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MTA Firing Event, 2024-06-08

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by Dave Nordling, Reaction Research Society

The Reaction Research Society (RRS) hosted a unique event with our clients, American Artist and the Los Angeles County Museum of Art (LACMA) at our private testing site, the Mojave Test Area (MTA). This was a two day event that began with an all-day filming and liquid engine static fire event on Saturday, June 8th at the RRS MTA. The next day began with a late luncheon, round-table discussion and short film presentation held at the Voyager Restaurant at the Mojave Air and Spaceport on Sunday, June 9th, 2024. The RRS was one of several invited guests including representatives of the Getty Foundation and Hyundai. Dr. Ayana Jamieson (Cal Poly Pomona) and members of JPL and LACMA also attended. The final event was a live performance and static firing of the replica engine at the RRS MTA which was a resounding success. I was the pyrotechnic operator in charge for both days with Dimitri Timohovich serving as my apprentice.

Seated from left to right, Adam Kleinman, American Artist and Dr. Ayana Jamieson, at the Voyager Restaurant in Mojave, California

Excerpted from LACMA press release:

American Artist: The Monophobic Response documents a meticulously crafted yet poetically altered re-creation of a pivotal 1936 static rocket engine test that initiated the United States’ venture into space travel. Inspired by Octavia E. Butler’s 1993 novel Parable of the Sower, which unfolds in the imagined dystopic year of 2024, American Artist performed and filmed The Monophobic Response in the Mojave Desert at the Reaction Research Society’s Mojave Test Area in the same summer of 2024. Artist’s interpretation involved an actual rocket engine test fire against the dry, desolate Californian landscape, creating eerie juxtapositions between Butler’s prescient visions and our troubling realities. Drawing parallels between Butler’s fictive 2024 U.S. presidential race led by an anti-space demagogue and the impending real-world election, this installation weaves together thought-provoking takes on our collective liberation and the concept of our shared “Destiny.”  

The 1936 GALCIT engine was one of the first American bi-propelllant rocket engines. The photo above is often referred to as ‘the Nativity scene’ of early American rocketry showing a young, scrappy group in the Arroyo Seco outside of Pasadena, California, making some of the first steps in a field of science not yet fully appreciated in their day.

The project with the RRS began in the Fall of 2022, when LACMA approached the president to gauge how practical it would be wanted to build and fire a full-sized replica of the same bi-propellant liquid rocket engine from the early days of the Guggenheim Aeronautical Laboratories of the California Institute of Technology (GALCIT). The project to replicate and fire this vintage engine was relatively simple for the RRS given our society’s long history with experimental propulsion. And so began the planning and study of what was known about one of the first liquid bi-propellant engines built in the United States from just a handful of scanned black and white grainy photos and hand sketches courtesy from JPL archives.

Thanks to this museum-funded project, with a few suppositions, some imagination and basic calculations, the RRS team was able to build a reasonably accurate replica of the 1936 GALCIT liquid methanol and gaseous oxygen bi-propellant rocket engine and it’s associated static fire vertical thrust stand. The most important aspect of designing this replica was not to aim for performance but rather to correctly interpret what the intended design might have been given the limited knowledge and resources of the period. To fire on command and operate safely were the two primary principles guiding this project.

RRS MTA, 6/1/2024, From left to right: Joe Dominguez, Dimitri Timohovich, Dave Nordling, Leanna Lincoln, Bill Nelson, Tre Willingham, David Stevenson, Manny Marquez, Aarington Mitchell

From careful examination of a cross-sectional drawing by Frank Malina and Jack Parsons, the scale size and key dimensions of the engine features were determined. A narrow half-angle of only 3 degrees was used in the nozzle design for this prototype ground test article. GALCIT must have been concerned with flow separation but had not yet developed a sense for how large the divergence angle could reasonably be. Design chamber pressure was not stated but it was assumed to be fairly low. Typically, amateur liquid propellant rocket engines operate around 300 psig. The design was shown to be sufficient for 500 psig, but in firing operations, the engine was run at only 50 psig both for safety and simplicity of the central task to get the engine to work on command and not overtax any component.

The engine was built in stackable steel slabs and a threaded in nozzle to form the desired internal chamber shape and bolted together. This practice is still used in university and professional test articles. The absence of sealing details in the sketches led our team to build graphoil gaskets that were custom built for the exact engine interfaces. It is very likely with this early engine design, as it is with engines built today, the first problem is combating leaks.

