Enerjet 1340/20, Part 2

In building my Enerjet 1340/20 replica, I largely followed the original design as shown in Enerjet's 1340/20 Sounding Rocket flyer of the 1970s. For example, I installed a 29 mm motor mount but concurrently also constructed a dedicated, removable 24 mm adapter for use with this rocket. A small deviation was made with regard to the parachute material; instead of the original two 12" silk parachutes, I used a hexagonal Rogue Aerospace PP-45 (45 cm diameter) nylon parachute and chose a combined recovery of airframe and payload section.

The most significant difference to the original 1340/20 rocket is the launch lug. Enerjet had fitted the rocket with wire loops for guidance during launch. While this likely made sense aerodynamically, I always felt unsatisfied when looking at the iconic 1970s photos prominently showing the #13 plastic fin unit's integrally moulded launch lug left without any purpose on the front side of the rocket. This was a design decision I didn't quite comprehend. I thus modified the top section of the moulded launch lug to hold a plywood stand-off, on which I later glued the lower of two conventional launch lugs. This worked flawlessly and left the front aspect of the rocket pleasantly uncluttered.

Epoxy adhesive was used throughout the construction of the rocket.

Astron Alpha Recovery

The fourteen year old me holding my freshly recovered Estes Astron Alpha after the launch seen elsewhere on this blog. This particular model was an early-style Alpha, featuring balsa wood fins and nose cone.

As noted in the aforementioned earlier post, this rocket was likely a self-made clone, as evidenced by what seems to be a Centuri parachute. I built a number of Astron Alphas of all incarnations, both from official Estes kits and as self-made replicas. It soon became a tradition to initiate launches with an Alpha, in order to determine wind conditions before switching to larger models.

Photographed by Hans Hofer in northeast Switzerland, in July 1978.

Handbook Of Model Rocketry

Another quest that proved a slightly more challenging than anticipated was my aspiration to find those editions of G. Harry Stine's Handbook Of Model Rocketry that my enthusiastically completist mind perceived as still dreadfully missing.

I first purchased the Handbook in its fourth edition in 1976 or 1977, and the latest, seventh edition is still readily available at the time I am writing this. We were utterly excited - rightly so! - about the Handbook when we first received it, and I thus also purchased any subsequent editions throughout the years. But obtaining the earlier and therefore historically rather fascinating editions was near impossible from Switzerland before the advent of the internet. And, as I found out, it can at times be somewhat difficult even today.

While I eventually found a copy of the second edition in decent condition, it was due to the extremely generous efforts by American collector Steve Kristal that I was able to complete the long-coveted line-up of books by adding the first and third editions. Needless to say, I am deeply grateful for such kindness.

For somebody who has been fascinated by model rocketry for most of my life, this means a lot. G. Harry Stine's Handbooks are not mere collector's items to me; it is still quite fascinating to read them, and the information therein has aged quite well. These books are like a time machine to an era when model rocketry lived through a golden age.

The photo above thus shows all the editions in chronological order. Top row, from left: Handbook Of Model Rocketry, original edition, Follett Publishing Company, Chicago, 1965; second edition, Follett Publishing Company, Chicago, 1967; third edition, Follett Publishing Company, Chicago, 1970; my original copy of the fourth edition as purchased when I was a teenager, Follett Publishing Company, Chicago, 1976.

Bottom row, from left: fifth edition, Prentice Hall Press, New York, 1987; sixth edition, John Wiley & Sons, Inc., New York, 1994; seventh edition (with Bill Stine), John Wiley & Sons, Inc., New Jersey, 2004.

Enerjet 1340/20

In my posts on this blog, I frequently alluded to how mythical Enerjet and that company's products appeared to us teenagers in mid-1970s Switzerland. At the same time, it was often difficult for us to find sufficient and reliable information about developments in our field of interest. We had to rely on issues of Model Rocketeer magazine, sporadic glimpses offered in company periodicals such as the Rocket Times or Model Rocket News. Or we deducted as much as we could from photos and text published in G. Harry Stine's Handbook Of Model Rocketry or Centuri's Model Rocket Design Manual, among others.

