September 2019 meeting

by Dave Nordling, Secretary, RRS.ORG


The Reaction Research Society (RRS) met on Friday, September 13, 2019. We had several new people come out to visit including the CSU Long Beach liquid rocket team. They were coming to learn more about the society and our resources at the Mojave Test Area (MTA).

The RRS had a special occasion to celebrate at the meeting which we did with pizza. The RRS now has three new licensed pyro-ops, Osvaldo Tarditti, Larry Hoffing and Dave Nordling. This will help us a lot in holding more events at the MTA.

Abel, Wally, Tustin and Hunter from the CSULB Beach Launch Team, enjoyed our celebration and stayed for the meeting.

Since we had so many new people coming to the meeting, we decided to make introductions and share some of the stories and latest projects before getting to the meeting agenda topics.

Wolfram Blume, new member to the RRS, discussed his plans to static fire a gasoline fueled subsonic ramjet

New RRS member, Wolfram Blume, came to the meeting tonight to discuss his plans to build, test and ultimately fly a gasoline fuel ram-jet called the Gas Guzzler project. He’s been working on this project since 2011 and he presented the RRS president with his test request to conduct a static fire test along with many details of his initial designs. The RRS has not tested a ramjet in many years and this will be a very interesting project as it develops.

Waldo Stakes, RRS member, explains his latest progress with the steam rocket he’s been working.

Waldo Stakes came to the meeting to share with the society his latest progress with a steam rocket he’s been working on for Mad Mike Hughes. Waldo’s projects are always fascinating as he’s worked with a lot of different groups over the years in racing and in rocketry. He’s also been working with Compton College on the planning of their large liquid rocket. The RRS is also glad to be a part of Compton College’s ambitions to build a liquid rocket.

Mario and Oscar of Compton College with RRS member, Kent Schwitkis listen to Bill Behenna present his latest avoinics payload project to be built for the RRS alpha.

RRS member, Kent Schwitkis and a couple of his students from Compton College came to the society meeting. There are many bright students at Compton College interested in working with the RRS and we have already began to assist each student with tasks specific to projects their working at the college.

Bill Behenna shows his latest prototype of an alpha payload to measure acceleration and barometric pressure.

We decided to showcase our membership project first before beginning our agenda which was a very good idea. Bill Behenna has been hard at work on his avionics payload to be built to fly in the many RRS standard alphas we have at most of our launch events.

After calling the meeting to order and the reading of the treasury report, the RRS began our September meeting agenda.

(1) Next Launch Event at the RRS MTA with LAPD CSP and Boyle Heights

The RRS has finished with the last classroom presentation of the series. The students have painted their rockets and are ready for the final launch day, next Saturday, September 21, 2019. After propellant loading, the RRS will be ready to receive our next group to watch their handiwork take flight in the desert.

(2) RRS facility improvements

Osvaldo has been leading the task of evaluating facility improvements to the RRS. The main improvements under consideration are (1) improving our restroom facilities at the MTA and (2) replacing the old blockhouse at the MTA. Osvaldo has made some drawings of the new restroom facilities and is discussing the details with a vendor to get a quote.

In early August, our large adjustable rail launcher was damaged in a failed launch attempt of a large solid motor. Osvaldo began repairs and hopes to have the box rail system restored soon.

The RRS MTA site was also the victim of theft of many things from the George Dosa building. Security at our test site is difficult given its remote location. Several suggestions were made including adding cameras, improving our locks and doors, making opaque window inserts for the building, and simply being present at the site more often. The RRS has been the victim of theft before, but it is something that is never easy to recover.

(3) 2020 Constitutional Committee report

The committee was not able to make their report this month. Several factors have contributed to this delay over the summer. The committee will make its presentation to the society at the next meeting in October.

(4) Society votes on holding the 2020 RRS Symposium

After some discussion last month, the society decided that we will in fact hold the next RRS symposium in the Spring of 2020. Given the increasingly successful events we’ve had since 2017, and the many people who have encouraged us to keep this annual event, the administrative membership voted in favor. Frank Miuccio will again be our symposium coordinator and the RRS will be reaching out to presenters and exhibitors very soon. Our next order of business will be setting the date which is likely to be in the month of April.

