Rocket Wonk

national perspectives on hobby rocketry and stuff

[rocketwonk]

My clips from AIRFest 23.

[rocketwonk]

Work in progress on the blog. Stay tuned.

[rocketwonk]

ROCStock on WBUR

Every month in the Mojave Desert, amateur and professional rocketeers gather to launch rockets thousands of feet into the air. Why do they do it? Saul Gonzalez of KCRW in Santa Monica attends an event and has this report.

Really nice piece on the biannual ROC event by Saul. And I'm not just saying that because I'm in it! Lots of good interviews and sounds here.

[rocketwonk]

Rockets of the corn. Complete Midwest Power 12 photoset on Flickr.

[rocketwonk]

Compatibility and the Hubcap

Let's face it, a lot of the magic I used to attribute to rocket motors was lost once I figured out that it's just a tube with ends and a right-size hole for the fire to come out.

But the propellant--that's the interesting part, especially so since propellant manufacturer choice has been the topic of near-holy wars in the hobby. The problem is that all manufacturers have their own unique tubes to go with their propellants, when it shouldn't really matter--the tube's job is to keep the fire coming out the right end, and that's about it. The uniqueness of the tube seems like more of a printers and inks (or razors and blades) thing: motor hardware is expensive infrastructure, so sell it at lower margin to lock people in to the higher margin propellant. The problem is that people end up with ridiculous tubs of mismatched hardware from every manufacturer taking up space.

Several years back, CTI did something that’s now blindingly obvious: make propellant that fits their tubes AND tubes made by other manufacturers. Uproar ensued: warranty coverage, certification status, and reload quality all became points of contention. CTI solved these problems well—replacement CTI hardware, individual cross-certification, and high (thankyouverymuch), respectively.

They also introduced what is probably one of the hobby’s best kept secrets: the “hubcap” adapter to allow CTI loads to be flown in snap-ring (AMW, Gorilla, Loki) cases. CTI 76mm propellant fits in cases from every major manufacturer, using every end retention technology.

But more importantly, I'm also one step closer to minimizing the volume that motor hardware occupies in the garage. Please keep up this cross-compatibility thing. Us flyers like it!

[rocketwonk]

Shhh, don't tell anyone. It's coming soon.

[rocketwonk]

Glue

I'm at the point where I need to buy some more epoxy. David Hailey turned me on to Aeropoxy ES6279 a while ago and, with the exception of a brief dalliance with Rocketpoxy (which I ended up giving to a fellow flier and kind of forgetting about–nothing against it), I've been using it exclusively for general bonding ever since. Laminating epoxy is for another discussion.

One quart size kit built a 6" IQSY Tomahawk, a 6" V2, a 6" Little John, a 3" Wildman, a 3" Darkstar, several Wildman Minis, a couple of Wildman Junior-size prototypes, and other miscellaneous stuff I can't remember right now. My next quart kit? I have no idea what's in store for it, but I love looking at fresh, unopened cans of epoxy, wondering what adventures we'll have together.

[rocketwonk]

Yeah, every reload comes with a free Kosdon Wallet!

Hulan Matthies, on Frank's tendency to carry cash in a ziploc bag in his swimsuit.

[rocketwonk]

There’s something weird up in the corner of Lucerne Dry Lake. Rick Magee mentioned a compass rose for bombing practice at a launch a few months ago. Time to go exploring.

[rocketwonk]

How do you keep the Estes line happy when there are 400 of them (with an endless supply of motors) and 3 of you? Bonus points: keep the high power line happy at the same time. Level up: hook enough of the Estes line that they visit the vendor and get a mid power kit. This is making my brain itch.

[rocketwonk]

Critical Culture

Seth Troxler:

Look, I’m generally really happy for everyone. I try to keep positive about all this craziness. But if you’re not critical of the culture you live in, and love, then you’re doing yourself and everyone around you a disservice. EDM plays host to a profound delusion about what electronic music and dance culture are. It’s ridiculous music, made by ridiculous, un-credible people. 

