November 2018 meeting

The RRS held our monthly meeting on Friday, November 9, 2018 at the Ken Nakaoka Community Center in Gardena. After coming to order and the reading of the treasury report, we discussed the agenda topics for this month. We were happy to be joined by new RRS member, Mike Albert.

[1]
Results of the RRS educational event at Weigand Elementary School with the LAPD CSP program was very positive. The launch event at the MTA had an excellent turnout, good demonstrations and ten alphas flown. We are becoming more effective in our execution at launch day, but there are still opportunities to improve the speed of operations while keeping our focus firmly on safety.

RRS president, Osvaldo Tarditti, teaches the kids at Weigand Elementary School

The weather in late October was ideal and we were able to enjoy the low winds and cool weather. With the low winds, the impact of all alphas were able to be heard and the timing by the kids showed the flight times to be very consistent. Many thanks to Osvaldo and Michael Lunny for doing a great job in packing them for what looked to be very good results.

the kids of Weigand Elementary School at the RRS MTA on 10/27/2018

[2]
Frank is in the process of coordinating the next RRS educational event with LAPD to be a school affiliated with the Imperial Courts housing project which should begin in January 2019 sometime around the Martin Luther King holiday. The school will be announced soon once the details are finalized. The launch event will likely take place in March 2019.

Michael Lunny (back table); Mike Albert (left) and Frank Miuccio (right)

[3]
Results of Jack’s ballistic evaluation motor (BEM) testing were discussed. Jack and his team were not able to attend the meeting, likely due to the California wildfires in his area on that night. The testing rig had a few flaws and a missing part. It was unclear if any useful data came from the one test. Osvaldo is working with Jack on improvements to his BEM. A deeper discussion of Jack’s BEM will hopefully come at the next meeting.

Jack Oswald’s BEM tied to a stake in the dry lake bed for stability; undergoing preparations for 10/27/2018 testing

[4]
Results from the horizontal thrust stand testing were discussed. Despite the problems with the foundation slab sliding with the firing of the micrograin alpha rocket, the load cell did record data which partially confirmed the impulse bit measurements from the past. Many people enjoyed watching the footage, but in all seriousness, an appropriate mounting foundation needs to be made to continue tests.

Matteo Tarditti secures the load cell fixture to the horizontal thrust stand

One proposed solution was to keep the existing shallow slab and drive a long stake into the ground to restrain the slab from moving south as the nozzle exhaust points north when firing. Another solution is to dig away the soil at the site and pour a deeper, rebar reinforced slab with the same 1/2″-13 female anchors. Keeping the slab low near ground level will keep this simple small foundation from preventing road access around the old blockhouse.

example of a buried foundation slab for the horizontal thrust stand

[5]
The Additive Aerospace flyaway railguide was discussed. The device worked well with the micrograin alpha rocket. The fit was good and the camera footage from different angles showed the alpha in the railguide rode the full length of the rail flying very straight. The flyaway railguide did not survive its maiden voyage, most likely due to impact from the fall back to the ground. Also, there is a concern that using the micrograin rocket on the aluminum 8020 rail would eventually jam the rails with the zinc-suifide residue that coats the surfaces after each launch.

Flyaway railguide clamped around an RRS alpha

The recovered pieces of the flyaway rail guide. A successful launch but the mechanism didn’t survive the fall back to the ground

[6]
The RRS needs to finalize the 2019 symposium date very soon. Frank and others consulted the local calendars of relevant organizations and schools and we have arrived at two possible dates in April. The announcement for the 2019 RRS symposium will be made very soon as invitations and preparations must begin very soon.

Date to be announced soon, the RRS will hold the 2019 symposium at the Ken Nakaoka Community Center in Gardena

[7]
We had a discussion of safety issues and propellant handling protocols during the meeting. The issue is complex and there are different opinions about what the RRS should require of our attendees and membership, but two points that were made clear is that safety is most important and that the RRS will seek to educate our membership about compliance with the applicable laws and best practices from our membership experience.

[8]
The RRS visit to the Experimental Aircraft Association (EAA), Chapter 96, at the Compton Airport on November 3rd was a success. RRS and EAA member, Xavier Marshall, gave Osvaldo and I a good tour of the hangar and their machine shop.

