Based on the recent lacking performance of the Contrails H222 nitrous oxide commercial hybrid motor, a pair of static fire tests were conducted to improve the ignition and severance of the nylon fill line. The latest of these static firings was conducted at the Friends of Amateur Rocketry site south of the RRS MTA on 4-17-2021. This was done for simple convenience since I was unable to attend the MTA launch event in the week prior. Mark Holthaus and John Newman oversaw my static firing and offered good ambien advice. Fellow RRS member, Dmitri Timohovich, joined me that day and brought his four channel firing box to conduct the remote fill and fire operations of the hybrid.
Dmitri connects the fill manifold to the nitrous oxide bottle at FAROrange fill and firing box for the hybrid motor Fill, drain and firing circuit for a Contrails hybrid rocket motor. The separate vent solenoid valve hasn’t been added. Weight scale is also a separate feature and not necessary for operation.
Nylon is one of the stronger polymer tubing materials which can handle the 900 to 1200 psig nitrous oxide pressure when flow is supplied from the solenoid valve controlled manifold. The problem is that this strength makes it difficult to quickly and cleanly sever the Parker NBR brand, 3/16” OD fill line allowing the nitrous oxide to flow against the fuel grain while gabapentin getting reliable ignition.
The original ignition method as designed by the manufacturer is a small resistor in place of an electric match and the use of a Pyrodex pellet which is essentially a pressed cylinder of black powder. The first flight attempt of the nitrous oxide hybrid rocket used this method but was not successful.
Contrails Rocketry, H222, 38mm, 16-inch high powered nitrous oxide hybrid motor
Earlier builds of the hybrid motor used electric matches and small scraps of composite propellant grain for a swifter and hotter ignition. The first two flights showed evidence of the fill line remaining connected. A better means of ignition and fill line severance was needed.
February 2021 launch of the hybrid motor in Larry’s 3-inch rocket body. It is clear that a hot plume is exiting the nozzle but the sharp arc to the north seems to indicate that the fill line is still attached.
The composite propellant is an ammonium perchlorate, aluminum powder and HTPB binder mixture with some red iron oxide used as an accelerant. These scraps were from RRS member, Larry Hoffing’s, small solid motor that he unsuccessfully tested at the MTA in 2019.
The Contrails H222 motor was mounted upside down due to the lack of a proper motor retainer feature. The static firing was the primary purpose which resulted in a feeble puncture of the filling line and no subsequent ignition.The aft end of the hybrid motor mounted for static fire at the RRS MTA on 3-20-2021Failed ignition resulted from the 3-20-2021 static firing. Disassembly revealed an excessive amount of electrical tape and an uneven burn around the fill line circumference was the most likely cause. Previous solid propellant grain motor test in 2019 was a failure, but the remaining tailings from the casting were useful in boosting the ignition power in prior hybrid motor tests
The last static test at the MTA failed to achieve ignition and only created a small tear in the fill line without achieving ignition of the grain. The composite fuel grain fragments were getting clean ignition but the electrical tape wrapping method I used failed to adequately focus the high temperatures to getting clean ignition and severance of the black nylon fill clomid visa line.
At John Newman’s suggestion, we used a small ring of composite propellant grain at the forward end inside the hybrid high-performance (HP) fuel grain. These were made from a 22mm cylinder that was cut to a 3/4-inch length and drilled out to a 3/8-inch hole size which is roughly twice the diameter of the black nylon filling line passing through. This larger hole would allow the electric match head to be in close contact with composite propellant ring. As the solid propellant charge burns it focuses the tremendous heat of combustion on the nylon fill line causing it to soften, extrude and cleanly sever.
