OpenRocket Motor DB

Attached is the screen shot of my OpenRocket motor selection. It's limited to Aerotech 38mm. There are 3 J350 motors listed. The data isn't consistant as to thrust, size etc. When you use Show Details, one of the files says it's from 1998. The other two don't have any notes at all.

Is there any way to update or clean up the motor database to eliminate old or outdated motor listings?

There is a way.

Download 7zip and install it. Open the OpenRocket .jar file. Navigate to datafiles\thrustcurves and then copy and paste the .eng or .rse files into that folder. You can add updated files for existing motors or add files for new motors. If a motor you add already exists, there will be two shown at that point.

It works on or 14.11 but may have issues with 15.03. Perhaps they'll fix it soon.

Looks like we have duplicate thrustcurve sets for this motor. Likely this happened when thrustcurve.org did some changes and I wasn't paying attention. If you see any more like this, let me know.

Kevin

kruland said:

Looks like we have duplicate thrustcurve sets for this motor. Likely this happened when thrustcurve.org did some changes and I wasn't paying attention. If you see any more like this, let me know.

Kevin

Click to expand...

A lot of the motors have duplicates like the J350 does. A quick look and I would estimate at least half have double or triple entries.

Kruegon said:

There is a way.

Download 7zip and install it. Open the OpenRocket .jar file. Navigate to datafiles\thrustcurves and then copy and paste the .eng or .rse files into that folder. You can add updated files for existing motors or add files for new motors. If a motor you add already exists, there will be two shown at that point.

Click to expand...

Actually you don't have have 7zip, once it's installed, those folder are already created and I've added motors by adding the .rse files before (the .eng files didn't work in 14.11). What I'm trying to do is delete the old motors that are already in the program, not ones that I added.

Handeman said:

Actually you don't have have 7zip, once it's installed, those folder are already created and I've added motors by adding the .rse files before (the .eng files didn't work in 14.11). What I'm trying to do is delete the old motors that are already in the program, not ones that I added.

Click to expand...

Yeah that was brought to my attention. And apparently you can't add the files normally that way anyway. I forgot I had the developers version of Java.

I've worked it back and forth. Without a developers setup to edit the entire jar you can't remove the existing motors. I tried removing the entire thrustcurve database, and OR won't launch without it. Just hangs. And the existing database is encoded when compiled, so you can't edit them out either. It's a quandary. What I did was rework ALL my AeroTech motor files. I broke them down and recompiled them by motor case size. Then named the files AeroTech_XXX.eng where XXX is the motor case newtons. Then OpenRocket sees them and shows them in the motor list as such. That way I can select only those AeroTech motors I want by diameter and case size. It's a little work, but it's working very well. I can upload them here if you want.

I try desperately to remember that OR is free and is someone's gift to our community. So while I refuse to ever belittle the program, I do wish that certain changes would be made to it. The engine database is one of them for the exact same reason you have here. Another is the tailcone formulas. You can't attach fins to a tailcone. It severely affects the ability to sim a rather large number of LPR rockets. The V2 specifically. But also several others. Hopefully the program will grow and expand as we all support it. I'd even be willing to pay for it if they'd put the work into it to make it fully rival RockSim. And they're getting close.

Kruegon,

You just hit on something I was going to post about within the hour, the V2 and OR. Since you seem to have some experience with it, can you tell me if I'm simulating a V2 correctly in OR? Here's what I did:

Like you said, you can't attach fins to a tailcone in OR, so I set my fin tabs to "0". This gave me the fin configuration I needed, but my CP is fairly far forward for a 2.6" Wildman V2 kit, so much so that I'm having to add up to 6oz of noseweight to make her close to stable. Is this the best way to get fins on a V2 in OR, or should I be looking at some other way?

Thank you! Sam

What I did was to attach the fins to the body tube. Then I adjusted them aft until I had them properly aligned with tailcone. Then I adjusted the TTW to extend to the motor mount. It appears to have corrected the CG and CP properly.

I'll give that a try, and thank you! Sam

Kruegon said:

Hopefully the program will grow and expand as we all support it. I'd even be willing to pay for it if they'd put the work into it to make it fully rival RockSim. And they're getting close.

Click to expand...

I think "they" is more like "he." Last I heard, there is only one semi-active developer of the code. If you dream it, you may have to step up to the plate and do it yourself. The "free" part of Open Source means "freedom", not price.

