# Open Rocket vs RockSim

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#### Oliver

##### Well-Known Member
As for the user interface if you look at the other software called SpaceCad
it has also a very similar user interface. So who copied from each other?
Regarding SpaceCAD, let me mention that this software was initially developed by Andreas Firnau and me, distributed by my former company FlyTech, way back in 1990 under the previous name "SpaceCalc+" (later continued by Andreas under his own label SpaceCAD). If I remember right, at this time only some Basic program listings existed along with a Mac software from Estes. I think that SpaceCalc+ was even the first commercial program for PC computers (along with a C64 version). And the first one with the feature to add parts from a part database to simplify the construction of a model rocket.

So from a historic background, there was no way that SpaceCAD could copy from any other related software because there was none. I would even say that ideas such as the parts database was copied by other programs later (although I do not have a problem with it since makes sense for every software).

But back to the topic, a fact I like is that - thanks to the great work of Boris - OpenRocket is available in many different languages such as French and German. This may not be an issue in the US or the UK, but in most other countries.

Greetings,

Oliver

Hi,

I created a feature comparison on the OR wiki. I know I'm biased, but I tried to make a fair comparison of the features. If you think something is misrepresented or some feature is missing, let me know.

https://sourceforge.net/apps/mediawiki/openrocket/index.php?title=Feature_comparison

Cheers,
Sampo N.
The staging support in OR has a significant missing feature, and that is being able to simulate stage separation at a time that is different from upper stage ignition. There is a big altitude advantage, especially for high altitude flights, of being able to have the sustainer coast for a significant duration before ignition. As far as I can tell, there isn't a way to simulate this in Open Rocket. Rocksim's interface for controlling the separation time separately from the ignition time is clumsy, but at least it's possible to do. So for now at least, I'd rank the OR staging support behind that of Rocksim.

What I'd love to see is a more complete and intuitive interface for controlling all the rocket events based on altitude, speed, time, etc. the way you can with full-featured altimeters. Perhaps control of those functions should be together in one place with the recovery events.

Oh, and one area where you're too modest in the comparison is with the supersonic accuracy. I have found that, especially for rockets with a Von Karman nosecone, the accuracy for supersonic flights is much better than Rocksim's, at least recently (there must have been a change, because a couple of years ago, OR was seriously under-predicting altitude for Mach 2 flights). The leader in accuracy is RASAero, but there's a lot of missing functionality in that software compared to RS and OR.

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I'll give you that, Alby. There is tension in the system. RS needs to step up the game to justify the price.
Indeed. And after communicating known bugs back to Apogee both directly and in the forums, and then being asked to pay for upgrades that don't address these bugs, I don't feel that their business model is working for me. I'm happy to pay for software when the support is there and bugs get fixed.

#### davdue

##### Well-Known Member
TRF Supporter
I know having a parts DB would be useful, but since I personally live in Finland and don't really have ready parts available, it hasn't been a high priority for me. I've got some ideas for it though. If someone wants to help out a bit...
Even if it didn't have a parts database to start with it would great to be able to save components. Then we could share them as well on TRF. For the most part you only need a few parts like BT's, MMT, couplers, eyebolts, etc.

#### Rocketjunkie

RasAero is by far the most accurate for high performance rockets of any of the software I've used. (RockSim, OpenRocket, WinRoc, RASP, and my own.)

#### troj

##### Wielder Of the Skillet Of Harsh Discipline, Potent
Something I've not seen mentioned in this is that it's beneficial to the hobby for both programs to exist, and have a healthy user base.

Why? Because it encourages them to keep up with each other in terms of feature set.

In the end, we, the rocketry community, win, by virtue of having better software available to us.

-Kevin

#### Sampo

##### Well-Known Member
Hi,

The staging support in OR has a significant missing feature, and that is being able to simulate stage separation at a time that is different from upper stage ignition. There is a big altitude advantage, especially for high altitude flights, of being able to have the sustainer coast for a significant duration before ignition. As far as I can tell, there isn't a way to simulate this in Open Rocket. Rocksim's interface for controlling the separation time separately from the ignition time is clumsy, but at least it's possible to do. So for now at least, I'd rank the OR staging support behind that of Rocksim.

