I like White Lighting in a commercial propellant but in a two grain motor, I also like my kick butt Tiger-Tail I mixed myself in A-T hardware. Flew a 2 grain 38mm A-T H in an ASP WAC Corporal and it always gives a beautiful leisurely ascent to about 1300-1500 feet. I put electronics in that great nosecone ASP provides and made the cone base removable for battery/electronics access so my WAC carries more weight. Used a Galejs MAD unit for flawless apogee deployment and a Jolly Logic chute release to unfurl the main at a lower altitude.
Put my 2 grain mixed H motor in using A-T hardware and I have to use a slightly drilled out nozzle from a J-350 and it's "kick butt" time as the rocket goes like a bat out'a h$ll to "out'a sight" land for awhile. The "pseudo" dual deploy with the JLCR really helps here too. Shoot, bought two of the JLCR units when they first came out. The Galejs MAD unit can be dicey and could only be activated upright on the launch pad but there are other units with failsafe circuits out there now. It was simplistic and cheap at the time to build. (I believe $19.95 but correct me if I' wrong on that. I ordered a bunch of the Galejs kits.)
Available engine simulation software can only do non-erosive nozzle simulations (ie. graphite nozzles) of motor firings as they can't take into account nozzle erosion. That's impossible to do as more aggressive propellant will erode a phenolic A-T nozzle faster. I did several ground tests to hone in on the proper nozzle throat for my 2 grain 38. Took time but it was a lot of fun. Used the simulator to get a ball park figure and err'd on the side of too large a nozzle throat to judge the burn and not blow the A-T hardware to smithereens early in the testing cycle. I have the videos buried somewhere of the ground tests. Some are funny to watch as they were close to road flares. As I honed down to optimal nozzle throat, I got better firings. Sometimes would "fart out" some molten plastic from the casting tubes at the end of the burn. I got a laugh out of that as I was very far away of the test burns. My video camera was closer and set to be zoomed in on the "butt end" of the motor so I got to see a lot of detail on playback when I got home. As mentioned, I got a kick out of that. Especially if it was a good burn test.
I will concede I found a thick-walled Garolite liner that fit A-T 38mm casings and used a clear plastic liner to cast the grains that worked. The Garolite liner was used to support the flimsy plastic casting tube while I packed and boy did I get an education besides using the Garolite liner in flight. No matter how hard I tried, the grains had teeny-tiny voids that I couldn't get rid of no matter how long I keep the uncured propellant under vacuum. Shoot, I could keep the mix under vacuum overnight and no matter how hard I tried, I still got "teeny-tiny" voids. I figured "wtf", I'll compensate on the nozzle throat. Worked well. Gosh, the Garolite liners were so thick, I could ream the remnants of melted plastic "casting tubes" out of them after a burn and get three firings out of the same liner before I had to retire them! One cannot do that with A-T stuff as their liners are single use only. Most are cracked or obviously not serviceable after firing. I did some of my mix in their stuff and the liners were single use as it is with their provided motor grains . It was so fun as I was the only one doing this stuff as far as I know at the time. With the clear casting tubes I could see the through the sides of the grain. It was an eye opener but was compensated by nozzle throat adjustment. More voids in a propellant leads to faster burn rate due to larger burn area.
Oh, A-T will sell one all the bits and pieces of their motors for a price and I ordered a lot of their "bits" a long time ago. Nozzles, O rings et ecetera. (Until I measured the O rings and ordered the high temperature rings from McMaster-Carr.) They were red-orange colored but I suspect they didn't make that much difference as far as motor competence. I suspect that the heating of O-rings might allow them to "melt" just a bit and seal voids to prevent blowouts. Just a conjecture on my part but I believe plausible mind you since motor burns are relatively short most of the time. (Excluding the long burn motors mind you.)
Kurt Savegnago
