ce Co The anticipated A.E.C. figures in 1957 and 1958 exceed those of 1956 and then taper off. Defense Department budgets are somewhat less at present but are expected to far exceed A.E,.C.'s as development proceeds. Gen. Keirn estimates that a total of $139 million will have been spent by AEC and the Air Force by July 1955 and that about $325 million will have been expended in bringing the two approaches up tothe initial testing of Ground Prototype Propulsion Systems, Additional Air Force funds will be needed before there is a propulsion system ready for flight test. There are two parallel approaches: the Fluid Fuel reactor under develop- ment at Oak Ridge, with Pratt and Whitney collaborating, and the direct air cycle being developed by General Electric at Lockland, Ohio. A paper study on a heterogeneous reactor cooled by sodium has been prepared by Nuclear Development Associates and could constitute. another approach if this is deemed .oToadvigsblte Fluid Fuel Reactor The Fluid Fuel reactor which Oak Ridge is developing (also known as the Circulating Fuel Reactor or the Fire Ball) is a beryllium-moderated reactor, fueled by a circulating fused salt mixture containing uranium, and cooled by sodium or Nak. The energy from the reactor is to be converted into propulsive thrust for the aircraft by transferring heat from the sodium to air from the compressor just before it enters the turbine of a reasonably—conventional jet engine. (The first reactor experiment - ARE - went critical Nov. 4th.) The technical problems are serious, centering around materials and corrosion. One of the fused salt mixtures which had been considered favorably :