Month: November 2019
Last weekend, I attended a launch event hosted by my local rocket club. It was a great experience, and I enjoyed watching others launch a ton of rockets, large and small. A launch report that the club sent out afterwards said that there were 111 total flights, ranging from motors sized 1/2 A up through G. (It was a low and mid power launch, so nothing higher than that.)
Something else made the day particularly memorable: my rocket self-destructed.
But first, a little background.
A rocket launch can go wrong in a lot of different ways. A LOT. One of the most common issues is a failure of the recovery system – for example, the parachute fails to deploy properly, and the rocket comes crashing down. But a rocket can be constructed perfectly and the launch can still end in disaster if the motor or engine malfunctions. Motors are designed by people with advanced degrees in chemistry and engineering, and constructed with expensive equipment in large facilities (with hefty insurance policies), but they’re effectively just small explosive devices and things can understandably go wrong at times. When a motor fails, it’s termed a “catastrophic failure,” commonly referred to in the rocket-launching business as a “cato.”
This launch day had an unusually large number of catos, including during one of my own launches.
I flew the “Mean Machine” twice, and the first time everything went well. It launched smoothly, flew high, the parachute deployed, and it drifted back to the ground. I recovered it and prepped it for a repeat performance.
But on the second launch, the motor suffered a catastrophic failure. It seems that the propellant inside the motor somehow exploded out of the casing, which meant a small fireball shot upwards through the rocket, superheating the body tube and blowing off the nose cone prematurely (and shearing off the parachute’s shock cord, severing it from the rest of the rocket). The body tube, which is normally very hard and difficult to bend, crumpled from the extreme heat. It then quickly cooled, and is now frozen and unbendable in its current sad and broken state.
I’m reassured that this “cato” was solely due to a defective motor and not my shoddy construction of the rocket, and I’m further encouraged by the fact that something similar happened to several other people on the range that day. (Not that I’m happy it happened to anyone else, but at least we could commiserate.)
And to be honest, it’s not really a big deal – the fins are totally fine. With a little work, I can cut away the damaged part and re-join the two halves of the tube into a single straight rocket again. It’s a good learning experience, and it makes for a great video clip, too, which I’ll post shortly.
Local rocket club launch
This weekend, our local Seattle area rocket club (Washington Aerospace Club, or WAC) held a small launch event at 60 Acres Field, a park that’s roughly a 30 min drive from where we live. We decided to stop by and check it out, and I brought along the Mean Machine and some E motors. This was the first time I’d been to a club launch and it was a great experience – it was well organized and coordinated, with a carefully set up range area and a range safety officer (RSO) in charge.
I didn’t know quite what to expect but they’d already set up all the launch pads and equipment, which made things really easy. Several dozen people attended, including families and young children, some to launch and others just to spectate. There were some really impressive rockets out there. Other groups were on the field too, aside from our club members – several groups of students were there for the Team America Rocketry Challenge, or TARC, so rockets were constantly in the air.
I was able to launch the Mean Machine with an E motor twice – the first launch and recovery was a textbook success, while the second was… more interesting. More on that in my next post. But I also plan to upload some video clips from the event!
High power rocket construction: part 1 (motor mount)
I finally got my head out of my ass and started putting together this high power rocket. (My head is often firmly lodged in my ass, so extracting it is time-consuming and unusual.)
The basic parts are similar to those in smaller rockets. You build a motor mount (to hold the motor in place) by attaching three centering rings. These rings keep the motor mount tube centered – hence the name – within the larger body tube of the rocket. Then you attach the fins to the motor mount. All of these attachments should be made using a strong wood glue or epoxy.
Later in the process, the larger body tube will slide over the mount and will be flush against the edges of the fins, where they can be secured with glue again on the outside of the rocket. They’re held firmly in place, inside and out, which is important because of the high stresses that will be placed on them during launch.
Finally – you attach a steel eyebolt through one of the centering rings, using some washers and nuts and then a strong epoxy to hold it all in place. The purpose of this is so that you can attach it to a strong (and fireproof) cord inside the rocket body, where the other end of the cord is attached to the nose cone, along with a parachute inside for recovery. This allows the rocket’s nose cone to pop off just after the rocket hits apogee (its highest point in the air) and lets the parachute deploy, while ensuring that all the parts stay together on the way down.
