My Background
I joined WMSI as a junior instructor-developer in January of 2015. In this role I was able to both teach and develop new technology for WMSI programs, and over the course of three summers at WMSI I had many opportunities to expand my knowledge of STEM and help others experience the magic of it. One of the most exciting projects I worked on at WMSI was the high-altitude balloon (HAB) program. High-altitude balloons involve a collection of several exciting components that come together to form a unique engineering challenge: sending a balloon with a scientific payload to the edge of space—and recovering it. WMSI works to streamline these processes to make this exciting educational platform much more accessible to schools across the north country, and I was excited to be a part of such an effort. On top of this, WMSI’s HAB work introduced me to the fascinating fields of radio communication and mission-critical “flight software,” subjects that are now driving my career in college and beyond.
Preparing a High Altitude Balloon (HAB) for launch
In the fall of 2016 I enrolled in Brown University and was presented with the incredible opportunity to be a part of Brown Space Engineering, a university club dedicated to building Brown University’s first satellite. The satellite, scheduled to launch in May 2018, was a small 10 cm cube called “EQUiSat” with the ambitious mission to periodically flash four LEDs in space that would be visible from the ground, and do so using cheap commercial parts and relatively simple fabrication methods (the final satellite cost $3776.61 to build). The satellite’s design was also fully open-source, meaning anyone with access to common machining and electronics tools, and willing to learn how to build a satellite, could buy the parts for EQUiSat and assemble their own version based on our design.
EQUiSat before launch
EQUiSat flashing two of its four LEDs
As I began working with the club, I expected the work on the satellite to be comparable to “rocket science,” and didn’t think there would be much I could contribute as a fairly new programmer. However, as I learned more about space engineering I realized much of it was familiar; space engineers think and operate just like we did at WMSI when working on HABs. Even more so, many of the challenges involved in space engineering were the same or had direct parallels with the challenges we encountered with HABs.
In my second year at Brown, after a long final push to complete the satellite’s design and construction, we finally integrated the satellite into its launch tube on March 19th, 2018. This was launched up to the International Space Station on the Orbital Sciences OA-9 Cygnus resupply mission on May 21st. After the capsule docked with the ISS three days later, we eagerly waited until July 13th, the day the satellite deployed. On the 13th, after watching on a live stream as the satellite shot out of its launch tube, we eagerly awaited its first flyover of one of our ground stations—the first time we might hear the radio signal indicating it was alive. At 7:25:48 PM EDT on the 13th, our ground station in Rome, Italy got that first transmission. That moment was the most exciting of my college career, and the satellite only continued to succeed from then on. We have now received almost 1000 transmissions and are continuing to monitor and analyze the satellite as it proceeds on its mission. We are also posting all this data to our website, equisat.brownspace.org, so everyone can keep up with the satellite.
Our first picture of EQUiSat in space; screenshotted from the livestream. It is clearly visible by it’s 4 LEDs
EQUiSat deploying from the ISS. It is the second CubeSat from the right
From HABs to Satellites
During this process of sending a satellite to space, I found through my own experience that the process of building, launching, and recovering a HAB provides one with 90% of the mindset and intuition required for a successful space mission. There are of course still technical and logistical challenges that need to be conquered, but many of the lessons that need to be learned to be successful in space—how to thoroughly test, how to handle harsh environments, how to build something that won’t break—are something everyone who participates in a HAB project comes to know.
There are several core similarities between HABs and satellites that illustrate the parallel lessons of these missions: the harsh environments that must be accounted for, the crucial scientific payload that forms the core of the mission, the critical “flight software” that controls the mission, and the radio lifeline that forms the only link between the mission and its ground support.
Harsh Environments
HABs and satellites both perform their missions far from the warm and sheltered surface of the Earth where we live our lives. Both missions experience extreme environments, but interestingly HABs and satellites have very unique challenges to face.
