I still don’t have a reliable setup, but some recent changes I made to my cloud chamber have resulted in this very satisfying display of subatomic contrails. Here are a couple of recordings. The first documents when I was stunned to see multiple concurrent trails and I called for Poldi to witness it.
“Hey Poldi!” (expand to see what we were excited about).
The second video is a sustained view for several minutes, placed to background music, to mesmerize those of us who are susceptible. Think about it. This is a visual representation of the radiation that is all around us! Expand to full screen for best effect.
If you’d like to read about how I got here, the previous post describes the project of building the cloud chamber.
I had the fortune of starting my career at a signature moment in the computer revolution—the microprocessor had just been invented and it was rapidly being incorporated into the many various tools that leverage our human intelligence. Among those tools are the instruments we use to measure the world around us.
Up until then, instruments that required some amount of interaction used very direct physical interfaces: knobs, buttons, and dials for input; meters, gauges and chart recorders for output. They were wired in complex arrangements but had limitations in how complex their measurement could be.
The microprocessor changed this by providing an inexpensive logic element that could monitor and manage much more complex channels of interaction: switches, keypads, digital displays, sensors, data terminals, printers, transducers and actuators were now on the list. The opportunities to make better measurements than ever before, or measurements that simply could not be performed previously because of their complexity, now became possible. As a result, there was a renaissance in instrumentation.
I was recently presented with a gift from a young family member. He thought I would get a kick out of a “NASA Mission Control Computer Chip.” And I did, even more than he could have imagined.
I suspect that an entrepreneur had acquired some decommissioned NASA equipment and found a way to monetize it by stripping the chips out of their sockets, packaging them, providing a backstory, and selling them to nostalgia seekers, space history nerds, and millennials looking for novel gifts for their boomer relatives. This is not a criticism. This is a fine way to keep these components from ending up in a scrap heap headed to a landfill and instead make a final tribute to a remarkable human project.
To someone born after the Apollo moon landing program, the artifacts of those times must seem just that: obsolete artifacts. There are still computer chips, of course, but they are smaller, more complex, and come in highly sophisticated packages that look nothing like those of that era. Just look inside a cell phone.
My pleasure at receiving this gift was not just the experience of once again seeing a 16-pin DIP (“dual inline package”). It was also the recalled memories of designing circuit boards with them in the 1970s. At that time, I worked for a small company that made geophysical instruments. We had employees, mostly women with fine motor skills, who hand-assembled these DIP packages, along with other electronic components onto circuit boards, soldering them into place and wiring the boards into the instrument chassis. I contributed to the design of those boards by figuring out how the digital chips needed to connect to each other.
I was curious what exact chip from mission control I had received. When I looked closely, I could see the part number stamped on its top: MCM 4116 BC20, along with the manufacturer’s logo and date code (8122- the 22nd week of 1981). This part number seemed familiar to me. I looked it up and found it to be a memory chip with 16,384 bits. Now even more memories flooded in! This was a milestone memory chip in its day!
And it was the very chip I had used in one of my first memory board designs. I was quite intimidated because it was in a class of memory called “dynamic,” which was a euphemism for memory that forgets rapidly. In order for it to not forget, it needed to be refreshed. And I had no idea how to do that.
There are now many different technologies used to store data, but in the 1970s, there were only a few, categorized by type. Read-only-memory, ROM, had data permanently etched in place. It was good for storing data that would never change, like program code and conversion tables. The other major memory type was, and is, random access memory, RAM. This is memory that can be written with any data pattern, and accessed later, in any order (randomly) to recover it. There were two types of RAM: static and dynamic. Static memory, SRAM (pronounced “ess-ram”), would retain its data state for as long as it was powered on. Dynamic memory, DRAM (“dee-ram”), as mentioned above, would fade away with time, measured in milliseconds.
Why would anyone bother with memory that didn’t remember much?
Capacity. It was possible to fit much more memory in a DRAM chip than an SRAM chip. This was due to the additional complexity (transistors) needed for the static memory cell to stay, well, static, and hold its value. In contrast, the DRAM cell comprised a single capacitor, a place to store electrons. As a result, DRAM chips had 4X the capacity of SRAM for the same size or cost.
Unfortunately, the electrons on the DRAM capacitors had the tendency to leak away. This can be compensated for by sensing the memory value before it fades, and then re-charging the capacitor to its original state. It is a lot of overhead to visit every memory cell, read it, and re-write it before time runs out, but memory was valuable, and the effort was deemed worth it.
I knew little of these underlying details of memory chips in 1977, but I did know that it was easy to design circuits using SRAM chips. Connect them up, and they seemed to “just work”. On the other hand, on hearing about the onerous demands and complexities of using DRAM, I was scared. It just seemed too complicated, and I didn’t think I knew enough to take it on. It might be really hard. So I resisted this project.
Eventually, I had to face the task. I obtained the data sheets and application notes for the DRAM chip I would be using: the 4116, just like the one recovered from mission control. In the days before the internet, this involved procuring the published data books from the parts vendor. I then dove into learning about dynamic memory and how to manage it.
I learned the basics that I described above, and I also learned that I didn’t have to read and re-write every cell. The chip could help out with that task. Memory was arranged in rows and columns of cells. If I could access each row, the chip would take care of refreshing all the columns in it! Other chips were available to invisibly help with accessing each row.
As I learned how to make the control circuits keep the memory refreshed, I realized that my fear had been unwarranted. This wasn’t so awful. It was not over my head. I knew how to do this!
I would eventually become skilled enough to use DRAM chips in high-end color displays, sometimes devoting many bytes of memory for every pixel, an unheard-of extravagance made possible with the increasing capacity and dropping costs of DRAM.
