Horten Ho 229
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| Ho 229 | |
|---|---|
 | |
| H.IX V1 drawings | |
| Role | Fighter/Bomber |
| Manufacturer | Gothaer Waggonfabrik |
| Designer | Horten brothers |
| First flight | 1 March 1944 |
| Primary user | Luftwaffe |
| Number built | 3 |
It was given the personal approval of German Luftwaffen Reichsmarschall Hermann Göring, and was the only aircraft to come close to meeting his "3×1000" performance requirements, namely to carry 1,000 kilograms (2,200 lb) of bombs a distance of 1,000 kilometres (620 mi) with a speed of 1,000 kilometres per hour (620 mph). Its ceiling was 15,000 metres (49,000 ft).[2]
Since the appearance of the B-2 Spirit flying wing stealth bomber in the 1990s, its similarities in role and shape to the Ho 229 has led many to retrospectively describe the Ho 229 as "the first stealth bomber".[3] A significantly coarsely built replica of a captured and disassembled Ho 229 was later tested by the US military who found the basic shape and paint composition of the mock copy would provide for 20% reduction in detection range against the Chain Home radar of the 1940s, but no significant stealth benefit against most other contemporary radar systems.[3]
Contents[hide] |
Design and development [edit]
In the early 1930s, the Horten brothers had become interested in the flying wing design as a method of improving the performance of gliders. The German government was funding glider clubs at the time because production of military and even motorized aircraft was forbidden by the Treaty of Versailles after World War I. The flying wing layout removes any "unneeded" surfaces and, in theory at least, leads to the lowest possible weight. A wing-only configuration allows for a similarly performing glider with wings that are shorter and thus sturdier, and without the added drag of the fuselage. The result was the Horten H.IV.In 1943, Reichsmarschall Göring issued a request for design proposals to produce a bomber that was capable of carrying a 1,000 kilograms (2,200 lb) load over 1,000 kilometres (620 mi) at 1,000 kilometres per hour (620 mph); the so-called "3 X 1000 project". Conventional German bombers could reach Allied command centers in Great Britain, but were suffering devastating losses from Allied fighters. At the time, there was no way to meet these goals — the new Junkers Jumo 004B turbojets could provide the required speed, but had excessive fuel consumption.
The Hortens concluded that the low-drag flying wing design could meet all of the goals: by reducing the drag, cruise power could be lowered to the point where the range requirement could be met. They put forward their private project, the H.IX, as the basis for the bomber. The Government Air Ministry (Reichsluftfahrtministerium) approved the Horten proposal, but ordered the addition of two 30 mm cannons, as they felt the aircraft would also be useful as a fighter due to its estimated top speed being significantly higher than that of any Allied aircraft.
The H.IX was of mixed construction, with the center pod made from welded steel tubing and wing spars built from wood. The wings were made from two thin, carbon-impregnated plywood panels glued together with a charcoal and sawdust mixture. The wing had a single main spar, penetrated by the jet engine inlets, and a secondary spar used for attaching the elevons. It was designed with a 7g load factor and a 1.8x safety rating; therefore, the aircraft had a 12.6g ultimate load rating. The wing's chord/thickness ratio ranged from 15% at the root to 8% at the wingtips.[1] The aircraft utilized retractable tricycle landing gear, with the nosegear on the first two prototypes sourced from a He 177's tailwheel system, with the third prototype using an He 177A main gear wheelrim and tire on its custom-designed nosegear strutwork and wheel fork. A drogue parachute slowed the aircraft upon landing. The pilot sat on a primitive ejection seat. It was originally designed for the BMW 003 jet engine, but that engine was not quite ready and the Junkers Jumo 004 engine was substituted.[1]
Control was achieved with elevons and spoilers. The control system included both long span (inboard) and short span (outboard) spoilers, with the smaller outboard spoilers activated first. This system gave a smoother and more graceful control of yaw than would a single spoiler system.[1]
Operational history [edit]
Testing and evaluation [edit]
The first prototype H.IX V1, an unpowered glider, flew on 1 March 1944. Flight results were very favorable, but there was an accident when the pilot attempted to land without first retracting an instrument-carrying pole extending from the aircraft. The design was taken from the Horten brothers and given to Gothaer Waggonfabrik. The Gotha team made some changes: They added a simple ejection seat, dramatically changed the undercarriage to enable a higher gross weight, changed the jet engine inlets, and added ducting to air-cool the jet engine's outer casing, so as to prevent damage to the wooden wing.[1]The H.IX V1 was followed in December 1944 by the Junkers Jumo 004-powered second prototype H.IX V2; the BMW 003 engine was preferred, but unavailable. Göring believed in the design and ordered a production series of 40 aircraft from Gothaer Waggonfabrik with the RLM designation Ho 229, even though it had not yet taken to the air under jet power. The first flight of the H.IX V2 was made in Oranienburg on 2 February 1945.