John Newman uses his lathe at his shop to gently machine fuel grains for custom applications https://www.winwaed.com/blog/getting-antabuse-without-prescription/.The ring of 22mm diameter composite propellant grain fits within the head-end of the hybrid fuel grain and can be pressed flush to the edge. A 3/8-inch hole is run through the 3/4” long segment to allow the nylon fill line to pass through with enough room for the electric match head Floating injector (left) with the nylon fill line pushed into the Parker push-to-connect fitting. Composite propellant grain is pressed in flush to the edge and electric match head can be seen beofre it is secured to the fill line to get the proper position when the motor is assembled Snap ring, graphite nozzle and steel nozzle washer finish the motor grain assembly inside the 16-inch aluminum body of the H222 modelThe complete motor assembly clamped into the unistrut holding fixture. The clear vent line at the head end must protrude to the outside to give a visible and audible indication when the oxidizer volume is filled with liquid before committing to firing.Dmitri Timohovich makes adjustments to the clamps holding the hybrid motor in place. Peak thrust is just above 200 lbf according to the official thrust curve data for this H222 model.Four channel firing box sits at a safe distance from the static fire test stand.Dmitri Timohovich (left) and Dave Nordling (right) pose next to the unistrut mounted static fire mounting of the Contrails Rocketry H222 high-powered 38mm hybrid motor ready for testing at the FAR site on 4-17-2021
With everything in place, we called over the pyrotechnic operators in charge for this FAR event. After inspecting the connections and describing the fill and fire procedures, we were authorized to begin the short filling process.
Successful ignition of the hybrid motor at FAR
The hybrid motor was loaded, fired, reloaded and fired again. Both times stable ignition was achieved and the fill line dropped out of the motor as expected. We had to abort the initial second firing as visual confirmation of the nitrous oxide completing fill was not apparent. Given the hybrid motor has a small weep hole in the head end of the motor means that given time the nitrous oxide will leak out safely. The clear 1/8” acrylic vent line had become tangled in the unistrut obscuring the liquid plume. Trimming the acrylic vent line helped to keep the tip more visible on the second and last firing that day.
Cheap and simple, the 3-inch Little John from Mad Cow Rocketry
The next step will be to purchase a 75mm rocket body able to integrate the 16-inch long, 38mm standard hybrid motor inside. The 3-inch Little John rocket from Mad Cow Rocketry was selected and should arrive soon. With luck, the rocket can be built and ready for 1010-rail launched flight at the next RRS MTA event on 5/1/2021.
The RRS is thankful for the support of FAR at their facility for this static fire. Dmitri and I conducted a safe dispoal burn of the scrap propellant. I was able to acquire a few more propellant ring segments for subsequent tests of the hybrid in flight. Later, we plan to revisit the Pyrodex black powder charges with the electric resistors as the initiator. It is not clear if this will be as effective as the high temperature composite grains and an electric match, but it is worth a try.
The RRS held a launch event at our Mojave Test Area (MTA) on April 10, 2021, the day after our monthly meeting. COVID-19 still remains a threat so everyone continued to observe protective protocols – masks & physical distancing. For the first time in months, we had a day with great weather for launching rockets and we made the most of it! We had low-power, high-power, and experimental solid rocket launches, another launch of Bill Inman’s Solar Cat, the maiden voyage of Wolfram Blume’s Gas Guzzler, and a static fire of Larry Hoffing’s solid power motors. Osvaldo Tarditti was our pyrotechnic operator in charge.
Activity around 9:30 am at the MTA – prep work ongoing for CTRL+V (left) and Solar Cat (right)
CTRL+V (USC RPL)
Preparation for the first launch of the day: CTRL+V actually began the day before launch with motor integration and other preparation work taking place at the MTA site. On the morning of the launch, the team from the USCRPL installed the rocket on the launch rail, which was then raised into place south of the MTA’s vertical test stand. Wires running from the rail were staked to poles and hammered into the ground to provide additional stability for the rail. Several launch crew members can be seen prepping the rocket above, and a still image of the launch of the rocket can be seen below.
Launch of USC RPL’s CTRL+V, the smoke took a strange path up the rail faster than the rocket!
