Meet the plesiosaur: a gigantic aquatic reptile

There’s a common misconception that any kind of large prehistoric animal is a dinosaur – from a t-rex to the flying pterodactyl to the woolly mammoth.

When I first heard this, I couldn’t believe it. Did people really believe that a woolly mammoth qualified as a dinosaur? Obviously a woolly mammoth was covered in thick fur (hence the name), which makes it a mammal, even if you knew nothing else about it. They just aren’t reptilian like dinosaurs.

But flying prehistoric reptiles (like pterosaurs) and swimming prehistoric reptiles (like plesiosaurs) – those were just different types of dinosaurs, right?

Wrong.

Until recently, I didn’t realize that plesiosaurs and pterosaurs are not considered dinosaurs. I had mistakenly lumped them all together. True, they were all reptiles and they lived during the same geological time period (the Mesozoic Era), but they were sufficiently different from an evolutionary and biological perspective that they aren’t categorized as dinosaurs at all.

long necked plesiosaur underwater
meet the plesiosaur

Plesiosaurs were a group of long-necked marine reptiles that lived during the Mesozoic Era, from the late Triassic period, through the entire Jurassic period, to the late Cretaceous period (roughly 225 million to 80 million years ago). Some, but not all, types of plesiosaurs continued to exist until the end of the Cretaceous period, about 66 million years ago. This is approximately the same geologic time period as the dinosaurs.


While the name “dinosaur” means “terrible lizard,” the name “plesiosaur” means “close to lizard,” an appropriate name since they were admittedly similar in many ways to the dinosaurs. 

The world map looked extremely different hundreds of millions of years ago, but plesiosaurs were geographically distributed in many areas, throughout the Pacific Ocean and near what is now North America, Europe, Australia, and Asia. 

Early in their history, plesiosaurs split into two different lineages – pliosauroids and plesiosauroids. The latter had a longer neck that was very flexible. Interestingly, later on, plesiosaurs increased dramatically in size (up to 43 feet or so) and the neck reached extreme lengths. with half the total body length consisting of the neck and head. And the jaws had an estimated biting force of around 33,000 psi, possibly the largest known bite force of any animal!

plesiosaur skeleton

There is even some evidence that plesiosaurs may have been warm blooded and gave birth to live young, rather than laying eggs. Of course, there is significant debate about whether some dinosaurs were similarly warm blooded, but that is a topic for another post…

Further reading:


Britannica

https://www.britannica.com/animal/plesiosaur


The Plesiosaur Directory

https://plesiosauria.com/


Wikipedia

https://en.wikipedia.org/wiki/Plesiosauria


ThoughtCohttps://www.thoughtco.com/plesiosaurus-1091520

Which dinosaur had the longest neck?

When most people imagine a dinosaur, they might initially think of a large, menacing tyrannosaurus rex, or the slow and lumbering stegosaurus with huge plates along its back, or the three-horned triceratops with its massive frill or crest above its neck. But one of the most frequently recognized types of dinosaurs is a sauropod.

As mentioned in my last post, all dinosaurs are generally divided into two categories: saurischia (“lizard hips”) and ornithischia (“bird hips”). Within saurischia, it’s further broken down into theropods (bipedal carnivores like t-rex) and sauropods.

Sauropods were plant-eating dinosaurs that walked on all four legs and had extremely long necks, with relatively small heads. They grew to colossal sizes and were the largest animals to have ever walked the earth. Technically blue whales are larger, but they live in the ocean and don’t have to deal with the constraints of gravity, so it’s apples and oranges in terms of a comparison. Some of the most well known sauropods are brontosaurus (now known as apatosaurus, though this is a heated debate among some paleontologists) and brachiosaurus.

dark rendering of long-necked dinosaurs
mamenchisaurs (artwork by cheungchungtat)

It’s true that a lot of sauropods had very long necks – it seems to be one of their defining features. But the long neck is intriguing, and it raises several questions. Why is the neck so long? Structurally speaking, how was this possible? And which dinosaur had the longest neck?


It’s always hard to say anything with total certainty about animals that went extinct more than 66 million years ago. I had never heard of the “Mamenchisaurus” until recently, but it seems to be a strong contender for dinosaur with the longest neck, and in any pictures (whether skeletal or depictions of what it probably looked like in real life) it’s startling. The Mamenchisaurus was approximately 60 feet in total length, and a good 30 feet of that was just the neck. Relative to its body size, this animal had the longest neck of any known dinosaur.

The Mamenchisaurus lived in what is now China (though of course the map looked very different back then) and seems to have lived during the Middle and Late Jurassic, and possibly in the Early Cretaceous.

long-necked dinosaur
how’s the weather up there?


At first, I thought that the purpose of the long neck would have been to reach really tall vegetation and trees, like modern giraffes. But it seems more likely that the dinosaur used its neck more horizontally to reach medium height or lower level vegetation, and the benefit in neck length was instead to sweep across much larger areas. This way, it didn’t need to move its body much (if at all) while feeding. No doubt this saved a lot of energy considering the colossal size and weight of the body!

Further reading:

Meet Mamenchisaurus, American Museum of Natural History


https://www.amnh.org/exhibitions/sauropods-worlds-largest-dinosaurs/meet-mamenchisaurus


Mamenchisaurus, Wikipedia

https://en.wikipedia.org/wiki/Mamenchisaurus


Mamenchisaurus, Natural History Museum, London, UK


https://www.nhm.ac.uk/discover/dino-directory/mamenchisaurus.html


Mamenchisaurus, Prehistoric Wildlife


http://www.prehistoric-wildlife.com/species/m/mamenchisaurus.html

Dinosaurs 101: Theropods and t-rex

Continuing the temporary non-rocketry theme from my last post –

I signed up for two classes beginning in early January: chemistry, which is an accelerated course that crams three months’ worth of material into four dense weeks, and a geology course all about dinosaurs, which takes place at a more reasonable pace. They’re both virtual classes, given the ongoing pandemic. Both have been really fascinating, and everyone loves dinosaurs, so I figured I’d post something about tyrannosaurus rex or a colossal, lumbering brontosaurus (or apatosaurus – more on that later).

Just as background, dinosaurs are generally divided into two major groups: saurischia and ornithischia. Within the saurischia group, it’s broken down even further into theropods and sauropods.

Theropods are a fascinating and really diverse group of dinosaurs, and at the risk of overgeneralizing a bit, theropods are meat-eating predators with very large and very sharp teeth. They had big heads and jaws, and they evolved to run at fast speeds on two legs, something that is obviously quite unusual among any animals, either back then or today. Their arms and hands were notoriously tiny (think t-rex arms), just because they weren’t that useful. Chasing down prey and catching it in your jaws requires powerful leg and jaw muscles, but not hands or arms, necessarily.

Speaking of tyrannosaurs, there have been some interesting recent discoveries about a baby t-rex.

baby t-rex, appears fluffy like baby chick
fluffy


The background on the recent discoveries is that a tiny jaw fossil was found in Montana in 1983, and decades later, another tiny foot claw fossil was discovered in 2018 in Alberta, Canada. Both were roughly 71-75 million years old. Researchers didn’t know what they were looking at right away, but eventually realized that both fossils belonged to a baby t-rex. The jaw was extremely small, but it closely resembles other known t-rex jaws. 

What these fossils meant – for the rest of us non-paleontologists – is that a baby t-rex was extremely small compared to an adult t-rex. Babies, when they hatched, were about 3 feet long, compared to the adult that was up to 40 feet in length! 

