Richard, in thinking about that first surfactant experience, that was true. The
super fine KNO3 (powder) mixture was like mash potatoes and didn't become
pourable no matter what temperature. I wonder what is going on with the KNO3
particle size/temperature/viscosity graph.
I live in a desert with humidity generally 5-20%, I never use desiccant and
don't bag my propellant grains and they stay dry for a long time (some at FAR
are 1 year old). And occasionally, get busy with other things and will leave
the KNSB in the skillet for hours at 220F so I'm sure most of the water is gone
but it remains pourable. I will have to try oven pre-drying the KNO3 before
mixing and melting to see if that increases the viscosity of granular melt with
increasing temperature.
What are the specs of your M-impulse motor? Mine are usually 5-7 grains and
will lift a 6" rocket to about 10,000' and a 4" rocket to around 15,000'. It
took a large UCLA 7.5" rocket to almost 5,000' last month testing their new
recovery system for their new larger liquid rocket. The main failed to come out
of the deployment bag on the first flight but the second flight was nominal
after addressing the issue. For the safety of rockets using my 'testing motors'
I keep the Kn low, ~300 On Friday, March 29, 2024 at 08:44:45 AM PDT,
Richard Nakka <richard.rocketry@xxxxxxxxx> wrote:
Now I have to disagree with you, Rick, a qualified disagreement. For my new
M-motor, I ground the KN very fine. The heated slurry was viscous, but nearly
pourable at 120C. So I heated it to 130-135C thinking it would get more fluid -
no, the opposite, it became even more viscous. This was the case with all 11
grains I cast for that project.Possible explanations for our discrepant
observations:1) my KN is very fine, yours is granular2) my products are quite
dry to start with, heating drives out what little moisture is present (residual
water is known to make a slurry more fluid)R.
On Fri, Mar 29, 2024 at 10:36 AM Rick Maschek <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
Richard, I've seen that video using surfactants a few times and this time I
converted the 119 C you begin with (unpourable) and the 130 C with surfactant
that you do the pour. 119 C = 245 F and 130 C = 266 F. The hotter the KNSB the
less viscous it is. I'm not denying surfactants don't work; I remember years
ago when we had a batch of KNO3 that was super powdery and the melt was like
mash potatoes and we tried Scott Jolley's surfactant method.
surfactant
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surfactant
Surfactants
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It made the otherwise unpourable pourable.
I don't grind my KNO3 super fine and in motors 4" and above, I don't grind any
and am able to pour my KNSB at 220 F ( 105 C ). When you are making KNSB motors
with 70 to 650 pounds of propellant, grinding the KNO3 to a powder isn't an
option.
Rick
On Friday, March 29, 2024 at 08:16:35 AM PDT, Richard Nakka
<richard.rocketry@xxxxxxxxx> wrote:
Sodium Laureth Sulfate works very well.
https://www.nakka-rocketry.net/sorb.html#Casting
Have you seen my video?https://www.youtube.com/watch?v=hcUBmzIBSjc
R
On Fri, Mar 29, 2024 at 10:11 AM Tr Mu <tl01001101@xxxxxxxxx> wrote:
What surfactants would you recommend? I'm adding Bi2O3, Mg, & Ferrocene and so
anything I add needs to be compatible with everything at casting temps. I'd
still test it by heating to +100°F over casting temp. But currently my sorbitol
is plenty liquid at temp and so I do not see a reason to add a surfactant.
Trevor
On Fri, Mar 29, 2024, 11:06 AM Richard Nakka <richard.rocketry@xxxxxxxxx> wrote:
Adding surfactant to KNSB or KNDX reduces the viscosity of the slurry to make
it easily pourable. If only a tiny amount is added (0.1% or so) performance is
not affected.R.
On Fri, Mar 29, 2024 at 8:42 AM Tr Mu <tl01001101@xxxxxxxxx> wrote:
My main reason for not wanting to go to dextrose is the viscosity. Sorbitol is
quite thin and thus I can load it up pretty high with KNO3, Mg, & other things.
My current formula for a fast propellant is only 30% sorbitol and still can
pour easily into my 29mm casting setup (with coring rod already in place).
Paraffin was a thought because it is even thinner when melted and I was hoping
it would allow me to go higher on the KNO3 percentage. This is why I started up
in the 80%s. Mainly I'm looking for things that are different to do. Eventually
I'll be able to do APCP and get all of the performance I want, but for now it
is fun to see how much I can get out of cheaper ingredients.
Trevor
On Thu, Mar 28, 2024 at 11:07 PM Lincoln Ross <lr21643@xxxxxxxxx> wrote:
BTW, Trevor, if you're trying to save money, you might consider dextrose. I
think Baker's Authority has it at something like $79 for 50 lbs. As usual,
Richard Nakka has quite a bit of info about using it in fuel grains:
https://www.nakka-rocketry.net/dex.html Note that the hydrated form melts at a ;
low temperature and doesn't give up all that much specific impulse.
On Thu, Mar 28, 2024 at 8:21 PM Lincoln Ross <lr21643@xxxxxxxxx> wrote:
There is also something called Gulfwax, commonly found at supermarkets. I think
mine might be from the previous millennium, though. Unless there was some kind
of aging over that time, I bet it is about the same stuff. In bulk, of course,
the stuff is cheaper.
On Thu, Mar 28, 2024 at 5:36 AM Tr Mu <tl01001101@xxxxxxxxx> wrote:
I just used some I found at Hobby Lobby. It was labeled as being pure paraffin
for candle making.
Trevor
On Thu, Mar 28, 2024, 12:56 AM Lincoln Ross <lr21643@xxxxxxxxx> wrote:
Any specifics or does the paraffin just end up covered with tiny bite marks? ;-)
On Thu, Mar 28, 2024 at 12:53 AM Bruce Beck <bbeck7@xxxxxxxxx> wrote:
Nitrates are lousy oxidizers for paraffin.AP works well but chuffs at low
pressure.
On Wed, Mar 27, 2024 at 4:16 PM Tr Mu <tl01001101@xxxxxxxxx> wrote:
This past weekend I had the idea of trying a paraffin based propellant. Has
anyone tried this? It melts at a lower temp than sorbitol and based on the
prices I found, it would end up cheaper than my current sorbitol motors.I tried
some small 10 gram batches of 80:20, 85:15, & 90:10 KNO3:paraffin. These were
based around 85:15 being an "ideal" ratio as per ProPep3 None of them would
sustain combustion. I want to try it again this weekend with finer ground KNO3,
but I wanted to see if anyone else has tried it.
Trevor