The rocket flew on a 6″ experimental rocket motor. A specific procedure was followed prior to launch, under the supervision of the pyro op, which included radio go/no-go call outs from several teams including tracking, avionics, and even a drone that took footage of the launch! All spectators and crew were in the bunker during takeoff at 11:04 am – ignition was prompt and rocket left the rail quickly and cleanly. The initial telemetry reported by the team indicated an altitude of over 11 km. Several members then went off on the daunting task of recovering the rocket from wherever it landed.
LUMINEER (BPS.space)
The next flight of the day came from BPS.space with the rocket Lumineer. This launch was conducted from one of the pads just west of the vertical test stand. The flight took place around 1:20 pm on a commercial Cessaroni “N” motor and was livestreamed to a reported 9,000 viewers on YouTube. The rocket utilized a “fly-away” rail guide to provide stability and eliminate the drag of rail buttons, which can be seen still in the process of falling from the rocket in the image below. The target altitude was 10 km, but telemetry was lost shortly after takeoff so the actual peak altitude was unclear after launch, and the rocket was not recovered for some time.
Launch of Lumineer from BPS.space
GAS GUZZLER (Wolfram Blume)
Wolfram Blume has been diligently making the pilgrimage to the MTA events over the last several months and the weather has been uncooperative for his chances of launching, but that finally changed in April! The maiden voyage of the GasGuzzler took place from the pad just west of the vertical test stand. This flight was conducted to answer several questions about staging during the flight – so the ram jet second stage was flown empty and only the first stage, commercial solid rocket motor was used to power the rocket. A slow-motion (10% full speed) video of the launch can be seen here.
Launch of Wolfram Blume’s Gas Guzzler, it’s so calm the flag on the vertical test stand isn’t waving!
The ascent of the rocket was smooth, validating the rigidity of the rocket’s design and the stability when empty. The data from onboard altimeters confirmed that the ram air entering the 2nd stage was enough to separate the 2 stages immediately (0.1 second) after motor burnout which occurred at 1,440 ft. The parachute for the booster stage deployed successfully and that stage was recovered without damage. The ram jet, upper stage utilizes a dual-deployment of a drogue parachute at apogee and main parachute at 1,000 ft above the ground. While each of these deployments were successful, the main parachute did not pull out of the deployment bag so the stage landed hard and damaged a few parts. Fortunately, the 2nd stage is not the final parts intended for the full flight of both stages so there will not be delays to the project to rebuild. Wolfram collected lots of useful data and plans to add a GPS tracker and other upgrades before his next flight. We all hope the weather remains in his (and all of our) favor!
CHARLIE HORSE (Keith Yoerg)
Up next was the 12th flight of Keith Yoerg’s rocket Charlie Horse. This was the first flight test of the LoRa GPS tracking boards discussed in previous reports. There are several difficulties with getting the units setup properly, not least of which being the frequent firmware updates required to pair the board with the mobile phone app (2 updates in as many months). Powering up the boards the night before would have helped eliminate these struggles, but a successful launch was still completed, a slow-motion (10% full-speed) video of the launch can be seen here, which was on a commercial Cessaroni I280-Smokey Sam motor.
Keith Yoerg’s Charlie Horse seen through the smoke of launch – the camera was tipping over!
One issue still to be resolved with the LoRa trackers is a setting within the Meshtastic mobile application which trades off tracking range for the speed at which new information packets are sent. The “medium” setting was used on this flight but for rocket flights it may be advantageous to reduce the range (which is purported to be up to 10 miles) in favor of more frequent location updates. More testing will be done on future flights in hopes of developing a cheap, simple GPS tracking available for rockets flying at the RRS.
SOLAR CAT (Bill Inman)
Bill Inman’s solar-heated steam-powered Solar Cat rocket took to the skies around 4:31 pm. While the weather was perfect for most of the projects, the light overcast that can be seen in the pictures above proved problematic for the solar heating required for the best flight. In addition by launch time, the solar collector was at its westernmost limit so no more heating was possible. At launch the water temp was 370 F and was at 130 psi.
