New Mars Forums

Official discussion forum of The Mars Society and MarsNews.com

You are not logged in.

Announcement

Announcement: This forum is accepting new registrations by emailing newmarsmember * gmail.com become a registered member. Read the Recruiting expertise for NewMars Forum topic in Meta New Mars for other information for this process.

#1 Re: Terraformation » Venus + magnesium » 2013-07-24 13:07:40

<<<But we could estimate that the temperature for chemical dissociation and separation of the Mg is negligible compared with the "temperature" of the trans-orbital velocities. So we , for the purpose of our guestimation could round-up the energy budget to dissociate Mg compounds and to send the metal over to Venus, within the orbital kinetic energy budget. How much delta-V? - 10-ish km/s? Indeed less but I'm lazy to check out. >>>
Depending on the chemical processing technology the energy demands for magnesium manufacture may vary from 1.22e+7 to 3.6e+7 J/kg.  But that's for MgCl2 which is the most common raw material available from sea water. There are processes for making magnesium directly from MgO or other magnesium compounds likely found on Mercury but I haven't found information in energy requirements.  Its probably higher which is why they're not used today.
http://www.belgeler.com/blg/lg2/electro … um-uretimi
The energy to move magnesium from Mercury to Venus orbit can be estimated based on the necessary change of total orbital energy.  If we assume circular (close despite Mercury eccentricity) orbits then it's the difference of kinetic orbital energy for a kg which can be obtained from orbital velocity of the two planets.  This gives approx 5.32e+8 J/kg.  Therefore energy of magnesium manufacture may be significant but we'll deal with that later.
The equivalent delta V required to get to Venus orbit is computed from V = SQRT(2*Energy/Mass) = 3.26e+4 m/sec or 32.6 km/sec.
You can save on energy by shooting in a very elliptic trajectory but that will require a very specific targeting solution but that will only happen when Mercury passes Venus. Since Mercury is slowly turning your Mercury based linear accelerator is going to have difficulty getting a good targeting solution. And if you miss, your magnesium cargo will drop back and probably be vaporised by the Sun.  Ultimately the total energy budget for manufacturing magnesium metal from the crust of Mercury and shooting it to Venus to reduce the CO2 levels is:

2e+20 kg of Mg * (3.6e+7 J/kg + 5.32e+8 J/kg) = 1.136e+29 Joules

Thats less than the 2.1e+29 J rotational energy of the earth so maybe if you figure out a way to keep from blowing the atmosphere away you could speed up the planet rotation.

<<< why Mercury orbit when we could use a statite solar power plant deeply at the sun, say at 1MW/m2 distance ... ?>>>

That assumes that you are going to have to either get the magnesium crust to the statite deeper into the Sun's gravity well which takes more energy or get the accumulated energy to the magnesium processing plant on Mercury. Beamed microwaves perhaps? Otherwise you're going to need a VERY long extension cord! wink

<<<Why 100%. Indeed far less is ok - 20%, 10% ...>>>
100% is used because we can't predict the future technological advances. Obviously no human device will ever reach 100% efficiency.  But using basic physical laws in our computations and 100% conversion effeciencies allows us to estimate the BEST we can do to achieve a specific goal.  Later if the numbers don't look too ridiculous (1,000,000 years to cool off Venus) we can refine them with realistic assumptions about future technology. Otherwise we would just mindlessly give up, wave our hands, and scream that NANOBOTS will terraform Venus, end world hunger, save us from global warming, and reduce the price of gasoline! wink

<<<You'll make me to calculate a recepie, indeed>>>

It's the only way to be able to realistically see which method for Terraforming Venus is the most efficient. Mass, energy, and time schedules are a critical part of of industrial planning whether you are building a statue, a city, or a new world.

