the N, on 15 May 2012 - 04:01 AM, said:
I've notified Saru and he has fixed the link.
the N, on 15 May 2012 - 04:01 AM, said:
About water, I tought that comet water wasnt salt.
And your point is?
There seem to be three very fundamental issues which you have either overlooked or not understood:
- The nature and composition of comets
- The way the natural water cycle works
- Basic economic commonsense
Let's address these issues one by one.
The nature and composition of comets
Comets are often described as dirty snowballs. This is an over simplification. As well as being a mixture of water ice, dust and rock there are other chemicals present too, such as ammonia, carbon monoxide, carbon dioxide, methane, methanol, hydrogen cyanide, formaldehyde, ethanol and ethane, long-chain hydrocarbons and amino acids. Your comet water may not be salty, but it is far from pure.
This water ice isn't sitting nicely on the surface either. Comet nuclei have a crust of dark material, probably made up of long chain organic material. The water ice is below this.
Next we have to consider the orbits of comets. These tend to fall into two main types, short period and long period. Both types present problems for your idea.
Short period comets have well known orbital parameters and are the easiest to send spacecraft too. The problem is that because they have made many passes of the sun they have lost a large amount of their volatile material.. including water.
Long period comets, on the other hand, maybe virtually pristine, containing almost all their water. The problem is they arrive unexpectedly. There is no way of knowing when a decent one will arrive.
Even assuming you do decide to mine the water on a comet the elongated nature of their orbits present you with a problem. If you mine them when they are close to the sun (and therefore the earth) you have very little time. They move rapidly through the inner solar system before disappearing back into the depths of space. This need to work quickly makes things more difficult (and remember, in economic terms, difficult = expensive). On top of this when a comet is close to the sun it starts to out gas. Volatile material boils of, breaking through the crust and forming the comet's coma and tail. This out gassing would make the comet a difficult, if not dangerous, place to work.
The alternative would be to work on the comet when it is a long distance from the sun. This way the comet would be more stable and you would not have to rush so much. The problem here is that we are talking about distances beyond Jupiter's orbit. Transporting water over those kinds of distances would be expensive.
The natural water cycle
The reason areas have drought is not because Earth lacks water, it's because fresh water doesn't always fall where we want it to.
You have been a bit vague in your posts, but I'm assuming you want this comet water to supply drought hit areas. You need to think what will happen to that water. After use it will enter the water cycle. It will either evaporate to become rain somewhere else eventually finding its way to the ocean, or it will be pumped into a river where it will find it'd way to the ocean. Your comet water will only be used once then it will be gone. Then what? Mine more and more comets? You may not have noticed, but one thing this planet doesn't need is rising ocean levels.
Economic common sense
In my first reply to you I asked you a simple question. So far you have failed to answer it, so I'll ask again:
Waspie_Dwarf, on 14 May 2012 - 11:11 PM, said:
How can it be easier and more cost effective (and for that matter a more efficient use of energy) to bring a comet to Earth than desalinate ocean water and pump it to where it is needed?
Your answer was simply to say that cometary water isn't salty. But that is the whole point of desalination. From a scientific point of view it is extremely simple. Heat salt water so that the water evaporates. Collect the water vapour and cool it. What you have done is collect fresh water and leave the salt behind.
The main problem with desalination plants is that they require large amounts of energy in the form of either heat and/or electricity. However many of the worlds drought zones are in hot countries, where there is a vast amount of free solar energy.
Even if you do reject the idea of desalination there is a much closer, cheaper and technologically simpler source of water ice. It would be easier to tow an iceberg to a drought zone than to tow a comet to one.
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