Re: the un-economics of space travel

From: Alex Terrell (alexterrell_at_yahoo.com)
Date: 01/29/05 

Date: 29 Jan 2005 06:34:50 -0800

George William Herbert wrote:

> There is so much wrong with this that it's hard to know where to
> start here...

Agree with all you say. One thought/question -
>
> One:
>
> Titanium ore isn't that scarce on earth: it's about 0.86% of the
crust.
> There are plenty of high concentration titanium ore bodies around.
>
> Titanium (metal) is expensive and has been rare at times because
> it takes so much energy to separate titanium metal from its ore
> (titanium oxide etc).
>
That can't be the whole story - estimated extraction energies* are:

Source Energy required O2 prod./metal prod.
----------------------------------------------------
Al203 -> Al 28KWh/kg 0.90
Fe203 -> Fe 7KWh/kg 0.43
Fe304 -> Fe 5KWh/kg 0.38
Si02 -> Si 25KWh/kg 1.13
Ti02 -> Ti 15KWh/kg 0.69
----------------------------------------------------

Yet aluminium is much more widely used. Titanium is also difficult to
work - it doesn't roll well, and it has an awkwardly high melting
point. And performance wise, it's not that much better than
Aluminium/lithium alloys, and for many applications not as good as
Carbon Fibre.

*This is from: http://www.abo.fi/~mlindroo/SpaceExp/Slides/sld002.htm
I assume the figures are KWhr per kilo of metal.

Alex