Dave,
Tripoli has given a provisional approval for steel nozzles on 'sugar'
propellant only for this year at research launches and with the ok of the
launch prefect. It is to determine if steel nozzle use will be allowed in the
future. They want data for tests and launches...specifically, what happens to
the nozzle in the event of a CATO. How far does it travel from the launch pad,
does it fragment, what impulse motor. Nozzle is to be pointed down, not looking
for nozzle up or horizontal tests. So far this year all of my flights and tests
have been nominal so if anyone has CATO data with steel nozzles on sugar
rockets PLEASE submit before the end of the year,
Rick
On Thursday, March 8, 2018, 09:00:14 PM PST, David Snyder
<dvdsnyd@xxxxxxxxx> wrote:
Richard,Again, Thank you for your thoughtful and thorough response. I hadn't
thought of using a steel nozzle. Will have to see if that is viable within
Tripoli. It definitely has it's advantages though.
The way you explain the analysis for needing or not needing to take into
consideration 2-phase flow makes sense to me, and has really helped me grasp
further understanding of 2-phase flow!Thank you!Dave
On Wed, Mar 7, 2018 at 12:08 PM, Richard Nakka <richard.rocketry@xxxxxxxxx>
wrote:
Dave,
Interesting formulation. Quite cool burning, even cooler burning than sugar
propellants, which means you can use a steel nozzle, nice.
You ask a good question as to whether you'll have to consider 2-phase flow.
Approximately 9% of the exhaust mass is condensed phase consisting mostly of
Carbon with some Ferrous oxide, this explains the black smoke. However, in the
chamber you have all gaseous products. As the combustion products flow through
the nozzle, the temperature drops and the condensed phase products form. This
is different than with sugar propellants, where the condensed phase products
form in the combustion chamber. So your case is a little trickier to analyze.
I would expect that two phase flow need not be considered since the particles
would form after the products have passed the nozzle throat. At that point the
particles would be travelling at the same velocity as the gases (that they form
from).
Richard
On Tue, Mar 6, 2018 at 9:57 PM, David Snyder <dvdsnyd@xxxxxxxxx> wrote:
Hi Richard,Thank you for getting back to me.I had thought that the answer could
likely be as simple as you pointed out.
A further inquiry:I am working on a HTPB based propellant where I am trying to
run through the theoretical values as done in the technical notepads on Nakka's
site. The formulation is called "Pitch Black" It is a fairly low Isp composite
propellant that is easy to make and produces a dense black smoke.I have to
believe that 2 phase flow would have to be a factor with this propellant due to
the thick smoke it produces.However, when running Guipep, there are no
condensed combustion products. However, in the exhaust flow results, there are
a couple products that are condensed.Does anyone have any insight on how to
treat the theoretical calculations with this propellant. I understand it is not
a sugar motor, but I appreciate any insight and guidance you could provide.I've
included an attachment a sample guipep run.
Again, Thank you all for your help!Dave
On Mon, Mar 5, 2018 at 12:35 PM, Richard Nakka <richard.rocketry@xxxxxxxxx>
wrote:
Dave,Glad to hear about your interest in the science of rocket propellants.Good
question you asked, straightforward answer. H3, KCN, CHF, CH2O, etc were left
out of the calculation because these are present in such tiny quanities. If one
took the extra effort to include these, you'd find that the final values for
isentropic exponent, etc, would be unchanged. Good exercise to try perhaps :-)
Richard
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On Sat, Mar 3, 2018 at 1:52 PM, David Snyder <dvdsnyd@xxxxxxxxx> wrote:
Hi Everyone,I've been lurking for a while. There have been some very
interesting discussions so far. A little background on me - I have worked on
Sugar based propellants in the past, mostly KN-Sorbital, and KN-Erythritol. My
father and I have successfully flown a J powered KNER rocket to over a mile at
our peak in sugar propellant. Our success wouldn't have been possible without
help derived from sites by Jimmy Yawn, Richard Nakka and Scott Fintel. Thank
you!
Now, We are looking at getting into composite propellant, but I am trying to
learn more about Guipep and the science behind propellant development and
formulation. For this, I am going back to sugar, since so much of the
theoretical side is documented by Nakka. I am trying to replicate some of the
theoretical calculations he has done.
So, I began going through the technical notepads on Nakka's site.Specifically
the KNSU notepad:http://www.nakka-rocketry.net/ techs.html
I understand the math behind most of it, and was able to very closely replicate
the numbers he came up with, but I am having trouble identifying why certain
combustion products were left out in some of the calculations.
Specifically in note 2:Nearly all of the combustion products from the Guipep
run are listed in the first table where the total moles, gas moles and
condensed moles are calculated.
However, I'm unsure of why some of the products are left out, notably I'm
unsure of why NH3, KCN, CHF, CH2O, and CNH were left out, but OH was left in.OH
has a smaller mole fraction than NH3 and others as far as I can tell when
evaluating the complete list in excel.
Again, in the second table where the isentropic exponent for 2 phase flow and
others is calculated, I'm unsure of how the final list is derived. Further
combustion products are left out in this list. Such as OH, KH, H, K and others.
Guipep also provides an exhaust products results. However, one of the
underlying assumptions is that chemical equilibrium is established in the
combustion chamber, and does not shift through the nozzle. Although, upon
inspection. The products in these results to not follow with that of the table
used to calculate the isentropic exponent either.
I can only assume that there is a reason for these decisions, but don't have
enough hand's on/gut-check style of knowledge to figure out why yet. Before
asking about some other questions I have, I'd like to gain some insight on this
if possible Would anyone be able to help shed some light on why various
combustion products were left out in each of the calculations?
Thank you for all of your help,Dave