<<<Indeed 10exp28 Joules is comparable with the rotational energy of the Earth, BUT magnesium flux to impart the momentum for spinning Venus faster would indeed ( I feel ) strip the atmosphere AND also, I like Venusian diurnal cycle of 2 months day and 2 months night.>>>

Many terraformer enthusiasts do. But I believe that a relatively fast spin rate is necessary to maintain convective movement of the air necessary to cool the surface. At present Venus surface receives less solar energy than the Earth due to the clouds. But lack of mixing due to the slow rotation causes a heat buildup in the lower levels of the air.  Actually it's difficult to blow away the air with collisions.  A Mars sized object hit the earth to create the Moon but here we are with plenty of air anyway.

#2 Re: Terraformation » Venus + magnesium » 2013-07-15 15:01:19

karov wrote:

http://www.spacedaily.com/reports/Mercu … t_999.html
Mg from wiki: "and the eighth most abundant element in the Earth's crust[2] and ninth in the known universe as a whole.[3][4] Magnesium is the fourth most common element in the Earth as a whole (behind iron, oxygen and silicon), making up 13% of the planet's mass and a large fraction of the planet's mantle."
I do not know how rich are the outer layers of Mercury, BUT I remind here that there was long time ago the idea to "extinguish" the excessive Venusian atmosphere with reactive metals.:
Mine magnesium and aluminum by solar-powered self-replicating automated factories on Mercury, and "sniper" Venus by solar-powered catapults with metal ingots, bullets, flakes ...
The metal would react with the CO2 into metalic oxides and sooth ( carbon ) , both solid under high pressure and temperature, which solid residue would precipitate on surface.
MgO the chemical formula of magnesia tells us that each Mg atom would take 1 Oxigen with it. Two Mg atoms to turn to ashes a molecule of CO2.
Molar mass of Mg approx. 24
Molar mass of MgO approx. 40
Molar mass of CO2 approx. 44
Of 4.8x10exp20 kg total mass of the atmosphere of Venus, 27% are carbon by mass. Or...:
... after the magnesium bombardment commences just step aside and wait several decades ( and about 200 000 000 000 000 000 tonnes of Mg delivered ) in order to get a 3-4 bars almost pure Nitrogen atmosphere around Venus and giant masses of magnesia-sooth on surface ... and you have ( pretty much indeed ) way more handable place to terraform and settle.
add water, stir well, wait the sediments to settle, infect with photosynthesizing organisms ...
If the Mercurian rocks of interest are, say, 10% Mg by mass, then "only" 1 000 000 000 km3 of rock must be processed en situ.
With surface area of 75 000 000 000 000 m2 and approx. surface density of 2000 kg/m3 one has to scrape off only 4-5 miles down from the whole surface.
The resulting 90% slag / scoria / dross from the Mg refinement would consist of iron, oxigen, alumina, silica ... ... which with their shear mass of 1 800 000 000 000 000 000 tonnes and areal density of about 30 tonnes per m2 are enough for construction of 600 000 000 000 000 000 m2 of habitat area or 600 BILLION SQUARE KILOMETRES or 1200 TIMES the total planetary surface of the Earth, or 4000 TIMES the land area of Earth!!!!
Thus the project "mine Mg from Mercury to solidify the nasty atmosphere of Venus" would bring only 0.03% "profit" as terraformed Venus, the major objective and the rest of 99.97% would come from utilizing the waste products of the project.

That's not a bad idea, at least as far as terraforming ideas go. The surface of Mercury is believed to be similar to that expected from partial melts of enstatite chondrites. They tend to be high in the mineral enstatite (MgSiO3), from which they derive their name. Perhaps you could calculate the energy required to convert to magnesium to metal and the energy required to accelerate the resulting metal to a velocity to intersect the orbit of Venus.  If you assume the insolation at Mercury's orbit and assume a certain surface area for a solar cell to power everything, and assume 100% conversion you could give us a minimum timeframe within which this would be done.  Energy budget and schedule.

If you could accurately aim so that the magnesium strikes the atmosphere at an angle this could transfer momentum and speed up the Venusian day. Perhaps you could do a calculation of how much of a spin you could give.

Is the reaction of magnesium and CO2 favorable at Venus conditions?
Hmm...I guess it is.
http://chemed.chem.purdue.edu/demos/mai … /5.16.html

#3 Re: Terraformation » Venus » 2013-07-12 02:22:11

Oops I made a slight error myself on the 24 hour energy budget. It should be 2.58*10^22 joules not 2.25*10^22 Joules. Watts goes to 7.45*10^18 W.

