5 reasons to put electronics into your rocket
I’m just beginning to learn about the different kinds of electronics that can go into a rocket. It seems like there are virtually limitless possibilities, but I’ll give a quick overview below.
A high power rocket often has an electronics bay (“e-bay”) or some payload area where you can put various types of payloads, generally electronics.
The options are really endless, but just to help provide some overall context, here are a couple of the major types or categories of electronics that can go into a rocket.
- Altimeter. This is a simple device that measures altitude, or height. It uses changes in barometric pressure to determine height (starting by setting it to zero at the launch site, so that it has a starting point). It’s fun to launch a rocket, but it’s nice to know exactly how high it goes. I’ve heard great things about the RRC3 from MissileWorks, for example, as well as the StratoLoggerCF altimeter.
- Parachute release. If you wrap the parachute with a rubber band so that it’s closed tightly, it won’t automatically open when it’s released at peak height. By using a very small chip, such as the Chute Release from Jolly Logic, you can control when that parachute actually opens up and deploys.
- GPS/ radio beacon. It’s helpful to know exactly where your rocket goes, using something to record position data. It’s also helpful for finding your rocket after it inevitably disappears from sight and you have no idea where it landed. I’ve heard several people recommend the BeeLine GPS, for example, from Big Red Bee.
- Flight computer. This is a small chip (e.g. the one pictured at the top of this page) that integrates several useful functions into a single device. A flight computer generally contains an altimeter and GPS/ radio beacon, but also contains “pyro channels” which can control parachute deployment. A flight computer allows a rocket to “dual deploy,” meaning you can deploy two separate parachutes, and you have a greater degree of control over when the rocket parts separate and the parachutes actually deploy. The flight computer pictured above is the TeleMetrum, from Altus Metrum.
- Camera. Is there any limit to how creative you can get with putting electronics into a rocket? Not really! I’ve just begun to scratch the surface, but I know people put a GoPro or other camera on the outside of the rocket and record video during launch, so that you see the earth receding underneath. For some of the biggest rockets, you can even glimpse the horizon and the edge of the earth’s atmosphere.
My initial goal is to just figure out what I’m doing (I have no experience working with electronics) and put together the basic parts to create a functional e-bay with a flight computer. This is one of my 2020 goals – and specifically a January 2020 goal because I have a lot more to do this year.
What to see at the Museum of Science & Industry in Chicago
When I was visiting family in Chicago for the holidays, I got a chance to check out the Museum of Science and Industry (“MSI”) and in particular, the Henry Crown Space Center. I was born and raised in Chicago and I’ve been to MSI many times when I was younger, but it’s been a few years now. They’ve remodeled and changed exhibits countless times, and I can’t remember having seen the space center before.
Needless to say, it was awesome! There are areas dedicated to each of the major US human spaceflight programs, explaining their purpose. These programs and their stated goals include:
- Project Mercury (to orbit a manned spacecraft around earth, to investigate humans’ ability to function in space, and to recover both person and spacecraft successfully),
- Project Gemini (to rendezvous and dock two spacecraft), and
- Project Apollo (to land men on the moon and return them safely to earth).
As pictured here, the exhibit included an actual manned capsule from Mercury and an actual module from Apollo. These were on loan to MSI from the National Air and Space Museum. There’s also a rock on display from the lunar surface. It’s really impressive to see these things in person; mind-blowing when you stop to think about it.
If you want to see more photos, check out my instagram, but I wanted to at least share some highlights from the exhibit on the blog as well. Chicago is renowned for its world-class museums, and MSI doesn’t disappoint.
The space center also had some areas dedicated to modern and future space missions, including info about SpaceX (see picture below), Blue Origin, Virgin Galactic, and other private companies, as well as current NASA projects and plans.
I’m enjoying launching model rockets and getting into high power rocketry, but it’s pretty inspiring to see a huge exhibit like this. It gives me motivation to set more rocket-related goals (and crush them) in 2020!
The goals that I forgot to mention
I listed my top 5 rocket-related goals for 2020 in my last post, but I am quickly realizing that an appendix is necessary.
It’s not just that I feel the need to go into further detail. Sure, each of those goals I already listed can be (and needs to be) broken down into multiple sub-parts. For example, in transforming my backyard shed into a workshop, I need to do a couple of major things:
- clean it and haul out a bunch of junk;
- knock out parts of the wall, frame window locations with wood, and install windows for natural light;
- wire it with electricity by running conduit from the main power supply in the house;
- install new wooden countertop for work surface;
- install light fixtures;
…and so on. Each of these has sub-parts as well – you get the idea. That will be a decent sized project. But aside from my previous post, I also need to add a few extra things to my list of what I want to accomplish in 2020:
- Write an “instructable” on how to build a high power rocket. One of the reasons I got into rocketry to begin with was that I came across a really good instructable on HPR.