Bill Inman’s Solar Cat takes to the skies for it’s 2nd launch at the MTA
The flight reached 41 mph speed and achieved a 60 ft altitude. While this was an improvement on the first Solar Cat launch at the MTA, with additional heating there could be even more impressive stats. While he can’t control the clouds, Bill hopes to arrive at the MTA site the night before a launch in the future to increase the chances of getting off a good test and launch before reaching our western limit of travel for the solar collector.
THE YOERG CHALLENGE (Dimitri Timohovich & Keith Yoerg)
With this being Dimitri’s last MTA event before leaving to Alaska for the summer, some other RRS members need to step up to the plate to keep the “Yoerg Challenge” alive. I have put out the call for more RRS members to build low-power rockets to fly at the MTA, and have left my 5-pad PVC launcher at the site for future launches. IT’S CHEAP, IT’S FUN, IT’S A CHALLENGE (and everyone is a winner)! What’s not to love? So get out there and build some model rockets!
The remains of the “Space Crater” – not covered in raw egg!
The entrants this month included Keith’s Big Bertha, Baby Bertha, and Hi-Flyer XL rockets and Dimitri’s Space Crater – which carried eggs in honor of Easter this month. Fortunately, Dimitri’s wife had the foresight to hard-boil the eggs because his rocket took the “Crater” part of its name a bit too seriously (the remains are shown above). A few of Keith’s flights before the GoPro battery died can be seen here.
SOLID MOTOR TEST FIRE (Larry Hoffing)
Larry Hoffing had some experimental solid rocket motors ready to test fire, but with all the other activity going on at the site he took the time to install a new “No Smoking” sign on the covered propellant loading area (shown below). Once things were a little less active, Larry was able to affix the motors and perform a test-fire. While the burns were long, they did not produce much thrust and need to be improved upon before use in a rocket.
No smoking sign added to the covered propellant loading area by Larry
CONCLUSION
In addition to everything detailed above, one of the USC RPL members flew a high power rocket to earn her Level 1 certification with the National Association of Rocketry, and Dimitri flew his water rockets with his son.
This was by far the most active event at the MTA in the past year and was an exciting day for anyone who likes to see rockets fly! Our next launch date has not been decided upon, but we hope to have an event in May to continue hosting at least one event per month at the site.
The RRS held a launch event at our Mojave Test Area (MTA) on March 20, 2021, the spring equinox. COVID-19 still remains a threat so everyone had to observe protective protocols. We had a lot of wind that day making launch impractical, but we still were able to get many things done that day including another static fire of a hybrid motor, some system checkouts of the Gas Guzzler and a possible flight of the Solar Cat steam rocket. Osvaldo Tarditti was our pyrotechnic operator in charge. Also joining us that day was fellow Rockets 2nd Class pyrotechnic operator and RRS member, Jim Gross,
MOBILE TRAILER CLEANUP
Mike Gottlieb was a lifetime member of the RRS who passed away over 2 years ago. Years prior, he had acquired a surplus mobile trailer from the former Rockwell International company which was left to reside at the RRS MTA. By permission from his surviving family, this single-axle, climate controlled trailer has been donated to the society. The trailer was opened by the RRS president and the interior inspected by our members present at our March 2021 launch event.
The Rockwell mobile trailer at the RRS MTA The interior needs a little work but otherwise has a lot of promise.A spacious interior which could be used as an office space.
For now, the space will be used for light storage until more space can be acquired elsewhere. We used the time to reorganize the contents of our storage trailer. We hope to renovate this new mobile trailer soon and restore its climate control systems which will be convenient in the summer months.
PUBLIC ADDRESS SYSTEM AT THE MTA
During the cleaning and reorganization of our storage space, we pulled out the public address equipment we had. The 12 VDC battery powered system including loud speaker and microphones worked well in a test from the old blockhouse. The society has talked about having a more distributed system around the main areas of the site. This will require some further equipment purchases, but for now we have a core system to start from. The goal is to make coordination of our events easier to do when we have large groups of people at the MTA again. Further still, we’d like to coordinate launch timing better with our neighboring amateur rocketry group (FAR) to our south.
