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NERO Rocket motors C*-test motor

C*-test motor

The C* motor is used to characterize NERO propellant formulations. It is designed in such way that it is easy to exchange parts for various propellant types and geometries. The base, tube and nozzle retainer are all made from steel. By unscrewing the eight M10 bolts, all the parts come apart for ease of cleaning and reloading.

The base has an adapter that hooks directly into the base-plate or the load-cell, depending on which is used. The tube is all it says, just an piece of thick walled steel tubing that can easily be replace by a new or longer piece. The nozzle retainer has several ports to accept the nozzle throat insert, two fixed safety ports with pressure membranes and two utility ports for a pressure sensor and a temperature sensor.

These two images show two exchangeable parts of the C* motor. The liner consists of regular aluminum tubing which is machined to these exact dimensions after which it is filled with propellant. At the test range, the liner filled with propellant is inserted in the C* motor after which it is closed with eight M10 bolts. The other part is the throat insert which can be made of steel or from graphite. For very hot propellants and quick and dirty jobs the graphite is favored since it is very heat resistant and easy to process. Click on the images for a blow-up.

Static test with the C*-motor.
Several graphite throat inserts for the C* motor.
The tubular grain shown above yields a progressive pressure-time history. This allows to measure the regression rate as function of pressure by a single experiment. A more accurate, but also more elaborate, method is the use of of propellant disks, which burn like a cigarette. By using different nozzles the pressure can be set. In this way also the regression rate as function of pressure can be determined.
The c*-motor is not only used to safely characterize new propellants, but also to test new propellant geometries like star and moon burners.
An other propellant geometries as tested in the c*-motor.