Author with Arrow rocket ![]() Arrow taking to the sky ![]() Author with Muon rocket motor | April 19, 2024 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.
|
![]() Alpha-2 liftoff, powered by zinc-sulphur ![]() Alpha-2 rocket ![]() Zinc-Sulphur motor static firing | August 25, 2022 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.
|
![]() Author with A-1 Rocket, 1972 ![]() Author with A-1 rocket, 2021 ![]() A-Engine static firing | September 13, 2021 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 !
|
![]() An APCP motor displaying mach diamonds ![]() Ammonium Perchlorate/HTPB grain segments ![]() APM-D.1 rocket motor APM-G 76mm finned rocket motor | December 17, 2020 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.
|
3D printed nosecone for Xi rocket ![]() NTM-5 nozzleless rocket motor firing JEM rocket motor | July 17, 2019 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.
|
![]() Static firing of the Impulser-XX | June 27, 2018 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. |
![]() Some of the Xi rocket components | September 5, 2017 Over the past few months, I have been designing and building my newest rocket. Deemed "Xi", this rocket incorporates lessons learned from my experience with the Zeta and DS rockets that I have built and flown regularly over the past three years. Similar to the Zeta, the Xi rocket is fabricated largely of lightweight aluminum, has a Delrin nosecone, and features the "Avbay" concept of the DS rocket that I favoured. The Xi rocket will incorporate an improved on-board aft-facing video camera and a smoke tracking charge. An "Egg Timer" altimeter will be added to provide backup for parachute deployment. To allow for greater payload volume, the Xi diameter has been increased to 3 inches (76mm), although the aft section housing the motor retains the 2.5 inch diameter (63.5mm) of the Zeta. The Impulser-X motor will be used for initial flights. An 8-grain segment version of the Helios motor, termed the Helios-XX has been designed and following static verification testing, will likewise power the Xi.
Graphics
|
![]() 76 mm KNSB grain with star core ![]() Setup for test firing | Jan.8, 2011 A rocket motor was recently designed and built in order to assess a new grain geometry -- one with a star shaped central core. This particular shaped star, with seven points, produces a relatively neutral burn, at least in theory. There are a number of advantages to this grain configuration. One of the most significant is that all burning takes place in the core. This means that the propellant itself serves to insulate the motor casing from the intense heat of combustion. The propellant used for this test was conventional sorbitol based KNSB, however, surfactant was added to allow for better casting around the complex geometry of the mandrel. The mandrel was machined from aluminum, and consisted of a central 7-sided rod and seven triangular "fins". Removal of the mandrel was simple, with the rod being extracted first, followed by each of the seven fins. Being intended only for static testing, the motor had a simple design. A heavy steel nozzle and bulkhead were used, requiring a minimum machining effort. The casing, however, was fibreglass composite. This choice was made to help assess how well the propellant served to insulate the casing. The rocket motor was test fired on December 4th, 2010. The firing was fully successful and a good graph was obtained of both chamber pressure and thrust. The thrust curve was somewhat progressive, however, this was attributed to casting flaws in the grain which resulted from some trapped air during casting. A repeat test will be conducted in the near future using an improved casting method which is expected to resolve this issue. |
![]() Four A-100M grains ![]() Firing of A24-C1 motor | Oct.2, 2010 Since the last update in April, I've been fortunate enough to have the chance to head out to the test range a couple of times to do some rocket motor testing. In May, I static fired the A-100M motor five times, including testing KNSB and KNDX propellants with and without a surfactant. Surfactant was added to the propellant during casting in order to reduce the viscosity of the slurry. Scott Jolley developed this remarkable technique, which worked very well and made the propellant pourable (watch the video). The surfactant that I used was foaming bath gel with sodium laureth sulfate as the primary active ingredient. There was a small reduction in delivered Isp (from 116 sec. to 112 sec.), but overall the performance was very comparable, with a somewhat extended burn duration of the KNSB treated with surfactant. Grain density was not adversely affected by the addition of surfactant. A propellant grain was also cast using xylitol sugar (KNXY), and test fired. The KNXY grain, which seemed to be non-hygroscopic, performed well in the test firing.
|
Two other motors were static tested. One was the new J-class motor powered by a half-kilogram of A24 composite propellant based on ammonium nitrate, aluminum and neoprene. This motor, deemed A24-C1, is a scaled-up version of the A24-B motor successfully developed earlier. This motor proved difficult to ignite, mainly due (in hindsight) to undersized igniters. After a number of attempts, the motor did successfully fire after a delayed start-up, and performed in a most impressive manner. The total delivered impulse was indeed mid J-class (977 N-sec) and would have been even higher if the start-up was cleaner. The characteristic velocity (c-star), which is a key measure of propellant merit, was a satisfying 1350 metres/sec. This compares to about 850 metres/sec typically obtained for sugar propellant.