What makes these discoveries so unusual is that there aren’t very many fossilized baby or young dinosaur skeletons in general, partly because the bones are so tiny and fragile. And while things like feathers don’t fossilize (as skeletal bones do), there’s indirect evidence that the baby t-rex would have hatched with feathers, looking kind of like a fluffy baby chicken – but much bigger and with a long tail, and presumably more menacing. 

The babies also had a different set of teeth, and it seems that they went through several sets as their diets changed as they grew older and larger. Dinosaurs are nothing if not chock full of interesting facts, and so I will leave you with one final impressive fact: once the babies grew into adults with their final set of teeth (and massive heads, jaws, and corresponding muscles), they could bite through anything, including bone, causing their prey to explode! This is very different from how a modern lion or tiger bites and kills its prey, which is more of a fatal bite that causes the prey to bleed out. Impressive for a creature that starts off life so small and looking like a fluffy chick.

Further reading:

American Museum of Natural History: What Did a Baby T. rex Look Like?

https://www.amnh.org/explore/videos/exhibits/growing-up-tyrannosaurus-rex


Baby tyrannosaurs dinosaurs were the ‘size of a Border Collie’

https://www.bbc.com/news/uk-scotland-edinburgh-east-fife-55796799


First tyrannosaur embryo fossils revealed

https://www.nationalgeographic.com/science/2020/10/first-tyrannosaur-embryo-fossils-revealed/

Off to the races in 2021: new year, new baby

Wow! It’s been a while since my last post, so I feel obligated to provide some sort of explanation. It’s been a busy start to the new year. My wife and I had our first baby, Ava, near the end of January, and there was a tremendous amount do in preparation for her winter arrival. And of course there’s been even more to do ever since she joined us nearly four weeks ago! As you might expect, the past month has been a complete blur. We’re a bit overwhelmed but are managing to adapt to life with a newborn. We’re extremely fortunate that everything went well, and we have a happy and healthy baby.

newborn baby swaddled with eyes open
Welcome Ava!

Improbable Ventures is meant to be primarily about rockets, from theoretical rocket science to my practical misadventures in high power rocketry (much more to come on this topic soon). But it is also meant to be broader, encompassing related projects and ventures, and it’s impossible to completely separate it from my own personal life as well – which is why you might see me writing the occasional article about a class I’m taking, or a recent trip or hike I took, or a new baby.

As a sleep-deprived new father, I’m not sure that I have anything particularly profound to say about parenthood that hasn’t been said much more eloquently by other people, many times before. It’s exciting and exhausting. I thought it would be a lot of work, but it turned out to be more than I’d imagined. It’s not particularly complicated; it’s just that virtually nonstop, around the clock care is required.

More interesting than any perspective I can provide is the baby’s point of view. What a dramatic difference to go from being in the womb – totally dark, almost like a sensory deprivation chamber except for hearing mom’s heartbeat and her voice on a regular basis – to suddenly (unwillingly) being born. It must be total sensory overload, except you have no words for anything, no way to describe your experience even within your own mind, and no way to understand anything that’s happening or what might come next. The baby has never had to use her lungs and breathe on her own before, or feel hunger, do things like drink and swallow milk, and suddenly she is forced to figure all of this out – and fast.

While it’s true that babies basically just eat, sleep, and cry (there’s no shortage of crying) all day and all night, it’s remarkable that they learn as rapidly as they do!

2020: A Rocketry Year in Review

The rearview mirror

A little over one year ago, I came across a question on Quora (an internet forum) about whether it would be legal to build and launch your own rocket into orbit.

Rearview mirror in a car with road and mountains
Looking through the rearview mirror

I’d always been interested in rockets and space, but I never seriously considered doing this or even realized it was possible, or legal. How realistic is this kind of project? Do you need anyone’s permission, i.e. the FAA? The US government?

One month and an uncountably high number of Google searches later, I was actively exploring the possibilities.

Near the end of 2019 (before we had any idea what kind of year 2020 would be), I set a few rocketry-related goals for myself. I was just realizing that anyone can build and launch real, working model rockets. And they could build and launch big ones, too – high power rockets. I decided to try it out, first building a few smaller low power rockets and sending them up with a small launch pad, and then building my first high power rocket. Somewhat unexpectedly, one of the bigger obstacles I ran into wasn’t the construction of the rockets, but finding a suitable launch site. But I found a few places and had some initial successes. I set some concrete goals going into the new year.

My 2020 goals included the following:

  • build and successfully launch my first high power rocket;
  • get my NAR HPR level 1 certification (H or I motor);
  • get my level 2 certification (J, K, or L motor);
  • build my first electronics bay, learn more about flight computers, and use dual deploy for parachutes;
  • get my amateur (“ham”) radio license;
  • renovate my backyard garden shed and build a practical workshop, primarily for rocket projects;
  • get my level 3 certification (M, N, or O motor); and
  • build a two-stage rocket.

Overall, things went pretty well. I didn’t achieve everything on the list, but I did accomplish many of these things and got some high power rocketry experience under my belt – basically everything except the L3 cert and the two stage rocket. And I did actually build my L3 rocket (three separate times!) but had two flight certification attempts that were not successful, so I came close but didn’t quite pull it off. In general, I did a lot of stuff I’d never done before, and learned a tremendous amount along the way.

In short, I had a blast!

The future plans

Turning to 2021, it’s a new year and time to set some new goals. The logical starting point is with the goals I didn’t quite get to finish in 2020. Was I too ambitious? Crazy? Did I just run out of time? Who knows?

Since I already rebuilt my L3 rocket for the third time and it’s ready to fly, my first goal is getting my L3 certification. This will let me fly M, N, and O motors (and there are some even bigger ones beyond that, but first things first). There are no additional certification levels, though, after L3.

Next, I intend to build a two stage rocket. It can be fairly simple and inexpensive – no need to start off with something overly complex right off the bat – but I want to get a solid understanding of staging, and specifically staging using electronics (multiple flight computers). There are a couple important “events” with a two stage rocket, but basically the first stage (booster) ignites on the ground and “boosts” it high into the air, and then the second stage (sustainer) ignites mid-air. The first stage also breaks off and falls back to the ground at this point, reducing total weight and drag so the sustainer can fly much higher on its own. I’ll have much more to say about this two stage project once I dive in.

After that, I’d like to start on a more ambitious two stage project – something made of fiberglass, minimum diameter, and more sophisticated. Ideally I might be able to build a two stage rocket using one M and one N motor that can hit 100,000 ft, but more likely it would be a high altitude rocket that goes a few tens of thousands of feet into the air. I’ll see what’s realistic as I get closer to this goal.

In the meantime, I’m also taking some more math and science classes in 2021. Right now I’m enrolled in a chemistry course as well as a geology course dedicated to dinosaurs. The latter is entirely just for fun and has nothing to do with rocketry, but it isn’t extremely time consuming or demanding either. Chemistry is much more intense, but it’s also much more critical to rocketry, especially if I want to eventually build my own solid fuel motors or get into liquid fuel or something down the road.

Here’s to 2021!

SpaceX Starship SN-8 test launch and fiery crash landing

On December 9, SpaceX conducted a test of its Starship rocket, and it was spectacular.

Starship SN-8 silver metallic rocket standing vertically against starry blue night sky
Starship SN-8

The rocket was called SN-8 (which just stands for Serial Number 8), following the naming pattern for each new iteration of the rocket. Elon Musk originally unveiled the idea for the Starship rocket last fall, and the prototypes SN-5 and SN-6 flew about 500 feet before falling back down. This test of a more complete looking Starship went up 12 kilometers, the vehicle’s first high altitude test.

Many people in the rocketry community watched this live. Below is a great condensed/ time lapse video showing both the launch and the landing, in case you missed it:

Basically, SN-8 had a successful launch and flew vertically for 5 minutes, then began falling back to earth. After cutting its engines, it fell horizontally – the “belly flop” maneuver – which maximizes surface area to help slow its descent.

