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  #21  
Old December 12th 04, 08:46 AM
Tommy
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I think he was commenting on the fact that most subsonic airplanes, cars
and the shuttle are made of aluminium not titanium. The last time I
checked titanium cost about 25$ per pound.

wrote:
Paul F. Dietz wrote:

How idiotic.



Do you have a solution that makes titanium refining no longer an
insurmountable obstacle to producing large amounts of titanium, or were
you just being glib?

Mike Miller, Materials Engineer

  #22  
Old December 12th 04, 09:32 PM
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Paul F. Dietz wrote:

If titanium had been all that desirable for the shuttle, more
capacity would have been added here. The cost of doing so would
have been a small fraction of the cost of the shuttle development.


This might be true for an extremely critical program with high titanium
demands, but generally the cost/difficulty/etc. of refining titanium
makes added titanium refining capacity an "insurmountable obstacle" for
most applications.

For example, even a national defense critical program like the SR71 did
not add titanium refining capacity. The Titanium Metals Corporation
produced titanium for the SR71 with titanium sponge obtained from the
USSR.

Mike Miller, Materials Engineer

  #23  
Old December 12th 04, 10:50 PM
Cameron Dorrough
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"Michael P. Walsh" wrote in message
...

Certainly automobiles are not made mostly of titanium and the Space

Shuttle
contains more aluminum than titanium. Not sure of the per cent

composition
of airliners, but I doubt it.


Airliners are mostly plastic these days (ie. kevlar and carbon composites) -
with a few bits of aluminium here and there. Metal is sooooo retro!! ;-)

Cameron:-)


  #25  
Old December 13th 04, 03:27 PM
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Paul F. Dietz wrote:
I repeat: if shortage of refining capacity for titanium in the US had
been the showstopper for an otherwise greatly superior material, that
capacity would have been added. The laws of physics and chemistry

don't
suddenly change at the US border.


Your point is only applicable to an extreme situation and trivializes
the effort involved. It's kind of like saying, "If the US needed to put
10,000 tons in orbit in a couple of years, the challenges are not
insurmountable." Well, the engineering and physics do not present
insurmountable problems, but there's more to launching a lot of payload
suddenly (or refining titanium) than just physics.
Mike Miller, Materials Engineer

  #26  
Old December 13th 04, 03:35 PM
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Cameron Dorrough wrote:

Airliners are mostly plastic these days (ie.
kevlar and carbon composites) -
with a few bits of aluminium here and there.


Large airliners are still primarily aluminum. For example, the upcoming
A380 giant is setting a record by being 25% composites by weight.

Metal is sooooo retro!! ;-)


Such was my thought when I specialized in composites and ceramics in
college. My first job was for a Navy subcontractor. I eagerly dove into
projects looking for the advanced materials in use.

Composites? Nope, steel.
Titanium? Nope, steel.
Ceramics? Nope, steel.
Stainless steels? Nope, normal steels.

Steel and aluminum are not retreating from use rapidly. They sit in
regions of materials properties where their combination of strength,
durability, weight, and cost will keep them in use for a long time.
Mike Miller, Materials Engineer

  #28  
Old December 14th 04, 08:44 PM
Ian Woollard
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Paul F. Dietz wrote:
Huh? Titanium the metal is common wherever you want to make it.
It doesn't occur at all in nature.

What may have been short was *refining capacity* in the US,
but that's obviously not an insurmountable obstacle.


No, there are no insurmountable obstacles to building titanium vehicles.

There are a number of difficulties:

a) the best ore is more common in non US countries, noteably Russia
b) US workforce experience with dealing with titanium was not high
c) titanium swarf is explosive
d) titanium requires specialist equipment to work, it's far less workeable
e) welding is more difficult than steel or aluminum
f) it's harder to refine

All of this pushes up the costs and decreases availability.

Problem a) was very significant at the time- the Russian block countries
had access to most of the alloys that were useable for building
vehicles. The titanium SR71 was built using material obtained using
clandestine means from Soviet companies.

A nickname for titanium was 'unobtainium'.

As I understand it, problem b) was perceived to be quite important when
building the Shuttle- workforce that had direct experience with titanium
were mostly assisting with black programs.

Note that the soviets who had greater access to titanium, didn't use it
very much, preferring to use much cheaper steel.

Paul


  #29  
Old December 14th 04, 11:01 PM
Cameron Dorrough
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wrote in message
oups.com...

Cameron Dorrough wrote:

Airliners are mostly plastic these days (ie.
kevlar and carbon composites) -
with a few bits of aluminium here and there.


Large airliners are still primarily aluminum. For example, the upcoming
A380 giant is setting a record by being 25% composites by weight.


By *weight*?? Have a think about that statement for a sec...

The difference in weight between, say, a B777 rudder (all composite except
for the Al center spar with the hinges on it) and a, smaller, B747 rudder
(all aluminium) is that 2 people can carry the first one and you need a
crane for the second.

By volume might be a better comparison - that's closer to 50% on the B777
and a lot more on the A380! :-)

Metal is sooooo retro!! ;-)


Such was my thought when I specialized in composites and ceramics in
college. My first job was for a Navy subcontractor. I eagerly dove into
projects looking for the advanced materials in use.

Composites? Nope, steel.
Titanium? Nope, steel.
Ceramics? Nope, steel.
Stainless steels? Nope, normal steels.

Steel and aluminum are not retreating from use rapidly. They sit in
regions of materials properties where their combination of strength,
durability, weight, and cost will keep them in use for a long time.


True, true - I was being more than a little tongue-in-cheek, but modern
composites will (hopefully) minimise their use eventually.

eg. a typical aircraft kevlar-honeycomb carbon-fibre sandwich is many times
stronger, more durable, lighter and maybe not yet cheaper than sheet steel
(but easier to fabricate into complex shapes) - but it just can't take the
heat that steel can - yet. :-)

Cameron:-)


 




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