All subsequent test flights and development were done by Gothaer Waggonfabrik. By this time, the Horten brothers were working on a turbojet-powered design for the Amerika Bomber contract competition, and did not attend the first test flight. The test pilot was Leutnant Erwin Ziller. Two further test flights were made between 2 and 18 February 1945. Another test pilot used in the evaluation was Heinz Scheidhauer.
The H.IX V2 reportedly displayed very good handling qualities, with only moderate lateral instability (a typical deficiency of tailless aircraft). While the second flight was equally successful, the undercarriage was damaged by a heavy landing caused by Ziller deploying the brake parachute too early during his landing approach. There are reports that during one of these test flights, the H.IX V2 undertook a simulated "dog-fight" with a Messerschmitt Me 262, the first operational jet fighter and that the H.IX V2 outperformed the Me 262.
Two weeks later, on 18 February 1945, disaster struck during the third test flight. Ziller took off without any problems to perform a series of flight tests. After about 45 minutes, at an altitude of some 800 m, one of the Jumo 004 turbojet engines developed a problem, caught fire and stopped. Ziller was seen to put the aircraft into a dive and pull up several times in an attempt to restart the engine and save the precious prototype.[4] Ziller undertook a series of four 360-degree turns with the wings banked 20 degrees. Ziller did not use his radio or eject from the aircraft. He may already have been unconscious as a result of the fumes from the burning engine. The aircraft crashed just outside the boundary of the airfield. Ziller was thrown from the aircraft on impact and died from his injuries two weeks later. The prototype aircraft was completely destroyed.[4]
The V3 was larger than previous prototypes, the shape being modified in various areas, and it was meant to be a template for the pre-production series Ho 229 A-0 day fighters, of which 20 machines had been ordered. V3 was powered by two Jumo 004C engines, and could carry two MK 108 30mm cannon in the wing roots. Work had also started on the two-seat Ho 229 V4 and Ho 229 V5 night-fighter prototypes, the Ho 229 V6 armament test prototype, and the Ho 229 V7 two-seat trainer.
During the final stages of the war, the U.S. military initiated Operation Paperclip, an effort to capture advanced German weapons research, and keep it out of the hands of advancing Soviet troops. A Horten glider and the Ho 229 V3, which was undergoing final assembly, were secured for sending to the United States for evaluation. En route, the Ho 229 spent a brief time at RAE Farnborough in the UK while it was considered if British jet engines could be fitted, but the mountings were incompatible[5] due to the available British engines of the time only using centrifugal compressors with their comparatively larger diameter compressor sections, and not the slimmer axial-flow turbojet powerplants the Germans were using.
Survivors [edit]
The only surviving Ho 229 airframe, the V3, is at the Smithsonian National Air and Space Museum's Paul E. Garber Restoration Facility in Suitland, Maryland. In December, 2011, the National Air and Space Museum had moved the Ho 229 into the active restoration area of the Garber Restoration Facility and is currently being reviewed for full restoration and display.Stealth technology [edit]
Engineers of the Northrop-Grumman Corporation had long been interested in the Ho 229, and several of them visited the Smithsonian Museum's facility in Silver Hill, Maryland in the early 1980s to study the V3 airframe. A team of engineers from Northrop-Grumman ran electromagnetic tests on the V3's multilayer wooden center-section nose cones. The cones are three quarters of an inch (19 mm) thick and made up of thin sheets of veneer. The team concluded that there was indeed some form of conducting element in the glue, as the radar signal attenuated considerably as it passed through the cone.[3]
Northrop-built reproduction [edit]