RRS testing found these graphoil gaskets lasted several prolonged firings. As the lower temperature binder material cooks out from the heat, the graphite portion still maintained pressure sealing as long as the joints remained undisturbed. Only after a hard ‘pop’ on the sixth engine firing did evidence of hot gas leakage occur. The RRS was able to disassemble, repack with new seals and reassemble the engine for another round of firing. No damage or erosion was seen on any interior surface including at the entrance to the nozzle throat.

The GALCIT engine design from the photos had what appeared to be a liquid water cooling jacket surrounding the outside of the engine head, middle and tail pieces. Photos show a sheet metal wrap which would infer a low pressure “dump cooling” approach. Photos show a square sheet metal can with a single feed line to allow gravity to fill the volume with liquid and let any steam or extra water to fall out of a short U-tube connected from a top port. For the sake of the exhibit and replicating the look of the engine tested at the Arroyo Seco, the dump water cooling port and sheet metal wrap and tank were added. In hot-fire testing, the feature proved to be unnecessary as the thermal mass of the engine steel plates was large enough that they never got excessively hot even after 20-30 seconds of continuous firing.

The engine was supported by a spring loaded shaft which fit into a black pipe. The design intended to have the pipe partially filled with water for dampening any oscillatory movement. The replica thrust stand was built with all of these features but no water was added as the friction between the parts was sufficient to dampen the movement. Corrections to the sketches seem to indicate internal support pieces were added to help guide the shaft’s movement along the center. Our own experience showed this to be a wise change so our replica also put these pieces inside for less troublesome movement. The rest of the thrust stand formed a simple flat base built from steel C-channel and angle materials. Seal welding of the pipe to the flat side of the C-channel was done but since no liquid fill was used, leakage in this area was of no concern. The thrust stand was calibrated with weights and found to be considerably and consistently linear as we had hoped based on the selected spring size we used that seemed to match the scale of the item in the period photos.

The original propellant feed system was done with manually operated hand valves with a person working from behind a single sandbag wall just a few feet away from the engine plume and noise. This was pretty gutsy and not a very safe approach but then again the early rocket pioneers at Caltech earned the moniker of “the suicide squad” for good reason. With safety in mind as required for all RRS operations and the members who would be firing the engine replica in the film, electrically activated pilot-operated solenoid valves were added to both propellant feed systems powered by 12-volt lead acid batteries.

The specific location was important for the film. American Artist and Chester Toye surveyed the MTA and found the empty space to our west and north with an open view of the northern mountain range and the western view of Koehn Dry Lake to be most scenic and appropriate for the film.

GALCIT-built prototype bipropellant rocket engine, October 1936, Arroyo Seco, outisde of Pasadena, California; image courtesy of JPL Archives

Sandbag walls were a common protective feature for early rocket experiments conducted in open field areas on the edge of town. The RRS painstakingly recreated these barriers thanks to the hard work of many volunteers. The society had an existing sand berm to protect the operators and all other spectators were at sufficient distance for the total impulse of the engine.

Our team saw no pictures of the firing box used by the GALCIT team in the 1936 Arroyo Seco firing, so we presumed to use a common metallic hobby box with the keyed safety switch required by California state law in amateur rocketry events. Some of our first engine firings with the complete feed and control systems were near the underground blockhouse to verify basic functions of the equipment and train operators in how system works and what to do if an anomaly occurs.

The oxidizer supply to the engine was simply gaseous oxygen from a high pressure tank. It’s likely the GALCIT team borrowed an oxygen gas bottle from a welding rig and used a low pressure regulator to control the flow into the engine. The RRS setup similarly used a high pressure regulator, commercial high pressure oxygen bottle and a swing-type check valve as seen in the oxygen supply manifold from archive photos.

The liquid methanol fuel supply in the 1936 GALCIT setup was likely pressure fed from a separate tank into the engine. A partial view of the top of what might have been the liquid run tank was seen in one of the JPL photos. In the modern replica, the RRS made a vertical welded pressure from 4-inch nominal stainless steel pipe and end caps welding on 1/2” NPT bung fittings. The tank is clamped to a pair of unistrut segments welded into a free-standing steel box frame structure that keeps everything steady and upright.