- Learn more about the laws and regulations governing spaceflight and rockets (manned and unmanned) and write and publish an article on this topic, maybe in a law journal. I was inspired by an article I saw on Politico recently.
- Get an amateur radio (“ham radio“) license. I’ve never really considered this until recently, but it’s becoming increasingly obvious to me that having such a license would be extremely useful when adding electronics to a rocket, since the ground station communicates with the rocket via telemetry, through radio. In fact, I’ve been looking at the TeleMetrum flight computer recently for the electronics bay in my rocket, and to legally operate a TeleMetrum flight computer system in the US, you need at least a “Technician Class” amateur radio license from the FCC.
So.. I’d better get started!
New year, new me: Goals for 2020
Farewell, 2019. Bring on 2020.
I’ve only recently gotten into rocketry, so I feel like I’m moving pretty quickly. Prior to a few months ago, mid to late 2019, I’d never even built or launched any kind of model rocket, even a small one.
Fast forward to today, and I’ve built and flown several rockets. I’ve even assembled a high power rocket and I’m on the verge of launching it (just need to find a high power launch event/ location)! Assuming the flight and landing are successful, I’ll get my level 1 certification through the National Association of Rocketry (“NAR”) for high power rocketry.
It’s a fitting time to say goodbye to one year and to welcome the next one. Now is when people generally step back and take stock of where they are in life, and what they want to accomplish in the next year.
So in that spirit, below I’ve listed my major rocket-related goals for 2020. They say a goal properly set is a goal halfway reached. Right? Right??
- L1 cert. Get level 1 (“L1”) certification in high power rocketry, using a rocket with an H or I motor.
- Build an electronics bay. Learn more about electronics and build a functioning electronics bay (“e-bay”) with a flight computer for use inside a rocket, capable of dual deployment (electronically deploying two parachutes at different heights).
- L2 cert. Get L2 certification in HPR, using a rocket with a larger J, K, or L motor and a functional e-bay.
- Build a workshop. Transform backyard shed into rocketry workshop.
- L3 cert. Get L3 certification in HPR, using a custom-built large rocket with an M, N, or O motor.
I’m actually not even sure this is all achievable in a single year, even if I go all out and work as hard as I can. From what I understand, people who build and launch high power rockets often take years between each certification. According to NAR, only 1,677 people in the entire U.S. are currently L1 certified; only 613 currently have an L3 cert.
But that’s ok! What would be the point in setting goals if they were easy to achieve?
Let’s do this 2020!
How to install a rocket motor (without blowing yourself up)
Rocket motors are basically small explosives, so they are understandably treated as hazardous materials for purposes of transportation and shipping. Of course, you can be pretty confident they are safe: these motors are generally produced by large companies that have a tremendous amount of professional expertise, as well as hefty insurance policies.
Two companies primarily manufacture high power rocket motors: Aerotech and Cesaroni.
For my first high power rocket flight, I purchased an Aerotech I-140-14A “White Lightning” single-use motor with a 38mm diameter.
The “I-140” means that this is an “I” class motor (H or above in the alphabet is considered high power), and the 140 is the total thrust, measured in Newtons (N). In terms of high power rocket motors, this is not terribly powerful, but it’s still significantly more powerful than anything I’ve ever launched before.
The 14 is the number of seconds in the delay, after the motor propellant burns out, before the ejection charge fires to separate the rocket body and deploy the parachute.
“Single use,” as the term implies, means that this motor can be used once. The alternative is a reloadable motor. I plan to try these in the future, but single use is the most simple and straightforward type of motor.
The 38mm is the diameter of the motor; you would typically buy a rocket motor that fits into the rocket’s motor mount tube. The diameters of 29mm, 38mm, and 54mm are all fairly common in HPR, although there are even larger sizes too. You can also always buy a smaller diameter motor for a larger rocket, and secure it using a motor mount adapter, which is just something that fills the extra space between the smaller motor and larger rocket tube, centering it carefully.
Since I have a 38mm motor and a rocket with a 54mm motor mount tube, I have just such an adapter, and I’ll cover building and installing the adapter in another blog post. A key consideration is making sure the motor and the adapter are completely secured with some sort of a retainer (e.g. ideally not just masking tape).
The motor here comes in a fancy yellow cardboard tube. Inside is also an igniter and a tiny vial of black gunpowder. The motor comes with instructions, but basically the gunpowder is inserted into one end of the motor and then covered with a plastic cap to seal it in. Later, when the rocket motor burns out, there will be a delay and then an ejection charge (shortly after apogee). The explosive force will be amplified by the black powder.
