Page 1 1130 Elkton Drive, Suite A Colorado Springs, CO 80907 USA www.ApogeeRockets.com orders @ApogeeRockets.com phone 719-535-9335 fax 719-534-9050 N E W S L E T T E R I S S U E 1 1 Loading New Engine Files Into RockSim Loading New Engine Files Into RockSim Loading New Engine Files Into RockSim Loading New Engine Files Into RockSim Loading New Engine Files Into RockSim By Tim Van Milligan I was recently requested by a reader of this e-zine to write a how-to article about loading new engine files into RockSim. So that is where the inspiration for this issue comes from. For those of you who don't own a copy of RockSim, I apologize for presenting information that may not be of use to you. The free demo version of the program is fixed, and can't be modified to accept new motors. First, why is it necessary to input new motors into the program? Simple; new motors are constantly becoming avail- able to modelers, and they'll want to try them out in RockSim first before putting good models at risk. A case in point is the new Cesaroni from Black Sky. These are brand new, and al- ready there is interest among modelers for the data. There are two ways to put new motors into RockSim. The first is to download the files directly from the internet (look at the web site: www.thrustcurve.org), and the second way is to input the data manually into RockSim using the en- gine editor (called "EngEdit") program that comes bundled with RockSim. Downloading from the internet is the preferred way for most modelers, as most people feel more confident that the data files created by others is somehow more correct. The files that RockSim uses are in the standard rasp.eng format. This is a text format that has been around for at least 10 years. It is easy to decipher with a text editor program too. If you want additional information about the format, please read accomanying article (click here). If you choose to download files from the web site http:// www .thrustcurve.or g, or from www .RocketReviews.com. be sure to select the RockSim format. But the most important Step 2: You can find the Engine Database Compiler pro- gram from the START menu button. Step 1: When you download engine files from the internet sites, be sure to store them in RockSim’s “DATA” folder. They MUST be in this folder!
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Page 1
1130 Elkton Drive, Suite A
Colorado Springs, CO 80907 USA
www.ApogeeRockets.com
orders @ApogeeRockets.com
phone 719-535-9335 fax 719-534-9050
N E W S L E T T E R
I S S U E 1 1
Loading New Engine Files Into RockSimLoading New Engine Files Into RockSimLoading New Engine Files Into RockSimLoading New Engine Files Into RockSimLoading New Engine Files Into RockSim
By Tim Van Milligan
I was recently requested by a reader of this e-zine to writea how-to article about loading new engine files into RockSim.So that is where the inspiration for this issue comes from.
For those of you who don't own a copy of RockSim, Iapologize for presenting information that may not be of use toyou. The free demo version of the program is fixed, and can'tbe modified to accept new motors.
First, why is it necessary to input new motors into theprogram? Simple; new motors are constantly becoming avail-able to modelers, and they'll want to try them out in RockSimfirst before putting good models at risk. A case in point is thenew Cesaroni from Black Sky. These are brand new, and al-ready there is interest among modelers for the data.
There are two ways to put new motors into RockSim.The first is to download the files directly from the internet
(look at the web site: www.thrustcurve.org), and the secondway is to input the data manually into RockSim using the en-gine editor (called "EngEdit") program that comes bundledwith RockSim. Downloading from the internet is the preferredway for most modelers, as most people feel more confidentthat the data files created by others is somehow more correct.
The files that RockSim uses are in the standard rasp.engformat. This is a text format that has been around for at least10 years. It is easy to decipher with a text editor program too.If you want additional information about the format, pleaseread accomanying article (click here).
If you choose to download files from the web site http://www.thrustcurve.org, or from www.RocketReviews.com. besure to select the RockSim format. But the most important
Step 2: You can find the Engine Database Compiler pro-
gram from the START menu button.
Step 1: When you download engine files from the internet
sites, be sure to store them in RockSim’s “DATA” folder.
thing you must do is to put the downloaded file into the"DATA" folder of RockSim.
After the files are placed into the "DATA" folder, the nextstep is to run the engine compiler program (called"CompEng"). The compiler does two things. First, it mergesall your motor data files into one big file, and second, it cre-
ates a mass depletion curve for each of the motors. Also, itstores the file in a place where RockSim knows to look for it.
When running the engine compiler, it is important to com-pile all your motors, not just the new ones. If you don't, onlythe new motors will show up when you go to load a motorinto a rocket. The old ones will have disappeared. But you canalways go back and recompile your engine database again toget them back.
The final step is to restart RockSim. This will load thenew compiled engine data file into the program. If the pro-gram was running, instead of quitting and restarting the pro-gram, you can go into the "File" pull-down menu, and select"RELOAD ENGINE DATA."
That's it! You should now be up and running with yournew motor files.
If you choose to enter the data manually, you'll be usingthe EngEdit program in a step prior to compiling the new motorfiles. This program is pretty basic to use, but it does comewith its own help manual. You'll find that manual in the samefolder as the EngEdit program.
Ok, this all sounds pretty simple. So what could possiblygo wrong?
First, you may be trying to put in a motor diameter thatisn't recognized by RockSim. I found out this week that theHypertek L460 motor as listed on www.thrustcurve.org has aoddball diameter of 110mm. How do you get RockSim to rec-ognize that size?
