Inhabitable Planets Too Close Together?

SWM wrote:Sure. Or it could be done by grinding up the surface oxides on a planet like Mars and extracting the oxygen.

Would grinding up the surface oxides produce fusion reactor fuel to convert hydrogen to Helium so it doesn't recombine?

That was the element of using water as the input material that made it attractive.

SWM wrote:

Algae -- especially a gene-engineered variety for maximum carbon sequestration -- would seem the simplest and most cost efficient way of dealing with any CO2. Genie-Corals would work, too.

There have been plenty of studies on using algae for this. Even with extreme genetic modification, it would take many centuries or even millennia to create a breathable atmosphere. Algae simply don't work fast enough.

I wasn't proposing Algae for making a breathable atmosphere, but for carbon sequestration in conjunction with some mechanical O2 production. Especially with genie-algae feeding genie-corals you aren't restricted to separating the O2 from the carbon to sequester it as coral reefs.

I don't see a single method being really effective in converting the mass required. The combination I propose here would solve a couple of problems that hamper O2 production -- algae isn't fast enough to break down CO2, and mechanical methods leave the non-oxygen component free to recombine.

cralkhi wrote:I've read about an experiment with making oxygen from oxide rocks by heating them up enough for the oxygen to be broken loose ("vacuum pyrolysis"). Temperatures seem to be 2000+ K.

http://science.nasa.gov/science-news/sc ... moonrocks/

http://www.uapress.arizona.edu/onlinebk ... rces08.pdf

I wonder what would happen if you did this on a REALLY large scale (eg giant solar mirrors/sails concentrating light to get a continent-sized area of crust hot enough to pyrolyze it).

You might actually be able to give the Moon a breathable atmosphere this way given sufficient (enormous) amounts of solar mirrors ... not the nitrogen though, it'd have to be like the pure oxygen low pressure atmosphere inside spacesuits.

Pure oxygen atmosphere is a terrible idea, it´s not used in spacesuits because it´s good, but because it´s difficult to do something better.

For one thing, pure oxygen is highly explosive... Low pressure mitigates, but it´s still a dangerous thing to use.

Let us get back to first principles.

You need an atmosphere that is about 3/4 Nitrogen, 1/5 Oxygen with traces of CO2 and other stuff at about the right sectional density.

A mostly airless world is probably the easiest starting point.

If you have a planet with far too much CO2 and pyrolysis can't transform it because it will recombine, then simply cook it off using orbital mirrors to heat selected regions of the atmosphere to a temperature where a significant fraction of molecules are at escape velocity.

Once this is done you might use the mirrors to heat selected portions of the planet surface to extract nitrogen and oxygen via pyroalisis.

However; it is more likely that you will have to import gases as ice extracted from comets.

Look again at the volume/mass requirement.

1eex14m^2 x 1eex4 kg per square meter is 1eex18 Kg or about 1eex15 tons or 1eex15 cubic meters.

This is a comet about fifteen kilometers in diameter. Assuming a solar powered propulsion system using material extracted from the comet as reaction mass, you can preprocess the ices in transit to use the crap you don't want (Carbon) for reaction mass while retaining water ice, ammonia ice and free oxygen ice if you have it.

Once you have cooked off unwanted atmosphere, you use solar powere destination and pyroalisis to finish processing gases from the comet. Stuff you want is exhausted out of an orifice pointed retrograde to deorbit while stuff you do want is exhausted in the opposite direction to counterbalance thrust and eject it from orbit.

Tenshinai wrote:For one thing, pure oxygen is highly explosive... Low pressure mitigates, but it´s still a dangerous thing to use.

Not so much explosive as inducing everything to burn. "Fireproof" things will burn merrily in 100% oxygen.

You need an atmosphere that is about 3/4 Nitrogen, 1/5 Oxygen with traces of CO2 and other stuff at about the right sectional density.

And that density can vary quite a lot as long as you adjust for it.

Nitrogen also isn´t a must have, it can be replaced by other gases, IIRC with helium being the least problematic one. Nitrogen probably works best but supplementing it with others can also work well.

A mostly airless world is probably the easiest starting point.

As long as an existing atmosphere isn´t severely harmful to the terraforming process, it is vastly preferable over starting from zero.

kzt wrote:Not so much explosive as inducing everything to burn. "Fireproof" things will burn merrily in 100% oxygen.