Congruent with our increasing skill in building and flying model rockets, we coveted any possibility to accomplish more advanced concepts and obtain motors with increased power. In the second half of the 1970s, when we became increasingly immersed in rocketry, Enerjet no longer existed, and it is very doubtful if any of Enerjet's products ever even made it to Switzerland while the company traded. We eventually found some solace when it became possible to obtain Flight Systems' products through a distributor in Germany, and we duly moved up a notch, both in motor power and materials.

But one of the rockets that always exerted an iconic radiance on me was Enerjet's 1340/20 payload rocket, first seen by us on page 231 of the fourth edition of the Handbook Of Model Rocketry, in 1976. Although I knew next to nothing about this rocket at the time, it became one of those designs that has never ceased to fascinate me in the 41 years since.

After Enerjet's demise, parent company Centuri continued to offer a number of components that were part of some of the former's most notable rockets. Among them were the #13 plastic fin unit (prod. no. F-413L), used by Enerjet's 1340 and 1340/20 designs and later part of Centuri's Phoenix Bird and Argos "Kwik Kits". Or the transition section and nose cone of the payload section of Enerjet's 1340/20, later offered in the guise of an egg capsule (prod. no. PNC-13E/ST-202), for example in Centuri's Rocket Times in fall of 1975 (a supplement to Centuri catalogue no. 761). And following the merger of Centuri and Estes, these parts occasionally reappeared as part of Estes kits, such as the Eliminator (the fin unit) or Eggspress (payload section).

Nonetheless, obtaining these parts to construct an Enerjet 1340/20 replica in the present day proved somewhat challenging, in spite of their sporadic availability and modern procurement tools such as the internet and eBay. Another surprise was the material used for the 1340/20's transition section and nose cone in their most recent guise as the egg capsule of the Eggspress. Instead of the more common, glueable high-impact styrene used for most nose cones, the plastic used for these parts is reminiscent of cheap garden toys for children, as usually imported from Asia, i.e., polyethylene. This flexible plastic is difficult to sand (and sanding is unavoidable due to the age of the original moulds), glue, and paint. I suppose this material was chosen due to its ability to absorb impacts without cracking.

The styrene plastic fin unit, on the other hand, appears to be entirely unchanged from the one I owned as part of my Centuri Phoenix Bird in 1978. The only difference is the colour in which it is moulded. As I was beginning to run low on original Enerjet waterslide decals, I had Wessex Transfers in Australia print me some replica decals.

Enerjet logo and Enerjet 1340/20 brochure sample page © by Enerjet Inc., Phoenix/AZ, USA.

Vehicle 76

The design of Vehicle 76, a sport model with payload section, is loosely based on the smaller Vehicle 9, previously covered here. Vehicle 76 was built in 1999, using various Vaughn Brothers, Estes, and Aerotech components. It utilizes plywood through-the-wall fins with a thickness of 2.3 mm. It measures 650 mm in length and 66 mm in diameter and is intended to be flown with 29 mm F and G composite motors.

The nose cone, 205 mm in length, conceals a tubular payload section with a length of 180 mm and a diameter of 42 mm. At the time, it was tailored to the altimeter I used most often, the Missile Works RRC2. The payload section is fully removable, for ease of altimeter access. The rocket is recovered by means of two silk parachutes.

Top photo shows Vehicle 76 in Zurich, Switzerland, in 2016. Lower photo was taken in Thalwil, Switzerland, after completion of the rocket in summer of 1999.

Vehicle 22 Redux

The evolved version of the original Vehicle 22 payload model rocket, Vehicle 22 B, while being prepared for launch from my metal theodolite launcher at Allmend Frauenfeld, Switzerland, on Saturday, April 26, 1986.

