YES, another great STEM activity with a new twist to the “egg-drop”…
Students are tasked to design and construct a soda bottle H2O rocket, successfully launch with its (egg) payload and recover unbroken (See Step 14 - Design Brief).
We spend time initially discussing the "design process". There are many versions, but the majorities have several steps in common: problem statement; defining criteria; research; brain-storming; modeling; testing; improvements; manufacture...
Many valuable lessons that can be incorporated into unit, i.e. Newton's Laws of Motion, Trigonometry, English-to-Metric Conversion, Statistics.
Engineers develop models to evaluate possible solutions.
Knowledge gained in other disciplines impact development of products & systems.
Research & development are problem-solving techniques widely used in the business world & technology.
Students will apply research and the design process to solve problems in and beyond the classroom...
Step 1: Constructing Launch Pad
To level the “playing field”, I constructed the launch pad… the materials you’ll require, with the exception of the tire valve, can be found at building supply or hardware stores.
10 feet - 1/2" PVC Pipe Schedule 40(DON’T CONFUSE WITH CPVC)
(1) 2” Long Piece, 1-1/2” PVC Pipe Schedule 40
(4) 1/2” Slip End Caps
(2) 1/2” Slip Tees
(1) 1/2" Tee, Slip & Internal Thread
(1) 1/2" Adapter, Slip & External Thread
(1) Small Can PVC Cement
(1) Small Can PVC Cleaner
(2) Hose Clamps w/at least 2” Diameter
(9) Multi-Purpose/Zip-Ties, minimum 8” Long
(1) Small Roll Duct Tape
(1) Small Roll Teflon Tape
(1) Small Roll of 2” Painter or Masking Tape
(1) Tire Valve/Stem – Local Automotive Supply Store
15 feet Twine or Thin Rope
(2) 2-Liter Soda Bottles
Tape Measure & Pencil
Hand Saw (Hack-saw, Back-Saw, or X-Cut)
1/2", 3/16” & 1/4" Twist Drill Bits
Heat Gun or Candle
Scissors or X-Acto Knife
Air Pump w/Pressure Gauge or Air Compressor
Step 2: Let's Begin...
CUT THE PIPE, six pieces, 12 inches long; one piece, 24 inches long; and one, 8 inches long of 1/2” PVC.
DRILL HOLE FOR TIRE VALVE, place an end cap on a piece of scrap wood, holding securely with pliers, first drill 1/4" pilot hole and then 1/2” hole in the top
INSERT THE VALVE, slide the valve through the hole in the end cap; grab the end of the valve cap with pliers and pull until fully seated.
Step 3: Glue & Assemble Base
GLUE & ASSEMBLE THE BASE, lay-out the pieces in the order in which they will be assembled: end cap, 12-inch section, slip tee, 12-inch sections, end cap, etc.
Clean the outside of the pipe and inside of the fitting with PVC pipe cleaner. Glue the pieces one at a time, cement sets in seconds…
Attach the 8” piece of PVC to the base with a pipe clamp to act as a string guide.
Step 4: Creating Bottle Seal
CREATE BOTTLE SEAL, this bulge will create a seal between the pipe and the soda bottle. Mark the vertical piece 10-inches from the open end. Using a candle or heat-gun, heat the pipe evenly at this mark until it becomes soft. Grasp pipe on either side of mark and push together to create a slight bulge. Hold the pipe straight until cool and no longer soft.
Step 5: Bottle Clamp
BOTTLE CLAMP; holds bottle tight to bulge. Tape nine (9) zip-ties together with duct tape, making sure the ties all face the same direction, are parallel and their heads line up evenly. Tape both sides to hold securely.
Slide a soda bottle over the end of the pipe until it seats against the bulge. Wrap the zip-ties around the pipe with the heads facing inward, catching the lip of the bottle. Secure the zip-ties with a hose clamp.
Step 6: Launch Trigger
LAUNCH TRIGGER; cut the top and bottom off a 2-liter soda bottle with a pair of scissors. Flatten the middle section using care not to crease it, held with painter’s tape, cut a 1-1/4 inch hole through both sides. This will hold the trigger in position until you’re ready to launch.
Drill a 3/16” in the side of a 3-inch piece of 1-1/2 inch PVC pipe. Tie piece of 10-foot string through the hole.
Step 7: Assemble Trigger Mechanism
ASSEMBLE TRIGGER MECHANISM; slide the “trigger spring” over the end of the pipe, the zip-ties and snuggly against the pipe clamp. Next, slide the “trigger” over the pipe and zip-ties. Thread the string through the holes in the “spring” and the “guide”. Conduct a test; the “spring” should hold the “trigger” up and over the ties…it should drop, allowing the ties to open up when you pull the string.
Step 8: Launch Sequence!
