Hi Martin,
I use Secondary Ignition Composition (SIC) in all my motors, both candy
and composite.
http://serge77-rocketry.net/igniter/igniter-e.htm
http://serge77-rocketry.net/knsb_ignab/knsb_ignab.htm
http://serge77-rocketry.net/knsb_ignab2/knsb_ignab2.htm
It leads to instantaneous ignition of the motor without the lag between
igniter POP and motor thrust.
Examples:
One-grain KNSB test motor
http://serge77-rocketry.net/alum1/k138-st-54.avi
from the page http://serge77-rocketry.net/alum1/alum1.htm
5-grain KNSB motor
http://serge77-rocketry.net/20031221/101_0140-1.avi
from the page http://serge77-rocketry.net/20031221/20031221.htm
So I recommend you to use SIC-1 or SIC-3 in the form of two or three
parallel strips along the grain core. Length and width of the strips
should be equal to core length and diameter. When using SIC, you don't
need to paint propellant surface with additional pyrogens.
Important note: when using SIC strips in the core, you should put igniter
in the nozzle end of the motor, not in the top of the core, as usual.
Because, if ignited from the top, SIC strips will move to the nozzle and
clog it.
One question: why do you use surfactant with milled KN? You want to
comparison performance of KNSB propellant with milled and coarse KN,
right? But it is methodologically incorrect to add surfactant only to
milled KN, because it greatly influences burn characteristics. It will be
more correct to add surfactant to both milled and coarse KN or not to add
it at all.
Serge Pipko
Kiev, Ukraine
serge77-rocketry.net
Dear people,
For my master thesis I am characterizing both course and fine KNSB
(KNO3-Sorbitol) propellants at various conditions (pressure/ grain initial
temperature) as it is a readily available solid propellant that has not
been characterized overtly much. In addition it would allow me to almost
freely publish my test data/ propellant characteristics and other results
which cannot be said of many commercial solid propellants or when
collaborating with companies.
However during my experiments I have run into considerable issues with the
fine (100 mu average KNO3) propellant, I cant get it to ignite while the
course (350 mu average KNO3) propellant burns alright. I've tried most of
the textbook solutions but currently I am completely out of ideas. I have
the feeling that my current igniter charge burns too fast for the KNSB to
properly start combusting. I'm looking for answers to for instance the
following questions:
- What would be potential physical mechanisms that make the fine KNSB
more difficult to initiate than course KNSB?
- What igniter redesigns could I implement to give it a better chance
of
ignition? (Other compositions/ different geometries/ slower burning
suggestions?) - bonus points for reuse of current hardware and non
space-grade energetic materials such as BKNO3.
I have condensed my thoughts and a summary of the problem in a small Root
Cause Analysis. I sincerely thank any suggestions in the right direction.
kind regards/ vriendelijke groeten,
Martin Christiaan Olde
*MSc student, DARE member*
*Delft University of Technology*
