OpenRocket - "Hacking", Workarounds, Kludges & Cool Stuff

[manixFan]

Is there any way to get a list of motors "built into" OR?

You have to go to the source on Github:

https://github.com/openrocket/openr...iles/thrustcurves/thrustcurve.org/00INDEX.txt
Each motor has an entry that looks like this:

AMW_I195.eng

Manufacturer: Animal Motor Works​

Designation: WW-38-390​

Data Format: RASP​

Data Source: mfr​

Contributor: John DeMar​

From there you can clean up the file and get a list of only the motors motors (below).

But you'll notice there are many duplicates - it's basically the motors database from thrustcurve.org as downloaded several years ago. If you do follow the above link, click the 'Raw' button at the top of the list, or click the Copy icon to the right of the Raw button to copy the plain text to the clipboard and paste into either Word or Excel.


Tony


this is a text file of only the motors and their designation, the other text info has been removed:

Sample:
AMW_I195.eng Designation: WW-38-390
AMW_I195.rse Designation: WW-38-390
AMW_I220.eng Designation: SK-38-390
AMW_I220.rse Designation: SK-38-390
AMW_I223.eng Designation: 434I223-14A
AMW_I223.rse Designation: 434I223-14A

 

[Rocketjunkie]

Added all my RockSim design and motor folders to OpenRocket. Had to close OpenRocket and restart for the changes to show. Edited the .eng files to add new motors, then restarted OpenRocket.

 

[bad_idea]

In addition to small hacks like creating plugged motors where none exist from the manufacturer or creating motor files that include the mass and dimensions of an adapter they're nested in, it occurred to me that - while a horrible hack - motors were also a good way to vary masses around a rocket.

To that end, I created 999 fake 1mm x 1mm motors of negligible impulse, massing from 1 to 999 g. I can use them to simulate variable nose weights from one config to the next, or flying a chute release with big, high-flying motors but not small, low flying ones.

Despite putting these in "inner tubes" with ignition set to never, I get the "recovery device opened while motor still burning" error each time I use them. Altitudes look the same as conventional mass elements at the same place, so I think they're not actually being simmed as burning, though I've only had time to run a few tests so far.

I don't mind the warning message so long as the hack is working, but does anyone have a better or cleaner hack for varying masses from one configuration to another? (Could be there's something simple that just didn't occur to me yet.)

 

[rharshberger]

In addition to small hacks like creating plugged motors where none exist from the manufacturer or creating motor files that include the mass and dimensions of an adapter they're nested in, it occurred to me that - while a horrible hack - motors were also a good way to vary masses around a rocket.

To that end, I created 999 fake 1mm x 1mm motors of negligible impulse, massing from 1 to 999 g. I can use them to simulate variable nose weights from one config to the next, or flying a chute release with big, high-flying motors but not small, low flying ones.

Despite putting these in "inner tubes" with ignition set to never, I get the "recovery device opened while motor still burning" error each time I use them. Altitudes look the same as conventional mass elements at the same place, so I think they're not actually being simmed as burning, though I've only had time to run a few tests so far.

Does anyone have a better or cleaner hack for varying masses from one configuration to another? (Could be there's something simple that just didn't occur to me yet.)

Use the built in Mass Object......

 

[bad_idea]

Use the built in Mass Object......

The problem I am trying to solve is how I pick that mass such that it exists when I fly on a D motor but not a B, for instance. I don't see any option to add or eliminate masses based on the individual flight configuration. Is it possible to do that, but I've never found it?

 

[rharshberger]

The problem I am trying to solve is how I pick that mass such that it exists when I fly on a D motor but not a B, for instance. I don't see any option to add or eliminate masses based on the individual flight configuration. Is it possible to do that, but I've never found it?

Not that I am aware.

 

[bad_idea]

Okay, then fake motors are the way I'll do it for now. Simplifies my life enourmously at the expense of a spurious warning message in each sim.

 

[JoePfeiffer]

Okay, then fake motors are the way I'll do it for now. Simplifies my life enourmously at the expense of a spurious warning message in each sim.

What is the message?

