There are two projects, in particular, that I have been working on over the past year that have kept me busy. Firstly, my Arrow* rocket. This rocket was designed with two goals in mind. To achieve supersonic velocity, and to reach an altitude of 2 km (6500 ft.) using a relatively small (<45mm) motor powered by one of my newer HTPB propellants. The Arrow rocket has a 51mm (2 inch) aluminum airframe and is designed with minimize drag in mind. This is accomplished, in part, by swept fins, Von Karman profile nosecone, polished airframe and fins, and fall-away launch guides.

The other project is an M-Class sugar motor. Designing and building this rocket motor, powered by KNSB, took about 4 months from start to finish. This is by far the largest rocket motor I have attempted to produce. I put everything I have learned over many years of EX work into the design and build process to help ensure a successful culmination of the sizeable effort involved. This motor, which I deemed Muon, is 89mm (3.5 in.) and is nearly a metre in length. Holding 6 kg (13 lbs) of propellant, the grain consists of six BATES segments. Prior to firing the full-size Muon, I decided it would be prudent to firstly test fire a two-segment grain version (Muon Short) that was essentially identical in design and construction except having shorter length casing. This motor was fired on Feb.23 and performed up to expectation. The full-size Muon was test fired a month later. It was a breathtaking sight, as the motor came to life and roared for nearly four seconds. The performance appeared to be nominal, although data collection failed due to a frozen laptop (literally, it was -9 deg.C. at the time). The Muon will be fired again later this year before the thermometer dips.

* The name was chosen to pay homage to the magnificent Avro CF-105 Arrow . An airplane that was, sadly, ahead of its time.

• Arrow aft end showing fins and boattail
  
• Arrow on launch pad prior to shake out flight
  
• Fall-away launch strap for Arrow 3-D printed of PLA plastic
  
• Muon-Short in STS-5000 test stand
  
• Muon nozzle (aluminum shell/graphite insert)
  
• Graphite throat insert for Muon nozzle
  
• Grain segments for Muon, each 1 kg. KNSB
  
• Curing propellant under pressure for 40 hours.
  
• Video of Muon static test firing (10 mbytes)
  
• Video of Muon static test firing, close-up (13 mbytes)
  

  Muon rocket motor firing

Earlier this year I accomplished the two key 50th anniversary events that I had planned. On February 26th, my A-rocket took to the sky after exactly 50 years of merited idleness with a beautiful flight nearly duplicating its earlier effort.

I also built and launched a zinc-sulphur powered rocket. Being a complete neophyte with regard to zinc-sulphur propellant, I based the design of the motor on Brinley's Alpha rocket. I scaled-down the motor and based my Alpha-minor on 1" EMT. The rocket itself was a full-scale replica with an all-aluminum airframe. It also featured many 3D printed components. The Alpha-minor motor was successfully static fired back in May. Prior to launching the Alpha rocket with the zinc-sulphur motor, I chose to christen Alpha with a flight utilizing a small APCP motor that I'd recently developed . This maiden flight of Alpha-1 took place in early June, a flawless flight. One week later, Alpha-2 with its zinc-sulphur motor was launched. The performance of the motor was disappointing, lofting Alpha to a tad over 400 feet (122m.). I had expected triple that. Reviewing the video of the liftoff, it appeared that the initial high acceleration resulted in much of the propellant being ejected from the nozzle (it was in packed powder form) before combusting. Perhaps some day I will try zinc-sulphur again. However, as a lesson learned, simply packing the zinc-sulphur into a motor does not appear to work well. Using a solvent (perhaps xylene) to partly bind the particles together may be the way to go.

I have made some progress with my Introduction to Experimental Rocket Design web pages. To date, it has been rather slow going, as I have been busy with APCP propellant development. The latter has been going well, and I have been converging on a "go to" AP composite propellant based on a well-suited epoxy binder. A J-class 38mm motor featuring this propellant recently lofted my Xi rocket to a recent-record of 4866 feet (1.48km). In the not-too-distant future, I expect to feature this APCP in a new web page.

