Volume 1, Issue 2 --- October, 1991

This is the electronic version of the Stratosphere Newsletter. Occasionally final editing is done to the actual layout of the newsletter and spelling checks, and other corrections may not make it into this edition. The content is complete (except for graphics).


September 28th Museum Launch - Another EOSS Success

What a perfect day it was to launch a balloon. At 9:34 AM, our Kasam 105 balloon with its payload lifted off into a clear, still sky. Quite a crowd of radio amateurs and general public had gathered at the launch site, right at the entrance to the Denver Museum of Natural History.

Channel 7 and Channel 9 captured the event for later showings on their respective news broadcasts. After soaring to 107,000 feet, the payload descended to a landing site only 20.6 miles southeast of the museum. In a record time of 19 minutes after touchdown, Ed, KA0ZAS, announced he was standing over the payload.

It took lots of teamwork to make this flight the success it was. Teamwork will continue to make the crucial difference in our projects. Merle, K0YUK and Dave, W6OAL, did their usual outstanding job getting the payload, parachute and balloon ready. Considering the number of new experiments carried on this flight, it was a wonder that more problems were not experienced. Once of the most successful experiments was the qualification of our new onboard computer, skillfully designed and built by Bob, W6ORE. This computer has opened up a whole new realm of future projects for EOSS.

Tom, N0KSR, organized and executed one of the most important functions of this project, the participation of a whole group of students who plotted and analyzed the performance of the flight via telemetry (see Tom's article inside this issue). The students also arranged the use of the museum's 8 inch telescope, through which the entire balloon flight was visually monitored, including the burst of the balloon!

Greg's, K0ELM, tracking and recovery team repeated their outstanding job as evidenced by the record time of payload recovery. The tracking team communications system performed flawlessly thanks to our good friends at the Colorado Repeater Association.

Meanwhile back at Denver Control, Mike, W5VSI, and Nate, KD0UE, led a team of excellent position plotters and net control operators. At the launch site, Marty, N0NTH, led the efforts to organize and set up the museum ground station while Tim, WB0TUB, served as the main EOSS Public Relations person.

To the fraction that were mentioned and perhaps even more importantly to the scores of team members who helped and were not mentioned, WELL DONE!

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"Humble" Telescope Project Takes Shape

Our next project will carry a solar telescope and camera to 100,000 feet where it will loiter for about 30 minutes, taking ultraviolet spectrum pictures of the Sun. Sponsored by students from CU, CSU and Green Mountain High School and several grants, including one from NASA, this project will be the most challenging yet for EOSS.

While the students will be responsible for the actual scientific payload, EOSS will build and integrate the RF telemetry and command (T&C) subsystem. In addition, EOSS will provide all launch, flight and payload recovery services required for this ambitious project. This week, a Raven 19K balloon will be ordered. This balloon will allow a payload weight of about ten pounds to the desired 100,000 foot altitude.

As the project takes shape for the December flight, it is evident that there remains much more to do and more help is needed. For instance, we still need a launch site. You can find out best what efforts are needed by attending the November membership meeting. Announcements for the project Preliminary Design Review and Critical Design Review will be made as they are determined.

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To view the logo that appeared in that issue of the "Stratosphere" click here.

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Pyrotechnic Payload Release Mechanism

Last issue this article discussed work towards a VOR-based balloon navigation system. That project took a back seat to setting up and running Denver Control for the last launch however, and it's just now back on the bench. The goal is to have it ready for the Humble Telescope in December. Watch this space in the next issue.

By now, most of you know that the FAA requires a commandable payload release for heavy launches, such as the Humble. The September launch carried an RC model servo mounted in the payload to do the job, but although the command was transferred, decoded and processed properly, the servo failed to operate. A postmortem suggested that the grease in the gearbox probably stiffened up in the frigid stratospheric atmosphere.

We also learned that the release mechanism should be mounted above the parachute to hold it open during ascent. The "sticky" parachute support designed to be stiff enough to hold the parachute up while the balloon line was attached to the payload, but loose enough to let go when the line was released wasn't quite stiff enough. The parachute collapsed over the payload early during ascent, probably due to unanticipated aerodynamic drag.

An important aspect of EOSS's activities, of course, is learning so this experience is a real asset in my eyes. The key here is to apply that learning to future launches. To that end, the 2nd Op, Mark, and I set out to develop a release mechanism which would exploit this experience. The design requirements included:

  1. Minimum of moving parts subject to sticking or seizing at -50 degrees F.
  2. Minimum weight to permit mounting above the parachute.
  3. Minimum weight to permit mounting above the parachute.
  4. Cascadable to permit redundancy, in case one fails.
  5. Electrically activated from 12 volts or less via the processor.
  6. RElease energy stored within the device to minimize power drain and activation wire size.

What came out was a free piston pyrotechnic device comprising three pieces of telescoping brass tubing about 1/4" diameter and 1 inch long assembled in a horizontal configuration. The larger diameter central piece attaches to the balloon line, and the payload is supported from the center of a yoke line, the ends of which are attached to each of the smaller outer tubes inserted into each end of the central tube. There is about .003" diametric clearance between the telescoping tubes.

