Launching Rockets – Adventures at Spaceport America

by RRS member, Joseph Maydell

It was the Saturday of Memorial Day weekend. My flight was experiencing rough turbulence as it flew over the mountains on final approach to El Paso, TX. I was traveling to Spaceport America as a sponsor on four upcoming space-shot attempts. After collecting my luggage, I picked up my rental truck and headed north on the two-hour drive to Spaceport America. The only other way to access Spaceport America is to fly into Albuquerque and make the three-hour drive south. I had decided to fly into El Paso to save some time. Texas had actually been my home ten years earlier while working at NASA’s Johnson Space Center as an International Space Station (ISS) flight controller.

Getting through security earlier that day had been an adventure. My carry-on only contained mission critical hardware and was flagged for inspection. Everyone in the security line stared as TSA agents pulled antennas, circuit boards, a soldering iron, hot air rework station, trays of SMT (surface mount) components, wiring, ground control units, and weather balloon inflation equipment out of my carry-on. Everything was thoroughly swabbed for explosive residue and a lot of questions were asked.

The reason I had been asked to sponsor the next four launches at Spaceport America was because I had led the development of a new set of avionics for professional rocketry. It consists of a flight computer called the Eagle and a handheld ground control station. It was developed as part of a program for safely launching and recovering rockoons. It has the ability to launch, stage, and recover a multi-stage rocket as well as other proprietary features unique to rockoon flight. It has a very accurate barometric sensor and an aviation-grade inertial measurement unit (IMU). However, what space-shot teams find especially appealing is the global positioning system (GPS) receiver that can obtain GPS lock at any altitude.

The first launch was set for Monday morning at 6:00 AM. The rocket was a two-stage rocket built by Coleman Merchant from Princeton University as part of his master’s thesis.

It had the energy and propellant mass fraction to easily pierce the von Karman line (100 km of altitude). A group of cadets from West Point were also on site to assemble and align the launch rail on loan from Kevin Sagis, Virgin Orbit’s chief engineer. My responsibility, in addition to monitoring the health of the Eagle avionics package, was to launch weather balloons in the hours leading up to the rocket launch. This was critical for obtaining the upper level winds for calculating the firing solution. In the coming week, I would be launching a new type of radiosonde I had developed that would help lower the cost of obtaining upper level wind analysis prior to rocket flights.

Two rockets made by Coleman Merchant at the Princeton Rocket Laboratory

At 3:30 AM Monday morning, the team assembled for final launch preparations. Radiosonde operations were going well. Preparations at the launch site were also progressing smoothly. However, there were concerns that the brackets used to bolt the 1010 launch rail to the main launch rail structure could make contact with the carbon fiber fins on the booster during launch. This hadn’t been apparent earlier since the launch rail was still being prepared the previous day. The decision was wisely made to delay the launch. An hour later, all the brackets had been trimmed using a hacksaw.

Launch preparations would typically begin at 3:30AM

After aligning the launch rail with the final firing solution obtained from my radiosonde data, the rocket was armed. We all moved to Mission Control to complete final checks. This is when we discovered another technical issue. Since so many electronics, transmitting at various frequencies, were crammed into the nosecone, and since the nosecone was in such close proximity to the large launch rail structure, it was taking longer for the electronics to obtain GPS lock. We had done a radio-frequency (RF) test of the avionics package with all electronics running the previous day, including GPS lock testing, but not on the launch rail since it was still being assembled. It took about five minutes, but eventually all electronics with GPS receivers had GPS lock. After getting a “go” from White Sands and Spaceport America, the final countdown resumed and Chase Lewis, the West Point pyro-lead, sent the signal that launched Coleman’s rocket.

Coleman’s rocket accelerating off the pad at 46 G’s

Even from a mile away, it was difficult for the eye to catch it as it accelerated off on its way to space. Acceleration during boost reached 46 g. At booster burnout, the rocket was traveling Mach 2.4. A charge fired which separated the sustainer from the booster. A few seconds later, the sustainer engine fired and the sustainer once again experienced a peak acceleration of 46 g along its X (vertical) axis. However, as speeds approached Mach 3.8, the rocket became unstable and began to fly in a large upward spiral. Acceleration on both the Y and Z axis, which should ideally be zero, hit 42 g. Somehow the rocket managed to hold together before exiting the earth’s atmosphere at which point all acceleration loads went to zero. A few minutes later, the rocket re-entered the earths’ atmosphere under drogue. The booster had landed much earlier. It didn’t have any electronics and its recovery method was ballistic.