What I'd love to see is a more complete and intuitive interface for controlling all the rocket events based on altitude, speed, time, etc. the way you can with full-featured altimeters. Perhaps control of those functions should be together in one place with the recovery events.
I wasn't even aware this was being done. I'd still consider this rather rare and advanced functionality on the scale of "Simple things should be easy, hard things should be possible."

One option would be to have a dedicated stage separation condition. What would be reasonable events for stage separation? I'm thinking upper stage ignition, current stage burnout, current stage ejection charge, never and launch (each with an optional +NN seconds). The default would be upper stage ignition, as it is currently.

An alternative approach would be simulation extensions. I've got some ideas on making "plugins" simpler to use and configurable. This could be used for more advanced event management, such as simulating an arbitrary flight computer.

Oh, and one area where you're too modest in the comparison is with the supersonic accuracy. I have found that, especially for rockets with a Von Karman nosecone, the accuracy for supersonic flights is much better than Rocksim's, at least recently (there must have been a change, because a couple of years ago, OR was seriously under-predicting altitude for Mach 2 flights). The leader in accuracy is RASAero, but there's a lot of missing functionality in that software compared to RS and OR.
Thanks for the info. I've been unable to directly compare results against supersonic flights, only against published wind tunnel data. The latter suggests an increasingly poor Cd result, with an error starting from about 20% at Mach 2 up to 50% at Mach 4. Maybe that's not that bad after all.

Cheers,
Sampo N.

Hi,

I wasn't even aware this was being done.
I'm pretty sure that most high powered staged flights have at least a few seconds between stage separation and upper stage ignition, to prevent scorching of the booster, increase altitude, or just for effect. Some people set up their rockets so that drag will separate the stages immediately after booster burnout.
I'd still consider this rather rare and advanced functionality on the scale of "Simple things should be easy, hard things should be possible."

One option would be to have a dedicated stage separation condition. What would be reasonable events for stage separation? I'm thinking upper stage ignition, current stage burnout, current stage ejection charge, never and launch (each with an optional +NN seconds). The default would be upper stage ignition, as it is currently.
Most people doing high-powered airstarts will perform staging separation at burnout or burnout + time. Most upper stage ignitions are based on time, but for safety reasons, the idea of igniting the upper stage based on altitude is starting to catch on.
An alternative approach would be simulation extensions. I've got some ideas on making "plugins" simpler to use and configurable. This could be used for more advanced event management, such as simulating an arbitrary flight computer.
That would be awesome. I would be happy to work with you on reproducing the Raven's deployment options. It would be cool if you could open up a Raven deployment setting config file in Open Rocket, and then assign events in Open Rocket like staging, upper stage ignition, apogee and main deployments to the Raven's 4 output channels.

https://www.featherweightaltimeters.com/FIP.php
Thanks for the info. I've been unable to directly compare results against supersonic flights, only against published wind tunnel data. The latter suggests an increasingly poor Cd result, with an error starting from about 20% at Mach 2 up to 50% at Mach 4. Maybe that's not that bad after all.

Cheers,
Sampo N.
For a Mach 2 flight to 32,000 feet last October, RASAero predicted 31,800 feet, Rocksim predicted 22,020 feet, and Open Rocket predicted 29,930 feet after I adjusted all the sims for the actual pre-flight mass.

#### Sampo

##### Well-Known Member
Learn something new every day. I haven't thought of how high-power staging is performed, so it hasn't been taken into account OR.

I'll have to see if I have some time to implement this - it shouldn't be that hard to make the separation event configurable. The fully configurable event management will have to wait until the plugin system is better fleshed out.

Cheers,
Sampo N.

#### Alby

##### Well-Known Member
Learn something new every day. I haven't thought of how high-power staging is performed, so it hasn't been taken into account OR.

I'll have to see if I have some time to implement this - it shouldn't be that hard to make the separation event configurable. The fully configurable event management will have to wait until the plugin system is better fleshed out.

Cheers,
Sampo N.

This is why Open Source Rocks.

#### El Phantasmo

##### Well-Known Member
This is why Open Source Rocks.
This isn't why OSS rocks. This is and example of excellent customer service. OSS's strengths lie in transparency (access to source code) and ability for others to use that code (within various licensing agreements).

#### Buckeye

##### Well-Known Member
TRF Supporter
This isn't why OSS rocks. This is and example of excellent customer service. OSS's strengths lie in transparency (access to source code) and ability for others to use that code (within various licensing agreements).
+1 to that. I suspect that Sampo's excellent service would be equally visible in a commercial product.

