Low cost, high endurance, altitude-controlled latex balloon for near-space research (ValBal)

High-altitude balloons in near space offer the possibility of affordable scientific experimentation and hardware testing for outer space missions. In this paper we present a novel, low cost high-altitude balloon system that achieves multi-day flight using inexpensive latex balloons by automatically venting lifting gas and dispensing ballast to maintain altitude. Traditionally, superpressure balloons have been used for high-altitude scientific missions; however, despite their long endurance and payload capacity in the tens of kilograms, their cost is in excess of tens of thousands of dollars. Latex balloons are significantly less expensive, typically costing little more than a hundred dollars, but in normal use fly for only a couple hours, rising until reduced atmospheric pressure causes the balloon to stretch beyond its limits. Precision-weighted latex balloons have demonstrated multi-day flights, but such systems cannot change altitude while aloft and offer minimal payload capacity (measuring in tens of grams). Our system, known as ValBal, offers altitude control capabilities exceeding those of a superpressure balloon at a two order of magnitude reduction in cost. ValBal can stabilize anywhere in its operational range of 10-25 km altitude, and can execute scheduled or remotely commanded altitude transitions during flight. In its current iteration, ValBal can be configured to accommodate payloads on the order of 10000 cubic centimeters and 2 kilograms. In June 2016, a ValBal demonstration mission flew for over 70 hours continuously, surpassing the previous world record of 57 hours, for the longest duration of a latex balloon flight. ValBal has flown twice more since then, including a flight of almost 80 hours. Planned developments will seek to improve the endurance to a week and increase the payload interface capabilities for scientific missions.