#4 Re: Terraformation » Venus » 2013-07-12 01:52:46

Hi Josh! Thanks for the welcome.  Sorry your site went kablooey! It seems I've always been a dollor short and a day late to have a conversation like this with technically savvy people. It seems that patience has paid off.

You've asked so many good questions. I'll try to address them as best I can. I'm an engineer not a space scientist or plasma physicist so my answers will have to be considered within that constraint. Also my personal philosiphical/political/social opionions will leak in occasionally. wink

The specific mass of a thruster with a power of 6.5*10^23 W. (your quote)
W = Joules/sec
My energy budget for 24 hours or 8.64*10^4 sec is estimated as  5^2 *2.25*10^22 Joules
5^2 *2.25*10^22 Joules / 8.64*10^4 sec = 6.5*10^18 W - a smaller value by a factor of 10^4
Unless I made a mistake your conversion is off.  That's why I like to stick with Joules. It minimizes errors and makes comparison so much easier. I'd really appreciate if you show me calculations  where you're getting your numbers.  Otherwise I have to puzzle it out which wastes time. Nevertheless it's still a big honking number. I'm assuming you're talking about the power of an ion stream that is powerful enough to blast away the atmosphere like hydraulic miner blasting away at a hill side. If that was the approach I'd agree with you. But using a homopolar effect is different.  Electric current flows through an ionized fluid within a magnetic field causing the ions to accelerate at right angles to both electric current flow and the magnetic field. Continue this and they finally leave at escape velocity.  Voltage and Current flow are the big issues, not the total mass of ions. The mass requirements will likely be far smaller.  The tricky thing with my system is the fact that the magnetic field will have to be artificially provided by the system itself since Venus currently has no magnetic field. That's the BIG question about the utility of my method. I know the interaction of ionized plasmas, current flows and magnetic fields, in high energy physics labs and tokamak reactors can do amazing things. Astrophysicsal journals are full of reasearch about natural plasma interactions.  Add the orbital mechanics of an artificial ring of ionized air molecules around a planet an a couple of ion beams and things could get interesting. I just don't have the physics expertise to say if this method would work without an externally applied magnetic field but I can't say it won't either. That's what some expensive simulation program might tell us.

The problem with a tower is scaleup.  Ionic bonds in metals and concrete appear strong at our scale, but as objects increase in size they remain fixed while volume related values such as mass/weight go up according to the cube root.  That's why a dinosaur the size of Godzilla would collapse into a pile of goo from his own weight as his cellular structure ruptured from the stress. A 100 km tower will have the same problem. Then you add the heat and corrosivity of the venusian atmosphere to contend with.  Momentum exchange will be localized on pillars sunk into the surface rather than distributed over the entire atmosphere as in my system. Space based systems can be lightweight and spidery except for the heavy duty components.  High tension components like carbon nanotubes would hold room temperature superconductors with minimal reflective shielding from the suns energy.  I estimated that the solar electric cell might mass only 1.13*10^13 kg well within the mass of several Venus crossing asteroids.  I agree it's going to be a big project, certainly beyond our puny little Type 0 civilization.

Actually I'm counting on the CO2 sticking around.  A thin donut of gas will form around orbit of venus, gradually dissipating from the solar wind. I wouldn't worry about contaminating our atmosphere. The fact that the disk of venus has to be seen through a telescope tells you how much space there is between us and Venus. In 1910 people panicked when they learned that we'd be passing through the cyanogen laden tail of Halley's Comet. No one died and scientists couldn't detect the gas.  Frankly If we can't solve our carbon footprint problem with wise conservation and planning then we won't make it to Type 1.3 and terraforming mars and venus will be a moot point.

