I believe it is relevant to long motor cores of any type ; it relieves
symptoms of erosive burning.
My suspicion is with nozless the taper can be much more gradual than with
stepped bates
As an added bonus, it should make the casting core easier to remove.
On Tue, Jun 25, 2019, 12:59 AM <spas@xxxxxxxxx> wrote:
Why we need increase core toward the end?
Where this knowledge come from? Is it relevant to nozzled motors or to
nozzleless motors?
Serge
Why are we continuing to make longer pure straight cores, when we knowwhere
that
we need to gradually increase the core toward the end ? Just to see
the upper limit is for various propellant flavors?
On Mon, Jun 24, 2019 at 12:17 PM Alex Kuehn <awkpilot@xxxxxxxxx> wrote:
The pressure in these motors is pretty low but the thrust at ignition is
very impressive.
https://youtu.be/fQs2THUi2Cc
That is a 24mm G I made that is nozzleless.
Some of us are working on trying to push the limits of these and see how
much performance we can get without a nozzle.
My typical nozzleless motor has a 1:32 core which if I recall correctly
is
an initial Kn of 129.
I am working with a gentleman from Washington (Richard Miles) to do a
series of tests to see how long we can make a motor but our initial
tests
have shown it gets a lot less straightforward (irregular burning,
errosive
burning, etc) when you try to do a really long one even though the
calculations seem to support doing one's that are longer than what
people
have down so far.
https://youtu.be/ZGpuR5dLRBM
This is a video of a motor test we did that I'd calculated would be a
29mm
H254 using Richard Nakkas propellant data and my excel calculator for
nozzleless motors and we got it to go finally and hold together (the
first
tests at this length ejected chunks of propellant) by lighting it in the
middle rather than the head of the grain but the friction fit grain
wasn't
secure enough and it failed. We're going to continue this testing soon
hopefully but both Richard Miles and myself have issues with humidity
and
propellant where we live so we're both waiting on rain to stop so we can
continue testing.
-Alex
On Mon, Jun 24, 2019, 10:42 AM Shawn McHatten
<shawn.mchatten@xxxxxxxxxxx>
wrote:
I'm wondering if I understand the formulas that are running around on
this thread. With the M19 burn the exit port diameter is approx 20mm or
or
a port area of .62sq inches. And the thrust is approximately 40kg or 88
pounds at the beginning of the burn. Are we saying the pressure at that
point in the burn is 88lbs/.62sqin or about 140psi in the chamber. That
does not seem like a very high pressure at all. Sorry for mix and
matching
units but I wanted to get it to something I understood.
thanks
Shawn
On Sat, Jun 22, 2019 at 2:48 PM <spas@xxxxxxxxx> wrote:
Richard,
There is no pressure on my graphs, I have not measured it. On the axes
of
all my graphs - time in seconds and thrust in kilograms. 50,000 means
50
kg.
Sorry, some links are to AER group, it is only for subscribers.
Here are links on my FB page
https://www.facebook.com/serge.pipko.5/posts/480370956039788
https://www.facebook.com/serge.pipko.5/posts/450824292327788
Serge
Serge, what are the units of pressure, millibars? The video linksseem
brokenthe
Richard
On May 5, 2019 3:33 AM, <spas@xxxxxxxxx> wrote:
I began a series of tests of nozzleless motors of different
configurations
and with different propellants. The purpose of the tests is to find
motorsoptimal configuration that will give the maximum Isp.
I recently tested 4 nozzleless motors with KNSB propellant. All
diameterhave the same size and weight, grain outer diameter 50 mm, core
in19.3 mm, core length 500 mm, propellant mass 1500 g. Motors differ
used
potassium nitrate.
M14 - granulated KNO3 (contains 0.8% SiO2 anticaking agent)
M15 - granulated KNO3 + 0,5% red iron oxide
M16 - pure milled KNO3
M17 - granulated milled KNO3
The following tests will be with a greater core length, with sodium
nitrate as an oxidizing agent and with the addition of aluminum.
Thrust curves of the motors are attached.
Videos of the tests can be seen here
https://www.facebook.com/groups/1396488870646273/
permalink/1993969987564822/
https://www.facebook.com/serge.pipko.5/posts/450824292327788
