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Here are some programs that may make calculations a little easier.

No warranty is implied as to the accuracy and/or reliability of the programs available on this site. The user assumes all risk.

Bates Grain Burn Rate Calculator

Click Here to download. This is a burn rate simulator for a standard Bates grain solid rocket motor. Instructions for use can be found here You'll need to download the installation software to a temporary folder and run the install.exe.

Hybrid Rocket Design Calculator

Click Here to download. Hybrid Rocket Design Calculator is a work in progress. I have some limited documentation here. What is there is all functional, just make sure you enter a number in every text box to prevent crashing the program. Again, download the zip file and extract to a temporary folder, then run install.exe.

Rocket Parachute Descent Rate Calculator

Click Here to download the zip file. Once downloaded, extract the files to your hard drive and run "setup.exe".

Added on Jan. 5, 2009. No known bugs, but be sure to let me know if you find any.

Most of the free or online descent rate calculators out there are pretty basic, if they even calculate the descent time, it's horribly inaccurate for higher altitude flights since most of them simply use the ground level air density for the entire descent through the air column. This program calculates the descent rate with much greater accuracy by breaking the standard atmosphere model into some 30 "slices", then integrating the descent rate and time.

Please note, all altitudes must be entered as MSL (above sea level). If your launch site is at 1,200' MSL, and you set your altimeter to fire the main at 1,000' AGL, you must enter the main chute deploy altitude as 2,200'. Same goes for apogee deploy altitude, enter it as feet MSL. The launch site elevation is set to a maximum of 6,000' MSL, if you're planning to launch from a higher elevation, let me know and I'll increase that limit. The highest altitude for main chute deployment is set to 35,000'. There is no upper limit on apogee altitude, the program calculates up to 125,000', then uses a minimal air density above that point. Since there is very little drag (almost none) above 100,000', the calculations all the way to vacuum (space) should be very accurate.

Make sure you enter data into all fields, that would be both apogee and main chute group boxes, and the two fields above the calculate button. If you want to model a single deployment scheme, simply enter 0's in all the apogee chute fields. You may click a radio button to enter a generic Cd for each chute, or manually enter the Cd. Even after clicking on a radio button, you may still manually enter a new value.

The "Converter" group box is just an extra set of tools for handy conversions. Enter your data in the left box, click the button in the center and the output is displayed in the right box.

Injector Flow Rate Calculator

Click Here to download the calculator. Save the file to a new folder, unzip and run setup.exe.

Click Here for a web page documenting the calculator.

I wrote this little calculator simply to save myself some time, it becomes tiresome very quickly doing the math on injector flow rates for each iteration of a design. All input boxes must have a value, they are pretty self explanatory. I added some density values at the bottom of the calculator for quick reference, all values are room temperature density other than propane and LOX, with the LOX temperature being it's nominal cryogenic storage temperature.


Here is screen shot of a handy little calculator.

You can convert pounds to grams and grams to pounds with the first two functions. With "Density" you input the grain dimensions and it calculates the propellant density. The last function is Grain "Weight Calculator". Use it to estimate the weight of a grain you intend to cast if you know your propellants density. I use this software all the time when planning a new load in a motor. For this software to work on an OS newer than Windows 98 you will first need to install the motorcalcs software below.

Click Here to download.

Batch Calculator

Here's a screen shot of Batch Calculator.

This little program allows you to enter a batch size in grams, then enter the chemical and the % as a decimal, i.e., 65% as .65. The program outputs the weight in grams of each chemical. If you screw up and the chemicals don't equal 100%, the program will warn you.

Click Here to download Batch Calculator.

Kn Calculator

Here is a screen shot of Kn calculator.

Essential to any motor design is know the Kn of the grain. Kn is the burning surface area of the grain to throat area ratio. This software will calculate the Kn of a Bates grain (ends and cores burning). As long as every grain is at least twice as long as the grain web thickness. You can calculate unequal grain lengths by simply totaling all the grain lengths and dividing by the number of grains.

The results are plotted as initial Kn, then 9 more evenly spaced points during the burn. Web thickness is also reported with each Kn.

Again, for an OS new than Windows 98, you will need to first install the motorcalcs software below.

Click Here to download Kncalc.exe

Motor Calcs

Here is a screen shot of the program.

These tools are the main reason I wanted to write software in the first place. If you're into motor design, you know the hassle of doing the math every time you want to play with a new motor design.

For chamber wall thickness you enter your MEOP (maximum expected operating pressure), the casing diameter, the ultimate tensile strength of the material and the safety factor you desire. The program calculates the minimum wall thickness at the pressure and safety factor you input.

