A modular TARC rocket?

Now that the season has begun I have been thinking quite a bit about this year's TARC. The big change this year is that the 100 teams participating at Finals will fly not to their qualifying 800 foot altitude, but to 775 and 825 feet, 25 feet higher or lower (order to be determined by a coin toss at Finals). The traditional way of dealing with this scenario is to add or take away ballast weight from the model, but another way has occurred to me, one that adds or reduces a consistent amount of weight and drag (so less weight needed). And it came to me when I glanced at my fleet the other day.

The Estes Converter was an almost-ready-to-fly (ARTF) offered by the Big E from 2007 to 2009. It featured a plastic fin unit and 4 BT-56 body tube segments with screw type couplers, enabling the owner to vary the rocket's length from 24 to 40 inches. I am one of these owners, and the sight of it a few days ago got me wondering if one could design and build a TARC rocket that could reach the three altitude marks simply by screwing on different lengths of body tube. After pondering the matter for a couple of days, I decided to look into the concept further.

Estes Converter (Click to enlarge).

A shorter Converter
(Click to enlarge).

The first step was to determine if similar screw-type couplers could be had from the rocket vendors. Such things could probably be 3D printed, but I don't have easy access to this technology, so I need to be able to purchase them from somewhere. Fortunately eRockets offers them in various diameters, including BT-70. This obstacle now eliminated, I fired up Open Rocket and set to work.

eRocket's BT-70 screw type coupler (Click to enlarge).

I did not want to start from scratch, so I selected a TARC rocket I had built for the 2015 challenge, which was quite similar to this year's goal (1 egg to 800 feet). The Bullpup 1 is a 4 finned, BT-70 based cluster named after my Jr. High School mascot, and it was a simple matter to use this design to check out my modular hypothesis. I replaced the cluster configuration with a single 24 mm motor mount, shortened the main tube, and changed the number of fins from 4 to 3, taking care to scale them up to preserve the stability margin. Then I added the eRockets coupler at the top of the sustainer and inserted various lengths of body tube between it and the payload section, watching the effects on altitude.

The Bullpup 1(Click to enlarge).

What I found was that a 5 inch length of painted BT-70 added to the 11 inch sustainer body tube would send the rocket to 830 feet on an E12-6. Adding an 8 inch tube would drop the altitude to 804 feet, and an 11.5 inch tube would result in an apogee at  777 feet. So you could envision a "basic" Bullpup with an 11 inch main body and 3 tubes of 5, 8 and 11.5 inches, chosen according to the desired altitude. This set of simulations are, of course, highly idealized, as you generally need to aim 50-100 feet higher in the sims to compensate for rail friction, imperfect finish, and so forth. However, they do show the concept is viable, and I do think Open Rocket can be used to determine the short and long tube lengths once the medium tube length has been established by flight testing.

Open Rocket simulations in order of decreasing altitude (Click to enlarge).

I wonder if any team out there will use this approach or something similar? 

Tidbits from rocket history...

My friends are well aware I have two passions - rocketry and history. So I very much relish the times when I am able to combine the two, as I have done by perusing old rocketry magazines over the past couple of weeks. In so doing, I uncovered a few things I found to be of interest, which I thought I would share.

The first item is the earliest mention I can find of the existence of a rocket club in the Huntsville area. If anyone reading this knows of the old Madison Rocket Club or Mr. Hudson, please get in touch. I would love to talk with you!

Mention of a Madison Rocket Club in the August 1970 issue of Model
Rocketry. You would think they could spell Alabama right
(Click to enlarge).

Lots of clubs struggle with finding or holding on to a flying field - HARA included. This club note from 1968 shows that the rocketeers over in Dalton, Georgia figured out a way around this issue.

From Centuri's American Rocketeer, Vol. 3, No. 1 (1968 -
Click to enlarge).

There is no way that a club could do this today!

The 3rd item is one of the NAR songs published in some issues of Model Rocketry - the claim is that they were sung at contests such as NARAM. Composed well before the advent of high power and the legal wrangling with the federal government (BATFE), this song highlights the battles to allow model rockets with fire departments all over the nation.

NAR song from the June 1969 issue of Model Rocketry (Click to enlarge).