I took away a lesson from all this. Something may seem incredibly complex, like the ubiquitous example of “rocket science,” but a complex field is not necessarily a difficult field, especially to those who are in its midst and have learned along the way. As one learns a little, the next questions to ask become apparent and guide you to learn more.
As a result of this experience, I became less hesitant about taking on new and unfamiliar challenges. Confront the challenge and the results are better, and you are better.
One of the works that came out of TAT Productions in the 1960s was an educational filmstrip. “Filmstrips” were a popular and common educational resource in the days of ditto machines and library paste. They presented a sequence of images that were explained by the teacher to convey an important topic in the class.
The project was for a history assignment. I don’t remember the exact topic, but I remember being pleased that I had access to a special-purpose camera. The camera club, sponsored by our chemistry teacher, Mr Van Wyk, had equipment available to its members, including a “half-frame” camera. This enabled and inspired us (Terry and Thor, the principals of TAT Productions), to make our own filmstrip. Terry did the heavy lifting, gathering the visual sources that we would include in our filmstrip, and I provided the technical effort of operating the photographic copy stand and the lighting. We had a broad range of materials and worked to present them in a coherent explanatory sequence. I arranged the camera position, lighting, and exposure, to capture each item in its best representation. We both worked on the script to accompany the filmstrip presentation.
When we developed the film and spooled it up to load into the filmstrip projector, we discovered a “production error”. Most of the images had been taken in “portrait” aspect, taller than wide, but the filmstrip projector was designed for frames in “landscape” mode. This resulted in the class having to turn their heads to make sense of it. We soon figured out that someone could turn and hold the projector on its side while advancing the film. And some poor student had to do this whenever our history teacher inflicted our production on his subsequent classes.
TAT productions went on to undertake more projects, forgettable to most, but unforgettable to us, including “The Commercial”, “The Tell-Tale Heart”, and “Images”, all featuring fellow students and our teachers, conveying truly important messages to our classmates of those times.
Today of course, the classroom projector would automatically rotate the pictures to match their aspect. I suspect that somewhere, in the same spirit that created TAT Productions, there is a modern-day collaboration between students making TikTok videos for their history class assignment. They will probably also encounter “production problems”, but it won’t be something as simple as getting the aspect ratio wrong!
I would not stay around to see the mission end. Once the instrument was airborne, there was no further purpose for our lab in the airplane hangar, and my job title became moving man and trucker. The packing went ok, but on the way home I ran into another weather condition: severe thunderstorms. Driving the broad-sided truck east on Highway 12, it was a challenge to keep it in my lane. The rain slowed me down but fortunately, the wind was not enough to blow me over. I thought about how fickle the spring weather in the Midwest could be. After weeks of steady wind, the short window of calm that permitted a balloon launch was followed by a gale force blast, perhaps to compensate and bring the average wind speed back up to the South Dakota standard.
Our next opportunity finally arrived two weeks later. Having been through two “dress rehearsals,” we knew what to expect.
The procedure was to lay out the balloon on a protective tarp on the runway. The topmost section of the balloon, a small portion that would become the “bubble”, was fed through a retaining “spool” and folded back on itself. The top section had two tubes, made of balloon material, through which helium would be fed, inflating the bubble, which would gradually ease up from the tarp, eventually becoming large enough to lift itself off the ground entirely, with only the spool and the tension from the uninflated remainder keeping it in place.
While the wind blew, the various research groups and the launch crew prepared and tested their experiments and rigs, like fishermen mending nets to get ready for the next big catch. At the end of each day we would check the wind conditions and then give up for the day, leaving the airport to seek dinner and retire to our rooms at the Super-8 for a few hours of personal time and sleep before repeating the routine the next day.
Cosmic ray instruments are complex and it seems there is always something that needs adjusting or fixing or calibrating, and then testing and confirming and re-calibrating. This is what consumed our time while waiting for the wind to die down. And it is a good thing to have had that time to do those last ground tests, because we encountered a troubling condition—an intermittent false trigger.
Scientific balloon launches have been part of NASA’s mission for over 30 years, but in 1977, they were conducted by NCAR– the National Center for Atmospheric Research. NCAR maintained a balloon launching facility in Texas that had all of the equipment and resources to support experiments like ours. Unfortunately, Texas was too far south for our experiment. Instead, we would be operating from makeshift facilities in Aberdeen, a town of 25,000 in an area of South Dakota that offered low population, but enough infrastructure to meet our technical and launch requirements.
There was a regional airport outside of town, and an airplane hangar was provided to house our laboratory field station. We were not the only researchers, however. Groups from other universities were also trying to measure the properties of cosmic rays. We each had a section of the hangar to set up and prepare our experiments for launch. After packing up our instrument and all the essential support equipment from our 4th-floor lab in the Physics building into a rental truck and driving a day west on Highway 12, we arrived in Aberdeen. It took us several more days to recreate an operational cosmic ray field lab in the airplane hangar.
This is the beginning of a series of posts that describe the launching of a scientific balloon experiment in 1977. The story was reconstructed after encountering some old photos from that event. Reminiscences can run rather long, so I have partitioned it into more manageable segments. I hope you enjoy this snapshot of the scientific and cultural times of the 1970s.
Background
While attending the University of Minnesota, one of my part-time jobs was as a lab assistant in the Physics and Astronomy Department. I worked in a laboratory dedicated to the cosmic ray research group led by professors Phyllis Freier and C J (Jake) Waddington. In the group were lab manager Chuck Gilman and graduate student Bob Scarlett who were preparing an instrument to be launched and held aloft by a balloon to gather data about cosmic rays, a (still) mysterious radiation of high energy particles from deep outer space.
