This year’s challenge of the American Helicopter Society (AHS) competition was to design an autonomous compact rotorcraft, deployable from a submarine. The task rules required that the vehicle would be able to deploy from the submarine while in periscope depth of 15 meters, rise to the sea level, float on the surface, and fly to a destination at a distance of up to 260 km where it would deploy or pick up the crew, and return safely to the submerged submarine. The main factors on which the judges focused were the fully autonomous operation of the vehicle, its stealth, and the ability to carry two possibly injured crew members with no prior experience in piloting an aircraft.
According to the team’s design, the vehicle will be able to exit the submarine through an existing missile-silo hatch. The students say this prevents the need for complex changes to be made to the submarine’s exterior – in fact, the helicopter already fits into some currently used US submarines. The scientists said that the Waterspout allows easy entrance options while hovering above the target zone, as well as a fast exit after landing.
Instead of using a capsule to protect the helicopter from the sea-water, the students chose to make the helicopter itself completely impermeable to water. A capsule could help to save weight and solve sealing problems, but the scientists said it would also require a smaller fuselage to fit in the given submarine hatch, and would limit landing capabilities. If the helicopter was not waterproof, it would have to land precisely on the capsule’s open platform, without being able to land anywhere on the water surface.
The students said that one of the main challenges they faced was the design of the vehicle’s moving parts, such as the engine intake and exhaust. Since there were no references from past helicopter designs, the teams had to develop various necessary original sealing solutions. The groups from the two universities worked on different aspects of the design – the Technion team planned the helicopter’s mechanical deck, blade-folding mechanism, the submarine-helicopter interface, and performed water-stability analysis, while the Penn State group designed the crash-worthy fuel system, the rotor blades, and was in charge of vehicle performance calculations. The two teams cooperated fully on the vehicle’s general concept, landing gear, exterior shape, and the entrance and egress doors. Following the win, the teams were invited to present the Waterspout at the annual forum of the American Helicopter Society.