MTA launch event, 2021-01-09

by the Reaction Research Society

The Reaction Research Society held its first launch event of the new year on Saturday, January 9, 2021.  Dave Nordling was the pyro-op in charge.  We had a couple rockets prepared and some maintenance work we wanted to continue.  Dmitri Timohovich brought his whole family to the event and we enjoyed grilled burgers there at the Mojave Test Area.  The January winds were light and cool that day.  It was a good day for launch.

Bill Inman enjoys a burger in the George Dosa Building
Everyone relaxing for a short lunch before getting to launch.

Wolfram Blume brought his two-stage rocket, the Gas Guzzler.  His ramjet upper stage was rebuilt from last year’s unfortunate breakage when dropped during loading on the launch rail last year.  3D-printed plastic parts can sometimes be very brittle and care must be taken.

The 1515 launch rail was put into position with some help from Bill Inman and a few others.  Bill Inman is still working on his solar tracker for his latest iteration of the Scalded Cat.  He made the trip from Carson City to the Mojave Test Area to help others with operations and we were very thankful.

Wolfram was able to mount his booster stage on the rails and carefully erect the launcher.  The booster uses a commercial solid motor, an Aerotech “K” motor.  

Wolfram cleans the 1515 rail at the RRS MTA in preparation for mounting the booster
Wolfram’s booster sits on the launch rail

The ramjet for this first flight was loaded with water to simulate the weight, but would not be fired.  The primary goal was to demonstrate the staging and recovery systems powered only by the booster.  Wolfram went back to the loading area to complete the preparations of the upper stage. During a system checkout, the parachute deployment charge fired.  After some careful examination, the source of the problem seemed to be related to errant software commands.  Wolfram aborted his launch attempt and returned with his rocket stages for further examination back in Los Angeles.  Although the charges could be reloaded, he could not be certain that an early parachute deployment would occur and wreck his vehicle during flight.

The Gas Guzzler upper stage ramjet

Dmitri Timohovich and Waldo Stakes worked on completing the welding of the new steel plate on the vertical test stand. This plate on the vertical test stand was damaged during a test failure many years back and late last year was finally cut out and the space grinded to fit a replacement plate.  Unfortunately, the stick welding system would require a different type of welder and a more powerful source to drop a reliable weld.  The welding of the plate will be reattempted at the next event.

With the grinding complete, the plate is fitted and ready to be welded in place

The second launch of the day would be Dave Nordling’s nitrous oxide hybrid rocket.  This 38mm H-sized commercial hybrid motor kit from Contrails Rocketry (H-222 model) had a modified igniter and was mounted in a new 4-inch body made by Larry Hoffing. The prior launch attempt had issues with severing the nylon plastic filling line so the ignition energy was increased with small bit of composite solid propellant ignited by an electric match.

Several minor problems occurred during launch preparations. The nitrous bottle and manifold filling system was working well but the electrical control box failed during tests.  After some discussion, the defective switch box was removed and we were able to fire and get a clean launch

Dave Nordling leans against the old blockhouse with the second build of the hybrid rocket waiting for launch
The hybrid sits on the 1010 launch rail

We repacked the motor before launch and adjusted the vent tube to be more visible. The filling of the rocket went quickly and smoothly, only about 20 seconds before the white stream of liquid could be seen. The filling was stopped and with a short five-count and the rocket was fired. The rocket came off the rails quickly and it seemed that the modified igniter worked. The big problem was the parachute recovery switch wasn’t turned on before launch. This simple oversight would mean a rebuild would be necessary.

The simplest error can lead to sad results.

The rocket was recovered on the north end of the MTA site. It only seemed to reach about 300 feet of altitude. Unfortunately the ballistic landing broke both stages and the internal motor mounts and a complete rebuild is necessary. The motor case was parts were in tact and so it was extracted and will be reloaded,

The hybrid motor seems to arc to the north against wind.

Beckie Timohovich recorded the hybrid flight on her phone, The rocket seemed to immediately curve to the north off the rails opposite of the wind. It seems that the nylon fill line might be still holding fast despite the added solid propellant charge. The 3/16-inch nylon plastic line being strong enough to hold back the 900 psi nitrous pressure, it also poses a challenge to cut cleanly from the ignition charge. A static firing of the motor will be done next to get a better look at how well the fill line severs and measure the thrust curve directly..

