Rocket Catcher Challenge for Grades 6-8

Background Information for Teachers

This section contains a quick review for teachers of the science and concepts covered in this lesson.

Companies like SpaceX and Blue Origin are trying to make spaceflight cheaper by designing reusable rocket boosters. Instead of crashing or burning up in the atmosphere, these rockets must land gently and without damage so they can be reused. This means that engineers must carefully steer the rockets back to Earth while keeping them upright. Some rockets land upright on the ground (Figure 1), and some are even caught by towers that grab them in midair (as shown in the video)!

This engineering challenge is inspired by real-world reusable rocket landings like those shown above. Your students' goal is to build a device that can "catch" a falling rocket (a paper or cardboard tube) so it lands vertically. They can also modify the rocket and add features like fins, a nose cone, hooks, or other attachments. The farther they can drop their rockets and successfully catch them, the higher their scores. They can only use certain simple materials, like paper and tape, and each material has a "cost." Figures 2 and 3 show a few example designs. These designs are just ideas to help your students get started. They can come up with their own ideas and build something totally different!

There are many physics and engineering principles you can connect to this project. 

• This project uses the engineering design process, which includes steps like doing background research, defining criteria, and brainstorming before you start building anything. Iteration, or repeating some steps more than once, is a normal part of the engineering design process. Your students' devices might not work well on the first try, and that is OK! They can test their designs, learn from their mistakes and failures, and use that information to improve their designs.
• A falling rocket has both kinetic and potential energy. That energy does not disappear when the rocket hits the device. According to conservation of energy, it needs to go somewhere! It can transform into other forms, like acoustic energy (sound), thermal energy (heat), or elastic energy (bending, stretching, or compressing materials). 
• A falling rocket experiences aerodynamic forces. Drag acts opposite the direction of motion, and lift acts perpendicular to the direction of motion. This may be confusing at first because we normally think of lift as acting up when referring to something like a flying airplane. But in this case, since the rocket is falling down, drag acts upward (opposite the direction of motion), and lift acts sideways! A rocket's shape, including any attachments like a nose cone or fins, will influence the aerodynamic forces on it and its aerodynamic stability (whether it tends to fly straight or tumble as it falls).
• Different materials have different material properties, like density, stiffness, and strength. Different materials that rub against each other also have different coefficients of friction. Your students need to take these material properties into account when building their devices. A device that is too weak may break when the rocket crashes into it. A design that is too springy may cause the rocket to bounce back out after landing. 

Additional Background Links

• Science Buddies staff (n.d.). Engineering Design Process. Retrieved October 10th, 2024.
• Dunn, M. (2024, October 13). In an engineering feat, mechanical SpaceX arms catch Starship rocket booster back at the launch pad. Associated Press. Retrieved October 29th, 2024
• Blue Origin (2024, May 19). Blue Origin Completes 25th Mission to Space with Six Crew Onboard. Retrieved November 22, 2024

Prep Work (15 minutes)

• Gather all the construction materials in a central location for students.
• Print the student worksheet (one for each student).
• Print the team entry information sheet (one for each team).
• Have your students watch the introductory video before they begin.
• Set up testing areas for students. You may need to move the class to a gymnasium or playground to test higher fall distances.
• You may wish to set up a distance-measuring station (for example, taping a tape measure to the wall) so students can easily measure distances when testing.

Engage (15 minutes)

Introduce the challenge to your students. Explain that their main goal is to build a rocket-catching device that will catch a falling rocket so it lands vertically. Show your students the introductory video if they have not watched it already. Then, go over the student worksheet and the contest rules (also included in the student worksheet):

Explore (1-2 hours)

1. Design. Before they start building anything, have each student each draw two ideas for a rocket-catching device and corresponding rocket design on their worksheet. Remind them to think about the materials they are allowed to use and how they can use those materials to build. They should also think about how the final score will be calculated. It depends on both the fall distance of the rocket and the amount of materials they use.
2. Compare. After drawing two designs, have each student work independently to compare their first and second design and think about which design would work better for the challenge.
3. Share. Have students form groups and share their designs with other students in their group. Students should compare the designs and discuss which one(s) would score best for the contest. Make sure students evaluate the designs objectively using specific criteria (e.g., the materials cost for each design) rather than subjective criteria like appearance. Each group should select a single design to build. Designs can include a combination of ideas from multiple students.
4. Build. After agreeing on a single design to build, students should start building it. They may need to make changes or adjustments as they build. This is OK.
5. Test. Students should test their devices from low start heights initially. The students can just stand on the floor, hold out their arms, and drop the rockets. Emphasize that it is OK if the device does not work on the first try (or second, or third...)! This is why engineers test things, so they can fix them and make improvements. They should make observations about what works (or does not work) while testing and think about how they can improve their design.
6. Iterate. Based on their observations, students should try to improve their design so they can increase their score. This can include dropping the rocket from a higher location but also efficient use of materials to decrease the materials cost.
7. Re-test. After making improvements, students should re-test their devices. Allow them to continue iterating, improving, and re-testing as time allows.

