A multi-staged vehicle with peak sensor

The following is a report written in February of 1985 by RRS members George Dosa and Frank Miuccio. The report details a three-stage rocket with several illustrations. For the sake of preservation, this report is reproduced in this article.

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A MULTI-STAGED VEHICLE WITH PEAK SENSOR
by Frank Miuccio and George Dosa

The purpose of this report is to document the building and testing of a three stage vehicle with a peak sensing device. Short betas were chosen for the 1st and 2nd stage and a short Mark Series for the 3rd stage. The peak sensor will be a photocell intended to detect the change from sky to ground and activate a parachute system. The 2nd and 3rd stage will be fired using inertia switches and a unique 3rd stage interlock system. A minor test will be of a passive sound emitter on the 2nd stage.

Also, (in this project) going to see if white, black or stainless is the best color to see (when spotting the rocket).

NOTE:
The report has sketches of the individual stages of the three-stage rocket and their interconnections.

first stage, shortened RRS standard beta, micrograin

2nd stage – shortened standard beta, micrograin rocket

3rd stage – Mark series rocket

556 timer chip, schematic

Sketch of the 3-stage rocket design

Second to third stage coupler design – sketch

Photo of the 3-stage rocket design

[more images and details to come, work in progress]

—- —-

For questions, contact the author, Frank Miuccio.
vicepresident@rrs.org

or the RRS secretary
secretary@rrs.org

Report on timer circuit design

This is a posting of a report written by our current society vice-president, Frank Miuccio, many years back. It has been reproduced here on our website for preservation. A hard-copy revision of the document will be published in the society archives. The original date shows it was Revision A, dated March 9, 1989, nearly 30 years ago. Some of the figures mentioned in the text are missing (until we find them again) and others have been remade for clarity.

Frank’s timer report, original cover from 1989

In reading the report, you can see that the technology of some aspects of the design are no longer commonly practiced, such as the use of mercury switches and mechanical relays, but the circuit principles are still sound. I have noticed that the model rocketry community, such as our friends at Rocketry Organization of California (ROC), have made great strides in timer designs.

Rocketry Organization of California

There are many commercial suppliers across the country that make a range of simple and complex designs that are reliable and affordable. Some products can be bought ready to use in your rocket application.

Eggtimer Rocketry

Also noteworthy is that lithium polymer battery technology is taking over from the conventional 9-volt. This doesn’t come as a surprise to many, but certainly worth mentioning. Some people still use the old battery types, but there are many smaller and very powerful options in batteries thanks to the growing airborne drone community.

It is the society’s intention to show this report to inspire our members today to expand upon the work done before. Many effective timer circuits are commercially available, but years before, to have such a device required a bit of ingenuity combined with plain trial and error. Enjoy!

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TIMER CIRCUIT REPORT
by Frank Miuccio, RRS

On June 25, 1988 at the Mojave Test Area (MTA), a single stage micrograin (80% zinc, 20% sulfur) rocket was flown with a simple payload that anyone can build. The payload consists of a timer that was set for approximately 18 seconds, a parachute, and an ejection mechanism. The timer was used to eject a parachute 18 seconds after burnout and was designed to incorporate the least amount of components. The timer consists of 4 components, 2 batteries and 2 safety switches and a mercury switch.

The main objectives of the payload were the following:
(1) To verify that the ejection mechanism (shown in Figure 1A and 1B) works properly. The ejection mechanism was designed and built by a member of the RRS.
(2) To verify that the mercury switch activates at burnout and stays on for the time constant.
(3) To verify that the timing circuit (shown in Figure 2) functions properly and can withstand the flight environment.

The flight was a success. The parachute ejected and was spotted by the tracking crew, who were located approximately 1000 feet away from the launcher. All three objectives were met with a positive result. A few shortcomings were noted. The parachute, 24 inches in diameter, drifted the rocket north-east and the rocket was lost. Also, the color of the parachute was white which was a problem in spotting.

Figure 2: Timer Circuit

The timing circuit has been used three times.

