July 2020 Workshop Episode

Welcome to episode 94 of The Rocketry Show We’ve been on a roll with great guest interviews lately. The team take a quick break from that this episode to focus more on the results of a few rocketry projects they’ve been working on! Jesse has been ‘fiberglassing’ a new kit, and building more rockets, but more importantly, recently launched his LOC Precision “Big Nuke”. He tells us all about those, and more! LOC Precision Big Nuke 4, which Jesse has reviewed on the show, flying on an Aerotech K550W to 3189ft! He finally got that in the air on July 17, 2020   Jesse is still putting finishing touches on a Executioner clone. Fiberglassed 29mm and full Dual Deploy Capable. Level 3 project planning including sizing, figuring weights, and which composites to use for each purpose!     Gheem has been building a beautiful X-15 kit, and he catches us up on where he is on that, as well as a few more projects. Gheem’s SNGAero X-15 Grande finishes and ready to fly!   Gheem’s original Estes Pro Series launch controller modified to use lipo batteries On July 25, 2020, CG finally got to test his Radio Telemetry system. Because of all of the “Covid 19 delays, this test ended up being a “full up” test, which means about 5 tests (each would normally have been their own launch) all happening on one launch. Liftoff of CG's Mr. Bean rocket, marking the first test flight of his flight computer / GPS / radio telemetry system! He’ll share how that went!   The receiver & antenna for CG's telemetry system. We also pull some of your emails from the Mailbag that we didn’t have time to get to on earlier episodes!

Gary Rosenfield of AeroTech and Quest Aerospace

In this episode, we talk with Gary Rosenfield, who founded AeroTech Consumer Aerospace in 1982. AeroTech makes ammonium perchlorate composite propellant motors, often referred to as simply “composite motors.” This distinguishes them from the traditional model rocket motors, which use black powder propellant.

AeroTech is known for making high power motors, up to the enormous M, N, and O impulse motors. But they also make low and mid power motors for model rocketeers.

A small selection of AeroTech reloadable motor casings

Around 2014, AeroTech merged with Quest Aerospace, a model rocket company which manufactured kits and black powder motors. The motors were rather similar to the Estes black powder motors, but included the much-loved Q2G2 igniters.

An Estes C6-5 on left, with a starter. An old Quest C6-5 on right, with the Q2G2 igniter.

Q2G2’s were fast igniters. That is, they required less amperage to fire, and with a small black pyrogen tip, they were great for igniting black powder clusters – configurations of two or more motors.

With clusters, it’s important to have all motors ignite simultaneously, or the rocket could leave the pad with one or more motors unlit. This can sometimes result in a less-than-straight flight trajectory, and it’s what makes clustering a fun challenge!

Following an accident in a port in China, through which Quest’s old motors were exported to the U.S., Quest motors and igniters became unavailable for a long time.

Bill Stine, who had founded Quest, challenged Gary to create an A-impulse motor with composite propellant.

Gary accepted the challenge, and after a long period of development and experimentation, the new Quest composite motors became a reality.

Dubbed “Q-Jets,” these little 18mm motors are the same length and diameter as standard A/B/C model rocket motors, but because they contain the more energetic AP composite propellant, Quest/AeroTech can get a D powered motor into the smaller sized casing.

A Quest Q-Jet D motor, top, is the same size as an Estes C engine, bottom. The narrow part sticking out on the right of the Q-Jet is the ejection charge well.

This is because AP propellant has a higher specific impulse than black powder propellant.

Q-Jets are fast, fun, zippy motors. And AeroTech has lots of different AP motors for rockets of all sizes.

You can get Q-Jet’s from our sponsor, eRockets.biz, by clicking here.

And you can get AeroTech motors from eRockets by clicking here.

And, hey, if you appreciate eRockets sponsoring The Model Rocket Show, let owner Randy know when you place your order! I’m sure he’d love to hear that his support is appreciated.

#93: Matt Steele on Rocket Staging (Part 1)

Matt Steele joins the show to kick start the first of at least a couple episodes on staging techniques for Model Rockets. Mr. Steele is a longtime rocketeer, owner of North Coast Rocketry, and is a Professional Rocket Scientist! Our guest, Matt Steel We first define ground rules you can follow to ensure the best probability for success. Rules adapted from professional Rocket Engineering Sciences. We think this will help hobby rocketeers a lot. The methods Matt Steele discusses can be applied any new rocketry project or technique. After laying the ground rules, we jump into the first part of this episode on multi-stage rocketry. Part two will appear in a few weeks after we have a chance to gather your e-mail questions on the subject. Later in the show, we share our first peak into new beta firmware being tested for the Flight Sketch altimeter. Thanks to listener Phil Parslow for suggesting the topic of multiple rocket stage launches!!

