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Electric Duct Fan (EDF) Self-Launch Glider?
Electric Duct Fan (EDF) Self-Launch Glider?
I have pondered this for some time now. Electric Duct Fan (EDF) propulsion systems have been making strides in the RC model jet world and are challenging the use of mini turbine jet engines (now used on a number of full scale SL sailplanes) Battery technology regarding power density and safety continues to improve at a rapid pace. (auto engineer recently stated that within 5 years batteries will approach the power density of gasoline ... hard to believe but ?? ) EDF systems do not have the tremendously high exhaust temperature (~700°C) and decibel level issues. (Though not as loud, the EDF systems sound very similar) Assuming: - L/D 40:1 850 pound Sailplane (in my case Genesis 2) - Cluster of (3) currently available EDF Units producing combined ~60 pounds STATIC THRUST (AFTER taking into account loss of efficiency do to close clustering of intake ducts) - Battery capacity for ~10 minutes full power .. no reserve - 2,500ft Paved Runway .. No Tailwind - Sailplane pre-positioned on runway (not taxied to runway) - Goal altitude of ~1,500ft AGL As a "sustainer" I am fairly confident this would yield some success .. if only buying you ~10 miles What I would like to hear from the hobby-physicists out there are comments on these questions: 1 - How detrimental is the loss of efficiency/performance when clustering duct fan intakes in very close proximity? 2 - With sailplane starting from rest, how long would it take to accelerate to flying speed? i.e. Would I need 3 miles of paved runway? and/or .. Would the batteries be dead before the glider left the ground? I certainly am not proposing a "replacement" for jet turbines .. only curious if the above scenario is at all feasible. Thanks for comments! Curt Lewis - 95 Genesis 2 Loves Park, IL USA |
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