Engineering Challenges for Kids: How to Design, Test, and Improve Hands‑On Projects

Engineering challenges are short, goal‑oriented projects that ask children to create a device, test whether it works, and then improve it. By framing the activity around a clear problem—such as getting a marble onto a target or building a rover that moves across a floor—kids practice the full engineering design cycle while using everyday materials.

Why Use Engineering Challenges?

Challenges give structure to open‑ended play. They provide:

• Purpose. A specific goal (e.g., “launch a marble into a cup”) focuses curiosity.
• Iteration. Repeated testing teaches that failure is a step toward improvement.
• Measurable evidence. Simple data (distance traveled, time taken) lets children see real progress.
• Collaboration. Teams can divide roles—designer, builder, tester—mirroring real engineering teams.

Programs such as the annual Science Buddies Engineering Challenge and NASA’s JPL classroom activities illustrate how low‑cost challenges can be run in any classroom or home setting¹².

The Engineering Design Process (EDP)

All reputable challenges rely on the same eight‑step cycle, often visualized as a looping diagram:

1. Ask: Define the problem and constraints.
2. Imagine: Brainstorm many possible solutions.
3. Plan: Choose one idea, sketch it, and list needed materials.
4. Create: Build the prototype.
5. Test: Run experiments, record results.
6. Refine: Identify weaknesses and redesign.
7. Share: Communicate the solution to others.
8. Repeat: Return to any earlier step as needed.

NASA’s elementary engineering packet presents these steps in child‑friendly language and stresses the importance of asking good questions and sharing results³.

Choosing a Challenge That Fits Your Situation

Before diving in, consider four practical dimensions: materials, age range, time required, and supervision level. The table below summarizes three popular, free‑resource challenges and how they align with those dimensions.

Pick a challenge that matches the materials you have on hand and the time you can devote in a single session or a short series of sessions.

Worked Example 1: Science Buddies Ball‑Run Challenge (2026)

The 2026 Ball‑Run challenge asks teams to build a pathway that guides a marble from a start point to a target zone using only cardboard tubes, tape, and optional rubber bands. The problem statement (from the official challenge page) reads: “Design a contraption that can transport a marble over a distance of at least 30 cm without it falling off the track.”¹

Materials

• Cardboard tubes (toilet‑paper or paper‑towel rolls)
• Masking tape or painter’s tape
• Rubber bands (optional for added tension)
• Marbles (one per team)
• Scissors (adult use only)

Step‑by‑Step Workflow

1. Ask. Write the exact goal on a sheet: distance ≥ 30 cm, marble must stay on the track.
2. Imagine. Sketch three different track shapes (straight, zig‑zag, loop).
3. Plan. Choose the zig‑zag design because it uses fewer tubes and can be anchored with tape.
4. Create. Cut tubes to 10 cm lengths, tape them together at 90° angles, and secure the ends to a flat cardboard base.
5. Test. Place the marble at the start, release, and measure how far it travels before falling.
6. Refine. If the marble falls at the first corner, add a small rubber‑band “spring” to push it forward, or widen the tube diameter.
7. Share. Record the final distance, take a photo of the track, and present the improvement story to the class.

Recording Data

Use a simple table to capture each trial:

Repeat at least three trials per configuration to see which changes are most effective.

Worked Example 2: NASA JPL “On Target” Cup Zip‑Line

In this activity, children modify a paper cup so that, when it slides down a zip line, it releases a marble onto a drawn target. The challenge integrates geometry (angle of release) and friction concepts.²

Materials

• 1 medium‑size paper cup
• 1 marble
• ≈ 9 ft (3 m) of smooth line (fishing line or kite string)
• 1 paper clip
• Masking tape
• Scissors (adult)
• Target drawn on a sheet of paper

Procedure Overview

1. Ask. Goal: “Drop the marble onto the target from the zip line with an accuracy of ±2 cm.”
2. Imagine. Ideas include cutting a hole in the cup, attaching a string pull‑trigger, or tilting the cup.
3. Plan. Choose the “tilt‑trigger” design: attach a paper clip to the cup rim and a short length of string that pulls the clip out of a notch when the cup reaches the low point.
4. Create. Tape the string to the cup, secure the clip, and set up the line at a 30° incline.
5. Test. Release the cup, observe where the marble lands, and measure the distance from the centre of the target.
6. Refine. Adjust the string length or the notch position to change the release timing.
7. Share. Create a short poster showing the original and refined designs with measured accuracies.

Data Capture

Record each trial’s landing coordinate (x, y) relative to the target centre. A basic spreadsheet can calculate the average error.

