Tag Archives: MTA

February 2018 meeting

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The RRS held its monthly meeting Friday, February 9, 2018 at the Ken Nakaoka Community Center in Gardena. After reading the treasury report, we proceeded with the meeting agenda as listed on the “Forum” earlier this week.

Attendees at the 9-FEB-2018 RRS meeting

The RRS was glad to welcome new student members Jack and Brayden who come from the former Chaminade High School Rocket program. The RRS will be supporting their project to launch a boosted dart ultimately to an altitude of 150,000 feet or more. This work fits nicely into the RRS goals with the SuperDosa project and Jack and Brayden have made a lot of progress already thanks to the help of their sponsors and supporters including the RRS’s own Dave Crisalli. Last year, Jack and his team had a successful motor grain test at the MTA and they are looking to build upon this success for an even larger hot-fire test. RRS as a 501(c)3 educational non-profit group is glad to support our members.

On this Friday, the RRS has started the first of five classes with our third group of students from Florence Joyner Elementary School in Watts in conjunction with the LAPD CSP program. The program will seek to schedule a tour of the California Science Center at some point and the five session program will culminate in a launch event at the RRS Mojave Test Area (MTA) on March 24, 2018. The launch date has not yet been confirmed so please look for updates on the “Forum” portion of this webpage.

On this same subject, Michael has been working with his contacts at Redondo Union High School to find a way to begin an educational program with the RRS. The RRS is glad to work with new and returning schools in our educational programs. For more details, contact the RRS events coordinator, Larry Hoffing. events@rrs.org

On our third agenda topic, we talked about the progress made to date for the 75th anniversary RRS symposium. We have had great responses from our prior exhibitors and speakers as many are returning for this year’s event on Saturday, April 21, 2018. Our event will have speakers and exhibitors from the aerospace industry, government agencies and academia. The speakers slots have filled up fast so we hope to have our final confirmations given to us soon.

Frank has made the first flyer for this event and we encourage everyone to download a copy and share with everyone interested in attending this event covering topics of professional and amateur rocketry.

first flyer for the RRS 75th anniversary symposium

Frank has said that there is still much to do in preparing for the symposium. This event will likely be bigger than last year’s so we will really need our membership to pitch in and help make this year’s 75th anniversary a success. Weekly phone teleconferences will begin in two weeks. Frank will notify people of their assignments and we will discuss progress at these meetings.

Our fourth topic on the agenda discussed the progress I have made with the parachute recovery system I have built for an RRS standard alpha rocket. We launch many of these at our school events at the MTA and even with our membership making their own. I would like to see more of our members and high schools working with making payloads for the alpha. Given the small size of electronics these days, there are many more possibilities for flying instruments and recording data.

parachute and tethered nose cone for RRS standard alpha rocket

My time was very limited as the meeting was running late and I was only able to show the key parts of the parachute system still in build. Chris Lujan showed me some better knots for securing my nose cone and tether line to the internal bulkhead. I also showed the 3D-printed plastic umbilical port that Richard Garcia kindly built for me which will make switching on RRS alpha payload much easier if they use PVC payload tubes. I will compile more details soon and if this subject is still of interest, I can elaborate more at the March meeting.

Modified 555 timer chip with solid state relay replacing a mechanical relay. Umbilical part in the upper left.

I have also been working on a horizontal thrust stand built to test RRS standard alpha rockets. This would allow members to record thrust from the S-type load cell donated to us by Interface Force Inc. of Arizona. All of the structural members have been cut, but the adapter pieces need some changes to make a simpler connection. Thanks to Osvaldo for improving my load cell adapter design.

RRS horizontal thrust stand parts with S-type load cell

For our fifth agenda topic, Frank Miuccio, inspired by the device built by the Space and Missile Systems Heritage Center (SMC) of Los Angeles Air Force Base (LA AFB) in El Segundo, made his own little rocket air launcher. This simple tool takes an air pump to compress the sealed interior space of PVC piping behind a simple sprinkler valve.

Frank’s mini-rocket air launcher using a car-tire pump

Once inflated and everyone is at a safe distance away, the rocket is slipped over the angled launcher tube and is fired by releasing the valve and reservoir of air pressure behind it. Very simple in operation, it is quite fun to play with and we think the kids in our educational programs will think so also.

RRS treasurer, Chris Lujan, holds a 12-inch plastic rocket launched from the pump driven air launcher; Larry and Frank discuss

As the last agenda topic, Richard had mentioned that the modifications to his cryogenic methane dewar were complete and that the vessel was back at the MTA. As we were out of time, Richard can explain the details more at the next meeting in March.