(5) RRS to present at the CATIE conference at Antelope Valley College

Dr. Khalil Dajani of CSU Long Beach has invited the RRS to be one of the presenters at the Space Responsiveness Workshop and Exhibit at Antelope Valley College at the Hellenic Center in Lancaster, California. The 2019 California Aerospace Technologies Institute of Excellence will be held on Wednesday, September 18th where members from industry and the government will hear our presentation introducing the society and our capabilities at the Mojave Test Area. We hope to make some great contacts at this event and begin some new partnerships..

https://www.avc.edu/news/2019/Sept/space_responsiveness_workshop

(6) RRS social activities in planning

The RRS has focused a lot on educational and project activities, but we don’t often plan simple gatherings for fun. Larry had talked about having the RRS visit Mt. Wilson as a private group. At the meeting, we also talked about having a simple barbecue at the MTA as was done in times past. We plan to revisit this discussion again. Other members are welcome to share their ideas.

(7) RRS history project – Garboden archives

Lifetime member, George Garboden, has many boxes of papers and reports from the RRS in his possession that he would like to pass back to the society for archival. In support of the RRS history project, the society is always glad to get articles, clippings and any kind of archival materials and make them more available to our membership. Frank, Larry and I have been working on the logistics of getting a new storage location, but the most important step is finding the time to carefully make quality scans.

(8) Social media improvements

Alastair Martin announced the next pending episode of his podcast, Rocket Talk Radio. Other fellow RRS members, Dave Nordling and Richard Garcia, will take part in the next installment of the “Before SpaceX” series on September 28th. In this episode, we will be interviewing Jim French. Jim has had a long and interesting career as a rocket development engineer for the H-1 and F-1 engines at Rocketdyne in the 1950’s and later at TRW in the 1960’s with the Lunar Descent engine during the heyday of Apollo. His book “Firing a Rocket Engine” is available on Amazon.

“Firing a Rocket” by James French

Jim French also worked for a startup company called the American Rocket Company (AMROC) in Camarillo in the late 1980’s and early 1990’s. We hope to have a great conversation and learn a lot about his experiences at this commercial space company.

(9) Memories of George Dosa

As our last order of business, we shared with the society that we lost one of our oldest and most beloved members of our society. In our long history, George Dosa, had a profound impact on the society and many of our past and present members.


The RRS adjourned our meeting after a long series of very interesting discussions. We are thankful to all for coming and we will be holding our next monthly meeting, October 11, 2019. If there are any changes or additions to make to this monthly report, please notify the RRS secretary.

secretary@rrs.org

April 2019 meeting

The RRS held our monthly meeting on April 12, 2019 at the Ken Nakaoka Community Center in Gardena. We had a full agenda with the 2019 RRS symposium just around the corner on Saturday, April 27th.

The symposium is just around the corner

We first welcomed two new members, Keith Yoerg and Jonathan Martinez. Keith is active with Tomorrow’s Aeronautical Museum (TAM) at the Compton Airport and has given many educational programs to local schools. He’s also a graduate of USC and a former member of their Rocket Propulsion Laboratory (RPL). Jonathan Martinez joins the RRS as a student member from Compton High School. He’s been working at TAM and the RRS hopes to help him in his new project to hot-fire a liquid rocket.

Keith Yoerg (left) watches Waldo Stakes (right) show off the gas generator injector he brought to the meeting.
New RRS member, Jonathan Martinez (left) and Wilbur Owens (right) at the April 2019 meeting of the RRS.

We next talked about the recent launch event with LAPD CSP and Compton Elementary. The “Rockets in the Projects” program is going strong and we were glad to welcome Compton Elementary to our workspace and launchpad in the Mojave Desert.

Dave Crisalli, our pyro-op for the event, gives the safety briefing to all attendees including Compton Elementary, LAPD and USC RPL

Under very pleasant weather, we had a good launch event starting with a tour, safety briefing and the kids finally getting a chance to see their rockets fly into the blue sky. Osvaldo had a seventh alpha rocket with a parachute system, but somehow failed to deploy. USC static-fired a six-inch custom solid motor.

An alpha assembled at Compton Elementary streaks away from the box rails at the RRS MTA
USC’s six-inch solid composite grain motor burns for full duration at the RRS MTA. A second motor will be integrated into the Traveller IV vehicle that USC will launch from Spaceport America in New Mexico

After Compton Elementary and LAPD CSP went home, Osvaldo, Frank, Larry and I did a little reconnaissance for the alphas we flew at the event. We were able to find 3 of the original 6 and one more alpha from the past MTA launch event. The higher level winds have been carrying the alphas in a more northerly direction west of the launch rails. For reference, Osvaldo recorded the following coordinates for one of the alphas found: 35* 21′ 16.83″ North, 117* 48′ 50.03″ West.

