From: sylvia@email.invalid   
      
   On 21-Feb-24 8:31 am, The Running Man wrote:   
   >> On 2024-02-20 1:51 p.m., The Running Man wrote:   
   >>>> For some reason, the PNN folks who were quite active on this group do   
   >>>> not seem to have posted anything in a long while. Did they run out of   
   >>>> active people, or money? Or did they finally figure out it doesn't work   
   >>>> and quietly closed shop?   
   >>>> --   
   >>>> /* * * Otto J. Makela  * * * * * * * * * */   
   >>>> /* Phone: +358 40 765 5772, ICBM: N 60 10' E 24 55' */   
   >>>> /* Mail: Mechelininkatu 26 B 27,  FI-00100 Helsinki */   
   >>>> /* * * Computers Rule 01001111 01001011 * * * * * * */   
   >>>   
   >>> What does PNN stand for?   
   >>>   
   >>   
   >> It stands for Propulsione Non Newtoniana (Italian, meaning Non-Newtonian   
   >> Propulsion). A group of Italian people claiming that they have a   
   >> propulsion system using no reaction mass. Something like a microwaves   
   >> bouncing around in a closed cavity that they claim, without explaining   
   >> the physics behind it, that it produces acceleration. They have video   
   >> showing that it gives if I recall correctly some 200 mN of force. We   
   >> tried to explain to them that because their microwaves heat one side of   
   >> their apparatus more than the other side, the air is heated more on one   
   >> side than the other. This differential in air temperature can explain   
   >> the force that they measure, therefore, outside an atmosphere it   
   >> wouldn't work. But they don't want any of that, they are sure that their   
   >> "invention" will revolutionize rocketry.   
   >>   
   >>   
   >> Alain Fournier   
   >>   
   >   
   > I once read a (fiction) book about futuristic spaceships and they claimed   
   that a mass-less propulsion drive could be made by a huge electromagnet which   
   would change its polarity so fast that the EM flux didn't have time to   
   dissipate, thereby creating a    
   repelling force.   
      
   Transmitting electromagnetic waves using a directional antenna produces   
   a net force. Not much of one, for sure, but some. It's a kind of photon   
   drive.   
      
   But it's still not mass-less, because the photons that form the   
   electromagnetic waves have mass, and the attached craft is losing mass   
   in proportion to the energy being radiated.   
      
   Near a star, the required energy can be collected using solar panels,   
   but solar sails of the same area work better.   
      
   So there's a reason we don't use photon drives.   
      
   Sylvia.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)