In early 2008, Northrop-Grumman paired up television documentary producer Michael Jorgensen, and the National Geographic Channel to produce a documentary to determine whether the Ho 229 was, in fact, the world's first true "stealth" fighter-bomber.[3] Northrop-Grumman built a full-size non-flying reproduction of the V3, constructed to match the aircraft's radar properties. After an expenditure of about US$250,000 and 2,500 man-hours, Northrop's Ho 229 reproduction was tested at the company's classified radar cross-section (RCS) test range at Tejon, California, where it was placed on a 15-meter (50 ft) articulating pole and exposed to electromagnetic energy sources from various angles, using the same three frequencies in the 20–50 MHz range used by the Chain Home in the mid-1940s.[3]RCS testing showed that a hypothetical Ho 229 approaching the English coast from France flying at 885 kilometres per hour (550 mph) at 15–30 metres (49–98 ft) above the water would have been visible at a distance of 80% that of a Bf 109. This implies a frontal RCS of only 40% that of a Bf 109 at the Chain Home frequencies. The most visible parts of the aircraft were the jet inlets and the cockpit, but caused no return through smaller dimensions than the CH wavelength. Given the high-speed capabilities of the aircraft it would have given the British defences just two and a half minutes to respond, which would not have been enough time. It is believed that, if deployed in great numbers, the Ho 229 could have changed the course of the war.[3][7]
With testing complete, the reproduction was donated by Northrop-Grumman to the San Diego Air and Space Museum.[3][8] The television documentary, Hitler's Stealth Fighter (2009), produced by Myth Merchant Films, featured the Northrop-Grumman full-scale Ho 229 model as well as CGI reconstructions depicting a fictional wartime scenario where Ho 229s were operational in both offensive and defensive roles.[7]
Variants [edit]
- H.IX V1
- First prototype, an unpowered glider, one built and flown (three-view drawing below).[1]
- H.IX V2
- First powered prototype, one built and flown with twin Junkers Jumo 004B engines.[1]
- Ho 229 V3
- Revised air intakes, engines moved forward to correct longitudinal imbalance. Its nearly completed airframe was captured in production, with two Junkers Jumo 004B jet engines installed in the airframe.
- Ho 229 V4
- planned two seat all weather fighter, in construction at Friedrichroda, but not much more than the center-section's tubular framework completed.[1]
- Ho 229 V5
- planned two seat all weather fighter, in construction at Friedrichroda, but not much more than the center-section's tubular framework completed.[1]
- Ho 229 V6
- Projected definitive single-seat fighter version with different cannon, mock-up in production at Ilmenau.
- H.IXb (also designated V6 and V7 by the Hortens)
- Projected two-seat trainer or night-fighter; not built.[1]
- Ho 229 A-0
- Projected expedited production version based on Ho 229 V6; not built.
Specifications (Horten Ho 229A (V3)) [edit]
From manufacturer's estimates-three view drawing at top of page shows the Ho IX V1 glider prototype.
Data
from The Great Book of Fighters[9]
General characteristics- Crew: 1
- Length: 7.47 m (24 ft 6 in)
- Wingspan: 16.76 m (55 ft 0 in)
- Height: 2.81 m (9 ft 2 in)
- Wing area: 50.20 m² (540.35 ft²)
- Empty weight: 4,600 kg (10,141 lb)
- Loaded weight: 6,912 kg (15,238 lb)
- Max. takeoff weight: 8,100 kg (17,857 lb)
- Powerplant: 2 × Junkers Jumo 004B turbojet, 8.7 kN (1,956 lbf) each
- Maximum speed: 977km/h (607 mph) at 12,000 metres (39,000 ft)
- Service ceiling: 16,000 m (52,000 ft)
- Rate of climb: 22 m/s (4,330 ft/min)
- Wing loading: 137.7 kg/m² (28.2 lb/ft²)
- Thrust/weight: 0.26
- Guns: 4 × 30 mm MK 108 cannon
- Rockets: R4M rockets
- Bombs: 2 × 500 kilograms (1,100 lb) bombs
See also [edit]
- Related development
- Aircraft of comparable role, configuration and era
- Related lists
References [edit]
Notes [edit]
- ^ a b c d e f g h i j Green 1970, p. 247.
- ^ Boyne 1994, p. 325.
- ^ a b c d e f g h Myhra 2009, p. 11.
- ^ a b c Handwerk, Brian (25 June 2009). "Hitler's Stealth Fighter Re-created". News.nationalgeographic.com. Retrieved 29 July 2012.
- ^ Brown 2006, p. 119.
- ^ "Flying under the Radar: A History of Stealth Planes." National Geographic Channel, 2009. Retrieved: 6 November 2010.
- ^ a b "Hitler's Stealth Fighter." Myth Merchant Films, 2009, first aired on 28 June 2009 on the National Geographic Channel (USA). Retrieved: 24 October 2010.
