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?
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.
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,
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
* 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.
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.
As we enjoy great advantages from the inventions of others, we should
be glad of an opportunity to serve others by any invention of ours;
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,
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
I see over a dozen responses, so is the dominant subject on RMR by a
wide margin. Thanks for your post.
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
I'm just a BAR, but in this new life my primary interest is
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.
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.,
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.