Author Topic: Increasing Mars' atmosphere with magnetic field @ Sun-Mars L1  (Read 3968 times)

Offline Danderman

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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.

Offline Eric Hedman

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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.
How would you scoop up a large mass of atmospheric gases without it seriously aero-braking your cycler at Venus?

Offline Robotbeat

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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?
..
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.
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Offline Robotbeat

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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.
How would you scoop up a large mass of atmospheric gases without it seriously aero-braking your cycler at Venus?
Youd have to input energy here.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Online meekGee

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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?
..
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?

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Offline Rei

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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.
How would you scoop up a large mass of atmospheric gases without it seriously aero-braking your cycler at Venus?

Well, you could probably make up for the delta-V with gravity assists.  But I certainly wouldn't want to be the one tasked with finding a viable trajectory  ;)

Either way, that would be a painfully slow process.  And I'm not sure how much of Venus's atmosphere you could remove before you'd hit its other, opposite problem.  Venus's surface is a large percent (I want to say something like 7%?) FeO. If you start terraforming it and producing oxygen, it's just going to rust away your oxygen.  It needs at least part of the oxygen that's bound up in its carbon dioxide.  Before you can reach stability, you basically need to recreate what happened on Earth with the formation of the banded iron deposits..
« Last Edit: 03/08/2017 11:02 AM by Rei »

Offline Robotbeat

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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?
..
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?
It depends on how massive the magnetosphere device is.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Hop_David

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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?
..
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.

Online meekGee

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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?
..
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.
.. 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 (!)
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Offline Hop_David

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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.
.. 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 (!)

Say we did terraform Mars, it'd take millions of years for atmospheric erosion via solar wind to make an appreciable difference. It's a very slow process.

I wouldn't be surprised if propellent spent in stationkeeping would exceed mass of atmosphere lost via solar solar wind.

Online meekGee

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Wiki says:

Quote
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 is

P = 1.6726×10−6 * n * V2

where 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.

For the sake of discussion, let's work with P(Earth)=3 nPa.

I'd expect n to go by inverse r-squared, and v (based on gravitational energy) by inverse root r.  So just as a starting point, let's take P(Mars)=1 nPa, nice and round.

Therefore we get a thrust of 1 mN for each square kilometer of effective sail area.

"effective" being the key word here.  Most of the wind flux continues with very little disturbance, but still, we're talking about shielding an entire planet (~7E6 km2) and if the wind catches the long magnetotail at an angle, you have a humongous cylindrical cross-sectional area.

Let's work with a starting point assumption of Aeff = 1E6 km2, so the required force is 1000N.  (This is an absolute WAG.  I'd say it's conservative for "head-on" wind, but might be liberal for "sideways" wind.

If the thruster ve is 3000 m/s, the mass burn rate is (F = m-dot * ve) = 1000/3000 = 0.3 kg/sec, or 25 tons per day.  Yuck.  But not completely crazy, so there's hope.

----------------

Can it be compensated for with orbital positioning?  Let's see what we can work with.

A big component of this acceleration will be radial, away from the sun.  So positioning the craft closer to the sun could help, as commented above.

L1, the article says, is 320 Mars radii away from Mars, so Mars' gravity there is 1/100,000 of Mars surface gravity, or 0.00004 m/s2.  By varying the position of the spacecraft (towards the sun(, we can recoup a fraction of that. Let's say 10%.  So 0.000004 m/s2.

We want to generate 1000N, so the mass of the spacecraft has to be m=F/a=25,000 tons.  (Did I get that right?)

k.  That's more than yuck.

Thrust it is then.

----

Since we're talking about terraforming an entire planet, 25 tons/day is not crazy.

David Hop above points out that this is more than today's mass loss rate (which is 0.1 kg/sec) but I'd argue that this mass loss rate would increase the minute the atmosphere starts thickening, so this will become a net positive.

Also, my Aeff=1E6 km2 is really a wild guess.  I think I'm on the conservative side.  If I'm off by even 1 OOM, this goes from "yuck" to "ho hum".

Much will depend on the shape of the magnetosheath.  If it can be shaped to be more "aerodynamic", Aeff will decrease.

Here's an idea: use multiple generators.  A small one near the sun, followed by a larger one downstream, etc.  This will make the magnetosheath more streamlined, with less "head" area, and hopefully less drag.
« Last Edit: 03/08/2017 06:35 PM by meekGee »
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Offline Space Ghost 1962

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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.

Online meekGee

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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.

You lost me...

I see to places where work is needed.

- Maintaining thrust to oppose the impulse change in the solar wind (since the orbital tricks seems much much too weak)
- Maintaining the magnetic field (which I'm not sure if it really requires work) - and is an energy, not momentum, consideration.

Which of these are you addressing?
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Offline Robotbeat

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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?
..
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.
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Offline Space Ghost 1962

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Could a huge magnet turn the Red Planet green?

Quote from: Bruce Jakosky
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.

Online meekGee

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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?
..
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.

If you read above, I got 1 kN as a ballpark estimate, at Mars distance, on what I estimated was drag on the sail.

This will be the equivalent of, oh, 10-100 kN for Earth.  A couple of OOMs from your number.

I want to find out if I have a mistake there - do you have the source?
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Offline Robotbeat

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Could a huge magnet turn the Red Planet green?

Quote from: Bruce Jakosky
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.
I totally agree with this. The magnetosphere is the last thing we would do (well, before full oxygen) while terraforming Mars.
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Online meekGee

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Could a huge magnet turn the Red Planet green?

Quote from: Bruce Jakosky
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.
I totally agree with this. The magnetosphere is the last thing we would do (well, before full oxygen) while terraforming Mars.

Without numbers, we got nothing, just bouncing back and forth between "it won't work" and "yes it will!".

It really brings us back to the required thrust levels, and energy consumption.  It also depends on how the planet/atmosphere will react to the increase in pressure that will follow - will it be a runaway effect?

This can be the greatest concept to hit the airwaves in a very long time, or just an interesting theoretical discussion.

It's interesting enough that I'm sure the follow-up math will be done.
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Offline Robotbeat

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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.

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Online meekGee

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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.

I was referring to the discussion upthread about energy and impulse, sitting "near" L1, etc.

As for the erosion rate, you clearly can't undo in 100 years what has taken millions (or billions) to occur - unless you have some positive feedback mechanism which they were alluding to.

Looking at the numbers, however:
- Mars loses 0.1 kg/sec (they say), which is 3.1 E6 kg/yr.
- Mars atmospheric mass is 2.5E16 kg.   (https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html)
- Straight time constant for a mere doubling of the atmosphere is therefore E10 years.  10 Billion.

So clearly it's not linear, since Mars isn't that old even.  Or the erosion rate is wrong. Or magnetic fields have nothing to do with atmospheric loss.

Hence the need for modeling, and some of the work they hinted at.

EDIT:
This abstract arrives at a similar conclusion:
http://science.sciencemag.org/content/315/5811/501

EDIT2:
Looked some more, and there's some head scratching going on. If atmospheric loss has to do with lack of magnetic field, then there must have been much higher erosion rates in the past.  .
« Last Edit: 03/09/2017 05:43 AM by meekGee »
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