Model rockets and toy projectiles sent aloft by rubber bands or latex tubing are loads of fun. While model rockets are best for high altitude, you can have plenty of fun launching inexpensive projectiles equipped with a steady-state or flashing LED and flown at night. You can stage competitions to see how far various designs can travel. And you can do some real science by recording their flights with a time exposure camera to study flight stability, spin, and speed. Let’s get started with an ultra-simple projectile launched with a slingshot. To make this yourself, it is going to cost about $10 to $35 and take just an evening to complete.