Thinking about Level 3

Someone at a recent launch was overheard saying, 'you can't start thinking about level 3 too early.' Even though I'm still a J350 (and an open chute) away from an L2, I've already started firming up details for my L3 project. And it doesn't matter if you are NAR or Tripoli -- L3 is L3, and is always a challenge.

Some folks just build a kit for L3, and simply fulfill the technical requirements without really learning anything new (aside from the fact that J-B Weld is more expensive than 30 minute epoxy). That's fine, if your certificate collecting. But I really want this to mean something. Its an opportunity to learn a lot of new, cool stuff -- why not take advantage of it?

Knowing that I am primarily interested in (A) avionics and (B) materials as they related to rocket design should drive my requirements. The thought of a lightweight, fully ground-controllable rocket that gets 100k feet out of a Q engine definitely gives me that 'special feeling'. My L3 should help me progress in that direction, since that is where I seem to be getting my rocketry buzz.

That said, I have a few simple goals for an L3 project:

• scratch build -- I have done plenty of kits of all sizes, so I wanted to try something more challenging. One reason to do this is to challenge yourself, and kits are getting a little ho-hum.
• keep it simple -- I didn't want to try anything fancy. In fact, I didn't even really want to do my own design -- I'd rather just 'borrow' a proven and useful one that appealed to me.
• use composite materials -- I have my eye on a 100 percent carbon-fiber airframe. We'll see how close I can get balancing the first two constraints of amateur rocketry (practicality versus price).
• come out the other side truly at another level -- I really want to learn a lot from this experience. So I'm going to keep the goals a bit 'lofty' (har, har).
  

Then came the scope creep:

• RF device 'friendly' -- must be 'easy' to hook up antennas to RF devices. Would be nice to be able to hook up antennas for up to six bands (23cm, 33cm, 70cm, 2m, 6m and 10m). These are used for mostly amateur radio related activities (ARPS, ATV, telemetry and propagation experiments). Also provides RF shielding to the electronics bay. RF choke system for firing leads going to the motor (to prevent RF-induced ignitions). Pyro lines are intentionally designed to not resonate at the used RF frequencies.
• Camera friendly -- Live video/audio (on amateur 70 cm), live video recording to hard drive, two aerodynamic (hidden) camera bays.
  
• Altitude hog -- something light, that eats up space. something that almost begs for an 'N' when its on the playa.
  
• Design must be scalable -- I didn't want to just jump into the Level 3 design. I wanted to build a smaller J-K prototype so I could 'learn' the new techniques (such as carbon fiber) and minimize risk to the main project (didn't NASA do it this way?)
  
• Use a flight computer of my own design -- I just converted to embedded systems (after 20 some-odd years of software engineering). I have an idea for an avionics system, that includes pyro firing and a telemetry bus. We'll see how that pans out.
  

As a 'really nice to have', being able to run an M hybrid motor with little modification to the rocket would make it even sweeter.

After looking around a bit, I believe I found a design that meets all of my requirements. The ARLISS-M is a Level-3 class rocket that is used by AeroPAC/ARLISS for low altitude student projects and experiments. It also comes in two flavors. The K class is designed to carry a CANSAT payload (a payload that is the size of a 'regulation' 12 ounce soda can) to 10-15k feet. The M class is designed to carry a larger payload to 30k feet. There's plenty of room for electronics, antenna systems could be deployed in the nosecone, and/or worked into the carbon fiber (thin wire). Cameras? No problem. There's plenty of places to put a microcamera. I also like John Coker's 'keep it simple' attitude towards design after spending a lot of time and hassle with the more complex version of the craft a few years earlier. That right there is free bug and beta testing, compliments of a pro (John, you don't know me, but thanks!! Now I'm going to steal your design. :) ).

Plus the design is already scaled down. What's not to love? And, I just joined AeroPAC, so it will likely be easier to find folks to help with this, since it is their design.