I'm trying to attach a picture of the planetary engineering system I have in mind. As you can see
(I hope) there is besides a solar power cell and a dual ion beam cannon, there is a ion stream collector. I cribbed the design from a schematic of a the ion scoop of a Bussard ramjet starship. It's purpose will be similar but far less severe, to capture some of the ejected atmosphere to ionize and use it to fuel the ion cannon. I think after an initial expendature of fuel for 1 Venusian year, the scoop will be able to collect enough ions to make the system self sustaining.

As far as throwing out the air faster, the energy goes up according to the square of the velocity which extends the terraforming time frame. Also my system can't hold the ring ions once they reach escape velocity so that's pretty much the limit.

As you've seen in my diagram my system is on the anti-sunward side of Venus. I realized it was pointless to shield the atmosphere of Venus from the sun when we are blowing 90% of it away. The planetary engineering system will be a statetite, hovering a fixed distance from Venus balanced between light pressure and gravititional attraction. After the project is complete we might move the solar cell to the other side for shielding. Or the residual ring can be used to deflect some of the solar energy. Or we can form clouds on the day side and dissipate them at night allowing heat to escape.  Maybe the laser cooling effect proposed by karov.  qraal01 linked to a paper that proposed that under the right conditions Venus may be inside the edge of the habitable zone. 1.9 insolation shouldn't be that serious a problem to a Type 1 civilization.  CO2 will gradually be absorbed into the new lakes and oceans to form carbonates but that may take thousands of years. In the meantime we'll just have to wear breathers or bioengineer ourseves to handle it.  Humans not wishing to 'go native' would live in aerostats with earth normal air floating above everything.

Yes I've heard of many other methods. Problem is they never discuss WHERE the material that will be used will come from. Where are you gonna get the stuff and how much will it cost in joules. And what kind of giant mechanical hand are you going to use to shove stuff down a volcano and where will it come from. There aren't any hardware stores in space. Every generation comes up with some new 'magic wand' to solve a problem and it never works out as planned. X-rays, electricity, atomic energy, lasers, computers, nanotechnology.  Chemical manufacture requires the presumption of factories, energy producers, raw materials, storage, transportation costs that are never considered. If such an idea is proposed I'd like to see energy and mass requirements. Otherwise it's just hand waving.  I want to see a real energy and mass budget.  And real time frames.

I think reasonably short day will be minimim necessary to maintain psychological health if nothing more.  We are not robots, and I really see no reason to become robots. 3 billion years of a day night cycle is part of our nature. So is living on a planetary surface under an open sky.  No one wants to learn the REAL lesson of Biosphere II.

As far as cost and justification. I'm taking off my engineer hat and putting on my political/social hat I realize we're hierarchichal hunter gatherer hominid primates. It's in our nature to claw and scratch for 'stuff', for mates, for power.  That may be the epitaph on our grave stone.  I really don't think we'll make it to Type 1.3 at our current rate. There's an iceberg on the horizon and the crew has barricated themselves in the wheel house with all the booze and babes and telling us to trust them and shut up.  If we do survive the impending crisis our culture will experience a fundamental change.  I personally think we're fooling ourselves about our own adaptibility.  Where are all the clean futuristic city skylines, the domed underwater metropolises, the arctic luxury hotels?  If we survive it will be because our minds have changed not our bodies.  A type 1 civilization will see the terraforming of Venus as an art project. A way to extend and expand the beautiful variety of life beyond the earth. Of course if we trash the Earth there won't much beauty to extend and expand. As I've said elsewhere we will not be able to reach for the stars while the earth rots away under our feet.

I think i got all the major questions. I'm sure you'll remind me if I didn't. smile


  th_615012623_PLANETARY_ENGINEERING_MACHINE02_122_367lo.jpg

th_466673127_T_Venus00a_122_517lo.jpg

#5 Re: Terraformation » Venus » 2013-07-10 07:27:45

I realize I've arrived late to this party but the idea of terrforming our neighboring planets has always fascinated me.  Clearly Mars will likely be far easier to terraform than Venus.  But I've always had a soft spot for our little hot headed sister world and feel that she could be a valuable asset to human expansion to space if handled correctly.  Two major problems that need to be addressed are her slow rotation and suffocating thick atmosphere. If those two issues are addressed then the other problems (no magnetic field, hot surface, toxic atmosphere) may be easier to deal with and may solve themselves naturally in time.

