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Old 7th December 2018, 04:07 AM   #401
3point14
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Originally Posted by GlennB View Post
Solar power would be my bet, though, as I mentioned upthread, obtaining some of the more obscure elements could be massively difficult. Ditto nukes.
I don't think the obscure elements are required if you do it this way:

https://en.wikipedia.org/wiki/Concentrated_solar_power

How effective that's likely to be at x KM further away from the sun, I have no idea. Similarly, I rally don't know if it would be easier or harder to build one of these on Mars.
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Old 7th December 2018, 04:58 AM   #402
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Originally Posted by Roboramma View Post
Not yet, but I'll look for it

Its one of the short stories in "Tales from the White Hart"
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Old 7th December 2018, 06:46 AM   #403
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Originally Posted by 3point14 View Post
I don't think the obscure elements are required if you do it this way:

https://en.wikipedia.org/wiki/Concentrated_solar_power

How effective that's likely to be at x KM further away from the sun, I have no idea. Similarly, I rally don't know if it would be easier or harder to build one of these on Mars.
It's still subject to the inverse square law, so you'd get a fair bit less per square kilometre than on Earth out of it.

And then there's the usual problem with solar power. Namely that it doesn't work at night AND doesn't do much in a dust storm even during the day. And we just had a Mars dust storm that lasted for more than a month. So better have batteries that can store a month's worth of electricity for your colony.

And that's an even bigger problem for a colony than on Earth. Even skipping past importing energy and whatnot, at least you'd still have air even if you were out of power for a month somewhere. Not to mention you can get there by helicopter with the red cross or whatnot to at least make sure the people have food and water. They won't be happy, mind you, but they'll live. On Mars if you don't even have power for the MOXIE (oxygen plant) for a month, because a month-long storm plunged the surface in darkness, everyone just dies horribly.
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Old 7th December 2018, 07:28 AM   #404
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Originally Posted by HansMustermann View Post
It's still subject to the inverse square law, so you'd get a fair bit less per square kilometre than on Earth out of it.
On the other hand the Martian atmosphere is much thinner, and a significant amount of solar energy is absorbed by the Earth's atmosphere.

My VPN isn't working so I can't get on google, but it looks to me like the power/unit area at Mars should be around 1/3 of that at earth. I think (from memory) that at earth we lose about 1/2 of solar power to the atmosphere, whereas I'd guess that it's basically insignificant at Mars, in which case on the surface of both planets you'd expect similar figures for power/unit area (less on Mars but not that much). The problem of dust storms does complicate that though.
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Old 7th December 2018, 07:30 AM   #405
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Originally Posted by smartcooky View Post
Its one of the short stories in "Tales from the White Hart"
You know, I had a collection of his short stories that included some (or all) of those that I read about 15 years ago, and I think I probably read that one. Something about termites does feel familiar. I'll have to try to read some of his stuff again, though, thanks
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Old 7th December 2018, 07:45 AM   #406
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It's not as insignificant as you'd think, because of the vast amounts of dust in the atmosphere. But be that as it may, you still have the issue of storms literally plunging the surface in darkness for up to a month or two in a row.
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Old 7th December 2018, 07:48 AM   #407
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Yeah, I'd be interested in actual figures for power /unit area on the surface. And certainly agreed that the dust storms cause a problem. At the very least some sort of energy storage would be necessary, but the scale here is pretty damn large.
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Old 7th December 2018, 08:11 AM   #408
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Originally Posted by Roboramma View Post
Do you have any reason to think that it wouldn't be the case? I mean, what specific sorts of health problems do you think could arise from low-gravity that don't exist in zero-gravity?

If your objection is just "Well, you never no, there could be something unexpected" that's fine, but I don't put the probability very high with respect to this particular concern.

The health problems of microgravity (effectively zero gravity, as on the ISS) are lethal long-term. We've gone about as far establishing that as possible, short of leaving an astronaut in orbit long enough to actually die from it. The countermeasures (hours of exercises per day) only slow down the damage.

