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RU Physics

Dr. Rhett Herman
Department of Chemistry and Physics

Welcome to my simple 2-liter water rocket homepage.

On this page, you will find plans for a simple, easy-to-make 2-liter water rocket and launcher capable of launching to heights of 30m or more. This particular design grew out of my wanting to build a rocket and launcher without resorting to ordering parts off the internet, or without spending several days putting the pieces together. All of the materials for this rocket were purchased at a local hardware store--Ace Hardware, in my case (yes, you even order from their website). However, with the parts descriptions below, you are not limited to Ace. After acquiring the parts and tools listed on this below, the time from assembly to launch should be about one hour. And while you can certainly find more eleborate, creative and flight-efficient designs on the web, I wanted something that almost anyone could build with minimal time and effort.


First, here is a picture of the assembled launcher. It takes approximately 30 (unhurried) minutes to assemble this launcher and have it ready to operate. Here is a picture of the launcher with a with a simple rocket on top; the pieces of the launcher are spread out on the table in front of the launcher. Assembling the rocket (three, 2-liter bottles) and the nozzle mechanism takes approximately 10 minutes, but five of those minutes are waiting for some superglue to dry.

Here is a picture (~87k) of the launcher with all the pieces identified. The parts are listed in the table below in the order in which they appear starting at the top. Here is a large (~416k) picture of the pieces with things laid out in order. Note that this picture has just the two-piece quick connect hose coupling. I listed the starter pack in the table below since it had two of the pieces that I use in the rocket nozzle. Finally, a picture of the rocket nozzle.

Launcher parts list

Launcher part description part #
quick connect adapter; female thread Ace #76953 Starter Set
hose washer, inside next piece (swivel) Ace #70332 (yellow, pack of 10)
3/4" to 3/4" brass hose swivel Ace #47041
hose washer, inside previous piece (swivel) Ace #70332 (yellow, pack of 10)
3/4" male hose thread to 3/4" male pipe thread; brass Ace #47037
1/2" copper pipe to 3/4" pipe thread adapter; copper Ace #41302
1/2" copper pipe; 12" long
1/2" copper pipe straps Ace #41833
1/2" to 1/2" copper pipe elbows Ace #41320
1/2" copper pipe; 30" long
1/2" copper pipe to 3/8" female pipe thread; copper Ace #41303
3/8" male to 1/4" fem. bushing; brass Ace #41277
1/4" Schrader air valve Ace #45194

Launcher tools and supplies list

description part #
three 2-liter drink bottles with their caps
hand drill or dremel tool
propane torch kit Ace #22011 (yes, the small one)
pipe solder Ace #27158
solder flux Ace #20586
teflon pipe thread tape Ace #40972

To assemble the launcher, follow these steps:

Top part, connecting to the rocket

  1. Insert one of the yellow hose washers into each side of the brass hose swivel.
  2. Screw the cuick connector into the "hose thread" end of the brass hose swivel. Be sure that you have the correct side of the hose swivel by seeing if the quick connector goes all the way in without the hose washer.
  3. Screw the brass hose thread/pipe thread adapter into the other side of the brass hose swivel.
  4. Apply 2 layers of teflon tape to the pipe thread end of the pipe thread adapter. This is the easiest way to make a tight seal.
  5. When you have completed (finished the simple welding) the L-shaped part of the launcher, screw the pipe thread adapter into the copper pipe to 3/4" thread adpater.
Middle part, L-shaped
  1. Cut a 30" length and a 12" length of copper pipe.
  2. Brush a small amount of the solder flux onto one end of the 30" pipe and into one side of the copper elbow joint. Insert the 30" pipe into the copper elbow.
  3. Following the directions in the propane torch kit, solder the two pieces together. Use a clamp to hold this since the copper pipe will conduct the heat.
  4. After the first joint cools for about 2 minutes, repeat the previous step with the 12" piece of pipe and the other side of the elbow. Try to keep the joint as near to a right angle as possible. However, if it's a few degrees off, that's fine since we're not achieving orbit here.
  5. Solder the (copper) 1/2" copper pipe to 3/4" pipe thread adapter to the remaining end of the 12" copper pipe.
  6. Solder the (copper) 1/2" copper pipe to 3/8" female pipe thread to the remaining end of the 30" copper pipe.
  7. Allow the solder joints to cool for about 5 minutes.