Unfortunately the crash bang methods (comet/asteroid collisions, nuclear explosions) usually suggested sound too much like planetary rape.  Also I don't think they'll work. Anyone who has seen an animation of two earth sized objects colliding understands that at a planetary scale a rocky crust behaves more like a fluid rather than a solid.  Kinetic energy is absorbed chaotically and a great deal is dissipated as randomized heat energy. The Boltzmann distribution of nuked or impacted atmosphere molecules means only a tiny fraction of the air will achieve the escape velocity necessary to leave the Venusian gravity field permanently. The rest will just fall back with all the heat and radioactive fallout that may take millenia to dissipate. There has to be a better way.

I did some back of envelope calculations to clarify minimum mass and energy needs for terraforming Venus and came up with some interesting results. I'm sticking to the basic joule-second-kg-meter system and scientific notation because using impressive sounding terms like TerraWatt and PettaJoule does not help in allowing others to compare numbers or participate in the conversation. And I’d really like feedback.

Mass of Venus = 4.87*10^24 kg
Mass of Venusian Atmosphere = 4.7*10^20 kg
Escape Velocity of Venus = 10,360 m/sec
Energy to expel all of the Venusian Atmosphere at Escape Velocity = 2.5*10^28 joules

Current Kinetic Energy of Rotation of Venus = 3*10^25 joules
Current Kinetic Energy of Rotation of Earth = 2*10^29 joules

The NASA site says the moments of inertia of Earth and Venus are nearly equal.

Therefore since rotational energy is one half the moment of inertia times angular velocity squared the energy needed to spin up Venus to one day per Earth day is approximately  2*10^29 joules.

Some have suggested that the air could be expelled from Venus along the equator at escape velocity thus not only reducing the total mass of the atmosphere but also speeding up the planetary rotation like Heron's steam turbine.  Inspection of the above data shows that even if we can expel every atom of air we just can't get to a Venusian 24 hour day.  However since rotational kinetic energy is proportional to the square of the angular velocity we CAN get to a longer day.  I estimate that 2.5*10^28 joules can get us to an airless Venus with a SQRT(2*10^29/ 2.5*10^28) * 24 = 67.8 hour day.  Obviously we want some of the Venusian atmosphere left for final terraforming.  I'm assuming one tenth or 9.2 atmospheres (bar). The energy budget drops to  2.5*10^28 * 0.9 = 2.25*10^28 joules.  Plugging into the rotational energy formula above gives approximately = 72 hours or 3 Earth days/per Venus day.

That's a pretty decent spin and could not only help stabilize temperature through atmospheric convection but may also help activate a magnetic field. If the rotational acceleration is applied gently tidal stresses may delicately crack the crust into sections allowing built up heat to release along the fissures and the beginning of a true continental plate tectonics system. This may allow for volcanic release of fresh water vapor into the atmosphere. For the Planet of Love a slow seduction is far better than a brutal assault. 

Otherwise water can be added by means of comet impacts or a small outer solar system object. I've considered Phoebe, Saturn's outermost major moon (approximately 200 km diameter, est. 50% ice) but there may be others. There may be a way of slowly introducing the water to avoid disrupting the crust.  Creating a 1000 year magma ocean is not good for colonization.

So how to do this megaproject? The construction of a massive tower sticking 100 km out of the atmosphere with a powerful blower nozzle has been suggested but as I've said rock behaves like a fluid at planetary scales. Such a device would likely sink into the ground before completion and if not it would topple over once you turned on the blower nozzle. I'm not even going to discuss the challenges of building such a monster in the hot corrosive atmosphere and deep gravity well of Venus.