The last motor tested had a KNSB grain with a pseudo-finocyl configuration. The primary goal of the test was to see if the pressure curve matched the theoretical Kn curve. It was found to match quite well. In the near future, I plan to test fire a grain with a 7-pointed star configuration, which theoretically produces a much more neutral burn.
![]() New experimental J-class motor ![]() | Apr.13, 2010 On March 20th, I gave a presentation at the University at Buffalo (New York state) on Experimental Rocketry and also on the Sugar Shot to Space program. This presentation was in support of the North East Conference of Space 2010. I was kindly invited by
the Students for the Exploration and Development of Space (UB-SEDS), which is a student run international organization that works to promote the exploration and development of space. I had a great time and the presentation was well received.
|
Whenever I visit a new supermarket, I always have my eyes open for mislabeled rocketry supplies. I recently discovered two such products, both interesting sweeteners. One is Xylitol and the other is a product called Stevia. I plan to attempt casting propellant grains for my A-100M motor and perform test firings if the casting is successful.
I have also been working diligently on updating and finally completing the web pages on RNX propellant. Last fall I test fired my RNX-BM motor which provided useful characterization data that will prove useful for designing RNX powered motors.
![]() RNX-BM5 results ![]() RNX-BM6 results | Nov.14, 2009 The RNX-BM "characterization" testing was recently concluded, with two good motor firings on Nov.7. The motor had been modified to hold a larger propellant charge, in order to obtain burn rate data at higher Kn values. The first static firing (RNX-BM5) was with RNX-71V propellant, and the second firing was with a charge of RNX-57 propellant. As is seen in the graphs, the progressive burning grains (hollow cylindrical) displayed the expected strongly progressive pressure and thrust curves. An interesting feature of the RNX-71V propellant is the slow initial pressure rise, which is a consequence of the rather high pressure exponent (n) that characterizes the burn rate at low pressure. Once chamber pressure reaches a certain value, the pressure exponent drops, which results in a sudden ramp-up of pressure. |
![]() Test firing of RNX-BM motor | Sept.27, 2009 The RNX-BM "characterization" rocket motor was test fired 3 times on Aug.19th. Three different propellants were used, RNX-71V, RNX-73 and the new formulation RNX-75V. The new formulation is similar to RNX-71V except that an extra-slow hardener was used with the West System epoxy that comprised the fuel/binder. Good thrust and chamber pressure data was obtained which was used to determine burn rate parameters, specific impulse and characteristic velocity (c-star). Kn (Klemmung) values for these tests ranged from 425 to 800, which is on the low side for slow-burning RNX propellant. As such, chamber pressures were relatively low. |
![]() Experimental ANCP grains pressed into metal tubes (-17 & -14A formulations) ![]() Nozzle for AIR 64 mm motor | February 10, 2009 Following successful development of an aluminized AN based propellant (see Experiments with Ammonium Nitrate / Aluminum based Propellant Formulations ), I decided to take on what may be an even greater challenge - to develop a non-metalized AN based propellant, using only commonly available materials. The photo shows two of the formulations, pressed into small grains, for open-air burn tests. Both of these particular formulations burned in a stable manner, as can be seen in the videoclips. The ANCP-14A formulation is based on AN, neoprene binder, with sodium chloride and charcoal burn rate enhancers. The ANCP-17 formulation is similar, but uses polyurethane binder, with sodium chloride and copper oxide to enhance combustion. The photo at left shows a nozzle that I recently machined. This is for a 9-grain, 64 mm motor that will use KNER (erythritol based sugar propellant) that is being designed and built by the Icelandic rocketry group AIR, and is slated to be flown in May in a new rocket (click for specs). |
![]() Remainder of self-extinquished propellant (1 of 4 segments) | June 1, 2008 Recently I had the opportunity to test fire two of my new 38 mm motors with experimental AN-AL (ammonium nitrate - aluminum) propellants (see Dec.2/07 posting), in addition to firing a number of other motor, including one for characterizing RNX propellant. One of the two AN-AL motors performed particularly well, with rapid start-up, a good clean flame, and excellent performance. |
![]() U. of Reykjavik presentation (with students' rocket) ![]() Media scrum at the launch site ![]() Raising the rocket into launch position | May 10, 2008 I was recently extended an invitation to do a presentation at the University of Reykjavik in Iceland, on the topic of amateur rocketry and to give an overview of the Sugar Shot to Space Program. The presentations were well-attended and enthusiastically received. Amateur rocketry is quite new to Iceland and the activities of rocketry groups, such as AIR, have been wholeheartedly embraced by the public. In addition to giving the presentations, a highlight of the visit was attending the launching of a scratch-built rocket by the students of the School of Science and Engineering. The rocket, powered by erythritol sugar propellant, was the culmination of a rocketry design course taught in collaboration with AIR. Despite a strong wind, the rocket was successfully flown to an apogee of 1.5 km., and safely recovered by parachute. This was an exciting event and provided a fitting climax to a short but wonderful visit to this beautiful and friendly country. A complete report on this trip will be presented in a future web page. A hearty thanks goes out to Ágúst Valfells and Magnus Gudnason for offering the invitation and for their wonderful hospitality. |