As a side note, there are a lot of principles in rocketry that are the same whether you’re building and flying a very small model rocket or a colossal commercial rocket, and one of them is drag and aerodynamics. Rockets are sleek and meant to minimize drag and air resistance when they’re moving vertically (or in whatever direction they are pointed), but they are really inefficient and have enormous drag if moving at an angle or horizontally. You’d be surprised how slowly even a large, heavy rocket falls back to the ground without any parachute when it’s falling sideways, and often in multiple (connected) separated pieces.

Starship SN-8 metallic rocket horizontal, falling against light blue sky
image credit: NASA

Anyway, back to SN-8: the belly flop was successful in slowing it down somewhat, and then its engines turned back on to turn the rocket again for a vertical landing. Unfortunately, it was still descending a bit too quickly when it hit the launch pad (perfectly on target) and it exploded in a fireball. But overall, this was an unbelievable achievement.

SpaceX is continuing to innovate and make things that were just recently science fiction into a reality.

My own progress in rocketry may be impressive, but it’s not quite at that level yet. I have some catching up to do!

Coding 101

This is a rocketry blog. It’s primarily dedicated to all my misadventures building and flying rockets. I try to document my successes, my failures, and lessons I’ve learned. But I do occasionally venture outside of rockets and try other things.

When math is prologue

For example, last year (2019) I decided to take some math classes at my local community college. There is an explanation for this, and as you might guess, ultimately it goes back to rocketry. I’m not an engineer or scientist, and I didn’t really get a solid education in math and science at the university level. My interests at the time were more in liberal arts – politics and history in particular – and so I ended up with an education in political science and law. I took a few math and science courses, but generally tried to avoid them.

But fast forward a few years, and here I am today building high power rockets. And rockets require a basic understanding of math and science and engineering, at some fundamental level. And it’s interesting, and I enjoy learning. So that’s my story.

black chalkboard full of math equations and drawings in white chalk
seems legit

I took a placement test last year at the local college and placed into calculus I (the first of a three part series). I ended up taking it, and then successfully completing the entire series over three quarters, each more grueling than the last:

  • Calc I covered the foundational topics: limits, continuity, derivatives, etc. as well as anti-derivatives and definite integrals.
  • Calc II covered techniques of integration and their application to definite and indefinite integrals, as well as some differential equations and polar and parametric equations.
  • Calc III covered a variety of topics including vectors, multivariable functions, partial differentiation, and double and triple integration, as well as series and sequences.

I’m proud to say I got an A in all three of these courses, but it wasn’t easy. In fact, each of them really pushed me to the limit to understand and master a tremendous amount of new (and complicated) material. The studying was intense, and calc III really pushed it to a feverish pitch. But I survived.

There’s something to be said for really expanding your mind and stretching your brain, regardless of the subject matter. I don’t deal with any math in my daily job, and a lot of the concepts in calculus are really fascinating. (If you don’t believe me, you might just need to try a better instructor. Check out Sal Khan’s lessons on Khan Academy, which I used early and often.)

On a related note: did you know that whenever you learn something new, your brain is literally physically re-wiring itself, growing new pathways and connections between neurons? That alone is a great reason to dive into something new and learn.

But I’m off on a tangent (no math pun intended). While 2019 was the year of math for me, 2020 has been the year of the rocket. I’ve documented this elsewhere on the blog, but this past year has been a wild ride: I built and flew my first (and second, and third) high power rockets. I got my level 1 and level 2 certifications in high power rocketry from NAR, and I made two attempts for level 3, which is the pinnacle of high power, at least in terms of formal certifications. (Admittedly both L3 attempts were unsuccessful, but I learned a lot, and I’ll get my L3 eventually.) I got an amateur “ham” radio license so I could use a flight computer with radio telemetry in my rockets, and I retooled the garden shed in the backyard as a rocket workshop. I think I did some other stuff in the past year, too, but I can’t remember everything.

