Yes, both motors were identical except the flight motor had an expansion
cone.
On Thu, Jun 20, 2019 at 1:47 PM <spas@xxxxxxxxx> wrote:
Regarding the addition of an expansion cone, I have tried that on one of
the nozzleless motors that I flew a while ago
Did these motors have equal length of strait core?
(see attached pics). After
test firing a nozzleless motor with a straight core, I decided to add anhttps://www.facebook.com/groups/1396488870646273/permalink/1993969987564822/
expansion cone, and fly the motor in a rocket. Well, the result was
disappointing. The rocket flew a fair amount lower altitude than
predicted.
So it seems that the expansion cone resulted in a loss in thrust. It will
be interesting to see if Serge's upcoming test firing of such a motor is
in
agreement with this finding, or not.
Richard
On Thu, Jun 20, 2019 at 6:07 AM <spas@xxxxxxxxx> wrote:
attached picture
Ray, thank you for your kind words)speed
It is always a pleasure to read of your experiments, Serge.
Do you measure chamber pressure during these tests?
No, but I believe in nozzleless motors pressure may be calculated by
multiplying thrust on exit port area.
From the thrust curves, it does not seem that erosive burning at the
exit
is significantly affecting the grain geometry.
There is interesting paper on this matter: "Internal Ballistics
Considerations of Nozzleless Rocket Motors", Journal of Propulsion and
Power, 1999.
http://serge77-rocketry.net/nozzleless0/nozzleless.pdf
The main idea, confirmed by experiment and calculations: the burning
of propellant is approximately the same along the entire length of thepart
core, because the acceleration of combustion due to erosion near the
nozzle is compensated by the acceleration of combustion in the head
due to a much higher pressure than near the nozzle.is
Also, it is interesting
that the M16 test had a shorter duration than the M19 test.
I have used new coffee grinder for M19, so the most plausible reason
somewhat coarser KNO3. It is unfortunate, because it is impossible nowto
correctly compare these two motors.poured
Have you considered forming an expansion cone in the propellant?
Yes, but not now. Conical insert has long been waiting for its time
(attached).
At first, I want to determine what maximum pressure such an engine can
withstand. So I will try more and more long core. Yesterday I have
motor with core length 700 mm, L/D = 14.wrote:
On Wednesday, June 19, 2019, 2:32:24 PM GMT, <spas@xxxxxxxxx>
(d/D)
now L/D = 12
and I prepare next motors with L/D = 14
I want to know what maximum L/D may be used for maximum Isp
core to diameter ratio (d/D)is about 1/3 in all tests
Very interesting, Serge. Previously you recommended a guideline of
length
to grain diameter ration (L/D) = 10 and a core to diameter ratio
=1/3
based on your earlier testing. What ratios are you using now?
Richard
On Wed, Jun 19, 2019 at 6:46 AM <spas@xxxxxxxxx> wrote:
More tests of nozzleless motors, previous tests are here
https://www.facebook.com/groups/1396488870646273/permalink/2020337984928022/500,
Today's two tests differ by a longer channel, 600 mm instead of
Lengtheningand
a
greater mass of propellant KNSB, 1750 g instead of 1500.
inthe
core leads to an increase in pressure in the motor and an increase
arethe
Isp, so I will increase core length further)
M18 - granulated nitrate
M19 - pure milled nitrate
Thrust curves of the motors with previous results for comparison
attached.
Video is here
https://www.facebook.com/groups/1396488870646273/permalink/1993969987564822/find
Serge Pipko
Kyiv, Ukraine
serge77-rocketry.net
I began a series of tests of nozzleless motors of differentconfigurations
and with different propellants. The purpose of the tests is to
differthe
optimal configuration that will give the maximum Isp.motors
I recently tested 4 nozzleless motors with KNSB propellant. All
have the same size and weight, grain outer diameter 50 mm, corediameter
19.3 mm, core length 500 mm, propellant mass 1500 g. Motors
sodiumin
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
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/serge.pipko.5/posts/450824292327788
Attachment:
NTM-12 mould.pdf
Description: Adobe PDF document
