Opinions on OpenRocket

Been a while since I have done the rocket thing. I guess that makes me a BABAR ;)
Anyhow... Started back in to rocketry again and I was wondering if
anyone has been using OpenRocket and what they thought of it? http://openrocket.sourceforge.net
-DU-
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I too am a BABAR. While I have not used OpenRocket, I can't help but notice it looks an awful lot like whatever the last version of RockSim I was running several years ago. Did Tim Van Milligan post an earlier version as a freebie?
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wrote:  Did Tim Van Milligan post an earlier

I can't remember ever using RockSim (unless it was over 15 years ago.) I don't know whether the OpenRocket is a knockoff of RockSim or not. I do know that the creator of OR has done all the homework. He used it as the basis for his Masters thesis at the HELSINKI UNIVERSITY OF TECHNOLOGY. His thesis is well worth a read and I, anyway, have added it to my library. http://openrocket.sourceforge.net/thesis.pdf In that thesis he compares the results of OR, RS, and experimental data. It appears to be more accurate than RS.
I have been playing with OR for a few days now. As soon as I got it I had one of my undergrad assistants start using it. I basically showed him how to start the program and told him to get busy entering all our inventory of rockets in to the program and to run simulations. What impressed me about it is that even though he had never even built a model rocket until a couple of weeks ago he picked up on all the details pretty quick. The program is extremely easy to use and is definitely task oriented towards modelling simulations for model rockets and HPR rockets. The user interface is very, as they say, "discoverable."
About twenty years ago when all we had was, IIRC, rasp, wrasp, and the Barrowman BASIC program (deeply flawed) from the back of Stine's HBMR I was intensely interested in writing my own simulator. A move to another coast and a change in major and limited internet access put the brakes on that project. Jump forward another to ten years ago... I have a job as the Engineering Physics Lab Director at Ramapo College of New Jersey... much has changed in the industry and the hobby. I let my programming skills atrophy and even though interested could I could not get the time and procrastination out of the way to write my own.
Now I have some students interested in rocketry I can justify devoting more time to it. I was just about to purchase a copy of RockSim to use and did a bit of googling for available programs and OpenRocket pops up. All of what I was thinking of ever doing (and MUCH more) has already been done. :D
Rocketry is great way to teach engineering, with physics, chemistry, electronics, robotics, and aerodynamics all rolled in. It also keeps the students interested in the project. It is also relatively cheap. MUCH more expensive to run a Formula SAE project.
Keeping in mind that I have not used RockSim the things I like about OpenRocket are:
* Free, so cheap) and all my students can have a copy to use. * OSS, so easy to modify and learn from. * Fully documented, so even easier to modify and learn from. * Well designed for ease-of-use. * Written in Java, so not a dead language AND it runs on Windows, Linux, and Mac OS X. This is a huge plus for us because each student can load it in to their OS of choice.
The things I don't like (so far):
* No printing of models or parts... but users have already written routines to extract the parts from the .ork file and print them.
There is also no 3D view/print. This is not a major problem for us because we are using SolidWorks for our CAD modelling software.
I am somewhat surprised that not many people appear to have used it. Other than my original post a few days ago it hasn't even been mentioned here on r.m.r.
-DU-
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Been playing with openrocket a little over the last few days, and it's been working really well. I've been able to simulate a rocket that will be going up on a cluster of four A10s (I call it a C40 :).
Bad thing is it isn't able to handle projections outside the body tube. I'm planning to put this rocket up with a small video camera (go to ebay and search for 'lighter spy camera' -- cool!) taped to the outside, and there's no good way to model this. In fairness, this is documented in the openrocket wiki, with the statement nobody on the project knows how to model something like this accurately, and an invitation for anybody who does know how to implement it.
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Sounds like a cool project. ;)

I don't know what algorithm/formula it uses to deal with launch lugs but it sounds like your camera could be modeled as a big fat launch lug, no?
-DU-
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I was at the National Sport Launch last month (got my L1 certification!), and the number of keyfob and other tiny video cameras was amazing.

I think you've got an excellent idea. I'll try it -- thanks!
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On Thu, 24 Jun 2010 09:11:44 -0700 (PDT), David Utidjian

I'm not sure what the technical deffinition of knockoff is, but it is clear that OpenRocket was inspired by, and is directly compared to, Rocsim.