Using the local wildflowers, Larry marks the location of a newly recovered alpha from the last MTA launch event

The 2019 RRS symposium was the next topic. We have over 300 Eventbrite tickets sold at the time of the meeting. The symposium has confirmed a full roster of speakers including AFRL Edwards AFB, Northrop-Grumman, USAF SMC. We decided not to hold the panel discussion this year. The symposium will start at 8:45AM on Saturday, April 27th.

Frank Miuccio goes over the preparations for the 2019 RRS symposium to be held on Saturday, April 27, 2019

The Ken Nakaoka Community Center in Gardena will allow us to set up the night before (4/26/19) at 7pm until they close at 9pm. There’s a lot of work to be done and we hope all of our membership can come out on Friday and help us with setting up tables and hanging the sign outside.

We also hope all of our membership can help at the symposium on Saturday (4/27/2019) as well. The Ken Nakaoka Community Center opens at 8AM, we will have just a little bit of time to get ready before the event begins at 8:45am with our RRS president, Osvaldo Tarditti, giving the introductory presentation.

RRS member group photo from last year’s 75th anniversary symposium (1943-2018)

The next topic of discussion at the April 2019 meeting was facility improvements at the RRS MTA. The society has decided to invest in upgrading our blockhouse and building a new restroom facility at the site for better creature comfort for the increasing number of guests we’re having each year. Osvaldo has been working up the plans for these two facility improvements and will get bids very soon.

We also hope to solicit donations from the public at the symposium to help the society reach our goals for these facility improvement projects. To anyone wishing to make a monetary donation to the RRS, you can use the “DONATE” button on the RRS.ORG homepage which connects to Paypal. Please leave us a note and accept our thanks. The society is striving to improve our facilities as we prepare to have more events this year.

Osvaldo also told us more about the RRS participating with CALFIRE in their review of the state laws governing amateur rocketry. Members of the Friends of Amateur Rocketry (FAR) organization have also been working with CALFIRE on this important committee. It is the goal of the RRS to inform the public and governing agencies on ways to make the law reasonable, practical and just to the amateur rocketry as we uphold our commitment to public safety. CALFIRE has been very supportive of our hobby and we are building stronger relationships with the State of California and our fellow rocketry organizations.

Dave Crisalli (RRS member), Larry Hoffing (RRS events coordinator), Ramiro Rodriguez (CALFIRE) and Osvaldo Tarditti (RRS president) at the RRS MTA launch event on 4/6/2019

Discussion on our last topic on the agenda was about the RRS’s participation with the base11 project. We were not able to talk about this subject in much detail as closing time had fast approached. As an educational non-profit group, the RRS has a charter to support university groups. The base11 project is very ambitious in its goal of student-run teams building and flying a liquid rocket to an altitude of 100 km or higher. This multi-year program will be a challenge on many levels both financial and technical. The RRS is happy to support the base11 Space Challenge at the RRS MTA.

The RRS is proud to support teams for the Base11 Space Challenge

The remaining agenda topics will be covered in next month’s meeting including the quarterly progress update on the SuperDosa project and the RRS partnership with Tomorrow’s Aeronautical Museum (TAM).

The Reaction Research Society meets the 2nd Friday of each month at the Ken Nakaoka Community Center in Gardena, California, at 7:30pm.

The RRS is very exciting about the projects we have planned for this summer. Our next monthly meeting will be Friday, May 10th, 2019 at 7:30pm.


Liquid Rocket Components: Pyrotechnic Valves

by Tom Mueller


Editor’s Note: This is a reprinting of the original article written by RRS member, Tom Mueller on the subject of pyrotechnic actuated valves around 1995 (?). He mentions the build of two different rockets (the XLR-50 and the Condor) and a hypergolic rocket he intended to build after this article was written. We hope to gather more photos and details about these rockets and display them in future improvements to this posting. For now, please enjoy the subject matter as the information is very relevant today to amateur builders of liquid rockets. The RRS has been very active lately in re-exploring liquid rockets. The society thought this would be a timely and interesting subject to share with our readers.

For any questions, please contact the RRS secretary, secretary@rrs.org


For an amateur rocketeer seeking to build a liquid rocket, one of the most difficult components to obtain or build are remotely operated valves. A liquid rocket will require at least one valve to start the flow of propellants to the combustion chamber. In the two small liquid rockets I have flown in the last year or so, both used a pyrotechnic fire valve located between the pressurant tank and the propellant tanks. The propellants were held in the tanks by burst disks (or equivalent) in the propellant run lines. When the fire valve was actuated, the sudden pressure rise in the propellant tanks blew the burst disks, allowing propellant to flow to the injector. This method of controlling the flow to the rocket allows the use of only one valve, and eliminates liquid valves.