Coding: all the rage

But 2020 doesn’t exclusively revolve around rockets for me. I also resumed my formal education by taking another class: a computer science course on programming, specifically in the Python language.

computer screen with python programming code
python programming language

I decided on this course partly because it seemed interesting – coding is, after all, extremely popular nowadays, with parents enrolling their kids in coding “boot camps” from an early age, and app development seems like a guaranteed lucrative career if not an outright path to billionaire status. But from my perspective, there’s a more practical reason – there are several engineering courses I’d like to take, and some of them require this basic computer science course as a pre-requisite. It’s nothing more complicated than that.

I’m just wrapping up the class this week, and I enjoyed it more than I thought I would. I’m not planning to quit my day job, but there’s a certain element of satisfaction in facing a problem that initially seems baffling or insurmountable, and then gradually solving it. This is just an introductory course and we only learned a few basic techniques, but once you understand them, they can be pretty powerful and can solve a wide variety of problems.

The concepts include things like: input, processing, and output; working with numbers; functions; decision structures (if/elif/else statements to test conditions) and boolean logic; repetition structures (for/while loops); value-returning functions; working with files; and sequences or lists. There’s a nice logical consistency to everything.

Now that fall quarter is ending, I have to decide what (if anything) to do for winter quarter. There are more science courses I would like to take: one is general chemistry – quite important in rocketry – and another is a geology course all about dinosaurs (!). Or I could just throw myself back into building and flying rockets. What do you think?

Going down in flames: how to self-destruct with rockets

The big day was finally here.

man standing in front of small trailer holding large red and white rocket
my pride and joy

I finished building the L3 Fusion rocket in early September and was ready to launch – once the wildfire smoke cleared in the PNW – as soon as the opportunity arose. And in late October, I had my chance.

The plan

On a frigid Saturday morning, with my wife joining the small crowd gathered at the rocket launch out near Walla Walla, WA, I went through my pre-launch checklist and got the rocket ready for flight. It was mostly ready to go – the black powder charges were prepared and loaded inside the rocket, the M-1297 reloadable motor was already built, the wiring for all the electronics was nearly complete. All I needed to do was plug each flight computer into its respective battery, turn on the GoPro camera, and seal up the rocket with a few rivets. And, of course, install the motor. Easy enough.

I’ve described this rocket before but just to quickly recap, the L3 Fusion is a 5.5″ diameter, nearly 8 ft tall high power rocket specifically designed for level 3 certification. It’s available from SBR at fusionrocket.biz and I highly recommend it. The rocket is cardboard and therefore lightweight (only 11 lbs before adding the M motor, which itself weighs another 11 lbs), but it’s reinforced and double-tubed from top to bottom, and then coated with an epoxy – basically making the rocket incredibly strong despite the light weight. On an M-1297 motor, this thing should fly to 9,000 ft or higher.

The key word, of course, is “should.”

I was a bit nervous, but mostly hopeful and excited. The temperature that morning was brisk – around 30 degrees F – and it didn’t take long for my fingers to get cold and then start to feel numb. It’s particularly difficult when you’re trying to mess with very tiny wires and electronics – think eyeglasses screwdriver (which is literally what I was using to attach wires to flight computers).

man holding large rocket horizontally above his head, walking through field
getting the rocket on the pad

But I had built this rocket entirely under the watchful eye of the man who designed it, with his recommendations. We even filmed the entire build as a tutorial for future generations, so this event might go down in history. I can’t say I built the rocket flawlessly, but I was pretty confident the flight would be successful.

As you have probably guessed by now, it was not.

rocket launching with cloud of smoke underneath
L3 Fusion liftoff!

