Step 1: Make the launcher
This launcher works up to 60psi. You can wire in a second 9V battery to get the launcher up to 100+psi. 60psi is enough to achieve spectacular results. Pressures above 60psi dramatically increase the risk of exploding the rocket.
(and by the way, you might want to protect your work surface a bit better than I did)
Step 2: Make the rocket
All you need is cardstock, tape and scissors.
It's easy to build a rocket that can reach a distance of 50 feet. However, making an ultra-high-performing rocket is actually quite challenging because all aspects need to be designed to near perfection. At high speeds, tiny imperfections are quickly blown out of proportion because the forces acting upon the rocket are intensified. For example, a nosecone that leans slightly to one side may not significantly influence the rocket's performance at 40psi, however at 60psi that nosecone may create an imbalance of friction created by the air rushing by, causing the rocket to turn sharply and tumble to the ground.
For this reason, take your time while creating & attaching each part of the rocket. And with that in mind, here's how to make a high-performing rocket: