Tag Archives: model rockets

MTA launch event, 2021-03-20

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Dave Nordling, Reaction Research Society

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 CAT FROM 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 cable

The 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 Challenge
A 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.

In Memoriam: Brandy (Robert “Bob”) Bruce-Sharp (1953-2019)

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by Larry Hoffing, Events Coordinator, Reaction Research Society and Korey Kline (contributing)

In January 2019, Brandy (Robert “Bob”) Bruce-Sharp passed away. As reported by Mark Clark and Tripoli, Brandy went quickly from non-Hodgkin’s lymphoma. At the BALLS 28 launch this past September, Brandy and wife Abbie’s ashes were launched and spread in an Aerotech M1939 rocket.

from left to right; Robin Meredith, Jim Bornwell, Jane (Brandy’s sister), Mark Clark, Gary Rosenfield

Bob was my friend and fellow student at Los Angeles (Robert H. Goddard) Pierce College rocket club that I founded in the early 1970’s. Around this time we met a high school kid named Korey Kline, he was only fifteen at the time but already a veteran shop mechanic. His high school rocket club, inspired by the Pierce club, found a Korean War five-inch diameter HVAR rocket at a vacant military recruiting office.

Bob Bruce, Michael Gill and Larry Hoffing of the Robert H. Goddard Rocket Society of Pierce College in Los Angeles
Bob Bruce and Larry Hoffing stand at the launch rail for a row of model rockets in the 1970’s

We proceeded to convert it to a zinc-sulfur rocket which required bolting some ports of the multiport nozzle shut, adding fins, and a payload section- I think Bob’s mother sewed the parachute. I did most of the machining in the school’s metal shop while some of the welding students added the fins. I remember hauling the thing, which weighed about 40 lbs unloaded, for a show-and-tell presentation at the Pacific Rocket Society (PRS) which met at the (now defunct) Northrop Institute of Technology in El Segundo.  B. J. Humphreys was the PRS president at that time.

B.J. Humphreys, past president of the Pacific Rocket Society and builder/pilot of the first rocket-powered wheelchair
Bob Bruce and Larry Hoffing in September 1972

Bob named the rocket “Bifrost” (pronounced “BIF-roast”) which is the old Norse term for the rainbow bridge to Asgard.  Our mission was to fly Bifrost at the Mojave Test Area (MTA) near the town of Cantil, CA, where the RRS, FAR and Polaris Inc. (under the direction of Dave Crisalli) currently test. In those days the bunker was covered with telephone poles that had been trucked out by RRS member John Mariano and his cousin in the 1960’s.  There’s a pile of them still laying at the MTA to this day! Access to the site was by dune buggy. The yellow blockhouse with its ballistic glass windows still stands at the RRS MTA.

This sets the scene for the launch of the missile on a wooden home-built Bruce rack – 3 aluminum fins had been welded onto a cowling over the casing as we hadn’t realized the launch racks were built for four-fin rockets (Hint: let your new members know about the launch rack configuration ahead of time). The PRS had most of the pyro-op’s at that time.  The PRS pyro-op in charge was afraid we’d blow up the rocket and surrounding area so he made us fill the casing half way with sand. It must have weighed 80 lbs.

5, 4, 3, 2, 1, ignition! The rocket lifted off, flew a short distance, and crashed. The failure to go the distance was attributed to the multi nozzle ports, we didn’t bolt enough of them shut to build pressure. There is a photo of it flying, I gave it to my machine shop professor, and unfortunately don’t have a copy.

Bob was a consummate modeler and draftsman. He won top prize from Estes in 1972 for his remote control Space Shuttle which was a thing of beauty.

Bob Bruce wins first prize in the Estes rocket modelling competition for his space shuttle design

Bob started a rocket kit company with Korey in the mid 1970’s called California Model Rockets, a precursor to large/high power rocketry. One of my biggest regrets in life is not joining them in this endeavor. Bob and I had previously invented the largest model rocket in the world we called “The Wopper” . The California State Fire Marshal rules at the time was that model rockets had a weight limit of 1 lbm including the motor, so designing it was no easy task. We got the brilliant idea one day of enclosing foam rings and horizontal balsa slats with construction paper to create giant tubes. The biggest F-sized motor at the time was F-100’s made by Flight Systems Inc. The large model rocket flew spectacularly to about 300 feet.

Bob relocated to Arizona sometime in the 1980’s to pursue drafting, and afterward I lost touch with him. However, my memories are vivid of us mixing and testing “Blue Knight” candy fuel (sugar motors), and launching model rockets at Half (Hof) Mile Square in Fountain Valley, CA (a former air ship site) with the Westchester YMCA Rocket Club. Hof Mile was a trip. Wheeled sail cars raced around on the landing strip as we launched rockets. We’d even have to pick up the gate keys from the local base commander. It was here while looking for a rocket in the tumbleweed that I stumbled upon a huge, beautiful red fox when the area was still wild back then.

Korey remembers Bob as his earliest mentor for rocketry. “By example he taught me to think outside the box!” Korey says he was only fifteen when he met us and we (and his mother) had to drive him to the rocket club meetings. Bob also introduced Korey to B. J. Humphreys of the PRS and Gary Rosenfield at the RRS.

One project we all worked on together was building the Hang Loose Bi-Plane, a one-man glider made of bamboo, wood, wire, & plastic sheeting. We cut and bent bamboo spars for the airfoil wings at Korey’s house over his mom’s gas stove. The glider had around a 14-foot wingspan and a 12-foot rudder.  It was Korey that drew the short straw to fly first. With Korey hanging in the center and the two of us at the wing tips we took off running from the top of a hill in Granada Hills. Korey lifted off about 10 feet in the air and started sailing down towards a school fence at the bottom where he bailed out before hitting.

Another thing we did that I can mention now was flying model rockets out of Korey’s in ground swimming pool. We sealed the motor and electric igniter with wax and lowered the rocket and launch pad to the bottom of the pool with the controller on deck. All I can say is that a sea launched rocket is pretty cool when it breaks the surface!

There were many interesting things we did with Bob and we remember him dearly. He loved his muscle car too, I remember other drivers on the 405 Freeway coming along side trying to race us, but Bob wasn’t a speeder, just a tinkerer. I often wonder what became of that car.

Mark Clark further reports on the Tripoli members forum:

“Brandy [aka Bob] started flying rockets in the 1960’s and at Miles Square Park and very early Lucerne launches. Getting into high power in the late 1980’s, he had moved to the Phoenix area and was a founding member of Arizona High Power Rocketry Association (AHPRA).

Brandy started Sonic Systems that locally sold reloads and nationally 7 1/2″ sized mosquito-type nosecones. Those who saw the ads in High Powered Rocketry (HPR) magazine will remember them. Brandy was also involved with the BALLS launch for the 18 years AHPRA was involved and a frequent poster to these forums. Brandy was a great friend for nearly 30 years.”

www.ahpra.com

www.ballslaunch.com

Brandy “Bob” Bruce-Sharp at the BALLS 25 launch with his up-scaled Centuri Enerjet 2650 rocket

MTA launch event, 2019-07-10

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by Larry Hoffing, RRS Events Coordinator

The RRS was glad to host an event at the Mojave Test Area for the UCLA Rocketry Club. This group of two dozen students launched a series of G-sized model rockets for their rocket building event on July 10, 2019.

Group photo under the RRS sign to the MTA

Each of the rockets had an egg as its payload. All but one was recovered intact. Each rocket had a custom data logging package including a barometer as an altimeter and an accelerometer. Average altitude was 2,480 feet with a group average peak acceleration of 14 G’s and thrust of 25 lbf.

Loading the rocket on the slotted rail launcher
Rocket on the rail and ready to go
Successful recovery; five of the six teams got their eggs back intact

One concern some of our members had from last week was if any of the structures at the MTA suffered any damage from the recent pair of earthquakes at Ridgecrest only a little more than 30 miles away across the dry lake desert floor. The RRS is happy to report that the damage seems minimal in that both the old block house is still standing and the George Dosa Building doesn’t look any worse for wear.

The old MTA blockhouse after the 7.1 Ridgecrest earthquake of July 5, 2019
The back door of the George Dosa building.
The students of the UCLA Rockets Club, 2019-07-10
Our events coordinator, Larry Hoffing, proudly shows his passion for rockets and the RRS

The RRS was glad to support this student event with UCLA. There will be a second, similar rocket building program later this month. For questions about future events, contact Larry Hoffing

events@rrs.org