The Rocket Motor of the Future Breathes Air Like a Jet Engine:
"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-rock...-a-jet-engine/