• Alpha-minor zinc-sulphur motor for Alpha-1
  
• Author with Alpha-minor zinc-sulphur motor ready for static firing
  
• Chamber pressure graph for Alpha-minor, test fired May 7, 2022
  
• My grand-nephew with Alpha rocket prior to its first flight
  
• Video of flight of Alpha-1 rocket with APCP motor(25 mbytes)
  
• Video of liftoff of Alpha-2 rocket with Z-S motor(10 mbytes)
  
• Video of static firing of J-class APM-E.6 APCP motor and Z-S Alpha-minor motor (19 mbytes)
  
• Static firing of Alpha-minor Z-S motor
  
• 38mm grain segments for J-class APM-E.6 APCP motor
  

Next year I will be celebrating 50 years since I began my amazing journey into the realm of amateur rocketry. I made my first amateur rocket flight on the 26th of February, 1972, launching my "A-1" rocket twice on that day. The first flight was a cautious one, with a "half-load" of potassium nitrate-sucrose propellant. It flew to around 50 feet altitude, not too impressive. For the second flight I threw caution to the wind and loaded a full charge of 50 grams of propellant. I still recall my exhilaration at seeing the rocket climb higher and higher, arcing over at an apogee estimated to be at least 500 feet. That made quite an impression on me at the time, and provided the impetus to pursue lofter goals. I still have my A-1 rocket. It needs a bit of repair, but I plan to launch it once again, sometime in 2022. Earlier this year, I static tested a replica of the "A-engine" (as I called it at the time, a carryover term from my earlier foray into model rocketry) that boosted the A-1 rocket. The motor is small, but packs a brief kick.

Another 50th anniversary project is to launch a zinc-sulphur rocket. The first two books I found that dealt with amateur rocketry were Brinley's Rocket Manual for Amateurs and C.L.Stong's The Amateur Scientist. Both featured rockets powered by this classic formulation. I had longed to built such a rocket back then, but never was able to obtain zinc dust. I recall trying to make my own zinc dust by filing down zinc cases of expired dry-cell batteries. Sulphur was readily found on the railway tracks behind our home. The resulting mixture tended to sputter with impressive blue, crackling flashes, but involved too much time and effort to make a decent quantity of the "dust". Besides, the discovery of "caramel candy" described by Brinley quickly drew my attention away from zinc-sulphur. As the zinc-sulphur rockets featured in these two books were the ones that initially inspired me, I feel that a worthwhile recognition would be to build and fly one in 2022, better late than never, as they say. Thanks to the miracle of Amazon and eBay, I had no problem finding zinc dust in 2021 !. Most likely, I will build a reduced scale version of Brinley's Alpha rocket. As the Alpha was a 15,000 foot rocket, a more manageable version would be a 1/3 scale version. My preliminary calculations estimate this 1/3 scale Alpha should achieve an apogee of around 3000 feet (900m.).

These anniversary projects will begin later in the year. At present, I have started working on a new set of web pages that detail the process of designing an amateur rocket. Planned topics include setting goals, nosecone and body design, sizing fins for stability, aerodynamics of amateur rockets, motor sizing, recovery, reliability, tracking and weight control. These pages will be based on personal experience and knowledge gained over the many years that I have been fortunate enough to partake in this most rewarding hobby. These rocket design web pages are intended as a long-term project that will take a while to complete. I will likely upload the pages on an "under construction" basis, starting in a month or two.

Incidently, 2022 is another anniversary, the 25th (quarter-century mark) of my Nakka-Rocketry website, which I started as a modest endeavour in 1997. Hard to believe that my website predates Google !

• Author with replica A-engine prior to static firing, April 2021.
  