The motor is placed into the rocket like any smaller motor: inserted into the aft end of the rocket, after loading and securing the gunpowder on one end, and attaching the igniter on the other end. The only additional complication here is that I’m using the adapter, as mentioned above.
That’s it! The motors in HPR (and their installation) are really very similar to those in low or mid power rocketry, with small model rockets. The biggest difference is just the amount of propellant, and consequently, the amount of thrust.
Definitely looking forward to launching this thing, although I am expecting something less like the Falcon 9 and more like the Hindenburg.
Why I drove 7 hours through the mountains to a rest stop
I recently finished building my first high power rocket, and mentioned in my last post the difficulties involved in finding a launch site, especially at this time of year. I’d need to find a local rocketry organization that has a launch site (i.e. either owns the land or has permission to use it) and secures the FAA waiver for the appropriate date, and then – weather permitting – I could launch. Unfortunately, this is all easier said than done.
There are only a handful of organizations in the PNW, and most of them don’t hold any launch events in the winter. I did come across one group, Gorge Rocket Club (located in northwest Oregon) with a promising launch calendar even in winter months, and there was a recent weekend with a scheduled launch. I decided to go for it.
The FAA waiver allowed a launch window of just a few hours starting at 9:00am, and the location was in Goldendale, WA, which is a 4 hour drive from my home. This meant hitting the road at 5:00am when it was still dark outside for a nighttime drive east into the mountains. No problem so far. Just need to load up on coffee and a couple of podcasts.
The drive out there would have been a bit more scenic if it weren’t in the early hours before sunrise. Due to a combination of darkness and fog, I couldn’t really see much of anything. On the way back, I did see some of the scenery; Snoqualmie Pass in particular is beautiful.
But as I drove through the pass and dawn started to break east of the mountains, I noticed the roads getting increasingly icy, and snow was beginning to fall. That’s not a great sign for a scheduled rocket launch. The further I drove, the more heavily it snowed.
Finally, as I approached Yakima about three and a half hours into this drive, I got the not-totally-unexpected news that the launch was cancelled due to heavy snowfall and no visibility. It was total whiteout conditions.
I pulled over at a rest stop to make sure it was really cancelled, and took the opportunity to make use of the facilities while I was there. Then I began the three and a half hour drive back through the mountains to Seattle (this time with some better views).
I took a picture of a sign before I left the rest stop, though. The image basically sums up my day:
I didn’t literally fall, but I definitely slipped on some metaphorical level and landed on my ass. Also, my head physically separated from my shoulders when I heard the cancellation news.
But this is all part of the fun of launching rockets. I’ve read others’ stories about their first launches where something was cancelled, or the FAA waiver never went through, or the rocket launched but then suffered some catastrophic failure. C’est la vie. It was a pretty low key scenic drive.
I may get a chance to launch again in the same area in the next few weeks, though, and if so I’ll certainly take advantage of the opportunity. Fingers crossed!
High power rocket construction: part 7 (painting)
Time for the finishing touches.
After covering the rocket in white primer, I used a can of white spray paint to coat it again – everywhere except the nose cone, which I painted red. I considered making it white, too, for a uniform (if overly simple) finish, but a major issue with painting rockets is that certain colors can be really difficult to see against the sky.
White, silver, or blue blend in too well and it’s easy to totally lose track of the rocket once it gets high enough. For that reason, rockets are often really bold and vivid colors, and also more than one color.
I added the “Improbable Ventures” logo, too. First high power rocket, but definitely not the last.
The completed rocket stands about 6 feet high. Inside is a parachute, a shock cord securing it, and a small fire blanket to protect the parachute against the extremely hot gas from the motor when it burns out and fires an ejection charge, separating the rocket in midair. There’s an electronics bay, but right now it’s empty. Prior to launch, of course, I’ll insert the motor as well.
Having built a few smaller (low power) rockets definitely helped me better understand what I was doing when building this high power one. As I’ve mentioned before, most of the basic parts are the same, and it helps to understand why you’re doing what you are doing, and not just blindly following instructions, even if they are idiot-proof. (We will see.)
The rocket is done, so my next step is to wait patiently for an upcoming high power launch hosted by a local rocketry club. But I may be waiting for a while.
While I could theoretically launch this thing by myself at any time, it’s not really practical. First, you need a proper launch pad and rails to keep it vertical during liftoff (I don’t have the equipment, but clubs do). Second, you need to find a very large area of land – many acres – that meets a long list of conditions ensuring it’s safe for launching rockets, and you need to either own it or get permission from the landowner. The launch site needs to be far away from any buildings or major roads (you don’t want a rocket crashing down, or even landing relatively softly with a parachute, in the middle of an expressway). And finally, you need to get an FAA waiver for launching high power rockets. A club will regularly apply for these waivers, which are specific to a particular date and time window.