A high altitude balloon must rise through many layers of the atmosphere with widely varying temperatures, from the pleasant surface temperature to freezing colds just past the edge of the troposphere to increasing heat as the atmosphere thins and lets in more and more radiation from the sun. The essential challenge is keeping the temperature of the HAB’s critical electronics in their relatively small operating ranges, both on the way up and on the way down.
A diagram of how temperature changes with altitude. You can see the “V” shape that represents the initial decrease in temperature with altitude, then the switch to an increase with altitude in the troposphere and stratosphere. Image credit: United Corporation for Atmospheric Research (UCAR)
A satellite actually has a different problem: in the vacuum of space it doesn’t have any cold or warm air to affect its temperature. This seems like a good thing, but it turns out that if a satellite can’t take heat from the air, it can’t give it away either. This means that all the sunlight heating it up directly through radiation and all the heat produced by its electronics stay in the satellite and keep heating it up. As a result a satellite must be designed to dissipate or spread out all this heat using radiators or heat sinks.
EQUiSat’s panel temperatures at the time of this writing (see here for the most recent). You can tell which panels are in the sun and which aren’t by these values
A satellite does have one virtue: it doesn’t have to go through all the environmental challenges a HAB must go through, as the satellite is safely housed in a rocket on its way up through the atmosphere into space. A HAB must handle everything earth can throw at it, from atmospheric extremes to lakes and snow drifts to hard landings and curious animals.
A landed HAB
A Crucial Scientific Payload
Both HABs and satellites are centered around their “payload;” the scientific part of the mission that is generally the primary reason for the launch. The payload is a large part of what makes the mission exciting; the designers get to send these craft into places they could never go themselves, and then get to understand what those places are like through the data they get back.
For HABs, payloads are generally devoted to measuring atmospheric properties, such as temperature, pressure, and wind speed and direction. They are especially good at this because they can take measurements at many different altitudes in the atmosphere. WMSI’s HABs are designed to deliver many different types of payloads to allow for a variety of types of student missions. Past measurements have included temperature and pressure, and there are plans for measuring radiation and even it’s effect on objects such as marshmallows and popcorn kernels.
Satellite payloads can also vary significantly. There is often little to measure in space, so satellites are generally put there to either observe earth from a high vantage point, or observe the rest of our universe free of the light-blocking atmosphere. EQUiSat in particular has a bit of an odd scientific payload: it is testing special LiFePO4 batteries in space for the first time, which are perfect for providing the large amounts of electrical current needed to flash its powerful LEDs. You might see these kinds of batteries in solar garden lamps and other solar power applications due to their durability and simple electrical properties, and they are also starting to show up in electric cars and bikes because of the large amounts of electrical power they can produce (so your vehicle can accelerate faster!).
The design of HABs and satellites are devoted to making sure this payload can perform its operations successfully even with changing mission conditions. A lot of engineering goes into making a good vehicle to deliver the payload reliably to where it needs to be, and keep it there and functioning. HAB designers in particular often have the additional difficulty of making sure that payload is delivered safely back to them with all its data or experiments for future analysis.
Critical "Flight" Software
Another exciting element of HAB and satellite missions is the software. Most coders are used to the idea of writing code and then fixing bugs with that code, writing new code and fixing the bugs that come with that, and so on. In other words, most code is dynamic, and is updated and patched as issues come up. But with HABs and satellites, it’s an entirely different ballgame. Though it is possible to reprogram code on a HAB or satellite remotely, it is often a risky process, especially for simple mission with a single computer on board. This is because the software must work perfectly the first time it is uploaded. A programmer can work on improving and debugging the code on the ground, but once it is uploaded to the HAB or satellite, any bugs could “brick” the satellite, making it useless and incapable of getting new code. This means that the code must be checked painstakingly and tested rigorously. Even more so, the code should be made to be resilient, meaning that even if something goes wrong or there is a bug, the code can recover and move on.
