[SS2S-Main] Re: Sugar Shot Weekly Activity Report -Dec.16-20, 2013

  • From: Richard Nakka <richard.rocketry@xxxxxxxxx>
  • To: sugarshot@xxxxxxxxxxxxx
  • Date: Thu, 2 Jan 2014 12:35:00 -0600

On Wed, Dec 25, 2013 at 5:36 PM, Cliff Bates <cliff@xxxxxxxxxxxxxx> wrote:
>     I kind of wonder about the terrific amount of build up of slag in the
> diversion part of the exhaust nozzle however.  It would appear that in
> flight if this happened it could cause a considerable yawing in the
> trajectory.

I wouldn't be too worried the slag buildup on the nozzle. This buildup
occurs only during the tail-off, when the pressure in the motor is
decaying down to zero. For this motor, the max chamber pressure was
low, and tail-off duration was particularly long,  which explain the
excessive buildup.

>     Also it appeared to me that the exhaust velocity was noticeably lower
> than normal.  But I'm kind of negatively bias on this diffusion plate idea
> anyway.

On Rick's urging, we decided to be particularly conservative with this
2-grain motor test, keeping the Kn low and therefore maximum chamber
pressure was particularly low (max 265 psi). The next two test
firings, 4 and 6 grain respectively, will see proportionally higher
chamber pressures.


>     Cliff
> ----- Original Message -----
> From: Jeppe Locht, Mainstage Co.
> To: sugarshot@xxxxxxxxxxxxx
> Sent: Wednesday, December 25, 2013 1:37 AM
> Subject: [SS2S-Main] Re: Sugar Shot Weekly Activity Report -Dec.16-20, 2013
> And the prize for showing remarkable restraint despite fair reason to go
> ballistic, goes to Rick ;-)
> On Dec 25, 2013 03:52 "Rick Maschek" <rickmaschek@xxxxxxxxxxxxxx> wrote:
> Eric,
> I can appreciate your comment. I could easily have left the four failed
> attempts out of the video and made it look like things went wonderful. I
> know many that try not to show things that don't work.
> This was the first time we did this type of motor. The tops of the grains
> were inhibited with polyester resin and a layer of pyrogen was painted
> across the top and down the two sides of the grain. During motor assembly,
> the floating nozzle slid forward and cracked the igniter's bridge wire, this
> was discovered after the first attempt and inspection of the igniter. On the
> second attempt with a new igniter, continuity was lost. On the third
> attempt, the igniter was not of sufficient intensity to ignite the pyrogen
> painted on the top surface. On the fourth attempt, a larger igniter was used
> and managed to burn the pyrogen painted on the top inbitited surface (seen
> in the 4th picture of the video) but failed to continue to burn down the
> sides of the grain. On the fifth attempt, a 0.125 thick slice of APCP
> propellant was cut from a 38mm grain and the igniter place in its center.
> That ignited the motor. This small K-class motor was to test this very
> thing, how to ignite these grains, would the sliver catcher work, and would
> this grain geometry burn as predicted. We were successful with these three
> things. A new bulkhead and igniter design has already been machined that
> should solve this problem.
> If you look at our many previous videos of motor tests, you will see we have
> nearly 100% ignition on the first attempt. Thank you for your comments.
> Rick
> From: Eric Christy <sliderulelover@xxxxxxxxxxx>
> To: "sugarshot@xxxxxxxxxxxxx" <sugarshot@xxxxxxxxxxxxx>
> Sent: Tuesday, December 24, 2013 6:02 PM
> Subject: [SS2S-Main] Re: Sugar Shot Weekly Activity Report - Dec.16-20, 2013
> You guys are EMBARASSING! Either you're lousy chemists, not able to get your
> mixture correct, or you're lousy electronics engineers, not able to make
> decent continuity between control board and igniter, or you're both. Which
> is it??? Suffice it to say, you bozos are very UNimpressive! When you grow
> some decent science, then get back to me. I bet you can't even balance the
> chemical reaction between Potassium Nitrate and Sorbital (sugar). You need
> to get that part right first before you try connecting to the igniter.
> Eric
>> Date: Mon, 23 Dec 2013 22:25:28 -0600
>> Subject: [SS2S-Main] Sugar Shot Weekly Activity Report - Dec.16-20, 2013
>> From: richard.rocketry@xxxxxxxxx
>> To: sugarshot@xxxxxxxxxxxxx
>> Highlights of recent developments on the DoubleSShot project
>> ---------------------------------------------------------------------------------------
>> -As planned, Rick Maschek test fired the 89mm (3.5”) 2-grain rocket
>> motor with DD-slot grains on Saturday Dec.21st. The test firing was
>> conducted at the FAR site, with the motor mounted nozzle down on one
>> of the vertical test stands. The base of the stand was fitted with a
>> blast deflector to help prevent smoke from obscuring the pressure
>> gauge used to record chamber pressure. This worked well, and good
>> pressure readings were recorded over the full duration of the burn,
>> which was nominal. Maximum chamber pressure was about 260 psi
>> (1.9Mpa), which compares well with the predicted pressure of 248 psi.
>> Due to problems with the igniter, the planned firings of the 4-grain
>> and 6-grain motor had to be postponed. Rick will be modifying the
>> forward bulkhead with an igniter fitting to prevent a similar igniter
>> issue from re-occurring.
>> Rick and Richard Dierking setting up the motor:
>> http://sugarshot.org/downloads/setup.jpg
>> Richard Dierking connecting the pressure gauge:
>> http://sugarshot.org/downloads/setup1.jpg
>> Motor at full thrust:
>> http://sugarshot.org/downloads/thrusting.jpg
>> Gauge reading at full thrust:
>> http://sugarshot.org/downloads/gaugereading.jpg
>> DD-slot grain details:
>> http://sugarshot.org/downloads/dd_grain.pdf
>> Video:
>> http://www.youtube.com/watch?v=h1mYHtsD7a8&feature=youtu.be
>> (video courtesy Rick Maschek)
>> -Richard has made further progress on fabricating the carbon composite
>> nozzle exhaust cone for the VIC-2 motor. All 10 plies of carbon
>> prepreg were wrapped around the mandrel. After each ply was laid,
>> heat-shrink tape was wrapped around the prepreg, then shrunk using a
>> heat gun to consolidate the layers. The product was then vacuum bagged
>> in preparation for curing. Curing will be done in an autoclave at
>> elevated temperature (300F/150C) and pressure (4 bar).
>> --------------------------
>> -Sugar Shot to Space is on facebook. Check us out.
>> http://tinyurl.com/2exr92k

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