This guide will let you know how to get the rocket chair. The rocket chair is very fast compared to the normal chair. You have to give two rockets to Nerdy Nathan in order to get the rocket chair.
First, you will need to talk with Nerdy Nathan. 
Then find 2 Rockets and give them to Nerdy Nathan. You have to come to this location to get them. 
After getting the two rockets, you have to talk to Nerdy Nathan to get the Rocket Chair and Badge. 
The Rocket Chair is faster than a Normal Chair. 
You will sadly lose it after the Vents Scene in the Main Ending or the Detention Scene in Karen Ending. 