The EAA 96 hangar at the Compton Airport

Inside the EAA 96 hangar, door to the office

The EAA has several airplane projects in work including one by Wilbur Owens. We ate lunch at Wilbur’s hangar and talked about future projects at the RRS including the standard liquid rocket.

Relaxing after lunch in Wilbur’s hangar

Wilbur Owens and Osvaldo Tarditti discuss the RRS standard liquid rocket

The visit concluded with a tour of Tomorrow’s Aeronautical Museum and their rocket laboratory. We visited with some of the students who were working on their rocket project. The RRS was glad to see a lot of enthusiasm for the science we love.

Tomorrow’s Aeronautical Museum at the Compton Airport

The rocket lab inside Tomorrow’s Aeronautical Museum

The EAA membership is quite reasonable at $80/year. Members have access to the facilities at the hangar including the lathe, mill and metal shears useful for both aircraft and rocket structures. For those interested in joining the EAA, contact Xavier Marshall.

[9]
The next order of business was the nomination of officers for the next calendar year by our administrative membership in attendance. The first step was appointing of the election chairman which will be Larry Hoffing. The prior executive council members were nominated to their same posts.

Osvaldo Tarditti, President
Frank Miuccio, Vice President
Dave Nordling, Secretary
Chris Lujan, Treasurer

Larry will email our administrative membership for their votes in the coming weeks. Write-in candidates are allowed. The election ballots will be due a week prior to the next meeting. Results of the election will be announced at the December meeting to be held on Friday, the 14th.

[10]
The RRS may have another launch event at the MTA, but this is dependent on confirmation of the appropriate resources needed to support the event. This will likely take place as soon as next week, or possibly on the Saturday after Thanksgiving. The RRS will post the formal announcement on the “Forum” of this website if the event becomes confirmed.

[X1]
Osvaldo was up in Rosamond and was able to take a short trip to the MTA to extract more of the rockets he could find with his ratcheting extractor tool.

A pile of alphas extracted from downrange at the MTA

In addition to the 15 alphas he was able to bring back for refurbished parts, he found the beta rocket that UCLA had launched.

UCLA’s beta rocket recovered from the desert floor

other parts of the beta rocket were able to be extracted including the beta coupler and a fragment of the red plastic nosecone

This beta rocket had an altimeter payload encased in a vented metal shell. Unfortunately, the Jolly Logic bluetooth solid-state device might have survived the crushing impact but the corrosion from possible rainwater intrusion after being planted in the desert dry lake bed sand for over a year proved to be fatal.

Payload case built into the beta rocket’s payload interior; note how the holes were crushed

Chris Lujan is inspecting the device, but it is very unlikely that any data will be recoverable from the chip. It is a shame as getting direct measurements of a beta flight would be great data to have. I guess we’ll have to try again?

Remains of the Jolly Logic altimeter chip, battery still attached

[IN CLOSING}

Wilbur and Xavier mentioned that the EAA is open to having the RRS use their office for one of our monthly meetings in the future. Given how close the Compton Airport is to the Ken Nakaoka Community Center in Gardena, this is quite practical. The RRS will make the announcement soon if one of our meetings in early 2019 will be at the EAA 96 hangar.

If there is anything here that needs correcting, please contact the RRS secretary.
The next RRS meeting will be Friday, December 14th, 2018.

January 2018 meeting

The RRS met for its monthly meeting, Friday, January 12, 2018, at the Ken Nakaoka Community Center in Gardena. We got a late start (8:04pm), but we covered a lot of ground.

Anniversary issue of the Astro-Jet is now available for purchase ($10/copy)

Everyone is reminded that the anniversary issue of the ASTRO-JET newsletter of the RRS is now available for $10 a copy. This special issue will be available in print only and proceeds go to benefit the society and our upcoming symposium event. Bill Janczewski and I have worked hard to bring this milestone issue together and we will have them ready for printing and distribution next week. To order, you can contact me by email (secretary@rrs.org) and send me your mailing address. Payment can be made by check to the “Reaction Research Society” sent to our P.O. Box 90933, in Los Angeles, CA, 90009-0933, found on our website.

Payment to the RRS for the ASTRO-JET newsletters can also be made by clicking our “DONATE” button on the website which directly links to our Paypal site. Please note your are paying for the ASTRO-JET and the number of copies.

