The Horten Flying WingsReimar and Walter Horten tested their first piloted nurflugel (only-wing) sailplane in 1933, while they were still in their teens. After further experiments, including a motorized sailplane, they built a twin-engined pusher that looked remarkably like the N-1M Flying Wing Jack Northrop would fly in 1940. Alas, this Ho 5 crashed on its first flight in 1937, breaking the aircraft, Reimar's jaw, and one of Walter's teeth. The problem was that bugbear of all-wing aircraft: the center of gravity was too far back.
The Hortens moved the engines forward and lengthened the propeller shafts, so that their all-wing looked even more like the N-1M. Their Ho 5-B flew successfully in 1938--two years before Northrop's--but was then allowed to languish under the demands of war production. (One of Reimar's projects after the war began was an all-wing transport glider for the invasion of Britain.) Not until August 1941 was Reimar asked to explore the potential of the nurflugel as a fighting aircraft, and even then his work was largely clandestine, in an authorized operation arranged by his brother in the Luftwaffe.
In 1942 Reimar built an unpowered prototype with a 61-foot span and the designation Ho 9. After some difficulty the airframe was mated with two Junkers Jumo turbojets of the sort developed for the Messerschmitt Me 262. The turbojet was apparently flown successfully in December 1944, and it eventually achieved a speed of nearly 500 mph (800 km/h). After about two hours of flying time, it was destroyed in a February 1945 crash that killed its test pilot.
Its potential was obvious, however, and the Gotha company promptly readied the turbojet for production as a fighter-bomber with the Air Ministry designation Ho 299. (Because Gotha built it, the turbojet is also called the Go 229.) Supposedly it would fly at 997 km/h (623 mph), which if true meant that it was significantly faster than the Me 262--let alone the Flying Wings that Northrop was building. Fortunately for the Allies, the Gotha factory and the Ho 299 prototype--the world's first all-wing turbojet--were captured by U.S. forces in April 1945.
Like today's B-2 Stealth bomber (and unlike Jack Northrop's designs), the Go-229 had a comparatively slender airfoil, with the crew and engines housed in dorsal humps, and its jet exhaust was vented onto the top surface of the wing. The first feature made it faster than the stubby Northrop designs; the second made it even harder to detect, as did the fact that wood was extensively used in its construction.
One reason that the Ho 229 never got into production was that Reimar Horten was distracted that winter by another urgent project: the Ho 18 Amerika bomber. This huge, six-engined nurflugel was supposed to carry an atomic bomb to New York or Washington, despite the fact that the bomb was mostly theoretical, the engines probably couldn't have lasted the journey, and the plane couldn't possibly have been completed before Germany surrendered. (At 132 feet, its span was a bit less than that of the Boeing B-29 Superfortress, the largest warplane of World War II, but considerably shorter than the Northrop XB-35 that was in the works from 1941 to 1946.)
Several nurflugels came to the U.S. as war booty, including the center section of the Ho 229. In 1993 four of them--all gliders--were returned to Germany for restoration at the Deutschese Technikmuseum in Berlin. The Ho IIL (which will remain in Germany) was finished in September 1996. Restoration continues on the other three, which will eventually come back to the United States; two are expected to go on display at NASM's Dulles annex when it is completed.
Another Horten glider, the Ho IV, belonged for a time to Mississipi State University and is now on static display at Planes of Fame in Chino, California, which also owns a Northrop N-9M, a technology demonstrator roughly the size of the Ho 299, but much less sophisticated.
The future of the Ho 229 itself is uncertain. The center section is presently at the NASM Garber facility, and will eventually go on display at Dulles, but nobody knows whether it will be finished, or to what standard, or whether it will remain a partial relic.