• Chamber pressure graph for A-engine, test fired April 17, 2021
  
• Video of static firing of A-engine (10 mbytes)
  
• Video of static firing of A-engine (camera #2) (10 mbytes)
  
• Replica "A-engine" disassembled
  
• Grain casting for "A-engine"
  
• Replica "A-engine" with potassium nitrate-sucrose grain segments
  
• Brinley's Alpha rocket
  
• Photuris A and Photuris B zinc-sulphur rockets featured in The Amateur Scientist
  

Another year has flown by and there are a lot of new developments to write about.

My rocketry activities were concentrated on development and testing of higher performance propellants featuring potassium perchlorate and ammonium perchlorate as oxidizers. There was a lot of learning involved, as I had not before worked with these particularly potent oxidizers. Fortunately, my efforts paid off and I was able to conduct a number of successful launches using some new propellants.

Initially, the bulk of my efforts were geared toward an AP-silicone propellant. Silicone is attractive as a fuel & binder as it is readily available and preparation of a AP-silicone grain is simplicity in itself. Although the experience was basically successful, the resulting propellant had a very high burn rate and featured a rather high pressure exponent.

I put work on AP-silicone propellant aside, for the time being, to delve into a more traditional AP-HTPB propellant. I figured it was a good idea to start off with a more tried-and-true approach. My retired friend and fellow rocketry experimenter Harry Lawrence (who worked with AP-HTPB propellants during his professional career) provided me with a simple starter propellant, which he deemed APX. I had good success with this propellant, and after a number of static tests, launched my Xi-20 rocket with APX powered APM-D.1 experimental motor. This motor featured a new development for me -- an aluminum nozzle with a graphite insert. Aluminum is attractive, not only because it is lightweight, but because it is nicer to machine than steel.

On the footsteps of some false starts attempting to develop a KP-based propellant, I altered my course and instead tried a blended oxidizer approach. Employing potassium perchlorate together with potassium nitrate, a modified version of KNSB was successfully developed, a propellant which I deemed KNPSB. Several successful static test firings and a couple of launches followed.

Due to the rather fast burn rate of KNPSB, I then designed a novel 76mm motor that is short and fat, and is unique in the sense that it has fins mounted on it. The 76mm diameter, which matches the diameter of my Xi rocket, provides for a decent burn time.

This motor also features a new development -- an aluminum nozzle with steel throat insert. This motor was successfully static fired, followed by a launch, powering my Xi-21 rocket.

KNPSB propellant is featured on my newest web page.

One other AP-based experimental propellant that I had success with utilizes epoxy as a binder and iron powder as a thermic agent. In the process of experimenting with such formulations, I learned that many common epoxies are not compatible with AP. I was fortunate to find one particular brand of epoxy that was compatible, although it required curing under pressure to prevent the formation of microbubbles in the finished grain.

• Machining an aluminum nozzle for 76mm motor
  
• Aluminum nozzle with steel throat insert for 76mm motor
  
• Aluminum nozzle with steel throat insert for 76mm motor
  
• 76mm APM-G motor on stand (pressure only measured) for first test firing
  
• Aluminum nozzle (with graphite insert) for APCP motor
  
• Balls of AP-silicone propellant ready for packing into mould
  
• Machining a phenolic throat insert
  
• Aluminum nozzle with phenolic throat insert
  
• Thrust-pressure curve for 38mm AP-silicone motor test firing
  
• Thrust-pressure curve for 38mm APM-D.1 motor with APX propellant
  
• Static test firing of a 38mm AP-silicone grain
  
• Static test firing of a 38mm AP-epoxy-iron grain

It has been over a year since I last updated my Sneak Preview page. As such, it is clearly time to tell about the many yet-unpublished projects that have occupied my spare time over that duration. Most recently, I have gotten a 3D printer. I figured it would be handy to have, as many parts related to my rocketry hobby can potentially be made more readily using "additive manufacturing" technology, compared to conventional methods. I have seen parts made by other rocketeers and have been more than impressed. So I was itching to get one for myself. The printer I bought is a FLSUN Cube, which comes as a kit. It is quite large, with a 260x260mm bed and can print items 350mm tall. It took a while to assemble and even longer to work out the bugs, but just recently I successfully printed my first rocket part -- a nosecone to replace the existing one for my Xi rocket. It is fabricated of PLA plastic and weighs a third of the current nosecone which was machined out of a solid bar of delrin (which was a big job!). I subsquently printed a parachute piston and AvBay compartment. Other parts that I foresee being 3D printed in the near future are fins and avionics supports.

