Discussion in 'Propulsion' started by kweaver, Jul 4, 2018.
Question came up today about the AeroTech, 38mm J520 status?
Anyone know ?
the Aerotech J520 is certified for use in a plugged only configuration. There was too much variation in the delay times so it was not certified to use a delay. This means you can fly this motor, but it has to use electronics for deployment, or I suppose have other motors provide deployment if a part of a cluster. The cert letter is attached.
Yeah, pretty much what Mark said. Last I recall Aerotech was looking to dial in the delay using some wizardry and ultimately get it certified with an adjustable delay.
That is the case. The delays for this motor are still an issue, and are still being worked on.
So I gather that the motor is currently not shipping?
Any idea when it will be available?
No one has it in stock that I can find and aerotech still has it listed as pending on their order form. It is apparently labor intensive due the high number of small grains needed for a non-hazmat "J" (in the 1080 case). Since aerotech is way behind in filling current orders I would not expect it anytime soom.
I only handled the certification letters and motor files. It was certified last fall- I know nothing of their production schedule.
Aerotech just published their updated motor matrix:
http://www.aerotech-rocketry.com/up...eroTech Master Motor Matrix 7-3-18 Sheet1.pdf
The J520 is missing, so I would conclude the motor is not currently in production.
So I already have a problem with this list. AT lists the L1040DM as a 75/3840, but it's on the Wildman site and a few others as a 75/5120. They can't even keep their own products straight???
Hey Guys, the J520W was certified as plugged a while ago and we have been trying to dial in the delay bit are having some issues. The motor is available but most dealers with them on order are waiting for the non-plugged motors to be certified.
I flew one to 11,500ft in a Go Devil 38 last year. Just my opinion I didnt think there would be enough demand for the delay version.
Anything worth flying this in, there aren’t delays for.
Plug it and ship it
I think there is a high demand for L2 cert flights on a rocket with the chute release
See my comments, I disagree. The impulse of this motor makes it perfect for L2 certs with motor ejection
Yup, Agree with T-Bone, I'm waiting on this one with delay... for the many one-off purchases of larger motors, this one fits the bill perfectly. Not all my larger rockets neatly support DD or Pyro.
Yeah, even though this reload uses the long 1080 case, it only has ~731 ns. By comparison, the classic J350 in the 720 case has ~698 ns and the "regular" J570 White Lightning reload for the 1080 case has ~973 ns.
Or you could use a 38/720 and get the J500 Green. It is 723 NS, and would have a better mass fraction due to less case weight.
I'm not very techy when it comes to rockets but how would you dial a delay in? Isn't that the point of the delay drilling tool and Rocksim/OpenRocket? I heard this is also a problem with the Redline propellant in the 29/40-120 casing and why they stopped selling the G71R for it
Not delay drilling. That's what we consumers do.
They have to determine the proper delay element composition and size so that after burnout, there's a consistent amount of delay left for timed deployment.
Different delay maerials are used for different motors depending on propellant and burn chemistry.
The g71r delay problem, IIRC, was that the delays aged sitting there in the package and you effectively got a zero-or-less. Presumably since the g77r works just fine, at some point the problem may have been resolved.
It has to do with the burn rate of the delay grains being effected by the pressure. Way beyond my pay grade too, just know enough to sound stupid.
J520W-13As are available at a significant discount right now from BMS.
Mine shipped with a motor date code of 09041802.
Be advised these are RMS-EZ reloads and require the 38FCRR retaining ring closure. Contrary to the AT EZ bulletin on 7/14/2015, they do NOT ship with a normal CRDK if you want to use your normal RMS forward closures that have functioned without fail for the last 20 years.
You could use the longburn plugged closure with these right? And it's non hazmat?
I guess these are the new supposedly fixed RMS-EZ closures. Now they need some guinea pigs, AH!! I mean flyers to see if they work right or not. That's why no CRDK included.
The J520 looks like a wasteful motor , in my opinion . The MSRP for the 730ns J520 is $85~ dollars vs $60~ for a 700ns J500. So you are getting basicly the impulse of a E15 for $25~ . If you where to order 2 J500's , the shipped price with hazmat would be cheaper then ordering 2 J520's without hazmat. Then you have to look at the cost of the 1080 case , assuming the flyer does not have one . Aerotech would have been better off redesigning a high impulse thrust load for the 38/720 case to be easy access . Instead , they opened the cores of a J570 till it met the requirements. If they had simply say , cut the grains of a J500 in half , so they can legally ship the motor non hazmat , then had the user glue the 12 small grain segments together to form 6 normal grains , they could have saved time and money , since this seems like a scheme to make a three non hazmat loads to compete with Brand L that does the same .
J-500 and J-350 are both retail $73 as of october 2018 update and require hazmat, not $60., J-520 is $86 and non hazmat, so $13 more. Casing is $5 more for the longer case, so pretty irrelevent if you don't have it. So it would take more than 2 to get even....The BMS sale is over. This info is from my direct Dealer price list I got from Aerotech at the end of October.
Yeah, competing is kind of the point. Of course brand L doesn't have a J that can ship without haz but who is really keeping track? The goal of the motor is to be US Mailable, that's it. A level 2 cert motor without haz.
I could not resist the temptation and got two reloads from the BMS sale. It looks to basically be a punchier equivalent of a J350W and I am a big fan of the flame and smoke of a White Lightning reload. One thing I wonder about with the return of the RMS-EZ delay format on this reload, is that it is similar to the DMS designs in that it uses the universal drilling tool. With the DMS reloads a washer has been added to the assembly of the element to ensure that the full ejection force goes forward, rather then exiting the nozzle of the motor. I wonder if something similar need to be done with RMS-EZ or if the design is different enough to not need it.
J520 is actually around $70.
Sale? Crud, I missed it. What was the price?
They were half price, like $43. I bought a bunch even though I don't have a 1080 case for them... apparently none of the vendors have them, either. Oh well, probably won't need them for a few months anyway.
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