LAUNCH SEQUENCE! Fill the soda bottle about one-third full of water and slide onto the end of the pipe until it’s seated against the bulge. Slip the ties over the bottle’s lip and slide the trigger up over the ties.
Pressurize the launcher with either a bicycle pump or air compressor. Exercise caution not to exceed 70 psi…
3-2-1… PULL THE STRING!!!
Step 9: Trouble-Shooting
Rocket does not launch:
1. Vertical piece of PVC pipe may need to be sanded a little so that mouth of bottle slids on/off easily. Caution not to sand down seal too much...
2. As you charge launcher, water/air escaping...loosen pipe clamp, seat bottle neck against seal, reposition zip-ties, re-tighten clamp.
Step 10: Safety Precautions
Respect as you would a loaded firearm...
Recommend 70 psi...not to exceed 90...worse case scenario, rocket could explode w/a loud"BANG", possibly causing ear damage.
Launch in a large open area away from parked cars and populated areas. Designate stand-off distance of 25 feet from launcher.
Restrict payloads...no rocks!
Adult(s) only charge system. Wear eye & hearing protection. Have your back towards launcher as charging.
These are by no means all inclusive...list will grow w/experience.
Step 11: Calculating Rocket's Altitude
We calculated rockets elevation with a home-made elevation tracker for less than $.50 cents or you can purchase a commercial one at most hobby/model stores for $20...
Ours was constructed with a meter stick, protractor, some string and a weight (flat washer).
The tracker is designed to measure the angle a rocket reaches from a known distance from the launch pad and a mathematical formula. Note: More accurate if the angle is below 45 degrees.
(Tangent of Angle) X (Distance from the Launch Pad) = Rocket Altitude
I use two (2) students, a “tracker”, whose responsibility is to track the rocket from launch to the highest point of flight (apogee) and determine the angle. A “recorder”, who calculates and records the data, both are positioned 300 feet from the launch pad and at right angle to wind.
For ease, we use a table with values of the tangent for various values of angle (See Step 12 – Table of Tangent Angle).
Example: If you are 300 feet away from the pad, and measure an angle of 27 degrees, the tangent of 27 = .5
.5 X 300 = 150 feet altitude
Step 12: Table of TAN(Angle)
|Table of Angles and Their Tangents|
|Angle||Tangent||° °||Angle||Tangent||° °||Angle||Tangent|
Step 13: Rocket Data Sheet
|Mean=the sum of the values of data set, divided by number of values in a data set. Mode= most frequently occurring value in a data set|
|Median= value that occurs in middle of data set arranged in chronological order. NOTE: Data set w/odd# of values always has median…for even# of values, two middle values are averaged w/results being the median|
|Range= difference between the largest & smallest values that occur in a data set|
Step 14: Design Brief
Client: US based school supply store chain
Client: US based school supply store chain
Target Consumer: Educators, youth groups, clubs, & home-schooled, etc.
Problem Statement: Proven fact that America’s youth are falling further and further behind other countries in areas of science, technology, engineering and mathematics. To further compound matters, national, state and local governments are facing deeper and deeper budget cuts each year. How can we help classroom teacher meet these challenges and still offer a quality education with dwindling resources?
Design Statement: Develop a “turn-key” unit on rocket propulsion. Content as minimum should include topics: Newton’s 3 Laws, calculating rate & height of assent, design process. Able to achieve same comparable results of more expensive “kits” yet at a portion of the costs. Content covers topics taught in other disciplines. Materials consist of common house-hold items or off-the-shelf at local retailers.
1. 2-Liter soda bottle
2. Achieve minimum height of 20 feet
3. Successfully launch and recover payload (egg)
4. Gross Rocket Weight (GRW) 160 grams or less.
5. Inexpensive, utilize common house-hold items
Step 15: Rocket Rubric
|Design||Simple, Clean, excellent choice of materials||Simple, Clean; minor changes while constructing||Complex, major changes to original design||Too Complex; materials incompatible||Incomplete|
|Construction||GRW less than 160g||GRW less than or equal 170 grams||GRW less than or equal 180 grams||GRW less than or equal 190 grams||Fails to Complete on schedule|
|Launching||Zero Structural Failures||Minor Structural Failure; launch unaffected||Minor Structural Failure; affects launch & altitude||Major Structural Failure; barely manages to launch||Fails to Launch|
|Height||50 Feet (+)||40 Feet (+)||30 Feet (+)||Grter/Equal 20 feet||Less Than 20 Feet|
|Recovery System Function||Functions as designed||Minor malfunction; no impact on payload||Major malfunction; significant impact||Major malfunction; extensive damage to payload||System failure|
|Payload||No damage||Superficial cracks; contents undamaged||Clearly visible cracks; contents seeping||Shell broken; contents leaking||Shell destroyed; contents unrecoverable|
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