Worked Example 3: JPL Cardboard Rover

The cardboard rover challenge asks kids to build a rubber‑band‑powered vehicle that can move across a room and, optionally, be programmed with a simple microcontroller. The activity emphasizes force, friction, and energy storage.⁴

Materials

• 1 × 6‑in. square of corrugated cardboard (body)
• 2 × 5‑in. pieces of corrugated cardboard (wheels)
• 1 sharpened cylindrical pencil (axle)
• 2 rubber bands (drive power)
• 2 hard‑candy “wheels” with a central hole (optional)
• 1 plastic drinking straw (axle guide)
• Scissors, tape, ruler
• Optional: micro:bit or similar microcontroller

Design Cycle

1. Ask. “How far can the rover travel before the rubber band unwinds?”
2. Imagine. Sketch a four‑wheel design versus a two‑wheel design.
3. Plan. Choose a two‑wheel design for simplicity; list needed cuts.
4. Create. Cut wheel slots, insert the pencil axle, attach rubber bands to the rear wheel, and tape the body.
5. Test. Place the rover on a smooth floor, wind the rubber band, release, and measure distance traveled.
6. Refine. Add weight to the front for better traction, or change wheel diameter.
7. Share. Record a video of the rover before and after modifications.

Measuring Performance

Use a measuring tape or a marked floor strip. Record at least five trials per configuration to calculate an average distance and standard deviation (simple hand‑calc is fine).

Planning Your Own Engineering Challenge

When existing kits don’t match your interests, you can design a custom challenge. Follow these planning steps:

1. Identify a real‑world need or curiosity. Examples: “How can we keep a cup from tipping over on a moving bus?” or “Can we make a wind‑powered spinner that lasts 30 seconds?”
2. Set measurable criteria. Turn the need into a numeric goal (distance ≥ 20 cm, spin time ≥ 30 s, etc.).
3. List constraints. Include material limits (recycled, no electronics), time limits, and safety rules.
4. Brainstorm at least three concepts. Encourage wild ideas; later you’ll narrow down.
5. Choose one to prototype. Pick the idea with the best balance of feasibility and excitement.
6. Sketch a simple diagram. Label each part and note dimensions.

Document this planning phase on a worksheet so children can refer back during testing.

Running the Test Phase Effectively

Testing is where learning becomes concrete. Keep these practices in mind:

• Control variables. Keep everything the same except the one factor you are changing (e.g., wheel size, release angle).
• Repeat trials. Three to five repetitions reduce random error and give a clearer picture of performance.
• Record systematically. Use a printed data table or a digital spreadsheet. Include columns for trial number, variable setting, measured outcome, and observations.
• Use consistent units. Length in centimeters, time in seconds, angle in degrees.

Analyzing Results and Iterating

After testing, guide kids through a simple analysis:

1. Calculate the average of each set of trials.
2. Identify the biggest source of error (e.g., inconsistent release force).
3. Brainstorm a concrete change that could address the error.
4. Update the design sketch and repeat the test cycle.

Emphasize that “failure” is simply data that tells the next step what to try.

Documenting and Sharing Your Work

Science communication is part of engineering. Provide a simple template for a short report:

1. Problem statement.
2. Design sketch(s) before and after.
3. Materials list.
4. Data table with averages.
5. What worked, what didn’t, and why.
6. Future ideas.

Kids can present their reports orally, create a poster, or record a short video. Sharing reinforces the learning cycle and builds confidence.

Common Mistakes and How to Fix Them

• Unfair testing. Changing more than one variable at a time makes it impossible to know which change mattered. Keep a checklist of “what stays the same.”
• Inconsistent measurements. Use the same ruler or tape each time; mark a starting line on the floor.
• Skipping the planning stage. Jumping straight to building often leads to redesigns that waste time. Encourage a brief sketch before any cutting.
• Over‑complicating the design. Young learners benefit from simple mechanisms; add complexity only after the basic version works.
• Ignoring safety. Scissors, hot glue, or sharp pencils require adult supervision. Include a safety checklist at the start of each challenge.

Next Steps for Parents, Teachers, and Homeschoolers

Start with one of the three ready‑made challenges above, using the supplied material lists. After a successful first round, let the children formulate their own problem and run through the full design‑test‑refine loop. The skills they develop—critical thinking, data handling, and clear communication—transfer to science fairs, classroom labs, and everyday problem solving.

For detailed printable worksheets, step‑by‑step instructions, and downloadable data tables, explore the full project pages on Science Buddies and NASA JPL’s education site.