Gaseous nitrogen from a high pressure bottle and a high pressure regulator allowed controlled liquid flow into the engine. The liquid was loaded into the tank from the top when the tank is unpressurized. The fuel run tank manifold at the top has a seal plug and a manual valve. Below these but above the top of the tank is a pressure gauge and a spring-loaded relief valve set to 500 psig. The liquid fuel leaves the run tank at the bottom to feed the engine at the fuel inlet port. The bottom manifold on the fuel run tank has a second manual valve which opens for draining.

The GALCIT team likely used simple rubber tubing for both fuel and oxidizer feed. Information indicated that the GALCIT team had an oxygen fire in one of the lines. The GALCIT team likely added the swing check valve into their regulator manifold after this problem occurred. The RRS setup used 1/2” oxygen-cleaned and teflon-lined flex hoses to mitigate the threat of a hose becoming a fuel source in a pure oxygen environment. Modern flex hoses with their stainless steel wire braiding also offer much higher operating pressures for additional safety in operations in the event of surges or pops from the engine.

For the fuel line to the engine, a high quality braided and overwrapped hose was used but modern hoses have bright colors and text along the length which seemed to disrupt the vintage look of the replica setup. This was mitigated with large diameter black heat shrink tubing used as insulation over large wire gauge bundles. With a little teamwork, the long 1/2” diameter fuel hoses were covered in a tight-fitting, but non-descript black covering looking more like the simple black rubber tubing of the GALCIT setup. The added shrink-wrap layer also proved to be a good barrier against abrasion and a temporary sacrificial layer needed to protect the lines during engine fires that happened in early testing. Any damage to the outer layer was easily patched with simple black electrical tape keeping the look of a distressed experimental rig.

Methyl alcohol or methanol was once a common household or industrial solvent for a variety of purposes. In the modern day, common solvents tend to be a loosely controlled mixture of cheap hydrocarbon compounds readily available from refineries. To better know the proper mixture ratio for running the engine, the team stayed with sourcing pure methanol. Methanol in bulk 5 gallon metal containers is found in the sports car racing industry from a local supplier, Dion and Sons, in Van Nuys. An abundant supply was found to be fairly affordable.

Ignition of the engine was initially done by pyrotechnic means. An election match in a small packet of composite solid propellant shavings was our approach, but despite the sufficient energy in each of the charges, significant iterations and team ingenuity and striving for simplicity, the reliability of retaining the igniter charge in the nozzle long enough to achieve engine ignition more than once proved to be very frustrating. The GALCIT team used black powder packets and had similarly poor results in reliable retention of the igniter charge in their engine at start.

In the end, both the GALCIT team and the RRS opted for the spark ignition method which proved effective and repeatable for both teams. The GALCIT team likely used a Ford Model T spark coil still commonly available among vehicles at that time. An old Exide battery was seen in one of the period photos but next to it is what appears to be a spark coil or ‘buzz box’ which was likely used for engine ignition in later firing attempts.

The RRS used a model aircraft spark plug which used a similar voltage multiplier circuit likely found in a ‘buzz box’ that would fire a vintage automobile spark coil. Grounding to the large metal test stand and running a single wire into the nozzle or throat of the engine was likely how GALCIT succeeded. The RRS directly tapped the middle ring of the engine and submerged the spark plug end inside the thrust chamber. After seven firings, the spark plug still fired perfectly with minimal damage from the extended hot gas exposure.

The team considered using a glow plug type of ignition device but given the immediate and repeated success of the spark igniter, we did not attempt this approach. The method does have promise but it will have to be demonstrated in a later member project.

Although we were very successful, the RRS was wise enough to make many replacement seals of all joints and had several spare spark plugs should our luck not be as good.

Putting a lot of hard work upfront and running many tests proved to be the deciding factor in our project’s success.

LACMA-American Artist filming day at RRS MTA, 6/8/24, from left to right, Dimitri Timohovich, Frank Miuccio and Dave Nordling

Filming of the event proved to be challenging for many not used to prolonged hours in the Mojave desert heat. The early June temperatures reached 97F which marked the end of the milder and cooler spring just a week earlier. Although we had a field medic present to assist anyone overcome by the high temperatures, we had very few that required assistance. Still, operations always occur more slowly and less efficiently when the air temperatures get high. The film crew was able to create the scenes necessary and the engine was able to fire on command, but the long day tested everyone’s resolve and thanks to the professionalism of many people and acts of kindness large and small, the project achieved its objectives.