It's extremely likely that the health effects of fractional (e.g. Mars or lunar) gravity are less severe than those of microgravity. It's possible there are no real problems with it at all, aside from (as in the common SF trope) not being developmentally adapted to full earth gravity and so being unable to relocate there without prosthetics. But if there are other long-term effects, we don't know what will suffice to counter them (i.e. over a lifetime). A few hours a day on a tilt-a-whirl would be fairly easily manageable. Full-time on the tilt-a-whirl during pregnancy would be onerous, but hey, the survival of the species is at stake so you do what you gotta. But if you need the whole population living on the tilt-a-whirl all the time, it multiplies the cost of habitable space on the Martian surface by something like an order of magnitude.
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Old 7th December 2018, 08:12 AM   #409
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Originally Posted by Roboramma View Post
Yeah, I'd be interested in actual figures for power /unit area on the surface. And certainly agreed that the dust storms cause a problem. At the very least some sort of energy storage would be necessary, but the scale here is pretty damn large.
If it's practically a vacuum, does that make storing energy in a flywheel practical?
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Old 7th December 2018, 01:59 PM   #410
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Originally Posted by Myriad View Post
The health problems of microgravity (effectively zero gravity, as on the ISS) are lethal long-term. We've gone about as far establishing that as possible, short of leaving an astronaut in orbit long enough to actually die from it. The countermeasures (hours of exercises per day) only slow down the damage.

It's extremely likely that the health effects of fractional (e.g. Mars or lunar) gravity are less severe than those of microgravity. It's possible there are no real problems with it at all, aside from (as in the common SF trope) not being developmentally adapted to full earth gravity and so being unable to relocate there without prosthetics. But if there are other long-term effects, we don't know what will suffice to counter them (i.e. over a lifetime). A few hours a day on a tilt-a-whirl would be fairly easily manageable. Full-time on the tilt-a-whirl during pregnancy would be onerous, but hey, the survival of the species is at stake so you do what you gotta. But if you need the whole population living on the tilt-a-whirl all the time, it multiplies the cost of habitable space on the Martian surface by something like an order of magnitude.
At this point, I'm not sure exactly how you envision that tilt-a-whirl, that it would be a problem. It's possible to have a centrifuge that doesn't make you puke, and still produces 1g, by basically being large and slow enough, and on Mars you don't need a full g pushing sideways, so it can be even slower.

Basically don't think the fast spinning ride with the plastic horses at the carnival, think something like the London Ferris wheel on its side.

And you don't even need to push it to a full 1g, so it can be fairly slowly rotating. For example if you can generate 3.7m/s2 pushing sideways, that gets you a nice 45° sloped floor and a 5.25m/s2 effective gravity on Mars. Which IMHO should be already decent enough.

And, yes, to concede your point, you probably don't even need to be on it 24/7. You could probably get away with having the work hours in lower g areas, so you don't have to put heavy industrial or scientific equipment on the centrifuge, and just have the free hours and sleep in your room on the Ferris wheel.
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Old 8th December 2018, 03:41 AM   #411
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Originally Posted by Myriad View Post
The health problems of microgravity (effectively zero gravity, as on the ISS) are lethal long-term. We've gone about as far establishing that as possible, short of leaving an astronaut in orbit long enough to actually die from it. The countermeasures (hours of exercises per day) only slow down the damage.

It's extremely likely that the health effects of fractional (e.g. Mars or lunar) gravity are less severe than those of microgravity. It's possible there are no real problems with it at all, aside from (as in the common SF trope) not being developmentally adapted to full earth gravity and so being unable to relocate there without prosthetics. But if there are other long-term effects, we don't know what will suffice to counter them (i.e. over a lifetime). A few hours a day on a tilt-a-whirl would be fairly easily manageable. Full-time on the tilt-a-whirl during pregnancy would be onerous, but hey, the survival of the species is at stake so you do what you gotta. But if you need the whole population living on the tilt-a-whirl all the time, it multiplies the cost of habitable space on the Martian surface by something like an order of magnitude.
That's all quite reasonable. I would guess that fetal development will require something quite close to 1g, though how close I won't guess. On the other hand when it comes to long term effects on adults, even if a few hours/day isn't effective, which I would also guess that it would be*, a few months on a treatment center in between stints of a few months at low-g should be (how long does it take astronauts to fully recover from a long stay on the ISS (where the problems of bone loss would be less severe per unit time)?

