After watching the video a few more times, you'll see that there are two
booms from the two tanks rupturing. First the lox tank fails because it
fell furthest, passing the hammer test with no chemical reactions. The
kerosene tank actually survives the initial impact but not the explosive
lox tank failure. The ignition source most likely the still burning landing
engine which is burning off residual kerosene.
Speaking of booms, the first landing at ksc had an interesting triple
sonic boom.
On Jan 18, 2016 7:53 PM, "Ian Woollard" <ian.woollard@xxxxxxxxx> wrote:
On 19 January 2016 at 00:54, Troy Prideaux <GEORDI@xxxxxxxxxxxxxxxx>
wrote:
Re bare Aluminium: It should be noted however that aggressive oxidation of
exposed material is something to be associated with very reactive grades
of
aluminium (eg: pure aluminium) and not the typical structural grade alloys
of aluminium we're all more familiar with. That's not to suggest it's not
possible for an energetic reaction to take place in the presence of pure
oxygen and a high energy fracture or tear, but it's a hazard often
erroneously attributed to all grades of aluminium alloys.
Actually the aluminium lithium alloys that are used in SpaceX's O2 tanks,
fail the hammer test with non zero probability.
In fact I believe it was Feynman that noted that the Space Shuttle flew,
every single time, with a waiver, on the basis that it was unlikely to get
hit by hammers in flight. (For those not in the know, the hammer test is
when you simply whack a tank filled with pure oxygen with a hammer to see
whether it promptly catches fire).
Nevertheless, aluminium lithium alloys O2 tanks are still used because
they're very light and strong and easy to work.
It's quite likely that the SpaceX vehicle essentially just failed a
particularly severe version of this test, but under the circumstances, and
with so many ignition sources, including the still hot engines, this
doubtless would not be considered a bad fault.
Troy
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
On
Behalf Of Henry Spencer
Sent: Tuesday, 19 January 2016 11:06 AM
To: Arocket List <arocket@xxxxxxxxxxxxx>
Subject: [AR] Re: SpaceX barge landing mishap
On Mon, 18 Jan 2016, John Dom wrote:
Burning motor/hot metal ignited the mix in that video. Schnapps and
LOX require an igniter to burn...
The edges of metal that has just split under heavy load can be quite hot
due
to release of strain energy, and the metal itself can be chemically active
due to lack of a protective oxide layer -- bare aluminum in particular is
extremely aggressive. Plus, in any accident involving pieces being thrown
around, there will be transient local high temperatures when things bang
into each other, perhaps going as far as striking sparks (depending on the
materials).
Henry
--
-Ian Woollard
Sent from my Turing machine