![]() A24-A3 motor firing ![]() New bulkhead and nozzles ![]() New 38mm test motor | Dec.2, 2007 Another round of test firings was recently conducted with my experimental ammonium nitrate (AN) and aluminum (AL) formulations. One formulation worked particularly well, resulting in a stable burn with a nice foot-long white flame (see photo at left). Buoyed by this result, I have been working on a scaled-up, 38 mm motor that will be used as part of this on-going test program. This motor utilizes a graphite nozzle retained within a steel shell (photos at left). The steel parts have been giving a protective coating of "Tool Black", a tough protective finish of cupric selenide. This motor also features snap-ring retention for the nozzle and bulkhead. In addition to conducting these test firings, I am working on a new web page which will give full details of my experiments with AN-AL compositions.
Videoclip of static firing
|
![]() Experimental AN-AL motors ![]() A23-A6 motor firing ![]() Richard Graf setting up SSJ motor in test stand | August 1, 2007 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. |
With a grain core diameter equal to the throat diameter, the six-segment SSJ motor (in stand, lower left photo) was expected to exhibit erosive burning. This was beautifully demonstrated in the measured pressure and thrust curves.
SSJ-4 KNSB motor thrust & pressure curves (English units)
(SI units)
(kind of cool how the measured curves exhibit that initial "kink" that matches the theoretical curve).
SSJ-5 KNDX motor thrust & pressure curves (English units)
(SI units)
(classic signposts of erosive burning are the pressure exceedance at start-up and the extended tail-off).
Images: AN-AL Experimental Motors
Measured chamber pressure curves
Thermite pellets for initiating combustion
Experimental motors for testing "A" formulations
Internal view of motor showing case-bonded propellant grain
End view showing nozzle retained by snap-ring
End view showing Bondo-Glass bulkhead with pressure port
Graphite c-star nozzles
Hydraulic ram setup for press-forming grains within motor casing
Fornulations
Videoclips:
Videoclip of SSJ-5 Static test (835 kbyte, wmv file).
Videoclip of SSJ-5 Static test (1675 kbyte, mpg file).
Videoclip of A23-A4 Static test (1238 kbyte, wmv file).
![]() ![]() | April 18-22, 2007 |
![]() ![]() | December 17, 2006 My newest SSJ "J-class" motor was successfully test fired on Dec.10th. Three firings were conducted (dismantling, cleaning and re-loading of the motor was pleasantly easy and troublefree). The main goal of the first two firings was to compare the effect of spacing between the six KNSB grain segments. The first firing had minimal spacing (1.5 mm) and the second firing had a much larger spacing (18.5 mm). The results were very interesting. The first firing results displayed the infamous "triangular" thrust profile. The second firing results, however, displayed a thrust profile very close to the design condition. These results suggest that the "triangular" thrust profile is a result of delayed ignition of the grain end faces (KNSB is known to be hard to ignite). Greater inter-segment spacing allows for turbulent flow to occur in the inter-segment region, facilitating ignition. Small inter-segment spacing provides a stagnant zone, which takes longer for ignition to occur at the segment faces. In addition to the SSJ motor, the A-100M motor was fired seven times, to collect data on the effect of potassium nitrate grade on performance. These results will be presented in a future web page. |
![]() ![]() | December 1, 2006 |
![]() | September 30, 2006 A milestone in the Sugar Shot to Space Project was recently achieved with the successful test firing of the 1/4 Scale Ballistic Evaluation Motor (BEM) that was successfully test fired on September 23rd. This "M class" motor powered by 6.8 kg (15 lbs) of KNSB sugar propellant is unique in the sense that it is "restartable". After firing its first "phase", there is an 18 second delay prior to firing ot the motor's second "phase". Read the test report |
![]() | April 14, 2006 Now that spring is here, static testing season has arrived once again. This past weekend featured eight test firings, including 5 tests of the A-100M motor with various propellant modifications, and the fourth firing of the L-class Liberty motor powered by epoxy-based RNX propellant (photo af left). Two of the A-100M experimental grains were produced using an innovative "vacuum-evaporation" method, which is being considered for use in the Sugar Shot to Space project (detailed in ssts_pdt_item6c.pdf). Also fired in the A-100M motor were two "sugar alloy" grains, as described in the Nov.19/2005 article below.