I am posting this little club note from the November 1970 issue of Model Rocketry because I think this would be an AWESOME name for a TARC team:

(Click to enlarge).

Trip Barber is one of the pillars of our hobby - past president of the National Association of Rocketry, and the driving force behind TARC. However, I did not know that he also possessed the power to make it rain. Check out this short piece from the letters section of the November 1969 issue of Model Rocketry...

(Click to enlarge).

Is it wrong of me to want to try this, which is easily repeated with today's technology?

It's Enerjet time!

I have made good progress on my backlog of rockets - the Mini X and Zeta are finished, Ool (My 2nd Geezer TARC rocket) has its 2nd coat of primer, and the Boyce Aerospace Redstone missile has another section of its 3D printed fin can sanded. It's time for a new project, but I have a slight problem - I'm out of sanding sealer, and Brodak, my supplier, is also temporarily out of stock. This kinda puts the kibosh on any rockets with balsa, as my results with skinning fins with paper vary significantly in quality and Fill N' Finish doesn't harden the balsa. This leaves me stuck with kits having plastic fins and nose cones, and most of these do not excite my interest. So what to do, what to do?

Once again the Internet came to the rescue...

I was watching the YouTube video of the manufacturer's forum at NARAM-61; NAR has two of these, one at NARCON in late winter and at NARAM in late summer, and they are a great source of information on what the various rocket vendors are planning in the way of upcoming releases. At NARAM, Aerotech announced that they are rebranding all their mid-range motors (E, F, G impulse) under a new label, one with a very venerable and honored name - Enerjet. For those of you unfamiliar with rocketry history, the Enerjet line was Centuri's attempt to commercialize sport rocketry in the early 70's, featuring some kickass E and F motors and kits. Never successful, the line was given up for dead in 1974, with the motors and kits sold off in a catalog yard sale. Even when gone, Enerjets were a legend held in awe by rocketeers like me, and the big boys of rocketry continued to fly them throughout that decade. I only dreamed of owning Enerjet motors and a kit, as the cost was way beyond my allowance and the altitudes (thousands of feet) were way too high for any fields to which I had access. However, I now have more money and access to the club flying field, so it is time for me to realize another of my teenage aspirations.

Enerjet 1340 Sounding Rocket ad and brochure. The prototype in the photo uses the Nike Ram nose cone,
not the longer 6.4" ogive used in the production kits  (Click to enlarge).

The easiest of the Enerjet kits to build was the 1340 Sounding Rocket, featuring a plastic fin can and nose cone (and hence, no need for sanding sealer). This sounded like a good place to start, and a glance at the online plans showed I had all the parts in stock. Even though Enerjets went away in the 1970's, the plastic fin can and nose cone used in the 1340 and 1340/20 sounding rocket kits survived the decades, being reused in the Centuri Argus, the two stage Estes Longshot, and the Estes Eliminator - I'm sure there were others, but my memory is not what it used to be. All of these kits are out of production, but the Eliminator just stopped being produced, so you can still buy one at AC Supply or eBay. So I yanked an Eliminator kit out of my stash and removed the nose cone and fin can, putting the remaining kit components in my parts bins. The other pieces for the 1340 are readily available - a 13" length of ST-13 body tube (Estes BT-56, which also is no longer produced), an 8" length of ST-13 for the payload section, a coupler, and a 5" length of 29mm motor tube (also known as LT-115 or BT-52). The original kit used a plastic coupler with a 0.1" ridge, but I substituted a balsa coupler and glued a 0.1" piece of body tube in its middle to simulate the ridge. I also used the thick-walled LT-125 for the 13" lower section, as the 29mm motor tube smoothly slides into it without the need for centering rings or even tape.

Estes Eliminator kit (Click to enlarge).

Parts for my 1340 clone (Click to enlarge).

The nose cone would not fit into the LT-125 tube, so I was stuck with ST-13 for the payload section, which meant that the BC-125 balsa coupler would be a bit too small in diameter for the ST-13 tube. I fixed this by gluing an HTC-13 cardboard coupler onto the top of the balsa coupler. It slid smoothly over the balsa piece and snugly into the ST-13, so the inner tube diameter mismatch problem was solved. I then filled all body tube spirals with Fill N' Finish, sanded and washed the plastic parts, and shot all external surfaces with a coat of Krylon gray primer. After this dries, I will spray on white primer, followed by a base coat of white. The fin can and motor mount will be glued on last, after the painting is done - easier that way.

