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#26 2016-10-17 15:21:15

karov
Member
From: Bulgaria
Registered: 2004-06-03
Posts: 953

Re: 2014-UZ224: New Dwarf planet

Void wrote:

I enjoy your work.

Yes. I enjoy it too! Brilliant.

The spectrum of icy bodies deserves an online calculator!

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#27 2016-10-17 16:05:20

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: 2014-UZ224: New Dwarf planet

A few calcs for reference:

1. To heat up 1kg of ice from -180C to 0C and melt it, takes 700KJ of heat.
2. A 5000MWth nuclear reactor would therefore melt 7143kg of ice per second.

To melt an icy body 58km in diameter using a 5000MW nuclear reactor would take 450,000 years assuming no heat losses due to radiation.  Over a practical timescale, we can assume it will never happen.  However, to melt a sphere of water 500m in diameter would take just over 100 days and a sphere 1km in diameter would take 850 days.

At the centre of a 58km body with density 1te/m3, pressure would be about 2 bars.  We can simply melt our way down to the centre of an icy asteroid and use nuclear waste heat to begin melting it from the inside.  The asteroid will consume huge amounts of waste heat before melting all the way to the surface.  Even with a TW of heat, it would take about 2000 years to completely melt.  This removes population density pressures from the mini-ocean world for a long time to come.  A 1km diameter internal water filled void with pressure of 2 bar, could carry a population of 250,000 without feeling overcrowded.  As more ice melts, more pressurised living space can be created.  This is a very different situation to a free-space O'Neill type habitat, where the need to dump waste heat into space places stringent limits on habitation density and the need to contain internal pressure requires thick pressure shells that are extremely massive.  In our internal asteroid ocean, habitation density is limited only by the rate of heat transfer into ice.  Habitats could be extremely light-weight and thin structures, as there would be no differential pressure between the inside air and the water outside.  This means that once the initial investment is made to set up the nuclear heat source in the core, expanding living space should be quite cheap.  Habitats would still need to rotate to produce gravity, as gravity close the centre of an asteroid that small would be non-existant.  Food supply would be largely aquatic, with artificial lighting supporting aquaculture in water between human habitat buildings.

If the nuclear reactor core has a power density of 500MW/m3, and is 50% fuel by volume, the fuel would weight 100 tonnes.  If the ancillary equipment, core barrel and turbo-generator weigh 10 times as much, the whole system would weigh about 1000 tonnes, with mass power density of 5kW/kg.  I am assuming shielding will be provided by water.

On this basis, a group of human colonists equipped with a few thousand tonnes of supplies, could essentially terraform an icy asteroid within the lifetimes of people now living.  The more people present, the more heat generated and the more rapidly the ice would melt.  Eventually, if population kept growing and the nuclear power supply kept growing, the entire body would melt and a spherical pressure shell would be needed to prevent the water from boiling into space.  Still, it is worth noting that a ball of water 58km wide with a surface temperature of 273K would radiate 3300GW of heat into space.  That's enough energy to support a population of 165million people, even if they use electricity to grow their food.

Does anyone remember this episode of voyager?

http://memory-alpha.wikia.com/wiki/Thir … _(episode)

Last edited by Antius (2016-10-17 17:12:11)

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#28 2016-10-18 05:23:24

Antius
Member
From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: 2014-UZ224: New Dwarf planet

Many of the Jupiter Trojan asteroids appear to be icy.

http://www.lpi.usra.edu/decadal/sbag/to … rojans.pdf

I would suspect that these are probably the best early targets for this type of colonisation.  Jupiter distance sunlight levels at ~50W/m2 may be adequate to allow a solar powered approach.  Not sure if this would be a weight advantage, but it avoids the need to develop a low gravity nuclear reactor.  The habitats themselves could be transported pre-packed in an inflatable fibre-reinforced bag, which will serve as the wall for the underwater habitat.

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#29 2016-10-18 05:39:25

karov
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From: Bulgaria
Registered: 2004-06-03
Posts: 953

Re: 2014-UZ224: New Dwarf planet

Where was the estimate about uranium/torium abundance in 'cometary material' ?

