My favorite idea is a cycler between Venus and Mars that scoops up excess Co2 and methane from Venus and transports it over to Mars, back and forth, shampoo, rinse, repeat, until both planets are optimized.
Quote from: Robotbeat on 03/08/2017 01:20 amQuote from: Space Ghost 1962 on 03/07/2017 08:37 pmFor no work to be done, no interaction / deflection must be done, thus no flux. So yes, you could have that situation, but in that case it wouldn't do anything, so why would you do it?..This is completely wrong.If I have an electric motor with permanent magnets, the magnets are obviously interacting. But they are not themselves doing work. The permanent magnets do not appreciably lose their magnetism, they last for the life of the vehicle.If I place an object on the hard floor and the object is sitting there, is the floor doing work? No. If I bounce a ball off the hard floor, is the floor doing work? Again, no. The floor does expend energy in order to deflect and interact with the ball. Same for a magnet.I can't believe we're having this discussion. Can someone else help me explain this really basic physical concept?RB - your analogy is not quite analogous.The floor has a "normal force" mechanism. L1 is not stable. So it can't "support" the field generator, and so has to continuously thrust against the delta-impulse it imparts on the solar wind. (That's the "planet-sized but inefficient solar sail" I was describing.
Quote from: Space Ghost 1962 on 03/07/2017 08:37 pmFor no work to be done, no interaction / deflection must be done, thus no flux. So yes, you could have that situation, but in that case it wouldn't do anything, so why would you do it?..This is completely wrong.If I have an electric motor with permanent magnets, the magnets are obviously interacting. But they are not themselves doing work. The permanent magnets do not appreciably lose their magnetism, they last for the life of the vehicle.If I place an object on the hard floor and the object is sitting there, is the floor doing work? No. If I bounce a ball off the hard floor, is the floor doing work? Again, no. The floor does expend energy in order to deflect and interact with the ball. Same for a magnet.I can't believe we're having this discussion. Can someone else help me explain this really basic physical concept?
For no work to be done, no interaction / deflection must be done, thus no flux. So yes, you could have that situation, but in that case it wouldn't do anything, so why would you do it?..
Quote from: Danderman on 03/08/2017 03:25 amMy favorite idea is a cycler between Venus and Mars that scoops up excess Co2 and methane from Venus and transports it over to Mars, back and forth, shampoo, rinse, repeat, until both planets are optimized.How would you scoop up a large mass of atmospheric gases without it seriously aero-braking your cycler at Venus?
Quote from: meekGee on 03/08/2017 03:20 amQuote from: Robotbeat on 03/08/2017 01:20 amQuote from: Space Ghost 1962 on 03/07/2017 08:37 pmFor no work to be done, no interaction / deflection must be done, thus no flux. So yes, you could have that situation, but in that case it wouldn't do anything, so why would you do it?..This is completely wrong.If I have an electric motor with permanent magnets, the magnets are obviously interacting. But they are not themselves doing work. The permanent magnets do not appreciably lose their magnetism, they last for the life of the vehicle.If I place an object on the hard floor and the object is sitting there, is the floor doing work? No. If I bounce a ball off the hard floor, is the floor doing work? Again, no. The floor does expend energy in order to deflect and interact with the ball. Same for a magnet.I can't believe we're having this discussion. Can someone else help me explain this really basic physical concept?RB - your analogy is not quite analogous.The floor has a "normal force" mechanism. L1 is not stable. So it can't "support" the field generator, and so has to continuously thrust against the delta-impulse it imparts on the solar wind. (That's the "planet-sized but inefficient solar sail" I was describing.You can just offset slightly from the Lagrange point and use gravity (of the Sun in this case) to react against the force of the solar wind. Just like a solar sail except acting on the wind and not just the light.
