Certainly the most futuristic aircraft design of World War II ― indeed, a design that would look very modern even today ― was the Luftwaffe’s Horten IX flying wing fighter, the final product of Germany’s Horten brothers. They had been designing tailless flying wing gliders since the early 1930s on the principle that without a fuselage the flying wing platform would have lower overall drag and thus increased performance.
When World War II began they built two examples with two small pusher engines with the idea of using the flying wing for military aircraft, and in August 1941 the Luftwaffe asked the brothers to expand their exploration of the flying wing’s potential with jet power. In 1942 the Hortens built a prototype with a 61-foot span, the Horton IX V1, but the wing spar was too small for jet engines so it was completed as an unpowered glider. The V1 was test-flown for the first time in February 1944 and flight results were very favorable.
After some difficulty caused by poor communications, the airframe was mated with two Junkers Jumo 004 turbojets developed for the Messerschmitt Me 262 and the second prototype, the Horten IX V2, made its first flight with jet power on 2 February 1945.
The V2’s center pod was made of welded steel tubing and housed the pilot and engines close together in center of the fuselage. The intakes were in the extreme nose next to the cockpit and the jet exhaust was vented onto the top surface of the wing, which had steel panels to protect it from the heat.
The wing itself was a slender, carbon-impregnated plywood airfoil with a chord/thickness ratio ranged from 15% at the root to 8% at the wingtips. Elevons and spoilers provided control. A drogue parachute slowed the aircraft after landing and pilot had a primitive, spring ejection seat.
The first flight of the H.IX V2 displayed good handling qualities, with only moderate lateral instability, the typical deficiency of pre-fly by wire tailless aircraft. While the second flight was equally successful, the undercarriage was damaged by a heavy landing caused when the test pilot deployed the brake parachute too early.
The damage was repaired, but two weeks later, on the third flight, disaster struck. After three test speed runs at about 7000 feet, the aircraft lost an engine as it approached the airfield to land, crashed and was completely destroyed.
Despite this setback, work continued on the third prototype, the Ho 229 V3, but the work was given to the Gothaer Waggonfabrik, (Gotha, GWF), which had the facilities to mass produce it. The V3 was essentially a ready for production, powered by two Jumo 004C engines and with two MK 108 30mm cannon in the wing roots. Work was also started on a two-seat night-fighter prototype.
The Gotha team changed the undercarriage to enable a higher gross weight and modified the jet engine inlets. The aircraft’s name was also changed to the Gotha 229, a name change that creates confusion to this day. After the war, the sole Ho IX V3 (Go 229), with the wings detached from the fuselage, was taken by the Western allies for evaluation. The RAF considered fitting it with British jet engines, but the mountings were incompatible, so it was returned to the US. Today it is awaiting restoration at the National Air and Space Museum.
There has been some discussion of the IX’s “stealth” characteristics. It would have certainly had a very low radar signature, but at the end of World War II this was not a consideration in aircraft design, only a by product.