|
![]() ![]() | January 18, 2005 The new Liberty "L-class" solid rocket motor was successfully static tested on January 16, and performed flawlessly on its maiden firing! This is the largest motor that I have successfully tested, to date. The Liberty motor met its design goal, delivering 3337 Newton-seconds of impulse ( click for performance curve). The motor is powered by RNX-71V potassium nitrate/epoxy composite propellant in a "rod & tube" grain configuration.
Photos (from top, click on image for larger photo):
Video clip of motor firing (834 kb, wmv file).
|
![]() | Mar.27, 2004 The flight of Frostfire Two made it apparent that for higher altitude flights, an effective means of making the rocket visible during descent is required. A number of methods will be investigated before the next Frostfire launch. In the photo at left is a flashing strobe light unit that was recently constructed in an effort to investigate whether this might be one solution. The strobe unit is made from a flash attachment for my old 35 mm Pentax. An alternative would be to use the flash components from a one-shot camera, but I chose this unit because it is quite a lot more powerful, operating off a 6V power supply (as opposed to 1.5V). The xenon strobe bulb is housed in a transparent nosecone fabricated from cast epoxy. The flash rate is set at once every 5 seconds. |
![]() | This is the (unpainted) aft fuselage for my next rocket project. The hi-tech body tube and fins are fabricated from composite materials by my good friend Roman (composites expert). Made to my specifications, the fins have a NACA 0005 airfoil shape, and are constructed of carbon/kevlar reinforced epoxy skins, with syntactic foam core. Very stiff & extremely lightweight, no flutter with these fins! The fuselage is sandwich construction, also with carbon/kevlar reinforced epoxy inner & outer skins. Sandwiched between is an 1/8" (3 mm) phenolic honeycomb core. The fins are bonded onto the fuselage with structural epoxy (Scotch-Weld 2216), and will be proof-load tested in the near future. |
![]() | Jan. 24, 2004 Here I am "wind testing" the new "1 metre cross-parachute" that I just recently designed and fabricated. Construction technique is similar to the "1 metre semi-ellipsoidal parachute" that I designed some years ago. However, the cross-parachute is much easier & quicker to make. This parachute will be used on my next rocket, Frostfire Two. This rocket will be quite similar to Frostfire One, launched early last year (however, this rocket will not have induced roll!). Payload will consist of the R-DAS, the PET system in the Zephyr rocket, a transmitter (same unit that flew on Frostfire One) with a new audio beacon, and an Audio Data Recorder (ADR). The motor will be the Paradigm, which is capable of boosting the rocket to a one mile (1600 m.) apogee. |
![]() | Nov. 23, 2003 Several things have been keeping my busy of late. Besides composing the CD of my website (on-going), finishing off my new Zephyr rocket, developing an AN/KP/epoxy formulation, I have also recently prepared an RNX-73 (KNCP) grain with a new geometric configuration. I call this a "pseudo-finocyl" (a true finocyl has fins that taper along the length of the grain). This configuration is quite easy to make. A central bore is drilled, then a saw is used to cut the fins (thanks to Dave Muesing for the concept). |
![]() | Nov. 2, 2003 At left is a photo of the new Parachute Ejection Triggering (PET) module that I've just completed (click for hi-res photo). Three systems are combined in the one module: Air-Speed Switch for primary drogue deployment, Timer for backup drogue deployment, and a second Timer for Main Chute deployment. A number of design improvements have been incorporated, such as a redesigned lightweight g-switch and an epoxy encapsulated Mercury Switch for mercury containment in case of hard touchdown. Otherwise, the basic concepts are the same at the PET system used for the Boreas series of rocket flights. First launch of the yet-unnamed rocket will be in a few weeks from now. |
![]() | Oct. 4, 2003 Recent static testing was conducted to determine if Mr.Fiberglass epoxy would be suitable for RNX propellant. This brand has the advantage of being nearly 40% cheaper than either West System or East Systems, currently in use. The photo shows the succesful firing of PCM-11 loaded with RNX-73 propellant, validating this brand of epoxy. Another plus is that vacuum treatment during production of the propellant is not required. |
