Even the shuttle tile aerogel material might be sufficient for a
lightweight nozzle attachment. A problem though is the shuttle tiles and
also the Johnson tiles have low compressive strength, only about 1 bar.
But as the exhaust travels down a nozzle towards the exit the pressure
also decreases. So perhaps it could be used as the nozzle extension for the
nozzle below where the exhaust gas falls below 1 bar pressure. This could
result in a significant reduction in weight. See for instance the
comparison size of the RL10 nozzle used on the DC-X optimized for low
altitude flight compared to one for high altitude, near vacuum flight:
This might be hard to test though for amateurs. Amateurs don't have access
to the expensive test equipment used to test engine performance under high
altitude, near vacuum conditions.
To do the test at sea level we would need to make the attachment so that
the length of the nozzle would make the exit pressure to be quite low. This
then entails dangerous loads on the nozzle due to the overexpansion. This
would be made even worse due to the brittle nature of the ceramic.
The most effective test would be on the rockets by university and amateur
teams whose rockets have reached 100K feet. The pressure there is only
about 1% that of sea level.
Bob Clark
On Mon, Jan 1, 2018 at 4:32 PM, Dave Barr <dhbarr@xxxxxxxxx> wrote:
Against my better judgement, I followed the link to find: 3M AF-12,
Cotronics 360m, & Cotronics 901.
I suspect the density and perhaps some of the other characteristics may
be misremembered from 1984.
On Sunday, December 31, 2017, Terry McCreary <tmccreary@xxxxxxxxxxxxxxx>
wrote:
Any idea what the commercially available materials are, and how theJohnson ceramic is made? Inquiring minds want to know!
Another possibility is the ceramic material developed by aerospace engineer
Best,
Terry
On 12/28/2017 2:48 PM, Robert Clark wrote:
Could the famous space shuttle tiles be used for nozzle material?
GW Johnson. A big advantage of the Johnson ceramic is it can be homemade
from commercially available materials, quite useful for the amateur rockets.
applications, Page 6: space shuttle tiles and other ceramics for nozzles.
Altitude compensation attachments for standard rocket engines, and
compensation-attachments-for.htmlhttps://exoscientist.blogspot.com/2017/12/altitude-
Bob Clark
--
Dr. Terry McCreary
Professor of Chemistry
Murray State University
Murray KY 42071