To be entirely correct, pure oxygen can hyperaccelerate combustion.

And yes, put pure oxygen in the wrong place and what you get IS an explosion.

What happens when something specifically made to burn slowly burns in pure oxygen:
https://www.youtube.com/watch?v=174_ivcc73E

Add in the right substance that is conducive to rapid burning instead and you can use it for blasting craters. Not that anyone will use it like unless they have to, it´s way too volatile.

LOX can be very dangerous.

http://wiki.nasa.gov/oxygen-fire-incide ... 7-2003.pdf

Weird Harold wrote:Would grinding up the surface oxides produce fusion reactor fuel to convert hydrogen to Helium so it doesn't recombine?

That was the element of using water as the input material that made it attractive.

But you don't need anywhere near that much hydrogen for fusion fuel. That much hydrogen would be enough to run the entire planet for a millennium!

Anyway, my point was that there are numerous sources for the oxygen. But they all have the same basic problem--you have to process enormous quantities of material to extract enough oxygen.

I wasn't proposing Algae for making a breathable atmosphere, but for carbon sequestration in conjunction with some mechanical O2 production. Especially with genie-algae feeding genie-corals you aren't restricted to separating the O2 from the carbon to sequester it as coral reefs.

I don't see a single method being really effective in converting the mass required. The combination I propose here would solve a couple of problems that hamper O2 production -- algae isn't fast enough to break down CO2, and mechanical methods leave the non-oxygen component free to recombine.

[/quote]
It's still the same problem. It can't sequester carbon any faster than it can generate oxygen from CO2, because it is the same process doing both.

SWM wrote:It's still the same problem. It can't sequester carbon any faster than it can generate oxygen from CO2, because it is the same process doing both.

The algae can't, but genie-coral can -- as calcium carbonate. The coral can't generate oxygen, but it can sequester carbon.

I agree that simply using thermalisis to separate CO2 in an atmosphere in situ is not going to work unless you have something else to bond with the free Oxygen and Carbon. Perhaps hydrogen extracted from Methane from comet could be injected to bond with the free Oxygen to form water that would precipitate out might be a solution. However; it is more plausible to just boil off a CO2 atmosphere from a planet then replace the atmosphere with the proper mix of Nitrogen and Oxygen as well as water if needed for a hydrosphere. Yes, the volumes seem daunting but given the energy budget that an interstellar colony ship should have it should not be that big of a problem. Pick a comet, grab it and bag it, then apply controlled heat to distillation separate the gases that you want, then use your colony ship's fusion rocket as a tug to boost it to the proper orbit. Alternatively; you might thermolisis to extract Oxygen from an orbiting moon to drop on planet.

We can scream about how huge the volumes and masses are but if humans have the technology to build a fusion rocket powered colony ship then this terraforming is within their energy budget. Perhaps no one has realized this because I am the first to crunch the numbers?

Think about it from a philosophical perspective. We worry about our current industrial civilization's 1eex13 Watt energy budget screwing up Earth's environment but our interstellar colony ship will have an energy budget of 1eex15 to 1eex18 Watts. Finding the energy to process and move the relevant masses would probably be less problematic than properely understanding the Macro chemistry to create a viable ecosystem.

SWM wrote:

Weird Harold wrote:Would grinding up the surface oxides produce fusion reactor fuel to convert hydrogen to Helium so it doesn't recombine?

That was the element of using water as the input material that made it attractive.

But you don't need anywhere near that much hydrogen for fusion fuel. That much hydrogen would be enough to run the entire planet for a millennium!

Anyway, my point was that there are numerous sources for the oxygen. But they all have the same basic problem--you have to process enormous quantities of material to extract enough oxygen.

I wasn't proposing Algae for making a breathable atmosphere, but for carbon sequestration in conjunction with some mechanical O2 production. Especially with genie-algae feeding genie-corals you aren't restricted to separating the O2 from the carbon to sequester it as coral reefs.

I don't see a single method being really effective in converting the mass required. The combination I propose here would solve a couple of problems that hamper O2 production -- algae isn't fast enough to break down CO2, and mechanical methods leave the non-oxygen component free to recombine.

It's still the same problem. It can't sequester carbon any faster than it can generate oxygen from CO2, because it is the same process doing both.[/quote]