Rockets: Creating Models and Testing Solutions

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Objective

Students will be able to utilize the design process to design a solution to a problem based on Newton's Laws.

Big Idea

It's not rocket science.....oh wait, it is! Students use the design process to create a water powered bottle rocket that can launch hundreds of feet into the air!

Introduction and Connection to the NGSS and Common Core

The first part of this project takes students through the design process including research, sketching, decision matrices, and writing design proposals. (Check out Rockets: Research and Design Proposals for more information.)  This lesson continues the design/build process and includes 3-dimensional modeling, constructing, testing, and revising design solutions.  Completion of this lesson will take multiple days.

This lesson is designed to address the following NGSS and Common Core Standards:

MS-PS2-1      Apply Newton’s Third Law to design a solution to a problem involving the motion of two colliding objects.

MS-PS2-2      Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object

CCSS.ELA-LITERACY.RST.6-8.9  Compare and contrast the information gained from experiments, simulations, video, or multimedia sources with that gained from reading a text on the same topic.

CCSS.ELA-LITERACY.WHST.6-8.9  Draw evidence from informational texts to support analysis, reflection, and research.

Scientific and Engineering Practices:

2 Developing and Using Models     Students should be able to develop and/or use a model to predict and/or describe phenomena. 

6 Constructing Explanations and Designing Solutions  

  • Apply scientific reasoning to show why the data or evidence is adequate for the explanation or conclusion.
  • Apply scientific ideas or principles to design, construct, and/or test a design of an object, tool, process or system.
  • Undertake a design project, engaging in the design cycle, to construct and/or implement a solution that meets specific design criteria and constraints.
  • Optimize performance of a design by prioritizing criteria, making tradeoffs, testing, revising, and re-testing. 

7 Engaging in Argument from Evidence    Construct, use, and/or present an oral and written argument supported by empirical evidence and scientific reasoning to support or refute an explanation or a model for a phenomenon or a solution to a problem. 

Crosscutting Concepts:

Systems and System Models: A system is an organized group of related objects or components; models can be used for understanding and predicting the behavior of systems.

Structure and Function  Structures can be designed to serve particular functions by taking into account properties of different materials, and how materials can be shaped and used.

Connecting to the Essential Question: What are you supposed to learn today?

5 minutes

In my classroom, I begin each class by asking the question, "What are you going to learn today?". Students respond by referencing the Essential Question, "How can I demonstrate science and engineering literacy?". This EQ is located on their Literacy Unit Plan as well as on the front board of my classroom.

Then, I have students rank themselves on each of the skills included in the unit plan.  Students rank themselves on a scale of 1 to 4 (4 being mastery). Students continue to update these scores over the course of the unit. I emphasize  that it is ok not to be at a "4". Learning is about growth! We will use this starting point to track the growth in their learning.

Notice in the student work below, that the student updates his scores over the course of the unit as he grows in his level of mastery.

I explain that the focus of the lessons over the next days are Skills 2 and 3. Students will be using the design process to design and launch a rocket as well as create a 3-dimensional model of their rocket in an Auto-Cad/engineering software.

Creating 3-dimensional Models: AutoCad Inventor

60 minutes

It is important to note that prior to this point in the lesson, students have researched, sketched, ranked design options based on criteria and written a design proposal (Rockets: Research and Design Proposals).

The engineering process is something that is a focus of the NGSS. In order to bring this engineering connection to real world engineering, I have my students design their rockets in a 3-dimensional Modeling Software, just as a "real" engineer might. The product I use is Autodesk Inventor, but there are other 3D CAD programs available. I am fortunate to work in a district that purchased this software through a grant that we wrote to General Motors. Autodesk Inventor has a 30 day free trial that you could have your students use as well if you are not able to purchase the software.  

I provide the students with these "Rocket Directions" and ask the students to create a 3D model of their rocket that is to scale in Inventor. Some students are great with written directions. Others, however, need verbal and visual support. I have found that when using technology, differentiation is key. Some students are ready to move quickly, others need time to process. I created a series of video directions that students can watch and listen to for each point of their rocket project. I purchased some headphone splitters from Amazon so that both partners can listen to the directions with headphones at the same time.

