DubaiAmateurRocketry
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Sharing some information and experience on Ammonium perchlorate, Potassium nitrate-sucrose, and Zinc Sulfur based propellants.
Sharing some information/ experience on Ammonium perchlorate based propellants, Potassium nitrate sucrose propellants, and Zinc Sulfur propellants.
Ammonium perchlorate based propellants(APCP) introduction
In APCP, you'll need to use Ammonium perchlorate spherical so it allows better burning characteristics and easier mixing(casting). You can buy them
from chemical stores that sells it for pyrotechnique purposes. In APCP the binder usually cures with ureathane linkages(R-O-H+ O=C=N-R diol and
diisocyanate) most common diol for this purpose is HTPB and ethylene glycol. For Isocyanate compounds are MDI and TDI. I'm not expert in polymers and
you can read more about it here.
http://en.wikipedia.org/wiki/Polyurethane
Poly urethane rubber should be plasticized because without plasticizers it is a very hard plastic unsuitable for propellant use. Plasticizers such as
DOS, DOP can be used, it can decrease the glass transition temperature, Tg, and make the polymer like a rubbre, soft and streachable, and hard to rip
at the same time.
Cured polymer using 80% Ethylene glycol and 20% MDI without plasticizers, and as you can see, its just a piece of plastic-like material. (I'm going to
make some insensitive energetic plasticizer soon(maybe few month), wait for my results)
APCP manufacturing,
Mixtures for good OB. O % Ammonium perchlorate F % Binder 15% Aluminum powder O/F ratio as follow HTPB (70:15) Ethylene glycol/MDI (68:17)
I'm bad at describing things/ procedures however the general process of APCP follows.
Add all binder, heat to around 80°C, add all aluminum powder(suggest 600 mesh, use gloves, 600 mesh aluminum powder will take days/weeks to go off
your hand) Stir it for few minutes, add ammonium perchlorate last.(You want to add metallic fuel first because they are usually the densest part of
your fuel, and if you mix the metallic fuel first with the binder, you often get higher density because they sink better when visousity is still good,
when you add AP, the viscousity will be destroyed and become like a cake) The low binder content usually prevent or make it very hard us to cast it
since we dont have vacuum pumps which allows much less viscousity. However we can still make the less professional APCP, after AP is added to the
binder and aluminum, keep the temperature at 90 degree, no higher, and mix for around 5 mintues. After that, stop heating and put it into a mold/
grain and wait for around 2 days to cure at room temperature. After it cures, it should look something like this.
Top left: Cured APCP now ready to fire.
Top right: the grain's core and the rocket engine is manufactured almost perfect.
Bottom left: heating the aluminum powder/ binder at 90 degree in a water bath for a while before adding ammonium perchlorate
Bottom right: what it looks like to mix a 15 micron aluminum powder with EG/MDI at room temperature.
Any ways, you can simply not cast APCP and push it into mold, however it will have few air bubbles which might be dangerous under fast(too fast) burn
rates. By adding 1% asphalt destroyed the burn rate and make it burn extemely slow, this is desirerable since fast burn rate with bubbles in your
grain can explode)
Explosion of APCP.
Succesful APCP
burn time 2seconds, third picutre was peak thrust, it looks as if it was not very powerful however it is! The high temperature melted the casing in
the end.
Another successful APCP.
Because APCP is hard to cast, and not casting it makes danger for explosion, My team made eutectic propellants, where my oxidizer is dissolved and I
dont even need to mix and simply cast it.
http://www.youtube.com/watch?v=rPvb-_GrlKE
Two other mixtures of ammonium perchlorate based fuels.
Left : Burn test of 80% AP 18% PU and 2% Asphalt, asphalt successfully slowed down the burn rate to 0.1cm/s
Right: 80% AP and 20% Epoxy resin(this mixture is called APER), this fuel have a much higher burn rate, or we can call it deflagration. APER is known
to cause explosions because AP can expoy can react with amine compounds in epoxy to form perchlorate salts of these compounds which is explosive,
example is ethylene diamine diperchlorate.
Potassium nitrate/ Sucrose propellant (KNSU)
KNSU manufactured from 3 ways, simple grind and mix, recrystallize from water, and melt sugar to cast propellant, each have some advantageds and I
always made mine from recrystallization method, instruction as follows.
Add around 1 part water to 2 part KNSU (65% KN 35%SU), stir few seconds. Start heating the solution (don't worry if it is not dissolved)
Step1
Heat the solution, best using electronic heaters, 4 years ago when I constantly used KNSU as my rocket fuel, I liked to save my money up rather than
buying a heater so I heated my KNSU by burning alcohol, you can control alcohol's flame temperature on the flame's position(yellow is very hot and
blue is much cooler) and wind speed, when more air passes by the flame is much hotter, you can use aluminum foil to shield the sides to prevent air
movement and the flame will be much cooler, using those techniques I made my KNSU without electronic heating and never faced a accident.
Step2
Heat the solution best at 140°C until the solution is very saturated and when around half of the water is boiled away, bubbles like soap will form,
when water is boiling prevent extensive stirring because it prevent evaporation. Stir away the bubbles though because it will fill the pot. Note
boiling point increases when solution is saturated.
Step3
When almost all the water is dried, you have to take it out very fast, when the it cools as water evaporate, KNSU will solidify into a very hard, as
hard as a rock, that is very hard to grind if you fail to shape it into your desireable shape before the phase transition. (This is a hard process for
me because I often take it out before its dry enough to solidify) It should be a little bit wet, just wet enough so you can put the fuel into a mold
and wait for it to become a hard solid. This step takes few real life trials and experience to understand, take small batches, like 10, 20 grams, and
do it out side your house. Auto ignition temperature is around >180°C , dont over heat. Stop heating instantly when you see sign of decompostion
(sugar turning black) and take the fuel out.