Flame color experiment with strontium chloride salt added to a small amount of liquid methanol burned in open air in a stainless steel dish.

For improved visibility of the engine plume in hot fire, strontium chloride salt was added to the liquid methanol providing a bright red/magenta color that could be seen even in the harsh glare of the mid-day sun. Other compounds were tried in similar open flame experiments but none produced a flame color bright enough to be seen in the harsh daylight of midday.

Once a reliable firing process was discovered, the team did not deviate making sure our team could execute our tasks without mistakes and our clients had the visual spectacle they required for this artistic endeavor.

Achieving a proper oxygen to fuel mixture ratio was an early problem, but easily solved by creating a wide range of orifice sizes through drilling set screws that allowed changes to be made quickly in this simple single element injector. Again, it bears mentioning that this project was to nearly fully replicate the early 1936 GALCIT design including injector features that are now known to be very substandard in terms of mixing and combustion efficiency.

Once the internal orifice screws properly balanced the oxidizer and fuel flow rates, the engine could be fired repeatedly. The engine proved to be very robust with little or no erosion on any of the interior surfaces even after 20-25 seconds of hot fire under the slightly fuel rich, methanol/oxygen flame temperatures. The custom-cut graphoil seals were able to last for several firings and only requiring replacement at the end of the day. The model aircraft spark plugs continued to operate even after half a dozen firings. Orifice tables were made that allowed for quick estimates of flow conditions under varying supply pressures. Although the intention was not to find any optimum conditions or settings, having the ability to adjust variables quickly in the field and knowing the directions of ‘goodness’ well justified the effort.

A very important part of the production involved two of our society members, Tre Willingham and Aarington Mitchell, who both acted in the film and fired the engine under the oversight of the pyrotechnic operator in charge, Dave Nordling, with fellow member Dimitri Timohovich’s assistance. They each gained practical experience in safely firing a rocket engine and managing the task in the summer heat of the Mojave Test Area. The society was able to give them sufficient field training in advance to allow them to act confidently and safely should problems arise. The yellow towel seen in the photos was used to cover the batteries and switchbox from the direct sunlight of that hot June afternoon in 2024.

Bill Nelson and Dave Nordling collected photos and videos taken from the RRS MTA over the months, weeks and days leading up to the event capturing the evolution of the replica engine and its analog thrust stand through hot-fire tests experiments, failures and finally successes

Bill Nelson is compiling a short presentation of the whole LACMA-American Artist project for the upcoming June 2024 monthly meeting on the 2nd Friday of each month (June 14 in this case). RRS monthly meetings are always held at 7:30pm at the Compton/Woodley Airport. Contact the RRS secretary, vice-president or president for the teleconference information.

Many RRS members contributed to the success of this project over the span of nine months leading up to this June 2024 event. The society would like to recognize and thank the following society members.

  • Dimitri Timohovich
  • Bill Nelson
  • Waldo Stakes
  • Tre Willingham
  • Aarington Mitchell
  • Manuel Marquez
  • Joe Dominguez
  • Leanna Lincoln
  • Chase Lang
  • Wilbur Owens
  • Frank Miuccio
  • Rushd Julfiker
  • Dave Nordling

The Reaction Research Society would like to thank the following individuals for their support, assistance and contributions to the success of this multifaceted project. The project was truly a great example of how all five studies of science, technology, engineering, art and mathematics, can be applied to produce something great.

  • American Artist
  • Chester Toye
  • Joel Ferree, LACMA
  • Dr. Ayana Jamieson, California Polytechnic University, Pomona
  • Dr. Eric Conway, Jet Propulsion Laboratory
  • Adam Kleinman
  • The student volunteers of the University of Michigan, Ann Arbor (MASA)
  • Aaron Miller, Weld Services Inc., Bonsall, CA
  • Mike Vanoverbeck, Compton College, Compton, CA
  • Ron Gerlach
  • Bill Heather
  • Compton/Woodley Airport, Compton, CA
  • Edwin “Ham” Metz, Linde Gases, Lancaster, CA
  • Dion & Sons, Racing Fuels, Van Nuys, CA
  • Titan Fittings, Denver, CO
  • Shane Hermanson, Field Medic
  • Karri and Derek Toth, Snake Wranglers, Palmdale, CA
  • Derek Honkawa, Friends of Amateur Rocketry

