What have I been up to other than working?
- Playing with writing Android software for my new phone, a Droid. Very cool phone. I am reminded how much I hate developing GUIs though. It’s so much work! In any case, I’ve been doodling with writing a program for helping out at the field during rocket launches. I’d like to publish it eventually but it’s tough to find the time to work on it.
- Cleaning the basement. I’ve had boxes that I haven’t fully unpacked since I moved out here to New Jersey from Indiana 5 years ago. It’s looking a lot better down there now.
- Planning my new CNC router. I currently have a Taig CNC mill, which is nice, but I often find myself wishing I had something with larger work area and higher feeds. I have an old PCB router (probably 20 years old) that was given to me, and it’s built like a tank so I think it’ll make a good frame for a retrofit (replacing wimpy little spindle motor with Bosch Colt router, wimpy steppers w/ 400 oz-in steppers, wimpy leadscrews with something beefy and fast like 1/2″ x 0.5″ or something). The blank PCB (copper-clad G10 fiberglass) sheets it used to cut are about 12″x18″, so the work area is not huge but still a pretty useful size. I’m hoping I can reuse all the linear rails and everything so it won’t be a big deal to retrofit it.
- Planning a million projects, as usual. I’ve just been too busy to actually get anything done on them. Hopefully that will change soon.

I was recently curious to see if I could build an extremely crude gyrocompass with little more than a motor and a wheel. I took an old motor I’ve had for probably 15 years and mounted it to a surplus stroller wheel with a shaft supported on bearings and a frame to hold everything together. The concept is that the motor spins up the wheel, developing tremendous inertia like a gyroscope, and the entire thing is suspended just so. If all the forces are in the right ballpark, over the course of 3 or 4 hours it should eventually orient itself so that it points to true north. So I built it and tried it out. Turns out the motor I had handy wants to spin that wheel *really* fast. It vibrated like crazy, almost a little scary. Haha. Those wheels aren’t the truest things ever. Maybe some time I will swap it out for something smaller that’s balanced better. I still think it would be cool to make a crude gyrocompass, I can’t see why it wouldn’t work.

Unfortunately this video only captures the events, not my commentary which connects them all together. Each event is displayed for 2-3 seconds, so you will probably want to just start and stop the video so you can go at your own pace.

I am sure plenty of people will see this and ask, “Why isn’t my favorite event on here?” Two reasons: 1) This is my timeline, not yours. 2) I had to scope this. As it was I had to talk fast for a half hour to get through it. If I had added anything more it would have been way too long. This means some things had to be cut. For example, there is no mention of the first space walk, let alone the first American space walk, or first man on the Moon. Why? For the purposes of this presentation, once you can get a spacecraft into space, putting a person inside that spacecraft and keeping him alive is a matter of refinement. And in many cases the US was not first, so why would I not give credit where credit was due? In some cases I just used an example that made my point, not necessarily the first or the best product or achievement. Bottom line: I could only put so many events in this timeline.

I’ve made a couple of quick videos and put them up on YouTube. One is about a cheesy program I wrote, MacBook Sonar. Basically it uses the laptop’s built-in hardware (speaker, mic) to measure the distance to the ceiling. Works decently well considering how hokey it is.

Here are a couple of videos of a stroboscope stopping the apparent motion of some of my tools (mill, grinder). Kind of cool.

Here’s a video I made that’s sort of interesting. I have this electric candle warmer that melts the wax, but when it cools the surface takes this strange concave shape that dips down perhaps 1/2″ or so. It’s hard to see but you can watch it form.

What about projects? A badly-timed hard drive crash wiped out most of my ramjet simulation work, and I decided to put it on the back burner (so to speak) for a number of reasons. However, I have made a good amount of progress on my latest project, which is a guided rocket. I will try and post again some time soon with some pictures of the current progress. There is a long way left to go, but I am actually quite pleased with things so far. If only I had more time.

• Rocket weight on the pad
• Frontal area (or largest diameter)
• Rocket motor used (allows me to look up the thrust curve on ThrustCurve.org, for finding drag during boost phase — EX motor without a known thrust curve? That’s ok, I just won’t have accurate data for the boost phase)
• Altimeter data (accelerometer AND barometric data would be perfect, accelerometer is the next best, but I’ll take just baro if that’s all you have!)