*Our bodies are quite good at adapting to stress, it's only the long term absense of that stress that leads to problems in living in zero-g. A few hours/day should be enough to induce that adaptive response. On the other hand it's not clear to me using sleep time would be sufficient as there's not that much load on the bones during sleep.
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Old 8th December 2018, 07:27 AM   #412
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Well, in my imaginary scenario they'd spend more like 16 hours a day on the centrifuge. Which would presumably involve at the very least some walking around and sitting, even if someone absolutely can't be convinced to spend some time on a treadmill or ergonomic bike. It's only when they have to do their job that they'd be in microgravity, and that mainly because some things can't be put on the centrifuge (e.g., maintaining the solar panels outside would still be microgravity) and some I really don't want to for cost reasons (e.g., it would take an insanely reinforced centrifuge to hold a nuclear reactor at 1g.)

So anyway, you'd spend some 8 hours or so in low g, then have 16 hours or so to recuperate in more acceptable g.

IMHO it should be enough to keep people at least reasonably healthy. With the caveat that I'm no doctor, so MHO doesn't have to count for much.
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Old 8th December 2018, 10:03 AM   #413
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Originally Posted by erwinl View Post
Just leave Matt Damon.

It's the Princesses of Mars that need rescuing!
Read the books, watch the movies (if you can find them now...……)...
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Old 8th December 2018, 10:14 AM   #414
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Originally Posted by 3point14 View Post
If it's practically a vacuum, does that make storing energy in a flywheel practical?
Well, you'd still have friction in the bearing, especially if the dust can get into it. Which, if it's not somehow sealed off, it will.

But let's do some maths there. You know me, I'm like math's little bitch. I keep coming back for more.

So let's say our whole colony needs only 1MW worth of power on the average. Which is actually very very Spartan, especially if you want to have 160 humans so they can at the very least have enough genetic diversity for a backup.

Let's say you want to hold power for a month. (Again, I'm going low. There have been recent storms that lasted a lot longer.)

so 1MW x 86400 s/day x 30 days = 2592000 MJ = 2.6 TJ

that's how much energy you'd have to store in the flywheel.

Now, that's pure kinetic energy. Assuming an ideal flywheel where the mass is all concentrated at the edge (or the vast majority of it, anyway) you need mv2 to be a little over 5*1012. So if we have a flywheel weighing 5000 TONS, its edge would have to be going at 1000m/s. You can plug in your own desired radius to get the RPM, but the edge is going at nearly mach 3 in any case. A bit more if it's a less ideal flywheel.

I'm thinking though that if you make it too large, the tensile strength of steel (or really ANY material you're using) isn't going to cut it.

Edit: the same applies, btw, if you have 5000 tons worth of lighter wheels. If you have 5000 flywheels, weighing 1 ton each, well, you still get the edge going at nearly mach 3 for each of them.
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Old 8th December 2018, 10:31 AM   #415
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That's an awful lot of flywheel.

Thank you for the maths!
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Old 8th December 2018, 11:27 AM   #416
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Originally Posted by 3point14 View Post
That's an awful lot of flywheel.

Yeah, but we can solve the power storage and the artificial gravity problems together! A rotating habitat with a rim mass of 50,000 tons (including contents) and a diameter of 150 meters (about the size and mass of a large modern stadium) would only need a rim speed of about 32 m/s to store your 2.6 TJ. That would be about 2/3 g centripetal acceleration, or a resultant of about .76 g. You get about 70,000 square meters of living and working space.