Frank brought one of George Dosa’s liquid rocket chambers to the meeting for inspection by the society. This single element coaxial injector has not been fired, but George had this made several decades ago. There was talk about what modifications could be made to get this article into hot fire.

George Dosa’s coaxial injector and chamber

Richard Garcia also brought his own liquid rocket chamber as part of the on-going RRS standard liquid rocket project he has been championing.

Richard Garcia’s pintle injector and chamber design

After the usual reading of the treasury report, we began to discuss the agenda topics. The meeting began with announcing our new members who have recently joined us: Michael Lunny, Bryan Calungcagin, Nancy Squires, Barsoum Kasparian and Jack Oswald. The RRS is glad to welcome our new members.

The discussion had turned to membership cards. Bill Janczewski has worked up a new card design and Frank was working with Bill on a few changes. The RRS does not issue membership cards except on an on-demand basis. RRS member, Alastair Martin who runs a printing business had several ideas for different types of card stocks and discussed them with the RRS.

Larry Hoffing had asked about getting a short run of business cards to support his role as the RRS events coordinator. Frank had said he has the resources to get these made.

Our discussion then turned to the upcoming RRS symposium to be held Saturday, April 14, 2018. We will try a new format of having our speakers present in the ballroom among our exhibitors. The collared white shirts we gave to our membership running the event was a good idea. We discussed getting these again with iron-on or screen-printed RRS logos to help identify those of us who will be running the event. Frank wanted to have posters showing a decade-by-decade look of the RRS over our 75 year history. This is a great idea and we’ll be working hard to collect old photos to have them on display at the symposium. Easels and other supporting equipment were in short supply as the brick walls of the Ken Nakaoka Community Center made wall-mounting very difficult.

For next meeting, we will discuss more of the details of the symposium including working on our list of presenters and exhibitors. Frank and I have already began to approach some of our prior speakers and exhibitors. We have already confirmed several from industry, government and academia including the LAPD CSP program and the Aerospace Corporation. We expect this year’s symposium to be even greater than last year’s event where we hosted over 200 people.

For the next agenda item, Frank and Larry will begin our next educational event with the students of Florence Joyner Elementary school in conjunction with the LAPD CSP program. This 5-week event will begin sometime in February with an expected launch event in late March. Alastair had indicated he’d like to participate, film and document this event. An update on this event will be given at the next month’s meeting.

Michael had indicated his interest in running an RRS educational event with his old high school, Redondo Union High School. Larry and Frank had offered to help him figure out how best to set this up based on the experience the RRS has had thus far. I had sent him the PowerPoint file I had made which can serve as the basis for the program he can give to an older group of students. This would be the first of several events that Michael and Bryan would like to hold on behalf of the RRS.

Our next agenda topic discussed establishing an account with the regional liquefied natural gas (LNG) supplier, Clean Energy in Boron, California. Richard Garcia has acquired a methane dewar which will be used for liquid rocketry experiments at the MTA. Richard was able to have one of our contacts at the Friends of Amateur Rocketry (F.A.R.) group modify the dewar such that it is ready for use. Our president, Osvaldo, said he would contact Clean Energy and give them the necessary information for the RRS to begin buying quantities of methane.

The next agenda topic was the quarterly briefing of the SuperDosa project. Osvaldo and I have identified chemical suppliers to produce the RRS standard solid propellant mixture recipe. We will meet offline to discuss prices and what is the best approach to proceed. Richard was going to work out some more simulations of our proposed vehicle to get an idea for sizing. The ballistic evaluation motor (BEM) that I designed is still in work. This is an important piece of hardware to characterize the burn rate of our propellant to help finalize and set the grain design. I hope to complete the assembly before the symposium which would also be the next quarterly reporting date (April 13, 2018).

The last agenda item was to discuss how to formalize the proposal process for RRS projects that we would like to seek funding from outside groups. One of the most important things to getting projects funded is to have a clear plan on what the scope of the project is, what purposes it will serve, what exact materials and quantities will be required and what the expected cost of this project will be using real quotes and defensible estimates. The RRS was in agreement and the executive council will meet later to discuss some of these documented proposals I have assembled. Projects include things like making more alphas and beta rockets, 3D printer for RRS use, spare electric generator for the MTA, getting a new launch rail built as backup, obtaining a liquid oxygen dewar…. etc.

