posted
Okay, so I've been thinking about this, lately. I was rereading Red Thunder, and I sat down to figure out how long it would take to get from the surface of the Earth to the surface of the Moon if you could accelerate constantly at one gee for half the distance, and then decelerate at one gee for the rest of it.
Discounting the gravitational pull from both bodies (because it's been too long since I did this kind of calculation, and I didn't feel like looking it up), it would take about 3 hours and 44 minutes to get from here to there.
So given the possibility of someone figuring out how to get that constant acceleration, I was thinking about how we might go about terraforming it. After all, it's virtually a sister planet, given its size, so why not start there?
The first thing would be to get an atmosphere there. Would it be feasible to grab a comet or something that has a lot of ice in it and plop that down there? Would it sublimate to gas, or just sit there like a frozen lump?
(Sorry if this sounds disjointed. I broke my thumb yesterday morning and took vicodin last night, and I'm still a little fuzzy.)
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posted
We need to drill a hole down into the the moon's center, and pump it full of lead. That will increase the moon's mass, and will thusly increase the moon's gravitational footprint.
PRESTO! Now it's got enough gravity to hold an atmosphere.
Then, we take all of the ocean water that is flooding over our cities because of the moon's newfound strong gravity, and send it up there!
quote:Originally posted by Scott R: We need to drill a hole down into the the moon's center, and pump it full of lead. That will increase the moon's mass, and will thusly increase the moon's gravitational footprint.
PRESTO! Now it's got enough gravity to hold an atmosphere.
Then, we take all of the ocean water that is flooding over our cities because of the moon's newfound strong gravity, and send it up there!
WATER!
GRAVITY!
ATMOSPHERE!
We'll feed the rats to the cats and the cats to the rats, and get the cat skins for nothing!
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posted
I'd love to live on a planet that was filled with lead. Earthquakes (or Moonquakes, I guess) would be especially deadly. We could then send up all of our toxic waste and keep it in giant, hastily built vats built on any developing fault lines over the pools of liquid lead. Awesome!
quote: After all, it's virtually a sister planet, given its size, so why not start there?
Lisa, the moon is no where near a sister planet. This like provides the best representative diagrams of earth and moon size and distance. I use it for astronomy presentations all the time: LINK!Posts: 1711 | Registered: Jun 2004
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Hell, I'd settle for a big dome. That would be so awesome to live in a colony somewhere other than Earth. Granted, placing it would be tricky what with that whole Light Side and Dark Side thing. *cues Starwars reference*
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posted
I'd think that a series of tunnels and caverns would probably be a better bet than a dome--it would be more resistant to impact from space debris, naturally insulatory, and a good shield to protect us from cosmic rays.
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The problem is that 1 in 4 people exposed to cosmic rays develop a really nasty skin condition.
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Then you have to invest in a pair of spandex briefs. Never really seemed fair that the one guy on the team with the nasty skin condition had to wear less clothing than anybody else.
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quote:Originally posted by sylvrdragon: Hell, I'd settle for a big dome. That would be so awesome to live in a colony somewhere other than Earth. Granted, placing it would be tricky what with that whole Light Side and Dark Side thing. *cues Starwars reference*
Tricky? Why, you don't know if you want to always see the Earth in the sky?
Or by Dark side / Light side do you mean the couple weeks of daylight followed by couple weeks of night? (which would be true of everywhere except at the poles when pointed slightly towards, or away from the sun.)
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quote:Originally posted by sylvrdragon: Hell, I'd settle for a big dome. That would be so awesome to live in a colony somewhere other than Earth. Granted, placing it would be tricky what with that whole Light Side and Dark Side thing. *cues Starwars reference*
Tricky? Why, you don't know if you want to always see the Earth in the sky?
There's a benefit to being on Farside. Snoopy Terrans can't spy on you there.
quote:Originally posted by Slim: Or by Dark side / Light side do you mean the couple weeks of daylight followed by couple weeks of night? (which would be true of everywhere except at the poles when pointed slightly towards, or away from the sun.)
Is that true? If Luna is orbiting Earth, wouldn't it have more frequent day/night cycles than that?
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posted
No problemo, ya just balloon the Moon. Or rather put the Moon within two balloons.
The first balloon needs to hold ~2.9pounds of atmospheric pressure or 1/5th*atmosphere in oxygen to sustain humans. However, the stretching caused by that pressure over the distance of the Moon's circumference is enough to burst a balloon. Hence you need to counteract that stretching with compression. Gravity acting upon the mass of the balloon creates weight, which acts as a compressive force. Balancing the compressive force of the balloon's weight with the stretching force of the atmospheric pressure would prevent bursting.