The first time was on December 28, 1986 on a two-stage rocket. It was used as a separation time delay for the second stage. The timer was installed in the uppermost section of the first stage motor prior to fueling. It primary function was to ignite the second stage 2 seconds after burnout of the first stage. During fueling of the first stage, a problem was noted. The timer was being exposed to extreme bouncing due to our fueling technique.

The next time, the timer was used as a stage delay was in December 1988. The circuit was packaged in a separate module which would be installed after fueling of the rockets.

The third attempt wasn’t as successful as the other two. The timer failed to function. A possible culprit could have been one of the safety switches which was installed backwards. The switch was installed with the “ON” in the upward position. This creates a problem since the acceleration (from launch) could force the switch in the “OFF” position (downward).

The timer looks promising that it can cover various time constants. To determine the desired time the values of the capacitor [C1] and resistor [R1] can be varied. One can calculate the values needed as follows in the formula below.

Time delay = [C1] * [R1] * 1.10

The following steps are used to achieve the desired time constant when building the circuit:

(1) Wire and/or solder in the circuitry except the resistor [R1] and capacitor [C1].

(2) Chose a value for the capacitor [C1] and permanently install it in the circuit. Note that the value needs to be in the microfarad (uF) range. In this report, a 22 uF capacitor was used.

(3) Calculate the value needed for the resistor [R1] by using the time delay formula. Note that this will only give you an approximation of the actual time delay. The resistance will be in the kilo-Ohm to low mega-Ohm range.

(4) Adjust a potentiometer (also called a “pot” or a “trim-pot”) to the calculated value (Pin 1 to the wiper) and temporarily connect the pot in place of the resistor [R1] (pin 1 to the wiper).

Potentiometer (adjustable resistor) next to a fixed value resistor

(5) Test the timer to find out if you need to adjust the pot by increasing or decreasing its resistance. Note that if the timer delay is longer than the desired time constant, decrease the pot resistance. Conversely, if the timer delay is too short, increase the pot resistance.

(6) Adjust the pot as needed and repeat Step 5 to get the timer delay correct.

(7) Measure the resistance value of the pot (Pin 1 to wiper) with a voltmeter then find and permanently install a fixed resistor of that value in its place [R1]. In this report, a value of 732 kilo-Ohms was measured when the circuit met the desired time period. A more common size of resistor is 750 kilo-Ohms which is close enough.

(8) Test the timer to verify the accuracy of the time constant.

(9) Once the circuit is tested and complete, surround and enclose the timer circuit with RTV. This is needed due to the G’s experienced during flight.

GOOD LUCK!

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Editor’s notes:

I have found that in modern times (circa 2018) electronic component stores are not as common as they once were. RadioShack is still in business, but they are not the big company that they used to be. I have had good luck in getting what I need from a local store in my neighborhood in Westminster, CA (Orange County). They have nearly everything an electronic hobbyist could want including lithium polymer batteries of all sizes.

JK Electronics in Westminster, CA

JK Electronics – Westminster, CA

Ordering from online suppliers (DigiKey) is always an option, but the catalog information posted by the mainstream suppliers can be difficult to interpret if you are not an electronics expert. Also getting small quantities (less than 100 units) can also make ordering excessively expensive when the shipping costs far more than the handful of parts you are ordering. Amazon and Ebay can be a helpful resource, but the buyer must be aware of the specifics of exactly what you need. Always do your homework, consult the advice of experts and you will be more sure to get the components you want.

Also of historical note, the K1 RELAY element of Frank’s timer circuit used a W107DIP-5 (5-volt) mechanical relay made by Magnecraft Electrical Company of Northbrook, Illinois. Frank had the actual catalog from Magnecraft in his report so I took a photo of the relay he had selected.

Magnecraft Electric Company, original print catalog

In this photo to the left, you can see the circuit diagram of how this Dual In-Line Packaged (DIP) reed relay is connected. This 107 model is a normally open (NO) single-pole, single-throw (SPST) type of device and contact rated for 10 VA.

