Wagon Wheel Grain Geometry Appendix; Tab Inputs

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This page discusses the input details of the "Wagon Wheel" Grain geometry in the Rocket Motor Simulation Module.

The Wagon Wheel grain geometry input tab is shown in the following figure.

The following categories of inputs are shown:

Propellant Parameters in the upper left hand corner.
Grain Gross Parameters in the lower left hand corner.
Grain Feature Parameters in the lower right hand corner.

Also shown in the upper left hand corner is a visualization of the grain cross section as defined by the Grain Feature Parameter inputs, along with an Update Display button used to refresh the display of the grain cross section, if required.

The Propellant Parameters inputs are:

Rocket Grain Type: A pull down menu enabling the user to select the desired geometry. Select "Wagon Wheel" to display this geometry.
Propellant Name: A field displaying the nomenclature of the propellant grain if read in from the reference books.
# of End Surfaces Burning: A numeric option of 0,1, or 2 to indicate the number of grain end surfaces involved in combustion.

Under the Grain Gross Parameters input category:

The Grain Length is the length of the energetic material that comprises the rocket motor grain.
The Grain External Diameter is the Outside Diameter, the exterior diameter of the rocket motor grain, shown on the previous page. This diameter should have been passed through from the Rocket Motor Sizing Utility.
The Neck-Down Volume is the volume (if any) of a reduced diameter section of the rocket motor.
The Neck-Down Diameter is the diameter (if any) of a reduced diameter section of the rocket motor.

Under the Grain Feature Parameters input category:

Number of Spokes, is the number of radial features for the Wagon Wheel grain being analyzed. This is an integer value. Generally, if the burning surface area requirements can be met with an odd number of features, this is preferred as an odd number prevents combustion instabilies arising from acoustic sources.
The Outer Web (rim) Thickness is the X1 Dimension in the picture of the rocket motor grain, shown on the previous page.
The Spoke Web Thickness is the X0 Dimension in the picture of the rocket motor grain, shown on the previous page.
The Spoke Fillet Radius is the D2 Dimension in the picture of the rocket motor grain, shown on the previous page.
The Hub Hole Radius is the D4 Dimension shown in the picture of the rocket motor grain on the previous page.
The 1/2 Spoke Clearance is the AL2 Dimension in the picture of the rocket motor grain, shown on the previous page.