1340 styles and paint schemes - models and photo by Bob Sanford (Click to enlarge).

The only problem is the decor. The standard grey, gold, and white doesn't strike me as being very visible (light rockets powered by F motors get way up there), and the red, white and blue scheme is too conventional. I'll have to ponder this as the build progresses. In the meantime, I shall look forward to this rocket's first flight on one of the new Aerotech E motors with the spiffy Enerjet label!

A summer cornucopia of new releases...

The rocket vendors have not been idle over the past couple of months; there have been lots of new kit releases, so many that it has been difficult to keep up. I thought that I'd use this post to list some of them, illustrating how the build pile has grown.

First, we have a couple from Semroc - the Jupiter B, a saucer kit based on the Jupiter 2 from the old Lost and Space TV series, and a bring-back of the Estes Andromeda. A high school friend of mine had an Andromeda, and I have always admired its futuristic looks. A bit fragile though - the long, thin BT-20 body was easily bent and my friend was repairing the model almost every time it flew. The Semroc kit has the thicker wall ST-7 tubes, so I'm hoping it holds up better to flight stresses. It also features laser-cut jigs to help position and hold the fins during gluing - a nice addition!

The Semroc Andromeda and Jupiter B (Click to enlarge).

The next four are from a rocket company that deserves more attention. Custom Rocket Company has been around for just over three decades, releasing nice looking, good quality kits - perhaps their best known is the 3 motor powered Landviper, which was popular back in the 90's. I have acquired four from their 2019 line - the colorful Cubix, the dangerously-named Drone Killer, the Orbit payloader, and the Spin Thing, which has spin tabs at the rear of its balsa fins. The only downside of the Custom kits is that they have peel and stick stickers instead of waterslide decals. I usually scan and copy them on decal paper for use in my builds - makes for a nicer looking model.

Recently purchased Custom rockets (Click to enlarge).

Finally, we come to the recent releases from the "Big E" - Estes Industries. There are quite a few of these, so let's start with the five advertised in the catalog - the Double Ringer, the Sasha, the Boosted Bertha, the Gryphon, and the re-release of the Black Brant II. The Double Ringer has already been discussed, so I'll move on to the Sasha, which is a two stage 24 mm powered "look alike" of a Russian SAM missile. It's quite a looker, and features through the wall fins on the booster. The Boosted Bertha is Estes realization of that which has been done many times since the late 60's - converting a Big Bertha into a 2 stager. Like the Sasha, the Boosted Bertha has through the wall booster fins and I particularly like the orange paint decor. The Gryphon is a sleek, 13 mm powered glider similar to kits that used to be offered by the now-defunct Edmonds Aerospace, and the Black Brant II is a bring back of the 1986 scale kit, updated with laser cut fins. A very nice quintet!

New Estes catalog releases (Click to enlarge).

The return of the Black Brant II (Click to enlarge).

There is a rumor that Hobby Lobby threatened to drop Estes rockets from its store unless the company did something special for them. I don't know the truth of this, but I do know that Hobby Lobby stores now have 8 Estes kits, found nowhere else. These are:

• The Luna Bug - a very small (2.5") 13 mm rocket a la the Mosquito. Given the tiny size of this model, I guarantee I will not be painting it green as in the kit art. This will only create a high chance of losing it in the grass/weeds in addition to the likelihood of losing it in flight. I will be very surprised if I find this one after its maiden voyage.

• The Solo - A blue-and-yellow ARTF (Almost Ready To Fly) featuring a single cylindrical glider. The C6-3 is the only recommended motor. Have already built this one.

Luna Bug and Solo (Click to enlarge).

• The Tigres, a nice looking 18 mm powered ARTF. This one is likely to please young kiddos, and it went together in less than 30 minutes.

• The Long Ranger - my least favorite of the new releases, this one is a rather plain, long 18 mm rocket. The only catchy thing about it is the name.

• The Epic II is simply an Estes Sterling Silver with a different paint decor and name. This one is not an ARTF, but a standard build with balsa fins, etc.