When you take it out you should be fast, and put it into a mold asap. You also need to make a core out of it with a measured size before hand so you
can calculate how much seconds you want your engine to fire.
You can find so much more information about KNSU on http://www.nakka-rocketry.net/
Left: fuel just taken out of the pot (70 grams)
Right, after an hour, it turns into a hard solid.
Theres no time for you to wait in real life to take a pic and chill, the fuel solidifies pretty fast as it cools, because viscousity increases at
lower temperature and water is drying out at high temperature.
3 grains of similar sized were packed into a small still tube rocket engine.
This was one of my first engines, fired on 2009, burn time 1.5 seconds, average thrust was 2.8 lbs, peak thrust was 6.6 lbs.
Exhaust velocity alone the nozzle = 641m/s (Mach 1.9)
Peak altitude if it was launched = 426.3(vacuum) 319.7 meters with aerodynamic drag. Those values are calculated and might not be precise
Zinc sulfur (ZnS) propellant.
ZnS is the easiest to make out of all ive wrote above, you simply buy zinc and sulfur and mix them with few drops of acetone or alcohol and press it
into a grain, wait for it to dry, and there it is.
However a more effecient and high performance method exist which i've not tried - you can melt cast sulfur and add zinc dust to it. The ratio is 67.1%
Zinc to 32.9% Sulfur. Addition 5-10% Magnalium powder can be added to give a more beautiful/ effecient burn.
Ignition > Thrust > Burn out.
ZnS produce a lot of light for a long time after burn so it produce a very long flame. The flame of Zinc/ sulfur is one of the most beautiful to watch
with your own eyes.
Some problems of ZnS
-Heat produced not enough to fully evaporate the ZnS, although it does in combustion chamber, it turns solid while in the expansion part of nozzle as
it cools down, where you loss a good part of impulse. ZnS is also Not fully combusted until after being expelled out of nozzle, one of the reasons for
having such a long beautiful flame tail.
Solving those problems.
-Adding Aluminum increase the burning temp from around 2000 of a typical ZnS to over 2300.(I typed this line few years ago and I have forgotten the
source where I saw it from, Aluminum does burn hotter with sulfur than zinc, however im not sure of the temperature, I expect it to go lower) hot-melt
propellant of sulfur and zinc can fully coat the zinc with sulfur that burns much quicker and makes the efficiency go around 10% higher. On youtube,
there're people who hot-cast ZnS propellant and their videos are easily found by searching for ''zinc sulfur rocket''.
Here is a part of a book on ZnS propellants
http://users.cybercity.dk/~dk.../Notes/chapter_1_history.pdf
Ive done some of these few years back so some corrections are welcome.
[Edited on 19-12-2013 by DubaiAmateurRocketry]
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VladimirLem
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Hi DubaiAmateurRocketry
First, your tutorial is very nice and it seems to me that you have much experience and knowledge at rocketry, so i want to make a
litte experiment and i have really low skills at the rocket motor and i have only AN, KNO3, HNO3 and KCLO3 avaible (and sugar of course  , no perchlorates)
so my question is, how can i make a motor that burns for 1 second (+/- 0.3s) that works with nearly no delay after the ignition and, of course has as
much power as it can get...
i only made KNO3+sugar and have to say, most times it takes much to long, that it burns with full force after the ignition....(0.5-2s)
and how about HNO3, is there a way to make some motor without high tech equipment? the trust of motors with that oxiudizer are very awsome (and
dangerous of course  )
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DubaiAmateurRocketry
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Quote: Originally posted by VladimirLem  | Hi DubaiAmateurRocketryI have only AN, KNO3, HNO3 and KCLO3 avaible (and sugar of course , no perchlorates)
so my question is, how can i make a motor that burns for 1 second (+/- 0.3s) that works with nearly no delay after the ignition and, of course has as
much power as it can get...
i only made KNO3+sugar and have to say, most times it takes much to long, that it burns with full force after the ignition....(0.5-2s)
and how about HNO3, is there a way to make some motor without high tech equipment? the trust of motors with that oxiudizer are very awsome (and
dangerous of course ) |
1 second ? depending on your motor's inner diameter. KNSU burns a lot faster with some Fe2O3. I actually like long burn time, because it looks nice
hehe. To make up for the loss of chamber pressure on a longer burn, I just increase my motor's combustion chamber's length. The successful design I
had, the fuel was 30cm long, and 3cm wide. And the core was 27cm long, 0.5 cm wide, centered.
KClO3 is sensitive to impact and friction, and AN barely burns, and when it does, it chuffs a lot and its bun rate is not stable.
for HNO3, its complicated... i have not worked with liquid engine ever.
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Turner
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It looks like the thrust on the motor second down is going a bit to the right?
Also, in the pictures of the motor, is that with the fuel loaded? Is that a concrete nozzle?
Would you use PVC motor in a rocket with APCP?
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DubaiAmateurRocketry
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| Quote: Originally posted by Turner | It looks like the thrust on the motor second down is going a bit to the right?
Also, in the pictures of the motor, is that with the fuel loaded? Is that a concrete nozzle?
Would you use PVC motor in a rocket with APCP? |
The second motor was extremely powerful, You must know its dubai, the sun light is sooo bright, that it shaded the flame and the white wall shaded the
white line of smoke, it even had mach diamonds.
yes, for APCP, i do not dare use a steel one, if a steel one explodes, it can cause injuries.
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