gwx Posted May 21, 2006 Posted May 21, 2006 In my country model rockets are not allowed except with a license ( which i guess nobody holds anyway ) so i'm just experimenting. My question is that I have not found the right glue or the right melting process to melt the KNO3 and Sugar. So would it be possible for me to just place the KNO3 and Sugar into the rocket tube as a endburning oxidiser+fuel? Would it create enough thrust? On the other hand, I am also worried it will cause an explosion because a single sparkler leads into the rocket tube.... thus the nozzle is only the size of a sparkler.... As long as the initial stage goes by OK, i guess the back should be Ok. Since the material for the nozzle is not meant to withstand heat well, it will melt away and allow for gases to escape easier. I can add in some potassium permanganate + sulphur + Al powder mix to boost the rocket halfway if there is not enough thrust.. Please reply soon thanks!!
BigBang Posted May 21, 2006 Posted May 21, 2006 What ever you do, don't use KMnO4 flash to boost it, you WILL get hurt. You don't actually have to melt the propellant to get it to work, doing so just allows more propellant to fit into your motor and form a single, favorable grain. Make sure your chems are very fine powders and well mixed. You can ram this or better yet, press it into your case. Use a hard nozzle, for ease, try rammed kitty litter, that won't erode too easily. The gasses will escape just fine. You will need to use a core if you want it to get off the ground. If you still want it the size (I'm assuming diameter) of a sparkler, a small core (.5-1 mm diameter) running up the entire motor should prove sufficient. You a sturdy case so you it doesn't cato (hopefully.) Stay green, don't use that flash.
gwx Posted May 21, 2006 Author Posted May 21, 2006 Thanks for your reply! I'm totally a rocket newbie as my country forbids even model rockets but I just can't wait to get one off the ground.. I don't actually know about pressing and coring because when I read websites I do not get what they are talking about. Does pressing mean pressing down on the propellant by means of a wooden rod? My question is.... surely the grains will become loose again? =/ Also for coring, I think it means putting an object like a needle all the way through the rocket propellant grain and then pulling it out... My question is : Would the rocket propellant not fall back into the hole that was just created by the needle? Also for my rocket I am up to the part of covering the part where the sparkler leads to the propellant at the nozzle area.... I am planning to add the propellant from the top... Is it still possible to ram/press and core? Sorry if this is confusing...
FrKoNaLeaSh1010 Posted May 21, 2006 Posted May 21, 2006 Well When you ram or press your rocket you d it so hard that the powder packs down into one single very hard grain. It is essentially one block of propellant and then you drill out your nozzle/core so it wont fall to pieces or anything.
gwx Posted May 21, 2006 Author Posted May 21, 2006 Thanks for the idea... Seems like its going to be quite hard to get it done. Can I make the hole first, with a tool ( maybe some pens joined together with masking tape ). And then ram it with another tool which has cross-section like a doughnut. Then I would take out the pens I have.. ? Also for ramming, I can just use my bare hands to produce sufficient mechanical force for the propellant grains to stick together?
Mumbles Posted May 21, 2006 Posted May 21, 2006 Yes, the use of a former for the core works fine. It is actually safer than drilling out the propellant. I would suggest something like a hammer or something to provide the ramming force. It will be a lot better than just your hand pressure.
gwx Posted May 22, 2006 Author Posted May 22, 2006 Thanks for your reply!! clarified all my doubts. I cant wait to get my first rocket off the ground. Will launch it on tuesday if all goes well ( ie i can find the tools )
Boomer Posted May 22, 2006 Posted May 22, 2006 One important thing to mention is that melting sugar propellant is not done primarily to get more mass into the volume, but to get a more intimate mix, and NO VOIDS. The latter is the most important, that is also why you ram BP so hard it becomes a single grain, or use epoxy in composites. With loose powder, as the pressure rises the flame is pressed between the grains, spreading faster and faster until you get a mass ignition/explosion. In contrast, a compact grain can only burn from the surface, no matter how high the pressure gets. With too small a nozzle, it may still blow out the nozzle or end cap, but it won't explode all at once like a salute. That's what all my motors with loose or hand-pressed BP did: work as a salute!
Von Bass` Posted May 22, 2006 Posted May 22, 2006 Don't forget to store your motors in an airtight container - most compositions containing sugar and KNO3 appear to be hygroscopic, which means it takes in moisture from its surroundings. If you dont have any ziplock bags to seal them in, i would recomend firing them straight away or pouring molten wax into the nozzle to form a barrier, but leave a match stick in the plug to form a small handle. I have gone to a field several days after manufacture to find my motor is of consistency simalar to thick syrup!
gwx Posted May 22, 2006 Author Posted May 22, 2006 Right... I read about that somewhere Does a slightly sticky mixture mean some water has been absorbed?
Boomer Posted May 23, 2006 Posted May 23, 2006 Yeah at least *some*. Try a piece if it still burns as fast. Cling wrap, plastic foil with rubber bands, alu foil rolled and folded inwards, and especially jam jars work well for storage. Just keep air out. Sealing only the ends won't help with a paper tube btw.
Mr.Dan Posted June 1, 2006 Posted June 1, 2006 If you want a slightly stronger fuel for the rocket you can use a mixture of 63%KNO3, 27%sugar, 10% sulfur you will still need a core in the rocket. It works better just packed KNO3 and sugar, i am not sure about the melted method however.