This link will take you to a folder that provides instructional videos for each piece of the rock as well as it's assembly in the Inventor program.  

**At this point in the year, my students have used Autodesk Inventor through a program called Project Lead the Way (PLTW). The program is worth looking into for your school! But, that doesn't mean you can't do this without PLTW. What I would suggest is that you take some time going over the basics of the program with your students before having them complete your rocket. I realize it might be scary to think you would have to teach your students an engineering software - but it's worth it!  Through the videos I have given you access to and the free tutorials that are out there online, it is worth it for students to get this experience!

Below are some 3-dimensional computer models, along with the student's complete prototype they constructed. Note that the prototype is built based on the model. (The next section includes information about how to actually build the physical rocket.)

 

As students begin to follow the "Rocket Directions", a frequent question that is asked is, "What should I dimension my (cone/fin/etc.)?". The key about making this 3-dimensional model is that it is to scale. So, the answer is, "Choose a dimension that fits your sketch.  You might want to get a ruler out and measure the bottle and get a feel for how big you want your rocket to be." I find that students do not have a great sense of measurement. Actually having them get out the ruler and the bottle is necessary for them to picture how tall they want their fins/nose/etc. to be.

Rocket Construction

90 minutes

Once students have completed their research, design proposal (from this lesson), and computer model, students are able to begin actual construction of their rockets.

Materials Required (per group):

  • 2 two-liter bottles (1 liter and 3 liter bottles will not fit the launcher)
  • Duct Tape 
  • Hot glue guns/hot glue sticks
  • Clay
  • File Folders
  • Cardboard
  • Any extra materials students chose (Some students use tennis balls, CDs, etc)

**I have the students bring in their own two liter bottles and duct tape. At the end of the project, I ask students to donate their left over duct tape.  As a result, each year I have a bin of community tape that students that cannot bring in duct tape can use. Your first year, you may want to buy some materials, particularly duct tape, for students that do not bring it in. I provide the hot glue and clay. I use about 1.5 bags of the mini glue sticks in the process. I use about 64 oz of clay.

The key to this procedure is that they need to create all of the "pieces" of their rocket first before putting anything together. In order to accurately place the center of mass and center of pressure, all parts need to be put together at the end!

Procedure:

1.  Completely cover one two-liter bottle in duct tape.  Go slow!  It is worth it to take your time and make the tape completely smooth. The entire center part of the bottle should be covered, except for the "bumpy bottom part" of the bottle. It will be covered by the 2nd 2-liter bottle (see the picture below left). The tape should go down the neck of the bottle, but should not cover or touch the "lip" of the nozzle. This will get in the way of the rocket attaching to the launcher (see the picture below right). It is key that there are NO holes or cuts made to this bottle.

2. Cut the other two liter bottle in "half". I say "half" because it might really be 1/4 or 3/4 depending on how tall the students want the rocket. The method that has given me most success with this is to use a razor blade or box cutter and poke a hole in the bottle and then use scissors to cut the the remainder. This part of the bottle will fit on top of the "bumpy bottom part" of the full two liter bottle. Duct tape the cut bottle half (typically the top half).

3.  Draw and cut out the fins from cardboard. Save all of the empty copy paper boxes from your school over the course of the year! They make great fins! Duct tape each fin smoothly.

4.  Make the nose cone. To make a nose cone follow these steps:

a.  Trace a circle and draw a radius on a file folder.

b.  Cut the circle and the radius line.

c. Fold the cone into the desired shape. (If students want a rounded top instead of a pointy top, simply cut off the tip of the "party hat" and add clay to make a rounded top.)

d.  Duct tape completely and smoothly.

Assembly Procedure:

1.  Duct tape the nose cone to the "half" two liter bottle.

2.  Hot glue the fins onto the full two liter bottle.  (Some will need a reminder to look back at their sketch to remember where they wanted to place their fins on their bottle.  Also, I always have students mistakenly put the fins on upside down.  The mouth of the full two liter bottle is the BOTTOM of the rocket!)

