May 2021 Virtual Meeting

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by Keith Yoerg (RRS Secretary)

The latest meeting of the Reaction Research Society took place this past Friday, May 14th and had 20 attendees – including a guest presenter and a project update from the Compton Comet team, which is composed of RRS members. We kicked off the meeting saying vitrual hello’s and catching up on personal updates.

Screenshot of discussion during the monthly meeting

UPCOMING EVENTS AT THE MTA

The group kicked off society business by planning for upcoming MTA events later this month. Wolfram Blume is continuing progress on the Gas Guzzler, but windy forecasts continue to limit his ability to do further launch testing. Osvaldo and Wolfram planned to visit the MTA on May 16th to do a practice setup for a future static firing and some housekeeping tasks at the property.

Osvaldo also informed the membership about an active day planned for Saturday, May 29th with groups from UCLA planning to do another static firing of their hybrid motor and a liquid rocket launch to 33,000 ft. and a team of students firing model rockets. Several additional RRS members expressed interest in attending this event.

GUEST PRESENTATION – COBRA FIRING SYSTEMS

Scott Smith, the founder of Cobra Firing Systems was our guest presenter for this month, continuing our recent discussions on wireless launch controllers. Scott has been in the pyrotechnics industry for 10 years, and developed Cobra into a 25-person company with roughly 14,000 customers around the word. They have worked with Mythbusters, Disney, and the US Military to name a few.

Scott describing the underlying technologies behind the Cobra Wireless Firing Systems

RRS member questions for Scott focused on safety, in particular the risk of misfires and adding a physical shunt to the system. The data is encrypted, includes checksums, and is built around a US-based company Synapse, which has allowed the company to avoid any reports of accidental misfiring due to stray wireless signals. Cobra firing boxes are modular in nature and allow for what the company calls a “slat” – which allows for a cap to be used as a physical, mechanical shunt on the system.

MEMBER PRESENTATION – COMPTON COMET

RRS student members Manuel Marques, Aarington Mitchell, and Tre Willingham presented on the status of their project the “Compton Comet” which is being built at the Compton Airport under the guidance of RRS members Waldo Stakes and Dave Nordling.

The Compton Comet team presenting to the membership

The rocket is a 75% ethanol & liquid oxygen bi-propellant rocket with a regeneratively-cooled engine. The engine is a surplus XLR-11 which should produce roughly 1,500-lbf of thrust, and was originally used in a group of 4 to power the Bell-X1 (the first aircraft to break the sound barrier). The rocket is estimated to reach an altitude of 20,000 km and will use a 2-parachute dual deployment recovery system.

THE FUTURE OF IN-PERSON RRS EVENTS

Members discussed the likelihood of in-person RRS events like the Symposium and meetings at the Gardena Community Center in 2021. It mentioned that the Symposium typically takes between 90 to 120 days to prepare, and it would be unlikely that the RRS would host one before spring 2022. There was a bit more of an optimistic outlook on the monthly meetings with a tentative goal set for a return to the Community Center in August (pending COVID restrictions).

MTA PERMANENT BATHROOM STATUS UPDATE

Designs and plans for the permanent bathroom structure at the MTA have been the main focus of the ongoing, twice-monthly meetings of the RRS Executive Council. Frank updated the membership on the current status of the project, which has gone through several iterations. Currently, RRS member Wilbur is working with professional drafters to get precise designs on paper – including model numbers for things like toilets and water heaters. A precise, written design will help the society get a final product that matches expectations.

The current plan is to build 2 or 3, 20-foot containers with 2 bathrooms each or 1 bathroom and 1 shower. These will be transported to the MTA and installed on concrete plinths which drain to a concrete septic tank and leach field. Water will be supplied by a well and stored in a tank installed on top of the bathroom or a nearby storage container. The bathroom facility is planned to be located southeast of the Dosa building, alongside the existing storage containers.

RRS BY LAWS

The RRS Executive Council has reviewed the recommended changes to the By Laws provided by the 2020 constitutional committee. Following are the By Laws as agreed to by the 2021 RRS Executive Council:

2021 RRS By Laws

LAUNCHING & STRUCTURES

Richard Dierking raised a question regarding the new structure being built on the Polaris land adjacent to the RRS site, and whether it must be considered an occupied structure during launch testing at the RRS site. This prompted a lively debate about the nuances of the regulatory framework around rocket activities in the Mojave desert, with several members voicing their opinions.

Safety of all personnel must be the #1 priority during activities at the MTA & communication between between the RRS, FAR, and Polaris is the best way to ensure that. Concurrent operations at adjacent properties are avoided when possible, and the RRS maintains relationships with our neighbors so that the Pyrotechnic Operator in charge is in contact with & can ensure the safety of personnel at adjacent property when operations overlap.

NEXT MONTHLY MEETING

The next RRS monthly meeting will be held virtually on Friday, June 11th at 7:30 pm pacific time. Current members will receive an invite via e-mail the week of the meeting. Non-members (or members who have not received recent invites) can request an invitation by sending an email to:

secretary@rrs.org

MTA launch event, 2021-05-01

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by Dave Nordling, Reaction Research Society

The Reaction Research Society held an event at the Mojave Test Area (MTA) on May 1, 2021. Dave Crisalli was the pyrotechnic operator in charge. RRS president, Osvaldo Tarditti, was also present along with myself, It was not to be a launch event as all planned tests were static firings by the UCLA liquid rocket team and the UCLA hybrid motor team. The winds were very high that day consistently above 20 MPH and gusts above 50 MPH at times. The weather otherwise was very cooperative with comfortable temperatures.

Other than gusting and persistently hugh winds, it was a great day at the MTA on 5/1/2021

Dave Crisalli gave a safety briefing in the George Dosa building to all attendees before the first static fire campaign would begin. The RRS pyrotechnic operator in charge is responsible for the safety of all during the event. Hazard identification (spiders, snakes, sharp objects) and good practices (hydration, sunscreen) are always part of the briefing, One of the most important things, Dave Crisalli mentioned was not to be in a hurry. It is very important to take the proper time to do things correctly and safely even if it means not proceeding with the intended test that day. Taking your time means avoiding mistakes and improving your chances for success.

Xavier Marshall observes the UCLA hybrid motor controls setup at the RRS MTA on 5/1/2021.

RRS members, Bill Inman and John Wells came to the MTA for the event, but only as spectators. The Solar Cat project is still active and undergoing improvements to its sun tracking method. Bill is also expanding the collector area and adjusting the necessary support structures. It is likely Bill and John will be back for the next RRS MTA event.

Dave Crisalli (left) and Bill Inman (right) at the RRS MTA vertical test stand on 5/1/2021

Also in attendance was the Compton Comet team who have all recently joined the society as members. It was their first time visiting the MTA and getting a chance to see another university team conduct liquid rocket test operations at our vertical test stand.

Members of the Compton Comet team, Manuel Marquez, Aarington Mitchell, Tre Willingham (from left to right) wait at the Observation Bunker at the MTA for the hybrid motor firing with Waldo Stakes (at right).

RRS member, Wolfram Blume came by the RRS MTA to take measurements of the vertical test stand for a future static fire test of his ramjet upper stage engine. He intends to use a leaf-blower compressor motor to simulate foward air flow, but a lot of calculations and planning is required before proceeding. The vertical test stand has a winch and pulley system still attached from Richard Garcia’s liquid motor test in 2017. It should be adequate for Wolfram’s lifting needs when mounting the test equipment to the stand.

The vertical test stand with the winch and pulley system still mounted.

The UCLA team spent the night before on our site setting up their equipment. This advanced planning paid off as they were ready for the first of two hot-fires of the liquid rocket just past noon.

Camera adjustments made before the first hot fire of the UCLA liquid rocket on 5/1/2021

Often, it can take several hours to verify all systems are in good working order before testing especially with a liquid rocket, The hybrid rocket was no exception that day.

