N.E.R.D.S.
WATER Rocket Safety
Water Rocket Safety Rules
1. Water rockets should only be used under the guidance
of a trained professional (adult).
2. No metal or sharp objects are to be used on rockets.
Care must be taken when cutting bottles. Each
design must be approved by the supervising adult
before launch.
3. Launch area and range should be large enough and clear
before launching any rockets.
4. Only plastic drink bottles are to be used. New bottles
should be used whenever possible. Bottles which have
been exposed to sunlight for long periods of time should
not be used. Bottles should be retired from use
after 10-15 launches.
5. Safety goggles must be worn when within 30 feet
(10 meters) of a pressurized rocket.
6. One person, the designated safety officer, is to check
for safe practices and can stop a launch whenever
unsafe practices are observed.
7. One person is designated as loading officer and is
responsible for securing the rocket to the pad
and charging the rocket with the appropriate air pressure.
8. One person, the designated launch officer, commences
countdown and launches the vehicle.
9. Be sure the launch pad is secured to the ground before launch.
10. All persons should be at least 10 feet (3 meters) from the
rocket when it is being pressurized.
11. Use only bicycle pumps or air compressors to pressurize
rockets. Always have a means for accurately measuring
the air pressure. Never charge a rocket without air
pressure measurements. Keep electrical cords away
from all water sources. If a compressor is employed,
use long air hoses rather than long electrical cords.
12. Rockets can be pressurized with various air pressures, but
never above 90 psi under any circumstances.
13. Never go near or over a pressurized bottle.
14. Never lean over the top of a pressurized bottle.
15. All persons should face the rocket during launch, kneel down
low, and participate in the countdown. No one should be
facing into the sun (keep the sun at your back or over
your shoulder).
16. If a leak is observed during pressurization, stop adding
air and release the rocket using standard launch
techniques. Then repair the leak.
17. Bottles modified with fins, nose cones, and extra mass
should be carefully tracked by all personnel and
avoided as the rocket returns to earth. Never
attempt to catch a spent rocket or any payload
that the rocket has launched.
18. If the rocket fails to release after the pin is pulled,
immediately clear the area and inform the
adult supervisor. The supervisor will jiggle
the rocket with a long stick and cause it to
release.
Additional Safety Concerns for Teachers
As with any science activity, the teacher must be
proactive and establish an environment that is safe.
The following recommendations will help you manage this
activity effectively and safely.
Construction of Rockets
Two-liter bottle rocket safety starts long before
the launch. After the initial naked bottle launch, students
will doubtless start building their own rockets. Consider
the following suggestions as you prepare for this activity.
1. Any materials that students wish to use, beyond those
provided, must be approved by the teacher.
2. No metal pieces or sharp objects may be used in the
construction. Plexiglas make great wings, but should
be avoided.
3. Take special precautions when cutting bottles. For
elementary students, the teacher can make an
incision with a sharp carpet knife and the students
can complete the cut with round-tipped scissors.
4. Do not use hot glue when attaching fins to the rocket body.
The heat from the glue can weaken the plastic to
the extent that the rocket may not be able to withstand
launch pressures.
The Launch Site
A little forethought in the selection of your launch site will
illuminate many potential concerns. Do not select simply for
convenience, but consider the following factors:
1. A large clearing such as an athletic practice field or vacant
lot is best. When launching in smaller areas, use reduced
pressures and adjust the launch angle to compensate for
wind. Before launching downrange, the following table
should be consulted.
Table of Distances for a Given Pressure
Pressure Typical Classroom Maximums
_________________________________
20 psi 26 meters
40 psi 51 meters
60 psi 77 meters
80 psi 102 meters
100 psi 128 meters
_________________________________
*All data is based on a 1,000 ml volume, a 45 degree launch
angle and no wind. Current known world record is 800 feet
(240 meters) at 90 psi. using a 1.5 liter vessel. This “Aqua
jet” record is held by the Paisley Rocketeers’ Society in Scotland.
An to attempt to verify this data and/or develop your
own empirical table is a good class-wide experiment. For vertical
launches, both rocket design and prevailing winds can play a major
role in trajectory. Take this into account especially when using
rockets equipped with parachutes. Vertically, a rocket will
typically reach 150 feet (46 meters). Using free fall formulas
and assuming no air resistance, the projectile will be traveling
at about 65 miles per hour (100 Kph) when it hits the ground.
Taking these velocities into account, no one should ever attempt
to catch a spent rocket or payload. Additional safety margins in
the range must be established whenever adding weight to the nose
cones to enhance performance (these missiles can cause property
damage). When using nose cones it is best to secure them to the
2 liter bottle with a string so that after separation they do not
fall independently.
The Launch
In addition to those safety rules discussed on previous pages,
you should observe the following:
1. Have a limiting device on all electrical compressors to keep
bottles from being over pressurized. The industrial
specification of burst pressure from one manufacturer
is approximately 175 psi but bottle designs vary and
bottles can burst at lower pressures due to bottle type,
fatigue from overuse, poor construction techniques, or
exposure to sunlight. We recommend using pressures of
90 psi or less. Under no circumstances should you attempt
to perform a bottle burst test.
2. Always anchor the launch pad. When working on a solid concrete
area, you may be able to weight the pad down, tie it
down to something solid or attach the cord to a tree
or a building in the opposite direction to counter the pull.
3. If you are filling rockets with a garden hose, make sure the hose
has a shutoff valve and that water is kept some distance
from the paunch area. Keep the water off when not in use.
4. Having a supervisor responsible for completing a safety check
list before launching is a good idea, especially during
more complex experiments such as mass expulsion or
a new class arrives on site after previous use. A sample
check list is presented on the next page.
Launch Site Safety Officer Check List
The launch site safety officer is responsible for verifying that
the following safety practices are observed.
Before the launch
___ 1. The pad is inspected and appears to be functional.
___ 2. The pad is firmly anchored.
___ 3. The size of the launch area is adequate for the
experiment undertaken.
___ 4. Water is not freely running near the launch pad
___ 5. All electrical cords are well away from the launch
area and the water source.
___ 6. The launch pin is properly placed over the lip of the bottle.
___ 7. All personnel in the area are wearing safety goggles
before the bottle is pressurized.
___ 8. When pressurizing, the air line is extended as far
from the pad as is possible and established pressures
are not being exceeded.
___ 9. All personnel are paying attention to the launch and
have their backs to the sun, so they won’t lose sight of
the rocket.
At the launch
___ 1. Verify that the area is clear, Both in range and downrange.
___ 2. Instruct the launch officer to begin a countdown in which
all participate.
At the end of each class period
___1. All electricity is turned off
___2. All water source is off
___3. Launch area is cleared of all material and related trash
(used bottles, tape, parachutes)