While I'm still new to HPR, some things are true anywhere: know what you want from your L3 experience. Do you just want to be able to burn expensive engines, or do you really want to know how this crap works? If it is the former, that's great! Get a well-designed kit, build it solid and fly the hell out of it! If you don't really know what your L3 goals are, then ask yourself why you got into HPR to begin with. Your goals are probably speaking to you there, in disguise.

If you decide that scratch building your L3 project is your thing, then hang out with me over the next few months. I'll be learning many new things -- drop by and I'll share them with you. And feel free to share your knowledge with constructive comments or critiques (especially if you know how to make long, strong and straight carbon fiber tubes).

kind regards,
-r

Part 2 -- Polecat Aerospace 5.5" 'Honest John' M31 1/4 scale kit

A little history before we start building the M31.



The Honest John M31 was originally developed and deployed in the early 1950's as a tactical nuclear weapon (sometimes called a 'battlefield nuke'). Originally conceived during the early years of the Korean War, it was first deployed in West Germany as a counter to the massive number of Warsaw Pact troops huddled along the western borders of the most eastern European countries. The M31 came in three pieces and could easily be assembled by a three man crew and ready to fly in 15 minutes or less. It had a range varying from 6 to 25 miles -- just enough distance to hurl a few kilotons at those pesky Red Army forces (remember the Cold War??). It was later replaced by the M50, which was shorter, lighter and had better gas milage.

The original M31 design was developed from off-the-shelf components inside of two years. The first version used a stock Aerojet JATO motor, which had enough impulse to propel 1,500 pounds around 15-20,000 yards.

Here's a link to an excellent declassified document (called a 'monograph') about the history of the Honest John program, as well as a great write-up describing the mindset of the time, and the motivations behind the tactical nuclear weapons program.

It was also a rocket from my childhood, growing up in the late 60's, about an hour away from Werner Von Braun's American home in Huntsville, Alabama (it was first built at Redstone Arsenal). My father and I must've built three or four of these things (my earliest cato was an Este's Honest John M31 at age 6. Back then, a cato got you a free rocket from the engine manufacturer. That *and* Apollo at the same time?! Wow, what a great time to be a kid.)



Now, let's get back to the kit.

The motor tube in the Polecat kit is simple to construct. Pretty much like every other motor tube assembly you've ever constructed. I used 30 minute epoxy, though 5 minute would work just fine on these kits. Again, I'll mention the lack of a third centering ring on the motor tube. It would give the fins extra needed support. The 5.5" Nike Smoke has this third ring, and was probably instrumental in helping to save the airframe on my version's last 'landing'. Since I plan on this being more 'eye candy' (flying I's to K's) than an engine hog, we won't worry about it.



Installing the motor tube assembly into the airframe is a simple matter. Nothing complicated here. Everything fits snugly, as it should, and the epoxy bonds well, leaving a very solid, confidence-inspiring airframe, even without the extra ring.

Assemblage of the fin can area is easy. The thick, freshly cut fins definitely need some sanding time. This is not a construction article, but I'm a relative newcomer to HPR. So if you are as new as I am (and maybe in the same boat), I'll make my plug (again) for this handy device:


It's a $40 circular hand sander. I hear you guys with nice workshops snickering from behind your drill presses, but for a guy who has never really had a good set of power tools, discoveries like this are lifesavers.

Anyway, I whipped through the fins in five minutes. The only problem I had was that I switched to 30 minute epoxy and still kept my five minute habit. I did two opposing fins, taped them, then noticed 15 minutes later that all of the epoxy was running down the fins, and one had popped out a bit. A few 'adjustments' later (including using a Big Gulp straw with the spoon end to pick up what little wet epoxy I could) and it was back together. I still managed to leave a mess of epoxy on the fin, but managed to maintain its integrity with a good bond.