Wishing to further expand my rocketry horizons, last fall I began experimenting with AP (ammonium perchlorate) oxidizer and to a lesser extent KP (potassium perchlorate). Initially wanting to use a readily available binder, I began experimenting with silicone II. I was largely impressed with the results. Physically, the product blends well into a putty consistency perfect for packing into a mould. It cures effectively, taking about 2 weeks to mature into a nice rubber-like grain. I successfully static fired a number of motors using AP-Silicone II formulations. The burn rate was found to be very high. Although not necessarily a drawback, I have been investigating additives such as ammonium chloride in an attempt to tame the burn rate. Or alternatively, I might take advantage of the fast burn to design an end-burner motor. In the near future, I'll be experimenting with traditional APCP based on HTPB rubber. With regard to KP, I have found it to be a difficult beast to tame as a propellant oxidizer. This is not a great surprise as KP is known for its high pressure exponent and attendant problems. I have found that KP, when blended with other oxidizers, appears to behave in a more responsible manner. This is a promising approach that I have just begun to pursue.

One of the essential elements of propellant development is determination of burn rate parameters (burn rate coefficient, a and pressure exoponent, n). This is useful for two important reasons. One, to ascertain whether the pressure exponent is in the practical range for a propellant (best between 0.3 and 0.6). And secondly, quantifying the burn rate parameters for a particular propellant is necessary for designing a rocket motor. A convenient device for measuring burn rate parameters is a strand burner. I have constructed a few of these in the past which have worked well. One of the drawbacks is the expense of using nitrogen gas as a pressurizing agent. As such, I decided to try designing and building a self-pressurizing strand burner. It seemed to make good sense to harness the combustion gases of a burning propellant strand to develop the required pressure. Another advantage to this approach recognizes that pressure changes (increases) as the strand burns, so theoretically a single burn can provide burn rate over a range of pressure.

Venturing into another field of endeavour, I have recently flirted with nozzleless rockets. As the name implies, a nozzleless rocket is simply a rocket without a nozzle. Or more specifically, without a dedicated converging/diverging nozzle. The motor consists solely of a propellant grain cast into a casing, with a central core running the length of the grain. A bulkhead closes off the forward end. If such a motor is made sufficiently long, choked flow develops in the core. As such, the core serves as a sonic nozzle. After learning about the nozzleless development work of Serge Pipko and in particular the surprisingly decent performance of such motors, I couldn't resist trying nozzleless rockets for myself. I made a pair of 38mm motors, one KNSB based and the other KNDX. Each held just over 500 grams of propellant. Although the KNSB motor suffered an anomaly, ejecting the entire grain from the motor shortly after ignition, the KNDX motor performed well, burning for 2.5 seconds and producing a maximum thrust of 50 lbs. (220 N.). Subsequently this motor was successfully flown in my Xi rocket (Xi-9). Eventually I plan to delve into the theory of nozzleless flow to gain a better understanding of the physics behind it and to develop a rational basis for nozzleless motor design and performance prediction.

I've recently developed a new rocket motor for boosting the Xi rocket. My goal was to develop a motor with a slightly higher impulse and longer burn time than the workhorse Impulser. This new motor, deemed JEM, is a 51mm J-class motor powered by KNDX. JEM was first static fired on 4 January 2019. Following this successful test, the JEM motor boosted Xi-11 a little over a month later.

