HeiDAS UH - Flying with superheated steam

[Abstract] The feasibility of steam as buoyant gas for high performing balloons was proved. Building and operating a rc-controlled insulated roziere-type model - HeiDAS UH became the first free flying steam balloon ever. Innovative and new developed materials are allowing temperatures up to 260°C and providing steam tightness and strength to the highest possible extend. CFD simulations of the entire balloon give a detailed overview of the temperature distribution and the efficiency of the insulation. A simplified mathematical model is presented which allows the quick and proper estimation of the thermal behavior and the systems performance. From the profound knowledge of the model an auomative altitude control system was developed and implemented. The steam balloon technology is now ready for implementation into a full scale prototype balloon.