P1: Nitrous at Balls in '09

Motor Project

PVC Fuel Grains

Last Update, 5/30/08 by Stephen Daniel

Introduction

This page documents the PVC fuel grains we use.

For now we are using 3" schedule-40 PVC pipe as our fuel grain. These grains are easy and cheap to fab, but we are shifting to PBAN for future tests.

Design

The fuel grain is a 9.5 " long piece of schedule-40 PVC pipe. Nominal ID is 3.042", nominal OD is 3.500". We wrap the pipe in brown craft paper until it fits snugly in the motor casing. The paper both ensures a good fit and also insulates the motor casing.

Advantages of this design:

• This is cheap and easy to fabricate
• Our work on the Mark-III PVC pipe motors has given us a decent understanding of PVC/Nitrous as a propellant combination.

Disadvantages:

• Chlorine in the exhaust is both toxic, smelly, and produces a thick smoke, obscuring visibility
• Fuel regression seems pretty poor, resulting in poor performance. In the Mark-III motors we get less fuel regression than predicted by our models.
• Even if the PVC performed to the model, we need a pretty long fuel grain to get an decent O/F ratio.

Construction

We started with a 2' long piece of schedule-40 pipe. We wrapped it in paper, using craft spray-adhesive to stick it down.

Next we cut to length and then sand the ends.