In the case of the first rocket, the XLR-50 which flew in October 1993, elimination of the liquid valve was important because the oxidizer was liquid oxygen, and a small cryogenic compatible valve is very difficult to construct.

For the second rocket, which flew in October 1994, the small size prevented the use of liquid valves. In fact, the single pyro valve I used was barely able to fit in the 1.5 inch rocket diameter. In this article I will describe the design of the valves that were used on these two vehicles, and variations of them that have been used in other rocket applications.

FIGURE 1: XLR-50 pyro-technic “fire” valve

The valve shown in Figure 1 consisted of a stainless steel body with a 0.375 inch diameter piston. The O-rings were Viton (material) and the squib charge was contained in a Delrin plastic cap. The Delrin was used to prevent shorting of the nichrome wire, and also to provide a frangible fuse in case the squib charge proved to be a little too energetic. In practice, I’ve never had the Delrin cap fracture.

The inlet and outlet lines to the tanks were silver brazed to the valve body. The valve was tested many times at inlet pressures of up to 1000 psi without any problems, other than the O-rings would need replaced after several firings due to minor nicks from the ports. To help alleviate this problem, the edges of the ports were rounded to help prevent the O-ring from getting pinched as the piston translates. This was accomplished using a small strip of emery cloth that was secured in a loop in one end of a short length of 0.020-inch stainless steel wire. The other end of the wire was clamped in a pin vise which in turn was chucked in a hand drill. As the wire was rotated by the drill, the emery was pulled snugly into the port, where it deformed into the shape of the inlet, and rounded the sharp edge. I used WD-40 as a lubricant for this operation, allowing the emery to wear out until it would finally pull through the port. I repeated this process a few times for each port until the piston would slide through the bore without the O-rings snagging the ports.

Another requirement is to lubricate the O-rings with a little Krytox grease. This helps the piston move freely and greatly reduces the problem of nicked O-rings.

FIGURE 2: Fire valve for a micro-rocket

The pyro valve I used in the 25 lbf thrust micro-rocket that was launched in October of 1994 is shown in Figure 2. This valve was identical in operation to the XLR-50 valve, with the major difference being its integration into the vehicle body. The valve body was a 1.5 inch diameter aluminum bulkhead that separated the nitrogen pressurant tank and the oxidizer tank. Because of the very small diameter of the rocket, the clearances between ports and O-rings were minimized, just allowing the valve to fit. The fuel outlet port was located at the vehicle center, providing pressure to the fuel tank by the central stand pipe that passed axially down the oxidizer tank. The piston stop was a piece of heat-treated alloy steel that was attached to the valve body by a screw. This stop was originally made from aluminum, but was bent by the impact of the piston in initial tests of the valve. The black powder charge in the Delrin cap was reduced and the black powder was changed from FFFg grade to a courser FFg powder, but the problem persisted. The stop was re-made from oil hardening steel and the problem was solved. In this application, the port diameters were only 1/16 inch so only a small amount of rounding was required to prevent the O-rings from getting pinched in the ports. The valve operated with a nitrogen lock-up pressure of 1000 psi.

FIGURE 3: Fire valve for Mark Ventura’s peroxide rocket

A more challenging application of the same basic valve design was used for the fire valve of Mark Ventura’s peroxide hybrid, as shown in Figure 3. This was the first application of this valve where liquid was the fluid being controlled, rather than gas. In this case the liquid was 85% hydrogen peroxide. The second difficulty was the fact that the ports were required to be 0.20 inch in diameter in order to handle the required flow rate. The valve was somewhat simpler than the previous valves in that only a single inlet and outlet were required. The valve body was made from a piece of 1.5-inch diameter 6061 aluminum, in which a 1/2-inch piston bore was drilled. The piston was also 6061 with Viton O-rings, which are peroxide compatible. The ports were 1/4-inch NPT pipe threads tapped into the aluminum body. The excess material on the sides of the valve was milled off, so that the valve was only about 3/4 of an inch thick, and weighed only 4 ounces. Even though the piston size was 1/2 inch, the same charge volume used in the 3/8 inch valves was sufficient to actuate the piston.

In testing the valve with water at a lock-up pressure of 800 psi, I was pleased to find that even with the large ports, O-ring pinching was not a problem. One saving factor was that the larger size of the ports made it easier to round the entrances on the bore side. The valve was tested with water several times successfully before giving it to Mark for the static test of his hybrid.

The only problem that occurred during the static test of hybrid rocket was that the leads to the nichrome wire kept shorting against the valve body. Three attempts were made before the squib was finally ignited and the engine ran beautifully. I have since been able to solve this problem by soldering insulated 32-gauge copper wire to the nichrome wire leads inside the Delrin cap. In this way, I can provide long leads to the valve with reliable ignition.

