Overview

To complete this lesson, students build the tallest freestanding structure they can that will support a marshmallow for at least 15 seconds. Though a marshmallow might not seem like a significant mass to support, students will find the challenge when they are constrained to using spaghetti sticks and tape. The same forces, like gravity and wind, that engineers have to take into consideration when working on Deep Space Network antennas come into play when building a spaghetti structure. In small groups, students will quickly brainstorm their ideas and discuss strengths and weaknesses. Once the group selects a design, they will need to build, test and redesign to make sure it is stable and can support the marshmallow, all within the time limit of 18 minutes.

Materials

Uncooked, thick spaghetti

Marshmallows (full size)

Brown lunch sacks (optional)

100 cm (1 m) of masking tape

Scissors (to cut spaghetti)

Science journal

Pencil

Meter stick or metric tape measure

Stopwatch (consider using an online version that may be displayed for the whole class to view during the activity)

Management

• This activity is meant to be an experiential introduction to the engineering design process and not a formal engineering project. Thus, quick student sketches are encouraged but formal plans are not required. Consider doing this activity with a class prior to introducing the engineering design process, then discuss how their natural thought and action processes are reflected in the formal engineering design process.


• Before class, assemble materials for each group in a brown lunch sack for ease of distribution and disguise until the challenge is revealed. 


• In each lunch sack place 20 strands of spaghetti and one full-size marshmallow.


• Place 1-meter strips of tape around the room for easy access - on windows or any adhesive-proof surface.


• Display an online stopwatch on the class projection system and set it to 18 minutes.


• Consider playing some upbeat music during the 18-minute challenge.


• Note: this challenge has been well researched and 18 minutes has been determined to be the optimal time for completion. More time has been showed to decrease team member involvement.


• Teams may use less than 18 minutes and have the teacher measure the height of their structure at any point prior to the 18-minute mark.

Background

• Many forces are at work on towers. Gravity and the dead load of the tower push down; the ground pushes back up and small air movements push from the side. A foundation distributes the load into the surrounding ground material and can help balance the sideways wind force. The size of the foundation depends on the strength of the supporting ground. A foundation placed in rock can be smaller than a foundation placed in sand or mud.


• Key Concepts


• Bending: Combination of forces that causes one part of a material to be in compression and another part to be in tension


• Compression: Force that squeezes material together


• Design Process: Identify the problem, brainstorm, design, build, test, evaluate, share, redesign and rebuild


• Load-bearing members: To support or strengthen a roof, bridge or other elevated structure with a network of beams and bars


• Neutral axis: An imaginary plane that runs through the middle of a material under bending, at which zero stress is experienced


• Tension: A force that pulls material apart


• Truss: Support something with a structure


• Watch the TED talk "Build a Tower, Build a Team," in which designer Tom Wujec describes how the activity is a revealing lesson in collaboration.
  

Procedures

1. Organize students into small groups. Be sure each team has some blank paper and pencils available for sketching.


2. Introduce the materials and the challenge. Emphasize that the structure must support the entire marshmallow for at least 15 seconds.


3. Tell students they will have 18 minutes to complete the task. 
   


4. Start the timer (and the music, if available) and announce, "Go!"


5. Call out various time points such as the half-way point at 9 minutes, 5 minutes left, 2 minutes left, etc.


6. At the end of the 18 minutes (or as student teams finish prior to the clock running out), measure and record the height of the structures. 


7. Have students share their models with the class and explain their design process - did they discuss among the group members first? Sketch? What structures did they try?


8. Show students the engineering design process graphic and help them to see that their natural thought and design process followed this in many cases. 
9. Have students make an entry in their science journal about this activity. Have them sketch their final result, regardless of whether it succeeded or failed, and discuss success and failure points. Have them sketch another design that they think might perform better if they had the challenge to do over again.

Discussion

• What did you contribute to your team?
  (Answers will vary.)


• What do you think engineers have to consider when they suggest which materials would be best for a certain structure?
  The strength of the materials, the types of forces acting on the structure, etc.


• What forces cause the tower to tip over?
  Buildings fail when engineers do not use designs and materials that are strong enough to resist compressive and tensile forces


• What features of the design helped your tower to reach new heights?
  (Answers will vary.)


• After testing what changes did you make to your tower?
  (Answers will vary.)


• Engineers early ideas rarely work out perfectly. How does testing help improve your design?
  Testing helps you see what works and what doesn’t. Knowing this lets you improve a design by fixing the things that aren’t working well or could work better


• What did you learn from watching others?
  (Answers will vary.)

Assessment

• Have the students demonstrate their towers structural strength and talk about how they solved their problems that came up during the design process.


• Ask about compression and tension forces as they relate to the strength of their structures.


• Journals should present measurements and design sketches.

Extensions

• Build a paper model of the International Space Station


• Build toothpick trusses to learn about International Space Station structures


• Engage your students in the Spacecraft Structures Engineering Design Challenge