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.

THREE ALPHAS

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.

BETA WITH RECOVERY SYSTEM

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

SECOND FLIGHT OF THE HYBRID ROCKET

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.

IN CLOSING

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.

July 2020 Meeting – *Virtual Only*

by Dave Nordling, Reaction Research Society, edited by Andrew Cortopassi, Secretary, Reaction Research Society

We held our monthly meeting of the Reaction Research Society (RRS) by teleconference on Friday, July 12, 2020.  Our treasurer, Chris Lujan, and our vice president, Frank Miuccio, called the meeting to order.

Since June 2020, we have made the teleconference feature a permanent part of all future meetings even after we ultimately return to in-person meetings at the Ken Nakaoka Community Center in Gardena.  Teleconferencing has allowed the RRS to better unite our far-flung membership from around the Los Angeles and neighboring areas and even those on travel.

Due to the restrictions imposed by the continuing pandemic, the next RRS symposium will be held early next year in 2021. This was decided by the membership at the prior June 12 meeting.  Frank has not been able to schedule a date, but the society plans to hold the event a little earlier in the year (March 2021) than what was done in the prior events.  We remain optimistic that we can have a full exhibition and speaker series while adopting appropriate precautions.

Osvaldo, Larry and Dave became licensed pyrotechnic operators in rocketry for the society as of one year ago.  By law, this means that with the renewal of their annual license they can provide reference letters, wholly at their discretion, to other members seeking to pursue their own application to becoming a pyro-op.  The society roster of pyro-op’s is growing and this is good for both the society and amateur rocketry in general.  We have enjoyed the support of the California State Fire Marshal’s Office (CALFIRE) for many years and this has been helpful as we educate a new class of members in becoming responsible members of our hobby.  The more people know the law, the safer our community will be and the stronger our voice with the state becomes.

Dave Nordling announced his intent to become a rockets first-class pyro-op and will begin preparing his application.  Jim Gross, one of our pyro-op’s at the society offered his advice to all seeking their license that it is an important responsibility to uphold the law and protect the safety of everyone above all else.  The state exams are geared towards verifying a licensee understands the numerous hazards and safety concerns in addition to the state licensing processes and reporting requirements.   Every pyro-op must personally vouch for the person they are recommending.  This is often done by mentoring, apprenticeship or some form of repeated skills demonstration before the licensed pyro-op to show the applicant is knowledgeable, confident, mindful and vigilant in the safe handling of all operations and the people around them.  It is at the sole discretion of each pyro-op what their standard will be.  CALFIRE is also very helpful to those having questions about the process.

Waldo Stakes is holding a memorial for Mad Mike Hughes on Saturday, July 18, at noon, at the 247 Cafe in Lucerne Valley, CA.  Some of our members expressed interest in attending to pay their respects to Mike’s family and friends.  Mad Mike was killed on February 22 this year in the last flight of his self-built steam rocket outside of Amboy, California.

The RRS will be holding a launch event at the MTA on Saturday, July 25th.  This event will be for RRS members only and will be the first launch event held since the onset of the COVID-19 pandemic in the United States in mid-March of this year.  Many have expressed their concerns in holding this event given several of or members are in at-risk categories either themselves or from within their household.  The counter-argument has been that given the wide open spaces around the MTA and the imposition of social distancing and wearing masks at all times, member safety can be maintained.  The society consensus was to proceed with the 7/25/2020 launch event.

Three micrograin alpha rockets and a beta will be launched at this 7/25/2020 event. John Krell will have built several high-speed datalogger prototypes that can fit within the tight confines of these alpha and beta aluminum payload tubes.  His earlier prototype datalogger was able to quickly and adequately sample the extremely high acceleration of an alpha at takeoff, although the 50G sensor range was exceeded across several consecutive samples.  The initial datalogger prototypes were recovered intact and could be reused.  Based on this success he will use a higher ranged accelerometer that will add greater detail to our knowledge of the micrograin rocket trajectory and provide additional data about apogee altitude and infer the rate of deceleration from impact.

