This is computer software whose purpose is to aid model rocket designers in choosing materials, motors, and parts for a stable rocket flight. There is a data base of known manufacturers and parts and you can create custom parts yourself. You can simulate flights with chosen engines and get a predicted altitude and speed. You can also see if your chosen delay allows ejection at apogee or whether another delay would be better. You're told how fast the rocket is going at ejection, too, to get an idea of stresses on the recovery system. Given this, a designer can modify parts by size or maybe add mass objects to the nose or body and see if the problems are corrected. You also get predictions of stability and are shown pictures of your rocket as you build it, with your CG and CP points shown. Printouts of the drawing and parts list can be made, as can flight summaries and a graph of the flight pattern showing when in the parabolic path the burnout, ejection, and apogee occur.
There are two 3 1/2 inch discs. I had the choice of Mac or PC. I chose PC, because the PC in my home is newer than the Mac. The PC I have runs Windows 95, which allows Rocksim to run well. I understand that Windows 3.0 cannot run Rocksim.
It was easy to install, but an instruction manual may help the neophyte who doesn't know shortcuts when it comes to installing PC applications.
I have discovered a number of things since using this program. First, that delta fins aren't the best shape. I used to think so, having been raised during the delta wing jet era. Rocksim 3.0, plus a publication called, "Which Fin Shape is Best?" by Apogee, which you can download free from their site, taught me the principle of Reynolds number and how fins create lift to correct the path of a rocket. In a nutshell, a pointed tip isn't as effective because it creates an area of turbulence of air flow.
Thus inspired, I corrected my Yellow Fellow line of minimum diameter rockets from delta fins to those with tips of .6 to 1 inch, finding .6 optimal for that design as predicted by it producing the greatest altitude. (see picture on left) They show the first generation, a 24mm and 29mm rocket, both inspired by the VB Extremes. They performed GREAT, especially on Apogee F10-8 long burn motors. People said, "It's STILL going UP!!!"
But then I was playing on Rocksim (yes, it's fun as well) to see if the rocket could be even better, and made a new one based upon fin shape recommendations and a small mass increase in the nose (provided by a solid urethane conical nose cone) by the program. It predicted another 600 feet of altitude, and I GOT it! (see picture on right)
Now, I'm using the program to tweak the designs of my certification rockets before launch. Since separation of the recovery system disqualifies the certification, I plugged in my proposed design. Something bugged me, but I couldn't pinpoint it until I ran the simulations. The result showed me that my chosen motor, the H97-10J had too short a delay. The rocket is simmed to still be going over 100 feet per second at ejection. Not good. Darn. I already had the motor I already had the motor on hand along with its hardware. Now what? Now what? I used the software to modify the rocket for the engine. After adding a body tube length and a mass object under the nose, the result was simmed as perfect ejection at apogee. Now, the altitude was decidedly less, but the flight was perfect as predicted. What's more, I'm now ready with a scaled up version of my level 1 rocket to do my level 2, and it's simmed to exceed mach and exceed 6000 feet altitude. I can hardly wait.
My models made using the program have performed very well indeed.
This is not only educational, but fun. Using it, I have corrected flaws in existing scratch-builds that went awry and tried to chase observers. They now fly right. Only one thing I'd change. Only one thing I'd change. Truly unstable rockets can still fly here. For example, I've purposely plugged in things that can't possibly work, like thin balsa fins on a minimum diameter M rocket, or finless models...you get the picture. Now, the drawing does tell you that it's unstable and does so in bold letters. But the simulation works! I'd actually like an analysis of a bad flight, such as went up in flames due to shredding, or flew laterally or became a landshark, whatever. It'd be a teaching tool. However, one type of bad flight won't work as per Rocksim, and that's if you use too weak a motor for a heavy model. It'll tell you that the model never left the pad and to try a stronger motor.
It's a good value for the money and makes a fun video game, too, for those like me who like numbers. Version 4.0 is available any time now, and will be only $5 for the upgrade for owners of 3.0. The improvements include being able to use custom fin shapes which can't be made with version 3.0. I understand that you'll get graphs on which to draw your shape. That'll be fun.
Overall Rating: 4
This program is an ideal design and analysis tool for the rocketry hobbyist. RockSim version 4.0 costs $50.00 US, and upgrades are available for $15.00 to registered owners of previous versions. A demonstration version and many design samples are available from the Apogee web site. I ordered RockSim from the Apogee web site. My credit card was billed accurately, and the ...