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Alright, so  the J500T is a single grain Blue Thunder load for the 75/1280 case that exists on the Aerotech website, on the same instruction sheet as the K1000T (75/2560) motor.  However the J500T was never actually sold or certified. After talking with Karl at Aerotech, I found that shopping at the RCS webstore ( and buying the single 75mm Blue Thunder propellant grain and the 75/1280 EMK (experimental motor kit) will give you the J500T. Specs for the nozzle throat sizes are attached.  Technically since this motor was not certified it has to be flown as an EX motor.
This was being discussed on The Rocketry Forum just the other day.
(01-21-2019, 02:07 PM)jd2cylman Wrote: [ -> ]Interesting.
This was being discussed on The Rocketry Forum just the other day.

Thanks for stopping by. Don't be a stranger.

Just to clarify, my notes in the attachment in the previous post were from my conversation with Karl. Everything else should be straightforward.

I ordered the blue propellant grain and EMK. Hopefully it gets here soon and I can fly it this spring.

I also ordered a single 98mm green propellant grain and EMK to make a K motor for the 98/2560 case. The green 98/2560 load was demo'd about 12 years ago, based on my internet searching, but also never produced. I'll post another thread for that one.

Cheers! Hope your New Year is off to a fantastic start.
Rocket motor delivery tracking across the USA is always fun.

Shipping cost for this package including hazmat was $52. The purpose here is not an exercise in bargain hunting, but the total cost of this order was still less than the retail price of one 98/2560 load and one 75/1280 motor. So, relatively speaking, the total cost of these two motors is not bad.  While not exactly 40% off black Friday prices, it was still cheaper than if I bought similar motors at a launch.
I used a 29/64 bit on the nozzle for this one (medusa nozzle).
Bottom end after a successful flight on the J500T. Never mind the fillet repair job on the Estes MDRM.
Flight pics.  Pretty quick liftoff and nice long flame. The J500T is a 1280 N-s J.  The 60" Fruity chute brought the 11 lb rocket down at a slow 17 fps. It flew out of site and into the stiff breeze, but floated back to land about 50 ft from the pads.