Rocket Activity
Water Rocket Launcher
Objectives
Construct a launch platform for launching
water rockets.
Description
Water rockets, built from plastic soft drink bottles,
are capable of flights greater than 100 m. The
bottles are partially filled with water and pressurized
with compressed air delivered by a hand bicycle
pump or small compressor. A special launch pad is
National Science Content Standards
required for holding the rocket while it is being
Physical Science
pressurized. When the desired pressure is reached,
• Position and motion of objects
the rocket is launched by releasing hold-down
• Motions and forces
clamps. The instructions that follow explain how to
Science and Technology
construct the launcher and provides a list of needed
• Abilities of technological design
materials. Only a few tools and simple construction
techniques are required to construct a launch pad
National Mathematics Content Standards
that can be used year after year.
• Measurement
National Mathematics Process Standards
Materials • Connections
-Refer to the shopping list (see page 91) Management
-Saw
-Drill Most of the materials on the shopping list are
-Screw driver obtained from a hardware/lumber store. If needed,
-Bicycle pump or small electric compressor the list can be given to a salesperson to assist in
locating the needed parts. The list includes sizes,
descriptions, and the number of each part required.
A scrap piece of 2 x 4 may be available at the lum-
ber store. You will need two short pieces, 6 in. and
3 in. long. The short piece should have pilot holes
drilled for the screws that will attach the block to
the launcher base. The block supports a launch rod
that guides the rocket during the first few moments
of the liftoff. The other block should have pilot holes
for attaching the corner irons to mount the block to
the base and for supporting the hold-down clamps.
Rockets Educator Guide 87
Although not required, it is recommended that the 6. Drill two pilot holes into the small block (part
wooden parts are painted or varnished. These parts #2), laid on its side. The holes should go straight
will be blasted with water each time a rocket is through. Place the block next to the flange opposite
launched, and finishing the wood will reduce poten- the first block. Screw it in place.
tial warping.
7. Push an empty soft drink bottle on to the stopper
Assembly Instructions for alignment of the other parts to be added.
1. Screw the galvanized floor flange (part #7) to the 8. Drill a hole in the small block large enough to
center of the launcher base. accept the launch rod (part #4). The hole should be
positioned so that the rod will just rest against the
2. Slide one end of the air hose (part #13) into the side of the bottle.
center hole of the pipe tee (part #9). The hose
should be bent so that it extends about 7 cm out 9. Align the two 8 in. mending plates (part #11) with
the top hole of the tee. It will take a little force to the bottle lip (just above the cap threads - the bottle
make the bend. is upside down). You will probably have to adjust the
height of the stopper. When launching, the bottle
3. Thread the brass nipples (part #8) into each end neck (rocket nozzle) will have to make a tight seal
of the tee. The hose will extend through the top with the stopper. The mending plates (hold down
nipple. clamps) press and hold the bottle on the stopper
while air is being pumped in. Turn one or both of the
4. Jam the barb splicer (part #10) into the end of the nipples to raise or lower the stopper and the bottle
hose that you pushed through the tee and nipple. to match the clamps with the bottle lip. (The two
Push the other end of the barb into the hole of the plates are like vice jaws that pivot sideways against
stopper (part #12). The wide end of the stopper the bottle neck just above the lip.)
should be nearest the nipple. Pull on the hose until
the stopper just rests on the tee. Thread the lower
nipple into the flange.
5. Stand the 6 in. 2 x 4 block (part #3) next to the
flange. Mark screw holes for three corner braces
(part #6). The braces will hold the block in place.
One brace goes on each side and one on the side
of the block opposite the flange. Drill pilot holes
into the base and the block. Screw the block to the
base.
Rockets Educator Guide 88
Screws inserted into the second hole (from the 12. Thread the hook and loop cable tie (part #14)
back) of each plate serve as fulcrums. The plates through the end screw hole of one of the two
pivot inward to grab the bottle. (When the plates mounting plates. This permanently attaches the tie
are pivoted outward, they release it.) When you are to the plate. Tie the launch string to the other end of
satisfied that the plates will get a good grip on the the tie. The string should be about 4 m long.
bottle, mark the positions of the second holes and
screw the plates to the upper end of the large block. 13. Connect the bicycle pump or compressor hose
Screw them in just enough to keep the plates from to the air hose. Depending upon the kind of pump
rocking but not so tight as enough to prevent them you have, you may have to obtain a connector to
from swinging from side to side. fit the pump. One approach is to install a second
barb splicer into the other end of the launcher’s air
10. Install two guide screws about 3/4 in. apart. The hose. Cut the pump hose and push the barb into it
guide screws ensure that both plates open fully and to make the connection. Use small hose clamps to
release the bottle. Refer to the diagram to see the secure the barb to the hose. Other kinds of connec-
positioning of the plates on the 6 in. block. tors are available, and some experimentation may
be necessary. (One approach is to take the launcher
11. Wrap several rubber bands around the short and your pump to the hardware store and ask for
ends of the clamps. You will have to experiment a recommendations.)
bit to get the right tension in the bands to pull the
clamps apart for the launch.
Top Down View
of Hold-Down
Clamps
Placing the hold-down clamps (8 in. mending plates)
The diagram above shows the position of a rocket bottle. The clamps are screwed into the block and are free
to swing side-to-side. The guide screws ensure that both clamps open at the same time (not just one opening
wide and the other one staying put). When ready for launch, the clamps are swung to the middle to grab on to
the bottle neck just above the lip. The diagram to the right shows the hook and loop cable tie wrapped around
the clamps. When the string is pulled, the tie is peeled off, and the clamps are released. The rubber bands on
the other end of the clamps pull them apart, and the rocket lifts off.
Rockets Educator Guide 89
Tips on Using the Launcher • To place a rocket with water inside on the base,
hold the rocket horizontally. Tip up the base and
• It is important to keep the bottle sealed with push the nozzle onto the stopper. Grasp the
the stopper as it is being pressurized. If the bottle with the clamps and hold them in position
bottle leaks (a small spray comes out as it is with the cable wrap. Set the rocket and launch
being pressuized), the seal is too loose. Raise platform level. It is not necessary to anchor the
the stopper by unscrewing one or both of the pad on the ground.
nipples a turn or two to elevate the stopper.
• A small pull on the string attached to the cable
• New plastic (PET) soft drink bottles are capable wrap is enough to peel it back and release the
of withstanding about 100 or more pounds per hold-down clamps.
square inch (psi) of pressure. A 2 to 1 safety
factor is recommended. Do not let students • Students near the launcher should wear eye
pump the bottle above 50 psi. Bottles can be protection while the rocket is being pressurized
damaged during the construction process. and launched.
Also bottles can be damaged on landing. Retire
water rockets after 10 flights or sooner if you • Keep other students about 5 to 10 m from
suspect damage. the launcher (further if you elect to use higher
launch pressures).
• Do not let students attempt to catch their rock-
ets unless the rocket has successfully deployed
its parachute.
Completed Water
Rocket Launcher
Rockets Educator Guide 90
Rockets Educator Guide 91