I’ve mentioned before that our local Seattle area organization (Washington Aerospace Club or WAC) doesn’t currently have a high power launch site, so, until it does, it cannot conduct or host high power launches. There are other clubs in Washington or Oregon if I’m willing to drive 4-6 hours each way (and I am), but almost none of them host any launch events in the winter months. Things usually pick up again in March.
I just might have a slim chance in early Jan or Feb to launch with an organization in southern WA or northern OR, weather permitting (i.e. no snow or whiteout conditions). It’s unlikely, but possible. In the meantime I’m going to dive into two related projects: (1) starting to learn about electronics and building out my e-bay for this rocket (for future launches), and (2) transforming our backyard garden shed into a small workshop for rocket construction.
High power rocket construction: part 6 (applying primer)
So if you’ve been following along with this step-by-step guide at home, the construction of your new high power rocket is now complete! All the major parts are assembled, and aside from putting a motor inside, you’re ready to launch. (Note: a motor is in fact required. More on this later.)
Some people do actually launch their rockets at this point without doing anything more, like applying primer or painting or adding any decals or other finishing touches. The idea behind flying your newly minted rocket “naked” is that it’s untested and may suffer some catastrophic failure during flight – so why invest a large amount of time making it look nice?
But most people take some time to class the rocket up after building it, even before the first flight. You can spend as much or as little time as you want on this.
Here, I used a spray can of primer to cover the length of the rocket. The primer should be applied as evenly as possible, continuously moving the can and its nozzle so that it isn’t concentrated too much on any single area. Better to do many short, quick passes with the spray than to focus too long in one spot and build up an uneven surface. (Of course, it can always be sanded down to make the surface even again, but this just adds unnecessary extra work.)
Another tip is to cover anything that you don’t want to spray with masking tape before you get started, like rail buttons or the motor retainer.
Our yard and house are surrounded by massive pine trees, so this would not be an ideal place to launch a large rocket, for a variety of reasons. But that’s okay. Look at that rocket gleam in the morning light.
Next: painting and finishing touches!
High power rocket construction: part 5 (motor retainer)
Motor retainer: helps prevent costly braces and unnecessary trips to the orthodontist during the rocket’s awkward teenage years.
All kidding aside, the motor retainer is simple but important. Extremely important, actually. Anyone reading this who has flown rockets before – of any size – knows what I’m talking about.
If you haven’t, here’s the deal: a motor burns for a period of time (a couple of seconds, generally) and the explosive force shooting out of the bottom of the rocket propels it in the opposite direction. If things are going well, this direction is up, into the sky. But once the propellant burns out, after a brief delay, right around apogee, it triggers a smaller explosion at the opposite end of the motor. This is basically an ejection of very hot gas inside the rocket. That gas has nowhere to go, and cannot escape. The explosive force breaks the rocket apart, at a place where the rocket is designed to easily separate – and inside is a parachute, which gets pushed out. Science!
But the hot gas filling the inside of the rocket only has “nowhere to go” and breaks the rocket apart if the motor itself stays securely in place. If it’s not sufficiently secured, then this event will forcefully push the motor backwards, out the bottom of the rocket!
This is dangerous and is a big problem for at least two reasons. First, the motor will simply fall back to the ground, without any kind of parachute or recovery device, and it could injure someone. A high power rocket can have a pretty large and heavy motor.
Second, if the hot gas pushes the motor out of the rocket, then the rocket will not properly separate where it’s designed to, and the parachute will not have any chance to deploy. This means the entire rocket will come crashing down, which will almost certainly irreparably damage the rocket. The falling rocket – without anything to slow it down – could also seriously injure someone.
Enter: the motor retainer. This is a simple device, made of some durable metal (e.g. “precision machined aluminum”) and comes in two circular rings. One ring is permanently epoxied to the motor mount tube at the aft end of the rocket. The metal on both circular parts is threaded, and the other ring is basically an end cap that screws onto the first ring. The end cap prevents the motor inside from sliding (or violently ejecting) out the back. The reason it’s in two parts that can attach or detach is to easily allow you to insert a new motor, or remove an old one, after each flight.
Given what would happen if a motor fell out the bottom of the rocket, to both the rocket itself and any innocent bystanders below, having a high quality motor retainer in place to secure the motor can literally make the difference between a successful flight and total disaster.
Plus, it classes up the rocket.
Improbable Ventures 