The booster recovery method was simple ballistics. Someone stumbled upon it a couple of weeks later.

After analyzing the data recorded by my avionics system (there were two altimeters by a different vendor but we couldn’t access the data), the leading theory for the upward spiral was inertial roll coupling. This is an aerodynamic phenomenon that can happen to both rockets and high-speed aircraft at a critical roll rate. Symptoms include divergence of angle of attack, large side-slip angle, and violent accelerations and loads. Air-frames with a low roll moment of inertia are particularly prone.

We still had one more launch window the following day. The decision was made to launch the second rocket and see if the problem repeated itself. No two rockets have the same roll rate due to tolerances in fin can and nozzle manufacturing processes. The hope was that the second stage would either stay below or above the critical roll rate during sustainer engine burn.

The launch window for Tuesday had also been scheduled from 6:00 to 10:00 AM. However, White Sands Missile Range informed us shortly before 6:00 AM that our launch window would close at 6:35 AM. This was unexpected and placed a lot of pressure on the team as we prepared the second rocket for launch. The rocket was armed just a few minutes before the launch window would close and we didn’t have time to allow the electronics to acquire GPS lock. The decision was made to launch with the hope GPS lock would be acquired during flight away from the interference caused by the launch rail. The booster once again flew flawlessly, but the sustainer never ignited. It coasted up to 19.7 km (64,600 ft) before coming back down under drogue. None of the electronics obtained GPS lock during the flight. The chance of us ever finding the sustainer and determining why its engine never ignited seemed unlikely. In the distance, we watched a missile soar into space over White Sands Missile Range. Now we knew why our launch window had been cut short.

I knew my avionics system had line-of-sight range, so in theory, as long and I could get my hand-held ground station high enough above the terrain, I would be able to receive telemetry. One idea I had was to mount my handheld ground unit to the top of the launch rail. We lowered the hydraulically-actuated launch rail and taped my ground control unit to the tip before raising it back up. The ground control unit was now sitting 40 feet above the desert. We lowered it a few minutes later and were disappointed to see that the ground controller had not logged any telemetry packets. This meant the rocket had to be in a gully or valley at a distance greater than a few miles. The next idea I had was to drive back and forth across Spaceport America along the expected flight path. I knew that if I came within a mile or two of Coleman’s rocket, I would receive packets and we could then locate the rocket. After driving for about an hour down some very rough roads, my ground controller started to log packets. An hour later we all hiked out to the sustainer which was lying in a valley. The sustainer was very close to where the booster had actually been targeted to impact as calculated by the upper wind analysis and firing angle solution.

On the drive back from the recovery area, I got a flat tire from an old fence-post nail. I tried to speed up through the cloud of dust from the truck in front of me to flag for help, but once my rim was hitting the ground I had to stop. I could have been out there for hours by myself if I hadn’t been able to break the lug nuts free with the inadequately short tire wrench I found under the truck’s passenger seat. Fortunately, I did make sure I had plenty of water, snacks, first aid kit etc., before heading out to try to find the sustainer.

So what went wrong on Coleman’s second space-shot attempt? It appears both altimeters rebooted when they fired the booster/sustainer separation charges. Because they were both rebooting, neither one fired the sustainer igniter. Since Coleman had only reached out to me two weeks earlier about integrating my avionics package into his rocket, my system hadn’t been approved by Spaceport America for initiating any flight events on his rocket. All it could do was go along for the ride while saving and transmitting flight data.

Coleman’s rockets had both flown amazingly well. The first space shot had come amazingly close to space. You could tell that a lot of experience and engineering analysis went into the design of his two rockets. I asked Coleman what he enjoyed most about the project:

“After spending months, coming out with a really nice final product that you are really proud of. Everything on this came out exactly the way I wanted it to. I don’t really have any regrets about how it was made.”

They truly were both impressive rockets. I asked Coleman what his biggest takeaway was:

“Spend more time on the electronics than you think you should. Don’t leave it until the last minute. It’s almost the most important part of the rocket. It’s something a lot of teams get wrong. They’re so focused on making sure it won’t rip apart.”

As an avionics systems developer, I couldn’t agree more. Coleman flew home and I had to start preparing for the next two space-shot attempts with Operation Space.

