Make Magazine project in Volume 15: Compressed Air Rocket. The basic idea is the same; build a pressurized vessel which releases the pressure through a tube and delivers it to a light-weight rocket propelling it into the sky. The project is elegant in it's simplicity and a heck of a lot of fun. My take on this project was a little different (but not much). I wanted to build something which had a stable launching platform or stand. Also I didn't want to use a bicycle pump (who wants to do all that pumping by hand?!) but instead use a shop air compressor.
Knowing myself and others who might like to play with this, having the ability to build up over 100 psi was just too tempting. So I was a bit concerned about using PVC pipe, even if it were wrapped in duct tape. Plus I have a 5-year old son who will be standing near-by, I didn't want to chance anything exploding. So my thought was; why not use black gas pipe? It's still relatively inexpensive but I feel would be a whole lot safer. I am not sure if the black gas pipe is necessary, but it seemed like a precaution which was worth taking. In the end I was pretty happy with the results. No worries of sun-exposure, very stable platform, compact and durable.
Rocket Launch Pad
The launch pad was made mainly from 1" and 3/4" black gas pipe and fittings. Many may think this is overkill. It probably is, but I guess I figured overkill rather than being killed is OK. I capped off the ends and added a quick connect air fitting to one of the pipe ends. This allows me to easily and quickly connect a portable shop air compressor when we are ready to shoot rockets.
The base itself is just made of scrap 2x4's, 2x6's and some plywood. To the sides I mounted an electrical box so that once connected to an extension cord for power I just need to plug in the compressor and 12V power supply (for the solenoid value) and we're ready to go. I also added a kill switch to the left side. This allows me to disconnect the 12V solenoid power. This is really handy when you have a bunch of kids over who want to keep pressing the launch button. This way when I am near the launching pad loading a new rocket I don't get hit with a stray rocket! They can hit the launch button all they want when the kill switch is off.
Here is the rocket launcher ready for firing --- It is connected to a Craftsman 125psi compressor and has an attached electrical outlet for power.
Here is the launcher with the "3-pronged" launcher attached. It's kind of fun to shoot 3 rockets off at the same time. Just make sure everyone is looking and yell "heads-up"!
The compression chamber is 1" gas pipe with 3/4" gas pipe teed off at 3 points. At one point my idea was to have three separate solenoid values to have time delayed launches. But I never did get to that. So they are capped off for now.
Making the Rockets
I have been experimenting with different types of rocket construction as well. The paper rockets described in the Make article work very well. But they are time consuming to make and the process is not very consistent. Lots off masking tape, folding, cutting, etc. I found that the 1/2" PVC pipe I have at the end of the solenoid value is the perfect size to hold an Estes BT-50 body tube. I found some body tubes on eBay, some Balsa nose cones (NC-50) and purchased some 3/32" x 3" Basswood to make fins. The process of making Basswood fins can be found on the Snap Dragon Rocket website. A little spray pain and you wind up with a pretty cool looking rocket.
I was concerned about the weight, but as it would be, both the typical paper rockets I made as well as the Estes style rocket I made were both 30g each. Overall the Estes-style rocket is cooler looking, but a bit more fragile I think. Flight however was not a problem. The BT-50 body style tubes worked great. The only problem right now is that the landing if awfully hard on the rocket without a parachute. I need to experiment more with making this more rugged as after only a few launches these rockets get pretty beat up.
Here is one of the more "traditional" paper rockets as suggested by the article. They work well but are somewhat time consuming to make.
This is one of the "Estes" style rockets I made from BT-50 body tubes, nose cones and Basswood fins. They look great and launch well, just a little fragile.