The UCLA hybrid motor team installs the fuel grain and nozzle into the 98mm standard motor casing,
The UCLA hybrid motor mounted for static fire on the RRS MTA I-beam

One of the two load cells had failed so the two teams had to share the same load cell between the hybrid motor and liquid motor firings. UCLA chose to let the hybrid team go next after successful results were seen with the first firing, The UCLA hybrid motor team corrected a few issues and were able conduct a successful hot-fire by late afternoon.

The society members in attendance also had time to make some minor repairs to the new mobile trailer asset, A steel plate was added to keep intruders from entering. Thanks to Waldo Stakes for doing the welding for this temporary fix.

The mobile trailer at the RRS MTA needs a lot of repairs

There was sufficient daylight remaining for a second hot-fire of the UCLA liquid rocket, The team had another engine with the previous injector design from last built and ready with a fresh internal ablative liner. They had retanked another load of ethanol and the liquid oxygen cylinder had sufficient stores for another loading cycle.

Preparing for liquid oxygen transfer to the propellant tank

Thanks to the hard-won, acquired experience of the UCLA team and their commitment to training new members and holding to their proven procedures, they were able to conduct the second firing safely for an impressive finish that day.

The UCLA liquid rocket team poses before their liquid rocket after a second successful hot fire on the same day.

Initial data from both UCLA static firings of their liquid motor suggest that the 650 lbf nominal thrust motor outperformed expectations and will be ready for vehicle integration and flight by May 29, 2021. The UCLA team had reason to celebrate at the end of the day. The RRS was glad to be a part of UCLA’s continued campaign to fly liquid rockets that are competitive with any university team in the country.

For other universities interested in working with the RRS, please contact the society president submitting a Standard Record Form downloaded from our website,

president@rrs.org

Static Fire Test of Hybrid Motor at FAR, 2021-04-17

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Dave Nordling, Reaction Research Society

Based on the recent lacking performance of the Contrails H222 nitrous oxide commercial hybrid motor, a pair of static fire tests were conducted to improve the ignition and severance of the nylon fill line. The latest of these static firings was conducted at the Friends of Amateur Rocketry site south of the RRS MTA on 4-17-2021. This was done for simple convenience since I was unable to attend the MTA launch event in the week prior. Mark Holthaus and John Newman oversaw my static firing and offered good ambien advice. Fellow RRS member, Dmitri Timohovich, joined me that day and brought his four channel firing box to conduct the remote fill and fire operations of the hybrid.

Dmitri connects the fill manifold to the nitrous oxide bottle at FAR
Orange fill and firing box for the hybrid motor
Fill, drain and firing circuit for a Contrails hybrid rocket motor. The separate vent solenoid valve hasn’t been added. Weight scale is also a separate feature and not necessary for operation.

Nylon is one of the stronger polymer tubing materials which can handle the 900 to 1200 psig nitrous oxide pressure when flow is supplied from the solenoid valve controlled manifold. The problem is that this strength makes it difficult to quickly and cleanly sever the Parker NBR brand, 3/16” OD fill line allowing the nitrous oxide to flow against the fuel grain while gabapentin getting reliable ignition.

The original ignition method as designed by the manufacturer is a small resistor in place of an electric match and the use of a Pyrodex pellet which is essentially a pressed cylinder of black powder. The first flight attempt of the nitrous oxide hybrid rocket used this method but was not successful.

Contrails Rocketry, H222, 38mm, 16-inch high powered nitrous oxide hybrid motor

Earlier builds of the hybrid motor used electric matches and small scraps of composite propellant grain for a swifter and hotter ignition. The first two flights showed evidence of the fill line remaining connected. A better means of ignition and fill line severance was needed.

February 2021 launch of the hybrid motor in Larry’s 3-inch rocket body. It is clear that a hot plume is exiting the nozzle but the sharp arc to the north seems to indicate that the fill line is still attached.

The composite propellant is an ammonium perchlorate, aluminum powder and HTPB binder mixture with some red iron oxide used as an accelerant. These scraps were from RRS member, Larry Hoffing’s, small solid motor that he unsuccessfully tested at the MTA in 2019.