Vehicle 22 B flew with a Flight Systems Inc. 21 mm black powder D or E motor. And while my flight data sheet of that day indicates a very good deployment of the parachute and a perfect post-flight condition of the rocket, the flight itself is described by means of a brief, wry remark: "stability deficiencies".

Photography by Martin Kyburz.

Cox Model Rocket Ad, December 1972

Cox "Now: Two more ready-to-launch rockets" ad, featured in Model Rocketeer magazine, vol. XIV, no. 11, December 1972, published by the National Association Of Rocketry, McLean, Virginia, USA.

Shown are Cox' legendary X-15 plastic model rocket, recovered by parachute, and the elegant Space Shuttle America, whose booster section was recovered by parachute while the two "shuttles" glided back to the ground.

Cox ad © by Model Rocketeer, McLean, Virginia & L.M. Cox Mfg. Co., Inc., Santa Ana, California, USA, 1972.

N Project: 4" Glass Fibre/Carbon Fibre Rocket, Part 3

Top photo: Professor Eugene Trubowitz is examining one of the fresh arrived Rocketman parachutes at the machine shop of the Swiss Federal Institute of Technology in Zurich, Switzerland, in late summer of 2000. All three rockets of the N project used Rocketman main und drogue parachutes.

Second photo from top: the two custom threaded forward closures of the Dr. Rocket 98 mm aluminium motor cases used for the two 4" rockets of the project. We were very fortunate to be granted to use the tool machines of the Institute for any such special modifications required in the course of our project.

Lower two photos: first trail assembly of the electronics compartment for the 4" glass fibre/carbon fibre rocket. The design of the electronics compartments for both 4" rockets was identical. The mounting base for the electronics thus consisted of an aluminium ring/shoulder, screwed to the modified forward closure. This arrangement further provided a mounting point for the glass upper airframe section.

The circular white insulation foam disc was intended to shield the electronics from the head emitted by the subjacent N2000 composite motor. Again, four threaded steel rods served to hold four custom- made aluminium mounting bridges, to which the two BlackSky AltAcc dual deployment recording accelerometers would subsequently be attached.

N Project: 4" Glass Fibre/Carbon Fibre Rocket, Part 2

Further images depicting the construction of the 4" glass fibre/carbon fibre N-motor rocket built for the BALLS 10 experimental launch held at Black Rock Desert in Nevada, in 2000. Top photo shows the custom made carbon fibre 4" nose cone with glass shoulder and steel tip. This beautifully immaculate cone was manufactured by Swiss Composite, based on calculations by Professor Eugene Trubowitz.

Centre photo shows Professor Trubowitz working on the rocket while we were performing a first trial assembly of the full (but still incomplete and unpainted) vehicle at the machine shop of the Swiss Federal Institute of Technology in Zurich, Switzerland. Components of the other two rockets of the N project can be seen to the right: the red and silver 4" aluminium/glass fibre/carbon fibre rocket with its welded aluminium fins and, at lower right, a section of the carbon fibre fin can of the 6" glass fibre/carbon fibre rocket.

Lower photo shows the 4" glass fibre/carbon fibre N-motor rocket erected vertically for the first time, in mid-September of 2000. The red Dr. Rocket N2000 98 mm aluminium motor case can be faintly seen through the lower glass fibre airframe section. The steel tip of the nose cone is provisionally held in place by masking tape; it would later be secured internally by means of threaded steel rod.

Vehicle 79 (Redux)

Vehicle 79 Dominator III ranks among my favourite rockets in my fleet. It is an uncomplicated rocket to fly, and its simple design provides a consistently impressive performance on F and G composite motors. Vehicle 79 was constructed from a variety of US Rockets and Aerotech components, featuring through-the-wall plywood fins, a custom-made aluminium baffle unit, and a payload section with a length of 315 mm. Top photo was taken at my former workshop in Thalwil, Switzerland, on November 22, 2010.