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#### bdureau

##### Well-Known Member
Hello
For those of you who are not yet convinced on how easy it is to design a rocket with OpenRocket here is a video that one friend from Tripoli France did to demonstrate basic fonctionalities

Again thanks a lot Sampo for making it free
Regards
Boris

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#### Inerax

##### Well-Known Member
I use open rocket and dont have to change the design every time....

is there something i should be changing?

Thank you Sampo!

#### Rocketbuilder

##### Well-Known Member
Personally, I would rather guess than pay \$123.60 for RS. OR works just fine for me. For all the people who complain about not having a parts database, every time you make an new engine mount or nose cone or tube, etc, just copy and paste it into a document labelled parts database. I'm going to start doing this soon. I think you might have to add some parts as a new stage but it should work.

Thanks Sampo, OR makes all of my scratch builds possible!

#### thobin

##### Well-Known Member
OK i just talked my genius programing friend, who will scratch his chin for a second and have it programed in about an hour. For Open Rocket.

I asked him to work on the fins and/or pods to be added to the fins attached to the air frame. (That is if it is not being worked on.) There are other things I could ask him to do to but his time is limited so any suggestions?

TA

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#### thobin

##### Well-Known Member
I'm wanting to see in OP is the Tube fins, Ring-tail fins, External pods done the most. and some printing issues and exporting to a drawing program format of some kind.

TA

#### astropilot

##### Member
IMHO the most important issue I would like to see reolved would be external pods, tube fins. The rest I can live with...

#### thobin

##### Well-Known Member
Well he is not done with the pods issue yet, but you can now import a bitmap file for the fin shape in the free form section. I haven't seen it work yet but he did call me and told me that its done. And he has moved on to bigger and greater sections of OP.

TA

#### Zonie

##### Well-Known Member
Runs natively on a Mac. Just double click on it.

It had some trouble making out the entire oop estes Viper rocsim file.

#### rockets4kids

##### Well-Known Member
Well, technically it doesn't run natively on a Mac. It still runs inside of a JVM.

Mac's are nice in that you can just click on the JAR file and the rest happens automagically. ;-)

#### thobin

##### Well-Known Member
Well A new version of Open Rocket is out some new upgrades one of which my friend did. Check it out.

TA

#### SteveA

##### Well-Known Member
I have both and what I like about Rocksim are the drop-downs for parts. Yeah, it has lots of bells and whistles, but I primarily purchased it in multiple licenses because I would like to expand my rocketry classes next year to a design class and I thought that Rocksim would be easier to teach in a short amount of time with all the little extras that Open Rocket does not have. That said, I do like both for various reasons.

What I would like to see with Rocksim is an expanded parts list to include all Estes BTs and more Semroc parts. (Not that there is anything wrong with those listed.) And have it available as an upgrade that you can download without buying a new program.

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#### JMGrant

##### New Member
The reason I was directed to this particular thread, I am looking for a way to design a rocket that comes down in two or more parts.

Specifically, I want a single stage, single Estes style motor rocket to launch, then separate at ejection into a payload section and "booster" section that return independent of each other.

The payload would use a parachute, while the booster uses a streamer.

I have decided that I want to go HP, and my 13 year old son is wanting to do TARC, hence my "new" needs. But I haven't figured out how to do that in OR, and I don't know if RS 9 can do it (I have d/l'd the demo, but I'm looking for an answer before I start the RS clock).

Also, I really like the idea of a customizable dB, exporting to RS, and especially the idea of flight computers.

I'll continue my search, but I just have to comment on how some folks simply can't live without abusing each other; I have learned that there is no one perfect solution to any situation, sometimes you need choices.

For the record, I have a copy of RS 6, which I still fire up now and again, but until just recently, I almost exclusively use OR for everything, including the after school program I instruct (5th through 8th grade). OR is well within their price range and capabilities.

There is also something to be said for commercial software, but when you finally get down to sustainability, both are as vulnerable as the other, except that OS can be assumed by a thoughtful community if the need exists... and, all things considered, that's the power of OS, IMHO.

#### Pat_B

##### Well-Known Member
Apogee has a TARC video section on their site that explains how to have separate components come down under their own recovery devices.