I thought there were two or three guys working on it the way I read it. But it's still a massive boon to our hobby. And I'm not going to make demands on it, just voicing what I hope to see one day soon. Like I said, if it gets a little farther along, I'd be happy to pay for it to use it. Just not the 100.00+ RockSim runs.

Kruegon said:

I thought there were two or three guys working on it the way I read it. But it's still a massive boon to our hobby. And I'm not going to make demands on it, just voicing what I hope to see one day soon. Like I said, if it gets a little farther along, I'd be happy to pay for it to use it. Just not the 100.00+ RockSim runs.

Click to expand...

Nothing is stopping the guys from selling OR (it is permitted under GNU). But, it is so far along that putting a price tag on it now may damage the kumbaya vibe that everybody feels around this open source software. At what price would you be happy - $20, $50, $75? It would be an interesting discussion.

I am afraid that as soon as OR is no longer free, many will start to loudly complain that $xx.xx is "too much", regardless of the price. This is a damn expensive hobby, and most have no problem plopping down hundreds and thousands of dollars in parts and motors. However, they then think the software should be free of cost. I don't get it.

I'd see $39.95 as a very viable market price. But it needs to have a few outstanding issues corrected before I'd put cash money behind it.

However, the general public would react poorly to it having any price. So although it's worth the 40 in my view, perhaps start slow at $24.95.

Kruegon said:

I'd see $39.95 as a very viable market price. But it needs to have a few outstanding issues corrected before I'd put cash money behind it.

However, the general public would react poorly to it having any price. So although it's worth the 40 in my view, perhaps start slow at $24.95.

Click to expand...

I think $125 for Rocksim or similar is very reasonable for what you get. RS and OR are a CAD program + Engineering solver in one package. If you tried to buy something like this from say, AutoDesk, you would be in to the tune of a couple grand. Not building prototypes and ensuring safe flights through simulation is easily worth $125 after just one scratch build. However, hobby rocketry is an extremely niche application populated by cheapskates who build models from other people's garbage (Just joking, guys. Calm down. :wink: ), so the price needs to reflect that, too.

This time around there were a number of developers working on OpenRocket. I am happy to say, it's been the biggest participation to date.

As for charging, it is true that GNU does not prohibit charging as long as the source is freely available. However, Sampo has made it clear over the years that even if there are some pay-per avenues it will always be free (as in beer) somewhere. However, if you do think the software is worth something, then there are ways to donate to the development. If you go to the OpenRocket Home Page there is a "donate now" button where you can send along any amount you think is appropriate. I have never asked how much money has been donated this way, but I would think it's in the 10s of dollars! Donations will go towards documentation necessary to further the product.

There are other ways to give to the OpenRocket community - for example listing exactly which motors you believe are duplicates would go a long way to helping us out. You can always answer questions on the forum, or contribute videos or how-to articles. Since Tube Fin simulation is really new, having good scientific experimental data would be very helpful. Finally if you are a java developer you can join in the fun.

How did I get started doing OpenRocket development? I thought the software was valuable but didn't quite do what I wanted, so I volunteered to contribute various bits including the Android program, more complex flight configurations, simulation of booster stage recovery (for HPR staging), the component library, tube fins, etc.

Kevin

Buckeye said:

I think $125 for Rocksim or similar is very reasonable for what you get. RS and OR are a CAD program + Engineering solver in one package. If you tried to buy something like this from say, AutoDesk, you would be in to the tune of a couple grand. Not building prototypes and ensuring safe flights through simulation is easily worth $125 after just one scratch build. However, hobby rocketry is an extremely niche application populated by cheapskates who build models from other people's garbage (Just joking, guys. Calm down. :wink: ), so the price needs to reflect that, too.

Click to expand...

I do not disagree that it's worth a decent price. The simple fact that it has the ability to reduce poor flight profiles and stop accidents before they happen is enough. Some of us old farts learned to design safely by flying rockets 360°. At once lol.

kruland said:

However, if you do think the software is worth something, then there are ways to donate to the development. If you go to the OpenRocket Home Page there is a "donate now" button where you can send along any amount you think is appropriate. I have never asked how much money has been donated this way, but I would think it's in the 10s of dollars! Donations will go towards documentation necessary to further the product.