Dave Nordling will also have two of the standard steel alpha nozzles with their internal flow paths ceramic coated.  This high temperature coating is used in the racing industry for piston coatings to extend their life.  A few years back this same coating from Specialized Coatings in Huntington Beach was proven on a recovered alpha nozzle showing zero erosion at the throat so we are confident of a repeated success.  Also, one of the alphas will use a longer propellant tube (4-foot) than what is the standard (3-foot).  We hope John’s dataloggers are able to capture good data from each of the alpha flights for valid comparison.  Also, capturing the trajectory of a beta rocket will be another important addition to the society knowledge base.

We discussed some of the history of different micrograin rocket experiments throughout the many decades of the society by several members.  Jim Gross offered to summarize his recollection of the many micrograin experiences into an article for RRS.ORG which will be posted soon we hope.

Larry, Dave and Osvaldo have made a second rocket ready for the Contrails H222 hybrid motor.  The nitrous oxide bottle should be re-charged and weighed in preparation for the launch event.  The recovery system has been added and reloading of the aluminum motor housing with an ignition system and hybrid fuel grain is the only step remaining.  Improvement to the igniter system was necessary after observing the high speed camera footage which will attempt to better sever the nylon filling line at the floating injector.  It was also recommended to add a small amount of paraffin wax to the forward end of the hybrid plastic fuel grain in an attempt to start the burn a little hotter when the nitrous oxide starts to flow.  Hybrid motors have been used successfully in model rocketry events but they have been known to be difficult to ignited and operate reliably.  It is the team’s intent share our learning with the society as we work toward success.

It was at this point, the discussion turned to oxidizers in general.  One of the earliest projects at the RRS was a rocket-grade hydrogen peroxide (H2O2) monopropellant liquid that was built and flown in the 1950’s.  Hydrogen peroxide was explored again at the society many years later in a project to re-fly a monoprop rocket system.  Recent information was gathered from Peroxychem on the properties, handling and safety precautions required with having of rocket grade hydrogen peroxide.  As expected, the cost per volume of 90% HTP was very high and likely beyond the budget of an amateur project using anything more than a gallon.  The membership felt that there wasn’t sufficient interest in restarting a peroxide project, but some kind of summary article of peroxide properties and a collection of different members experience might be interesting.

Jim Gross mentioned his past experiments with nitric acid and its hypergolic reaction with furfuryl alcohol.  Regardless of the specific oxidizer, cleanliness and material compatibility of all wetted surfaces is of paramount importance in all experiments and projects.  Many people appreciate these hazards when it comes to liquid oxygen, but may not similarly appreciate the hazards with other oxidizers like nitrous oxide and caustics like nitric acid.  All oxidizers, even sulfur, must be treated with studious care and respect.

The 2020 Constitutional Committee is still due to present their draft for society membership review and comments.  An overview presentation will hopefully be made at the next meeting in August.  Updates to the language and policies have been needed for years in order to better describe how the society operates.  Ratification by the executive council should follow once all administrative members have had a chance to make their concerns known to our society.

In closing, Wolfram gave the society an update on his gasoline-fueled ramjet project, the Gas Guzzler.  He is making improvements to the flow path to enhance mixing and will continue with his benchtop experiments and analyses.  He is making progress but will not attend the 7/25/2020 due to the extreme heat in the Mojave desert.

Jim Gross reinforced this concern for all members to protect themselves against heat exhaustion while attending the MTA event.  Air temperatures can easily exceed 110 F at the peak of the Mojave afternoon.  Bringing a cooler with ice and cold beverages is essential as is sunscreen, a hat and light desert clothing.  Even those who have adapted themselves to the desert summer must take these precautions and be mindful of the condition of others.

We adjourned after 9PM as some of our members were retiring for the night.  Our in-person meetings must contend with the community center closing at this time, but with our meetings done virtually we can enjoy the extended meeting time together.  The next meeting will be again held by teleconference on Friday, August 14th.

Please contact the RRS secretary if there are any questions or concerns.
secretary@rrs.org

All members are responsible for keeping their contact information with society up to date and staying current on their annual dues with the RRS treasurer.
treasurer@rrs.org