While visiting relatives in Georgia a few months ago, they had a story on the news asking what people think would happen in the next century. One lady said that man will land on a comet and tap it for water. I thought this was an odd answer, but does anyone know if it is possible? Thanks
I don’t know about a comet, but Isaac Asimove wrote a short story about people going to the rings of Saturn to bring back chunks of ice.
Comets are made of H<small>[sub][/sub]</small>0, along with many other compounds common in space. So there is water available there.
As to the practicality of doing so, I don’t think so.[ul][li]We don’t know when exactly comets are coming into the inner solar system. By the time we see them, it’s to late to put together an incepting space mission.[/li][li]They’re moving damn fast.[/li][li]It be expensive.[/li][li]Moving a comet would be near impossible.[/li][li]And even if all the above points could be addressed, landing something like that on Earth would not be a good idea. That’s what killed the dinos, according to one current theory.[/ul][/li]
Judges 14:9 - So [Samson] scraped the honey into his hands and went on, eating as he went. When he came to his father and mother, he gave some to them and they ate it; but he did not tell them that he had scraped the honey out of the body of the lion.
The reason for looking for sources of water in space is so you can use it as fuel and air (Oxygen and Hydrogen). Lifting water or fuel from the Earth’s surface is very expensive and takes up room you could use for food, equipment, tourists, lawn chairs and board games. The idea with the comet is that if they are indeed mostly water, you could take off with only a quarter tank of gas, rendevous with a passing comet and fill up for the rest of your journey to who knows where.
Elmer J. Fudd,
Millionaire.
I own a mansion and a yacht.
What a great beer you could make out of comet water! I mean the commercials alone would make Rocky Mountain spring water as lame as moose piss.
“…send lawyers, guns, and money…”
Warren ZevonUm, no. I don’t think comet water is that pure. It would need to be distilled.
Yes, if I remember correctly, there’s also ammonia and other wonderful stuff in it. Comet hair bleach?
An infinite number of rednecks in an infinite number of pickup trucks shooting an infinite number of shotguns at an infinite number of road signs will eventually produce all the world’s great works of literature in Braille.
Damnit, NTG, I knew I slept through a few college classes, but I thought I was at least semi-conscious in Astronomy 101. Are Saturn’s rings still composed of kryptonite?
“…send lawyers, guns, and money…”
Warren ZevonBluepony: Are Saturn’s rings still composed of kryptonite?
Yes. And Klingons are around Uranus. 
Judges 14:9 - So [Samson] scraped the honey into his hands and went on, eating as he went. When he came to his father and mother, he gave some to them and they ate it; but he did not tell them that he had scraped the honey out of the body of the lion.
Water is extremely precious if you’re going to do anything in space. You need a lot of it for life support - all those hydroponic farms or whatever you use to make food. And with a little electricity (which is cheap in space - just open a solar panel) you get hydrogen and oxygen to power your rockets. This is why there is so much interest in finding water on the Moon. It could make THE difference between an outpost living off the monthly supply ship from your government back home, and a self-sufficient colony.
Mining the comets for ice has been a subject of many science fiction novels. “Heart of the Comet” by Gregory Benford and David Brin is one of my favourite sci fi novels - it’s about a 76-year mission to alter the orbit of Halley’s Comet and steer it into Earth orbit. One of the novels by Allen Steele had something about it too.
The method in Benford book (which is supposedly based on actual calculations) was to give the comet a nudge near perihelion, which is the point in orbit where the comet is farthest away from the sun and moving slowest. If you push it the right way, you can make it pass by one of the planets on its way back towards the sun. If you do the near-miss just right, you can fling the comet into pretty much any direction you want. It’s basically the same ‘gravity assist’ that NASA probes often use. As for the actual nudging, you can just mount an electromagnetic launcher and fling away bits of the comet. Or explode a nuclear bomb on one side of the comet so that side vaporizes and pushes the comet in the opposite direction. If you want to do the steering closer to the sun, I suppose you could use a solar sail.
Just some further info: there are many comets which have very short periods. Presumably one of them could be used, though they may be a bit thin on the remaining water. And I don’t think the idea would be to land the comet nucleus by slamming it into the earth. 
Isn’t it true that all the water we have on Earth was brought to us by comets?
Of course not - water is cheap on earth!
On the other hand, some people (OK, some sci fi writers) suggest that slamming a comet on Mars may make it more hospitable there.
Landing on one? I don’t know about that, but remote controlled rendezvous with one and pick up some samples is probably a fairly high probability mission profile for the next half-century or so. Lots of good science to be done from that sort of a mission.
The implication of Homochirality of the precursor molecules for life is a medium hot topic in Xenobiology these days. Nothing like hard data to stir up that sort of debate. If we can get genuine Comet Stuff to examine, we can measure the proportions of amino acids and such. Non-organic hydrocarbons, the crystallography of extra solar condensates, isotope proportions, Helium traces, and a hundred other facts would keep half a hundred research teams busy for years.
The shopping list for the mission planners will be extensive. This ship will have to be orbited to intercept early, if possible, and make more than one sampling mission. We want the first sample from the coldest possible site, early in the orbit. Then we want samples of the tail, and then more samples from the surface, after solar influences. Magnetic scanning of the entire fly by of course, as well as visuals for the glamour shots. The ideal comet would have a long orbital period, hopefully in the thousands of year range, to assure the highest possible accretion of Oort/Kuiper debris to be evaluated. (The chance of a maiden fly-by is too small to add to the planning conditions, darn it.) That kind of mission would require an orbital break in the near Neptune distance range, to wait a few years or decades for the opportunity to match orbits with a likely inbound candidate.
Drinking water and rocket fuel don’t even make the list. Just having the chance to actually bring a kilogram of the stuff back is gonna be a long shot, unless we quadruple NASA funding for the next fifty years or so. But the interest is there, I assure you, from half a dozen unrelated branches of science.
<P ALIGN=“CENTER”>Tris</P>
Inspiration usually comes during work, rather than before it.
– **Madeleine L’Engle **
If you want water from the comet you’ll have to barter with the Heaven’s Gate people in the rocket behind it.
Triskadecamus:
SDMB, How do I freakin’ love thee. Let me count the ways. Wakes my brain up everyday.
(holy shit)…homochirality of precursor molecules…xenobiology…isotopes. I was going to expand further on my Comet Beer idea, but I think I’ll just let that one fall by the wayside.
“…send lawyers, guns, and money…”
Warren ZevonAWB the path of a comet is not that hard to calculate, had I not failed calculous I’d be able to show you.
Go here for all the info you’d like on comets: http://www.jpl.nasa.gov/comet/
our techonology is so advanced we’ve been puting telescopes almost right behind comets for about 4-5 years now.
hope this helps
I am a fire whose flames lick and spit at the boundless sky forever desiring wonderous consummation
-me
Nope.
Unfortunately, Comet Beer would be so expensive, only Bill Gates could afford a single case of it!
>< DARWIN >
__L___L