SUBJECT: Space Flight
DESCRIPTION: Rockets, using pencils for their bodies, are launched
with a rubber band-powered launch platform.
CONTRIBUTED BY: Gregory Vogt, OSU
EDITED BY: Roger Storm, NASA Lewis Research
MATERIALS and TOOLS:
- 2 Pieces of wood 3'X4"Xl" in size
- 2 Cup hooks
- 1 Wooden spring clothes pin
- 1 Small wood screw
- 1 Screw eye
- 2 Metal angle irons and screws
- 4 Feet of heavy string
- Iron bailing wire (18 gauge minimum)
- Several rubber bands
- Several wooden pencils (unsharpened)
- Several pencil cap erasers
- Cellophane or masking tap
- Heavy paper
- Wood file
- Drill (3/16 inch diameter)
- Join the two pieces of wood as shown in the diagram to form the launch
platform. Use a metal angle iron on each side to strengthen the structure.
- Screw in the cup hooks and screw eye into the wood in the places indicated
in figure 1.
- Temporarily separate the wooden pieces of the clothes pin and file
the "jaw" of one piece square as shown in figure 2.
Drill two holes through the other wood piece as shown. Drill one hole through
the first wood piece as shown.
- Drill a hole through the upright piece of the launch platform as shown
and screw the clothes pin to it so that the lower hole in the pin lines
up with the hole in the upright. Reassemble the clothes pin.
- Tie a knot in one end of the string and feed it through the clothes
pin as shown in figure 1, through the upright piece of the platform and
then through the screw eye. When the free end of the string is pulled,
the clothes pin will pen. The clothes pin has become a rocket hold-down
and release device.
- Loop four rubber bands together and loop their ends on the cup hooks.
The launch platform is now complete.
- Take a short piece of bailing wire and wrap it around the eraser end
of the pencil about one inch from the end. Use pliers to twist the wire
tightly so that it "bites" into the wood a bit. Next, bend the
twisted ends into a hook as shown in figure 3.
- Take a sharp knife and cut a notch in the other end of the pencil as
shown in figure 3.
- Cut out small paper rocket fins and tape them to the pencil just above
- Place an eraser cap over the upper end of the rocket. This blunts the
nose to make the rocket safer if it hits something.
The rocket is now complete.
LAUNCHING PENCIL ROCKETS:
- Choose a wide open outdoor area to launch the rockets.
- Spread open the jaw of the clothes pin and place the notched end of
the rocket in the jaws. Close the jaws and gently pull the pencil upward
to insure the rocket is secure. If the rocket doesn't fit, change the shape
of the notch slightly.
- Pull the rubber bands down and loop them over the wire hook. Be sure
not to look down over the rocket as you do this in case the rocket is prematurely
- Stand at the other end of the launcher and step on the wood to provide
- Make sure no one except yourself is standing next to the launch pad.
Count down from 10 and pull the string. Step out of the way from the rocket
as, it flies about 75 feet up in the air, gracefully turns upside down
and returns to Earth.
- The rocket's terminal altitude can be adjusted by increasing or decreasing
the tension on the rubber bands.
DISCUSSION: Like the flight of Robert Goddard's first liquid
fuel rocket in 1926, the pencil rocket gets its upward thrust from its
nose end rather than its tail. Regardless, the rocket's fins still provide
stability, guiding the rocket upward for a smooth flight. If a steady wind
is blowing during flight, the fins will steer the rocket towards the wind
in a process called 'weather cocking.' On NASA rockets, active controls
steer during flight to prevent weather cocking and to aim them on the right
trajectory. Active controls include tilting nozzles and various forms of
fins and vanes.
BACK TO THE ROCKET ACTIVITIES
Oklahoma State University