The night ran late and our meeting concluded at 9:10pm.

There’s a lot of preparation that must be done in advance of our 75th anniversary symposium on Saturday, April 14th, so we’ll be putting this recurring item on the agenda for next month’s meeting.

For next month’s meeting, Frank will finish his paper rocket air launcher device that he has been making. This was inspired by the last educational event with Grape Street Elementary where the students visited the Space and Missile Command Center at Los Angeles Air Force Base in El Segundo, CA. With luck, we hope to demonstrate it outside the community center and take some video for our YouTube channel.

YouTube – Reaction Research Society

Also, for next month’s meeting, I had promised Frank and Osvaldo that I would bring in my alpha parachute assembly that I have worked into a PVC payload tube. I have resolved some of the issues with my timer circuit, but I am still looking for access to a 3D printer to produce my internal umbilical switch mount.

As always, if there is anything here I have missed or misstated, please let me know. Our next monthly meeting will be held, Friday, February 9, 2018. Hope to see you there.

secretary@rrs.org

RRS standard alpha rocket

Some time ago, I was asked to explain in more detail about the RRS standard alpha rocket. Although it has been frequently referenced, some of our general audience may not be familiar with the many aspects of the alpha. Therefore, I have decided to devote an entire article to this subject.

Alpha rocket iso view

This standard design at the RRS has been a common beginner’s rocket in our amateur rocketry society. We use it in our build events with schools, offer it as an experimental testbed for universities and also for our members to conduct their own experiments. It has a long history with the RRS and we still continue the tradition of building these rockets as it is a nice platform for experimentation and introducing newcomers to amateur rocketry.

RRS president, Osvaldo Tarditti, holds a pair of alphas

A similar “Ft. Sill alpha” rocket design was mentioned in the 1960 book, Rocket Manual for Amateurs, by Bertrand Brinley. Over the years, there have been changes made to the alpha design, but this article describes what has become the RRS standard in the alpha rocket design. I have been told that the 1-inch alpha design was created as a smaller and cheaper-to-fly design from the 2-inch beta design.

The alpha is a single-stage rocket consisting of a 3-foot length of 1.25″ outer diameter (OD) drawn-over-mandrel (DOM) steel tubing to hold the propellant. It is often erroneously referred to as a 1-inch rocket, which is more of a relative size measurement. The propellant tube has four trapezoidal sheet steel fins welded at their edges near the bottom such that the rocket fits with the launcher rail design at the Mojave Test Area (MTA).

the RRS launcher rails for four-finned rockets,
beta launcher is shown

Once ready, the alpha rockets are top-loaded into the rails and the pyrotechnic operator (pyro-op) in charge hooks up the igniter wires once we go into a launch mode.

RRS alpha sitting in the rails

launch rails for the alpha as viewed from above

The propellant tube has a bolted bulkhead at the forward end sealed with an O-ring. With good tolerancing, we’ve had no leakage from this joint and the four 1/4″ fasteners have sufficient retention under the brief ~1000 psi chamber pressure surge during combustion. This solid aluminum 6061-T6 bulkhead is installed first into the top of the propellant tube to begin loading the powdered propellant from the aft end.

coupler and bulkhead piece for the alpha

alpha bulkhead loaded and bolted in

The powdered propellant is loaded using a metal funnel a little at a time and gently and periodically bouncing the tube against a wood block to help settle out any air gaps. Many different improvements to increasing the packing density have been tried by the society over the years, but the society uses no special method for increasing the packing density of the micrograin propellant in most of our launches today.

Alpha tube loaded with micrograin propellant

Next the nozzle is loaded with a thin plastic burst disk (or diaphragm) with two tiny through holes to thread in an electric match (e-match).

electric match and burst disk

An e-match is a common pyrotechnic device used to initiate larger reactions with propellants. An e-match is two thin-gauge wires with a segment of nichrome heating wire bridging them. Covering the nichrome wire is a small amount of pyrogel compound that creates a brief high temperature flame once the match is given sufficient current. The e-match is single-use as the tiny wire is destroyed after ignition.