Karl Posted June 1, 2006 Posted June 1, 2006 If you want a slightly stronger fuel for the rocket you can use a mixture of 63%KNO3, 27%sugar, 10% sulfur you will still need a core in the rocket. It works better just packed KNO3 and sugar, i am not sure about the melted method however. I havn't heard of this forumla before, I will have to give it a try. Thanks,Karl
FrKoNaLeaSh1010 Posted June 1, 2006 Posted June 1, 2006 I have used it. It deffinitely seems to burn faster then just dry mixed and rammed kno3/sugar. I still think the melted mix was a little better than the mix with sulfur additive. Would it be possible to melt the kno3/sugar/sulfur mixture or will the sulfur lower the ignition point too much?
Mr.Dan Posted June 1, 2006 Posted June 1, 2006 i wouldnt advise it sulfur lowers the ignition temp. i havent tried it. Mainly because when i tried to make smoke bombs by melting the composition it all went up in the pot, only 200grams but still enough to turn me away from melting propellents.
ApocalypsePlease Posted June 3, 2006 Posted June 3, 2006 I've been reading that you can use melted KNO3 and sugar as propellant, and not dry mix, but how would you pack it into the casing without making a gooey mess with air pockets? I've melted it before, and I don't think the consistency is very good for pouring and filling the casing evenly... Any suggestions?
justanotherpyro Posted June 3, 2006 Posted June 3, 2006 There is a point in the cooling stage that it gets to a playdough consistency, put it in then and press it.
ApocalypsePlease Posted June 8, 2006 Posted June 8, 2006 Alright thanks. When I get my lab set up, I may do an experiment testing different ways of using KNO3+Sugar. Dry mix, melted, Rcancy...
Pyrohawk Posted June 8, 2006 Posted June 8, 2006 Well it really depends on how they melt and form it. If you just melt the two togethor then it never gets a play doughy consistency. You have to just pour the propellant into a mold carefully to never get any air bubbles. Now if you Recrystalize the propellant "then" it gets to be moldable every time you heat it to 200F. Dry mixed, melted and recrystalized are the three common methods of using it.
Electron Posted June 8, 2006 Posted June 8, 2006 I've been reading that you can use melted KNO3 and sugar as propellant, and not dry mix, but how would you pack it into the casing without making a gooey mess with air pockets? I've melted it before, and I don't think the consistency is very good for pouring and filling the casing evenly... Any suggestions? Read up on Nakkas website about reducing air bubbles, i think he used a chilled metal rod with a diameter about 10% less than the motor inside diameter to press out the air at regular intervals during the casting process. To make my molten propellant a lot more pourable i add ethylene glycol in the form of antifreeze. I use : KNO3 65% : Sucrose 33% : Ethylene Glycol 2% Melt all of the KNO3 and Sucrose together, when this is molten stir in all of the Ethylene Glycol.
gwx Posted July 3, 2006 Author Posted July 3, 2006 Its so viscuous and difficult to put into the engine casing ( melted kno3-sugar ) but i did it anyway and rocket launched quite well and fast. It was cored btw.
justanotherpyro Posted July 3, 2006 Posted July 3, 2006 Well it really depends on how they melt and form it. If you just melt the two togethor then it never gets a play doughy consistency. You have to just pour the propellant into a mold carefully to never get any air bubbles. Now if you Recrystalize the propellant "then" it gets to be moldable every time you heat it to 200F. Dry mixed, melted and recrystalized are the three common methods of using it. Every time I have melted KNO3/sucrose It gets to a workable dough-like consistency. After its melted together thoroughly, I turn my hot plate onto 1 ( lowest setting I have ) and it keeps it at a workable stage as long as I stir it around every 30 seconds or so to prevent hotspots.
gwx Posted July 4, 2006 Author Posted July 4, 2006 I've been reading that you can use melted KNO3 and sugar as propellant, and not dry mix, but how would you pack it into the casing without making a gooey mess with air pockets? I've melted it before, and I don't think the consistency is very good for pouring and filling the casing evenly... Any suggestions?Read up on Nakkas website about reducing air bubbles, i think he used a chilled metal rod with a diameter about 10% less than the motor inside diameter to press out the air at regular intervals during the casting process. To make my molten propellant a lot more pourable i add ethylene glycol in the form of antifreeze. I use : KNO3 65% : Sucrose 33% : Ethylene Glycol 2% Melt all of the KNO3 and Sucrose together, when this is molten stir in all of the Ethylene Glycol. Hey may I know if this is glycerin? Also can I just use a bit of glycerin without measuring the weight? I mean, does it really matter. E.g. I take 60% kno3 40% sugar and add some glycerin inside until it is pourable? Thanks lots dude!!!!
Electron Posted July 4, 2006 Posted July 4, 2006 Glycerin (aka glycerine, glycerol, propane 1,2,3-triol, 1,2,3-trihydroxy propane) is a similar but different substance to glycol (ethylene glycol). I have wondered about using glycerol myself, i just havn't got round to it yet, i imagine it will work though. You could try using glycerol without weighing it, but you will of course achieve inconsistent motors. If you are just adding it in at the end add it slowly and be content with any reduction in viscosity. Glycerol is a fuel and hence will affect your oxidiser-fuel ratio. Speaking of ratio, i would advise you to use more oxidiser in your propellant if you are to try to thin it, to at least 65% oxidiser. I'm assuming you don't have a balance that is accurate enough to measure small quantities of glycerol, since it is a liquid you can measure it in volume to measure its weight :-glycerol has a density of 1.59 g/cm3, so say you were making 100g of propellant and 2% is glycerol, use 2/ 1.59 = 1.26 cm3. Good luck and let us know if glycerol works as a thinner.
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