Of course, you'd lose your artificial gravity temporarily when you have to draw down significant amounts of that reserve power (but you'd only do that in emergencies, surely), and your habitat will seem a bit tilted until you can rev it up again.
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Old 8th December 2018, 11:59 AM   #417
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Hmm, I like that idea. Though I think 50,000 tons is a bit much. That's the weight of a bloody battleship.
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Old 8th December 2018, 12:07 PM   #418
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Hmm... could you please run the maths past me, though? When I do it in my head, it ends up about 2 orders of magnitude too short for 2.6TJ. Of course my maths could be wrong, but I'd like to learn where I went wrong with it.
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Old 8th December 2018, 12:23 PM   #419
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Never mind, I think I made a calculation error. It needs 10x more energy.

For instance, 4x the radius, 2x the rim speed (so 1/2 the rpm), and 2.5x the mass.

ETA: No, even that's not enough; I was even farther off.
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Old 8th December 2018, 02:33 PM   #420
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Ah. Well, for once I'm sorry to have been right. I was starting to like your centrifuge doubling as a flywheel idea.
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Old 10th December 2018, 05:18 AM   #421
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BTW, just to make it clear, just beacause the number is big, it doesn't mean it's impossible to store it. Just not in a flywheel. About 5000 tons of li-ion batteries should just about store that much. And would only cost about half a billion for the batteries, and a fair bit more for the transport.

Just, well, hope the batteries don't blow up, like li-ion occasionally does, or you'll be able to see the resulting crater from Earth
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Old 10th December 2018, 06:45 AM   #422
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Does anyone remember the old "solar power satellite" concept?

Such a thing might work better for Mars than for earth. For instance if the transmitted microwave power went off target, the colonists would still be safe due to the same radiation shielding that was protecting them from all the other radiation.

(But would a dust storm block the surface power reception? If so, they're of course no better off than if the panels themselves were on the surface.)

To be able to maintain it themselves, the colonists would need to maintain a space flight capability. But with Mars gravity, that might not be much more difficult than maintaining all the other technology they would need.
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Old 10th December 2018, 07:15 AM   #423
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Bingo. The problem is that when there's a dust storm, you literally can't see the sun for all the dust. I don't expect a satellite to do much better there.
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Old 10th December 2018, 09:41 AM   #424
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And whatever panels you use might need some built-in wipers. There will never be any rain to wash off the accumulated dust. There are cleaning eventWPs, but you might not want to rely on them.

Down here in Greece we quite often get saharan dust blowing in. It can make my car undriveable unless I use the screen washers.
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Old 10th December 2018, 09:56 AM   #425
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Originally Posted by HansMustermann View Post
Bingo. The problem is that when there's a dust storm, you literally can't see the sun for all the dust. I don't expect a satellite to do much better there.
I'm sure the Icarus from Die Another Day can break through. Can't speak to the safety of anyone it targets, however.
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Old 10th December 2018, 10:08 AM   #426
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Originally Posted by GlennB View Post
And whatever panels you use might need some built-in wipers. There will never be any rain to wash off the accumulated dust. There are cleaning eventWPs, but you might not want to rely on them.

Down here in Greece we quite often get saharan dust blowing in. It can make my car undriveable unless I use the screen washers.
Well, just as long as you don't end up polishing those panels an opaque white, while rubbing the dust on them with the wipers. I know at least the moon dust it's not the rounded particles of dust on Earth, but some rather jagged rock fragments. I'm sure some of the dust on Mars has been around the block often enough to have gotten rounded, but anything from recent enough impacts AND anything from humans digging a bunker there, has got to be the jagged kind.
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Old 15th December 2018, 09:03 AM   #427
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Originally Posted by Belz... View Post
I'm sure the Icarus from Die Another Day can break through. Can't speak to the safety of anyone it targets, however.
I was thinking of “Real Genius,” which was both funny on purpose and more realistic.
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Old 17th December 2018, 03:19 AM   #428
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Originally Posted by autumn1971 View Post
I was thinking of “Real Genius,” which was both funny on purpose and more realistic.
Yeah, that was a pretty fun movie.
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Old 17th December 2018, 06:08 AM   #429
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My new Mars colonization plan*:

Build a self-reproducing robot that is also capable of building several different designs (similar to an ant queen which can build new queens, workers, drone, soldiers, etc.). Design these robots to be able to operate on mars and utilize local materials for their reproduction.