Both outer tubes are tightly plugged with dowels swagged in place at the outer ends. One of them contains 100 mg of gunpowder, about 1/10 that in an ordinary shotgun shell. An electrically fired model rocket igniter is imbedded in the powder; its leads are insulated and brought out through the end seal. The igniter leads are soldered to a 14 foot length of 2 conductor #28 ribbon cable. The other outer tube is plugged end to end with the dowel to serve as a simple piston.

Since the mechanism is held together by lateral tension in the yoke, only a small spring is needed to keep in intact during prelaunch handling. Only one piston must be blown out of the center tube. Once that happens, the load will transfer to the remaining tube, causing the mechanism to tip far enough to let gravity pull the remaining tube out.

Initial tests were conducted with a great deal of caution against a possible violent explosion. The puny "pip" of a report once we got things working was disappointing, to say the least; cap pistols are louder. The most recent firing was conducted as a demo at the last EOSS membership meeting.

Static firing tests were done with a 6.5 lb weight on the yoke string with clip leads connecting a 12 VDC 5A current-limited supply to the igniter leads. Until we soldered the electrical connections, the igniter failed to fire in 2 out of 3 attempts. With good solder joints, we've had 100 percent success in five shots.

I suspect that poor electrical contact at the igniter clips may have a lot to do with the spotty success the model rocket folks have experienced.

Two igniter types were tested. The Estes device has a pair of tim-plated leads terminating in a short piece of nichrome wire coated with ignitable material; its DC resistance is 0.6 ohms. The Aerotech Copperhead igniter is made of a thin strip of mylar, copper plated on both sides with about one half inch of ignitable material on the end. It measured 6.0 ohms and is rated to fire from 6 volts, so it was more attractive electrically. But soldering the #28 leads to the two sides without melting the mylar proved too tedious and chancy. So we've opted to stick with the Estes device.

A single mechanism weighs 9 grams or one third of an ounce. The 14 foot #28-2 cable comes in at 12.5 g and adds 1.6 ohms to the circuit. Ignoring source resistance, firing the device will require 5.5 amps for less than one half second. The per-launch expendable include the center tube, gunpowder and one igniter with a total cost of less than 50 cents.

We plan to test the device at -50F by cold soaking it in a styrofoam ice chest chilled with dry ice. We'll hold off on that until some of the other payload devices are ready for cold soaking. Since the sliding parts are of the same material, and gunpowder carries its own oxygen supply, we don't expect any failures due to seizing or failure to fire.

Time and a design review will tell.

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September 28 Balloon Flight Data

Note: instead of reprinting excerpts of the log that appeared in the hard copy edition of the "Stratosphere", let me suggest you download the flight telemetry for EOSS-3. This file is a plain ascii text file enclosed in a ZIP compressed file. You can then examine the entire flight.

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EOSS and Education

When the amateur radio community embarked on a new endeavor as a means to find a diversion from the norm, EOSS was formed. As the club structure took shape, one prime aspect of each launch was agreed upon, education. Hence the slogan "Promoting Science and Education through Amateur Radio and High Altitude Balloons" was born. Education is a key word in that slogan. EOSS has dedicated the knowledge of each club member to students in the Denver area. We offer a practical application of the learning process that a student needs in understanding his or her school work, as well as some extra information to take back to class.

Our September 28th launch (EOSS-3) gave us the first real opportunity to involve a group of exceptional students. The Association of Astronomical Studies group, comprised of Explorer Scout men and women from troop 2268, stood up to be heard and they shouted. Within a week after our initial contact the students gave us an idea on payload stabilization that is under adoption as a future experiment. On flight day their graphs, made from real time data, were on display and the personality of their group was exhibited in excellent fashion. The debriefing report was highlighted by a complete breakdown of all the pertinent facts taken from the packet telemetry. The graphs were both computer and hand drawn. This report could give anyone the sense of knowing everything that had happened during the flight.

The important job of direction finding was supported by the Search and Rescue Explorer Scouts. They plotted along with our regular transmitter hunters and performed a job that aids their knowledge in finding lost people or a downed aircraft. Explorer Troop 599, an amateur radio troop, worked radio. What a perfect way they found to gain experience in ham radio. Our next QSO could be with these young students.

EOSS sees a future for these young people, but not before they saw a future in EOSS. Their plans are already in place to improve the telemetry logging and plotting techniques and the experiment ideas are limitless in their estimation. And now the tables have turned, the reality that we are learning from them is evident and a sharing of minds is bonding a solid youth/adult relationship. EOSS welcomes this as a start in our goal to be the provider of education.

With a firm start at hand, the work is just beginning. Capturing the hearts of other young people is still ahead. Standing by our commitment to educate must be reaffirmed on each new balloon launch. EOSS can grow into branches with the routs we've started and progress into a strong long standing force in the learning community.

EOSS gives its 73's to all the hard working students involved with the last balloon launch and we are looking forward to working with you again.

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Balloon Launch Station Needs

Most of the equipment used at the balloon launch site is fairly common, but there are several unique needs. According to EOSS needs second sources for the following equipment:

  • Portable Hi-Gain 2 meter and 70 cm antennas
  • Tripods (Azimuth/Elevation) for hi-gain antennas
  • Long (80+ feet) runs of coax with 259 and "N" connectors
  • ATV downconverters
  • Packet Stations (EOSS has a TNC now thanks to Gary, N0ERG)

People willing to risk lives (?) and equipment at upcoming launches please contact Marty. It is not necessary that you operate your equipment at the launch site, but your help would be appreciated and you would be honored.

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