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#30 2016-10-18 21:09:03

Void
Member
Registered: 2011-12-29
Posts: 5,345

Re: 2014-UZ224: New Dwarf planet

I am very encouraged by your mention of the Trojan Asteroids, somewhat perplexed, that such a major body of objects, has been so little mentioned.

I decided to put these links, in not to detract, but to perhaps see where and what are the easy sized objects for adaptation to your suggested methods. 

https://en.wikipedia.org/wiki/List_of_S … ts_by_size

From post #7 Antius said:

The concept could be taken all the way down to bodies perhaps 50km across.  In that case a 1 bar pressure would be achieved at the sea bottom some 8km deep.  The solid floor of the 'ocean' would have a 1 bar outside pressure but a gravity of only 1 thousandth of Earth's.  Para terraforming would be relatively easy.  With such low gravity, the membrane tension of water would prevent catastrophic floods for very small leaks and flowrate would be slow even for catastrophic leaks.  At the ocean floor, habitats would need be little more than steel frames covered in a polyethylene liner.  Due to buoyant forces, they would need to be tethered to the ocean floor, but at 10(-3) gees, buoyant forces would only be 1kg per cubic metre of water displaced.

So, then this:
https://en.wikipedia.org/wiki/List_of_S … _to_100_km

Of course only some will be icy as you want.  I realize you didn't need this, but it has helped me get a better understanding.

I do have perhaps a few variations on your theme so far, one which is not too silly.  The Antius Sub Dwarf Planet, with a popcorn core.

They are probably going to mine the core anyway, so why not utilize the "VOIDS", in the core as habitation?  Curiously, in the center, will be a place of very close to microgravity.  Some voids there would be useful for whatever you want.  Spinning synthetic gravity machines.  Strange large caves with some kind of plants connected to walls or trays.

Of course these spaces will be harder to cool, being more remote from the ocean.

Antius also said in post #1:

New dwarf planet discovered at the edge of the solar system.  The new world is some 500km in diameter.
http://www.space.com/34358-new-dwarf-pl … uz224.html
This dwarf planet could be terraformed relatively easily by melting it using a nuclear heat source.  The result would be a water ocean ~90km deep, overlying a silicate core.  An icy shell would float on top of the ocean and would provide enough pressure at its base to prevent the water from boiling.
If the shell is 800m thick, pressure at the surface of the ocean would be 1 bar.  About 300GW of heat would be required to keep the global ocean liquid, as heat flux through the shell would be about 0.5W/m2.
Pressure at the ocean bottom would be about 90bar.  Mining of silicate materials would be carried out by dredging.  An ocean ecosystem could be based upon algae and plankton in the global ocean.  This would require some form of artificial lighting.  Humans would live in floating habitats tethered beneath the ice shell.  Maybe it would be possible to farm the ocean for a large proportion of food needs.
Such a terraformed world should be relatively easy to build, as aside from the provision of a nuclear heat source, no large-scale planetary engineering is required.  Terraforming could presumably be carried out incrementally, with an initially small habitat and nuclear heat source, resulting in a localised ice covered sea.  As colo isation proceeded the world would gradually transform into a global ocean.  Ammonia dissolved within the water will provide fixed nitrogen needed to fertilise the ocean ecosystem.

Supposing you did establish your "Civilization" on this world, where the people lived under an ice shell 800 m thick, and that they could access the core as well, but would have to cope with an ocean pressure of 90 bar at the surface of the core.

What if the inhabitants later expanded their civilization by building "Popcorn/foam" core worlds with a water/ice ocean surround?  Then they could eventually get the pressure at the bottom of their ocean down to 1 bar, and at that point they could tunnel their core, making it into a "Popcorn core".

The built worlds would start with a metal sphere, with compartments, many of the compartments would be filled with tailings, as you would want your artificial core to on average weigh a little more than water does, so that it would stay centered at the bottom of it's ocean.

They would then surround this "Foam" core with water and ice, to produce the ideal pressure at the bottom of it's ocean, on the surface of the core.

