DoublSShot Boiler Plate Static sugar motor Test Sept 10, 2011 video cams 1 & 5

[LIONMAN11111]

Why you are using a star grain geometry and not simply a core grain geometry ? the thrust curve profile are very similar to each other, but the star grain geometry is much more difficult to made...

Also have you ever though the possibility of the negative erosive burning ?

[mojaverockets]

@LIONMAN11111 We will be using a light weight composite motor casing for the flight and the 'Bates' core grain heat from between the grains weakens the casing. By using a full length neutral burning STAR core in a long single grain we eliminate those places.

[donperry1]

I know you guy's are pro-amateurs but here are my thoughts.

I'm wondering if the casing swelled under pressure, separating the grain inhibitors in the process, creating more burn surface area.

I'm guessing you are running the KN ratios at the limit :D

Hope you find the cause of the "anomaly"

[mojaverockets]

@donperry1 That would be a very good possibility if we case bonded the propellant. We actually cast it in casting tubes that 'free float' in the casing allowing the combustion gases to pressurize both the inside and outside of the propellant to eliminate swelling/cracking/separating of the propellant. Thanks for the thought.

[david1513]

wait a minute your fuel over pressure rised the chamber pressure to fasti just noticed that it build pressure far to fast if your useing iron oxide use less if not and its AP use a silcone binder instead of epoxy, if its a suger rocket dont use iron oxide thats only for small rockets that need that little extra boost because of the size of the motor being so small,

[mojaverockets]

@david1513 We don't use iron oxide, just KNO3 and Sorbitol as propellant. And it actually built up pressure 'slower' than our other successful motors. Thanks for the thought.

[david1513]

@mojaverockets i hear Sorbitol is a artifical sweetner like sweet 'n' low is this right? i bought some sweet and low used it it dident seem to have much power and no flame just lots of smoke, burn rate was very slow, my confection sugar seems to work best from domino's sugar, its pure cain sugar this was my dads idea and he hates rocket by the way im not young im 62 years old been doing this ever since i was 7 years old thats why my dad hates it lol,, ive boreded him to death with this shit

[mojaverockets]

@david1513 Sorbitol

Sorbitol is a sugar alcohol found in nature (in plant foods such as fruits and berries) and is also commercially made for use as sweeteners.

Sweet 'N' Low is the brand name for the artificial sweetener made from saccharin. It is made from an organic molecule out of petroleum.

They are not the same. Sorbitol is similar to sugar, Sweet 'N' Low is not though it is sweet in taste. We use sorbitol because the melting temperature is less than that of sugar.

[david1513]

@mojaverockets i have another question why heat the mix to desolve it why not use denatured alchol to desolve the mix it will evaperate very quickley and it will burn..! if its not compleatley dry you could still burn it ..!it's used as a lamp or stove fuel, it has no oils in it when it dry no resadue is left behind, i just wonder if anybody has tryed it i just got this idea three days ago,

[mojaverockets]

@david1513  It has been tried. When it evaporates the density of the propellant is lower.

[david1513]

@mojaverockets ok is that good or bad sounds bad?

[mojaverockets]

@david1513 Lower density means less propellant in the rocket and if there was a lot of alcohol that evaporates it could cause many voids that would cause the propellant to burn faster and maybe lead to overpressurization and you see the results in our video of what overpressurization can lead to.

[david1513]

@mojaverockets can i ask you another guestion? what size core burn are you useing, give me inches if you can ok? i beleave your caseing is ok, your core might be to large building pressure far to fast. plus the longer the motor and core the more power it develops the biger the core the faster the pressure, fat rocket motors have less power then a long motor has, fat motors only give more run time,

[seleneteam]

@david1513 Sorbitol dissolves in pure methanol above 50 degrees very good, but try to dissolve the according amount of KNO3 in methanol!!

[david1513]

@seleneteam i grind my kno3 fine like face powder with a blinder not a coffee grinder like most do, when i cook it it always desolves frist then my confection sugar desolves next, i use only domenos pure cain sugar ive only had two catos in 55 years, im 62 now, the two cato's was caused by a bad cardboard linner, wrong cardboard used for linner...!

[david1513]

ok flame retardent is make with warm water and put 7 oz of borax in twoQT's warm water,, then add 3 oz of boric acid put in spary bottle and spray the card board tube till its very wet let dry now the flames wont bother the linner

[david1513]

ok it looked like the tube ruptured mid ways down the tube this can be caused by no linner in the tube the tube was super heated and let lose it power, the tube over heated use a card board liner for that size rocket motor it will have to be 1/4 inch thick, your tube seemed to be PVC, PVC will not work on this size rocket it must be T-6 aluminum this will be costley, ill tell you how to make flame retarent for the card board tube ill put it on the next post ok,

[mojaverockets]

@david1513 The motor casing was steel, the propellant tubes were cast of material similar to the Apollo space capsule heat shield. But thanks for the suggestion.

[david1513]

@mojaverockets ok i got the answer you cant use steel with a seam in it it must be solid like spun T-6 aluminum for the outer caseing ,most steel tubes have a seam down the side ive tryed this it wont work it will slit open every time, your nozzel seems to work great you might try makeing the hole a bit biger your fuel is working great no problum there

[Barnekkid]

A minor setback for Richard and the boys, I'm sure. GO SS2S!!

[seleneteam]

@Barnekkid You say it. We'll strike back

[benmerkenhof]

o2 mixture not right? maybe a buble in the propellant. Do you agitate when setting the mold?



[mojaverockets]

@benmerkenhof

We use agitation and vibration to eliminate bubbles. We are currently looking at several possibilities for the anomaly.

[stockpotato]

Das ist nicht so gut. I think you need to coat the grain (the inside of the star) so that it doesn't ignite like that.

[JandoCalrissian]

Wow! A great reminder that rocket surgery is difficult, dangerous work. Fix it, fly it! Keep up the good work!