For the new blue, I’ve been trying to characterize rate data from motor burns, rather than from strand burn data or burn rate motor testing. (It’s more fun to static test a motor than it is to do a strand burn test.) More on the maths later, but here’s the results so far:

Overcast at times, nice temperatures in June, Skidmarks in California, Frank Kosdon legal again. What was going on?! Hats off to the board and all the volunteers for a fantastic launch. Find some of my photos from ROCstock 29 after the jump, including lots of Ms, Skids, Greens, Reds, and an L3 flight.

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I’ve been working on a new blue formula as of late. Consider this the first “official release”. It was conceived in January, first fired in April, and first fired with data last weekend. It’s a smokeless variant of the typical blue I’ve flown in the past — 1% CuO, 2% Al — with the goal of getting something “Blue Thunder“-like. The story of the first flight is up in a blog post on OurPlanet.

First reactions from the flight were: (1) Not quite as fast as Blue Thunder, but certainly nice nonetheless, and (2) Oh my, look at that flame separation. Data from static testing showed that this burn was only at ~570 PSI, but the flame stands off nicely, even at low chamber pressures. It turns out to be about as fast as Kosdon fast, at least per the data. Here’s a typical curve from a Loki 38/480 firing:

Delivered Isp is somewhere around 200 sec, so nothing too special — just another “knob” propellant to add to the fray. Formula and rate data after the jump.

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After more research, discussion, and testing, the linear erosive model (see this post for more info) doesn’t seem to hold 100% true. Sometimes. This post is more of me thinking out loud about the subject in general, and attempts to tie up most of the theories into a neat, easily accessible post. So, here goes.

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It seems that Strontium Carbonate-based red motors get a bit of a bad rap in the community. The king of these formulations is Pat Gordzelik’s Polish Rojo family of propellants. I originally shied away from making reds, as I believed PR/SPR to be “wimpy” propellants that made a weak red flame, and that real men used Strontium Nitrate to make red motors. But Strontium Nitrate has its problems — it’s highly hygroscopic and needs to be dried and screened before use, and the grains must be kept sealed tightly before flight. I have a few old Kosdon East “Red Rhino” motors that are nitrate based, and though they give a BRILLIANT red flame and a delightful low-thrust, long-burn profile, they are immensely difficult to light due to their age and the amount of moisture collected by the hydrophilic Nitrate groups.

So, I decided to try out Polish Rojo:

Nice flame, Pat! (Photo by SoCal Mad Matt, click for larger version)

Further details on the motor after the jump:

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Nice day, small crowd, relaxed atmosphere. It was good to see everyone again after a four-month ROC hiatus! I flew two rockets and took pictures of a few others, including two L3 shots.

Photos after the jump:

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There has been a lot of discussion as of late regarding erosive burning and its relation to mass flux. Many have suggested that propellants with certain additives (notably, Oxamide) have a better response to high mass flux conditions, and have proven with ample results that it in fact does. While the effect these additives have is noticeable, it does not seem to scale linearly with pressure, as I might have expected thanks to the basic interpretation of Vielle’s law. After doing some thinking and some research, I happened upon some useful information on how to characterize the effect mass flux has on erosivity.

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I was browsing the catalog at one of my favorite chemical suppliers (Darren originally told me about them — Mach 1 Chemicals), looking to submit a few quotes for new bonding agents, as my supply of HX-878 is rapidly aging and I’m looking for a new, possibly more useful, compound. In the middle of my browsing, I happened upon the following entry:

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Let’s see if this works:

Well, isn’t that lovely!

I would have brought back more photos, but my camera battery turned four this month and decided that it didn’t like to hold a charge any more. Thanks to Ken Brown for letting me borrow a pack on Saturday, but unfortunately I got in exactly one picture on Sunday before mine bit the dust — hard. Regardless, here’s a few pictures of the action, biased towards my own flights (two Mojave Greens and the venerable Arcas lighting a red motor). There’s also pics of a L3 shot, Greg Lyzenga’s Thumper painted to look like a carrot, and Tim Scott’s all-carbon Butt Ugly Phoenix on a K550W, with the appropriate flame-to-rocket ratio.

http://www.tdkpropulsion.com/photos/roc408/ for the rest of them.