Keith Yoerg holds up the speaker after a successful test at the old blockhouse
NEW RESTROOM FACILITY
As discussed at the March 2021 monthly meeting, the society is going forward with building a new restroom facility with flushing toilets. This will be a big convenience to our visitors and members alike. The executive council has received bids and plans for the restroom and is working with suppliers to find the best solution given our budget. We are grateful to our generous benefactor and the many people who supported this project with their time and skills. More progress should be made soon as we would like to deploy this facility before the hot summer months arrive this year.
General placement of the proposed new restroom facility at the MTA subject to change and only for illustration..
FIRST FLIGHT OF THE SOLAR CATFROM THE MTA
Bill Inman and new member Jonathan Wells returned to the MTA for another attempt to launch the solar powered steam rocket, the Solar Cat. He has been making many adjustments and had his first launch near his home in Carson City. Today would be his first launch of his Solar Cat from the MTA.
Bill Inman and his team set up his parabolic solar heating system for today’s sunny day at the MTA
Bill was able to work out minor problems on his trailer mounted systems last month and was fully ready to use his solar heating and tracking system for the hours necessary to reach launching temperatures of the stored water load in his steam rocket.
Bill has had some minor problems with the release system which led to a unintended release of the rocket. No one was injured but it did cost him several useful hours for insolation (heating). His second attempt was only a partial heat load but sufficient to conduct the first (technically second) flight at the MTA. Keith Yoerg managed to capture the short flight in the late afternoon. It’s a bit comical to watch given how short the flight was, but it is a significant milestone in getting this non-traditional form of liquid propulsion to work. We look forward to the advancements, Bill will make for future flights from the MTA.
The Solar Cat gets a clean release from the launcher and clears the rails on 3/20/2021.The Solar Cat reaches its apogee while still in the frame of the video recording.The wind pushes the rocket back to the launcher for an ungraceful return then clonking to the ground.
REBUILD AND SYSTEMS CHECK OF THE GAS GUZZLER
Wolfram Blume had made several improvements since his last flight attempt of his two-stage ramjet-solid motor rocket. He was able to correct software issues but also made physical feature changes to his booster. Wind speeds were excessive for much of the day, so he used his time at the MTA for fit checks while on the 1515 rail launcher.
Osvaldo Tarditti and Bill Janczewski observe Wolfram Blume’s operations with his ramjet upper stage in our loading area. No gasoline will be used in the maiden flight which will test the booster and staging systems. The unique design will need some flight testing before committing to a full flight with a fueled upper stage,Wolfram Blume walks to the launch pad where his Gas Guzzler rocket rests on the pad.
Wolfram was able to conduct his tests making use of the 1515 rail launcher. He left in the afternoon after completing his tests and will return for our next launch event planned for April 10. 2021.
WIRELESS FIRE CONTROL AT THE MTA
Wireless fire control is a remote means of conducting launch without stringing long wire connections. This has been a controversial subject at the RRS with some of our members actively supporting using these systems and others being skeptical about their safety.
Richard Dierking mentioned the Wilson F/X wireless firing system which has been used at the Rocketry Organization of California (ROC) and at the Friends of Amateur Rocketry (FAR) site. Fellow RRS member, Dmitri Timohovich, has used Cobra Firing Systems for pyrotechnic events in the movie business with success. He brought one of these systems to demonstrate at the MTA with test bulbs. The 64-bit encryption in this system vastly reduces the possibility of stray signals causing an unintended firing.
Two 18-channel fire control boxes with the remote in the middle.
A decision was made at the March 2021 meeting to proceed with care by testing one of these wireless fire control systems with only low-power simple model rockets. We also thought meeting with a sales representative or technical advisor from a wireless fire control system manufacturer to explain the safety of these systems to the society would be an excellent idea. Some of our members have had a negative experience with these systems with unintentionally firing. Older wireless fire control systems have had safety issues. Safety in operations with pyrotechnics of any kind is of paramount importance.
wilsonfx.com
cobrafiringsystems.com
The RRS plans to educate themselves further about wireless firing system technology before making any further policy decisions. It is agreed that every pyro-op in charge at the event has the final say about what systems are and are not allowed at the event. The best course of action for any project leader is to discuss all aspects of their test or launch with the pyro-op in charge well in advance of the event at the MTA.