These built worlds would orbit the original parent, and since there would be many you could distribute your population to them and so keep the heat load down on the original parent.

I wonder, could the core be 50% voids?

Hope I haven't colored too far outside the lines.

Last edited by Void (2016-10-18 21:43:51)


Done.

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#31 2016-10-19 03:59:31

Antius
Member
From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: 2014-UZ224: New Dwarf planet

I think ‘pop-corning’ the core will be the default way of building habitable volume in the sub-dwarf water world.

My initial assumptions about how people would colonise such an object were incorrect, because I assumed it would start with a body that had already been melted using nuclear heat and people would simply colonise the end result.  After melting a non-differentiated body, silicates would fall to the centre forming a core and I assumed that humans would either colonise the core boundary or form habitats floating in the water, depending upon the size of the body being terraformed in this way.

The reality is that it would take millennia to melt even a 50km diameter body.  For the first wave of colonists it would make more sense drilling down into the middle of it and using nuclear heat to gradually expand an internal water filled cavity as the ice gradually melts.  As this happens, silicates would enter the water and would presumably be filtered out and used as feedstock for building materials and whatever else the colonists need.

For a population numbering a million or less, melting the whole body would take so long that it exceeds the realistic length of any civilisation.  It takes a huge amount of energy to melt ice.  So by the time the covering ice has declined to 800m in thickness, the bulk of the silicate materials embedded within the ice would already have been used to build habitats and there would be no core as such.

The idea works best with non-differentiated bodies that are mostly ice, with minor additions of silicates.  The optimum diameter would appear to be about 50km.  This gives ~2 bar pressure at the centre and 1 bar at about 60% of the radius.  If the body is much smaller, internal pressures never get greater than 1 bar even at the centre and habitats need pressure shells.  Much bigger, and pressures at the centre begin to get problematic for human beings.  We can just about live at 2 bars, but 5 bars would really complicate things.  So the best candidates would be 50-100km in diameter and mostly water ice.

The news is not good with regards to mining fuel for nuclear power reactors.  Typical uranium concentration in meteorites is <1ppm.  It is not clear that refining uranium from an ore so poor will ever be energetically favourable, even using breeder reactors.  It is therefore likely that fresh nuclear fuel will need to come from Earth, at least initially.  One piece of good news: the fission of 1kg of uranium yields about 21GWh of energy.  So a 5000MWth nuclear reactor will go through just over 2 tonnes of uranium per year.  If transport costs from Earth are $1000/kg, shipping the uranium would add about $0.05 to the cost of a MWh of thermal energy.  A small cost overall.

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#32 2016-10-19 11:57:53

Void
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Registered: 2011-12-29
Posts: 5,345

Re: 2014-UZ224: New Dwarf planet

I'm not very worried about the fission thing.
It appears that the solar option will be sufficient for human reach for some time, and I anticipate that fusion will eventually become real, say within 100 years of time.

With mirrors, I see no reason why the moons of Jupiter, and the Trojans cannot be handled (Except for lethal radiations).

The realm of Jupiter is behind the "Snow Line", the asteroid belt further in, not in the snow belt anymore.

I am interested in a 2D chart, with the horizontal scale being the level of differentiation, and the vertical being the size of the objects.

I would exclude any object without sufficient ice/water for a water/ice column minimum of 1 bar.  But I would make an exception for Earth and Mars polar areas, simply because I want to relate the mini worlds to terrestrials.  In reality, I exclude Earth, because except on the very small scale to prove technologies, our polar ice caps should not be messed with as a rule.  As I have already stated, I would include the polar areas of Mars, as part of the outer realm, as they more resemble the outer solar system than the inner.  This is possible in part due to the meager atmosphere of Mars, and the coldness of the poles of Mars.  I am not sure how much Ceres, and the asteroid comets, can be included, they used to be behind the snow line, but are not anymore.  Therefore the technologies required to handle them are different than for the realm of Jupiter and outward.

Quadrant #1
So, on my chart, I would put the polar areas of Mars in a quadrant for differentiated objects that are large.