Quote from: Robotbeat on 03/08/2017 04:16 amQuote from: meekGee on 03/08/2017 03:20 amQuote from: Robotbeat on 03/08/2017 01:20 amQuote from: Space Ghost 1962 on 03/07/2017 08:37 pmFor no work to be done, no interaction / deflection must be done, thus no flux. So yes, you could have that situation, but in that case it wouldn't do anything, so why would you do it?..This is completely wrong.If I have an electric motor with permanent magnets, the magnets are obviously interacting. But they are not themselves doing work. The permanent magnets do not appreciably lose their magnetism, they last for the life of the vehicle.If I place an object on the hard floor and the object is sitting there, is the floor doing work? No. If I bounce a ball off the hard floor, is the floor doing work? Again, no. The floor does expend energy in order to deflect and interact with the ball. Same for a magnet.I can't believe we're having this discussion. Can someone else help me explain this really basic physical concept?RB - your analogy is not quite analogous.The floor has a "normal force" mechanism. L1 is not stable. So it can't "support" the field generator, and so has to continuously thrust against the delta-impulse it imparts on the solar wind. (That's the "planet-sized but inefficient solar sail" I was describing.You can just offset slightly from the Lagrange point and use gravity (of the Sun in this case) to react against the force of the solar wind. Just like a solar sail except acting on the wind and not just the light.Did you figure out how "slightly" this would be?
Quote from: Robotbeat on 03/08/2017 04:16 amQuote from: meekGee on 03/08/2017 03:20 amQuote from: Robotbeat on 03/08/2017 01:20 amQuote from: Space Ghost 1962 on 03/07/2017 08:37 pmFor no work to be done, no interaction / deflection must be done, thus no flux. So yes, you could have that situation, but in that case it wouldn't do anything, so why would you do it?..This is completely wrong.If I have an electric motor with permanent magnets, the magnets are obviously interacting. But they are not themselves doing work. The permanent magnets do not appreciably lose their magnetism, they last for the life of the vehicle.If I place an object on the hard floor and the object is sitting there, is the floor doing work? No. If I bounce a ball off the hard floor, is the floor doing work? Again, no. The floor does expend energy in order to deflect and interact with the ball. Same for a magnet.I can't believe we're having this discussion. Can someone else help me explain this really basic physical concept?RB - your analogy is not quite analogous.The floor has a "normal force" mechanism. L1 is not stable. So it can't "support" the field generator, and so has to continuously thrust against the delta-impulse it imparts on the solar wind. (That's the "planet-sized but inefficient solar sail" I was describing.You can just offset slightly from the Lagrange point and use gravity (of the Sun in this case) to react against the force of the solar wind. Just like a solar sail except acting on the wind and not just the light.Normal L1 is an impasse in a 3 man tug of war. Sun's gravity on one side, Mars gravity and centrifugal force on the other side.If pressure from the solar wind were constant, you could set up the magnet a little sunward of Sun Mars L1. Then you'd be striving for a balance in a 4 man tug of war. Sun on one side, Mars gravity, centrifugal force, and pressure from solar wind on the other side.But solar wind isn't constant. The solar sail man in this tug of war would be napping sometimes, other times it'd seem like he was on crack. Station keeping for this L1 solar sail would be a nightmare.
Quote from: Hop_David on 03/08/2017 02:58 pmNormal L1 is an impasse in a 3 man tug of war. Sun's gravity on one side, Mars gravity and centrifugal force on the other side.If pressure from the solar wind were constant, you could set up the magnet a little sunward of Sun Mars L1. Then you'd be striving for a balance in a 4 man tug of war. Sun on one side, Mars gravity, centrifugal force, and pressure from solar wind on the other side.But solar wind isn't constant. The solar sail man in this tug of war would be napping sometimes, other times it'd seem like he was on crack. Station keeping for this L1 solar sail would be a nightmare... and the direction of thrust would vary, with the direction of the solar wind, and with the shape of the sail, which would drag behind the craft in a hard to predict direction.Still though, this doesn't mean you can't counter it with an acceptable amount of thrust.Numbers would be useful at this point, but electromagnetic dynamics is not my field (!)
Normal L1 is an impasse in a 3 man tug of war. Sun's gravity on one side, Mars gravity and centrifugal force on the other side.If pressure from the solar wind were constant, you could set up the magnet a little sunward of Sun Mars L1. Then you'd be striving for a balance in a 4 man tug of war. Sun on one side, Mars gravity, centrifugal force, and pressure from solar wind on the other side.But solar wind isn't constant. The solar sail man in this tug of war would be napping sometimes, other times it'd seem like he was on crack. Station keeping for this L1 solar sail would be a nightmare.