In all honesty, I find it profoundly sad. We’re trying to move on and be a real force of culture and conversation—a wider genre recognised as having real cultural depth—but EDM is wiping that slate. For being taken seriously in a musical sense, that’s frustrating.  A lot of my work— especially with my label Tuskegee—is a revolt of that, and an attempt to historically legitimise our culture. That’s my passion. The rave changed me, and I want kids to be able to experience that tomorrow.

Swap in "internet rocketry" for "EDM" and "rocketry" for "rave" and you've got my current state of mind. (And I agree with Seth about EDM culture too, but that's the wrong blog.)

[rocketwonk]

One Pad (or LCO flow control ctd)

My dad and I were talking about range flow control again (thrilling, yes?) and he brought up a good point about this launch:

 A lot of flights for just one pad. Makes me wonder if launching would be more efficient at ROC if they had fewer pads....

Is the critical issue for throughput the number of pads, or the competency of the range boss in utilizing them? I would tend to think the latter. MDRA usually sets up 28 pads for Red Glare in three banks of eight, plus four away cells, yet they manage to launch 600+ rockets over the weekend. CMASS does 350 rockets in a day with 14 pads. ROC sets up 60+ pads for ROCStock, but at its peak only launched 800 or so.

Setting up fewer pads also has the benefit of reducing workload on the volunteers. Maybe the active number of pads should be constrained to the number that the LCO can mentally manage.

Related: Interstate 5 in south Orange County has 9+ lanes in each direction, yet still gets blocked up during rush hour. It's not a capacity problem—it's a control one.

[rocketwonk]

Launching in the snow is something I've always wanted to enjoy, but never have. Until last weekend: clear skies, calm winds, and tons of flights at the QCRS February launch outside of Princeton, IL. Here, Chuck Swindler puts up one of many M flights for the day. My full photoset is over on Flickr.

[rocketwonk]

Polecat is Hiring, ctd

A while back, it came up that Polecat was running into either supply chain or labor problems; either way, the pipeline was clogged and there weren't any kits being produced.

With the recent news of Jack no longer planning to serve the ROC monthly events, it then comes as no surprise to read this on Facebook:

Hey all, Tim Z. from Leading Edge Rocketry, here. Excited to let you all know, as of January 2014, LER has purchased Polecat Aerospace from Jack Garibaldi. All kits are back in production and will be available for your purchase within the next 30 Days! Please visit www.polecat-aerospace.com for more info!

Divorcing the kit line from the dealer (i.e., What's Up Hobbies) is an excellent choice; Andy and Jack both succeeded as a result of their manic passion for the sport, but that will always lead to burnout. This seems like a healthy, stable path forward for the line.

I'm glad someone will be continuing to carry on the Polecat tradition of big, light, inexpensive cardboard kits. There's definitely a market out there for them.

(Discussion thread over at TRF.)

[rocketwonk]

Speaking of loads for the 3300, here's a photo I took of a Kosdon L3000 in a rocket by Joel Rogers, NERRF 2011.

[rocketwonk]

PEPSRC

Martin-Marietta's PEP—Propellant Evaluation Program—is every hobbyist's favorite equilibrium code. (I've since moved on to others, but that's because I'm insatiable and it's hard to cite an ancient code from a company that no longer exists in refereed journals.) Unfortunately, the binary floating around the internet was last compiled c. 1996 to run on 16-bit machines, and so it's effectively dead with Windows XP reaching EOL. John DeMar found a copy of the source and uploaded it to his website. I've mirrored it here. Compile it while it's hot.

If you're not a FORTRAN guru, the NASSA guys have compiled a .NET version available on their website here.

(Richard Nakka has a nice writeup on the inner workings of PEP at his website, too. Check it out.)

[rocketwonk]

I made this video to explain the math of burning rate stability. For a good propellant, n < 1 is the requirement. If it's got plateau burning, so much the better. Implying that your motor is running unstable and on the verge of blowing up because your propellant has plateau burning is just against the math.