Henry:
The X-37 thrusters used a Pt/Pd alloy wire that was custom woven to a fine
mesh--these thrusters were much smaller than my hand (1 lbf., as I
recall)--the mesh was then punched to make the individual pieces that
stacked to make the cat bed.
That was all there was to it; 98% Peroxide is too hot for silver but has no
effect on Pt/Pd alloy. Cost--for an about .75" by 2" cat bed--was north of $5k
each after all the scrap was sold back. A *lot* of care was taken to
recover the scrap....
Bill
On Friday, September 16, 2016, Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
wrote:
As I read the earlier post, the failure was not in the platinum/palladium
coating but in the underlying ceramic beads. Automotive cat converters heat
up and cool down relatively gradually so surviving extreme thermal shock
probably isn't a design requirement for the catalyst's ceramic substrate.
(Extreme parsimony with the actual catalyst metals definitely is a design
requirement.)
Just out of curiosity, anyone have a source and price on pure
platinum/palladium mesh or wire? On plated mesh or wire? It occurs to me
that it might be overall cheaper to bite the bullet and pay, say, $10K per
engine, than to put more time and effort into finding a cheap alternative
for HTP cat-packs when that's already soaked up so much time and effort to
no avail.
Henry
On 9/16/2016 5:14 AM, William Claybaugh wrote:
Randall:
Very clever, raiding catalytic converters. I'll look into exactly what
the car companies use; pure platinum / palladium should not have failed
at peroxide temps....
Just curious and OT, but could you see more than a bright dot? Wings?
Bill
On Friday, September 16, 2016, Randall Clague <rclague@xxxxxxxxx
<mailto:rclague@xxxxxxxxx>> wrote:
Hi Bill,
Not hardly; these were platinum/palladium beads scavenged from a
catalytic converter at a junkyard. Considering the difference in
mass flow between what they were designed to handle and what ERPS
asked of them, it's no wonder they were pulverized. It's a tribute
to automotive engineering that they worked for as long as they did
under those conditions.
I didn't know that about X-37, thanks. I did see one in flight.
10x50s from a Burbank back yard. 22 Dec 11, so that would have been
OTV-2.
-R
On Thu, Sep 15, 2016 at 1:33 PM, William Claybaugh
<wclaybaugh2@xxxxxxxxx
<javascript:_e(%7B%7D,'cvml','wclaybaugh2@xxxxxxxxx');>> wrote:
Randall:
I deduce from your discription that the Platimium / Palladium
was deposited on some sort of matrix and that the coating came
off under differential thermal expansion; yes?
The 98% peroxide thrusters developed--but not used--for X-37
used woven screens in more or less the conventional manner used
for silver. They worked w/o incident in testing.
Bill
On Thursday, September 15, 2016, Randall Clague
<rclague@xxxxxxxxx
<javascript:_e(%7B%7D,'cvml','rclague@xxxxxxxxx');>> wrote:
ERPS tested platinum/palladium beads in 1994. The beads
work fine in an ashtray, as ERPS demonstrated during their
talks at Space Access '94 and '95. (In '95 they scorched
the tablecloth, and they were asked not to repeat their
demonstration.)
Video of a test ERPS did with a platinum/palladium bead
catalyst pack shows that the exhaust starts out white, goes
clear, then turns tan. Post-test inspection showed that
many beads were crushed or absent. The tan exhaust was
interpreted as pulverized catalyst departing the engine, and
their hypothesis was that the beads lost structural
integrity due to thermal shock.
-R
On Wed, Aug 24, 2016 at 11:46 PM, William Claybaugh
<wclaybaugh2@xxxxxxxxx> wrote:
I'm pretty sure that Platinum / Palladium cat beds are
proven to work just fine and last forever running 98%
Peroxide.
Bill
