This webpage is devoted to documenting the Helios Payload. It is currently under construction, but will be updated continuously with links to all previous data, design files (both good and ugly), conclusions, ongoing work, and other resources. Enjoy!
Helios began as a freshmen group payload in the Fall Semester 2015. That iteration of the payload proved that we could (sort of) safely fly a balloon valve above the payload string parachute, and produced data that has led development since. The valve failed to demonstrate the ability to release enough helium midflight such that there was a mesureable change, but it still produced a lot of other cool data.
Since then, Helios has become a long term payload. Efforts since mid Spring Semester 2016 have culminated in a second valve design. In reality, the second design is two lighter valves capable of flying in either a 3000 g or 1600 g balloon, though only the 3000 g balloon version has flown. This payload has verified that the valve really can release enough helium to make a difference in flight, but it would be imprecise to claim guaranteed success.
Ongoing efforts are now working towards a third valve for Spring 2017, with the aim of a long duration flight with winds to the west (i.e. not towards the ocean!). This valve will likely reuse the Delrin disc from the second version with a hole for a new fill mechanism, and at least a new valve plug if not an entirely new valve design. Some electronics will also be swapped out to get closer to realizing our goal of putting the entire payload inside the balloon neck with no external box, and to utilize a better fan.
The core of Helios is the balloon venting functionality. A latex weather balloon works by expanding as it rises such that the internal pressure almost exactly equals the external atmospheric pressure. As the external pressure decreases, the volume increases until eventually the balloong bursts. By venting the balloon once already in the air, one can extend the flight duration of the balloon by delaying the burst to a higher altitude. However, this also decreases the ascent rate, which for Nearspace, would prolong the flight long enough to land over the Atlantic Ocean. Thus, Helios only vents at high altitude. If enough air is vented, the ascent rate will reach zero, and the balloon will almost never pop unless it biodegrades in the intense sunlight of the upper atmosphere. This control over the ascent rate and the maximum altitude can be used to obtain longer experiment sample times at altitude, increase the balloon maximum altitude (potentially to a ballooning record), and even influence the landing site by keeping the balloon in regions with favorable winds for longer periods of time.
NS-51 was Helios's first launch. The payload consisted of a disc sealing the balloon neck with a piece of tubing routed to a valve inside an insulated electronics box. The valve vented into the box for 60 seconds at an altitude of 18000 m. While the data cannot prove the valve worked as intended, the recovery proved that we could safely fly more vlaves above the balloon parachute in the future and still land safely.
NS-56 was filled with issues. The Adafruit GPS library occupied too much space on Helios's new processor, and could not be stripped down, so the payload flew with the valve set to open 35 minutes after power on. Unfortunately, an overflow error instead caused the valve to open after two minutes, before it had even left the ground. Additionally, this flight had an apex at 1700 ft.
NS-57 was Nearspace's first test of the Adafruit Feather M0. All systems were tested and ready to go, but the processor would not start on the launch pad, so the payload was flown as a weight. The processor magically started working three days later.
NS-58 brought newfound success at the end of the summer. Helios came to the launch pad with a spare processor, which turned out to be unnneeded, and opened for 90 seconds at 20000 m. The data returned highly suggests valve success and illuminated some other interesting phenomenon.
Contributors: Joseph Breeden, Samantha Howard, Eric Jagde, Grayson Miller Advisors: William Gilbert, Steve Lentine, Camden Miller Professor: Dr. Mary Bowden
HELIOS 1.0 (Helium Exhaust Liberating Inflation Optimization System) sought to test the idea of venting a balloon midflight. The advisors designed and fabricated the valve, and the rest of the team created the payload structure, electronics, and software to operate it. The payload consisted of two parts: a disc and a box. The disc was machined out of a reject aluminum reaction wheel and used to plug the balloon neck, while allowing a 1 inch diameter tube to penetrate the disc. The disc also held a mount for the payload string. The tubing was routed to a fill valve and the electronics box. One half of the box contained an Arduino Mega, and the other half contained the valve, consisting of radial holes in an aluminum cylinder that were covered and opened by a plunger connected to a 10 mm linear actuator. Sensors included a BNO055 IMU, two Parallax MS5607 Altimeters, and an Adafruit Ultimate GPS.
The payload only flew once on NS-51. Though we were initially optimistic, there is not nearly enough to suggest that the valve actually performed as intended. However, the valve did prove that Nearspace could safely fly a heavy payload above the balloon parachute and still descend at close to normal velocities. HELIOS 1.0 also took the first pressure and temperature measurements inside the balloon, showing that the inside of the balloon was actually an extremely stable environment. The flight generated numerous ideas for improvement, some of which were implemented in the Helios 2 series. Download the data file to see 17 plots generated during analysis.
Credit to Camden Miller and Steve Lentine for their rapid design of the valve, and their general support throughout payload construction, credit to Steve Lentine for the acronym idea, and credit to William Gilbert and Mary Bowden for allowing HELIOS to safely fly.
Check out our Poster Presentation, Final Code, Valve Design, and Data.
This section is still under construction, but you can get the gist of it from reading this paper.
From this point onward, the acronym is forgotten, but Helios is still a great name for a payload. Helios 2.0 was designed to be the lightweight version of Helios 1.0 that would be safer to operate and more reliable since we now had more experience. Except, we wanted three flights and had multiple sizes of balloons planned, so we made two versions to fit both balloons. In the end, only version 2.1 ever flew.
This section is also under construction and will be filled in around summer 2017. However, I can tell you Helios 3.0 will consist of a more thorough redesign combining aspects of both previous versions (fill tube, ahem!) and more ambitious flight goals.