I've unintentionally burned aluminum in LOX a few times. Foil burns
happily and brilliantly, just as steel wool will burn in air, but
metal with any thickness won't catch (just as steel plate won't burn
in air). On the fire during the NGLLC on Xoie a 1/8" aluminum tube
pressurized with LOX failed due to an external fuel fire. It sprayed
GOX and then LOX on the aluminum foil insulation cover, which burned,
then the Pyrogel insulation, which burned down to bare aluminum tank,
but the tank itself was undamaged. Until it was later turned into a
grill, then stolen. Mojave.
In another 'experiment' a copper part heated above the melting point
of aluminum was pressed up against an aluminum part in the presence of
LOX. Some surface aluminum melted away and added a white streak to the
exhaust, but the aluminum part did not "catch on fire" and only had
superficial damage consistent with melting.
Aluminum lithium may be dramatically more reactive, I haven't tried
burning it. Lithium is obviously more reactive, but aluminum lithium
alloy has a tiny percentage of lithium in it. If it was really
hazardous then you'd think there would be stories from it causing
trouble in all the previous systems it's been used in.
Titanium is definitely more reactive in LOX; if the helium tanks are
COPVs with titanium liners and a liner burned it would contribute
energy quickly. Reportedly, tearing titanium in the presence of LOX is
sufficient to get a reaction rate that is described as an explosion,
but again sadly I haven't had a chance to try it. I'll have to borrow
a cup of LOX off somebody at FAR some time and try to set off a
titanium sheet.
Ben
On Sun, Sep 11, 2016 at 6:56 PM, David Weinshenker <daze39@xxxxxxxxxxxxx> wrote:
On 09/11/2016 03:43 PM, Henry Vanderbilt wrote:
Yes, but... As I understand it, aluminum in LOX very much tends not to
catch fire absent significant heat and/or a mechanical impact or tear
that exposes unoxidized aluminum directly to LOX.
Something fractured (or jammed violently and made fresh scratches /
shavings) in a vent valve handling pressurized GOX?
It looked like the venting plumes of cold vapor changed location
shortly before the burst, in the video I saw (not sure if that's
relevant)...
-dave w