![]() | Sep. 2, 2003 The load cell (see below) worked like a charm. Together with the pressure data acquisition system, developed earlier, the thrust & chamber pressure curves for the Epoch motor were produced. The RNX-71V propellant also performed as hoped, confirming the design goal that this propellant be interchangeable with RNX-57. (Click for photo of test firing). |
![]() | Aug. 23, 2003 This is a photo of a 200 lb. (900 N.) capacity load cell that I recently built (see Strain Gage Load Cell for Thrust measurement). This load cell is fitted with four (full-bridge) strain gages and produces a nicely linear calibration curve. It has been mounted on the STS-5000 static thrust stand and will soon be used in conjunction with a pressure transducer utilizing the data acquisition system I built a few months back (see below) to collect both thrust and chamber pressure readings. This setup will be utilized in the static firings of the Epoch and Paradigm rocket motors loaded with RNX-71V propellant |
![]() | Static firing of PCM-5 June 22, 2003 This was another characterization test of a slab grain of RNX-57 composite propellant. This motor had a Kn=700 and a propellant mass of 208 grams.
View video: PCM-5.WMV (272 kbyte, sound is kinda weird) |
The above graph shows the measured chamber pressure for the two Slab motor static tests that were recently conducted (tests PCM-3 & 4). The Slab grains (see below) have a constant burning area (constant Kn) and it was expected (hoped!) that the pressure plots would reflect this with a more-or-less constant chamber pressure. Clearly, this "expectation" was dashed when I saw these curves...the pressure rises (nearly linearly) over the duration of the burn. Why? Inhibitor failure was ruled out after initial consideration. This behaviour has not been observed with RNX-57. After some head scratching, I recalled that RNX-62 was earlier noticed to be a lot more porous than RNX-57. Examination of the surface of the propellant under magnification revealed that RNX-62 has nearly 10 times as many minute bubbles or voids, estimated at 4000 per cubic centimetre (constituting about 10% of the propellant volume). Although these voids are very small (approximately 350 micrometre diameter), the large number of them may lead to a constantly increasing burning area (Kn) and an accelerated burn rate, explaining the odd pressure curves. The next "obvious" step is to determine the source of the bubbles (reaction between the West System epoxy & potassium nitrate, or some impurity...?).
Two new static test motors were recently designed and built and will be used for characterizing the RNX propellants. These motors utilize slab (rectangular) propellant grains with inhibited edges, which provides for neutral burning. These slab grains are 1/2 inch (12.7 mm) thick. Key propellant characteristics such as chamber pressure as a function of Kn, burn rate as a function of pressure, and characteristic exhaust velocity (c-star) will be measured.
A new data acquisition system has been developed for use with the PCM series of tests. Currently, the system will be utilized for chamber pressure measurement only, but will later be enhanced to measure motor thrust, as well.
A 0-5000 psi pressure transducer is connected to a simple INA122 based amplifier circuit, which in turn is interfaced to a DATAQ 154 A/D converter unit. This is controlled by software on the laptop computer, which also stores the test data.
The blue item in the photo is a manifold to which the pressure transducer, a 0-1000 psi digital pressure gauge, and a grease nipple are connected. This is used for calibrating the transducer...a grease gun supplies the necessary pressure.
Tailored to the faster burning RNX-62 epoxy composite propellant (utilizing West System epoxy), a BATES grain configuration was prepared. The casing was stretched to accommodate the 10% additional propellant, over the basic version of this motor which is powered by RNX-57.
This motor was static tested on April 19th (ERMS-19). The results are shown in the graph below.
Only the chamber pressure was measured. The indicated thrust is based on the relationship
F = Pc At Cf , where Pc is the chamber pressure, At is the throat area, and Cf = 1.4, the estimated thrust coefficient.
As the chamber pressure is on the low side for the Epoch motor (which has a rated design pressure of 1000 psi), the Kn will be increased for the next test. However, this particular Kn and grain configuration would be just about right for a PVC motor, giving a really l-o-n-g burn time! Hmm, food for thought...