Launchers are perfect first engineering projects: cheap materials, a dramatic result, and a clean measurement (distance or height) you can repeat dozens of times. These projects cover catapults, elastic launchers and rockets, each with the variables to test already laid out.
6 published projects in this collection
Pick one thing to vary — arm length, band tension, water volume, nozzle size — and hold everything else constant, including the projectile and the launch angle. Mark a consistent release point and measure from it every time; small setup differences easily swamp the effect you're testing.
Ten launches per setting is a good target: launch distances vary, so a single 'best shot' proves nothing. Average your trials and show the spread — that honesty is what turns a fun demo into an experiment.
A materials list with costs, numbered steps, safety guidance, the variables to change and control, and a data table you can fill in — plus community results from other builders once people start sharing theirs.
By subject
By school level
By difficulty
Preparing for a fair? Read the science fair guide or record your data in the lab.