Wrasp file for the AT J 575 FJ?

[Fore Check]

Anyone know where to get a wrasp file for the 9-grain AT J575-FJ reload? Thrustcurve.org doesn't have one. In fact, I can't find a thrust curve for it at all (perhaps I'm not looking in the right place?)

Even if I did find the thrust curve, I'm not sure I'd know how to generate a wrasp file myself (but I'd try if somebody would explain it to me.)

Thanks!

 

[Fore Check]

Well, I think I figured out how to generate an engine file with EngEdit.

I also found the thrust curve for the J575FJ on AT's website.


Then I built a file for it in EngEdit. The curve I inputed looks a *HECK* of a lot like the real thing on AT's site. The cert document (On AT's site) indicate:

Motor:          J575FJ
Burn Time:      1.34 sec
Total Impulse:  798.116 NS
Max Thrust:     839.5 N
Avg. Thrust:    593.95 N

]

My results, after building a thrust curve from scratch, are:

Motor:          J575FJ
Burn Time:      1.34 sec
Total Impulse:  796.033 NS
Max Thrust:     840.689 N
Avg. Thrust:    594.054 N

The thrust curve looks dad-gummed close. I like it. I think I've done good enough to be confident in the accuracy of my sims.

Problem is, I built the engine as an added motor to the already large Aerotech.rse file. Anyone know of a way to export it as an individual motor file so I can share it with y'all?

 

[MarkM]

Problem is, I built the engine as an added motor to the already large Aerotech.rse file. Anyone know of a way to export it as an individual motor file so I can share it with y'all?

The only way I know is to open up EngEdit and the Aerotech.rse file. Then, under the file menu select SPLIT and select your options & hit OK. This will then parse out every engine in the file as a separate.rse file (the Aerotech.rse file remains intact as is). Unfortunately, I haven't figured out a way to parse out only a single engine.

 

[Fore Check]

The only way I know is to open up EngEdit and the Aerotech.rse file. Then, under the file menu select SPLIT and select your options & hit OK. This will then parse out every engine in the file as a separate.rse file (the Aerotech.rse file remains intact as is). Unfortunately, I haven't figured out a way to parse out only a single engine.

Ok...

That didn't work.

Not your fault, dude.

No matter what I did, EngEdit said whatever space I was trying to save the "split" files to was an invalid directory or some such. I hate computers sometimes.

 

[Fore Check]

Well now - after a night's rest and a do-over on splitting that AT file, I succeeded!

I had to convert the *.rse file back to a *.eng file so I could upload it here, which means you will want to change the "type" from "unspecified" to "reloadable." That bit of data is lost in translation from RSE to ENG, among other things too (but I don't think those other things affected this file.)

Anyone want to critique this before I get so bold as to submit it to ThrustCurve.org?

The link to the thrust curve on AT's site is here: https://www.aerotech-rocketry.com/c.../reloadable/rms-38_1080/j575fj-m_tra_cert.pdf

View attachment AT J575FJ.eng

 

[cls]

the eng and rse files are text, just open with notepad and cut & paste to a new file.

 

[Fore Check]

Thanks.

I adjusted the RSE file a smidge and sent it in to thrustcurve.org

I find it easier to build the file a bit differently. Isn't it great that we have several methods to acheive the same goal?

 

[darkhelmet]

The burn time is defined between the 5% of peak thrust points, not to the end of the burn. Your "tail" on the curve should be longer such that the published burn time matches the point where the thrust tapers to 5% of peak.

Average thrust is also defined between the 5% marks, not over the whole curve. This usually doesn't make much difference unless there's a regressive taper at the end of the curve, like this one has.

The TMT curve appears to have significant noise in the data (which may bias the motor specs), and also is truncated at the end (possibly due to an offset error with their test stand).

 

[gregzo]

Search for past posts for what you want...

https://www.rocketryforum.com/showthread.php?s=&threadid=30131
Good Luck

 

[Fore Check]

Thanks, Gregzo. I *did* do a search and didn't turn up anything relevant. Perhaps I entered search parameters that were a bit off?

On a related note, I've tried searching for stuff that I know is out there (since the update) and can't find that stuff either.