Operation Space was a project started by 18-year-old Joshua Farahzad. It was collaboration of students from multiple universities that had joined forces through the internet to design and build a space-capable two-stage launch vehicle. They had reached out to me a few months earlier about sponsoring their space-shot attempt and flying my avionics package into space on their rocket. I saw it as an opportunity to get additional testing and data on the Eagle system. Test it they did, in ways I could have never imagined!

The first launch attempt was scheduled for Thursday morning at 6:00 AM. However, assembly of the first rocket wasn’t completed until late Thursday afternoon. Parts designed and manufactured in different parts of the country didn’t fit together the way they were expected to fit. Last minute modifications were required including additional machining of fins and other critical components. The avionics bay was completely redesigned on Wednesday and rebuilt on Thursday. The first deployment test didn’t occur until Thursday evening.

Friday morning, after 48 hours of round-the-clock work, the first rocket was finally on the launch rail. Chase once again sent the signal that ignited the first stage. Everything went well until the sustainer engine ignited. It was obvious from the smoke trail that the sustainer had gone completely unstable. Once it landed, we lost all communication. Our search in the desert for the sustainer at the last received GPS coordinates proved futile. At the time the leading theory was that the sustainer had lost one of its fins.

The second rocket was launched Saturday morning. Its flight path also went unstable about two seconds after sustainer ignition. It also abruptly stopped transmitting all data once it landed. Once again, we went out to the last received GPS location. We never found the sustainer. However, to our surprise we did find the avionics bay with a short length of parachute tether and a wad of carbon fibers from the nose cone. When it hit the ground the battery tray inside broke loose and crushed my avionics system. Most of the SMT components had popped off the motherboard. Fortunately, the avionics bay was in a clearing only a few feet from where I had received the last packet during flight. Otherwise, we may have never found it since there was a lot of thick brush and we were all looking for a large rocket. We could have easily overlooked the small avionics bay hidden in a thicket. This is probably what had happened when we searched for the first sustainer the previous day. We had been warned not to poke around in the bushes because of the rattle snakes. We hadn’t considered looking for something as small as an avionics bay.

Chase Lewis inspecting the interstage of the Operation Space rocket.

Once we returned to Mission Control, I was able to solder the SMT memory chip to a good Eagle motherboard using my hot air rework station. This made it possible to download the flight data. This is what the flight data revealed: two seconds after sustainer engine ignition, the rocket started to go unstable and then it drastically altered its angle of attack. One tenth of a second later, the avionics bay separated from the rest of the rocket. It did a 180-degree turn and coasted backwards to an altitude of 15.5 km (51,000 ft) with the parachute tether trailing behind it before coming back down. Most likely, aerodynamic loads at Mach 3.5 caused the carbon fiber nosecone to fail. This released the drogue which was housed inside the nosecone. The force of the drogue opening and shredding broke the altimeter bay free from the rest of the rocket. Later, I learned that the nosecones had a major manufacturing defect. There wasn’t enough time to manufacture new nosecones and those who knew about the issue had hoped for the best.

The avionics bay from the second Operation Space launch as we found it. Notice the black wad of carbon fiber presumably from the nosecone shoulder.

The Operation Space Team put in a lot of effort to reach space. It was disappointing to see them only reach 15.5 km. However, I have no doubt that with more experience, an improved design, and better preparation, they can be successful. They had a lot of fun, worked well together, and certainly learned many lessons. One in particular that I would like to emphasize:

You should never underestimate the amount of time, effort, and diligence required for successful space flight. Among other things it requires thorough engineering analysis, diligent acceptance testing of all manufactured parts, exhaustive vehicle integration testing, and well-written operation procedures.

It was now Saturday afternoon. After downloading the flight data, I left Spaceport America with just enough time to drive back to El Paso and catch my flight. I only had one concern. With all the work helping Operation Space machine, wire, assemble, test, and prep their two rockets, I never did get my flat tire fixed. I was on my cellphone telling my wife how excited I was to see her and the kids that evening when a warning light went off. My adventures were not over: I had another flat tire!

About the author

Joseph Maydell has over a decade of both space flight and high-altitude ballooning experience. He is a former ISS Flight Controller and NASA spacecraft systems instructor. He has started multiple successful aerospace businesses and is passionate about inspiring students to pursue careers in space exploration. If you have any questions or comments, you can reach me here.

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!


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.



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.