We tested the catalyst we normally use for Tridyne with H2O2 once. The
catalyst bed consisted of 2mm Al2O3 pellets with a very high internal
surface of 200m^2 per gram. The pellets were coated with a mix of
platinum and other precious metals. The pellets were very active but
fell apart after seconds. I don't think this was because of the thermal
stress. The problem was IMO that the H2O2 entered the porous pellets as
a liquid and the decomposed H2O2 (so, the hot H2O steam and O2) cracked
the ceramics because of the much higher specific volume which tried to
expand inside the pellets.
Bruno
"At that time [1909] the chief engineer was almost always the chief test pilot
as well. That had the fortunate result of eliminating poor engineering early in
aviation" (Igor Sikorsky)
--
Bruno Berger
Swiss Propulsion Laboratory
E-Mail: bruno.berger@xxxxxx (HTML-Mails will be dropped!)
PGP: http://www.spl.ch/contact/Bruno.Berger.asc
WWW: http://www.spl.ch
HAM: HB9RSU
Am 16.09.2016 um 16:18 schrieb Henry Vanderbilt:
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