Some of the designs will also do things other than reproduce, including building local infrastructure, like solar panels, railways, etc.

Let these robots loose on Mars and with a designed in goal of covering the planet in solar panels and mining local resources.

Have them also build large power transmitters which can beam the power back to the Moon in the form of lasers which can be recieved in large collecting stations.

Use this power to power lunar industry.

Steps of the plan:

1. Wait one to two hundred years for the underlying technology to be developed.
2. Initial R&D to develop the specifics of the project.
3. Building the initial prototypes.
4. Launch them to Mars.
5. Wait a few hundred more years for them to spread and develop the entire Martian surface.
6. Profit.

*Admittedly it may not count as colonisation when no humans ever set foot on Mars, but it's close enough for me.
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Old 17th December 2018, 07:13 AM   #430
HansMustermann
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Well, that still puts you back to square one, when it comes to why a colony would be super-expensive.

Just to produce the chips for the army of robots, you need some silicon foundries. You need mines for all sorts of materials, including the trace elements for those electronics and the solar panels and batteries. All those tend to not be all found in one place even on Earth, so then you need an infrastructure to haul and process all that stuff. Etc.

The idea that some robot would play in the dirt a bit and find all it needs to make another robot is... not very realistic.

Anyway THAT is the actual problem if the goal is to have a viable backup on Mars. To have your reproducing robots you need to have first solved that problem. But if you solved that problem, you don't really need the robots any more. You can just put the humans there too, if you solved that.
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Old 17th December 2018, 02:30 PM   #431
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Where's Markie? Surely he has a suggestion for the power supply problems at Mars? Plenty of H2O on Mars. Solar power to split off the H. Hydrinos to the rescue! Next year, maybe.......
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Old 17th December 2018, 04:18 PM   #432
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Originally Posted by HansMustermann View Post
Well, that still puts you back to square one, when it comes to why a colony would be super-expensive.

Just to produce the chips for the army of robots, you need some silicon foundries. You need mines for all sorts of materials, including the trace elements for those electronics and the solar panels and batteries. All those tend to not be all found in one place even on Earth, so then you need an infrastructure to haul and process all that stuff. Etc.
That's assuming your robots use silicon chips. Our brains don't require silicon, but are still pretty good at information processing.

Could we design "robots" through genetic engineering rather than traditional design that could actually function on Mars? Perhaps some combination of the two? Perhaps a whole new design that shares many similarities with life but uses a different resource chain? The requirement for liquid water seems pretty tough to get over, but things that tunnel through the planet and melt the ice found underground might be conceivable, anyway.

Quote:
The idea that some robot would play in the dirt a bit and find all it needs to make another robot is... not very realistic.
It works here on earth...

Quote:
Anyway THAT is the actual problem if the goal is to have a viable backup on Mars. To have your reproducing robots you need to have first solved that problem. But if you solved that problem, you don't really need the robots any more. You can just put the humans there too, if you solved that.
Not sure what you mean here. If we have these advanced robots, Mars is still a a desolate environement for humans. We could use the robots to build shelters and stuff on Mars, I guess (if they actually worked).

Anyway, I was half-joking. But only half...
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Old 18th December 2018, 03:26 AM   #433
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It works here on Earth because we've had billions of years worth of bacteria to make that dirt contain everything you need. That's your infrastructure right there. The same doesn't already exist on Mars.
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Old 18th December 2018, 03:35 AM   #434
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Originally Posted by HansMustermann View Post
It works here on Earth because we've had billions of years worth of bacteria to make that dirt contain everything you need. That's your infrastructure right there. The same doesn't already exist on Mars.
Sure, Earth is a much easier environment for which to design a self-replicating robot.

