The Marshall Space Flight Center and its industry partners have just announced the completion of successful testing of air-breathing rocket engines. These "athodyds" are basically supersonic combustion ramjets, and have interested rocket engine designers since the early 40's. (I first read about them in the Akron Beacon Journal in 1945.) The rockets are placed in ducts that entrain air around the rocket exhaust until the rocket reaches Mach 2. Then the combustion switches to the supersonic-combustion-ramjet mode until the rocket attains a speed of Mach 10. Thereafter, the engines resume operation as conventional rocket engines, driving the vehicle into orbit. All of this lowers the weight of oxygen that must be carried on board, and substantially lowers payload costs.
    An artist's conception of such a vehicle is shown in the figure below.

    Additional photos may be found at http://www1.msfc.nasa.gov/NEWSROOM/news/photos/2000/photos00-108.htm
 and an Air-breathing Rocket Engine Technology Summary: is available at:
http://www.msfc.nasa.gov/news/astptechbriefs/air_breathing.pdf
    Interviews and materials supporting this Media Update are available to media representatives by contacting June Malone of the Marshall Media Relations Department at (256) 544-0034. For more information on Marshall's space transportation activities, visit: http://www.highway2space.com 

This news brief was taken from "Air Breathing Rocket Tests Successful", ScienceDaily, April 23, 2000.