#92: Scott Binder of SBR Fusion Rocket

Scott Binder joins us to to talk about things at FusionRocket.Biz, and -more importantly- hangs with The Rocketry Show team to talk model rocket stories, and fun memories. :-) Scott's scratch built "sport scale" Falcon 9 rocket mentioned in this episode.     Scott's eye for detail is amazing. Check out the detail on the back end!       Launch day!! Liftoff!!!   Later, CG, Gheem, and Jesse talk shop on the projects they are working on! Enjoy!

#4 – The FAQ – Questions, Volume 1

In this episode the Rocket N00b answers some model rocketry questions – some beginner’s questions commonly asked on online forums, as well as a couple questions sent to him through social media.

“What’s the Best Glue?”

Yes, we know. This question gets asked a LOT online, and some rocketeers get tired of seeing it. But it’s a good sign – it means there are new people entering the hobby all the time. That’s good for us, as it means more people to support our vendors of kits and motors, as well as greater awareness of this safe and awesome hobby.

The long answer is on the show (the N00b does tend to ramble). The short answer: for most model rocketry applications, you want to use white or yellow glue. Brand is pretty unimportant – pick one you like. The bond formed between paper and wood with these glues is stronger than the materials themselves. If a fin breaks off, it’s not the glue that failed – it’s probably that the body tube’s paper has ripped off, or a fin has snapped at the root.

Here’s a video sent to the N00b by Kirk G. showing a strength test of various white and yellow glues.

Obviously the construction technique here is quite different from what you’d be doing when building a model rocket, but it does illustrate the point that these glues are plenty strong.

Here’s the link to the Titebond page showing the differences between Titebond I, II, and III.

And here’s a quick video from Titebond comparing the three glues.

We also talk about epoxy, CA or super glue, plastic cement, glue sticks, and finally, hot glue (DO NOT USE HOT GLUE).

The plastic cement the N00b mentioned (but couldn’t remember the name) was Plastruct Plastic Weld.

eRockets.biz

The rockets the N00b mentioned during our sponsor segment – eRockets.biz – were by New Way. You can look at all the New Way kits eRockets carries by clicking here.

“Do Engines/Motors Go Bad?”

A lot of times, people will have rocket motors from a decade ago or more. Many people on the forums ask if they’ll still be good.

The fact is that model rocket motors, whether they are black powder or composite motors, do not have an expiration date. The important thing is how they’re stored. If they’ve gone through a lot of hot and cold temperature cycles over the years, the propellant grains can crack, making them more prone to catastrophic motor failures, or CATOs.

But people have flown 30-40 year old motors with no problems.

Some composite propellants, such as White Lightning or White Thunder propellants, can have some surface oxidation on them, making them harder to light, but that’s about it. Again, temp cycling may be a problem, but if properly stored, they don’t really “go bad.”

If you’re not sure, you can always soak old motors in water and dispose of them, and get new ones. Or, heck, fly ’em. That’s what minimum safe distances are for! (Click here to see the Model Rocket Safety Code.)

“How Do You Fill the Seam Between Two Body Tubes?”

Some kits come with two short body tubes, instead of one long one, and you’re supposed to join them together with a tube coupler. A follower on Instagram asked the Rocket N00b, “How do you fill in the seam so it looks like a single tube?”

It can be done easily. But the first thing to ask yourself is if you actually want to do that. There are two good reasons not to fill in that joint.

The first is if the rocket is to be painted two colors, and the color separation coincides with the length of the body tubes.

Here’s one of the N00b’s favorite Estes rockets, the Cosmic Explorer. The top is black and the bottom white.

If you paint the rocket first, with the top black and bottom white, and only glue the tubes together at the very end, you’ll have a perfect color separation – a straight line, no bleed through of the black paint onto the white – and because of the color difference, you won’t see the seam.

The second reason is you might want to convert the rocket into a payload carrying vehicle. Some kits come with a payload section. Instead of a hollow tube coupler, they come with a balsa bulkhead called a nose block. 

But even if there’s just a coupler, you can make your own bulkhead from heavy card stock, balsa, or basswood, add a small loop of Kevlar string, and now you have a payload section. Instead of blowing off the nose cone, the rocket will separate at the coupler during parachute ejection. You can fly your payload (such as an altimeter) in the upper section and keep it safe from ejection gasses.

The Estes U.S. Army Patriot is a perfect kit for this conversion. So is any kit with two tubes.

But if you do want to make one seamless tube out of two, you can use Elmer’s Carpenter’s Wood Filler.

Thin it until you can brush it on with a paint brush, and coat an area around the seam about two inches long. Once it’s dry, sand it smooth. Even if the tubes are a little uneven in their thickness, the wood filler can cover that up. The rocket will be slightly thicker in that spot, if you measure it with a digital caliper, but you won’t see it.

The Estes Hi Flier XL comes with a two part body tube. Elmer’s CWF brushed on the joint and sanded smooth can conceal the line.

