New Mars Forums

Let's hear them.

So I was thinking some more about harnessing solar power in the inner solar system before it gets all weak out by mars. 

Let's say you have an umbrella made from shiny Mylar.  It doesn't have to be Texas-sized, just 10 meters across or so.  Something we are capable of launching toady.  if set to face the sun, it would focus the sunlight to a point on the sunside.  Now if you put a collector on the "handle" at that focus point, you could redirect all the sunlight over that 78 m^2 into a small area.  If you took that point and fed it to a fiber optic cable, you could direct it anywhere you want, like Mars.

I haven't done the math yet but you could probably strike a balance between its orbital speed of the sun, light pressure and distance so that it orbited the sun at the same angular velocity as Mars, thus, always between Mars and the Sun.  Not directly of course but just off to the side to collect and redirect sunlight that would miss Mars.  By the time the light from a pinpoint reached mars, it would probably spread out enough to hit the whole surface.

They would have to have a gyroscope to make corrections in their orientation and a little smarts to make sure they are facing Mars and "leading their shots" to compensate for the speed of light delay.

All in all, they don't sound too complicated.  The best thing is that they don't rely on asteroid mining or other science fiction stuff (although that would help).  We could build and launch them today.

You would have to launch thousands of them but that also allows you to do it little by little.  erecting a 500km mirror above Mars is something that people might always put off into "the future" but sending up a couple dozen inner-system-collectors every year sounds doable.  Especially if they cost only a few thousand bucks apiece. 

I know that you'd spend more on stuff like electronics and fiber optics on these than with a simple huge Mylar sheet but keep in mind that you'd be collecting sunlight closer to the sun where it's brighter. More bang for your buck.  Also, it would be harder to take them down by sabotage or accident and turning them into a super weapon would be pretty tough.

Anyone want to go into business?

Wouldn't it make more sense to practice on dead worlds before putting up gigantic lenses, mirrors and sheilds in orbit of a living planet.  I'd perfer that we learn the ropes on a place where a miscalculation wouldn't cost 100 million lives and 5 trillion dollars.

Actually, if I'm not mistaken, hydrogen will react with CO2 directly.  Venus' pressure and temperature are in the right area for it too. The trick is getting enough H2 to Venus to do the trick.  My math shows it's something like 3x10^19 kg of H2 to convert the whole atmosphere to water and carbon.  It seems like getting that much in a magnetic trap is going to be slow going at best.

Creating an honest to God magnetosphere might be on the order of difficulty of building the whole world from scratch.  The best solution I can think of is to put a big electromagnet or web of them at the L1 point to act as a shield for the incoming solar wind.  It would trap particles which I guess you could use but I think the quantity is going to be pretty low.

REB,

Thanks for the props.  I’m also convinced that bringing H2 to Venus is the only way to go.  If you grab a comet from far out, you will still need to have energy to split the water to use as a fuel.  Plus, you have a lot of waste oxygen to deal with.  Getting hydrogen from one of the outer gas giants won’t be easy but I’m sure that if intelligent uses of gravity slingshots are used, you can conserve a lot of energy.  I’m more concerned about what kind of craft would be up to the task and how many trips it would take.  Some breakthroughs in material science could shore up some of those issues.

As for the day length/spin problem I think crafty use of mirrors is probably the way to go for the first few thousand years.  As someone posted before, it would take 5000 years of spinning if you were able to harness all of the incoming sunlight.  So that’s a distant goal at best.  However you could fake it if your front shade could cycle between dark and translucent on a 24 hour cycle.  Likewise, you could have mirrors at some modified L2 points to act as some bright “full moons”.  Those could shine on a 24 hour cycle too.  Hell, you could probably work it so that day and night were planet-wide.  Such mirrors would have to be M2P2 craft with charged dust suspended in them.

I don’t know about that planetary shell idea.  You really only need to shield the light coming on from the front.  Why use thousands of miles of fiber optics if you can redirect the light with mirrors and no medium but space?

the idea with the mirrors close to the sun is that they would focus it to a small area.  If the concentrated light could be redirected from a small point with fiberobtics or something, you could direct it to one place.  It would still fan out but you would have a nice little baby star near the sun.

A couple problems with this are that the things would have to be in some kind of orbit which would take it out of the line of site for some time.  It also could be used as a weapon if some nut wanted to put the earth through a bad heat wave.

Getting H2 from Earth or comets involves cracking water.  That means energy.  Another thing to consider is that you end up with a bunch of oxygen that you need to do something with.  I guess you could react it with the 3 bars of nitrogen to make the Venus the happiest planet in the system.

Also, remember that sending H2 form Earth means that we'll have to give up a sizable percentage of our water. I don't think too many people will like that idea.

One thing to note; when I ran my numbers, Venus ended up with about 10% of the water on earth if you turn the atmosphere to water with hydrogen.  you'll still need s shade of some kind to keep the sun side from frying and the moisture in the atmosphere from keeping the greenhouse effect going.  There would be plenty of exposed land to live on since the water would of course settle.  The poles would probably be the first habitable parts.

I guess you could put Venus and Mars at the Earth/Sun L4 and L5 points.  Still, moving the planets is absurd.  Teleporting...

Back to comets, does anyone have figures on how many comets it will take to make an atmosphere and some oceans?  Unless they are the size of our moon, I'm guessing it will take quite a few.  What about a buffer gas?  Unless the comets contain a good amount of nitrogen or some noble gas, you still need to get that from somewhere.

As far as crashing comets go here are my thoughts:

If you send it hitting the surface at like 1% C, you're probably going to add heat. However, if you are able to park the think in L2 , chip of bits and send them toward the planet at such a speed that they'll melt before they hit you will probably have a net cooling effect.  It might not be much.  Something like letting an ice cube melt in a hot room.  I could be off about this.  I'm no good at thermodynamics.

In the interest of spinning the planet faster, you would probably want to strike the planet in the direction of rotation.  Again, probably won't have a huge effect but every bit helps.

Does anyone know how many comets this will entail?  Crashing comets into Mars isn't necessarily all about adding water.  Venus however is much bigger and almost devoid of water so comets or hydrogen is the only option of getting it there. It seems to me like it would take millions to provide a sizable fraction of the water we have on Earth.

I'm still rooting for Hydrogen from Uranus 

You've touched on the solution and the problem in one stroke.  Since Venus has no water, the bacteria would have no medium in which to grow and process the air.  We would also have to seed it with an airborne species which I don't think yet exists.  Perhaps you could start it with an ice comet crash but once they use up all the hydrogen from the water, they'll die off.

At least that's the gospel according to Zubrin.

Jupiter is probably a bad choice then but Uranus "only" has an escape velocity of 21 km/sec.  2/5ths of Jupiter and only twice as bad as Earth.  It would take longer to get there but it would be easier to get it out.  It’s also a lot colder so you would heat up less as you zoomed through the atmosphere. 

You can tell I'm not giving up this idea without a fight 

well if fusion is ever adopted the gas giants will be the big storehouses.  If they can get to the He3, they should be able to get the hydrogen too.  Maybe not though.

If the hydrogen is added to the atmosphere and you get 90 bar of water, all you need to do to cool it is put up a sun shade.  pretty much every description of Venus terraforming includes one at some point.  once you get a big water rain, the albedo will go way up if you end up with some oceans.