About my program, DragFinder: The goal is to find real-world drag information by launching real rockets. Programs like RockSim can try to estimate the drag, but when ballpark guesstimates aren’t accurate enough, DragFinder will offer the solution. The program will be freely available for download by anyone, and it will allow you to find the drag coefficient for your rocket as it varies with altitude, Mach number (taking altitude into account), and time. It will tell you the aerodynamic force on your rocket, and even Reynolds numbers (in case you are doing scale models and want to be able to compare flows).

Why would you want to help? Because when I’m done with it, I’m going to release it for free on my website. But why would you want to USE the program? Because it’s almost like having a wind tunnel. For one thing, it can help improve your future simulations. Maybe you have a crazy-shaped rocket that RockSim doesn’t know how to handle — this can help you model it. Maybe you’re planning on launching something really big/high/fast/wacky — this can help you understand the aerodynamic forces better on a scale model first, and help you model it more accurately.

I would also like to make the flight data I receive (along with descriptions and pictures if possible, maybe even RockSim files) freely available on my website. This way others that need similar information won’t have to replicate all this effort to experiment with writing their own rocket software. If you have data but do not want me to include your name on the website, just let me know.

Next on the list is converting the drag force vs time over to drag coefficient (Cd) vs mach number, which shouldn’t be too bad. I believe that should take both altitude and speed into account, hopefully resulting in a fairly accurate drag estimate.

So how do I verify that my code is working? Here’s where I’d like some help from rocket hobbyists out there, if anybody reads this: I need data. I need information about rockets including their weight, motor used, frontal area or diameter, and flight data (either altitude vs time or acceleration vs time). I’d like data for big rockets, small rockets, high-altitude and low-altitude rockets, everything I can get. I can get data from a few rockets of my own, but the more the better. Real data will allow me to validate that the software works (and find out why, if it doesn’t). I can then be confident that DragFinder will be an effective tool for characterizing the drag on my ramjet project. And, of course, I plan to post DragFinder for free so that anyone else that wants to can benefit from it. Anybody?

Unfortunately with the current version I have been unable to produce a Decker-inspired design that is self-sustaining. I am hoping this is due to an inaccuracy in the drag model. I am considering trying to determine a model of the drag forces empirically, possibly by building a scale model of the vehicle and flying it on a known rocket engine. Perhaps by tweaking frontal area and Cd values in RockSim and in my spreadsheet until they agree with actual flight data I can come up with something usable.

Hmmmmm….. How about a tool that read in flight data in the form of acceleration and/or altitude over time (maybe altitude would be easier for most people to come up with), along with a thrust curve for the motor, and it would produce a graph of estimated drag force? Of course the results would vary from flight to flight, but the more flights, the more accurate the data. Flying the same rocket a number of times, this tool could produce a statistically useful summary of drag forces vs speed. With a direct model of drag forces, one would not even need to mess with something so crude as a Cd. Oooohhhhh….. And one could even fly a version of the rocket without the ramjet engine attached in order to determine how much drag is caused by the ramjet engine itself. Oh man that would be useful….

• Local fire marshal: I live in the Burrough of Audubon, so this was Bill Schaeffer. He was glad I started by coming to him rather than just going ahead and mixing propellant in my backyard. However, he suggested I talk to the county people.

• County fire marshal: I’m in Camden County, so I spoke with Deputy Fire Marshal Ernest F. Busch. He asked me to send him some documentation so they could start a file and do some research, so I sent him the following:
• MSDS sheets for all chemicals involved in making propellant (AP, AN, aluminum and magnesium powder, HTPB binder, curing agent)
• Links to the Tripoli Rocketry Association (TRA) and the Maryland-Delaware Rocketry Association (MDRA)
• Scans of my TRA paperwork showing the signatures for my certifications
• Scans of all of my TRA ID cards (they happened to document my changes of address)
• Scan of the certificate received from John Wickman’s solid rocket motor design class

He said he would begin researching things, and recommended in the meantime that I try and talk to Lou Kilmer at the Department of Labor (DoL is in charge of explosives). I left a message for Lou but got a call back from the Department of Community Affairs instead.