For questions and inquiries about similar projects and topics, contact the RRS president, Frank Miuccio.

president@rrs.org

MTA Launch Event, 2021-12-17

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by Dave Nordling, RRS.ORG

The Reaction Research Society held its last launch event of the year 2021 at the Mojave Test Area on Friday, December 17th. I was the pyrotechnic operator in charge. This was my first launch event as a Class 1 pyrotechnic operator although none of the activities this day involved a liquid rocket. We had four launches planned for that day. Two from Keith Yoerg, one from Wolfram Blume and one from Dimitri Timohovich. RRS members Wilbur Owens, Xavier Marshall and Bill Inman came to be spectators at this launch event.

Bill Inman at the RRS MTA on 12-17-2021

IMPROVEMENTS TO THE 1515 RAIL LAUNCHER

The first flight of the Hawk in late November revealed a concern about the stability of the 1515 rail launcher with heavier rockets. Although quite heavy in its steel rectangular tube construction, Dimitri and Keith used cinder blocks and sandbags to weigh down the legs of the base. This resulted in damage to several of the sandbags from the exhaust of the M-sized motor from the initial flight.

Flat steel plate with welded bolt
Flat steel plate added to the 1515 launch rail base for greater anchorage

A flat steel plate with a threaded rod welded to the center was connected to the bottom of the 1515 rail launcher to allow for more weight to the base and allow for more cinder blocks to be added for even more stability. New adjustable feet were added to the existing four threaded holes at the far points of the legs. Eyebolts were also bought to screw into the 3/4-10 holes in the pad to strap the base down if necessary.

The 1515 rail launcher with its new anchor plate held down by cinder blocks.

SECOND FLIGHT OF THE HAWK

The December 17th launch event was primarily for the second flight of Keith Yoerg’s massive 14-foot long, 8-inch diameter Jumbo Dark Star rocket made by Wildman Rocketry with a 98mm Cesaroni N2600 Skidmark motor. The launch was held on Friday to coincide with the anniversary of the Wright Brothers first flight..

The payload tube of the Hawk being prepared for launch on 12/17/2021.

The payload was something very special to the Yoerg family and to American aviation history. The payload was a few squares of cotton fabric from the right wing of the original Wright Flyer aircraft that made aviation history. This cloth was the actual material that flew in 1903.

An authenticated piece of American aviation history flies on the Hawk from the RRS MTA.

A similar piece of the cotton fabric used in the Wright Flyer was sent with the Mars Ingenuity helicopter aboard the Mars 2020 mission being part of the first aircraft flown on a foreign world.

Mars Ingenuity helicopter at Jezero Crater on the surface of the Red Planet in April 2021

It was amazing to fly a similar piece of history at our humble launch site for our members to enjoy on the anniversary of manned flight.

After securing the payload and verifying the recovery systems were in proper working order, the Hawk was taken to the launch pad and erected for flight.

The Hawk slid into the 1515 extrusion rail by its rail buttons.
Manually erecting the Hawk took several people to carefully raise and push the stopping pin once the rail was near vertical.
Keith checking out the wireless data system.
Dimitri connects the igniter circuit into the society’s new Cobra wireless firing system
Keith Yoerg and Xavier Marshall of the RRS pose with the Hawk before its second flight on the Wright Brothers anniversary.

Before the countdown, Keith gave a very moving speech with his mother, Janette Davis, present in the observation bunker.

118 years ago today, on the sandy windswept dunes of Kitty Hawk, North Carolina, my Great-Great Granduncles Orville and Wilbur Wright achieved the first powered, heavier-than-air flight of a manned aircraft. A few small pieces of fabric from that historic airplane are ready to take flight again today, from the sands of the Mojave Desert, aboard ”The Hawk” an 8-inch diameter 14-foot fall rocket Honoring Aviation, the Wrights, and Kinetics. In 1903, this fabric reached a max altitude of 10 feet at a max speed of 10 feet per second. Today, that same fabric is expected to reach an altitude of over 7,000 feet with a max speed of 791 feet per second (or Mach 0.7).

We’re now ready to start the countdown. The sky is clear, the road is clear.