The remnant of the fill line from within the hybrid after firing. The end looks smoothly extruded.

After recovering the hybrid rocket and putting away the equipment, we flew a water rocket for Dmitri’s young son. Although very simple, these things are very fun.

Max Timohovich holds the water rocket fired several times at the end of the afternoon.

The event was a partial success and there is more work to be done on our facilities including adding a new toilet facility at our site and welding in the plate on the vertical test stand. The next hybrid rocket launch may be a couple months away, but Bill Inman may have his next design of his solar heated steam rocket ready for launch af fhe MTA in a few weeks. He had his first successful flight in the Nevada desert just before Christmas. He is getting ready for a flight from the RRS MTA.

Bill Inman has his first successful flight of his solar-powered steam rocket on 12/22/2020

Wolfram seemed confident that he too might be ready to try his first launch of the Gas Guzzler at about that same time. If the next launch event occurs before the next monthly meeting on February 12, 2021, the announcement will come through the society email list.

The sun sets at the RRS MTA after a good day.

October 2020 virtual meeting

by the Reaction Research Society

The RRS held it’s monthly meeting by teleconference on October 9th at our usual starting time of 7:30pm. We had a few members calling in from out-of-state. We had a few new topics to cover.

Some of the attendees to the October 2020 monthly meeting


We held a work event at the Mojave Test Area on October 3rd which was very successful despite higher temperatures for that autumn Saturday. We cleared a lot of tumbleweeds, mended the barbed wire fence at our front gate, painted the metal window gratings on the front of the Dosa Building and even cleared off the decks of the large vertical test stand. We had a lot of great help and we hope to continue making these site improvements to make our facility more attractive and useful.

The large vertical test stand at the RRS MTA after some clearing.

We agreed to meet at the MTA again on November 7th which will coincide with a static fire test of USC’s Rocket Propulsion Lab latest multi-grain solid motor design. We will also attempt to remove and replace a bent panel on the vertical thrust stand. The nitrous oxide hybrid rocket by Dave Nordling, Larry Hoffing and Osvaldo Tarditti is also ready for launching. If there are other member projects that are ready we will add those to the event and notify the pyro-op in charge.


Liquid rocket projects have become more popular recently and some have started within the RRS.

Loyola-Marymount University (LMU) in Marina del Rey started a capstone project for their upper classmen in their undergraduate aerospace engineering program to design and build a large liquid rocket. The LMU Lion project was inspired by the FAR-MARS competition. Dave Nordling has been supporting the early design work on behalf of the RRS starting early this calendar year prior to the pandemic restrictions ending in-person meetings. LMU has restarted the project with the new academic year with a series of specialized coursework and short presentations on topics from experts around the industry. Dave was glad to present the history and capabilities of the RRS. The presentation was well received and LMU has looked at using our vertical test stand when they get their first liquid rockets systems ready for test.

Loyola Marymount Aerospace Research Society

The Compton Comet project at Tomorrow’s Aeronautical Museum has been restarted with RRS members, Waldo Stakes, Kent Schwitkis and Dave Nordling. The Compton Comet is a liquid rocket to be built, tested and flown at the RRS. It is a larger vehicle design which has several parts built and will use a surplus XLR11 single-chamber fueled by LOX and a 75% ethanol-water blend, It is a very ambitious project for the Compton College STEM students but it will provide an excellent means of learning practical skills.

Engine section built from a surplus tailcone and ethanol-LOX engine sits on the workbench

UCLA is continuing Project Ares for this next academic year. Last year’s liquid rocket vehicle design was in its final preparations for a Spring 2020 launch at FAR until the pandemic closed campuses around the country including the UCLA Lab. UCLA invited a few RRS members to attend their preliminary design review by teleconference. They are proceeding with several design improvements from last year’s vehicle design and when their laboratory access is restored under carefully regulated conditions, they hope to have another static fire at the RRS and flight from FAR next spring.

