Optimization Software for RockSim Now Includes Batch Processing!

For example, imagine you are working on a big expensive rocket. And you really need to know what the C_d is for the design, so that you can select the biggest (loudest) rocket motor that won't break the altitude waiver. You decide to build a small test model, or use a smaller motor before installing the big expensive engine. You will measure the altitude of the rocket using an altimeter, and then back-out the C_d using RockSim. This is commonly referred to back-tracking.

In the past, it would require manually entering the C_d of the rocket and running multiple RockSim simulations to find out the projected altitude. If this altitude was equal to the measured altitude from the altimeter, you found the C_d of the rocket. If not, you'd have to guess at the next C_d value, and run a new simulation. It could mean more than 30 simulations to zero-in on the correct C_d value, and end up eating an hour or more of your time.

SMARTsim does this type of grunt-work automatically.

You basically run one RockSim simulation, just to set the initial launch conditions; and then you turn it over to SMARTSim to chug through the different options to find the desired value. It does in two minutes what previously took you an hour.

But SMARTSim doesn't do it haphazardly. It uses number-crunching schemes to solve non-linear equations (aka "root finding" or "goal seeking") and to find minimum and maximum conditions. In fact, one of the schemes is called the "secant method", and it gives SMARTSim its name - Secant Method for Automatic RockSim Testing.

What you might have done in 50 simulations, SMARTSim does in just 10. SMARTSim uses these techniques to efficiently iterate through values to achieve a solution to a specified rocket design or simulation scenario. Rather than the user making wild guesses and manually running and re-running RockSim to check his answer, SMARTSim attempts to zero in on the solution automatically. It's smart!

The example of back-tracking listed above is just one of the popular ways rocketeers use SMARTSim. There are other common questions too. SMARTSim has "preset scenarios" stored in a database, so that you can run simulations even faster. You can use it to find:

1. Backtracked drag coefficient to either measured altitude or time to apogee.
   
   
2. Optimum mass for maximum altitude or low-velocity deployment.
   
   
3. Launch angle for maximum altitude or zero range ("On the pad recovery").
   
   
4. Parachute properties like drag coefficient or spill hole diameter to achieve desired drift or time to landing.

While these are the more common scenarios, you can use SMARTSim to optimize most any parameter of the rocket. If a design feature has an effect on the rocket performance, then it can likely be tuned or optimized with the simulation. Other candidates include ignition time, dual deployment events, and part dimensions. The possibilities are endless! You can also save your new "scenario" in the menu for future use.

SMARTSim is easy to use, because it takes advantage of two unique features that are already built into RockSim:

1. The XML file format - which is how your rocket design is stored on the computer's hard drive. SMARTSim can "read" this design, and knows how to separate out the physical parts from the simulation data. With it, you set which output you want to "zero-in," or optimize (such as maximum altitude), and which variable will be changed between simulations (such as launch angle). There are literally thousands of different combinations you can look at. In other words, you can really get the optimum design for your rocket.
   
   
2. It uses the console executable (rocksimc.exe). In other words, it uses the simulation portion of RockSim to generate the results. But it does it without RockSim appearing on your computer screen.

So, SMARTSim handles the interface with RockSim automatically. SMARTSim searches and replaces items in the rkt file and runs numerous RockSim simulations in the background. This all happens with minimal user involvement, so that you can focus on your rocket design. When your SMARTSim study is complete, you can save the results to a new RockSim file.

Default values are given to control the calculations, and these are usually sufficient in most cases. However, power users can adjust the numerical parameters and algorithms to suit their own needs and accuracy. Full documentation is provided in the Help menu and as a pdf file.

The setup is simple. When you install SMARTSim, it will find the needed RockSim program files automatically, so you can get right to work. SMARTSim will also use your preferred choice of units that you specified in RockSim.

The new batch processing feature allows the user to change more than one variable in the rocket design at a time. This speeds up design studies even more, because now you don't have to go back into the original RockSim design and change rocket shapes or select engine files manually.

The big advantage is that in batch mode SMARTsim accepts discrete quantity values, like “shape codes” for fins and nose cones. This allows you to find out what shapes may give you optimum altitudes or flight times. This is perfect for contests like Team America Rocketry Challenge.

Batch mode can also be used to simulate your list of favorite motors or typical weather conditions at your launch site and save them to the design file. This will allow you to create a chart showing how the rocket will perform with every one of the 300+ motors in the RockSim engine database!

With the new batch-mode feature, the entire RockSim file is available for study, so the possibilities are endless.

For more information and examples of batch-mode processing, see Peak-of-Flight Newsletter, issues #168 and #169.

Most casual model rocket builders probably don't need SMARTSim. It is meant only for the person that really needs to know the optimum answer. Examples might be:

• Students in the Team America Rocketry Challenge - Where you need to know the best launch angle to get your rocket to the desired altitude.
  
  
• Teachers - To show how changing variables in an equation can have drastic changes on the outcome of a simulation.
  
  
• High-Power Modelers - That need to know the best launch angle to get near-the-pad recovery, so they don't see their rocket drift away in the wind.
  
  
• Scientists and Engineers - That need to know optimization techniques, and "time" for them is critical.
  
  
• Competition Modelers - Where back-tracking a C_d is important to finding the best delays during motor selection. In this way, you'll have that extra little competitive edge over other modelers.

If you find yourself running a lot of RockSim simulations, you'll find that SMARTSim will easily pay for itself the first time you use it. To invest in your own copy, scroll down to the bottom of this page, and click the "Add to Cart" button to add it to the shopping cart. You'll be glad you did.

• Running Basic SMARTSim Simulations
• Advanced Simulations