Magnecraft W107DIP-5 catalog specs and circuit diagram

I’m not sure if Magnecraft Electric Company is still around, but a modern update to the timer circuit design would likely use a solid-state NPN type of bipolar junction transistor (BJT) instead of the mechanical relay. This exercise is left to the individual to pursue, but not in this article.

NPN type of Bipolar Junction Transistor (BJT)

example of an NPN-type of BJT, rated for 1-watt, connections are labelled

It is important to make sure you know which pin or connection is which. The polarity of the circuit element you are using can be critical. For example, the longer lead on a capacitor is often the positive (+) one. The case on a capacitor should also have a negative sign (-) or a dash symbol to indicate which pin is the negative one. The circuit diagram that Frank included in his report has been careful to show these important details on polarity.

Spark Fun website on electrolytic capacitors and proper polarity

One should also note that very often the pins on a chip are numbered in specific sequential pattern, but the circuit diagrams often don’t follow these and simply call out the pin location by number only. I have put the pin diagram for the common 555 timer chip below to illustrate this important distinction between a physical layout and the schematic which doesn’t always match the physical locations.

555 timer chip with the actual pin locations, notice the notch at the top to show where “1” starts

Just to give a little more detail on the mechanical relay that Frank used, I have re-created the pin diagram from the Magnecraft catalog picture showing the layout of the 14 pin connections. You’ll only need four of these connections (2, 6, 8, 14) as seen in Frank’s circuit.

Pin layout for reed switch type of mechanical relay, Magnecraft WR107 DIP-5

Also, a word about the timer delay formula is that it is based on the basic RC circuit type that has an exponential rise relationship once the circuit closes and starts. For simplicity, this formula just assumes a fixed 1.1 ratio to relate the product of the capacitance and resistance value into the predicted time delay in seconds.

Sample calculation of the approximated time delay with capacitor and resistor values converted to seconds

It is important to understand that this is only an approximation and actual experiments are required to be more precise. Each of the lines and connections adds a little bit of variance to the actual delay time you will see and it’s hard to know exactly what this is without testing. Frank’s instructions go into how to do this by first using an adjustable resistor (potentiometer / pot / trim-pot) to measure what resistance you need, then you go get a fixed resistor to install at the end. This way, you can adjust for some of the real-world effects of your connections and verify that your timer will give you the fixed time delay you want. Also remember when buying capacitors and resistors, you will have to buy them in the sizes that are common. Even with the modest precision of these devices (+/-10% on capacitors; +/-5% on resistors), you can still get very close to the time delay you want and these parts aren’t very expensive.

Some people will put in an adjustable resistor in their circuit designs which is fine if the pot can stay tuned on the exact setting you want and you have the access to make adjustments if needed. Typically, you don’t have good access once the payload is installed on the rocket, so this is why this design has chosen to permanently attach a fixed value resistor after some testing to validate the operation.

Lastly, I should make a note on the use of RTV for “potting” or encasing the circuit. Room temperature vulcanizing (RTV) silicone rubber is a liquid compound that usually comes in small tubes and bought in automotive shops (e.g. Autozone) that after it dries will make a rubbery solid. This final step of encasing your circuit in a flexible but firm solid is considered by some to be necessary to secure the timer circuit from deflecting and possibly malfunctioning under the high acceleration experienced in the rocket flight.

Others feel that this step is not necessary. It has also been said that RTV is corrosive to electrical contacts and should not be used. In any case, you must make a structurally robust circuit that stays put, doesn’t break and will protect your connections from accidentally shorting against the interior metallic walls of your rocket parts (if you have them). The high G-loads from a micrograin rocket’s acceleration are not trivial. Proper packaging your payloads is a very important consideration in rocketry.

The method of successfully potting a circuit in RTV is probably worthy of a separate discussion. It is wise to have all of your leads sticking out of the drying potting compound you’re using better it sets otherwise you can’t connect the right parts when the mess is dry. It sounds obvious, but wait until you screw it up?! 😉

Thanks for reading. Look to the RRS.ORG for more articles on different rocketry subjects past, present and future.

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