- ^ "San Diego Air Museum will house replica German flying wing." signonsandiego.com. Retrieved: 6 July 2009.
- ^ Green, William and Gordon Swanborough. The Great Book of Fighters. St. Paul, Minnesota: MBI Publishing, 2001. ISBN 0-7603-1194-3.
Bibliography [edit]
- Boyne, Walter J. Clash of Wings. New York: Simon & Schuster, 1994. ISBN 0-684-83915-6.
- Brown, Eric. Wings On My Sleeve: The World's Greatest Test Pilot tells his Story. London: Orion Books. 2006. ISBN 978-0-297-84565-2.
- Green, William. Warplanes of the Third Reich. London: Macdonald and Jane's Publishers Ltd., 1970. ISBN 0-356-02382-6.
- Myhra, David. The Horten Brothers and Their All-wing Aircraft. London: Bushwood Books, 1997. ISBN 0-7643-0441-0.
- Myhra, David. "Northrop Tests Hitler's 'Stealth' Fighter." Aviation History, Volume 19, Issue 6, July 2009.
- Shepelev, Andrei and Huib Ottens. Ho 229, The Spirit of Thuringia: The Horten All-wing jet Fighter. London: Classic Publications, 2007. ISBN 1-903223-66-0.
External links [edit]
 |
Wikimedia Commons has media related to: Horten Ho IX |
- Horten Nurflügels
- Handwerk, Brian (25 June 2009). "'Hitler's Stealth Fighter' Re-created". News.nationalgeographic.com. Retrieved 29 July 2012.
- Arthur Bentley's scale drawings of the Ho-229
- Construction of a model of the Horten IX including CAD files (in German)
- "Horten: Two brothers, one wing"
- "Photo: Horten Ho 229 flying over Göttingen, Germany. 1945.".
"Hitler's Stealth Fighter" Re-created
Brian Handwerk
for National Geographic News
for National Geographic News
June 25, 2009
Top stealth-plane experts have re-created a radical, nearly
forgotten Nazi aircraft: the Horten 2-29, a retro-futuristic fighter that
arrived too late in World War II to make it into mass production. (See
Hitler's stealth fighter in pictures.)
The engineers' goal was to determine whether the so-called stealth fighter
was truly radar resistant. In the process, they've uncovered new clues to just
how close Nazi engineers were to unleashing a jet that some say could have
changed the course of the war.To replicate the Ho 2-29 late last year for a documentary premiering Sunday, a team from the Northrop Grumman defense-contracting corporation used original Nazi blueprints (see re-created blueprints of Hitler's stealth fighter) and the only surviving Ho 2-29, which has been stored in a U.S. government facility for more than 50 years.
The all-wing Ho 2-29 looked more like today's U.S. B-2 bomber (B-2 bomber picture)—or something from a Star Wars prequel—than like any other World War II aircraft. Made primarily of wood and powered by jet engines, the plane was designed for speeds of up to 600 miles an hour (970 kilometers an hour).
Armed with four 30mm cannons and two 500-kilogram (1,100-pound) bombs, the planned production model was also meant to pack a punch.
A Ho 2-29 prototype made a successful test flight just before Christmas 1944. But by then time was running out for the Nazis, and they were never able to perfect the design or produce more than a handful of prototype planes.
Determining the Horten's stealth capabilities could help reveal what might have happened if the Ho -229 had been unleashed in force.
Last Minute "Miracle Weapon"?
As Hitler's Thousand-Year Reich crumbled, the führer clung to dreams of secret Wunderwaffen—miracle weapons (more Nazi secret weapons).
Enter the unconventional Horten brothers, who were at work on one such weapon.
Lead designer Reimar Horten was a glider designer "obsessed with the all-wing [design] because of the possibilities it created for low drag and exceptional performance," said Florida-based aviation historian David Myhra, who interviewed the Horten pair numerous times from the early 1980s until their deaths in the late 1990s.
Walter Horten was a military man who had lost hundreds of
Luftwaffe colleagues during the Battle of Britain in 1940.
"He was burning with revenge and felt the need for a plane that would be pretty much invisible to Britain's Chain Home radar system. That's what he wanted his brother to design."
The result of their collaboration was unique among Luftwaffe designs.
"It has no vertical surfaces for stability or control. Every exterior surface of that aircraft contributes lift," said Russell Lee, curator for the only remaining Horten 2-29 aircraft, at the National Air and Space Museum's Paul E. Garber Preservation, Restoration and Storage Facility outside Washington, D.C.