• My new 3D printer
  
• 3D printed parachute-piston for Xi rocket
  
• Measured thrust and pressure curve for nozzleless motor NTM-5
  
• Apparatus for casting JEM grains
  
• KNDX grains for JEM motor
  
• Two experimental AP-silicone composite motors
  
• Experimental AP-silicone composite motor on test stand
  
• Test firing of experimental AP-silicone composite motor
  
• Mixing a batch of AP-HTPB propellant
  
• Cast grains of AP-HTPB for an experimental 38mm motor
  
• Experimental self-pressurizing strand burner
  

Amongst other rocketry related endeavours that have kept me busy, I've recently worked on developing two new motors for my Xi rocket. One of these is a second stretch of my Impulser motor, which I've deemed Impulser-XX. This motor holds six grain segments of KNDX. This motor was successfully static test-fired on June 3rd. During the same outing, I test-fired my basic Impulser with KNSB. The purpose of this test was to assess certain design improvements such as grain inhibitor material and thermal liner that had an enhanced thermal protection coating. Also, an objective was to compare KNSB made with synthetic potassium nitrate (made from calcium nitrate) to that made with commercial-grade potassium nitrate (the Impulser-XX was likewise fueled by synthetic potassium nitrate). The results of these two tests demonstrated that synthetic oxidizer performed just as well. The enhanced thermal protection coating was also a success.

A third rocket motor, deemed SSJ-F was also fired -- a flight-version of a static-test motor that I'd developed and test-fired back in 2006-2007, the J-Class SSJ motor. This motor is slated to be flown in a future Xi flight. The test-firing of SSJ-F was less successful than the Impulser motor firings. A burn-through of the motor casing occurred shortly after achieving full thrust, leading to a partial rupture of the casing. Fortunately, no damage to the STS-5000 test stand or instumentation resulted, despite the violent event. Cause of the burn-through was, in hindsight, the result of a number of design flaws including deficiencies in the thermal protection. Of significant note, the SSJ-F did not incorporate the improved thermal protection used experimentally on the earlier Impulser/Impulser-XX tests. The SSJ-F motor is currently being prepared for a follow-up test firing in the near future, with several design modifications being implemented.

This past Saturday turned out to be a momentous day for my rocketry journal. Five motors were successfully fired, with excellent data collected. The previously proven SSJ motor was fired twice, providing useful erosive-burning data. The firings also demonstrated the viability of KNSB propellant prepared by the Vacuum-Evaporation method (which will be documented in a future web page). Also confirmed was the viability of a new method of casting KNDX propellant directly within inhibitor sleeves.

The most exciting results came from the firings of my new motors powered by an experimental ammonium nitrate (AN) and aluminum (AL) propellant. Out of the five motors (see photo, top left), two failed to ignite. However, the other three ignited and burned rather well (photo, middle left), generating decent chamber pressure. The measured pressure was used to compute characteristic velocity (c-star) for the propellant, which was determined to be 4204 feet/sec (1281 m/sec). Not bad, for a first try. This roughly relates to an Isp of about 200 seconds, which should improve at higher chamber pressure. A lot more experimentation is needed before a practical propellant comes out of the effort, but this is an encouraging step.

Besides the novel propellant composition, the AN-AL motors were my first motors to utilize snap-rings for nozzle retention. Utilizing neoprene as a binder, the hollow-cylindrical propellant grain was formed by a hydraulic ramming technique in a case-bonded configuration. Complete details on these motors and propellant is slated to be featured in a future web page.

In the photo at left, I am holding my newest creation, a "J" class rocket motor that will be used primarily for studying erosive burning of sugar propellants (as described in the November 5th update). The cause of the odd "triangular" thrust profiles seen in many test results of KNSB (sorbitol propellant) will be also be investigated. The most recent hypothesis suggests that inadequate segment spacing may be responsible.

The photo below illustrates three batches of six segments of KNSB propellant for this motor. The first three static tests will determine the effects of core size and of segment spacing.

As well, I am continuing to gather data and test results on the influence of the potassium nitrate grade on propellant performance and burning characteristics.