Rüdiger Klaehn wrote:
Ed Kyle wrote:

[snip]
not. The second stage is of Aluminum Lithium, which
is stronger for its weight than the Aluminum used in
the first stage. Ice forming on the outside of the LOX
tank during prelaunch provides some insulation - and
the ice usually shakes off right at liftoff.

Last thing I read was that the upper stage is made from normal
aluminium alloy, because they could not find a reliable source for the
required LiAl alloy (translation: Somebody put some pressure on LiAl
manufacturers not to sell to spacex if they want to continue being
suppliers for the LiAl Shuttle ET).

That has reduced the payload by something like 100kg.

Hmmm. The SpaceX web site still says that the Falcon 1
second stage "tank structure is made of aluminum-lithium".
It says that the Falcon 5 and Falcon 9 second stage tanks
are going to be aluminum.

- Ed Kyle