• The ARTF Cadet is also a kid pleaser with its cool decor and use of 18mm motors. It's also a Bill-pleaser, as I really like the looks, despite the peel and stick markings.

Tigres, Long Ranger, Epic II, and Cadet (Click to enlarge).

• The ESAM-58 is a 24 mm powered single stage version of the Sasha, redone in a Canadian/British decor.

And finally:

• The Cherokee-E - A longer version of the hallowed Estes Cherokee-D of yore. Like its shorter cousin, this rocket is also powered by 24 mm motors, and I bet it really gets up there on an E12. Duane - who is a Cherokee aficionado - could not wait to get his hands on one of these.

Cherokee-E and ESAM-58 (Click to enlarge).

And those are the new adds to the build pile. As you can see, I have lots of work ahead of me.

New fleet additions...

The Mini-X and Zeta (Click to enlarge).

My recent burst of rocket building mania has resulted in a few additions to the fleet. The first two of these are the builds I started way back in December, the Zeta and the Mini-X. These rockets are from old 1960's Estes rocket plans, and they came out looking A-OK. I must say that I enjoy building these retro birds - takes me back to my childhood. The Zeta flew last Saturday on an A8-3; the Mini-X will probably fly at my next launch, whenever that is.

Oeuf proudly showing off (Click to enlarge).

Next to be completed is my first entry for this year's Geezer TARC - Oeuf. She's looking all sleek and sporty in her yellow and white decor.

I also threw together one of the new Estes releases during a stormy evening a couple of weeks ago. The Double Ringer is a bit of an odd duck, featuring two cylindrical gliders that more or less glide. It too flew last Saturday and performed well on a C6-3. I wish I could say the same for Allen's Double Ringer, which was powered by a Q-Jet D16-4; the gliders did not even remotely glide, fluttering to the ground like heavy feathers. My guess is that the cylindrical gliders may be very sensitive to their weight distribution, and that a slight deviance from the instructions can make the difference between gliding or not. At least that's my current hypothesis - gliders are not my strongest suit.

Estes Double Ringer (from catalog -
Click to enlarge).

My Double Ringer blasts off
(Click to enlarge).

The last add to the fleet is an Estes bring-back of an oldie - the Phantom. This model is a teaching tool, with a transparent structure so that folks can see the various parts of a model rocket. It was never intended to fly, even though the occasional doofus might attempt it, with the predictable result of a smoke and soot filled mess. My Phantom went together in about 30 minutes using some medium CA, and it currently resides on one of my rocket shelves, awaiting its chance to help teach the young.

Estes Phantom (Click to enlarge).

I currently am working on finishing my second Geezer TARC rocket, Ool, and a 1/34th scale Redstone missile made from 3D printed Boyce Aerospace parts. I will also throw together some more of the Estes new releases.

More on those in a later post.

The launch before the storms...

Rocketeers awaiting their chance to fly at Saturday's launch (Click to enlarge).

During the HARA club meeting Thursday night, Allen announced that he and a few others would gather at Pegasus Field East today for some rocket flying - at 8:30 AM! My initial reaction was "ain't no way I'm getting up early on a Saturday", but by dinner time on Friday I had changed my mind. The lure of flying a few rockets was just too strong, and besides, the day would be cooler in the morning. So I linked up with Duane just before 8:30 and we trundled off down the road. Only Martin was there when we arrived at the field, but the three of us were enough to get the canopy, table, chairs and pads set up. Allen showed up next, followed by Collin and his daughter and Josh and his dad, Dean. A few other folks who were going to fly some Estes birds of their own also arrived on the field, and we were able to assimilate them into our launch with ease. Rounding out the party was Julian and his family, along with Blake - a bit bigger crowd than normal, but that only added to the day's fun.

Collin and his daughter prep their rockets (Click to enlarge).

Flying got started around 8:45 with the launch of  my MPC Icarus clone. Powered by an A8-3, it had the questionable Micropeak altimeter tucked into its payload bay, as I was determined to see whether that device was truly wonky or if the exposure to direct sunlight on the previous two flights was the culprit behind the funky readings. The Icarus performed flawlessly, deploying the parachute near apogee and making a soft landing in the grass; I am also happy to report that the Micropeak worked exactly as it should, reporting a peak altitude of 221 feet. It seems to work fine if the device is fully enclosed.