 

[neil_w]

The problem I am trying to solve is how I pick that mass such that it exists when I fly on a D motor but not a B, for instance. I don't see any option to add or eliminate masses based on the individual flight configuration. Is it possible to do that, but I've never found it?

Submitted as a feature request, issue 1279: https://github.com/openrocket/openrocket/issues/1279

 

[bad_idea]

What is the message?

"recovery device opened while motor still burning" (This is the same message I got when mixing D12-0s with E12-8s, which prompted me to create a D12-P file to simulate wadding and taping the top of a D12-0.) Since the fake motor is set not to ignite (for I don't want the mass lost in flight) and has no ejection charge, and since recovery is set for first ejection charge, I'm wondering if there is something I've missed in creating the motor files. I'll do some more tinkering later on. I have confirmed with rocket and motor mass plots that the mass stays as expected, dropping the mass of propellant in the actual motors during their burn but retaining the mass of the fake motor.

Since I've been testing this on a more complex design than is needed to demo the utility of the hack or diagnose the warning message, I'll try to upload a simpler example later on.

Submitted as a feature request, issue 1279: https://github.com/openrocket/openrocket/issues/1279

Thank you, Neil. If no one knew a simpler way to accomplish this, I had intended to submit a feature request to add configurable mass elements to the configurations created in the Motors & Configuration tab, but I didn't want to pile-on during the beta so was going to submit it after release. I've also been trying to learn the code so as to figure out how this could be added, but it's been very slow going so far.

This would go very well with issue 1053 to add chute release support, at least for my use of the chute release, where on some rockets I use it for larger motors but I don't with smaller motors. My other - main - use case is to change out nose weights to tune stability when flying different motors. But it would also be useful for cameras, trackers, etc., anything that may be on one flight but not the next.

I have been handling this either by overriding mass from one sim to the next - copying down the results so as to retain them when I revert to the original mass, or by keeping two (or more) separate ork files up to date with the same changes. The fake motors are an attempt to be able to manange these different flight configurations in a single file and without all the back and forth.

In the very long run, it would be ideal to be able to create and sim a more modular rocket in the same file, e.g., to fly with an avbay and and extra body tube in one configuration and not in another - or even to fly a sustainer with a booster in one configuration and on its own in another - but I realize that would be a much larger effort than variable mass elements would be (and I'm sure even variable mass elements won't be simple when all is said and done).

 

[waltr]

I have been handling this either by overriding mass from one sim to the next - copying down the results so as to retain them when I revert to the original mass, or by keeping two (or more) separate ork files up to date with the same changes. The fake motors are an attempt to be able to manange these different flight configurations in a single file and without all the back and forth.

I have been handling different mass, as in Altimeter or not by adding a 'mass object' in the correct placement. Then use the 'comments' tab to record down the options and manually change the weight of the mass object as needed.
This method has been working fine for me.

 

[bad_idea]

Yes, that is what I have been doing all along too, until yesterday evening. It works, but flying the same rocket in many different configurations, it can become a bit of a chore, especially when trying to optimize during design.

 

[neil_w]

Yes, that is what I have been doing all along too, until yesterday evening. It works, but flying the same rocket in many different configurations, it can become a bit of a chore, especially when trying to optimize during design.

In general, any part of the program that requires a "hack" is a deficiency in the program. Calculating and managing nose weight requires too much effort right now. It is not particularly easy to remedy in a good, general-purpose way, and we have a long list of feature requests to weigh it against, but for sure it would be our objective to make this better if we can. At some point.

 

[bad_idea]

The formidable list of things y'all are already working on is why I hadn't opened a feature request for this some time ago. It was always possible to handle manually, and there were many more critical issues, even before I started exploring the fake-motor workaround.

 

[JoePfeiffer]

This is one of those things that, the more I think about it, the more I like it and the bigger it gets. Being able to handle a more modular rocket design is something I'd like a lot; I'd like to be able to put together one of my standard GPS-carrying nose cones, standard altimeter bays, and standard fin cans with a couple of pieces of body tube.

NOT going to think about before final release of the new version, and want to make sure the actual plan is also modular (ha ha) so we don't go down another seven year rabbit hole like with pods (which are absolutely worth it in the end, but I really wish we'd found a way to have incremental releases while they were implemented).