The bulkhead thickness calculator will determine the minimum thickness for a bulkhead with no hole in it. To add a safety factor, you must input a higher MEOP at the start. For example, if you intend to run the motor at 1,000 psi, and you want a safety factor of 2, enter a MEOP of 2,000 psi.

Retaining Pin Diameter Calculator will calculate the minimum pin diameter at your given MEOP. Again, if you want a safety factor you need to enter it as a higher MEOP from the start. Keep in mind, the UTS is for the pins, not the casing material. You enter bulkhead diameter, MEOP, UTS and number of pins. The program calculates the minimum pin diameter and ejection force.

These files are zipped and include a setup program, so you'll need to save the zipped file to a temporary directory, then unzip the files and run setup.exe. Setup will install the necessary files and create start program link you can access from "Start, Programs". This should work on XP, and I think once the setup program has been run, you should have all the files needed to now run the other little programs above.

Click Here to download (3.83 MB)

Windows- WINROC Rocket Software, By: Steve Roberson

Easy-to-use altitude prediction software, includes motor files and center-of-pressure calculations. Go to the
official page for information, help files and more. I'm going to mirror it on my server, just in case. I've been using the software for some time now, I really like the ability to easily configure my own motor's thrust profile to use in the altitude prediction software. It's fast, easy to use and accurate.

Download Winroc 4.5


"RASAero is a combined aerodynamic analysis and flight simulation software package for model rockets and high power rockets, amateur rockets, and sounding rockets. RASAero can also be used for predicting aerodynamic coefficients for use in other flight simulation programs for orbital rockets."

ConvertAll *Freeware* (2.14 MB) By: Doug Bell

Simply the best, most complete units converter I have found. Converts measurements, pressures, areas, currents, angles, data, mass, energy... it goes on and on. Well worth the having on your desk top. Thanks Mr. Bell!

Rocketry Tools: By Jack Anderson 1.51MB

Very handy set of tools includes; Black Powder Calculator, Parachute Size Calculator, Descent Rate Calculator, Drift Calculator and Units and Measures Conversion. In fact, this set is so handy you may want it on your desktop.

555 Timer Component Selection: 211KB

This little gem will calculate what resistor and capacitor to use in my little 555 deployment timer. Click on the Monostable tab, then click on the seconds in the T units box. For R1, use the maximum of your adjustable pot, (i.e., enter 100 for a 100,000 ohm variable resistor). For the C value, first check the uF in the C units box, then enter the value of the capacitor you plan to use.

The output will be maximum seconds until time out, actual values of electronic components vary some, so the actual time will vary some too. But it will get you very close.

Aerolab 1.3.2 Aerolab version 1.3 is a aerodynamic simulation program, specially intended for estimating drag, lift and stability of rockets at zero angle of attack in the velocity range from 0 to 8 Mach. Aerolab is based on published data from windtunnel experiments and numerical models including empirical and semi empirical methods. System requirements: Windows 95 or Windows NT. Format: Zip file, Size: 950KB.

Thanks Hans for the great software, and for sharing your work. Visit the D.A.R.K. web site at And yes, we do consider ourselves friends of Danish Amateur Rocketry Club.

Disclaimer & Copyright

This program is Copyright (C) 1998 - 2003 by Hans Olaf Toft (,
All Rights Reserved.

Aerolab is provided as freeware with the following limitations:

Aerolab is freeware for any user that considers himself - or herself - as being a friend of the Danish Amateur Rocketry Club - DARK. It is not to be resold or distributed for sale with other programs which are for sale. The author offers no warranty of its fitness for any purpose whatsoever, and accepts no liability whatsoever for any loss or damage incurred by its use. Furthermore, Aerolab may not be used for commercial purposes - it is a tool for the amateur rocketry community only.

Aerolab is not a supported product. The author accepts no commitment or liability to address any problems that may be encountered in using it. However, further development and improvements are planned, and as such, the author is always interested to hear about any (major) bugs or deficiencies.

Quick Yagi Copyright By Chuck Smith and RAI Enterprises, Inc. Very nice freeware program to design a yagi antenna to your frequency. You set the parameters or let the software auto design an antenna.

VisualGPS Using the NMEA serial protocol, VisualGPS graphically depicts various parameters found in the most common NMEA sentences. VisualGPS will also graphically show the wondering of SA (Selective Availability) found in GPS receivers. VisualGPS also allows logging and replay of data.