I,Rocket flies on Nov 9, 2008 - Video here
Disclaimer: this page is not intended
to be used as directions to make rocket propellant and I assume no
liability for any use of the information posted here. This information
is meant only as a chronicle of my experiences in amateur rocketry.
This page will chronicle
my first attempts at making my own sugar based rocket propellant and a
new rocket to try it out in.
First off I'd like to say a big 'thanks' to Scott Fintel for his
inspiration and help.
You can visit Scott's
Amateur Experimental Rocketry Web site here
I will be using a 1.75" Motor
Casing supplied by Scott and will be using his casting method for
making 'Bates' grains out of a sugar based propellant using a mixture of 65% KN03 (Potassium, Nitrate) and 35% ER (Erythritol).
For this motor the grains will be cast in 'molds' made of 1.25" x 2.5" PVC pipe.
The motor will require 6 grains. If all goes well I should wind up with
a motor in the 'I' impulse range with somewhere between 50 and 60lbs of
thrust.
The
rocket will be approx 60" tall with a 3" diameter body.
Progress Reports:
Jan
6 2008
Nov 25, 2007
Nov 24, 2007
Nov 19, 2007
Jan
6 2008
It's been
awhile since I've updated my progress on the web site but I have been
working on the project. The Holidays and work have slowed me down
considerably though.
I ordered an RRC2 Altimeter from www.missileworks.com
and am working on an avionics bay. No pictures yet but will post some
soon.
I decided to try my luck at making a parachute. Thinking I was
getting a deal, I picked up some rip stop nylon for $4.99 a yard at a
fabric store in Sioux City that was going out of business. Then I found out the Hobby Lobby store in Sioux City carries rip stop
nylon in quite a few colors for a regular price of $4.99.
I dug out my Mom's
old sewing machine. I have had this old thing sitting in my basement for
several years and had never tried to use it so I had no idea if it even
worked.
I was ready to get going when I discovered I had no bobbins for the
machine. A quick stop on eBay and I had some bobbins and spare needles on
the way.
I got the bobbins and set about trying to figure out how the hell to work
the thing. It is an old Singer portable that my mother had received for a
high school graduation gift. After some searching on the web, near
as I could figure, the machine was a 66-16 from about 1948 or so. I
downloaded a manual and started studying.
The next step
was to decide what type of parachute I was going to make. Hemispherical,
Semi-Hemispherical, Parasheet, Octagon, Hexagon, etc.
I decided for simplicity, especially since I had never done any sewing
before, to go with a hexagonal flat sheet with six gores of alternating
color.
While it's certainly not perfect
I am very happy with my first attempt and I think this chute will do
nicely for this rocket.
I still need to make and attach the shroud lines.
Click on a thumbnail for a larger
image
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Mom's old Singer
worked great |
The finished
parachute. |
Nov 25, 2007
I glassed the fins last night using .75oz fiberglass cloth and West Systems 105 Epoxy.
I'm not sure if they really needed this added strength.
This morning I built a fin alignment jig. I drilled 1/16 holes along the root edge of the fins. These will help the epoxy hold the fins to the motor mount tube. I used thick CA to spot glue the fins on the tube in proper alignment. I then used 1" strips of fiberglass and epoxy to bond the fins the to motor mount tube.
Click on a thumbnail for a larger image
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Fin alignment |
Fins
are bonded to the MMT |
While the epoxy was setting on the Fin/MMT assembly I prepared my homemade nose cone lathe to turn an 11" Ogive Nose Cone out of a 3"x 3" x 12" block of balsa. An hour later and a big pile of balsa dust and Voila! A Nose Cone!
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| Nose Cone |
Nov 24 2007
Well after 5 castings, 3 grains per casting. I have finally 6 usable grains.
Before I cast the second batch of propellant I used a round file to smooth the inside of the PVC casting in the hope that I would be able to get the grains out of the casting tubes without having to beat them to death.
The second batch went well and the grains came out of the casting tubes much easier. In fact, I was able to get them out just by pushing them out with my fingers.
I now had 5 usable grains!!
The third batch went pretty well but again I could not get the grains out of the casting tubes. I had to beat them out and in the process cracked every one of them. Turned out I did not have the cardboard liners in the casting tubes seated properly and melted propellant got between the cardboard lining and the PVC casting tube wall, essentially gluing the grains into the casting tubes.
I must pay more attention to the preparation of the casting tubes.
For the fourth batch I decided to re-melt the bad grains along with leftover hardened propellant from the previous castings.
This batch was also a disaster as I simply could not get the melted mixture melted enough to pour smoothly. Instead it would sort of 'glob' out of the melting pot. It made quite a mess and the grains were unusable. I was somewhat puzzled by this and asked Scott his opinion on what may have happened. He thought perhaps that the re-melted grains had lost some sugar due to soaking into the cardboard liners and that was enough to throw off the ratio of KN to ER. Made sense to me. Since the grains are unusable, and I am certainly not going to try re-melting them again so I took them outside and lit them off just for fun.
You can see the video here
For the fifth casting I mixed up a fresh batch of propellant. This time I was extra careful to get my casting tubes prepped properly.
This was by far the best pour of them all. Maybe, just maybe, I'll get the hang of this yet.
Here's the line up...
Click on a thumbnail for a larger image
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6
grains and the motor |
I do not have the nozzle for this motor yet as Scott is making it for me so I still have time to decide on the size.
The Kn Calculator Software that Scott recently created is very handy for trying various combinations.
Here are a couple screenshots from the software
(the software is available on Scott's web site - see the link at the top of this page)
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Nozzle throat dia. of .3475" |
Nozzle throat dia. of .3" |
Since this motor won't do me much good without something to put it into I got started on the rocket today.
Here's a quick mockup of the rocket using VCP
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A starting point |
The Motor Mount assembly always seems like a good place to start. I went to my tube stock and found a nice heavy mailing tube. It was a it to big for the 1.75" motor casing so I sliced a .375" strip out of it and CA'd it back together.
Once the centering rings and fins are assembled to the tube this seam will also get epoxied.
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Cutting the Centering Rings |
MMT tube and CRs |
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MMT fins and bottom CR |
Nov 19 2007
I just completed my first attempt at making the KNER propellant grains.
I prepped the casting tubes and melted the the propellant mixture.
Once I had the what I thought was the right viscosity of melted propellant I began to pour it into the PVC casting tubes. I had some difficulty getting the melted propellant to pour smoothly, but other than that it was fairly easy. Next time I will heat the mixture to a higher temp to get a smoother flow out of the melting pot.
I allowed the propellant to cool for about an hour. The coring rods came out easily but I had the use a large dowel and a hammer to get the grains out of the casting tubes. One of the grains had some visible air pockets on the core walls and was unusable.
Click on a thumbnail for a larger image
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| Materials all laid out. | Casting stands prepped. |
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| Grains have
cooled for over an hour. The coring rods came out easily. |
Bottom of the cooled grains. |