On Earth, the weight of a 33.9foot/10.34metre column of water produces a compression equal to 1*atmosphere. So the weight of 1/5th of 33.9feet, or a 6.78foot column of water would produce compression equal to 1/5th*atmosphere. But the Moon has only 1/6th of Earth's gravity, and a given mass on the Moon would have only 1/6th the weight as it does on Earth. And it would take 6 times that 6.78feet, or the weight of a 40.7foot column of water to produce the compression equal to 1/5th atmosphere.
Thing is, water is scarce on the Moon. Or rather hydrogen is scarce; oxygen can be cheaply mined&distilled locally. But the hydrogen needed to combine with oxygen to produce water would be expensive whether imported or as byproduct of Helium3 mining. Countering that expense are the facts that: 1) Water is a nearly ideal radiation shield. An 8foot barrier of water is enough to decrease the level of radiation from nuclear reactor fuel rods in a cooling pond down to safe levels: ie lower than the high-energy radiation from the Sun and cosmic rays hitting the Earth's surface. 8feet of water would be more than enough to protect those on the Moon's surface from any solar flare or cosmic ray burst that Earth's surface life could survive. 2) Water would provide a temporary self-sealing barrier to punctures produced by small meteors. Water's evaporation into a vacuum lowers the temperature until the fluid turns into ice. 3) Water is a necessity for life. Having a large reservoir overhead is a BIG plus. 4) Water stores LARGE amounts of heat.....which is a useful quality in providing a thermal buffer between daytime temperatures and nightime temperatures. 5) Aquaculture is the most efficient means of producing high-quality protein. And little fishies swimming overhead would provide a welcome taste treat. 6) Under the Sea is the perfect anthem for a buncha Lunatics.
So subtract 8feet of water from the 40.7feet of water needed to produce the weight providing the compression countering atmospheric pressure to get the mass equivalent of 32.7feet of water to provide the rest of the compression Cuz to produce weight, it doesn't matter whether the mass of a kilogram of water is being used or the mass of a kilogram of lead. For the skin of the balloons themselves, cheapness nearly trumps over all other factors.
Transparency would be nice so that the Sun can provide light for photosynthesis in the plants and phytoplankton which provide food for the critters. Fortunately, the Moon has LOTS of silicon and oxygen: the primary ingredients of glass. Silicon dioxide is 2.2 times as dense as water, and dividing 32.7feet (water column) by 2.2 gives us ~14.8foot as the thickness of glass that would provide the rest of the weight needed to counter atmospheric pressure. Say a 7.4foot thickness for each balloon.
So whatcha end up with is: 1) The Moon's surface 2) The artificial atmosphere 3) Teathers/towers to hold the balloon skin above the Moon's surface. Otherwise the balloon will rise on one side, and put unacceptable pressures on the other by falling onto mountain peaks, etc of the surface. "Ringworld is unstable." 4) A 7.4foot-thick segmented&reinforced glass"balloon" providing the bottom of the "sea" and a third layer of protection from small-meteor strikes. 5) Light-pipe teathers from the top of the second glass balloon to the bottom of the first balloon. Cheap glass is nowhere near as efficient at transmitting light as fiber optic cables. Properly-made lightpipe cables would act as "tv screen pixels" allowing a good view of Earth and Space. 6) Water. Circulation pumps drive the water around the Moon to prevent large swings in temperature between the monthly day&night cycle from shattering the balloons. And prevents water from freezing: water expands when turning to ice, which would also put unacceptable internal pressure between balloons. And aerating pumps to exchange gases between the Moon's surface and the sea. 7) The second 7.4foot-thick segmented&reinforced balloon to keep the water from boiling off into the vacuum. The outer balloon would also provide more than enough radiation shielding for the plankton and fishies.
Just offhand thoughts to be contrarian. I'm sure there are other engineering challenges. And the individual glass"balloon" thicknesses were chosen purely for simplicity of illustration.
The other thing to consider is that such "balloon"surfaces can easily be stretched across craters, giving LARGE "outdoor"living areas while preserving the vacuum on the rest of the Moon. And a vacuum is a HIGHLY desirable characteristic. Without atmospheric resistance, a centrifugal sling could boost products to orbit or escape velocity for pennies per pound. Spacecraft carrying more delicate objects such as humans could be launched by linear-accelerators at a cost lower than a short-hop airline flight. An orbiting rotovator can set down a load on the surface with no (or almost no) rocket-braking. Similarly, the rotovator could lift a load from the surface into orbit at minimal cost (excluding initial construction expenses).
posted
Woo! Crystal spheres, a reservoir of water held above the firmament...all we need is to discover water under the surface so that we can have the Fountains of the Deep and we'll be all set!
