It may, and I will probably do that. I need to figure out how to measure
the temperature the case gets to, but meanwhile I can fly steel motors* as
long as they're no hotter than what I've tried so far. It would be nice if
I could end up burning more of the fuel and having less gunk, though.
*They have spring relief that opens things up and are extremely unlikely to
CATO.
On Sun, Mar 31, 2024 at 8:19 AM DH Barr <dhbarr@xxxxxxxxx> wrote:
Does a simpler candy mix running fuel rich not achieve the temperature
reduction you're after?
On Sun, Mar 31, 2024, 3:37 AM Lincoln Ross <lr21643@xxxxxxxxx> wrote:
I gathered the crumbs from yesterday's attempt and pressed them a bit
harder this time, which kept them together better. Results were much the
same as yesterday, though. Maybe 6 or 7 seconds of slow burning, consuming
only part of the grain, and then it went out. I took out the rest of the
pellet and lit it with a red hot nail. It smoldered a while, then started
burning a bit more vigorously, then went out. Left behind was a mostly
hollow toadstool shape almost exactly the same color as the original grain.
Even a propane torch wouldn't get it going again.
Incidentally, my torch has developed a habit of leaking propane around
the stem of the adjustment valve. This catches fire and I have to blow it
out before I can turn off the torch. Probably time to retire it. I have
another one someplace, though.
I could try reducing the amount of paraffin, but I'm not optimistic.
Maybe I'll go back to sugar and epoxy. With the reduced paraffin, I'd need
some other binder or to make the 2.5 ton press I was thinking about.
On Sat, Mar 30, 2024 at 6:20 AM Lincoln Ross <lr21643@xxxxxxxxx> wrote:
I just tried some fuel with paraffin in it. The mix was, roughly, KNO3
60 percent, sucrose 16 percent, paraffin wax 16 percent, sulfur 4 percent,
red iron oxide 4 percent, and a tiny bit of homemade lamp black. It was a
small batch, though, so probably not terribly accurate. The KNO3 and red
iron oxide were milled together for a while and the resulting particles
were quite fine. I also milled the sugar until it was very fine, and I
milled everything but the paraffin together for a while. The goal was fuel
that was moderately slow to use in a Jetex engine that I have, at a
somewhat lower temperature than straight rocket candy would be at. I heated
up the fuel and mixed it with paraffin, but the fuel seemed awfully dry
after I added it, and, despite mixing for a few minutes, I'm not sure I got
the paraffin evenly distributed. I pressed it into molds, but after cooling
it was still a little crumbly. I managed to get a fuel pellet sized chunk
out of it. I managed to ignite it inside the Jetex motor, but it
only smoked for a couple of seconds, perhaps because the current was
interrupted for a moment. I applied power again and it burned for maybe 5
or 6 seconds, even producing a reasonably fast looking, but small exhaust
stream. Maybe not enough for useful thrust. Then it went out. On opening it
up, very little of the pellet had burned, and it was clogging up the screen
that Jetex motors have to prevent clogged nozzles. Later, I tried lighting
up the material clogging the screen, but it didn't burn much, even when red
hot. I think it did, in fact, clog the screen pretty well, because a bit of
smoke vented out where it shouldn't have halfway through the burn. The case
is held closed with a spring, and I suspect it allowed the case to open
just a bit. . What's odd is that the unburned portion of the pellet, once I
got it lit, burned fairly vigorously in open air.
On Sat, Mar 30, 2024 at 1:44 AM Rick Maschek <
dmarc-noreply@xxxxxxxxxxxxx> wrote:
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 granular
2) 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 <http://www.ajolleyplace.com/surfactant.html>
surfactant
Surfactants
<http://www.ajolleyplace.com/surfactant.html>
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