Flight 2 of “The Hawk” is launching in 5… 4… 3… 2… 1…

Rail-mounted camera caught a few frames before the N-motor destroyed the lens.

The second flight of the Hawk was close to predictions reaching over 7,800 feet in altitude and 742 feet per second. The Hawk with its drogue and main parachutes working properly was fully recovered. Keith got telemetry data and provided screenshots of the results below.

Telemetry data from the second flight of the Hawk on 12-17-2021

Beckie Timohovich was a big help in the recovery efforts and bringing back the hardware to the launch site. She also makes really good Alaskan caribou chili which we all got to enjoy at lunch in the Dosa Building.

The ratcheting extraction tool for removing alphas from the ground.
The Hawk returned safely to the ground with the historical payload intact. Wireless and onboard data was recorded and video footage from the ground and on the vehicle was recorded.

The 1515 rail launcher with its heavier base worked well and did not shift although the straps were singed by the hot exhaust and seemed to be superfluous. The parachute system on the Hawk deployed well and brought the vehicle down in tact. Most importantly, the family heirloom flown as a payload was returned to safekeeping.

The 1515 rail after launching the Hawk. Unfazed and ready for another pounding from Wolfram’s K-sized booster motor

Keith is considering his next flight of the Hawk. One idea is to fly an even larger motor if an O-sized motor will fit in the existing 98mm mount. The goal being to go faster and break the speed of sound and fly even higher. Keith was also pondering adding a second stage to the Hawk. We hope to learn his next plan in the new year as we hope to have another launch event in January 2022.

TWO MICROGRAIN ALPHA ROCKETS

We flew two alpha micrograin rockets. One by Keith Yoerg, one by Dimitri Timohovich. Each had a payload built by John Krell. These were the first zinc-sulfur rockets to be loaded and flown by Keith and Dimitri which although both them have been active members of the society for years, this experience served to initiate them into the RRS.

Dimitri was first to load his blue nose-to-red finned rocket and fire it while Wolfram Blume completed his assembly and preparations for the second flight of the Gas Guzzler two-stage rocket with a water ballasted ramjet upper stage. Keith Yoerg’s alpha with the bright pink nosecone and fins was the second of two alpha flights, Like with the Hawk before it, the RRS used our Cobra wireless firing system with the alpha rockets.

Dimitri Timohovich loads the powdered micrograin into the propellant tube using gentle vibration to release any air pockets.
Keith finished with the loading of powdered propellant, installs the nozzle into his alpha.

https://www.cobrafiringsystems.com

Keith edited the footage of both alpha flights into one compilation on YouTube. See link below:

John Krell’s Adalogger design custom built for the tight confines and high acceleration of Keith’s RRS standard alpha.
Keith prepares to load his alpha into the box rails.
Still capture of Keith’s alpha streaking nearly straight up in nearly calm winds that day.
Keith Yoerg’s first alpha rocket.

A few days after the MTA launch event, John reported a summary of the results from the two different instrumentation payloads. His emails are paraphrased below.

On 12/17/2021, two Alpha rockets were launched. Both were instrumented with high speed flight computers. Dmitri’s Alpha (blue nosecone) carried an original Alpha Datalogger on it’s third flight and Keith’s Alpha (pink nosecone) carried a newer Adalogger design on it’s second flight.

John Krell had two data logger designs. the original data logger design was flown on Dimitri’s alpha.

The bad news first. The Adalogger SD card socket broke during its first launch. I did not catch this issue prior to this launch. The SD card fell out of its socket during the initial acceleration and no flight data was recorded from Keith’s alpha, The next design update will include a nylon post to prevent SD card ejection. Keith’s Alpha also incorporated a semi-soft shock absorption mounting. It didn’t work as well as planned, but it does show potential with two modifications. Damage to the Adalogger system was minimal and repairable. 

9-volt battery mounted in the aluminum nosecone of Dimitri’s RRS alpha.

Dmitri’s Alpha produced significant new data during the burn for a micrograin rocket. The thrust was relatively smooth and constant compared to the previous three Alpha launches that carried flight computers and returned data. Absent were the large acceleration bursts during the burn. (See attached graph)

Acceleration plot of Dimitri’s alpha flight.

