[SS2S-Main] Re: Rocket help request

  • From: "James Jason Wentworth" <blackshire@xxxxxxxxxx>
  • To: <sugarshot@xxxxxxxxxxxxx>
  • Date: Thu, 2 Jan 2014 18:21:51 -0900

Hello Ben,

Thank you for posting this tip! Tracking smoke is both useful and desirable for model jet flyers as well as for model rocketeers; as well as facilitating tracking of the models, smoke trails provide greater scale realism for scale jets and scale rockets alike. The availability of silicone oil also wouldn't present any handicaps to home production of Rapier-type jet motors. I'm hoping that Dr. Z can arrange to again export his Rapier jet motors to the USA and Canada, but if he can't for any reason, a standardized user-produceable jet motor is a workable "Plan B."

-- Jason

----- Original Message ----- From: "Ben Brockert" <wikkit@xxxxxxxxx>
To: <sugarshot@xxxxxxxxxxxxx>
Sent: Thursday, January 02, 2014 9:12 AM
Subject: [SS2S-Main] Re: Rocket help request


Glad to hear from you, Jimmy, it's always interesting to see your projects.

If you do another experiment on this, try adding a small amount of
silicone oil to the propellant; between one drop per kg and 1% by
mass. When burned inside the engine it turns into incredibly fine
silicon dioxide dust that coats the surfaces of the nozzle. The slag
then isn't able to stick, and won't build up; there's been papers
about using it in APCP rockets to reduce aluminum oxide slag on the
nozzle.

It's available from most drugstores in small bottles, intended for
other purposes related to its slipperiness. You can also get it in
gallon jugs from a variety of industrial suppliers because it's used
as an inert liquid for heated baths.

Keeping with one of the themes of sugar rockets, both the oil and the
silicon dioxide are nontoxic. You don't want to inject the oil under
your skin, but it's safe to eat.

Ben


On Thu, Jan 2, 2014 at 10:44 AM, James Yawn <jyawn@xxxxxxxx> wrote:
I just sent a "wake up" message to the SugPro list, and have not seen it
back in my in-box.  But I did not get a bounce either, not yet.  I would
love to see that list come back, and it would certainly be an appropriate
forum for this discussion.

I did a little experimenting with sugar-propelled Rapier clones a few years ago, and got them to work... more or less. I did not pursue it to the point of making practical motors. Challenges were that burn time was too short
(less than 10 seconds, as I recall) and thrust too strong - several times
what a Rapier would produce.
Another problem is that the combustion of KNO3 with any form of sugar
produces a lot of potassium carbonate. In high-pressure motors this product
is blown out the nozzle at high velocity and thus atomized into that fine
white smoke we all love. Or hate, because in low-pressure motors, it often collects into globs, which are blown out the nozzle in spurts. Hot spurts.
Really hot spurts if they hit your skin.  This might be a problem for
someone wishing to hand-launch their models.  Appropriate protective gear
might mitigate this problem.
Leading me to wonder if an ammonium perchlorate propellant could be induced to burn slowly enough to serve this purpose? It could be formulated so that all products of combustion are gaseous, much like the nitroguanadine used in Jetex motors. But I have only made AP propellant a couple of times, so will
defer this idea to those who have more experience.
Oh, I found my page on those experiments:

http://www.jamesyawn.net/endburner/

I hope to see the SugPro list return. I miss those conversations, and the marvelous resource of it's aggregate intelligence. If I can help with that,
please let me know!

Jimmy Yawn
jyawn@xxxxxxxx
www.jamesyawn.net






James Jason Wentworth wrote:

Hello Peter,

Thank you for replying to my query.  Unfortunately, I know nothing about
the SugPro list. However, the simulation you described below sounds like just the motor we Jetex/Rapier modelers could use! At the very least, it could serve as a baseline design "point of departure" that we could start
with to develop such motors.  That will be quite helpful--Thank You very
much!

-- Jason

----- Original Message ----- From: "Peter Johansson"
<rockets4kids@xxxxxxxxx>
To: <sugarshot@xxxxxxxxxxxxx>
Sent: Wednesday, January 01, 2014 9:22 AM
Subject: [SS2S-Main] Re: Rocket help request


On Wed, Jan 1, 2014 at 3:57 AM, James Jason Wentworth
<blackshire@xxxxxxxxxx> wrote:

Yesterday and today I have received numerous messages on the SS2S e-mail list. I was wondering if anyone here could offer suggestions to solve a
problem:


Before we get to that, Is there any news on the migration of the
SugPro list to the new mail server?  That list would be far more
appropriate for this discussion than ss-main.

something similar to this but optimized for model jet use (an end-burner producing 1/10 of a newton or so of thrust, for 10 - 20 seconds or more) would enable Jetex and Rapier flyers in the western hemisphere to enjoy
our
hobby with no worries about being unable to obtain jet motors for our
models.  Could anyone here suggest propellant formulas for such
low-thrust,
long-burning jet motors?


Sugar propellants are generally not suitable for end burners because
it is difficult to get the burn rate fast enough for them to generate
sufficient thrust -- at least for rocketry applications.

However, I just attempted some simulations based on your requirements
and it does seem theoretically possible to hit that ballpark.  A 5mm
diameter grain (about the smallest you want to work with) will produce
about 3/10 N, and 40mm length will provide a 5.4 second burn time.
Total impulse is 1.68 Ns, 42% A.

-p.



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