THEONE Posted September 16, 2011 Posted September 16, 2011 Boys i have made a motor with r-candy with sulfur and it looks pretty good but that i want to know if this produce more energy than regular r-candy or not 60% kno324% sugar12% glucose syrup14% sulfur
r1dermon Posted September 16, 2011 Posted September 16, 2011 it'll produce a higher average thrust, but not as high total impulse. sulfur will increase the burn rate of your propellant.
donperry Posted September 16, 2011 Posted September 16, 2011 I dont like the 60% kno3.Do you use GDL_Propep? ITs great for e.x fuels another one i use is GUI pep
THEONE Posted September 17, 2011 Author Posted September 17, 2011 (edited) it'll produce a higher average thrust, but not as high total impulse. sulfur will increase the burn rate of your propellant. As you can see i have add more than normal sulfur, sulfur works as catalyst but i have add more than normal so the burning rate it will decreased... I dont like the 60% kno3.Do you use GDL_Propep? ITs great for e.x fuels another one i use is GUI pep I really do not know what are these... Edited September 17, 2011 by THEONE
donperry Posted September 18, 2011 Posted September 18, 2011 To produce more energy you will need a different oxidizer. KNO3 has basically been exhausted. What you can use is red iron oxide to ensure it gets a good burn. This, theoretically will not produce a better ISP. But in reality it is different especially for the melted method.In the melted method the sugar wraps around the kno3 grains. This is not as closely bonded as rCandy. Thus, the rcandy slightly is better performing WHEN DONE CORRECTLY. The major drawback with rCandy is that we have to be patient to get the moisture out. The best thing you can do is run your fuel ratios thru PEP based software like this one http://www.lekstutis.com/Artie/PEP/
donperry Posted September 18, 2011 Posted September 18, 2011 UPDATE I ran your formula thru propep You should know your formula does not add up to 100 I got an Isp of 143.9 Traditional ratio would give 150 But that's not a bad tradeoff if you are going for the flame
THEONE Posted September 18, 2011 Author Posted September 18, 2011 Something else, when i test the motors they work fine, but when i put them fly, most of times they CATOed, has anybody any idea why this it happens ? P.S. my motors are erosion burning cause the nozzle is 9mm and the core is 10mm
r1dermon Posted September 19, 2011 Posted September 19, 2011 describe the CATO...nozzle failure? casing failure? do you actually get unburned chunks of fuel being spit out the nozzle? sulfur is not needed in rcandy motors. KNO3 and sorbitol, if prepared correctly, can attain an isp nearly 200.
THEONE Posted September 19, 2011 Author Posted September 19, 2011 (edited) Sometimes i had an end cap CATO but most of times (90%) was the nozzle , if CATO happens, a grain also comes out of the casing and burns outside of the casing...It CATOes, when i know that the same engine another times with the same nozzle-fuel works well This one when the end cap CATOeshttp://imageshack.us...os/594/i8n.mp4/ Edited September 19, 2011 by THEONE
dagabu Posted September 19, 2011 Posted September 19, 2011 Those are not CATOs, you are over pressuring the ends and you will have to find a way to contain the nozzle so that it does not blow out. -dag
THEONE Posted September 20, 2011 Author Posted September 20, 2011 Those are not CATOs, you are over pressuring the ends and you will have to find a way to contain the nozzle so that it does not blow out. -dag It is not over pressuring, this motor was 4 bases grains like this one , as you can see the test works well...
dagabu Posted September 20, 2011 Posted September 20, 2011 If the nozzle blows out but the tube does not part, it is a classic over-pressure. -dag
THEONE Posted September 21, 2011 Author Posted September 21, 2011 (edited) If the nozzle blows out but the tube does not part, it is a classic over-pressure. -dag It is impossible to me the tube does part, because my glue (PVC pipe cement) is not good enough... Also more pressure exists at the top , so it is logical that the end cap will failure not the nozzle correct ? Edited September 21, 2011 by THEONE
THEONE Posted September 21, 2011 Author Posted September 21, 2011 (edited) I got an Isp of 143.9Traditional ratio would give 150 So what is going on here... Edited September 21, 2011 by THEONE
r1dermon Posted September 21, 2011 Posted September 21, 2011 You will need to use a proper pvc cement. The mechanical bond on your casing is not strong enough to contain the chamber pressure. You need a chemical bond.