My Icarus starts the launch (Click to enlarge).

Altimeter data from the Icarus Micropeak (Click to enlarge).

The rockets flew fast and furious for about 3 hours - so fast that I could not keep up, failing to record a few of the launches due to too many things going on at the same time. I only know the motors used in a few flights besides my own, so I'm going to hit the highlights of the day (in my opinion, of course) in this post.

The A8-3 in my Zeta ignites (Click to enlarge).

The Photon Probe gets going (Click to enlarge).

In addition to the Icarus, I sent my newly built Zeta on a picture-perfect flight with an A8-3. It was followed by my Estes Double Ringer; the C6-3 got it up to a decent altitude, where it deployed the cylindrical gliders. Unlike Allen's - who flew his Double Ringer on a D16-4 - my gliders actually glided, with one making a shallow swoop to the very edge of the field. Unfortunately, I botched turning on the keychain camera strapped to the side, so no video - I was really hoping to get a few frames of glider separation. Switching next to something a bit simpler, I loaded my clone of the Centuri Stellar Photon Probe on the pad, and it also performed well on a B6-4. The rocket landed not far from the canopy, coming down slowly under an 18" plastic Estes parachute.

Ignition of the Double Ringer's C6-3 (Click to enlarge).

The Double Ringer's gliders way up there
(Click to enlarge).

Inspired by Duane's multiple altimeter checkout by putting all of them in the same rocket, I did the same with my last flight of the day by placing a Perfectflite Firefly and one of my Micropeak altimeters in the payload section of my Probe-18 rocket. The B6-4 pushed the model to just over 380 feet, and I was very gratified to see the agreement between the two altimeters.

The Probe-18 adds more scorching to my blast deflector
(Click to enlarge).

Probe-18 under parachute (Click to enlarge).

Comparison of the Probe-18 altimeters (Click to enlarge).

So much for my stuff - now on to the highlights. Josh's Estes Airshow was the first of these, with both gliders putting on a nice show.  Duane's School Rocket flew well on an Aerotech E15 and Allen launched his finless ducted rocket on a partly stable flight that started out well but ended up in some serious corkscrewing around the sky. Inspection of the recovered model showed why - a sizable fraction of the lower tube had burned away! One of Josh's rockets, "Please don't melt" also suffered a heat mishap - being entirely 3D printed, some of the lower section melted badly, despite the name.

Josh's Airshow clears the rod (Click to enlarge).

Airshow glider doing its thing (Click to enlarge).

Coming in for landing (Click to enlarge)!

Duane's School Rocket leaves the pad
(Click to enlarge).

Liftoff of Allen's ducted rocket (Clicked to enlarge).

Aftermath of the flight (Click to enlarge).

"Please don't melt" soars into the sky (Click to enlarge).

Josh holds the melted pieces (Click to enlarge).

Duane had loaded three altimeters into one of his Geezer TARC rockets, and they all agreed that the F32 propelled the model up to around 645 feet, give or take a few. This was good news, as a couple of these altimeters were ones the John Paul II TARC teams had labelled as bad. This flight seemed to indicate that the bad readings were from user handling rather than equipment malfunction. Allen then launched the most impressive flight of the day - his BMS School Rocket was loaded with a G127 Redline, and it put that puppy up to 2226 feet in a flash! Top speed was 434 mph and the electronics took 28 g's during the flight. Something tells me Bill Saidon at BMS never designed the rocket for such a beastly motor, but we are very glad Allen got the model back in one piece. It was by far the coolest flight of the day.

Duane's rocket lifts off with its cargo of altimeters
(Click to enlarge).

Allen's School Rocket under G127 power
(Click to enlarge)!

There were many other flights, mainly by Estes kits. Amazons, Crossfires, Lynxes, Cobras, and Nike-X's all took to the air multiple times, and I think Josh must have flown pretty much his entire fleet. We departed the field at noon, and Duane and I hit the local Arby's for some needed sustenance. I had just arrived back at the apartment when a series of thunderstorms broke loose, and I felt pleased that we had chosen to launch in the morning. Sometimes things work out in good ways - today was one of those times.

A Nike-X under power (Click to enlarge).

An Estes Amazon streaks towards the clouds
(Click to enlarge).