Seriously, though, that was interesting, aspectre.
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posted
One thing else to consider: the Moon's surface is about as dark as coal. Extremely weak background lighting and a LARGE surface area is what makes the Moon('s reflection of sunlight) appear bright to us. Ballooning the Moon will make it a LOT more reflective. Probably enough to easily read during full moons. Such a high light level would hafta have a MAJOR effect on life on Earth, especially on nocturnal animals.
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Lisa, One lunar day is the same as one lunar revolution around the earth. It's why (more or less) the same side always faces us. It's an effect calledgravitational locking.
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aspectre, as long as we're going so far as too balloon the moon, couldn't we just take it the next step and balloon the moon with a dark, non-reflective material?
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quote:Originally posted by aspectre: One thing else to consider: the Moon's surface is about as dark as coal. Extremely weak background lighting and a LARGE surface area is what makes the Moon('s reflection of sunlight) appear bright to us. Ballooning the Moon will make it a LOT more reflective. Probably enough to easily read during full moons. Such a high light level would hafta have a MAJOR effect on life on Earth, especially on nocturnal animals.
Paint the outside black.
I'm still not clear on why Luna can't hold an atmosphere. I mean, Mars has one, thin as it may be. Why couldn't Luna? And if enough air were dumped on Luna, why wouldn't it stay there? It's not as though it has no gravity at all.
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I've tried putting large objects inside balloons before. It's fun, but when things go wrong... imagine a moon-sized baloon doing the flatus dance around the solar system.
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quote:Originally posted by aspectre: One thing else to consider: the Moon's surface is about as dark as coal. Extremely weak background lighting and a LARGE surface area is what makes the Moon('s reflection of sunlight) appear bright to us. Ballooning the Moon will make it a LOT more reflective. Probably enough to easily read during full moons. Such a high light level would hafta have a MAJOR effect on life on Earth, especially on nocturnal animals.
Paint the outside black.
He was specific about it being clear so as to allow for photosynthetic organisms to live within it.
quote:I'm still not clear on why Luna can't hold an atmosphere. I mean, Mars has one, thin as it may be. Why couldn't Luna? And if enough air were dumped on Luna, why wouldn't it stay there? It's not as though it has no gravity at all. [/QB]
Mar's gravitational pull is .37 of Earth's, while the moon's is 16.2%. The pull of gravity on Mars is strong enough to trap some gasses, but that of the moon isn't.
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posted
The moon is also closer to the sun than Mars is. The reason the atmosphere doesn't stay on the Moon is because the solar winds blow the atoms away into space. You need a stronger gravity than the Moon has to keep them from escaping.
(At least according to the sites I found while googling. Don't want to pretend expertise I don't have!)
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Oh, yeah, I'm a total layman too--my degrees are in Classics and in Education; nothing sciency at all there. I just like reading about this stuff, and some of it sticks; I could easily believe that there might be reasons other than the ones I'm aware of for phenomena like this.
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quote:I'm still not clear on why Luna can't hold an atmosphere. I mean, Mars has one, thin as it may be. Why couldn't Luna? And if enough air were dumped on Luna, why wouldn't it stay there? It's not as though it has no gravity at all.
It has to do with the energy requirement to be accelerate individual gas molecules so that they are travelling fast enough to escape the moon's gravity.
On the earth, a helium atom at room temperature has enough energy to travel at escape velocity, provided it doesn't collide with other molecules. Helium migrates up through the atmosphere until it reaches a point where the atmosphere no is no longer in the viscous regime, so individual molecules act as ballistic projectiles. At this point, a helium molecule with the same kinetic energy for room temperature at sea level is traveling at escape velocity, and it simply heads off into space.
Hydrogen could do the same thing, except that it is usually locked together with oxygen to form water, so it's too heavy to escape.
Mars' atmosphere is mostly CO2, which is pretty dense. It might be possible to create an atmosphere around the moon using argon or chlorine molecules though. Or mercury vapor. That should be heavy enough. Yeah, that's the ticket.
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posted
It is true that the moon does not possess a gravity strong enough to hold onto an atmosphere permanently. But it seems to me that the atmospere would bleed off into space at a slow enough rate, that if it were regularly replenished, you could have a viable atmosphere. So whatever method you used to set up an atmosphere there in the first place, keep on using it now and then to maintain it at the desired pressure.