The meeting adjourned but several of us watched Frank and Chris test fire the small rocket air launcher that Frank had built from Home Depot parts and a battery powered car tire pump. Despite the darkness of night, we were able to recover these small 12-inch vehicles aided by the inclusion of a blue LED in the nose. We had more than a little fun popping these little rockets as high as 100 feet.

If there is anything I have missed or misstated, please let me know:
secretary@rrs.org

Our next meeting will be Friday, March 9, 2018 at the Ken Nakaoka Community Center in Gardena. See you there!

August 2017 meeting

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The RRS met for our monthly meeting Friday, August 11th, at the Ken Nakaoka Community Center in Gardena. We were well attended, but got a late start. After the usual reading of the treasurer’s report, we began the meeting with the first agenda topic.

Frank has been talking with several groups interested in doing alpha build events including the LAPD wanting to serve another set of students in another housing project in Watts. The Watts event at the MTA was very successful and we discussed what went well and what could be improved.

We discussed getting a shared server for running RRS members to run applications related to rocketry. Frank and Chris are looking into options but haven’t found anything yet. Many of us use cloud services to store our files, but the RRS ought to discuss data storage options that can be better accessed by our membership. This topic is on-going.

The RRS history project continues. We received a set of RRS newsletters from Bill Claybaugh (thank you, Bill!). Richard Garcia continues to scan the newsletter stacks he has. We are still interested in getting reports, newsletters and anything else relevant to our history.

Bill Claybaugh was also kind to donate one of his 3-inch nozzles with a graphite insert to the society. In time, we will receive Bill’s propellant test rig which I look forward to examining and using at the MTA.

Bill Claybaugh’s three-inch nozzle

side view of three-inch nozzle with graphite throat

The RRS has made contact with our founder, George James, and some of the other early members of the society. We hope to schedule interviews and help to document as much of our history as we can in advance of the 75th anniversary symposium, April 14, 2018. The RRS is working on a list of our officers going back through the many years to the beginning starting with George James. We appreciate the help we’ve got so far, but there’s still a lot of work to do.

The next launch event at the MTA will likely be in the latter part of September. Some of the potential events with schools will be in October. There is significant interest in the RRS having a launch event for the several members interested in launching their own alphas. Many of our new members, Alastair, Bill, Angel and now Drew, have expressed interest in launching their own alphas. Myself and Larry will likely try to put something together as I continue to work on the parachute system for the alpha.

The council will update our membership once the next launch event at the MTA can be organized and set.

We had hoped to look at the footage from the keychain camera mounted to the fin on LAPD’s alpha rocket. The camera was recovered and the data was good, but Osvaldo did not have the opportunity to edit the footage. Alastair also had some video footage he took from the 7-22-2017 Watts launch event at the MTA, but he was still editing. We decided to push this item off to next month.

We discussed timer chips and other methods of switching on payloads right at launch. I brought my wood block breadboard and worked with Richard to resolve some issues with my circuit not firing. Osvaldo built a cotter-pin based spring-loaded switch that he mounted inside a segment of the alpha payload as an example. The society continues its efforts to learn more about what works with payloads and what doesn’t. I discussed my idea to attempt a flight speed sensor with a pair of barometric pressure sensing chips. Osvaldo said he’d drill a hole in the tip of an aluminum nosecone for the stagnation port.

We adjourned late at 9:22pm. In the future, we need to watch the time spent on each agenda topic. I would suggest we bring a simple battery-powered 6-inch wall clock into the meeting room so all people can more easily keep better track of time without pulling out their phones.

The topic of issuing membership cards and developing a better system of tracking dues collections was not addressed and will also be pushed to the next monthly meeting.

Our next meeting will be Friday, September 8, 2017.

If there is anything I missed or misstated, please let me know.
secretary@rrs.org

RRS standard alpha rocket

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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. Discover the power of a good night’s sleep! Say goodbye to restless nights and hello to peaceful dreams with Ambien, your trusted sleep ally.

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. While ativan can bring relief, it’s essential to use it under medical supervision due to its potential side effects and addictive properties. Your doctor will advise you on proper dosages, potential risks and benefits, as well as alternative treatments or lifestyle changes that may be beneficial.

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. Remember, mental health matters and seeking treatment is a sign of strength. Take charge of your well-being with xanax.

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.
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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.

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