As a side note, if you include an electronics bay (“e-bay”) in the rocket, which is optional, then you need two cords: one to attach the motor mount to the e-bay, and another to attach the other side of the e-bay to the nose cone, so again everything stays together. The e-bay also have steel eyebolts on both ends for attachment. Just FYI, I’m building and including an empty e-bay in this rocket; I’m not actually installing any electronics in it for the first launch. I want to keep things relatively simple for my level 1 certification flight and will start putting in some interesting electronics for the next launch after that.
If you’ve built and launched any rockets before, you’re probably rolling your eyes at how I’m oversimplifying much of this, and you also likely already identified several inaccurate statements I’ve made. On the other hand, if you’ve never done any of this before, I probably just confused you with a bunch of inadequate and lackluster descriptions.
In fact, I’m pretty sure I’ve failed to satisfy anyone at all with this post. But then, who cares?
The escape velocity of social media
When I haven’t been busy gluing rocket parts together – and gluing them to myself – I’ve been setting up some social media accounts for all my rocket-related adventures. You may notice these nifty little colorful icons at the top of the sidebar now, too. They’re pretty self-explanatory, but check them out and be sure to follow me and subscribe!
High power rocket: Unboxing this mother
As I mentioned in my last post, I ordered a kit to get started with building my first high power rocket. The first thing that I realized is that this kit has a lot of parts. You can see most of it in the picture above, but let me be clear: I have no idea what I’m doing. I didn’t even realize there were multiple tubes inside other tubes until much later. Why so many tubes? And those little bags are just full of more tiny pieces of hardware.
As if to make the situation even more confusing, some of the parts that came with the rocket kit are not actually necessary to build the rocket, and in fact cannot be used at all in this rocket build. (One such example is the appropriately named “baffle” that came in this package.) And yet, other parts that are critical to completing the rocket do not come in this kit, and they need to be purchased separately. Instructions are mercifully included, but they’re more like an overview for someone who is familiar with all the parts. They’re also entirely composed of text – no pictures or diagrams. The lack of clarity rivals IKEA product assembly instructions.
It is starting to dawn on me that building a high power rocket is not as easy as I assumed it would be.
But it is fun. The major parts that come in the kit, and what you can see in this picture, are basically the rocket airframe/ body tube, nose cone, wooden fins and centering rings, wooden electronics bay, and two parachute recovery systems, with shock cords. All the basic parts needed, more or less, to build and fly a large rocket.
Except for brains and ability, which I currently lack. But I can figure that out later, right..?
You might be asking yourself: HyperLOC 835? What the hell is the title of this post referring to?
I will tell you. But first, you should know that ending a sentence with a preposition is technically grammatically incorrect.
As I’ve mentioned previously, I am getting started with high power rocketry (“HPR”). As you might suspect, I have no idea what I’m doing and no clue where to get started, so I did a lot of googling. I discovered that LOC Precision is a pretty well known company that sells large rocket kits, and so I bought a kit for the HyperLOC 835. It’s just the name of this particular rocket design.
This is a hefty rocket. Once built, it will be 74 inches tall, and it’ll weigh 60 oz (or just under 4 lbs). The body tube or airframe has a 4 inch diameter. It should fly to over 4,300 feet, although this depends entirely on the motor used. It also has a 54mm motor mount tube, which is on the larger side. From what I understand, 29, 38, and 54mm are all very common diameters for the motor, although other sizes exist as well.
Aside from the fact that it looks cool, this particular rocket has the advantage that it can be used for both level 1 and level 2 certifications. The main difference between L1 and L2 is just using a bigger motor (although I’m glossing over some other important details, but right now, it doesn’t matter). Rocketry is a fun hobby, but it’s not exactly cheap – so while my L2 certification is still a ways down the road, it’ll be nice to be able to use the same rocket again for that.