Also recorded was the impact. The impact duration was measured at 16 milliseconds. This is the shortest impact duration recorded for an Alpha. A prior impact duration of 18 milliseconds produced a deceleration of 716 G’s. This impact deceleration should exceed that value.

Further analysis of the data is required to determine a value. A picture of Dmitri’s rocket in the ground prior to extraction will be helpful.   (Photo was later provided.)    

Motor burn duration           0.408 seconds

Maximum Acceleration       103.95 G’s at 0.304 seconds

Maximum Velocity               676 ft/sec, Mach 0.6 based on integrated accelerometer readings  

Altitude at Burnout              ~138 ft    

Maximum Altitude                4,307 ft AGL by barometric readings

Terminal Velocity                  463 ft/sec, Mach 0.411  based on barometric readings

My video records of Keith’s Alpha show a shorter burn duration equating to a higher acceleration and velocity. The altitude should also be higher with the shorter down range distance. 

Dimitri’s alpha with its red paint at the aft body coming off from the intense heat of the micrograin burn. Dimitri’s rocket was found significantly further downrange than Keith’s but on the same heading

The still pictures at the end furnished the information necessary to estimate the deceleration at impact. Keith’s alpha’s penetration depth of approximately 3 feet 10 inches correlates to a deceleration rate of 680 to 720 G’s in a span of 18 to 20 milliseconds. Dimitri’s Alpha penetrated approximately 3 ft 8 inches into the ground in 16 milliseconds equating to ~900 G deceleration rate. Wow!!! 

The main objective was to give all of our active members experience with micrograin rocketry. Although rarely practiced outside of the society, it is considered to be something of a rite of passage and also serves as valid experience with the unlimited category of rocketry. This event gave Dimitri and Keith this experience which will help them as they advance as pyrotechnic operators.

SECOND FLIGHT OF THE GAS GUZZLER RAMJET

Wolfram Blume brought his second build of the Gas Guzzler rocket to the MTA for a December test flight. The same booster section with an Aerotech K-motor was flown. The ramjet was rebuilt and was flying a 3/4 load of water in the gasoline tank to have a representative payload weight including any possible sloshing that might occur.

Wilbur Owens discusses the ramjet operation with Wolfram Blume. This forward view is without the forward cowl. In the background is a graduated cylinder for precisely metering the fuel load into the ramjet.
The forward end of the ramjet with its annular cowl and forward spike as it nears final assembly.
The Gas Guzzler booster stage design remained the same for this second flight from the MTA.
Wolfram holds the lower half of his ramjet ready for final assembly and stacking of the two stages.
Wolfram carefully walked the ramjet upper stage to mate with the booster stage already on the launch rail.
Wolfram Blume and John Krell examine the Gas Guzzler on the 1515 launch rail before its second flight.
The Gas Guzzler sits side-saddled in the 1515 rail launcher to allow proper clearance of the fins.
The Gas Guzzler lept straight and clean from the 1515 rails in its booster flight.

From the ground, it was clear that the booster flew straight and stage separation had taken place. The booster parachute ripped loose. The ramjet came down only under its drogue chute and the hard landing damaged the upper stage enough to warrant a complete rebuild.

Clean stage separation was evident, but the booster parachute ripped loose.

Wolfram spent several days after the launch event looking at the remains of Gas Guzzler. A few things are known so far:

The addition of 1.14 kilograms of ballast water did not cause any problems. The two stages – both separately and together – were still stable in flight. Also the stage separation worked.

After separation, the booster came apart at apogee into two pieces. It is an easy fix as a bulkhead blew out and only needs to be better reinforced against the loads. A recent addition of a GPS tracker to the second flight of the booster worked.

The ramjet lost electrical power at apogee. The reason was found and will be repaired.  The power failure meant that the GPS tracking stopped at apogee which is a serious problem. Wolfram is considering adding a backup GPS tracker to the ramjet with a separate power supply.

Based on telemetry, the deceleration seen after stage separation gave the drag coefficient (Cd) on the ramjet at 0.25. The accuracy of this calculation is about 10% based on the acceleration readings which is fairly good all things considered.

drag force = Cd * velocity-squared * air-density

The thrust also scales with the square of velocity and that gives the minimum velocity when thrust minus drag exceeds weight to be about 656 feet per second (200 m/sec).  This is the minimum velocity which the booster must supply at burnout.

