XPost: sci.electronics.design, sci.physics, sci.space.policy   
   From: ham789@netzero.net   
      
   On 11/7/2016 7:39 PM, jimp@specsol.spam.sux.com wrote:   
   > In sci.physics mike  wrote:   
   >> On 11/7/2016 1:46 PM, jimp@specsol.spam.sux.com wrote:   
   >>> In sci.physics Phil Hobbs  wrote:   
   >>>> On 11/07/2016 01:37 PM, jimp@specsol.spam.sux.com wrote:   
   >>>>> In sci.physics Robert Clark  wrote:   
   >>>>>   
   >>>>>    
   >>>>>   
   >>>>>> If you know of a means to provide 50,000 V at *lightweight* then you   
   will   
   >>>>>> have solved the problem of an independently flying lifter, using the   
   >>>>>> macrosized wires currently used. You would need about a power to weight   
   >>>>>> ratio for the power source of better than 1 watt per gram, while being   
   able   
   >>>>>> to provide these ca. 50,000 V voltages.   
   >>>>>>   
   >>>>>>    Bob Clark   
   >>>>>   
   >>>>> Trivial; look at any camera flash unit built in the last several decades.   
   >>>>>   
   >>>>> However you have totally missed the point; voltage and the weight of the   
   >>>>> converter is irrelevant as it is the total power that determines the   
   >>>>> weight of it all.   
   >>>>>   
   >>>>> BTW, here are some real world power to weight ratios:   
   >>>>>   
   >>>>> Boeing 777 engine 10 kW/kg   
   >>>>    1985 Chevy Celebrity 300 W/kg <-- So for a 1000 kg car, that's 402   
   >>>> horsepower?  Sign me up! ;)   
   >>>>   
   >>>> Cheers   
   >>>>   
   >>>> Phil Hobbs   
   >>>   
   >>> No, that is the power to weight ratio of the engine, not the power to   
   >>> weight ratio of the car.   
   >>>   
   >>>   
   >> Power is a red herring.  What's important is the total energy produced   
   >> by the   
   >> engine AND the fuel supply.   
   >> It doesn't get the least bit interesting until the engine can lift   
   >> itself and a FULL tank of whatever powers it AND the vehicle AND the   
   >> payload to reach the destination.   
   >> I can't imagine that ever happening 1000 feet off the ground on this ole   
   >> earth at a cost anywhere near the cost of other forms of transportation.   
   >   
   > Are you trying to say airplanes aren't going to make it in the commercial   
   > world?   
   >   
   >   
   Yep, that's exactly what I'm saying: "Airplanes with ion drive are not   
   going to make it in the commercial world."  Whatever technology can make   
   that work will be FAR less costly applied to something that rolls along   
   the roadway.   
      
   But that misses the point that it's ENERGY that's the concern.  Doesn't   
   matter how light or powerful the airplane engine is if it still can't lift   
   enough fuel to reach the destination.  It takes a given amount of energy   
   to get from here to there.  Changing the engine only affects the efficiency   
   of the process that converts the available fuel source to whatever it takes   
   to motivate the vehicle.  Maybe we'll see terrestrial ion engines, but   
   the efficiency   
   improvement won't be huge.   
      
   If we had an electric fuel source of sufficient energy/weight ratio,   
   we'd already have electric airplanes.   
      
   If you're gonna spend millions of dollars to fling an object into   
   space at escape velocity, it makes sense to have a nuclear power   
   source that applies tiny thrust for a long time using minimal reaction   
   mass to continue the flight to places unknown.   
   For a terrestrial flight to New York, not so much.   
      
   So, what am I missing?   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)