"That had been tried before and failed time and time again," Lee said. "Reimar Horten took the idea further and made it more practical than any other designer really up until the B-2."
(Interactive: Explore Hitler's stealth fighter.)
Re-creating Hitler's Stealth Fighter
To determine once and for all whether the Ho 2-29 had stealth capabilities, experts first examined the surviving 2-29 and probed it with a portable radar unit based on World War II radar tech.
Then, in the fall and winter of 2008, they set about building the full-scale re-creation at a restricted-access Northrop Grumman testing facility in California's Mojave Desert.
The construction team embraced historic materials and techniques, and the Horten 2-29 replica, like the original, is made largely of wood and bonded with glue and nails.
Unlike the original, however, the replica wasn't built to fly, though it did soar, after a fashion.
The new craft's body was constructed around a rotor, which allowed the replica to be manipulated atop a five-story-tall column. There, in January 2009, the craft was subjected to World War II-style radar.
Initiated by Michael Jorgensen, writer and producer of the National Geographic Channel documentary Hitler's Stealth Fighter, the construction and testing of the replica was funded by Northrop Grumman. (The National Geographic Channel is part-owned by the National Geographic Society, which owns National Geographic News.)
Stealth by Accident?
Stealth aircraft rely on shapes that prevent radar waves from bouncing back to their sources and on materials that absorb radar energy (stealth-plane time line).
Some experts, like the Garber facility's Lee, question the Hortens' postwar claims that their plane had been intended as a stealth plane.
"My take on it is that their goal at the time was to meet requirements for speed and range," Lee said. "The all-wing concept was [Reimar Horten's] baby, and he designed the shape for aerodynamic reasons—he never started talking about radar until after the war.
"Reimar talked about a sawdust and carbon coating to absorb radar energy, but we found no evidence of that on the Horton that we have here," Lee added.
But Myhra argues that the plane was indeed intentionally designed for stealth.
"When I talked with Walter Horten in the 1980s and '90s he always referred to his aircraft as low-observable," said Myhra, a former aerospace scientist.
Horten also told Myhra about his time in a Berlin think tank, when he had learned about radar evasion from Nazi navy officers hoping to camouflage their submarines.
Walter claimed to have brought this information to his brother so that it could be part of the plane's design.
"These guys knew about this stuff," Myhra said. "They were probably the only people in the entire German aviation community that were pursuing this line of thought."
Proof of Stealth?
Radar tests on the replica show that the plane's radical, smooth design would indeed have given it a significant advantage against radar, according to Tom Dobrenz, a Northrop Grumman expert in stealth, or "low observable," technology, who led the Horten replica project.
In short: The Horten 2-29 looks to have been the world's first stealth fighter.
But was it meant to be?
"I believe they were [mainly] driven by the aerodynamic side of it," Dobrenz said.
Still, radar tests on the surviving Ho 2-29 revealed "that they put some kind of carbon-type material in between the layers of plywood on the plane's leading edges," he said.
"Personally, I cannot understand that being for anything other than doing something to [defeat] radar." Even so, Dobrez added, "I'm not so sure that they had any clue what it was going to do or whether it was going to work or not."
"Could Have Been a Game Changer"
At least one major mystery remains: How would Hitler's stealth fighter have affected the outcome of World War II, had the plane made it to mass production?
"This design gave them just about a 20 percent reduction in radar range detection over a conventional fighter of the day," Dobrenz said.
According to tests on the replica, World War II British radar would have picked up the Horten over the English Channel at about 80 miles (129 kilometers) out, versus 100 miles (160 kilometers) for a conventional World War II fighter.
But because of the Ho 2-29's tremendous speed, the time from detection to target—the British mainland—would have been lowered from the usual 19 minutes to just 8 minutes, making it difficult for Allied defenders to respond.
"Probably, for at least a short amount of time, it could have been a game changer, until a counter was developed for it," Dobrenz said.
But the Ho 2-29 design was far from perfect.
World War II-era jet engines were unreliable, for one thing. For another, the lack of stabilizing vertical surfaces—a bane of all-wing designs, past and present—resulted in frequent lurches, making sharp shooting and accurate bomb delivery that much harder.
In a different place and time, with further development, the promising Horten 2-29 might have made a difference.
But by early 1945, aviation historian George Cully said, "The Germans had run out of pilots, petroleum, and time."
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