The disaster

The countdown began: 5… 4… 3… 2… 1…

With a thunderous roar, the rocket shot off the pad and climbed into the sky with lightning speed. An M motor is a pretty powerful one, and so this was expected. What was not expected was just a few seconds into the flight, as we watched it ascend and disappear into the sky, was another loud boom. The smoke behind the rocket, which was otherwise basically a vertical line, suddenly changed as the rocket veered sharply from its trajectory.

It broke up and fell back to the ground in multiple pieces, and the certification attempt was a bust.

We mounted a search with half a dozen people scouring the hilly area where we saw the parts land, and we were able to find and recover everything except for the rocket’s three fins. The fins were completely torn off, but a lot of the rest of the rocket was largely undamaged. We even found the electronics, despite the fact that the e-bay fell separately from the rest of the rocket and it’s quite small and difficult to spot in small bushes and tall grasses on a hill.

damaged rocket parts scattered on ground
the aftermath

The aftermath

You can learn a lot from studying a rocket failure, just by seeing what happened to the airframe. You can sometimes learn even more if you recover the electronics and download the flight data (assuming they’re still working properly), and/or from an onboard camera like a GoPro.

In this case, it seemed obvious that the fins experienced fin flutter, which is a phenomenon where the forces acting on the fins are much higher than they should be under normal flight conditions, and the extreme vibrations can either change the rocket’s trajectory or even destroy the fins.

Leaving aside complicated discussions of aerodynamics, fins are really important to a rocket. The rocket itself is streamlined and has a motor at the bottom which accelerates the rocket upwards (vertically), but anytime the rocket deviates from that vertical path, the fins stabilize it. The air pushing against the broad fins with large surface area pushes the bottom of the rocket back into place. It’s an ingenious system that self-corrects without the need for a sophisticated computerized guidance system. (Very sophisticated and large rockets tend not to have fins precisely because they do have such computerized guidance systems.)

Without fins, the rocket has no stability. In this case, the moment one or more fins were damaged due to flutter, the rocket careened significantly off its straight trajectory. Since it was still traveling at very high speeds just a few seconds into the flight, the forces acting on the rocket were tremendous and it was almost instantly destroyed.

close up view of damaged rocket with missing fins
the fin can, minus fins

As you can see in the picture above, the entire bottom of the booster section of the airframe was destroyed and all three fins were torn off. Some of the rest of the airframe was damaged, despite the fact that it was double tubed and reinforced with some serious epoxy. And the drogue (smaller) parachute disappeared into oblivion.

But much of the rocket was surprisingly undamaged. The larger parachute never even unraveled and was completely fine, along with both white shock cords connecting everything together. The nose cone and electronics were in great condition as well. Unfortunately both flight computers had their batteries ripped out during this event so they lost power and stopped recording data after the first few seconds, but both are in perfect working order and only needed new batteries, an easy fix.

The conclusion

It also seems clear that the cause of the fin issue was my own flawed construction technique. Typically, with previous rockets, I’ve built the fin can (i.e. the section of the rocket consisting of the motor mount tube and the fins) outside of the larger diameter rocket airframe, and then inserted the fin can into the airframe. This allowed me to use plenty of epoxy attaching the fins to the motor mount tube at the root edge of the fin, and to build up thick epoxy fillets.

In this case, however, I inserted the motor mount tube into the airframe first, and then attached the fins “through the wall” of the airframe tube. I likely didn’t use nearly enough epoxy on the root edge of the fins when inserting them – and because of this, at least one was yanked off during flight when it experienced flutter.

The reboot

I knew what I had to do. Rebuild the entire rocket (salvaging a few parts from the original if possible, like the parachute and shock cords) and this time, build the fin can outside the airframe and use plenty of epoxy on the fins. Make sure those fins are securely attached and incredibly strong.

Which is exactly what I did, for my level 3 certification attempt #2, just three weeks later.

How did that attempt go, you ask? Well, let me go put on some coffee and I’ll tell you all about it..