My next liquid rocket is a 650 lbf design that burns LOX and propane at 500 psia. This engine uses a Condor ablative chamber obtained from a surplus yard. For this reason, I call it the Condor rocket. This rocket uses a scuba tank with 3000 psi helium for the pressurant. I decided to build a high pressure version of my valve as the helium isolation valve for this rocket. When firing this rocket, just prior to the 10 second count, this valve will be fired, pressurizing the propellant tanks to 600 psi. I assumed going in to this design that the O-rings slipping past a port simply wasn’t going to work at 3000 psi.

At these pressures, the O-ring would extrude into the port. In order to get around this problem I came up with the design shown in Figure 4.

FIGURE 4: High pressure helium valve for Condor rocket

For this valve, the O-ring groves were moved from the piston to the cylinder bore of the valve body, so the O-rings do not move relative to the ports. The piston is made from stainless steel with a smooth surface finish and generous radii on all of the corners. The clearance between the piston and the bore was kept very small to prevent extrusion of the O-rings. The valve operation is similar to the one shown in Figure 3, and the valve body is made in the same way except female AN ports were used rather than NPT ports. When the valve is fired, the piston travels from the position shown in Figure 4a to that shown in Figure 4b. During this travel, the inlet pressure on the second O-ring will cause it to “blow out” as the piston major diameter translates past the O-ring groove. The O-ring is retained around the piston, causing no obstruction or other problems. This valve has been tested at 2400 psi inlet pressure with helium and works fine. It will be tested at 3000 psi prior to the first hot fire tests of the Condor rocket next spring.

As a side note, essentially an identical valve design as the one used on the Condor and Mark’s valve is a design shown in NASA publication SP-8080, “Liquid Rocket Pressure Regulators, Relief Valves, Check Valves, Burst Disks and Explosive Valves”.

A second pyro valve is used on the Condor system as shown in Figure 5. This valve is used to vent the LOX tank in the event of a failure to open the fire valve to the engine.

FIGURE 5: Emergency vent valve for LOX tank, Condor rocket

When the propellant tanks are pressurized by the helium pyro valve, the LOX tank auto vent valve (shown in Figure 6) closes. If the engine is not fired after a reasonable amount of time, the LOX will warm up, building pressure until something gives (probably the LOX tank). The pyro valve shown in Figure 5 is used as the emergency tank vent if the engine cannot be fired. The valve body is stainless steel with a stainless tube stub welded on for connection to the LOX tank. This valve has been tested to 800 psi with helium and works fine. In this case, some ‘nicking’ of the O-rings can be tolerated because the O-rings are not required to seal after the valve is fired. The ports in the bore are still rounded, however, to prevent the O-rings from getting nicked or pinched during assembly of the valve.

Even though it is not a pyro valve, I have shown the LOX auto-vent valve in Figure 6 because this design has proven to be very useful for venting cryogenic propellant tanks without requiring a separately actuated valve or control circuit. The valve uses a Teflon slider that is kept in the vent position as shown in Figure 6a.

This allows the tank to vent to the atmosphere, keeping the propellant at its normal boiling point. When the helium system is activated, the pressurant pushes the slider closed against the vent port, sealing off the LOX tank, as shown in Figure 6b. An O-ring is used around the slider to give it a friction fit so the aspiration of the LOX tank does not “suck” the slider to the closed position. This problem happened to David Crisalli (fellow RRS member) when he scaled this design up for use on his 1000 lbf rocket system. I have used this design on the LOX tank of my XLR-50 rocket, which used a 1/4-inch diameter slider, and on the Condor LOX tank, which uses a 1/2 inch slider. In both cases the vent valve worked perfectly.

FIGURE 6: Automatic LOX tank vent valve

The main fire valve on the Condor rocket is a pair of ball valves that are chained together to a single lever so that both the fuel and oxidizer can be actuated simultaneously for smooth engine startup. For static testing of the rocket, I will use a double-acting air cylinder to actuate the valves. For flight, however, I plan to use a pin that is removed by an explosive squib to hold the valve in the closed position. When the squib is ignited, the pin is pulled by the action of the charge on a piston, allowing the valves to be pulled to the open position by a spring. This method may not be very elegant, but it is simple, light, and packages well on the vehicle. David Crisalli has successfully employed this technique on his large rocket.

That covers the extent of the pyro valves I have built or plan to build so far. In the next newsletter, I will present the design and flight of the small hypergolic propellant rocket that used the valve shown in Figure 2.