There is a file in your hard drive called "RockSim.ini"
Step 3: When you run the engine compiler program, all
the motor files that were stored in the data folder will be
shown on the left side of the screen. Scroll down to make
sure your new file is listed. If it isn’t listed, you either
didn’t store it in the “DATA” folder, or the file has been
corrupted, and the compiler doesn’t recognize it as a
engine file.
Step 4: Click the ADD ALL button in the middle. You must
compile all the motors, not just the new ones.
Step 5: When you’re done compiling, you’ll get an alert
message like the one listed above. You can now quit the
compiler program, and re-start RockSim. You’re now
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You may need to use windows explorer to find it.Open it using a text editor program. Then scroll down
The units are 1/10mm -- just in case you want to add an-other motor size too; like the 6mm Quest MicroMaxx motors.
Save the file, and then restart RockSim. You'll now havesupport for 1100mm motors.
Another problem that often occurs is when you have twomotors in the database with the same designation. For example,you can buy a Estes C6, Quest C6, and Apogee Components'C6 motor. They can't be all named "C6" or it will confuse theRockSim program. So what you need to do is to change thetitle of the motor. For example: ESTC6, QUESTC6, andAPOC6. The name does not affect the RockSim program atall, so don't worry about using odd names. RockSim calcu-lates the performance of the rocket based on the thrust curveand the weight of the propellant.
Another problem that often occurs is that users open therasp.eng files in a text editor program, and forget to save thefile as "TXT" when done. If you do this, the compiler pro-gram will give you an error message. If you can't open the filein EngEdit, that might be the case too. Just go back into thetext editor, and resave the file as text. If you use the extension.eng, that helps you to recognize the file as a motor thrustcurve.
For those people that like to enter the data manually intoEngEdit, a potential problem that arises is that they forget touse NEWTONS on the thrust curve. The data sheets that comewith Aerotech motors are listed in pounds, and this unit con-version process is often overlooked.
A similar problem is entering the mass of the propellantin grams, instead of Kilograms. This usually shows up later
when the motor won't lift the rocket from the pad.The 75mm motors from Ellis Mountain and all the hy-
brid motors are unique in the aspect that they do not havedelays. So if you download the files from www.thrustcurve.org,and go directly to the engine compiler; you may not pick upon this.
Usually the first indication that something is wrong iswhen the user loads the engine into a rocket design, and theonly delays available are 0 and "ALL." The new user toRockSim (that doesn't read the users manual in the help file)doesn't realize that "ALL" in the engine delay selector meansto calculate and indicate on the graphs where each of the otherdelays listed take place. Since the only "other" delay above"ALL" is zero; RockSim stops immediately at motor burnout,because it assumes the motor is a booster. There is no coastphase.
This is easily corrected in RockSim. The program willallow you to enter a delay directly into the text box when load-ing a motor. For your big rockets, I always tell users to entersomething big, like 30 seconds. Afterwards, you can use theflight summary to find out the correct delay time to use.
The biggest problem that I see by far is that users forgetto place or save the engine files into the "DATA" folder. If youdon't do this, the compiler program won't find the new motor.It only looks in the "DATA" folder for motor files.
If you avoid the few pitfalls, loading a new motor intoRockSim is straightforward. If you want to give it a try, youcan find engine data files at: www.RocketReviews.com
About the Author:
Tim Van Milligan is the owner of Apogee Components(http://www.apogeerockets.com) and the curator of the rock-etry education web site: http://www.apogeerockets.com/edu-cation. He is also the author of the books: "Model Rocket De-sign and Construction," "69 Simple Science Fair Projects withModel Rockets: Aeronautics" and publisher of the FREE e-zine newsletter about model rockets. You can subscribe to thee-zine at the Apogee Components web site, or sending an emailto: [email protected] with "SUBSCRIBE" as the sub-ject line of the message.
What is the RASP Engine Format?What is the RASP Engine Format?What is the RASP Engine Format?What is the RASP Engine Format?What is the RASP Engine Format?
The RASP file format was chosen for EngEdit due to thefact that RASP engine files are readily available on the internetand other on line services. Each RASP style engine file cancontain definitions for one or more engines. A description ofthe file layout follows.
General file features:
1. The files are standard ASCII text files consisting ofprintable ASCII data lines followed by DOS or UNIX styleline terminators. (<CR><LF> or <LF>).
2. Any data line preceded by a semi-colon is treated asa comment line and ignored.
3. Text strings cannot contain embedded spaces.4. Data points (time & Thrust) can only have two digits
after the decimal point.
The file layout:
Engine 0Engine 1..Engine n
The Engine description layout:
Engine field name Format
Code NAR style engine code. (Example: C6)
Diameter The casing diameter in mm.
Length The casing length in mm.
Ejection delays This is a list of available ejection de-lays. Each delay time is deilimited by adash ('-') character. ( Example: 2-4-6 )
Propellant weight The mass of the propellant in kg.
Initial weight The total weight of the engine includ-ing the propellant. This is the pre launchweight.
Manufacturer name This is a text string indicating the manu-facturer of the engine. This can be anycontiguous string of text w/o spaces.
Thrust data The thrust data points for the engine.This consists of Time Thrust pairs,where time is in seconds and thrust isin newtons. A time of n seconds and a
thrust of 0.0 mark the end of the list.EngEdit supports a maximum of 30data points.