An elegant solution may be possible. Build a huge solar powered ion cannon and use it to convert Venus into a homopolar motor!  It's easier to build big machines in space rather than on the Venusian surface. And there are many M-class Venus orbit crossing asteroids that could serve as construction material.  The idea goes like this:

1-Place a gigantic solar powered ion beam cannon so that it is always above one pole of Venus. Alternatively place it at the L1 point.  Since an ion cannon is also an ion thruster it could stay there as long as you had fuel to compensate for gravitational attraction and solar pressure. Just don't get too close.
2-Divert a comet or larger water rich object to make an atmospheric grazing encounter with Venus. The fragmentation would make a spinning ring of ionized dust and gas going all the way down to the ionosphere.  The angle of the strike will determine the angle of the ring.
3-Turn on the ion cannon aiming at the perimeter of the ring.  A compensating electron beam will fire where we want the pole to be.
4-As electric charge builds up in the spinning ring a magnetic field will form per the right hand rule.  Electricity flowing outward will accelerate the particles in the ring all the way down to the ionosphere of Venus at right angles to the electric flow and induced magnetic field. In theory the electric flux will reinforce the magnetic field and the ring particle orbital kinetic energies will increase.
5-The particles in the ring perimeter will ultimately reach escape velocity and be dissipated to be replaced by more of the atmosphere.  Ultimately more of the air would be ionized as it spun around the planet with increasing speed.
6-Superhurricane winds are induced from the spinning ionosphere through angular momentum exchange down to the surface causing a slow increase of the planetary spin at the angle of the ring and opposite the direction of the ring.  The ring will be self replenishing as more of the air and some the surface is sucked up ionized and accelerated outward through the electromagnetic homopolar effect.
7-The ring will significantly expand the surface of the Venusian atmosphere, accelerating cooling. However resistive heating from electric flow will have to be factored in.
8- When enough of the air is gone and Venus is spun up enough turn off the ion cannon. If the original comet or moonlet has enough volatiles rain will begin to fall cooling the surface.  The residual ring if formed at a sufficient angle will add to the cooling effect.  Forming rain clouds during the shortened day and dispersing them at night perhaps by using the ion cannon at lower power will also cool things off.
9-If done right the planetary magnetic field and crustal tectonics may be induced from all this activity. Management of the remaining artificial ring and cloud formation will continue to maintain the environment. Then comes atmosphere modification using microbes. Nevertheless the surface will be rather inhospitable until things settle down.

So where to get the energy to do this and how long will it take? Solar energy falling on a solar cell the diameter of Venus at Venus orbit assuming 100% conversion efficiency will produce 2.58*10^22 joules per day.  2.25*10^28 joules/2.58*10^22 joules per day = 872093 days or 2,389 years. This is clearly too long for most civilizations. However if we increase the size of the solar cell by a factor of 5 diameters then the time is reduced to 2389/5^2 = 95.57 years or about 1 century.

The final Venus should be suitable for bioengineered life and modified humans who can handle high CO2 levels. CO2 greenhouse effect will be an issue but an artificially maintained daylight cloud cover can reduce the problem and evening rain will gradually strip it out of the atmosphere to form carbonates.  Solar shading from the residual ring will also help.  And if not a laser cooling effect suggested by karov perhaps using the ion cannon could keep temperatures down. Also the huge solar power cell could be used as a solar shield besides providing virtually unlimited beamed power to the inhabitants of Venus. A true paradise.

Unresolved questions relate to the creation of a self sustaining magnetic field in the spinning ionized ring of electrified air.  Can it be sustained with enough intensity and directional stability to do the work required?  I don't have enough understanding of plasma electrodynamics and ring particle orbital mechanics to answer that question. Perhaps someone out there has access to the requisite knowledge and a powerful computer. smile

Also the ions fired from the cannon will have to come from somewhere.  Just about any element can be ionized under the right conditions. What to use? Obviously it has to be accessible in sufficient quantities. Hydrogen, oxygen, carbon, even nickel/iron are possibilities.  I’ll leave that for future speculation.

2.25*10^28 joules is obviously well beyond the capacity of a Type 0 civilization like ours.  But that's only 2.25*10^28/3.8*10^26 = 59.21 seconds or about one minute of total solar output.  So a Type I civilization on the Kardashev scale that is trending to a Type II could do it without much problem.

Board footer

Powered by FluxBB