Kits don’t come with motors, so I also bought a high power “I” motor, manufactured by Aerotech. These motors are basically just explosive devices and so it’s considered a hazardous material (HAZMAT) for transportation and shipping purposes. More on this motor in a future post.
One thing I’m quickly learning is that a kit is a great starting point, but it definitely does not provide you with all the parts you need. There are several things I’ll still have to buy separately, in addition to the motor. These include:
- Forged eyebolt. This is just like a regular eyebolt, but someone has fraudulently copied it.
- Fire blanket. This is the blanket that emergency responders will use to delicately wrap and then quickly remove my body after it’s been scorched during an ill-fated fiery liftoff.
- Motor retainer. A motor’s underrated alternative to wearing braces. Prevents the motor from moving over time and from being scolded by its dentist.
But enough of these additional parts. Time to unbox everything and begin assembling this mother!
Higher and higher
To recap my whole journey so far: as of just a few months ago, I had never built or launched a model rocket of any size. I’m not sure I’d even ever seen one in person (I actually don’t know how I managed that). I started out by googling whether it’s even legal to launch a rocket at all. (For the record, it is.) But I bought one small simple kit, put it together and launched it. And then another, and another.
I’m still at the very beginning of all this, but I’ve now built and launched four separate low and mid power rockets. Some were physically small and others were large. Some required more assembly and construction than others, like sanding and painting. But I now have a decent understanding of the basic parts of a rocket, how they all go together, and how the launch process works. I can’t say I’ve mastered all the basics, but I’m much more comfortable now than I was when I started.
I’ve also just begun to scratch the surface of what can go wrong.
I’m ready to dive into high power rocketry (“HPR”), which is both more exciting and more challenging. In some ways, a high power rocket is just a bigger version of a low power rocket. You have the same basic parts – cardboard body tube or airframe, wooden fins, plastic nose cone, motor mount inside to hold the motor in place, recovery system (parachute and shock cord), and a few other things – whether the rocket is small or large.
But at the same time, HPR is in other ways fundamentally different. The key distinction for HPR is the power of the motor; an H class motor or higher generally qualifies as HPR. This is more dangerous and requires certification, as I referenced in a previous post. Organizations like the National Association of Rocketry (“NAR”) certify individuals at level 1, 2, or 3 for purposes of HPR. Even the most basic certification (level 1) requires building a high power rocket with an H or I motor, and launching it successfully (including the recovery) without any catastrophic failure or damage.
HPR starts to involve more durable parts, including a lot of things I’d never heard of: fire blankets, forged eyebolts or u-bolts, electronic bays (“e-bays”), and more.
It’s time to build a high power rocket!
Rocket launches of Athena and the Mean Machine – video highlights
Rocket launch: the Mean Machine
So last weekend, I went out to 60 Acres Field (see pic below) as I mentioned in my last post, and I launched two rockets. One was small, and the other was quite big. This post is about the bigger rocket.
The appropriately named Mean Machine is a full 79 inches in height. I myself am only about 72 inches tall (okay, 71 and a half, I’m rounding up), so this rocket towers over me, and that’s even before it gains a few more inches on the launch pad. This is by far the largest rocket I’ve built, and it uses the most powerful motors I’ve tested, so far: it requires either a D or E motor. I did a couple launches with the D first, and then the E. This is just physically a heavier rocket than the other low power models, and it makes sense that it needs a more powerful motor to carry it into the air.
Nobody could be more surprised than me that these were all textbook successful launches. I was a bit concerned that despite the gigantic empty field, a six-foot rocket might come down and do some serious damage, especially if the parachute didn’t deploy or something else went wrong. But things went smoothly. No fatalities; nobody was even impaled.
Again, the absence of any wind was extremely helpful as the rocket went nearly straight up and didn’t drift too far away. The parachute deployed perfectly each time. In one of the launches, the rocket landed almost exactly where it was launched, despite being shot about a thousand feet into the air.
Basically, this whole event was really fun, and luckily it turned out to be a successful launch and recovery on a day with ideal conditions. This will no doubt inflate my ego and give me a false sense of invincibility going forward.