There are other ways to give to the OpenRocket community

How did I get started doing OpenRocket development? I thought the software was valuable but didn't quite do what I wanted, so I volunteered to contribute various bits including the Android program, more complex flight configurations, simulation of booster stage recovery (for HPR staging), the component library, tube fins, etc.

Kevin

Click to expand...

As far as I can tell right now, the biggest things for me in OR are the tailcone issues and the motors.

I'd love to be able to completely customize the motor db. I only fly Estes and AeroTech motors. It's most probable that they are all I ever will fly. In RockSim, I deleted every motor file completely and compiled the most up to date database of currently available motors I could find. I broke them down by case size and made it stupidly easy to see what case the motor matches. Now, only motors I'll actually fly appear in it. But it's so old. If I could wipe out and reload the OR database, it would definitely grab my attention.

The tailcones in OR cannot have fins attached. That's a problem for a lot of the Estes and true scale rockets. While I have no idea how to correct it (I'm not a programmer), it is something I'd like to see. I haven't played with the parts database extensively yet, but I will be very soon.

Kruegon said:

... In RockSim, I deleted every motor file completely and compiled the most up to date database of currently available motors I could find. ...

Click to expand...

Wise move. I have done the same, only to find out in one case that the older motor file was the more accurate one. Grrrr...

IMO, the motor file proliferation and errors are the biggest threat to the simulation part of this hobby, because they affect each and every flight. We can all give feedback for corrections to kruland and thrustcurve, but it seems to be a bigger challenge than that.

Buckeye said:

Nothing is stopping the guys from selling OR (it is permitted under GNU). But, it is so far along that putting a price tag on it now may damage the kumbaya vibe that everybody feels around this open source software. At what price would you be happy - $20, $50, $75? It would be an interesting discussion.

I am afraid that as soon as OR is no longer free, many will start to loudly complain that $xx.xx is "too much", regardless of the price. This is a damn expensive hobby, and most have no problem plopping down hundreds and thousands of dollars in parts and motors. However, they then think the software should be free of cost. I don't get it.

Click to expand...

That is just it. I am a Rocksim guy. I have used ever version since v4. I have not problem paying for software within reason. I, unlike the vast majority of you, have had my hands on Rocksim Pro. Really a heck of a program, but I cannot pay the ridiculous price tag. If it cost $200-250 I would snag it.

Open Rocket has been free. If you make it a for pay software people will likely balk period. Some will stay with their current free version and some would upgrade. The trick is to determine the right price.

Buckeye said:

Wise move. I have done the same, only to find out in one case that the older motor file was the more accurate one. Grrrr...

IMO, the motor file proliferation and errors are the biggest threat to the simulation part of this hobby, because they affect each and every flight. We can all give feedback for corrections to kruland and thrustcurve, but it seems to be a bigger challenge than that.

Click to expand...

Well, I can speak to this as the Editor of Thrustcurve. To create the files is a very manual process, and yes, occasionally errors are made. We try to fix them asap, but the reality is that this is my hobby too- not a job.

Now, where do errors come from other than a typo type of thing. Well, let me list a few for you. I get my info directly from testing orgs. Let's consider the slight differences in the way they report/measure things. TMT reports propellant weight the difference between ore burn and post burn. From a simulation standpoint this makes total sense. In reality, this may over list the propellant if you were to look at the manufacturers info as you might burn some casting tubes etc.

Then, you can throw I the normal and allowed variation in motors performance. Look it up, but having a ten percent difference motor to motor is possible.

In a motor file, how do you list a motor length? It it the casing length, is it the length of the motor with front and rear closures? Is it the total length including nozzle and forward closures?

Another issue that I think is prevalent is inaccurate simulations. Is your file really accurate? Masses, dimensions, and finish. Have you adjusted your sim for temperature, humidity, wind, and launch angle?

Also, at least for Rocksim and Open Rocket, they are based on Barrowman. If you have not read it there are some qualifications on its use. One commonly exceeded is that Barrowman was intended for subsonic. Anything beyond that is use at your own risk, so to speak. I have, as have others, found that both will work fine up to about Mach 1.5 or so. Again though, the farther you get from Mach 1 the more error you are likely to experience.

So, all that said I think that if you have accurate sim files corrected for actual launch conditions you should be happy if you are within 5-10%.