The Honest John M31 has a distinctive nose, to say the least. And with the Polecat kit, that is exactly what you get. It's over three feet long, very sturdy (fiberglass) and has a nice, smooth finish. There are seams from the molding that you will have to sand down, as with most cones. However, I discovered that this particular nosecone was too large for its bulkhead, which slipped right through. It was also too large to fit into the electronics bay coupler section, even after I sanded the cone. I have contacted Andy, but it is the weekend, and this is 'near real time', so I'll probably hear back from him on Monday.

Next time, I'll cover the electronics bay (the dual deploy option), rail mounts, and miscellaneous information about the kit.

Merry Christmas

-r

Part 1 - Polecat Aerospace 5.5" 'Honest John' M31 1/4 scale kit

When one makes the step into high power rocketry, there is a certain amount of obliviousness to how much money is about to be committed to building things that will literally go up in smoke. But after a few k-notes and untold hours (along with hard landings, catos, crashes, lost rockets and really long walks), one resigns himself to the somewhat uncontrollable 'impulse' to build larger and more 'airworthy' craft.

I had recently built and flown a 5.5" 1/3 scale Nike Smoke from Polecat Aerospace (Santee, California). Painted all black and 78" tall, it is an attention getter at any launch. Fly's nicely on I-J motors, and reportedly can run an M with no problem. On my Level 2 cert attempt (with a J570 -- I definitely wasn't messing around :) ), it took a particularly hard landing after a chute failure. The hit only popped off two of the thick spruce fins, with no other damage whatsoever. Convinced of the quality of Andy Woerner's (Polecat's owner, and owner of What's Up Hobbies) kits, I decided to pick up his 5.5" 1/4 scale Honest John M31 for a special project.

When I built my level 1 rockets (LOC Precision's Hi-tech 45 and its big brother EZI-65), I was introduced to the first level of high power construction methods. High power Level 1 (Tripoli or NAR) is where one graduates from the childhood of Elmers glue and Estes rockets to the joys of 5 minute epoxy and Kevlar straps. Both the Honest John and the Nike Smoke kits are designed for the stresses of Level 2 flight, which means fiberglassed airframes, thick, spruce fins and lots of heavy duty hardware.



The Honest John comes in a large box, and is a bit under 10 pounds delivered to your door. The large, distinctive nosecone is fiberglassed plastic, and the body tube (which is shown still wrapped up) is a standard thick airframe tube that has been fiberglassed. I opted for the dual deploy option, so this presented me with more hardware than I had dealt with on the single deploy 'Smoke. There's an electronics bay, along with a large bag of u-bolts and a few other items that one doesn't see in a single deploy system. I was a little disappointed to see that there were only two centering rings for the motor tube. The 'Smoke came with three, and Andy provided an extra to epoxy on the bottom of the rocket (to shore up the airframe in case of a hard, desert landing). However, I am building this for a special 'project' and won't have time to order and wait for an additional centering ring, so I'm going to go with the manufacturer's design.

If you've ever put your hands on a finished Polecat kit, the first thing you'll notice are the sturdy spruce fins. These fins will take a hard hit without breaking and won't fold under high aerodynamic stress. This kit is no exception. In fact, any kit you get from Polecat will have a sturdy airframe and full-duty fins.

The downside of large kits is that there's a lot of sanding and finishing work. That could be said of any rocket kit, but with large kits, there's so much more of it that hand sanding is less of an option. I decided with this kit to pick up a nice, small circular sander (for about $40 at Home Depot). I could've done a much better job with the finish on the 'Smoke if I had not sanded it all by hand.

Andy says that you can build any of his kits with five minute epoxy. I built my 'Smoke using mostly five minute epoxy -- and it has held up wonderfully. But I've decided to go with the extra strength of 30 minute. Plus the longer setting time leaves a smoother finish than five minute (a bonus for those of us who can be a little sloppy sometimes).

In the next part, we'll start building the Honest John -- and maybe I'll give you a little clue into my 'special project'.

peace and respect
Robin