On Aug 29, 8:07 pm, byblow wrote:
On Aug 26, 8:30 pm, Keith Henson wrote:

On Aug 25, 6:59 pm, byblow wrote:

What equipment, materials and amount of electricity are needed to
produce steel (in space) from ores found on NEOs?

It depends on the object. Some of them, 1986 DA for example, are
thought to be solid nickel-iron. Depending on what you wanted to do
with it, the material could be melted using an open ended induction
furnace, electromagnetically pumped out and rolled into I beams.

So the nickel-iron on a metallic NEO (like 1986 DA) is totally pure
and doesn't need to be refined?

It's hardly pure in the sense that it's got lots of different elements
in it and we don't yet have samples so we are not certain about what's
in it. As for needing to be refined, it depends on what you want to
use it for. Construction grade I beams, probably not.

Does it become nickel *steel* after it's melted?

It's been melted, billions of years ago. As for what you call it,
steel is what we call iron reduce from ore and refined to specific
composition.

Do you happen to know how many kilowatt hours it would take to melt a
tonne of nickel-iron using induction heating? How about to melt 100
tonnes?

It's easy enough to figure out. Iron is close enough to 56 g/mol. A
kg would be 17.8 mols. The specific heat is 25 J/mol/deg K. or 446 J/
kg/deg K. Iron melts at 1800 deg K. so figure heating it 1600 deg.
That would take ~714 kJ/kg. The heat of fusion is 13.8 kJ/mol or 246
kJ/kg, around 960 kJ/kg to heat and melt.

Given this is rough use 1000 kJ/kg. A kJ is a kW-s, so a 1000 kW (a
MW) would heat and melt a kg/s. Over an hour it would melt 3600 kg or
3.6 tons per MW per hour. 100 tons would take 27.8 MWh to melt.

This doesn't consider the thermal radiation loss from the induction
furnace.

In the context of a serious mining project, a kg/s doesn't amount to
much. The Morenci mine in Arizona processes a million tons per day or
around 11,000 kg/s.

A 5 GW power satatellite using 1 GW for the induction furnace would
melt 1000 kg/s. The estimated mass is 2 x 10^13 kg so at this rate it
would take 2 x 10^10 s to use it up or 634 years.