Reflect (30 minutes)

Once all groups have finished building their devices, have a class-wide competition to calculate official scores. For each team:

1. Measure the fall distance. As shown in Figure 4, this is the vertical distance between the topmost point of the rocket-catching device and the bottom of the rocket at the start. Students should start with the rocket at the highest location they have successfully tested so far. There are two ways to find this distance:
   1. Measure the distance directly using a tape measure or meter stick.
   2. If you find it easier to measure from the floor, then:
      1. Measure the rocket's start height (the distance from the floor to the bottom of the rocket).
      2. Measure the rocket-catching device's height (the distance from the floor to the topmost point of the device).
      3. Subtract the device height from the rocket start height to get the fall distance.
2. Let the students drop the rocket, making sure they follow all of the rules listed above.
3. Measure the rocket's end height (from the ground to the lowest point on the rocket, including anything attached to the rocket's body) and make sure it is at least 10 cm.
4. Measure the rocket's landing angle as shown in Figures 5 and 6.
   1. Cut a piece of paper into a square.
   2. Fold the paper in half diagonally to form a 45 degree angle.
   3. Hold the paper up to your rocket, with one of the short edges horizontal (parallel to the ground) and the other short edge vertical (perpendicular to the ground).
   4. Compare the angle of your rocket's body to the angle of the long (diagonal) edge of the triangle. The rocket's body should be tilted more "vertical" than the long edge of the triangle (greater than 45 degrees).
5. If the test violated any of the rules, the students must start over and do a new test.
6. Once the students have achieved two successful drops in a row from the same height, they can record their fall distance in the worksheet and calculate their score. If time allows, they can try again to get a higher score.

Scoring

Your score is then calculated using this equation:

Equation 1:   $\: Score\; = fall \; distance \;in\; centimeters - total\;materials \;cost$

A scoring worksheet and scoring spreadsheet are available to help you calculate your score. You can also read the following written instructions or watch the video with an example calculation.

1. If you measured your distances in inches, convert them to centimeters by multiplying by 2.54. For example, if your fall distance was 40 inches, that is 40×2.54 = 101.6 cm.
2. Count the total number of each material item that you used.
   1. Material quantities are not prorated. For example, even if you only use one quarter of a sheet of paper, you must count the entire sheet.
   2. Remember to count materials used for both your rocket-catching device and additions to your rocket's body.
   3. If you used a rolled sheet of paper for your rocket's body instead of paper towel or toilet paper tubes, that sheet of paper does not count toward your total.
   4. Only count materials used in your final design for both your rocket and rocket-catching device. Materials used for earlier prototypes do not count.
3. For each material, multiply the quantity by the point cost for that material to calculate the subtotal for that material. For example, if you used 6 sheets of paper, which are worth 3 points each, that is 6×3=18 points. The material cost is 18.
4. Add up all of the subtotals to get your total materials cost. For example, a design that used the sheet of cardboard, 6 sheets of paper, tape, 2 paper clips, and 70 cm of string would have the following materials cost:
   1. Tape is "free" (0 points)
   2. 1 piece of cardboard = 5 points
   3. 6 sheets of paper × 3 points each = 18 points
   4. 2 paper clips × 1 point each = 2 points
   5. 70 cm of string:
      1. First, round up to the nearest 100 cm, so 70 cm rounds to 100 cm.
      2. 100 cm × 2 points per 100 cm = 2 points
   6. Total = 5 + 18 + 2 + 2 = 27 points
5. Plug your fall distance in centimeters and total materials cost into Equation 1 to calculate your score. For the design in the example above, with a fall distance of 101.6 cm and a total materials cost of 27 points, the score is 101.6 - 27 = 74.6.
6. Round your score to the nearest whole number. The score of 74.6 would round up to 75. If the score was 74.49, that would round down to a final score of 74. The score submission form will not accept decimals.

Assess

• Collect your students' worksheets and use them to assess how they worked through the design process.
• Ask each group to give an oral presentation about their design, including the engineering challenges they faced and how they addressed them.

Lesson Plan Variations

Did your students enjoy this type of hands-on project? Check out the other Engineering Challenges and try them in your classroom!