Thr Rocket Project at UCLA

Richard Garcia had started a design for a small liquid fueled rocket that would be easier to build and serve as the basis for a common or standard design for society members wanting to test and fly a liquid rocket at reasonable cost. Propellants are ethanol and liquid oxygen. The design has features proven from past successful liquid motor testing at the RRS MTA. The first prototype of the small 125 lbf motor is in build now. After successful demonstrations of the motor in hot-fire, the vehicle will be built.

Illustration of the RRS standard liquid rocket concept

There is a rocket hangar space opening up at the Compton/Woodley Airport which RRS members will soon have access. It has been a goal to have a work space within the city centrally located for most of our members. Operations at the rocket hangar will be limited to construction activities and small-scale pressure tests and cold flow operations, but it will offer our members a greater convenience for those with limited working space in their homes. Contact Wilbur Owens and Xavier Marshall for details. Social distancing and mask protocols would apply.


Fires are one of the greatest risks that come with amateur rocketry. At the behest of several members we have been discussing way of better preparing to fight fires from our site. The roughly one dozen pressurized water containers we have in our storage container are filled and made ready at every event. These have been useful for containing any fires starting at the pads. The RRS is looking at storing large quantities of water at the MTA. We’re also looking at trailer mounted water tanks that could be pulled by a small all-terrain vehicle (ATV) with a motorized pump spray system. These are commonly found in agricultural locations and would be an excellent addition to help limit the propagation of downrange fires until county resources can arrive.

An example of a 200-300 gallon water tank with a motorized pump system


New restroom facility designs have been discussed over this summer. Concepts have been discussed with contractors and firm cost proposals are being prepared. Issues like cost and permits are important concerns. The society last year approved this facility upgrade project as the top priority.

One of several concepts for a new restroom facility at the RRS MTA under discussion


Next meeting teleconference will be held on November 13th. After appointing an election chairman, we will be holding nominations for executive council positions at the meeting. Administrative members of society are encouraged to participate as we select our next year’s leadership. Active membership is also required so be certain to pay your dues if you haven’t all year.

If there are any questions or comments, please contact me RRS secretary. You can also follow the RRS on Facebook and on Instagram.

MTA launch, 2020-07-25

by Dave Nordling, RRS.ORG

On July 25, 2020, the Reaction Research Society held its first launch event at the RRS MTA since the start of the pandemic. Our pyrotechnic operator in charge that day was our society president, Osvaldo Tarditti. I was his backup. We also had Jim Gross come out for the event who has been our pyro-op in charge at many of these events.

We observed social distancing as best as we could and everyone was wearing a mask. Protective equipment is normally required for loading operations and keeping our people spread apart only makes good sense. The heat (107 F) was significant but everyone was largely prepared to endure the exhausting environment. We had a few glitches in the launch process which can happen at any event. It is times like these that make patience and planning very valuable.

We held a short safety briefing before beginning launch operations. I reviewed the natural and man-made hazards at the MTA, underscored the importance of hydration, the buddy system and montioring each other and ourselves for hest exhaustion. We had a lower turnout as this was a private society event and with the heat we sought to run through the micrograin launches in one straight series holding the hybrid rocket flight for last. After the safety briefing, Larry performed a propellant burn demonstrstion then we adjourned to the observation bunker while the pyro-op’s began to ready the micrograin rockets in the rack. John Krell assisted me with the rack loading and arming process.

We had four micrograin rockets and the hybrid rocket for this launch event. There were three alpha rockets with slight differences in their design. John Krell had built three avionics payloads, one for each, to capture the trajectory data (acceleration and barometric pressure) so that an apt comparison could be made. We also had an avionics package and recovery sytem (parachute) built into the beta by Jerremy Hoffing, son of Larry Hoffing. The hybrid rocket would be last in the series,

Bill Inman surveys the upper half of his launch rail made from electrical conduit for the three-finned steam rocket he built.

Bill Inman came to the launch event to both spectate the launch of the micrograin and hybrid rockets and also examine portions of his launch rail unit from his Scalded Cat steam rocket project. He has already begun planning a newer steam rocket design.

Bill Inman captures a launch from his cell phone camera from the MTa observation bunker.