an Estes rocket igniter or e-match, shown as an example

With the burst disk sitting on top of the nozzle facing inward to the propellant, the e-match is packed into the propellant with the thin wire leads running to the outside. The burst disk sits inside the propellant tube held behind the nozzle closing off the propellant powder in the rocket. Although the zinc/sulfur micrograin propellant is fairly insensitive and stable, the e-match has sufficient energy to ignite the micrograin propellant behind the burst disk.

loaded propellant tube with nozzle and burst disk ready for attachment

The use of a linen-filled Micarta burst disk is not only for practical reasons of holding the propellant inside the tube after the tube is turned right-side up, but it helps build up the chamber pressure after the first few moments after ignition. The burst disk is designed to sacrificially break under the elevated pressure created from initial ignition from the e-match. The thickness of the burst disk is carefully chosen to not over-constrain the initial pressure rise in the propellant tube on ignition. The burst disk fragments then quickly exit the nozzle as the rocket takes off leaving the lead wires behind.

alpha nozzle bolting into the bottom of propellant tube

nozzle loaded on to propellant tube with e-match wires sticking out

Above the coupler is the payload tube. The standard alpha design uses a 1.75″ OD, 0.065″ wall, aluminum 6061-T6 tubing. The standard design calls for an 18-inch payload tube length, but shorter versions have been flown with 12-inch lengths being common in some of our school launches.

Nose cones have been made from wood, Delrin plastic and from solid aluminum. The RRS standard alpha design uses a tangent ogive shape which has been more of a traditional choice. Nose cones sometimes have hollow space inside for more payload capacity, although solid nose cones have also been used. The aluminum nose cones are fairly light and are very damage resistant compared to the plastic nose cones that mash from impact or the wooden ones that shatter. Aluminum nose cones have been re-used in subsequent builds after some turning and polishing.

12-inch payload tube with aluminum nose cone

Instruments are flown in the payload section and although space is very limited in these small rockets, smaller chips have increased the number of measurements possible (altimeters, cameras, barometric pressure sensors…). Smoke tracers have been used in recent events with increasing success. This helps in spotting the direction of flight and where to start looking to recover the rockets after impact. In these flights, we have a second set of ignition wires running to the rocket to first light the smoker before lighting the motor.

vented payload tube with smoke grenade inside, wooden nosecone

The alpha is a solid fueled rocket by what is called a micrograin propellant. The zinc and sulfur fine powders are one of the earliest solid propellants used in amateur rocketry and was invented by RRS founder, George James. The RRS standard mixture is 80% zinc and 20% sulfur by weight. Different ratios have been tried in the society, but this is our standard. Although a low performer among today’s solid propellants, it is inexpensive, simple to find, comparatively stable and quite fast once ignited.

zinc powder

sulfur powder

micrograin combustion demonstration at MTA

The zinc and sulfur powder constituents are separately measured and weighed then added to the 30-pound capacity metallic mixing drum. The mixing drum has internal metal baffles to speed up mixing as it is rotated on an electric motor driven rolling carriage.

metal baffled mixing drum with the zinc and sulfur, before mixing

electric motor driven mixing rolling carriage used for micrograin propellants

alpha launch 03-25-2017

The empty weight of the alpha is 3.65 pounds. Measured after propellant loading, the alpha fully loaded is 6.55 pounds. The calculated propellant load would be 2.90 pounds.

Specific impulse of the zinc/sulfur micrograin is quite low, 32.6 seconds. With an ideal combustion temperature of 2,600 degrees Fahrenheit, despite best efforts in packing, a significant part of the powdered propellant falls unburned out of the nozzle from the rapid acceleration even as the propellant is combusting. The rocket is supposed to operate as an end-burner with a 90 inch per second burn rate measured in many tests. Although most rocket groups no longer use the micrograin, the RRS maintains the tradition and it is hard to beat for simplicity.

The burnout time is about 0.8 seconds and burnout velocity is subsonic (roughly 600 ft/sec). Apogee for the alphas have been estimated at 5,500 feet based on the flight times (35 to 38 seconds) from launch to impact. Despite the long history of launching the alpha, some of these performance figures haven’t had many recorded measurements. The RRS is working on making systems to take better measurements, not only for the alpha, but for any of the rockets we build and test at the MTA.

If there are any questions about anything in this article or there is anything more you’d like to know about the RRS standard alpha, feel free to post a comment on our forum.

***