Do not get me started on dealing with turbulence and base drag in short fat rockets.

Kruegon said:

I'd love to be able to completely customize the motor db. I only fly Estes and AeroTech motors. It's most probable that they are all I ever will fly. In RockSim, I deleted every motor file completely and compiled the most up to date database of currently available motors I could find. I broke them down by case size and made it stupidly easy to see what case the motor matches. Now, only motors I'll actually fly appear in it. But it's so old. If I could wipe out and reload the OR database, it would definitely grab my attention.

Click to expand...

You can actually "hide" all the motors you don't use. When you go to the motor selection dialog (in OR 14.03 and later), there is a list where you can select the visible manufacturers. Uncheck the ones you don't use. OR will remember which ones you've checked the next time you run the program. For me, I only show Quest, Estes, Aerotech, CTI, and Loki.

Kevin

kruland said:

There are other ways to give to the OpenRocket community - for example listing exactly which motors you believe are duplicates would go a long way to helping us out.
Kevin

Click to expand...

kruland said:

You can actually "hide" all the motors you don't use. When you go to the motor selection dialog (in OR 14.03 and later), there is a list where you can select the visible manufacturers. Uncheck the ones you don't use. OR will remember which ones you've checked the next time you run the program. For me, I only show Quest, Estes, Aerotech, CTI, and Loki.

Kevin

Click to expand...

I actually did hide the motors I didn't want. I set it up so it only showed 38mm Aerotech motors. There are 50 different motors listed and there are 15 duplicates, or about 30%:

G67R 111 Total Impulse (TI) 106mm long
G67R 110 TI 106mm long

H45 332 TI 203mm long
H45W 289 TI 194mm long
H45W 320 TI 191mm long

H73J 180 and 154 mm long
H73J 188 TI and 152 mm long

H112J 261 TI 202mm long
H112J 281 TI 191 mm long

H242T 234 TI 154mm long
H242T 244 TI 152mm long

I132W 595 TI 335mm long
I132W 640 TI 330mm long

I161W 333 TI 191mm long
I161W 334 TI 202mm long

I195J 445 TI 297mm long
I195J 473 TI 298mm long

I211W 431 TI 240mm long
I211W 440 TI 250mm long

I225FJ 350 TI 202mm long
I225FJ 371 TI 240mm long

I284W 554 TI 297mm long
I284W 591 TI 298mm long

I357T 341 TI 202mm long
I357T 356 TI 203mm long

I435T 556 TI 297mm long
I435T 596 TI 298mm long

J350 669 TI 337mm long
J350W 700 TI 340mm long
J350W-L 650 TI 337mm long

J825R 928 TI 479mm long
J825R-M 929 TI 478mm long

Most of these probably wouldn't make much difference in a simulation, but based on the difference in Total Impulse from some of them, it could make a significant difference.

markkoelsch said:

Well, I can speak to this as the Editor of Thrustcurve. To create the files is a very manual process, and yes, occasionally errors are made. We try to fix them asap, but the reality is that this is my hobby too- not a job.

Now, where do errors come from other than a typo type of thing. Well, let me list a few for you. I get my info directly from testing orgs. Let's consider the slight differences in the way they report/measure things. TMT reports propellant weight the difference between ore burn and post burn. From a simulation standpoint this makes total sense. In reality, this may over list the propellant if you were to look at the manufacturers info as you might burn some casting tubes etc.

Click to expand...

I can appreciate the conflicts you face with the data and assumptions. It isn't easy. Thanks for weeding through it.

Another issue that I think is prevalent is inaccurate simulations. Is your file really accurate? Masses, dimensions, and finish. Have you adjusted your sim for temperature, humidity, wind, and launch angle?

Click to expand...

All true, but these are things the user can easily adjust or correct in his personal simulation file. The motor file, not so much. The user usually can't or won't investigate the accuracy of the thrust curve.

I have done simplified variation studies by putting simulation parameters (including those you mention) through some typical, as well as extreme, ranges. The motor file still generates the most difference in the result. I am sure that if one did a proper Monte Carlo or ANOVA study, the motor data would be the most significant parameter every time.

So, all that said I think that if you have accurate sim files corrected for actual launch conditions you should be happy if you are within 5-10%.

Click to expand...

+1 to that. Anything more, and you are just chasing your tail.