Quadrant #2
Enceladus being presumed to be a differentiated object of a smaller size.

Quadrant #3
Callisto being a more or less not differentiated object, at least in it's upper layers, and like Mars of a large size.

Quadrant #4:
The optimal non-differentiated small icy objects that you are most interested in.

There will be gradients of a continuum of these objects, and methods best suited, the preferred tools will be different.

I will speak of how I would handle Callisto, and Enceladus a bit, and see if you may be able to find applications for small undifferentiated worlds.

I previously spoke of canals (Covered of course) on Callisto, and that would be one way.  However for a more dynamic method on Callisto, I would entertain, a honeycomb of cells of water with an ice topping, where each cell is a metallic canister.  Parts of the moon's surface would have these, and in each cell would be an ice covered water cell, protected in part by a metal canister.  Above the ice would be a minimal artificial atmosphere of a pressure required by the vaporization point of the ice.  The vaporization point of the ice would be determined by the temperature of the ice, which could be rather cold.  At the bottom of the cells habitats.

Other areas of Callisto would have ice covered lakes where sediments on the bottoms would be mined, and the metals recovered, and the tailings (Ice/rock)  would be donated to "L" location construction sites, to create artificial world, where "Popcorn/Foam" cores would be manufactured, and ice/water would be made to surround them.

So, in this case for Callisto, a form of strip mining is employed, and from time to time the honeycombs (Cities/Habitats) will be recycled/moved, to allow strip mining to continue, until the entire moon is consumed?  (Lots of habitats then).

Please note that I am staying outside of your range of worlds, and am dealing with world outside of your stated range.  The purpose is to see if you can and will find anything of use for your range of worlds.

Enceladus:
https://en.wikipedia.org/wiki/Enceladus
400px-Enceladus_Roll.jpg
400px-Enceladus_Cold_Geyser_Model.svg.png

Well, here we have an example of what happens when heat is added to such worlds, in this case significantly larger than your optimum size, and the heat we think coming from part of the core.

According to some models, Enceladus has an ocean over part of it's core.  This is probably an unusual situation I would think, for smaller outer solar system objects, but as a model, might help in your efforts.

The only other thing I can think of is if you have an "Oil" which has a similar specific gravity to that of melted water, then you could create a vertical tube, to pass through the ice down to the core to get core materials, early on.  You would need a liner, the special oil, and robots that could survive and work in such an environment.

But of course you are looking at undifferentiated small worlds.

Done.

Last edited by Void (2016-10-19 12:41:48)


Done.

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#33 2016-10-24 11:56:14

Void
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Registered: 2011-12-29
Posts: 5,345

Re: 2014-UZ224: New Dwarf planet

Here apparently is some further information on the asteroids that are associated with Jupiter.

http://phys.org/news/2016-10-kepler-cau … roids.html 

I think the information tends to favor the last things Antius seemed to say.

The other study focused on 56 pre-selected Trojan asteroids in the middle of the L4, or "Greek" group, which orbits ahead of Jupiter. Since they are farther out from Kepler, they could be observed for longer periods, from 10 to 20 days, without interruption. And this turned out to be crucial: Many objects exhibited slow light variations between two and 15 days. Long periodicity suggests that what we see is not just one rotating asteroid, but actually two orbiting each other—the study confirmed that about 20 to 25 percent of Trojans are binary asteroids or asteroid-moon pairs. As Gyula M. Szabó (ELTE Gothard Astrophysical Observatory), lead author of the other paper, said, "Estimating the rate of binaries highlights the great advantage of Kepler, because the interesting periods, longer than 24 to 48 hours, are really hard to measure from the Earth."

What Kepler did not see are rapidly spinning Trojans. Even for the fastest ones, one rotation takes more than five hours, suggesting that the asteroids we see are likely icy, porous objects, similar to comets and trans-Neptunian objects, and different from the rockier main belt objects. "A large piece of rock can rotate much faster than a rubble pile or an icy body of the same size without breaking apart. Our findings favour the scenario that Trojans arrived from the ice-dominated outer solar system instead of migrating outwards from the main asteroid belt," Szabó said.