Lower photo shows Vehicle 79 on a friend's aluminium launch pad, on the occasion of our "last launch of the century", held on December 22, 1999, in northeast Switzerland. We flew our rockets from 2 to 5:30 pm; the temperature fluctuated around the freezing point. This was our seventh flight that day and thus our last flight of the launch and of the century. Vehicle 79 was powered by an Aerotech 29mm F20-7W Econojet motor. The payload flown consisted of a Missile Works RRC2 altimeter and a custom 9V piezo sonic locator. The flight was perfect and loud, and the RRC2 indicated an altitude of 1274 ft.

1972 Enerjet Catalogue

Sample pages from the unique and intriguing 1972 Enerjet advanced rocketry model products catalogue (no. 721).

As deeply curious and utterly determined teenagers building model rockets in remote (from a consumer point of view) Switzerland in the mid to late 1970s, we were continuously driven towards increasingly advanced rocket concepts and the quest for rocket motors more powerful than the commonly available A, B, C, and D-class motors. Mind you, it was far from granted to find even such "regular" motors in Switzerland at the time. Our ambitions were satisfied to some extent when a German distributor brought the product line of Flight Systems Inc. to our hemisphere and we were finally able to obtain their range of D, E, and F black powder motors.

In our minds, however, Enerjet represented the holy grail of advanced model rocketry, and it therefore served as the underlying inspiration for many of our own projects. This was of course long before readily available information by means of the internet, and even though Enerjet was no longer trading as an active company by that time, the company, for us, was thus an entity equally shrouded in mystery and emitting a limitless fascination. The few things we knew about Enerjet had been glanced from pictures in books (the Handbook Of Model Rocketry) and Centuri brochures, or from the remnants of Enerjet's existence as evident in Centuri's catalogues.

I would have given anything to own the 1972 Enerjet catalogue at the time (or to even be granted to have a brief look at it), but any such publications remained unobtainably elusive for us two rocket obsessed adolescents in Switzerland. Only much later in my life was I finally able to obtain a pristine original edition. The infinite waiting period mattered little; Enerjet's very existence and iconic designs still represent the same captivating inspiration to me to this very day.

The above excerpts from the 24-page catalogue show, for example, Enerjet's revolutionary "port burning" composite motors with glass fibre casing, or the fantastic (and operable) Nike Smoke semi scale rocket (vaguely similar to the Centuri kit) and Nike Ram high altitude payload rocket.

1972 Enerjet catalogue sample pages © by Enerjet Inc., Phoenix/AZ, USA, 1972, scanned from my personal copy of the catalogue.

[Entry amended October 31, 2016; with thanks to Chris Michielssen.]

N Project: 4" Glass Fibre/Carbon Fibre Rocket, Part 1

Construction of the 4" glass fibre/carbon fibre N-motor rocket, the final of three flight vehicle designs built by our team for the BALLS 10 experimental launch held at Black Rock Desert in Nevada, in 2000. All three rockets were designed by the project's initiator, Swiss Federal Institute of Technology Professor Eugene Trubowitz, who subsequently invited me to be a main partner in logistics, financing, construction, and launch.

Powered by an Aerotech N2000 motor held in a Dr. Rocket 98 mm aluminium N motor case, this 4" rocket was to comprise glass fibre lower and upper airframe sections, three carbon fibre fins, and a custom-made carbon fibre and steel nose cone. The rocket's design resulted in a length of 2336 mm and a diameter of 101 mm.

Top photo shows the very early stages of the rocket's construction at Professor Trubowitz' home, in July of 2000. The carbon fibre fins have been aligned and attached to the lower airframe section with epoxy adhesive.

The next step, undertaken at the machine shop of the Swiss Federal Institute of Technology in Zurich, involved preparing a mould for the manufacture of laminated fillet strips. Centre photo shows these laminated fillets after attachment to the fin/airframe joint, in August 2000. One such laminated, formed fillet can be seen bottom left.