This segment talks about the three alphas we built and flew to compare two design changes. The three designs were:

  • standard alpha with three-foot propellant tube, plain carbon steel nozzle
  • standard alpha with three-foot propellant tube. ceramic coated nozzle
  • longer alpha with four-foot propellant tube, ceramic coated nozzle

Among these three designs, we were examining the effect of the ceramic coated nozzles which used a proprietary coating process used on automotive engine pistons and exhaust pipe interiors in the racing industry. Specialized Coatings was the company providing the service which we have used before. The coating was proven in a prior alpha flight in 2017, but the nozzle was misplaced and lost after photos were taken at the event. A repeat test was warranted to not only provide photographic evidence but also to cut-up a nozzle to see how the coating survived. It is likely that a ceramic coated nozzle can survive multiple firings before erosion sets in.

Converging part of an alpha nozzle with the ceramic coating
Diverging part of the alpha nozzle with a ceramic coating.

The other variable explored was to change the length of the propellant tube and thus increasing the propellant available. Past projects have explored using longer propellant tubes, but this project would bring flight data for direct comparison. To achieve maximum altitude, a second ceramic coated nozzle was used. Just based on the time of flight observed from the observation bunker, the four foot alpha remained aloft for at least four more seconds. John Krell took some video like a few others did. We may be able to estimate the trajectories if we fail to recover the data from one or all of the alphas.

The four foot alpha rocket payload is being loaded.
The four foot alpha rocket sits in the alpha rails with the beta rocket in its own rail launcher behind it.


The beta rocket used at the launch event had a recovered nozzle which had some minor erosion. This was sufficient for this flight. The two features were the parachute recovery system and the avionics package to record altitude data.

Beta rocket with a classic Dosa-style fin can.

The beta was the first micrograin rocket ready for flight and thus it was loaded into the box rails built for the beta. This beta design differed from the standard design by having a straight coupler meaning that the aluminum payload tube was the 2.0-inch diameter as the 2.0-inch DOM steel propellant tube. Because of cost, betas are produced in smaller and less frequent batches. This sometimes leads to more variations in the design. With a little more part production, we can achieve greater consistency between betas.

The used beta nozzle sits next to the Dosa-style fin can

The typical aluminum coupler design flares out to a 2.5-inch aluminum payload tube. The standard design better fits the box rail launcher which was made with a 2.5-inch bore. The standard payload tube size would have offered more room for packaging the recovery system. Nonetheless, Jeremy was able to fit everything together and the beta propellant tube was filled and made ready.

The 2.0-inch rocket did lay properly inside of the quad-rail launcher, but the sloppy fit was a little concerning. We had considered using a sabot to fill in the gap, but no practical solution could be made. The solid steel rails would contain the rocket but the concern was whether the avionics switch would get bumped into the off-position. To avoid this, a small block of wood was used to lift the beta high enough to clear the switch near the top of the payload.

The ignition wiring of the beta with the dual igniters is rechecked by Osvaldo. The beta is propped up on a chunk of wood to clear the payload switch. There was a concern that it could accidentally switch off.

The first launch attempts resulted in no firing. After re-checking the cabling and my hookups, no error was found. Second attempt also had the same negative result. To expedite the launch process we proceeded with the alpha launches.

The beta under repair in the old blockhouse.
Two burst disks with two electric matches.

After the alphas flew, we re-tried the beta rocket with a dual-igniter for redundancy, the first electric match was found to be defective. This time after some initial trouble with the battery, on the third attempt we got ignition.

Still capture of the beta rocket at the 7/25/2020 launch event
A massive smoke plume from the beta just a fraction of a second after ignition


A new rocket body was built to hold the same Contrails H222 nitrous oxide hybrid motor flown earlier. this year. Larry Hoffing did a lot of work building a new rocket body from scratch. It’s boat tail was fitted to accept the 16-inch long, 38mm casing of the Contrails H222 model. Osvaldo built in the parachute recovery system and all parts of the rocket fit well together at the RRS MTA. I changed the location of the vent tube and routed the line to the outside trimming the excess away once the rocket was vertical and captured in the 1010 rail. A lot of this preparation was documented on the RRS Instagram page.

