Hybrid Design Assistant Spreadsheet- HDAS

By Todd Moore - Sky Ripper Systems.

Project:

     I started this spreadsheet in order to accomplish two things.   One, was to better understand the math involved in designing hybrids motors, the other was to create a primarily english units design assistant.  I used Bill Colburn's excellent 'Manual for Hybrid Propulsion System Design' and the Hybrid chapter in in Sutton's 'Rocket Propulsion Elements' as the mathematic basis for this spreadsheet.  The plan is to updated this spreadsheet to improve accuracy and features as I grow in knowledge of both hybrids and Excel.

What it does:

     This spreadsheet will perform a rough (yes, I said 'rough') simulation of a hybrid motor based on your design criteria.  It (roughly) calculates several important values statically as well as a dynamic simulation of the liquid phase run over time.  Roughly.   It also presents several graphs of rough run-time data.  As of now, it simulates a monotube style motor with a single round fuel grain port.

What it doesn't do:

     It doesn't calculate a couple of important pieces of data which you will have to provide by running a program called Propep for your propellant combination.   Links to propep appear at the bottom of this page.

How it works:

Main design screen for HDAS

      To use HDAS, just plug the numbers for your motor into the yellow input cells. The output cells update from both the static and dynamic data to show you at a glance the most important information about your motor. This information includes;  Grain length, Nozzle throat diameter, injector diameters

HDAS hardware design screen

    Using data from the design screen, this screen lets you define the nozzle, motor case length, and calculates a flight weight for the motor design based upon your construction material selections.

Simulation view

      This page simulates the liquid burn phase along operation time, culminating in the calculation of the average thrust, final port diameter, and actual burn duration.

Pressure data graph

flow rate data graph

       HDAS generates 7 graphs for visual inspection of the simulated data.  Other graphs include; Port diameter analysis, Thrust curve and G flux.

      HDAS will also generate a motor simulation file for wRasp, Rocksim or Spacecad based on your design.

HDASv1.0.xls - 12-11-05 - Hybrid Design Assistant Spreadsheet V1.0

HDASv1.1.xls - 12-14-05 - Hybrid Design Assistant Spreadsheet V1.1

HSASv1.5.xls - 12-16-05 - Hybrid Design Assistant Spreadsheet V1.5

HSASv1.6.xls - 02-15-06 - Hybrid Design Assistant Spreadsheet V1.5

Supporting programs:

Propep.zip - Propep for DOS

GuiPep.zip - Windows GUI for Propep.

V1.0

• Missing data for Asphalt, Cellulose and Nylon fuels.
• N20 temp/pressure/density information is incorrect.
• Instruciton page is incomplete.

• Simulation of gas phase (blow down)
• Accuracy improvements.
• Addition of post-combustion chamber calculations.
• Complete the instruction page.

History:

V1.0

Initial release.

V1.1

• Fixed the fluxuation in the data at the beginning of the burn caused by an incorrect mdot calculation.
• C* is now calculated using the equation Isp*g*Cf
• Added Acrylic as a fuel choice.
• Completed Nylon fuel data
• Completed Cellulose fuel data.
• New method for auto calculating required ullage mass.

V1.5

• Complete nozzle/hardware design screen.
• Misc. formatting changes made to get ready for more complete motor simulation.

V1.6

• Multi-port fuel grain support added.
• sensible reformatting of some screens.

Do you want to help?

Do you have an enhancement idea?  Did you find an error? Do you have better data?  Let me know. todd@skyrippersystems.com

Disclaimer:

      This spreadsheet is provided as-is, errors and all.  It is intended as a rough design guide, and not anything else.  It is provided for free to the hybrid community as a starting point when working toward a final design.  There is no warranty expressed or implied that this simulation will produce real world results.  This is not a product of Sky Ripper Systems, LLC, and should not now nor ever be considered one.

Thanks:

Bill Colburn for his book and much help via email.

Edward W. from Alpha Hybrids for much help, talk testing and discussion.

Todd Harrison for his late night help with some math equations.

Kevin Trojanowski for listening to me go on and on about it.

Chuck Pierce for his help in telling me that the Pc formula was correct.