"The two men arrived at the airfield before dawn to set up the test stand for   
   a    
   prototype of their air-breathing rocket engine, a new kind of propulsion   
   system    
   that is a cross between a rocket motor and a jet engine. They call their   
   unholy    
   creation Fenris, and Davis believes that it’s the only way to make getting   
   to    
   space cheap enough for the rest of us. While a conventional rocket engine must    
   carry giant tanks of fuel and oxidizer on its journey to space, an   
   air-breathing    
   rocket motor pulls most of its oxidizer directly from the atmosphere. This   
   means    
   that an air-breathing rocket can lift more stuff with less propellant and    
   drastically lower the cost of space access—at least in theory.   
      
   The idea to combine the efficiency of a jet engine with the power of a rocket    
   motor isn’t new, but historically these systems have only been combined in    
   stages. Virgin Galactic and Virgin Orbit, for example, use jet aircraft to   
   carry    
   conventional rockets several miles into the atmosphere before releasing them   
   for    
   the final leg of the journey to space. In other cases, the order is reversed.    
   The fastest aircraft ever flown, NASA’s X-43, used a rocket engine to   
   provide an    
   initial boost before an air-breathing hypersonic jet engine—known as a   
   scramjet—   
   took over and accelerated the vehicle to 7,300 mph, nearly 10 times the speed   
   of    
   sound.   
      
   But if these staged systems could be rolled up into one engine, the huge    
   efficiency gains would dramatically lower the cost of getting to space. “The    
   holy grail is a single-stage-to-orbit vehicle where you just take off from a    
   runway, fly into space, and come back and reuse the system,” says   
   Christopher    
   Goyne, director of the University of Virginia’s Aerospace Research   
   Laboratory    
   and an expert in hypersonic flight."   
      
   See:   
      
   https://www.wired.com/story/the-rocket-motor-of-the-future-breat   
   es-air-like-a-jet-engine/   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)