I've seen all sorts of Water Bottle Rockets on Instructables and while surfing the web but I thought an Instructable with the step-by-step process of building a whole bunch of them with a class of grade six kids would be good. Each step in the Instructable will be a day in the class. At the top of each day you'll find a list of tools and materials. Just follow through a day in advance and you'll have kids learning so much more than anyone bargained for.

This rocket is based on the usual 2 liter pop bottle you find at grocery stores. You add water, pressurized air and using these instructions you'll get height that you and your students will not believe. AND to make it interesting... we have a passenger... the Eggstronaut, which is an egg that if survives will award extra marks to the team.

You'll need the basic materials listed below as well as a launcher... Here's a link to a commercial version... i've added a couple of pics of it below as well.

http://shop.pitsco.com/store/detail.aspx?ID=1179&bhcp=1

I will design and build a launcher and do an instructable in a few weeks when I get a chance. I have seen all sorts of designs but I'm hoping to come up with something as effective as the commercial one above....
A good hand pump works well but a compressor REALLY makes life easy... you can max the pressure like crazy, too.

Learning Objectives:

-The students will learn and apply Newtons Second Law of Motion in a way that makes sense to them...
"The more massive an object is... the more force it takes to accelerate it" or you could say...
"Heavy stuff takes more force to move"

-The students will learn and apply the basic principles of Newtons Third Law of Motion...
"To every action there is an equal and opposite reaction" or you could say...
"if you push something it will push back"

-The students will understand Newtons First Law of Motion...
"F=MA" or to make it so I can understand...
"stuff that is sitting there will stay that way unless something happens to it. Once things start moving they tend to keep moving until something happens to change how it is moving"

-Students will learn to tell the difference between MASS and SIZE

-By building a simple Rocket the students will understand these laws in a way that makes sense to them AND they will learn to think creatively, design and problem solve while building a basic design.

-The students will learn to use basic tools to construct a working project.

Tools and Materials:
-scissors
-Hot glue gun
-duct tape
-X-Acto or Olfa mat knife
-2 liter pop bottles (NOT water bottles!) get at least 2 of them
-Cardboard or coroplast (the stuff cheap signs are made of)
-batting, foam, paper strips.... whatever you find for the Eggstronaut...
-egg

Vocabulary:
-Pressurizing
-Ratio
-Symmetrical
-Hypotenuse
-Scale (as in drawing to scale)

I'll also provide a marking sheet at the end so you can use it in your class.
Right, then. Lets get started...

Step 1: Day 1. the Introduction

Tools and Materials:
-a couple of 2 liter bottles
-Big sheets of paper. (i cut stuff off a roll from the art guys...)
-Metersticks (yardsticks for the people south of me ) :-)
-Lots of pencils.
-An egg

-a computer with examples of water-bottle rockets from the web. check out youtube... I use a TV attached to my ancient computer... not impressive but works fine...

After you show the kids examples from the web they will be hard to hold back. Its pretty cool. I start asking questions like these:

-How does it fly?
-Why are some short and some long?
-Some rockets have 2 fins, some 6... why?
-What about the fin size?

I cover each of these points on the board. What you want to coax out of them is:

The rockets fly by pressurizing air with water. (more on the water next day) This is important because the "Booster Bottle" which is pressurized ****MUST**** be a bottle for carbonated drinks and MUST MUST NOT be punctured or cut AT ALL. It will explode if otherwise. I've done it and it is really scary. Funny but scary.

Long rockets (double length) work best. You can chat about what RATIO is now... Suggest methods of lengthening the rocket. (tubes, extra bottles)

Fins that are Symmetrical with 2-4 are best. Keep them small... explain that the rockets explode off at more than 100kph and large fins will rip off. A good size is a triangle with Hypotenuse of 3-7 inches and bottom edge of 1-3 inches is good.

Now introduce the EGGSTRONAUT. Explain that if the passenger survives they will get extra marks. They love this. Go over padding and protection if you want but i find the kids come up with the most amazing ideas... better than mine! My only stipulation is that they have to make an escape hatch that can be used to insert and remove the Eggstronaut on the field.

Once the kids are ready i break them into groups of 2 or 3. Don't do 4... you always get at least one kid who is left in the cold. I pull out the paper and teach them about drawing objects to scale on the paper. You can trace out a bottle or two which helps them visualize it.

Spend the remaining time working on design. You'll get a couple groups that finish the drawing in minutes... just send them back with revisions... measurements... notes... whatever you can make up :-) Make sure they draw the fins to size and they are being realistic about the egg and how it will get into the hatch.

Spend some time discussing materials. I ask the kids to bring bottles, long cardboard tubes, cardboard, coroplast and any packing material they will need. Its up to you. I supply basic tools and tape to build the rocket with.

Step 2: Day 2... Building and Newton #2 and #3

Tools and Materials:
-Duct Tape
-Hot glue and Hot Glue guns (not required...see below)
-2 Liter bottles
-Cardboard, Coroplast
-scissors, x-actos, mat knifes...etc
-Material for batting
-2 skateboards (if you can find them...)

The kids are ready to build but first you can do a fun demo. The first law i teach about is Newtons 2nd Law...

"The more massive an object is... the more force it takes to accelerate it" or you could say...
"Heavy stuff takes more force to move"

I like to demonstrate this by pulling up the smallest kid in the class. I pull out 2 skateboards.. facing each other and about 2 feet apart. I put the student on one skateboard and i stand on the other. I'm not a big guy but usually the size discrepancy is pretty obvious. I longboard as a hobby but i act like I've never stood on one. the kids like that... I ask the student to hold out both hands in front than i do the same. I ask the class what would happen if we pushed our hands together really hard. Of course the kids know what happens so i gently push on the hands of the student. Its amazing how far a kid will roll. I won't move more than a couple of inches.