“What Kinds of Cameras Can You Put On a Model Rocket?”

A number of small video cameras can be attached to a model rocket to record the flight. A very popular kind is called an 808 keychain camera. This little “spy camera” looks like a key fob. They’re cheap and compact, and can simply be taped to the side of a rocket with electrical tape.

These little cameras range from very cheap (less than $10) to not so cheap (some cost between $70-90). Quality varies a lot, but even the cheap ones may be good for fun.

Little cameras like this can simply be attached to the side of a rocket with electrical tape.

MateCam seems to be a popular brand among rocketeers. Aside from video quality being on the better end, MateCams have a larger lens assembly. You can take one apart and arrange its guts to fit a special project.

The little cameras the N00b mentioned are called flash drive cameras.

There are a number of kinds of so-called “flash drive cameras,” but the ones referred to here can be found on eBay for less than $9.

Here’s video of the hidden camera payload rocket, the Ceres B booster with ICU2 payload, the design of which came from Mike Westerfield’s book, Make: Rockets: Down-to-Earth Rocket Science.

#90B – Ken Biba and ARLISS

  ARLISS Pushing the boundaries for student STEM programs, ARLISS is a unique rocketry program where members of the Level 3 High Power Rocket community team up with scientists worldwide along with several student organizations to allow them to design "soda can sized" payloads to launch to near space.  These payloads are typically small electronic instrumentation packages designed to carry out whatever scientific experiments the students wish to perform! ARLISS Launch Ken Biba has been involved with the group for many years, and he joins us to discus ARLISS activities and more!   Typical ARLISS Mission Profile.  

#3: K’Tesh! A Chat with Jim Parsons, OpenRocket Wizard

The Omega booster and Cineroc, simulated in OpenRocket by our guest, Jim Parsons

In this episode, we talk with Jim Parsons, who was once described as “the Chuck Norris of OpenRocket.”

OpenRocket is free model rocket design and simulation software which runs on Java. You can download it here, and play around with it if you’ve never tried it before.

OpenRocket is a great tool – and it’s free. But it does have its limitations.

If you make a sim of a kit, you might notice that it doesn’t look exactly like the kit you’re building. One big difference you’ll notice is the nose cone. All nose cones in OpenRocket (except for the elliptical ones) come to a sharp point, which isn’t the case in most model rockets. Usually nose cones are spherically blunted.

Jim Parsons’ OpenRocket version of the Estes Der Red Max, with an accurately-shaped nose cone

Now, for a flight simulation, this may not matter much. To find the center of pressure, model rocket simulators use what’s known as Barrowman equations, a system of mathematically locating the CP on a model rocket. These were derived from the math used in sounding rockets, and were published as an R&D report at Naram X in 196X by James Barrowman. (Click here to see the N00b’s interview with James Barrowman at NARCON 2017).

One of the simplifying principles of Barrowman equations are the assumption that all nose cones come to a sharp point.

But what if you want a simulation that looks like the actual kit? What if you’re trying to clone a historic, out of production model? Or you want a good reference for decal placement?

Jim has figured out how to trick OpenRocket to simulate accurate looking kits of all kinds. Some are quite challenging, because of features on the model that OR isn’t built to re-create. Check out this masterful sim of the Estes QCC Explorer.

The intakes on this model were challenging. Read about it here.

While most of K’Tesh’s sims can be used for flight simulations, due to the limitations of OR, there is the occasional model sim which is mostly just for show. The A.C.M.E. Spitfire, by FlisKits, is one such example.

This version of the A.C.M.E. Spitfire is about as close as OR can get.

The N00b has used some of Jim’s files and images to figure out the decal placement and paint scheme measurements on a number of builds, like his recently-completed Semroc Bandit and Semroc Cherokee D.

The N00b’s Cherokee D, a Retro-Repro by Semroc

Jim joins us from China, where he lives and works. He and the N00b discuss OpenRocket, chat a little about model rocket history, and the challenges of pursuing the hobby while living in China.

Check out K’Tesh’s master list of sims on The Rocketry Forum by clicking here :

https://www.rocketryforum.com/threads/kteshs-openrocket-files-index.148212/

#89: Listener feedback, High Power Rocket safety, and Rocksim 10

In this episode: CG and Tripoli Northern Ohio http://northernohiotra.com Prefect Chris Pearson discus high power rocketry safety tips to use during prepartion phases before launch. This advice encompasses all of the recent Tripoli recommendations as well. Chris Pearson We get some interesting thoughts & design modifications from a listener on CG's centrifuge tube ejection charges. If you are looking for places to buy these tubes, here are a couple of links to what CG uses: From Amazon.com From Granger   One of CG's Ejection charge centrifuge tubes.   Also, CG and Gheem take their first peak at Rocksim 10! https://www.apogeerockets.com/RockSim/RockSim9_Features