Hello Wyatt, ECP is a pretty good reference IMHO, but the author is ugly
and his wife dresses him funny.;-)
You were wise to go with the HTPB system, mainly because that's what
most amateurs use, so finding a mentor who can stand beside you and
provide direction isn't a major undertaking. And of course, it cures
faster...though I've never had much luck with IPDI alone as a curative.
If you haven't done so already, you might check Chris Short's site, he
has curatives for sale. https://www.csrocketry.com/
I'm a little concerned about isocyanate vapors. Either work outdoors
under a pop-up awning on a calm day, or have active venting -- a good
fan blowing out of an open window, with more open windows in the are,
and arranged so the vapor doesn't go over you as it exits.
In ECP I concentrated on 29mm motors (I'm frugal. Or cheap. Whatever),
but 38mm is significantly easier to pack, if you're packing and not
pouring. A single-grain 38mm has about the same mass as two 29mm grains.
Feel free to holler if you have questions.
Best -- Terry (who is actually handsome. Debonair. Witty. And modest,
I forgot modest.;-))
On 1/30/2020 2:10 PM, Wyatt Harris wrote:
Hi everyone,--
I've been subscribed to AROCKET off an on for the last ~20 years, and I believe this is my first post (I may have sent one when I followed this forum back in high school, but I can't remember).
To provide a bit of an intro about myself, for those that care, or at least to show that I'm not coming at this totally out of the blue:
I started building rocket motors in middle school and continued into high school (early 2000's). They were almost all KNSB motors (thank you for your website Richard Nakka!), with the exception of a large LOX/hybrid that I built with a propulsion engineer from Raytheon, and launched at BALLS 2004.
I went on to get a BS in Astronautical Engineering, where as a senior I was chief engineer for a boosted dart rocket project that was launched at WSMR in 2009. Following college I got a MS in Mechanical Engineering, did some other stuff for a few years, and am presently 1.5 years into a 3 year PhD program in Astronautical Engineering (not researching anything propulsion related however; I'm actually examining a GNC topic for spacecraft RPO).
To the subject of this email: I recently got back into building small rocket motors as a hobby. I've made a few small KNSB motors, though I'm more interested now in moving on to APCP. I have the APCP/HTPB kit from Firefox. For the time being, I intend to build and test motors with <50g of propellant.
I'm reaching out to the forum with the hope that this might be a good place to get some advice on working with APCP (especially regarding safety, common pitfalls and best practices). I've got and have read through /Experimental Composite Propellant/, /Plastic Resin Bonded Fuel Systems /(Firefox book), the CP technologies book (doesn't seem very helpful for APCP though), and I also have Burnsim. I intend to proceed following the procedures outlined in the first two books as closely as possible.
If this is the right place to ask, I suspect I'll have plenty of questions moving forward, but to pose a couple to start:
(1) My main concern right now is proceeding safely, so any practical advice out there regarding safe production of small APCP (<300g) batches? My initial plan is to use an open garage with PPE including nitrile gloves, goggles and VOC respirator. I've taken a look at the SDS's for the chemicals involved, it seems that IPDI is is the nastiest component? The SDS for this makes it sound very toxic.. how concerned should I be about this for the small batches I'm making? Any concerns/things I should know about other chemicals such as AP/HTPB/EHA/tepanol? I'm not planning to do any crazy propellant formulations (exotic oxidizers/metals) at this point.
(2) I opened up the teponal (HX-878) from the kit and noted that it is *extremely* viscous (challenging to remove any with a tongue depressor). Since it's been a while since I bought the Firefox kit, wondering if this is normal, or has it gone bad?
Thanks for reading the long email. Thank you in advance for any advice!
-Wyatt