I get the kids to notice 2 things.
-The person with less mass moved further
-The person with more mass actually DID move a bit.

Newtons 2nd law relates to the idea that more massive objects will take more energy to accelerate, or move. The person with less mass moved more because it takes less energy to move them.

The other part of the demo is that the more massive person still moved... This is explained by Newtons 3rd law which says:

"To every action there is an equal and opposite reaction" or you could say...
"if you push something it will push back"

The kids notice that i move as well. You could explain the idea that every time objects move each other BOTH have the same force being pushed on them. More massive objects don't MOVE as much but they still have the same energy exerted on them. This is also a good explanation for why we add water to the bottle. The water being pushed out from the bottle has more mass than just air so it pushes against the bottle harder which forces the bottle up with more force. You can tie this into Newtons 2nd law as well if the kids are still engaged at this point.

Now you can start BUILDING STUFF

Pull out the drawings, gather the materials and demonstrate a couple of skills...

-Stacking bottles for height.
Show how to cut a bottle safely with a blade. keep the cap on when starting... makes it easier. I cut a bottle open about 4 inches up from the bottom than show how they can stack. Its up to you if you want the kids to use blades. It worries me so i ask the kids to use scissors AFTER i start the cut for them.

-Taping
I give out a meter at a time. Kids will use a whole roll if left to it. I demonstrate how much tougher and more accurate it is to use 4" strips of tape placed lengthwise. i do one side, line up for symmetry than tape the other.

-Using drawings as patterns
I ask the kids to use the drawings as a pattern to cut out the fins and other parts... I find a scroll saw works great on cardboard and coroplast.

-Attaching stuff to the bottles
Use sandpaper to scuff up wherever they want to attach things. Hot glue works well but i find that it is used WAY too much and kids burn themselves. I find tape works well. The fins can also be taped on with care.

Remind the kids about a couple of things...They forget that the egg has to go in and out easily. I cut a hatch in the top bottle. Remind the students that they MUST NOT puncture the BOOSTER BOTTLE at all. Usually one team will forget this. You will also get at least one team that will forget that the booster bottle goes TOP DOWN and they will tape the fins on upside down. Make sure they understand SYMMETRY and that the rockets work really well if they are about 2 times the length of a bottle.

Step 3: Day 3 Building and Newton #1

Tools and Materials
-Same as last class...

Today i like to start with another bit of theory. I verbally test the class to make sure they remember Newtons #1and 2 Laws than i introduce the 1st law, which goes like this...

"F=MA" or to make it so I can understand...
"stuff that is sitting there will stay that way unless something happens to it. Once things start moving they tend to keep moving until something happens to change how it is moving"

I ask What would happen to the student with less mass if NOTHING was slowing them down. The students usually know that the kid would keep moving... We talk a bit about why the student stops... friction, mainly...

Now I ask them if both the small kid and myself started moving at the same speed who would go farther. They know intuitively that I would... but why? This is where the "M" in the 1st law comes in. Explain that FORCE ("F") would increase if the MASS ("M") increased... Show them simple examples on the board.

So how does this relate to the rockets? I explain that a slightly heavier rocket will go further. A WAY heavier rocket will not move at all of course. I suggest that weight in the nose can be beneficial BUT can be used ONLY if it is not sharp or too heavy or potentially dangerous. A ziplock of sand works really well. You can tell the kids this but they come up with great stuff on their own... One team used peanut butter which is heavy and also worked well as a protectant for the egg...

I've included a series of shots that i use to demonstrate the process to the kids... The steps show how you can add two bottles together with just a bit of duct tape. You can also use the duct tape to attach some fins. Notice also that i added water to the top (non-booster bottle)

I have kids work out plans for parachutes sometimes. They are pretty exciting for kids and sometimes work but need to be carefully planned. Most kids get a plastic bag, tape it to the nose and hope it will work. It won't. If you want to explore the idea of parachutes i suggest using plastic bags cut open and tethered properly. I've had students use a bottle cut in half with the egg attached to the top. The bottle rests on the booster rocket but is not attached. When the rocket is accelerating the egg bottle remains in place. When the rocket starts to slow the air pushes the bottle off and the parachute opens. I think i'll try it this time. If i do i will elaborate on it more and append this instructable.

Step 4: Day 4 THE LAUNCH

I make sure the students understand the idea of adding water as it relates to the laws of motion. It seems that the ideal amount of water is about 1/3 of the bottle but encourage the kids to experiment.

I bring out the Eggstronauts with much fanfare and excitement... its fun to turn it into a goofy event. The teams submit the rocket and eggstronaut hatch for entry. Once the water is added and the egg in place we launch. Make sure the kids are well back. sometimes the rockets go sideways. The most concern for safety comes when a team builds a really accurate rocket. This means the rocket is going to come down pretty much where everyone is standing. If this happens i get the kids to all make sure they have a back to the wall of the school... This really cuts down on the danger level. Do not let kids run after the rocket until it lands. They have a really solid punch... sometimes they leave holes in the ground.

The biggest concern for me has turned out to be the least. I was worried at first about the bottles exploding. After accidentally exploding a water bottle and a compromised pop bottle on two occasions I can tell you the only danger is the embarrassment of needing to clean your shorts afterward. It explodes with a very impressive gunshot that scared the heck out of me both times. My guess is that the material is so light it has very little momentum and doesn't cause damage other than evaporating whatever is attached to the bottle. Its pretty impressive!

I give a basic mark related to the design... it needs to look like the rocket when finished. I also give marks for accurate flight and height and a bonus mark for eggstronaut survival.

Try this project! I've done it for years and i have 20 year old ex-students come back and tell me they learned more with the rockets than half their science classes. As a shop teacher there really is no greater compliment.

:-)

-stu