3.  Place clay in the half two liter bottle until the center of mass is in the appropriate place. (The rocket should balance above the top of the fins, almost where the half and full bottle will end up connecting.  To start, the rocket will be bottom heavy.  Adding clay moves the center of mass towards the front.)  It is important for students to consider how they put the clay in the half bottle.  If they simply put it as a ball inside, it will bounce around inside and make the rocket unstable in flight.  So, most students "smush" it to the sides of the bottle.  When doing this it is important to make sure to spread the clay evenly to prevent the rocket being "lopsided".

4.  When, and only when, the rocket balances at the right place, duct tape the half two liter to the whole two liter bottle.

*Inevitably, you will have students attach the half bottle to the full bottle without adding clay and adjusting the center mass.  It is so important that they remove the tape and add the clay before launch day.

Launch Day: Testing Prototypes

75 minutes

Launch day is here! There is a lot of build up for this much anticipated day! Being organized and having a plan will be very important.

First, safety is so important. These rockets can fly hundreds and hundreds of feet into the air if done effectively.  Have your students wear goggles! You never know if a fin might fall off the rocket in flight and fall to the sky. Make sure students stand a safe distance back from the launcher.  And, set up your launch site away from any buildings. Although made out of cardboard, I have literally had rockets go through the roof of a building! Strategically plan your launch site where it will not be able to hit any buildings, roads, or vehicles.

Air compressors work way better than bicycle pumps - and they will save your strength as well! For years I used a bicycle pump with rocket launches. They worked well enough, but using an electric air compressor took launches to a whole new level. There are a couple of options for this. One, check in with your woods/shop teacher. They may have an air compressor that you could use. Cheaper than buying your own air compressor, you could just buy extra length of hose to add to the shop air compressor to get you away from the building. Second, you could purchase or borrow an air compressor "on wheels". This has proven to be the best option for me. This way, I can wheel it far away from the buildings and out to the baseball fields out of danger.  

On the day of the set up, allow time before your first class to set up your launch site. And, I strongly encourage you to launch a couple practice rockets so that you can get a lay of the land and the trajectory the rockets could take. (You might want to check your prevailing winds, as well as the wind direction and speed on launch day.)

It is important to be efficient so you can get the launches in during a class period. I fortunately have long 70 minute class periods. In this amount of time, I can have my students launch their rockets twice. However, if the initial minutes in class are "wasted" you may run out of time.

When students arrive, here are the things they need to do:

1.  Fill an empty two liter bottle half way with water. Use a funnel to pour the water into the rocket.  Close the cap.

2.  Fill the empty two liter bottle half way with water again (if you plan to launch twice).

3.  Bring extra duct tape. (If you are going to let students launch twice, they will need some duct tape to repair damage caused by the first launch.)

4.  Bring a timer. (I use a cell phone to time the length the rockets are in the air. You can buy devices that will measure the height of the rockets; however, I have found them hard to work and collect accurate data with.)

Wait to give directions on how to work the launcher until you are outside. If you try to give the directions inside the classroom, students are so excited about launching that they may not remember by the time you get out to the launch site. I always have the students line up and I give each group a number. This way, I can keep track of how many groups I need to get through and which students come next. It will save you from the, "Can we go next?" question as well.

I emphasize that students must all turn and face all rocket launches. We count down from 5 seconds as a class for each launch. For safety, students need to be ready to move if the rocket should take an odd path. If students are talking or have their backs to the launcher, they will not be able to see the rocket's path.

The launches are awesome!!!!!!!!  Enjoy.  This will be a highlight of their year!

 

Closure

5 minutes

One important aspect of the design process is the idea that engineers are constantly improving their designs and sharing ideas.  After watching all of the successful rockets, I have each group brainstorm the successful aspects of their rockets and the aspects they would improve if they were given the opportunity to build a rocket again. Then, each group shares out to the whole.

Don't skip this! Make sure students are aware that the this reflection is a crucial part of this lesson. Below are some sentence frames that might help your students have a quality discussion after their launch.

"I noticed a pattern that the rockets that were the most successful had ________________________ in common.  My rocket ________________________.  So, I would adjust ____________________ if we were to redesign."

 

"My rocket was very successful.  However, if I were to try this again, one aspect I might experiment with changing is __________________ because ___________________."