What became the last Junkers wartime submission to the German Air Ministry during World War 2 (1939-1945) - the Junkers EF-140 (or "Project 140") - was actually a further development of the earlier Horten Ho P.18A flying wing bomber developed as part of the "Amerika Bomber" initiative. The initiative stemmed from the German need to generate a fleet of bombers capable of crossing the Atlantic and striking at major American cities along the east coast (hence the program's name). The bomber would have to possess inherently excellent range to reach these targets and return home after delivery of their war load. High altitude operation was a must for efficiency and to avoid interception by aircraft or ground-based fire.
Thanks to the Allied air raids wreaking havoc on German war-making facilities and infrastructure, the Germans lost their chance to advance an atomic weapons program and were forced along a more conventional route utilizing more conventional methods. This gave renewed attention to a long range bomber for delivery of a large drop-bomb load and various German air concerns through their hat into the ring to secure a Luftwaffe contract for a long range, heavy-hitter. Despite several design competitions to fulfill the requirement, no one company could promise that their new bomber would possess the range necessary.
The Horten Brothers (Walter and Reimar) were contacted during late 1944 due to their background in large, tailless "flying wing" aircraft that might fit the bill. Walter Horten responded with a possible submission which entailed use of no fewer than six Junkers Jumo 004 turbojet engines. The design was designated as the "P.18A" and Luftwaffe chief Hermann Goring himself championed the product.
In an effort to expedite development of the bomber, it was decided by the Air Ministry to involve the talents of multiple firms - a design-by-committee approach being favored rather than give the lead to the small Horten team. Manufacture of the aircraft would fall to the Junkers concern which held extensive experience in arranging large aircraft prior to, and during, the war. Other companies thrown into the mix were representatives of Arado and Messerschmitt. Because of the relentless Allied air raids, it was decided to build the prototype in a cave - adding an air of secrecy to the entire program.
The flying wing design being penciled out would be a fine delta-shape with swept-back mainplanes. The crew would number six and all were to be contained in a centralized section of the blended-body fuselage. A multi-wheeled undercarriage, wholly retractable, supported the design when at rest. The engine exhaust ports would be built into a straight section of the trailing wing edge while outboard trailing wing sections would conform to the sweep defined by the leading edge. Considering the vast internal make up of the aircraft, it could have carried large stores of fuel for the journey ahead as well as crew support systems and the bomb load (all bombs to be held internally). Defensive armament was 4 x remote-controlled barbettes fitting 30mm MK 108 automatic cannons - mainly to contend with interceptors. Two barbettes were positioned facing forward near the nose with the remaining to barbettes set to either side of the rudder structure, facing aft.
The committee soon turned on the Horten design and felt that a vertical rudder should be added for stability and the turbojet engines be clustered as two groups of three engines each. Reimar Horten grew displeased with the whole notion of detracting from the streamlined, all-wing approach that originally existed - any sort of obstruction was sure to increase drag and reduce performance. To that end, the Hortens abandoned the project which carried on without them.
The bomber was christened with the designation of EF 140 as part of the Junkers brand label from this point on. The redesigned aircraft retained its general shape from the Horten submission but an interesting vertical structure was added that ran nearly from the nose of the aircraft well past the engine exhaust ports at rear. The crew compartment was worked into the base of this structure, heavily framed over to form the cockpit, while the nose - the point of the arrowhead - was glazed over for better observation by the bombardier. Due to the speeds and altitudes at play, each of the six crewmen would be granted ejection seats. As expected, the six engines were clustered in two groups of three and set to either side of the bomb bay area. The engine of choice became either the Junkers Jumo 004 or the competing BMW 003 turbojet series.
This is about all that constituted the EF 140 flying wing bomber. The design was not furthered into any physical form (not even wind tunnel models) and the situation for Germany deteriorated to such lengths that many of its aircraft projects (some quite fantastic in their scope) fell to naught by the end. As such, the EF 140 was one a myriad of "paper airplanes" never to see the light of day in the grand war. The Hortens, meanwhile, continued work on their P.18 and developed it into the P.18B which achieved Goring's personal approval. However, this initiative also went nowhere due to the lack of available material, manpower and funding. The end of the war signified the end of this flying wing project as well.