This can be nerve wracking, but it can also be very exciting. It’s an opportunity to put something through its paces to be sure that what you’ve made is foolproof, and it makes it that much more exciting to see it work.
In fact, most HABs and satellites have some critical component that depends entirely on the code working for the mission to go as planned. For HABs, this is the cutdown system; the balloon in a HAB will keep going up for quite a long ways before it pops, so to keep the HAB from landing in a place where it can’t be recovered or going hundreds of miles from its starting point, the code must trigger some mechanism to cut off the balloon at a pre-planned time or altitude. WMSI HABs have used servo motors in the past but have now switched to using Nichrome wire. This wire has high electrical resistance and gets extremely hot when electricity goes through it, such that it slices right through the cord attaching the balloon to the payload box.
A diagram of the WMSI HAB cutdown system
In satellites, this critical component is what’s called a “deployable.” This is often either a radio antenna—which must be extended to a particular length to function optimally—or a set of deployable solar panels to power the satellite. In fact, EQUiSat used a nichrome system very similar to WMSI’s nichrome cutdown system for deploying its antenna, and this system was successful on EQUiSat just as it has been on WMSI HABs.
A close up of the EQUiSat’s antenna holding system. The three nichrome loops with the string running through them are just visible between the three sets of parallel strips of metal just above the LEDs
The Radio Lifeline
The final critical similarity between HABs and satellites is their method of communicating with the ground: radio waves. These missions are great at revealing the power of radio communications, as a radio allows the HAB or satellite to transmit its health data (called “telemetry”) and information on its scientific payload down to the ground in real time.
Once your HAB is released into the air or your satellite goes up on a rocket, and you watch it disappear from sight, it seems like it could be gone forever. But once you begin to hear the first beeps and see the first data from your mission as it comes in over the radio, you feel like you’re connected to your project again and it becomes an adventure to keep up with it as it works through the rigors of the mission.
The author listening for EQUiSat in front of WMSI in Bethlehem
While radio is essential to a mission, it is also one of the most complex and finicky parts. As you try and listen for a HAB or a satellite, it all comes down to how strong of a signal you can pick up and whether you can get a “good” signal so your data doesn’t have errors. This is why satellites and HABs are so popular in the amateur radio community. This is a group of people who work with radio as a hobby, and they get very good at hearing very faint signals such as those from HABs and satellites. Both WMSI HABs and EQUiSat have benefited greatly from the expertise and willingness of HAMs who help pick up transmissions.
A WMSI alum, Nick Sullo, listening for a HAB.
In addition to being a lifeline for data about how a mission is going, radio waves are actually crucial to “finding” HABs and satellites. Radio plays a crucial role in recovering a HAB, and WMSI has done a lot of work with radio triangulation—the math of using radio signals to estimate a transmitter’s location—that was inspired by a search and recovery of a lost HAB. Radio is also used to find satellites when they are first launched. Most CubeSats, including EQUiSat, are launched in a batch with several other satellites. For the first few days after launch, no one knows which satellite is which. But with some precision measurements of the radio’s doppler shift (the increase or decrease in the frequency of radio waves coming from something moving towards or away from you very fast), people on the ground can eventually determine each satellite’s exact location and distinguish it from the others.
In the end, HABs and satellites are far more alike than one would think. Both encounter many similar challenges, and a designer with HAB experience is ready to take on the unique challenges of a satellite. In fact, it’s fair to say that building a satellite—though it is a very complicated endeavor like any engineering challenge—is not the hardest part about going to space. One of the biggest barriers to getting into space for anyone is securing the funding for a rocket launch, but fortunately the cost of going to space has been dropping dramatically over the past two decades thanks to innovative new companies and ongoing developments. The success of EQUiSat has shown us at Brown Space Engineering that you don’t need a million-dollar budget or a team of veteran engineers to build a satellite, and space is only becoming more accessible by the day. Soon, we’ll all be able to head for the stars.