Kepler aimed at the heart of the L4 swarm. Green dots are the known Trojans, black dots are the observed ones. Credit: Gy. M. Szabó et al. 2016
As Kepler continues its new mission, more objects from the solar system are crossing into its view, including planets, moons, asteroids and comets. The telescope that transformed the science of stars and exoplanets will undoubtedly leave its mark in planetary science, as well.

So it seems to support the notion that an ocean could be gradually melted, and no natural core would predate the melting, and a core with suitable "Voids" could be manufactured, to be protected by the ocean, and at the center of the ocean.  Of course the ocean would be protected by a layer of ice  and/or manufactured materials.

Last edited by Void (2016-10-24 12:01:55)


Done.

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#34 2016-10-24 17:14:01

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: 2014-UZ224: New Dwarf planet

Might end up being easier to colonise the Trojans in some ways than colonising Mars, though the journey times would be a lot longer to Jupiter orbit.  Of course, we aren't actually going near Jupiter, so the propulsive dV is perhaps more manageable.  Maybe nuclear electric mass-drivers can we used for regular transfers?

Melting down to the core in the first place might not be easy.  We would definitely need a nuclear drilling machine.  It might take a few years for a multi-MW machine to melt its way down to the gravitational centre.  Once it is done and the reactor is switched on, habitable volume would start to grow rapidly.

Within the cavity, one would need an oxygen mask to breath, but could otherwise swim around in a normal swimsuit.  With so little gravity, virtually no bouyancy, no differential pressure and a surrounding environment of warm water, human habitats would be lightweight and may be little more than air filled tents.

The key enabling technologies are the transportation systems and relatively lightweight nuclear power sources.

Last edited by Antius (2016-10-24 17:17:59)

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#35 2016-10-24 17:25:04

Void
Member
Registered: 2011-12-29
Posts: 5,345

Re: 2014-UZ224: New Dwarf planet

This is borrowed from a conversation I am having with Tony, it might have use.

https://en.wikipedia.org/wiki/Biorock#C … a_new_reef

Biorock, also known as Seacrete or Seament, is a trademark name used by Biorock, Inc. to refer to the substance formed by electro-accumulation of minerals dissolved in seawater. Prof. Wolf Hilbertz developed the process and patented it in 1979.[1] The building process, popularly called accretion, is not to be confused with Biorock sewage treatment. The biorock building process grows cement-like engineering structures and marine ecosystems, often for mariculture of corals, oysters, clams, lobsters and fish in salt water. It works by passing a small electric current through electrodes in the water. The structure grows more or less without limit as long as current flows.

Possibly that could lead to a method to build corrosion resistant structure from dissolved materials not otherwise useful.

Last edited by Void (2016-10-24 17:27:08)


Done.

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#36 2016-10-24 17:37:13

Void
Member
Registered: 2011-12-29
Posts: 5,345

Re: 2014-UZ224: New Dwarf planet

Artificial Gill:
http://news.bbc.co.uk/2/hi/science/nature/4665624.stm
The thing needs battery power, but we are getting better at that.

Also, whereas Earth water has the standard air mix, I suspect that you could cut down on the Nitrogen, and up the amount of Oxygen that was dissolved in the water.

Henry's Laws would also apply.  Here on Earth air is normally dissolved at 1 bar pressure.  Nothing would stop you from compressing more into the water, up to saturation.  Of course eventually if it encounters lower pressure it will fizz to bubbles possibly.  But your divers will normally be in a warm water enclosure anyway, so any fizzy bubbles could be recovered. 

You mentioned 2 bars of pressure as an optimal maximum in one of your posts, optimal for the bottom of the "Sea".

Just some another option.

I believe I read that in Antarctic dry valley lakes, when they drill a hole in the ice Oxygen fizzes out.
I think the reason is that for about 2 weeks each summer temporary streams dump CO2 laden water into the lake, and then algae in the upper layers extract the Oxygen from it, boosting the Oxygen content of that layer in the lake.

Fun stuff!!! smile

Last edited by Void (2016-10-24 17:38:25)


Done.

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