Note: I have recently been told that hardware stores now have a "glue" for copper pipes that is easier than soldering the copper pipes together. (Thanks to J.D.L. for pointing this out.)

Bicycle pump connection
  1. Put teflon tape on the threads of the 1/4 Schrader air valve. Screw that into the brass 3/8" male to 1/4" female brass bushing. This should be tight using pliers, but you don't have to use anything like a huge crescent wrench.
  2. Put teflon tape on the 3/8" threads of the brass 3/8" male to 1/4" female brass bushing. Screw that into the (copper) 1/2" copper pipe to 3/8" female pipe thread which is on the 30" copper pipe. Again, tighten with pliers.
Rocket connection
  1. Put teflon tape on the threads of the brass 3/4" male hose thread to 3/4" male pipe thread. Screw this into the 3/4" pipe thread adapter on the end of the 12" copper pipe. Tighten with pliers.
Launch stand
  1. Make this out of scrap wood, or pieces of 1" x 6" wood. I made the "L" shape using 1 1/2" wood screws. I mounted the copper straps using 1" wood screws. I prefer screws since (a) they hold better than nails and/or glue and (b) they can be removed and replaced as needed for disassembly.

The exhaust nozzle consists of 4 parts, and is held together by superglue. Here is a picture of the 4 nozzle pieces.

Rocket nozzle parts list

rocket nozzle part description part #
two, 2-liter (also 20-ounce) bottle caps, end-to-end
O-ring, 15/16 x 3/4 x 3/32 Ace #41944
quick connect adapter; male thread Ace #76953 Starter Set

Nozzle assembly

  1. Use superglue to put the two bottle caps together, back-to-back. (Be sure to sand the joined sides to roughen up their surfaces so the glue will stick.) One will screw right onto the rocket; the other will accept first the O-ring and then the quick connect coupling.
  2. Once the glue dries, use a drill or a dremel tool to make a 1/2" hole between the two caps. The water will flow easily through this hole.
  3. Insert the O-ring into one cap, and then screw the quick connector into that cap. You will only need to tighten this a moderate amount--don't strip the threads on either the cap or the quick connector.
  4. Back and front views of the nozzle show the finished item and the water route.

Note: When I first built my rockets I used superglue with decent success. This meant that for every two attempts to glue the bottle caps together one of them wouldn't hold under the pressure while the other would. But in recent builds I have used Gorilla Glue with more success. I do clamp the glued halves together with a cheap 2-inch clamp I get from the "cheap table" at my local hardware store (same store but no longer affiliated with Ace).

Assembling the rocket

The launcher with a the rocket shows how everything goes together. Two of the 2-liter bottles are joined by the middle section of the third 2-liter bottle. The two main bottles are pushed right against each other so that the five "feet" on the two bottles interlock--this keeps the whole arrangement remarkably straight (thanks to RU student Daniel Hansen for this insight) and stable in flight. The upper 2-liter bottle serves to stabilize this rocket during flight; only the lower bottle will have the water an pressurized air. This assembly needs no glue, and is ready for launching.

To launch this rocket, fill the lower bottle about 1/4 full with water. Put the nozzle on, and place the rocket in the quick connect socket. Attach a bicycle pump with a pressure guage to the 1/4" air valve. The bottles are tested at 7 atmospheres pressure, but I've found that 5 atmospheres is more than adequate for flights up to nearly 30 meters. Also, you'll be able to experiment and find there is an optimum fill level for flight height.

For safety considerations, you should not look directly at the rocket during pressurization (in case the lower bottle bursts).

You can certainly search the web for more efficient and elaborate designs, and even find multiple-stage mechanisms. However, I wanted something quick and easy, requiring very little "manufacturing" skill so that anyone could construct their own rocket. By the way: The "trigger person" who disconnects the quick connect coupling should expect to get soaked!

      To contact me, use any of the following methods:

snail mailphone/email
Dr. Rhett Herman
Assistant Professor of Physics and
   Adjunct Professor of Geology
Dept. of Chemistry and Physics
135 Curie Hall
Radford University
Radford, Virginia 24142
(540)831-5441 (office)
(540)831-6443 (department)
(540)831-6615 (fax)

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