Lower photo shows Professor Trubowitz inspecting the provisional placement of the custom-made aluminium rail guide stand-off. The unfinished rocket in the foreground is the 4" aluminium/glass fibre/carbon fibre N-motor vehicle previously detailed on this blog.

Vehicle 77 Redux

A clear personal favourite in my fleet, the Enerjet Nike Ram-inspired Vehicle 77, photographed in northeast Switzerland on July 30, 1999, on the occasion of a flight powered by a 24 mm Aerotech E28-7T RMS composite motor. This flight took place in the early afternoon of a beautifully clear day, with low winds, and a temperature of around 30 degrees Celsius.

Launched off an Aerotech Mantis pad, Vehicle 77 carried a 6 volt piezo sonic locator. The rocket flew fast, very stable, and out of sight, to a computed altitude of slightly over 800 meters. The parachute deployed perfectly, but the rocket's payload section and parachute became entangled in a barn drain pipe upon landing. The tallest member of our little launch group was just able to pull it free, but the piezo sonic locator was lost during the retrieval, and the plastic parachute was damaged. Vehicle 77 itself survived in perfect condition.

A few weeks later, I replaced damaged parachute (it had likely been the wrong choice for such a rocket at any rate) with a nylon parachute by Rogue Aerospace.

Rocket Fleet, 1989

Scans of two regrettably very deficient analog photos taken at my former home in Nürensdorf, Switzerland, in autumn of 1989, depicting part of what was then my rocket fleet as well as some designs under construction at the time.

Top photo shows, from left: Vehicle 59, built from Flight Systems and Centuri parts and designed to fly with Flight Systems E black powder motors. Vehicle 59 measured 886 mm in length (including a payload section of 456 mm length). The rocket in the center is my scratch-built Honest John semi scale model (still lacking any finer details), while the model on the right is Vehicle 51 B Enigma II, a development of the earlier Vehicle 39 A Enigma. Vehicle 51 B was constructed using Estes, Centuri, and CMR components and intended to be flown with Flight Systems E and F motors. It measured 896 mm in length and featured a payload section of 158 mm usable space. The lower and upper sections of the rocket were recovered by means of two separate parachutes.

Lower photo, from left: Vehicle 32, a cluster design utilizing three 18 mm motors and featuring a payload section. Next to it are Vehicle 23, a 24 mm experimental design with ultra thin, high aspect-ratio plywood fins, and Vehicle 22 B, also using three high aspect-ratio plywood fins that were strengthened with an epoxy coating. The rocket line-up is completed by Vehicle 48 A Heracles (designed for 21 mm and 24 mm D motors), Vehicle 39 A Enigma, and Vehicle 44 A Rhea (a sport model with payload section, built specifically for Flight Systems D18 motors).

Homage To Model Missiles, Inc.

I scratch-built this semi scale Aerojet-General Aerobee-Hi in 1986, using Centuri parts. It was an homage of sorts to the beginnings of our hobby and thus to some of the protagonists that had inspired me during my youth, ten years earlier: Orville H. Carlisle and G. Harry Stine.

As described, for example, in a fantastic article titled The First Model Rocket Kits, authored by G. Harry Stine and published on pages 5 to 9 of the February 1978 issue of Model Rocketeer magazine, Carlisle and Stine's Model Missiles, Inc. produced the Aerobee-Hi as the company's first proper model rocket kit in 1958. Moreover, I also admired the early Aerobee-Hi model rockets when I obtained what was my first copy of the Handbook Of Model Rocketry (Fourth Edition) in 1976 or 1977, such as in the formidable launch photo on page 125. We were model rocket obsessed teenagers at the time and not only glorified G. Harry Stine but also the beautifully pure design of the Aerobee-Hi rocket.

My own Aerobee-Hi was first launched on May 28, 1999, many years after I had originally completed it. The top photo shows the final preparations for this maiden flight, conducted with an Estes B6-4 motor in northeast Switzerland. As can be expected for such an immaculate design, it performed flawlessly. The lower two photos show the same rocket in May 2016, in Zurich, Switzerland.