Let the Fun Begin!

So now that we have a fueled rocket, and safe bunker to test it's time to light this candle (Bad paraffin wax pun intended).

So I made some modifications to my bunker. I finally added wheels and a vice as you'll see in the video. It's also worth noting I clamped the video camera to the bunker, so that I would not have to be near the rocket the first time I ignited it. I felt that since I was a couple of small holes away from building a pipe bomb that I might not want to stand on top of it and take video.

Anyway, I connected the lines that run from the O2 tank to the rocket. I dowsed a few threads from a rag I cut up in gasoline, and threaded them through the exhaust nozzle to so that they contacted the wax inside the rocket body. The whole set up looked like this video I took from the day before the test fire. You can see that this is before I modified the bunker.



I actually ended up doing a small trial that day without the exhaust nozzle. Basically the rocket turned into a flamethrower that shot flame a good six to eight inches behind it. I have video of it but it's pretty crappy.

Tonight, I did the same exact set up, but with the improved bunker, and I kept the exhaust nozzle on this time. The results speak for themselves...



On a final note, the sputtering that you see in the video was actually caused by me. Throughout the burn I was constantly playing with the oxygen flow rate. I wanted to put it at full power, but when I would the flame would literally light up the sky. There were a couple of points in the burn where I goosed the throttle, and then had to ease it back. The next test will be 100% oxygen flow throughout the entire burn.

Can I Get $20 of Regular?

So tonight I'll explain how I add the solid rocket fuel to the rocket body. First thing's first, we need to decide on a fuel.

Basically there are a couple of criteria that you want to look at. The first thing is fuel stability. You want something that by itself is relatively harmless and nonreactive at room temperature. Secondly you want to look at whether the substance you're going to use can be molded to shape the inside of the rocket body. And the last criteria you want to look at is the amount of "pop" the fuel is going to give you.

So for this first rocket I'm going to use paraffin wax. It's the same wax household candles burn, so obviously it's safe. It can be melted down and then fit into a mold, and if burned at high temperatures like we're going to do it will certainly produce a lot of energy.

So step one go out and buy some candles. Try to get the unscented ones. I say that because when you melt it down, scented candles will obviously release their aroma. My house has smelled like oranges for the past three days, which in all honesty is a welcome change.

Step two is melting that candle down. Get a pot. Strip the candle of any stickers and plastic that may be on it. Throw the candle in the pot, place it on the burner and fire it up to medium low heat. You don't have to melt all the wax, just enough to fill the body of the rocket engine.

While the wax is melting get a bowl, a wooden dowel and a sheet of paper. Tightly wrap one layer of paper around the dowel. Then cut the paper and tape it off. We're just trying to create a barrier that will separate the dowel and the wax so that they come apart easier. Stand the rocket up so that it is standing straight up on the bottom of the bowl. Next remove the top nozzle from the engine. Place the dowel inside the rocket body and make sure it's pushed as far down as it will go, and that it is not touching the cylinder walls. Now pour pour the hot wax onto the dowel. It should run down the dowel and into the engine. At this point do not touch the rocket body. It may burn you. Keep filling the engine until the wax reaches the top. Blow over the top of the engine to cool the wax so it solidifies. Once you see the top has solidified put the bowl, rocket and dowel in the freezer together for about 45 minutes. Once the 45 minutes have passed the rocket engine should be safe to touch. At this point slide out the dowel. you may need pliers to pull it out. Don't worry if the paper comes out or if it doesn't. Screw the nozzle back on and you're done fueling your rocket!

This whole process takes some time. If you're like me you'll want to hurry through it so you can test fire the engine. Try not to rush! This is an extremely important step in the building process, and needs to be done right.

And as always, take two extra seconds for safety. Don't spill melted wax all over yourself. It won't be comfortable...

Hardware Store Hibryd Rocket Construction Begins

So two nights ago, I finally got around to going to Home Depot. I bought a bunch of brass fittings, some plastic tubing and an oxygen tank, and I set to work on constructing a very simple rocket engine. This photo clearly illustrates the fittings:



The fittings are attached from left to right in the order you see above and the result looks like this:



The next thing you need to do is get you oxidizer. I'm using gaseous oxygen. You can buy this at home depot in the welding section. It's like $6-$8 bucks a container, so it's a lot cheaper than I would have expected. The expensive part is finding a regulator for it. Instead of looking around for one I picked up a Benzomatic Welding and Brazing kit. This came with an oxygen tank and a regulator that fit the tank. I had to cut the tubing that came with it, but it'll get the job done. So now you have a set up that looks something like this:



Now in the above picture you see the clear plastic tube connected to the black tube. I feel I should note that you can't just put them together like that. You need to get some more fitting and actually make that joint there. I forgot to buy those parts when I was at the store, but I took the picture anyway. So the joint is missing from the picture.

So at this point you can see that your engine is starting to come together. In the next blog entry we'll take it a step further and I'll show you how to put fuel into the rocket engine. Until then have a good night and take two extra seconds and think about safety.

Safety First

So tonight I've pretty much nailed out the rocket test enclosure (bad pun intended). The whole enclosure is 32" wide by 24" high and 24" deep. I made the walls 5" thick all the way around. You'll see in the video below that the walls are hollow. This is so I can fill it with sand, or some other material that will absorb the impact of flying debris. I'm not going to actually pour sand in the walls. The plan is to actually line the walls with garbage bags, and then fill the garbage bags with sand. That way I can easily remove the garbage bags when I go to move the rocket test enclosure. I'm also toying with the idea of adding wheels to move it around because although it's not ultra heavy, it certainly cannot be defined as "light". Check out the videos below for a little more clarity.

They came out really dark. Next time I'll use a better camera.