[nwallin]

The Battle of Midway was fought in spectacularly deep water, on the order of 17,000-18,000 feet deep. This would make salvaging difficult, if not impossible. Scapa Flow is shallow enough for divers.

Once we run out of cheaply salvageable steel, we'll likely turn to steel smelting processes that do not introduce air into the steel. These processes require dramatically more energy and are thus more expensive, but will still be way less expensive than attempting to salvage at deep ocean depths.

[awalton]

> Once we run out of cheaply salvageable steel, we'll likely turn to steel smelting processes that do not introduce air into the steel.

This would be exceptionally difficult, as oxygen is a basic requirement for steel making as we have ever known it. Steel is made from iron mixed with carbon and then heated to melt. Then oxygen is added which burns the excess carbon into carbon dioxide and reacts with all of the other reactive contaminants and brings them to the surface where they can be cupped off as slag. The melt is poured and cooled and you have steel. Early steel processes used air, blast into the furnace with high powered pumps. Modern steel is made with purified oxygen from cryogenic processes (and there are even designs floating around for steel mills which use the turboexpander from the oxygen processing to help generate electricity to drive the mill).

Without oxygen, you'd have to start with very, very clean iron ore (containing nothing but iron and whatever you wanted to alloy with the final steel), and add exactly the right amount of carbon (which is also exceptionally difficult, since carbon is light and the heat will want to make it sublime anyway). Odds are such a steel would still contain so much impurity as to require a second melt in a vacuum arc furnace, which also would dramatically drive up the cost.

While there might be a future making steel like this in space, I'm not counting it as very likely in the slightest to happen in this century.

It's much easier to use exceptionally clean oxygen - the mill could use an oxygen generation process (like a hydrogen peroxide chemical process plant being added to the mill), or by ultrafiltration of the process oxygen (which seems more realistic all told).

[burfog]

Start with iron pentacarbonyl, which is conveniently a liquid that can be distilled. That gets rid of nearly all impurities.

[Godel_unicode]

Iron bottom sound would definitely be a better bet, although the fact that it's a grave site definitely gives pause. Scapa Flow is relatively unique in that it's a large collection of ships, without being a grave site, and being near the surface.

[ars]

> steel smelting processes that do not introduce air into the steel.

Air is perfectly fine. Both Oxygen and Nitrogen do not stay radioactive for longer than a few seconds. It's CO2 that is the problem, specifically the carbon.

And of course any other random impurity.

They could just use cryogenicaly distilled air, and take the nitrogen-oxygen part (the boiling points are very close).