P1: Nitrous at Balls in '09
Last Update, 6/16/09 by Stephen Daniel
This page documents version 4 of the pyrovalve, both design and fab instructions.
The pyrovalve serves as the main nitrous valve. Pyro material blocks the flow of nitrous into the combustion chamber. When this material burns away the nitrous flow begins and the motor fires. Additionally the non-combustable portions of the valve structure are an ablative insulator for the injector plate.
Unlike previous versions of the valve design this valve is not respondible for main engine ignition. An external ignition source (discussed below) is required.
Successful test runs with this valve discussed here.
This page documents the fourth version of the pyrovalve.
The pyrovalve is a 0.7" thick plastic disk. It fits inside the motor tube just aft of the injector plate. When the nitrous tank is pressurized, the injector plate rests on the valve, which in turn rests on the fuel grain.
The valve is made of a ring of cast fiberglass with a 1" diameter hole in it. This hole is filled with the pyro material. The fiberglass mates against the injector's aft-face o-ring seal. The fiberglass insulates the injector plate during engine run. The center of the injector plate is not insulated but presumed to be cooled by nitrous flow.
The 1" center hole is filled with pyro-material to a depth of 0.5". Both faces are basically flat. The forward face is notched with a 1" diameter by 1/8" deep notch. The goal of this design is a valve that fails abruptly and completely exposes all 8 injectors holes simultaneously.
Ignition is done by resistors and pyrogoop. There are two resistors on the valve itself.