The Contrails H222 motor was mounted upside down due to the lack of a proper motor retainer feature. The static firing was the primary purpose which resulted in a feeble puncture of the filling line and no subsequent ignition.
The aft end of the hybrid motor mounted for static fire at the RRS MTA on 3-20-2021
Failed ignition resulted from the 3-20-2021 static firing. Disassembly revealed an excessive amount of electrical tape and an uneven burn around the fill line circumference was the most likely cause.
Previous solid propellant grain motor test in 2019 was a failure, but the remaining tailings from the casting were useful in boosting the ignition power in prior hybrid motor tests

The last static test at the MTA failed to achieve ignition and only created a small tear in the fill line without achieving ignition of the grain. The composite fuel grain fragments were getting clean ignition but the electrical tape wrapping method I used failed to adequately focus the high temperatures to getting clean ignition and severance of the black nylon fill clomid visa line.

At John Newman’s suggestion, we used a small ring of composite propellant grain at the forward end inside the hybrid high-performance (HP) fuel grain. These were made from a 22mm cylinder that was cut to a 3/4-inch length and drilled out to a 3/8-inch hole size which is roughly twice the diameter of the black nylon filling line passing through. This larger hole would allow the electric match head to be in close contact with composite propellant ring. As the solid propellant charge burns it focuses the tremendous heat of combustion on the nylon fill line causing it to soften, extrude and cleanly sever.

John Newman uses his lathe at his shop to gently machine fuel grains for custom applications https://www.winwaed.com/blog/getting-antabuse-without-prescription/.
The ring of 22mm diameter composite propellant grain fits within the head-end of the hybrid fuel grain and can be pressed flush to the edge. A 3/8-inch hole is run through the 3/4” long segment to allow the nylon fill line to pass through with enough room for the electric match head
Floating injector (left) with the nylon fill line pushed into the Parker push-to-connect fitting. Composite propellant grain is pressed in flush to the edge and electric match head can be seen beofre it is secured to the fill line to get the proper position when the motor is assembled
Snap ring, graphite nozzle and steel nozzle washer finish the motor grain assembly inside the 16-inch aluminum body of the H222 model
The complete motor assembly clamped into the unistrut holding fixture. The clear vent line at the head end must protrude to the outside to give a visible and audible indication when the oxidizer volume is filled with liquid before committing to firing.
Dmitri Timohovich makes adjustments to the clamps holding the hybrid motor in place. Peak thrust is just above 200 lbf according to the official thrust curve data for this H222 model.
Four channel firing box sits at a safe distance from the static fire test stand.
Dmitri Timohovich (left) and Dave Nordling (right) pose next to the unistrut mounted static fire mounting of the Contrails Rocketry H222 high-powered 38mm hybrid motor ready for testing at the FAR site on 4-17-2021

With everything in place, we called over the pyrotechnic operators in charge for this FAR event. After inspecting the connections and describing the fill and fire procedures, we were authorized to begin the short filling process.

Successful ignition of the hybrid motor at FAR

The hybrid motor was loaded, fired, reloaded and fired again. Both times stable ignition was achieved and the fill line dropped out of the motor as expected. We had to abort the initial second firing as visual confirmation of the nitrous oxide completing fill was not apparent. Given the hybrid motor has a small weep hole in the head end of the motor means that given time the nitrous oxide will leak out safely. The clear 1/8” acrylic vent line had become tangled in the unistrut obscuring the liquid plume. Trimming the acrylic vent line helped to keep the tip more visible on the second and last firing that day.

Cheap and simple, the 3-inch Little John from Mad Cow Rocketry

The next step will be to purchase a 75mm rocket body able to integrate the 16-inch long, 38mm standard hybrid motor inside. The 3-inch Little John rocket from Mad Cow Rocketry was selected and should arrive soon. With luck, the rocket can be built and ready for 1010-rail launched flight at the next RRS MTA event on 5/1/2021.

The RRS is thankful for the support of FAR at their facility for this static fire. Dmitri and I conducted a safe dispoal burn of the scrap propellant. I was able to acquire a few more propellant ring segments for subsequent tests of the hybrid in flight. Later, we plan to revisit the Pyrodex black powder charges with the electric resistors as the initiator. It is not clear if this will be as effective as the high temperature composite grains and an electric match, but it is worth a try.