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  • Unleashed - the Samarai Way
    Posted by Graham Warwick 6:06 PM on Jul 17, 2011

    Electric aircraft are here today, but available battery technology severely limits their size and performance. Hybrid-electric propulsion is a solution, using fuel to provide sufficient energy storage and an internal-combustion (IC) engine to generate the electricity.

    NASA is looking at a vertical take-off and landing personal-aircraft concept that combines an IC cruise engine with a lightweight electric lift system. The Samarai* reduces drag in forward flight by stopping the single-blade wingtip rotors so they can act as extensions to the wings.

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    blog post photo
    All concepts: NASA

    NASA aerospace engineer Mark Moore says a key objective with Samarai is to achieve propulsion redundancy all the way out to the tips of the prop-rotors. One way this is achieved is by using short-range laser scanners at each corner of the vehicle to watch for potential blade strikes and quickly stop the affected prop-rotor before impact.

    He says a test rig was built that showed electric motors can be stopped in any position "incredibly quickly", especially given each single-blade rotor's small size and low weight. The result is a compact configuration, although there is some wasted rotor thrust from download on the wings, Moore says.

    blog post photo

    Samarai is a more practical follow-on the NASA's Puffin concept for a lightweight single-person VTOL aircraft. The all-electric Puffin weighs less than 300lb and is highly efficient, with a lift-to-drag ratio of around 18, but the pilot cannot sit down and a blade strike would be catastrophic, Moore says. Here are NASA videos of both concepts.


    Samarai


    Puffin

    * Samarai comes from the single-blade rotor's similarity to the samara, or maple seed.

    Tags: awt, aeronautics, rotorcraft, propulsion

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