STATIC FIRING OF THE HYBRID MOTOR
The last two firings of the Contrails H222 38mm 16-inch hybrid motor left some questions about how reliable the ignition of the motor is. From both prior flights, it was evident that quick severance of the nylon plastic fill line at the launch command was not happening. Altitude was very low from such a powerful motor according to the curve. Since the last flight damaged the rocket body beyond repair, the next firing was intended to watch the startup sequence in careful detail under static conditions.
The motor survived in tact from the last short flight, The nozzle, spent grain and floating injector were shoved forward from the impact, but all parts were able to be removed, cleaned and reassembled for another firing with the last of my three fuel grains from the kit.
.The Contrails H222 motor reloaded for the third time.
The static test firing was done on the vertical test stand using a simple wooden fixture and 1/2-inch fasteners. The fixture was built quickly and unfortunately not perfectly. We had to fire the motor upside-down which is not representative of how the engine flies.
The vertical test stand holds the hybrid motor ready for firing with the fill line above and clear vent line below.The 3/16” nylon fill line c0nnects to the floating injector push to connect fitting below the fuel grain and graphite nozzle held down by the snap-ring. The electric match is wrapped along side of and held against the fill line.Acrylic 1/8” vent line from the top bulkhead push to connect fitting
The igniter used in the 3-20-2021 test used an electric match as was done in the second test. The kit comes with an electric resistor. In the first test, this was insufficient to get ignition and sever the fill line. Second firing used an electric match and a fragment of composite propellant. This achieved ignition but the fill line wasn’t fully severed. The third attempt used a similar load with a bit more composite propellant. The idea was to produce an ignition flame hot and fast enough to soften and sever the pressurized nylon fill line, With the escaping oxidizer liquid, the combustion should be enhanced and help sever the line. In practice, this doesn’t seem to occur quickly enough,
In the hybrid firing that day, the igniter fired and some chuffing from the nozzle was seen but the combustion was not sustained and the oxidizer supply emptied. The motor will be disassembled and inspected to see if all the composite propellant was consumed or if the nitrous oxide dispersed the pack before the full burn could finish.
A thin piece of composite propellant pressed against the electric match head pressed against the nylon fill line.Floating injector loaded with the igniter and fill line strung through the fuel grain and nozzle.The hybrid firing box with ruggedized 100-foot cableThe new hybrid rocket firing box with built-in solenoid valve and fire control.
MORE WATER ROCKETS
Dmitri upgraded his water rocket launch system to fire multiple rockets. He had a remote firing box which made it very easy to set up. The winds were too strong for any high altitude flights, but the modest water rockets were plenty of fun.
Water rockets lift off from the new blockhouse.
MODEL ROCKETS
The Yoerg Challenge started as a simple request to those attending our meeting on March 12, 2021 before the launch event: build as many model rockets from as many people as possible and launch them from the multi-wire launcher array that Keith built last month. Dmitri and I both answered the challenge for the event, Although many of our members have built many model rockets since they were kids, some of have not. For those experienced and inexperienced, the Yoerg Challenge was issued. More rockets at each successive event inspires others to build more rockets and more ambitious rocket builds. The RRS is for all forms of reaction propulsion even with a simple model kit.
The Estes Generoc E2X loaded with a C6-7 motor. An inexpensive and simple answer to the Yoerg Challenge,Dmitri Timohovich built the Firestreak SST for the Yoerg ChallengeA few model rockets fly up and away at our arch.
At the end of the day, Keith and Dmitri launched their model rockets using small “A” sized motors to keep their altitudes low and avoid being carried far downrange with the high winds. I decided not to fly my first model as I left early that day. We hope others will build and bring theirs at our next event.
IN CONCLUSION
Next launch event will be April 10, 2021, with USC and member projects.
