Ed:
I use YSZ on the metal shell of solid rocket nozzles. Typically 310
stainless with 0.015” YSZ plasma sprayed on all ID surfaces and the
graphite throat insert bonded to the YSZ layer; the length of the insert as
appropriate to avoid overheating the steel.
This works fine on 3-4 second burns with a 5400 degree F propellant
formulation and for nozzles in the 0.75 to 1.00 inch throat diameter range.
The YSZ layer goes to 0.060” for a 1.5” throat and 8 second burn.
I’m looking for a simple (read low or no cost) software solution to allow
heat transfer calculations for graphite-YSZ-stainless and YSZ-stainless so
I can correctly size the YSZ layer for larger nozzles but in the meantime
have an Excel model for 1d estimation. How are you estimating internal
heating?
Cost seems to me very reasonable, a few hundred dollars at a industrial
spraying company for a half dozen nozzles. Aerospace quality sprayers
charge s good deal more for no immediately evident benefit.
I’m looking into trying a 70/30 mix of Tantalum Carbide and Hafnium Carbide
that had been shown to handle 6000 degrees F (melting point is around 7200
degrees F) but that will have to wait until I get the current hardware
flown.
Bill
On Sat, Aug 17, 2019 at 1:28 PM Ed LeBouthillier <codemonky@xxxxxxxxxxxxx>
wrote:
On Sat, 2019-08-17 at 16:33 +0000, Ray Rocket wrote:
I did this at a college lab, but have the equipment and could
potentially set up a CVD sputtering process at home.
At the very least, a rotary vane backing-roughing pump will be
required. A small but decent one is around a hundred bucks at Harbor
Freight. I have done silver and carbon sputtering on small samples
using similar pump. For aluminum mirrors (12" dia), I additionally
used a diffusion pump. You could potentially do this in an inert
atmosphere instead.
Sputting and CVD are important processes. Ultramet grows chambers using
CVD. However, I think that it is a bit more onerous process than
electroforming. Especially for amatuer/hobbyist support, I think. My
understanding is that it requires a vacuum, induction heating and flow
of some onerous gases.
I do not know if a diamond chamber would work, but suspect it might
be fine for smallish thrusters.
Charles Pooley wanted to experiment with small engines made with quartz
tubing. I have no idea if it would've worked or not.
Diamond could be incorporated into any electroplate process if the
particles are small and the solution is continuously agitated,
similar to a Nikasil coating process. Alternatively, silicates,
nitides, carbides or other solids can be incorporated, where they can
modify bulk hardness, surface oxidization, wear surfaces, thermal
conductivity and tensile strength.
I'm currently exploring the use of TBC (Thermal Barrier Coatings) for
small rocket engines. YSZ (Yttrium Stabilized Zirconia) seems like the
favored one for rocket applications (with an appropriate application
process). I spoke with one owner of a company that specializes in TBC's
and it seems like it could be done at a reasonable price. The idea is
that something like YSZ can lower the heat flux conducted to the engine
substantially. So, the process I'm exploring is copper electroformed
chamber, coated with YSZ internally. Done in small batches, it might be
affordable/feasible. The reason for the coating is that unmodified heat
fluxes in small engines can overwhelm the coolant capacity of the
propellants and require substantial film cooling. As the engines get
larger, the heat flux becomes more manageable vis-a-vis the available
coolant.