Is it possible to design and build something that could work similarly on Mars? I don't think any currently extant organisms fit that bill, but they are also evolved for life on Earth, so that doesn't address the question of whether or not it's possible.

I'm not confident that it could be done on a small scale, but our ability to design the system for the environment means that even with the much more marginal environment on Mars it's at least conceivable that it could be done.

Could said robots do more than just reproduce and actually do real work on infrastructure development? That's expecting even more, but I think if we could achieve the first goal (of reproduction and spreading over the planet) then this second goal is likely to be possible.

I certainly admit that I haven't really said anything here except to suggest a possible concept for consideration, but I don't think your criticism rules it out.
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Old 18th December 2018, 05:10 AM   #435
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Well, it's not as much criticism as just saying that if you solved the pre-requisites for that, you've already solved the pre-requisites for a colony too.

The MAIN problem for a "humanity backup" colony is maintaining tech level and maintaining the colony. In your scenario, you have essentially even overshot that goal. You're several technologies ahead of being able to make a self-sustaining colony at that point.
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Old 18th December 2018, 05:57 AM   #436
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Well, I guess that's sort of my point. I think trying to do it with modern technology doesn't really make sense, but with more advanced technology it will almost happen naturally.

For those who want it to happen, pushing society toward a particular direction may cause that natural technological/economic evolution happen faster, which could be important if we think we might miss the chance entirely due to some other forces.
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Old 19th December 2018, 05:27 AM   #437
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Originally Posted by Roboramma View Post
Well, I guess that's sort of my point. I think trying to do it with modern technology doesn't really make sense, but with more advanced technology it will almost happen naturally.

For those who want it to happen, pushing society toward a particular direction may cause that natural technological/economic evolution happen faster, which could be important if we think we might miss the chance entirely due to some other forces.
This is what I meant by reaching a Clarke's 3rd law level of technogy before we could build a self sustaining colony, and if we have that technology than all the scenarios envisaged in this thread as extinction events for humanity (that a Mars colony would protect against) are no longer extinction events, they become inconveniences at worse.
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Old 19th December 2018, 10:05 AM   #438
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Originally Posted by smartcooky View Post
For starters even though Venus is closer to the Earth than Mars, the tyranny of Tsiolkovsky's rocket equation means that getting to and from Venus is much harder than getting to and from Mars. This is because Venus is deeper into the Sun's gravity well;
Nope. When it comes to going from one heliocentric orbit to another, Venus takes less delta V.

Earth to Venus departure Vinf: ~2.5 km/s
Earth to Venus arrival Vinf: ~2.7 km/s
Total Earth to Venus Vinf: ~5.2 km/s

Earth to Mars departure Vinf: ~3 km/s
Earth to Mars arrival Vinf: 2.6 km/s
Total Earth to Mars Vinf: ~5.6 km/s
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Old 19th December 2018, 11:16 AM   #439
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Originally Posted by smartcooky View Post
Thinking long term, Mars is also the best option for terraforming.
Terraforming is implausible science fiction.

Any space settlements are going to be wholly enclosed artificial environments. On the Moon or Mars it would be underground habs.

Given the very mild temperature swings at the lunar poles, constant sunlight, and water and other volatile ices in the lunar cold traps, the moon is the best candidate for near term settlement.
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Old 19th December 2018, 11:22 AM   #440
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Originally Posted by GlennB View Post
Before you mention terraforming again, could you at least have the decency to calculate a ballpark figure for the tonneage of O2 it would take to make a breathable Martian atmosphere, ballpark figures for the tonneage of raw materials required and the energy input?

Just typing key words like 'terraform' won't achieve a damn thing.
I provide those number here

Terraforming Mars isn't remotely plausible.

If we did have the wherewithal to crash comets and volatile rich asteroids into Mars, we could also build biomes on said asteroids and comets. Which would give us much more real estate than terraforming a rocky planet or large moon.
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