The second fllight of the hybrid rocket sits on the 1010 rail.
The hybrid rocket sits on the 1010 rail positioned for flight

The Contrails H222 motor is a very simple design made for reloading and re-use. The designs are built to common metric standards used in model rocketry. Using the smallest size, 38mm, for a first hybrid project made sense as we would learn the practical things necessary for a successful launch. It also was a size very close to the micrograin rockets that the RRS commonly uses.

The Contrails H222 motor slipped into the rocket body awaiting the retaining ring. The igniter is taped against the nylon filling line going up the nozzle, fuel grain and up to the floating injector fitting.

The Contrails design is very simple and easy to assemble with the right tools and lubricants. The interior of the 16-inch long motor is divided into two parts, one for filling with nitrous oxide liquid supplied under pressure and the other holds the inert plastic reloadable fuel propellant grains and a graphite nozzle. The two volumes are separated by a dual O-ring sealed piston called the floating injector.

Cross-sectional illustration of the Contrails hybrid rocket motor

The motor uses a snap-ring retention method for securing the graphite nozzle plug in the aft and another snap ring is used to keep the vented top plug in place. The internal pressure of the nitrous oxide liquid holds the floating injector down against the fuel grain. The injector consists of a stainless steel Parker push-to-connect plastic tube fitting. The ignier is designed to break the filling line inside of the motor releasing the flow of nitrous oxide and providing ignition nergy to start the combustion of the plastic fuel grain in the presence of newly streaming oxidizer flow. It is a very simple and impressive system. Contrails also sells kits and replacement parts to replace those that wear out.

Top bulkhead fitting with an orificed vent line in the top, snap ring is installed and removed with a special tool.

Last launch attempt successfully demonstrated the motor assembly, motor integration into our first rocket body and loading process. The remote actuation of the nitrous filling line and separate electric ignition circuit required a two-channel firing rig which operated well as expected. The flaw in the first aunch was failing to quickly and cleanly sever the thick-walled nylon fill line.

The floating injector with the 3/16-inch nylon fill line inserted. The Parker brand push-to-connect fittings are used for this application.

The nitrous bottle was recharged with liquid and secured to an I-beam. The valve manifold was attached and after a quick tightening was free of leaks. We secured the electrical and fluid connections to the rocket and ran our control lines back to the old blockhouse with all of our observers in the safety of the observation bunker. Osvaldo and I conducted all operations with care. Then the first problem struck.

Nitrous bottle with the filling manifold

We couldn’t get the fill solenoid to open. This was first thought to be the battery. In past summer events the heat can degrade the battery. We had several no-fire conditions which led us to suspect the battery health. For the beta, the fault was a broken lead on the electric match. Running a voltmeter showed a little weakness of the battery but 12-volts was showing on the needle. We moved one of the cars closer to the blockhouse to use its battery but the solenoid still wouldn’t open. Given, the late hour in the peak of the afternoon, we scrubbed the launch attempt and safed and disconnected the fluid and electrical system.

Nitrous oxide bottle courtesy of Nitrous Supply Inc. in Huntington Beach. The fill-drain system with remote operated solenoid valve.

The bottle pressure was reading very high that day and although the vessel and plumbing is amply rated for the 1400 psi reading on the gauge. By weight, the bottle wasn’t overfilled, but the heat of the day certainly brought the pressure up. The solenoid valve was bought as part of an assembly sold by a different supplier. With no labelling or marking on the solenoid, there is nothing to identify the manufacturer or model number. A couple emails were sent to the seller but no information on the valve make and model has been given. The internal design and operating limitations of this 12 VDC normally closed solenoid valva is unknown but it is possible that the high pressure against the seat was too much for the solenoid to overcome. Chilling the bottle or simply venting the bottle to lower the pressure might have helped. More tests of the solenoid valve will be done to verify its functions and perhaps some careful disaasembly of the valve may reveal markings to identify it. We are also considering building our own simple solenoid valve fill and drain assembly once the right parts can be specified.


It was a long day but very worthwhile. We hope to have another launch event soon. The results of the day’s events will be discussed at the August 14, 2020, monthly meeting which will be held by teleconference.

Lovking up the gate at the end of the day.