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I'm really struggling to understand a sentence from page 23 of A Deepness in the Sky

But you can't eat diamonds, not raw anyway. Without the usual mix of native volatiles and ores, fleet life would be very uncomfortable indeed.

  • Why does it say "But you can't eat diamonds, not raw anyway"? Does this mean that diamonds are processed into volatiles like water to make food?

  • And ores, for what are they used on the fleet, furniture?

  • Why does it say "uncomfortable"? Because of the volatiles (water) supply?

  • What exactly are "native volatiles and ores" used for on the fleet?

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The author refers later to 'volatiles plants', a technology which turn diamonds, or any other form of carbon, into useful products and even food and drink. Without volatiles (such as water ice) the system won't operate.

The author is also pointing out that without metallic ores, building new ships and maintaining the existing fleet would be next to impossible.

Pham snagged a bulb of the brew. The container was new plastic. Benny had some kind of in with the crews that ran surface operations on the rockpile. The little volatiles plant gulped in airsnow and water ice and ground diamond. . .and out came raw stocks, including the plastics for drinking bulbs, furniture, the zero-gee pool game. Even the parlor’s chief attraction was the product of the rockpile—touched by the magic of the temp’s bactry.

This bulb had a colored drawing on the side:DIAMOND AND ICE BREWERY , it said, and there was a picture of the rockpile being dissolved into suds. The picture was an intricate thing, evidently from a hand-drawn original. Pham stared at the clever drawing for a moment. He swallowed his wondering questions. In any case, others would ask them. . .in their own way.

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Both of the existing answers are good, but a glimpse of the chemistry behind the answers may be helpful.

There are four elements which are critical for life: earth, air, fire Hydrogen, Carbon, Nitrogen and Oxygen -- H, C, N and O. (There are others such as calcium, sodium, potassium, iron and sulfur needed also, but in comparatively trace amounts.) Carbohydrates, starches, sugars and the like are basically polymers of CH2O. Proteins are polymers of amino acids which have the general structure NH3CHRCOOH, where R is a add-on usually made of C, H and O.

Diamond is pure C. No matter what you do to it, you can't make any of the inputs for life without adding O, H and N. So with diamond but without a supply of volatiles also, you'd be dead. (Rich, perhaps, but dead.)

At our favored temperatures, most compounds of O, H, and N are gases or liquids, and gases and liquids go by the generic name of "volatiles". (There are also some very common carbon compounds which are common volatiles in space: carbon monoxide, carbon dioxide and methane are the most common.)

(I'm actually puzzled that they care about diamond, since it's not a particularly useful form of carbon and carbon is pretty common, anyway. But as a source of carbon, it's pretty sexy.)

Because the volatiles are, well, volatile, they tend to escape during planetary formation, and the smaller the planet the less able it is to hold onto volatiles. Smaller inner Solar System bodies like meteors and asteroids tend to be high in non-volatiles (iron, silica, carbon) and low in volatiles. Most plans for permanent settlements in space are focused on finding in situ sources of volatiles. (Consider the discussions of bases at the Lunar South Pole, which is believed to have deposits of water ice.)

So, bottom line, volatiles are expected to be the limiting resource pretty much anywhere in space where humans can survive.

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    Conversely, the Oort Cloud may have lots of volatiles, but a restricted supply of metals, especially if we're talking about technologically-useful metals like iron, nickel and chromium, so-called "rare earths," etc. Of course we may not want to live there if it's too hard to gather energy. – DavidW May 30 '19 at 19:45
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    Nearly the hardest thing to do in space -- after ensuring a supply of volatiles -- is to get rid of waste heat. If we ever make fusion workable, being close to the Sun and far from the volatile supply may be more trouble than its worth. – Mark Olson May 30 '19 at 20:10
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As pointed before, there are 2 main ingredients: carbon to make the structure of things (whatever they are) and ores, which would play the disolvent/mixer part of the job. Our planet and its life forms are mostly based on carbon and water as a disolvent, most xenobiologists think there might be other life forms out there based on slightly different elements and solvents, like silica and methane or ammoniac.

So no, no way they eat raw diamond back in the temp, dirty raw diamonds are fed into the machinery that (probably) crushes them to atom scale and resembles molecularly to a biofriendly form: from crystal to food.

Valorum quoted a fragment mentioning bacteria (the bactry, the core of any fleet or temporary settlement), do not forget they play a role transforming things for us here and now. Just scale this up.

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