• Department of Community Affairs, Division of Fire and Safety: they are responsible for the development and enforcement of the State Uniform Fire Code. I spoke with Josh Lazarus, Supervisor of Inspections. His determination was that since I would be working on my own property and making propellant for my own personal (non-commercial) use, the Fire Code does not apply. He then recommended I talk to the Department of Labor.
• Department of Labor:
• I first spoke with Senior Inspector John Jordan. He determined that since none of the ingredients in ANCP are on the ATF explosives list, and neither is the ANCP itself, they would have no jurisdiction over it. However since APCP is on the explosives list, that would probably require a permit from the Department of Labor if I intended to make it. He also said that since black powder (used in ejection charges) is on the explosives list, I would need a permit and a magazine for that, and on top of that, I would need a separate permit and magazine (with yearly renewal fees) for the storage of the electric matches which would initiate the black powder. And if that weren’t enough, if I were to install the black powder and electric matches on my property I would need some sort of installation permit. This all becomes very expensive. John then recommended that I run everything by his boss Howard Black to see what he thought. As for storage of commercial rocket motor reloads, he said that since the NJ Model Rocketry Act says you can store up to 220 pounds of propellant without any sort of permit, he didn’t see a problem there.
• Director of the Division of Public Safety & Occupational Safety & Health, Howard Black: He agreed that storing less than 220 pounds of commercial rocket propellant shouldn’t be a problem. I asked him about the issue of needing a permit for the black powder, and he said that since the NJ Explosives Act allows small arms reloaders up to 5 pounds of black powder (or 36 pounds of smokeless powder) without any permit, he didn’t see a problem with me doing the same for rockets. On the electric matches issue, he deferred to John Jordan.
• ATF: I haven’t spoken with anyone in-depth about this yet, they mainly just pointed me towards the paperwork for filing for a Low Explosives User Permit (LEUP). There are plenty of guides online about getting your LEUP, so I probably won’t duplicate much of that. As near as I can tell no LEUP is required to make AN motors. This (the LEUP) seems like the thing to get though, since it opens up a lot of doors (buying higher grades of powdered metals, etc).
• Local Police: I actually haven’t spoken with them yet, but Howard suggested I talk to everybody I can think of just to get everyone on the same page.

The No-Permit Approach: So what do I do with all of this information? I can’t afford to get permits for every little thing right now, but I want to be legal. So my current approach is to try and do without the things that require permits:

• Black powder: Keeping small amounts on hand should be fine as long as it’s stored in a USDOT-approved storage container (which I haven’t looked into yet).
• Electric matches: Maybe I can just make some substitute (capsules of black powder with a simple bridge wire inside?), or even look into using an alternative like a CO2 cartridge-type ejection system. Motor ejection is always an option for small rockets, though I am opposed to it in most HPR cases.
• Storing commercial propellant: This seems to pose no problem.
• Making custom propellant: Stay away from things that are on the ATF’s explosives list. Right now the best option seems to be using AN-based propellants.

If anyone has any updated information, please post a reply. I will try to keep this updated as I get more information. Thanks!

]]> http://www.creamyrobotgoodness.com/2007/12/04/amateur-rocketry-in-new-jersey/feed/ 0 http://www.creamyrobotgoodness.com/2007/11/07/shameless-plug-peeps/ http://www.creamyrobotgoodness.com/2007/11/07/shameless-plug-peeps/#comments Wed, 07 Nov 2007 22:51:04 +0000 Dave http://www.creamyrobotgoodness.com/2007/11/07/shameless-plug-peeps/ You know the story well: You love Peeps. You crave Peeps. But there are only specific seasons when Peeps are available, forcing you to wait and settle for lesser treats in between seasons. So what’s the solution, you ask?

OffSeasonPeeps.com is now open! We are still setting up the website and figuring out how to run everything, but this will be your one stop shop when you are jonesing for some yellow Easter chicks, white Halloween ghosts, or [insert your favorite marshmallow Peep here].

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