For this flight using the K-motor in the booster, with the water ballast, the maximum velocity was 574 feet per second (175 m/sec). The ramjet reached an apogee of 3,800 feet AGL (above ground level). The booster pushing the ramjet reached an apogee of 3,100 feet AGL. Maximum acceleration under boost phase was 6 G’s. The ramjet was flown without fuel, only an equivalent weight of water instead of gasoline.

The next build of the Gas Guzzler will have a larger booster which will hold an L-sized motor.

In the 12-17-2021 flight, the ramjet’s drogue parachute deployed correctly but the main chute did not. This seems to have been caused by the drogue chute being too small. Rockets with dual-deployment parachute recovery systems typically split the rocket in two places with the drogue ejecting forward and the main ejecting backwards. It is a good, reliable system but it cannot be used in the Gas Guzzler design because you cannot split the ramjet in the middle. Both of the parachutes must deploy from the front. The recovery system design requires the drogue to pull the main out of the ramjet at 1,000 feet.  Wolfram developed this system on prior rocket with launches at ROC in Lucerne Valley and it has worked the last three launches. Wolfram is confident that it will work in the next flight of the ramjet, too.

Damaged fragments of the ramjet recovered downrange after the second launch of the Gas Guzzler.

The air flow measured inside the ramjet during the second flight on 12-17-2021 was within the range of an air blower system at Wolfram’s workshop that had considered using to static fire the ramjet with an operational burner. However, he is not comfortable with trying the main burner at his workshop, but testing the flameholder and its igniter is OK. Thus, a static test of a fueled ramjet coupled with an air blower system is being considered.

Going forward, once the ramjet is rebuilt, Wolfram would like to verify the performance of the igniter and flameholder over the full range of the air blower’s speeds in a static fire setup at the MTA. In this testing, he also wants to work on how quickly the flameholder ignites to avoid losing a lot of forward speed after stage separation.

Wolfram will rebuild the ramjet as quickly as possible and could be ready for another launch in February 2022. He would like to do another booster-only flight from the MTA to verify the fixes on that stage. If successful, then the next launch will try a flight with a short ramjet burn using roughly 5 seconds of gasoline fuel.

The society will peer-review the work done so far and find the best way to proceed. Wolfram is still evaluating the data and may have an update to this firing report later.

TESTING OF A GERB AS A LIQUID ROCKET ENGINE IGNITER

Dimitri and I have overseen a few recent liquid rocket engine static fires at the RRS MTA. Although there have not been any ignition problems, we had discussed different approaches to getting a safe and reliable start.

Liquid rocket engines sometimes have problems with achieving reliable ignition. Failure to ignite the cold mixture of propellants due to lack of sufficient energy or outright failure to light can create a serious fire or explosion hazard. One of the simplest approaches is to use a sufficiently energetic pyrotechnic device mounted in the engine throat from the aft side. Visible indication of the igniter firing should be confirmed prior to opening the propellant valves and releasing the stored pressurant gas.

There are a few different pyrotechnic devices that are good for this task such as lances and gerbs. Both require a special license to get. Dimitri, who has such a license and happened to have a couple gerbs that we could try. Lances have been used in prior liquid rocket engine firings and vehicle launches with success.

https://en.wikipedia.org/wiki/Gerb_(pyrotechnic)

https://en.wikipedia.org/wiki/Pyrotechnics

At this event, we decided to test a gerb to see if it would be appropriate to try in lighting a liquid rocket engine. We secured one to the top of the alpha box rail and fired it to examine the plume,

A gerb is a pyrotechnic device used in firework displays.
Simple schematic of a liquid bipropellant rocket engine with an external igniter system
The gerb was fired to determine if it would make a suitable igniter for a liquid rocket engine.

Our impression of the gerb operation was favorable in terms of its 20-second firing duration, but it seemed that a smaller gerb size might be sufficient. Smaller gerb sizes are available. There is also the long-term consideration of having these available for liquid rocket testing which would require a storage magazine. Other less complicated means should be explored.

IN CLOSING

Several of the attendees stayed behind to clean up the MTA and relax in the Dosa Building. This was the last launch event for our outgoing president, Osvaldo Tarditti, who has faithfully served the society for many years with his time, skills and leadership. We enjoyed the sunset on a mild and nearly calm winded day. It was a fine end to a great day at the MTA and what was our last event of 2021.

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