I can relate, but I have a different historical perspective. Back in the day, I could whip through a Barroman CP calculation with paper, pen, and my trusty circular slide rule. Using a computer program for such would just slow me dowm. In 1978 I developed a 6-DOF model rocket modeliong and simulation program and used it in my Aero E. Senior PRoject. Thity years ago, my teammate, Dave Cook, rewrote my report for the NARAM-22 R&D competion audiance, and I presented it there. Dave later did some more programming work it and even sold a few copies, with my permission. However, it never really took off. Perhaps it was too far ahead of the market? I don't mean to suggest that my program was significant or even a precurser to RockSim or Open Rocket. I expect that several rocketeers likely wrote thier own simulation programs, even before mine; although, I think I was the first to present such to the NAR community through R&D competition reports. Rather, I suggest that the notoion that all we had 20 years ago were lousy candles and whale oil lamps until VanMilligan marketed the light bulb, er RocSim, is more whimsical than historical.

I have enot run OpenRocket or looked at the code yet. The think what bothers me the most is Java. If all the junior high and high school kids ar programming in Java, then I guess that is the way to go. Personaly, I prefer a procedural language like Fortran or C, over Object Oriented languages like Java. I'm also concerened about the note that OpenRocket uses a lot ofmemory and may even have a memory leak. Many students have old handed down computers, so let's not tell them OpenRocket is cool and free, you just need to upgrade your computer first.

I see over a dozen responses, so is the dominant subject on RMR by a wide margin. Thanks for your post.

Alan Jones
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I'm sure the same could be said about MS Office, Neo Office, Open Office etc
Damian
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Damian Burrin
UKRA 1159 Level 2 RSO
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David Utidjian schreef:

Very nice program. It does what I want it to do: calculate the stability of a rocket. IMO it's easier to use and it's free. Saves me $120 compared to Rocksim.
Roland
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Roland wrote:

Yep.
Though a bit of string and a whirl does it better - once you have built the rocket.
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While that technique works fine for an Estes Alpha it is rather difficult to accomplish with a rocket that is several feet long and masses 2+ kilograms. Also awkward to determine exactly where the CP is.
-DU-
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David Utidjian wrote:

You just need some space, and maybe a little muscle.
Also awkward to determine exactly where the CP

Move the string until the rockets doesn't fly - if that's too hard, and it can be, move it as you swing.
Takes two strings, the racer people will have details.

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I'm just a BAR, but in this new life my primary interest is motors. ;-)
In any case, after spending the past year perfecting motor designs, I am finally getting around to serious flight. I downloaded the demo of Rocksim, but I actually found OpenRocket easier to use. I have designed, built, and flown quite a number rockets with OpenRocket and they all perform as expected. I do not have a flight computer, so altitudes are just eyeballed. My time delays are quite accurate, however, and when I set them to apogee as predicted by the simulator, invariably they pop exactly at apogee. That is just about the coolest thing when launching a 100% scratch-built rocket for the first time. ;-) I launched one OpenRocket design in 30 MPH winds and it went perfectly straight up to 1500 feet. I had tuned for exactly 1.0 caliber of stability (CG exactly one BT diameter above CP) so I was fairly certain she wouldn't weathercock.
If you are looking to build a traditional 3FNC or 4FNC sub-sonic rocket, OpenRocket is all you need and it will do the job with aplomb. It does handle trans-sonic and super-sonic flight, but the algorithms have not been as thoroughly verified in flight testing. The features are limited, but it has all the basics covered, and when it does, it seems to do very well.
-g.
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A fellow FVR member presented this tool at one of our club meetings, at NIRAcon, and this spring at NARcon.
I finally gave it a try, and used it to design the A Cluster Altitude model that my daughter and I flew at NARAM-52 earlier this month. We both had great flights, and she ended up in 5th place and I got a 3rd. It was a pretty easy learning curve to get that first design cranked out, and I'll definitely be using it more in the future.
The latest version of OpenRocket will read all of the Rocksim data files, so you don't need to re-do all the existing designs that are already posted on the net.,
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