Advancements in low-cost, long endurance, altitude controlled latex balloons (ValBal)

High-altitude balloons give easy access to near-space experiments; however, stringent mass-budgets and low ambient temperatures make it challenging to develop capable small-scale research platforms, restricting most small-scale flights to uncontrolled latex balloons with ~3 hour endurance. Last year we demonstrated a novel altitude control system for latex balloons (termed ValBal) that enables multi-day flight carrying a several kilogram payload. We have achieved a cost-per-kilogram-hour that is competitive with much larger zero-pressure or superpressure balloons, while offering dynamic altitude control capabilities far exceeding those systems. Our nascent platform has garnered interest from research groups including geological and atmospheric research laboratories. ValBal has been sought as a new platform for glaciological observations, through the development of a 435 MHz radar sounder payload to measure ice sheet thickness in Greenland. Coupled with the broad altitude control capability of our platform, these applications have motivated a separate research project to control flightpath by algorithmically switching between different wind layers. In this paper, we present the latest developments towards a reliable and low-cost platform for near-space research. Over the past year we have made advances that eliminated the need for high-grade thermal insulation by selecting a battery chemistry that can function at -65 °C and reduced the number of custom mechanical components by a factor of ten through the use of additive manufacturing, along with a two-fold reduction in overall system cost. We have demonstrated robust performance, with our last five successful flights achieving a mean endurance of 83 hours and a world record maximum for latex balloons of 121.5 hours. In addition, we are developing a 10 kbit, 400 km range, GFSK radio system for experimental data downlink to a dedicated network of ground stations across the US. As our design approaches a kit that can be assembled in just a few hours, we look forward to many more research collaborations leveraging the new capabilities offered by the ValBal platform.