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You'd probably have to steal atoms from Jupiter or the other gas giants to do that. Sounds fun.
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Well, if we were dealing with the amount of technology needed to do this anyway, we might as well mine the outer planets for hydrogen.
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Ron: Why build a colony in which you have to replenish your atmosphere. Seems easier to live in caves (a la "The Gods Themselves) or bubbles, things like that, where you could preserve your atmosphere.
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It blows my mind that we went to the moon in 1968 or whenever... I mean have you ever seen the COMPUTERS from the 1960's?!
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There are certain factors which render it feasible or infeasible for a planetary body to maintain an atmosphere. At approximately 16% of Earth's gravity at the same distance from the Sun, our moon will not hold an atmosphere at all, much less one with the capacity to sustain life and burn out meteorite impacts.
Because of the atmosphere thing, you can't have uninsulated colonies. Because of the meteorite impact thing, you can't have surface colonies. Because of the lack of sufficient gravity to prevent space punies, lack of useful sustaining resources, and the lack of any real appealing reason to do so, you probably won't have 'burbs on Luna.
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quote:Originally posted by Samprimary: There are certain factors which render it feasible or infeasible for a planetary body to maintain an atmosphere. At approximately 16% of Earth's gravity at the same distance from the Sun, our moon will not hold an atmosphere at all, much less one with the capacity to sustain life and burn out meteorite impacts.
Because of the atmosphere thing, you can't have uninsulated colonies. Because of the meteorite impact thing, you can't have surface colonies. Because of the lack of sufficient gravity to prevent space punies, lack of useful sustaining resources, and the lack of any real appealing reason to do so, you probably won't have 'burbs on Luna.
The one thing you DO have, by virtue of that 16% gravity is a premade platform for a space station to get you to the rest of the solar system.
posted
I suspect one of the stable Langrangian points would be preferred. Even .16 earth gravities is a substantial cost sink.
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quote:Originally posted by Lisa: Paint the outside black.
He was specific about it being clear so as to allow for photosynthetic organisms to live within it.
The bottom outside. Not the top.
quote:Originally posted by Noemon:
quote:I'm still not clear on why Luna can't hold an atmosphere. I mean, Mars has one, thin as it may be. Why couldn't Luna? And if enough air were dumped on Luna, why wouldn't it stay there? It's not as though it has no gravity at all.
Mar's gravitational pull is .37 of Earth's, while the moon's is 16.2%. The pull of gravity on Mars is strong enough to trap some gasses, but that of the moon isn't. [/QB]
I don't see why. It's gravity, anyway. If it's there, what would make it leave? It's not like Luna rotates, right?
(Never mind. I saw the other answers. But I wonder how much of that is stuff that people have come up with to explain the fact that there isn't any atmosphere on Luna and how much of it is fact. I'd still want to try it.)
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quote:Originally posted by Tara: It blows my mind that we went to the moon in 1968 or whenever... I mean have you ever seen the COMPUTERS from the 1960's?!
We went to the museum, and saw footage from the moon landing in 1969. I'd never heard that about the landing module losing computer control and being manually landed with like 1 second of fuel left. Was that recently declassified material or something? I couldn't believe no one has made a movie about that.
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Did it lose computer control? I thought there were boulders on the assigned landing area so Neil Armstrong took manual control and moved horizontally to a clear spot.
As for the atmosphere problem, one analogy is boiling and evaporation. Molecules escape from boiling liquid just like molecules escape from atmospheres. If the gravity is too weak, the "lid" is off or only partially on.
Astronomers also use the term "evaporate" for stars that escape from clusters or the Milky Way, and similarly you could say that objects that escape from the Solar System evaporate.
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Originally posted by Lisa: "The bottom outside. Not the top." Meaning what?... to paint only the part exposed to the sun would 1. eliminate the desired effect of being able to grow plants 2. not work for long, because the same side of the moon is not always facing the sun.
Or that the plants would be grown beneath a clear layer under which was a black layer under which was a colony \ (clear shell( Plants (black shell( (Moons surface(
But then that doesn't resolve the reflection issue.
On atmosphere: particles move around because they got heated up from sunlight (at some level). This makes them wiggle about. Because of the intensity of the light at our distance from the sun and the weakness of the gravity preventing those particles from leaving the particles will leave.
My brother's explanation (at grad school for planetary astronomy): There's not enough gravity. So. The mean velocity of particles is greater than the escape velocity.
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