THEONE Posted September 21, 2011 Author Posted September 21, 2011 (edited) You will need to use a proper pvc cement. The mechanical bond on your casing is not strong enough to contain the chamber pressure. You need a chemical bond. 1) The PVC cement is fine but i have notice that it melts the PVC but does not melt the coupler... i do not know why, maybe the coupler is from an another material 2) That is why i use very low KN round 110 ΜΑΧ 3) Also the motor were CATOed was the same motor at the test and the test works well!! It is not over pressuring, this motor was 4 bases grains like this one , as you can see the test works well... But when i put them to fly it CATOesThis one when the end cap CATOeshttp://imageshack.us...os/594/i8n.mp4/ The motor at flight and at the test was the same! Edited September 21, 2011 by THEONE
THEONE Posted September 29, 2011 Author Posted September 29, 2011 sulfur is not needed in rcandy motors. KNO3 and sorbitol, if prepared correctly, can attain an isp nearly 200. What about KNSU propellant, how the isp can be increased ?
WSM Posted September 30, 2011 Posted September 30, 2011 (edited) When I was a lad (back in the 60's) I came up with a modified potassium nitrate/sugar mixture that approximates: 70 KNO320 sugar (sucrose)10 S I remember calling it "Yellow Powder" due to the color caused by the presence of the sulfur in the mix. It burned slowly with a noticeable violet flame because of the potassium. I imagine it would be fairly powerful if catalyzed by some red iron oxide. It may well make a respectable rocket propellant. My Mom never could understand why I had a five pound bag of dusting sulfur stashed away in my closet. WSM Edited September 30, 2011 by WSM
aeon Posted October 1, 2011 Posted October 1, 2011 (edited) What about KNSU propellant, how the isp can be increased ? The information given by r1dermon is completely incorrect - your GUIPEP runs are correct! KN-sorbitol has a maximum ISP attainable of 164 seconds at 1000 psi. r1dermon, why spread this misinformation? If by 'correctly prepared' you mean run in a case capable of holding together at 5000psi and exhausting into vacuum, then sure, but this hardly typical wouldn't you agree? KN-sucrose has a slightly higher theoretical ISP, but not by much. In practice KN-dextrose has the highest ISP as it casts easily and reproducibly unlike KN-sucrose, and does not exhibit mesa-burn-shape profile unlike KN-sorbitol (sorbitol has some weird pressure-burnrate behaviour at higher pressures where the rate deviates from the usual r=aP^n St. Roberts power-curve-law) and so a higher duration of the burn is spent at design pressure (at least if you design the motor as using a geometry the delivers a near flat exposed burn surface profile) and hence higher performance is observed. Edited October 1, 2011 by aeon
THEONE Posted October 1, 2011 Author Posted October 1, 2011 (edited) About the APCP propellants, were you can find any Low energy fuels acting as binders ( HTPB - CTPB - PBAN ) Edited October 1, 2011 by THEONE
THEONE Posted October 1, 2011 Author Posted October 1, 2011 I have seen that the slow burning rate at almost all fuels is a disadvantage like here but why ?
dagabu Posted October 1, 2011 Posted October 1, 2011 Slower burning ANCP is a great fuel for rockets as is APCP, they both have advantages and disadvantages as well. I don't, however see the slower burning rate as a disadvantage in model rocketry though, it allows for a lighter rocket to reach great altitudes due to the longer burn time of the fuel grains. Care must be taken when preparing the AN though as the speed of the fuel varies greatly with just a small particle size change. It really needs to be air-float to work properly. -dag
aeon Posted October 1, 2011 Posted October 1, 2011 Polyurethane or silicone, if you want elastomeric chemically-curing binders...
aeon Posted October 1, 2011 Posted October 1, 2011 To get acceptable burnrates with ANCP it needs to be highly metallised, usually with superfine Mg. Also, AN undergoes a phase change around room temperature, changing density drastically which cracks grains and otherwise debonds the oxidizer from binder, ruining the mechanical properties. It's also hygroscopic, and has a rather poor exponent ('n'), usually around 0.5-0.6, which makes it's burn rate highly dependent on pressure. By comparison, AP is usually anywhere between 0.2 and 0.35 uncatalyzed, and up to 0.5 with heavy catalysis, CuO in particular.
THEONE Posted October 1, 2011 Author Posted October 1, 2011 To get acceptable burnrates with ANCP it needs to be highly metallised, usually with superfine Mg. Also, AN undergoes a phase change around room temperature, changing density drastically which cracks grains and otherwise debonds the oxidizer from binder, ruining the mechanical properties. It's also hygroscopic, and has a rather poor exponent ('n'), usually around 0.5-0.6, which makes it's burn rate highly dependent on pressure. By comparison, AP is usually anywhere between 0.2 and 0.35 uncatalyzed, and up to 0.5 with heavy catalysis, CuO in particular. So ANCP it doesn't recommended at all...
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