going to be living in mars bases one way or another.. even if we stay on earth. This is just another example out of thousands of how the inexorable evolution towards efficient sustainable technology on earth brings mars bases closer.
Plant based meat substitutes tend to have 2 problems: many of the better ones are based on glutens, which make many peoplei ill, and in order to have an acceptable taste they contain ridiculous levels of sodium chloride.