The wind exerts a pressure at 1 AU typically in the range of 1–6 nPa (1–6×10−9 N/m2), although it can readily vary outside that range.The dynamic pressure is a function of wind speed and density. The formula isP = 1.6726×10−6 * n * V2where pressure P is in nPa (nanopascals), n is the density in particles/cm3 and V is the speed in km/s of the solar wind.
Back to the "work" argument. The root of the confusion is the presumption of constants not time varying.E.g. that the tensor isn't present. It is.
At current loss rates driven by the sun and solar wind as measured by MAVEN, it would take about 2 billion years to remove the present atmosphere…. If we put up an artificial magnetosphere, it would be very intriguing in terms of physics. But it would have minimal effect on the thickness of the atmosphere, the global temperature, or the behavior of the polar caps. At least not for billions of years.
Quote from: Hop_David on 03/08/2017 02:58 pmQuote from: Robotbeat on 03/08/2017 04:16 amQuote from: meekGee on 03/08/2017 03:20 amQuote from: Robotbeat on 03/08/2017 01:20 amQuote from: Space Ghost 1962 on 03/07/2017 08:37 pmFor no work to be done, no interaction / deflection must be done, thus no flux. So yes, you could have that situation, but in that case it wouldn't do anything, so why would you do it?..This is completely wrong.If I have an electric motor with permanent magnets, the magnets are obviously interacting. But they are not themselves doing work. The permanent magnets do not appreciably lose their magnetism, they last for the life of the vehicle.If I place an object on the hard floor and the object is sitting there, is the floor doing work? No. If I bounce a ball off the hard floor, is the floor doing work? Again, no. The floor does expend energy in order to deflect and interact with the ball. Same for a magnet.I can't believe we're having this discussion. Can someone else help me explain this really basic physical concept?RB - your analogy is not quite analogous.The floor has a "normal force" mechanism. L1 is not stable. So it can't "support" the field generator, and so has to continuously thrust against the delta-impulse it imparts on the solar wind. (That's the "planet-sized but inefficient solar sail" I was describing.You can just offset slightly from the Lagrange point and use gravity (of the Sun in this case) to react against the force of the solar wind. Just like a solar sail except acting on the wind and not just the light.Normal L1 is an impasse in a 3 man tug of war. Sun's gravity on one side, Mars gravity and centrifugal force on the other side.If pressure from the solar wind were constant, you could set up the magnet a little sunward of Sun Mars L1. Then you'd be striving for a balance in a 4 man tug of war. Sun on one side, Mars gravity, centrifugal force, and pressure from solar wind on the other side.But solar wind isn't constant. The solar sail man in this tug of war would be napping sometimes, other times it'd seem like he was on crack. Station keeping for this L1 solar sail would be a nightmare.Now THIS is a very good point!The solar wind typically has about 10 MN of force on a magnetosphere the size of the Earth's. That's about an F1 or two's worth of thrust.
Could a huge magnet turn the Red Planet green?Quote from: Bruce JakoskyAt current loss rates driven by the sun and solar wind as measured by MAVEN, it would take about 2 billion years to remove the present atmosphere…. If we put up an artificial magnetosphere, it would be very intriguing in terms of physics. But it would have minimal effect on the thickness of the atmosphere, the global temperature, or the behavior of the polar caps. At least not for billions of years.
Quote from: Space Ghost 1962 on 03/09/2017 01:02 amCould a huge magnet turn the Red Planet green?Quote from: Bruce JakoskyAt current loss rates driven by the sun and solar wind as measured by MAVEN, it would take about 2 billion years to remove the present atmosphere…. If we put up an artificial magnetosphere, it would be very intriguing in terms of physics. But it would have minimal effect on the thickness of the atmosphere, the global temperature, or the behavior of the polar caps. At least not for billions of years.I totally agree with this. The magnetosphere is the last thing we would do (well, before full oxygen) while terraforming Mars.
Wait, who is not looking at numbers? The erosion rates of the atmosphere are very small and would remain small even while terraforming. So a runaway effect (if present) wouldn't be greatly affected by the presence or absence of the field. As long as we can start it, we should be able to trigger the runaway through easier means.