The Horten Ho IX was a late-WWII prototype flying wing fighter/bomber, designed by Reimar and Walter Horten and built by Gothaer Waggonfabrik. It was the first natural flying wing powered by a turbojet, and was the first airplane designed to incorporate what became known as stealth technology. It was a personal favorite of German Luftwaffe chief Reichsmarschall Hermann Göring, and was the only plane to come close to meeting his "1000, 1000, 1000" performance requirements. Its speed was estimated at 1,024 km/h (636 mph) and its ceiling 15,000 meters In the early 1930s, the Horten brothers had become interested in the flying wing structure as a method of improving the performance of gliders. The German government was funding glider clubs at the time because production of military airplane 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 drag. 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 layout proposals to produce a bomber that was capable of carrying a 1,000 kg (2,200 lb) load over 1,000 km (620 mi) at 1,000 km/h (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 simply no way to meet these goals — the new Junkers Jumo 004B turbojets could give the required speed, but had excessive fuel consumption. The Hortens deduced that the low-drag flying wing layout could meet all of the goals: by cutting down the drag, cruise power could be lowered to the point where the range requirement could be met. They put forward their private project, the Ho 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 plane would also be useful as a fighter due to its estimated top speed being significantly higher than that of any Allied airplane. The Ho 229 jet 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 airplane had a 12.6g ultimate load rating. The wing's chord/thickness ratio ranged from 15% at the root to 8% at the wingtips. Control was achieved with 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 roll than would a single spoiler system. The plane utilized retractable tricycle landing gear, with the nosegear on the first two prototypes sourced from a He 177's tailwheel system. A brake parachute slowed the airplane upon landing. The pilot sat on a primitive ejection seat. After the war Reimar Horten said he mixed charcoal dust in with the wood glue to absorb electromagnetic waves (radar), which he believed could shield the plane from detection by British early warning ground-based radar known as Chain Home. In the modern era it became known that a flying wing layout will reduce the plane's radar cross-section, though no wartime documents survive to confirm that the Hortens were working specifically on a radar-defeating airplane. In a 1950 document Horten brought up the possibility that their design may have such benefits, and the document specifically mentions reduced detection by sight and radar. It is now known that a jet powered flying wing model such as the Horten will have a smaller radar cross-section than a conventional WWII-era twin engine airplane: with wings blended into the fuselage, no large propeller disks, or vertical and horizontal tail surfaces. Horten's theories were tested by Northrop-Grumman in 2008 and found to have been successful, resulting in a radar cross section only 40% that of conventional planes. The first Ho IX V1, an unpowered glider, flew on 1 March 1944. Flight results were very favorable, but there was a landing accident when the pilot attempted to land without first retracting an instrument-carrying pole extending from the plane. The model 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 a system to carry cold air to cool the jet engine's outer casing, as the wing was made of wood. The Horten Ho IX V1 was followed in December 1944 by the Junkers Jumo 004-powered Ho IX V2; the BMW 003 engine was preferred but unavailable at the time. Göring believed in the design and ordered a production series of 40 plane from Gotha Waggonfabrik with the RLM designation Horten 229 flying wing even though it had not yet taken to the air under jet power. The first flight of the Ho IX V2 was made in Oranienburg on 2 February 1945. All subsequent test flights and development were done by the Gotha Waggonfabrik. By this time, the Horten brothers were working on the Amerika Bomber and they 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 Ho 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 Ho IX V2 undertook a simulated "dog-fight" with an Messerschmitt Me 262. It is stated that the Ho IX V2 out performed 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 a flight time of around 45 minutes, at an altitude of some 800m, one of the Jumo 004 turbojet engines developed a problem, caught fire and stopped. Ziller was seen to dive the airplane and pull up several times in an attempt to re-start the engine and save the precious prototype plane. Ziller undertook a series of four 360 degree turns with its wings banked 20 degrees. Ziller did not use his radio and did not eject from the plane. He may already have been unconscious as a result of the fumes from the burning engine. The airplane crashed just outside the boundary of the airfield. Ziller was thrown from the aircraft on impact and hit a large tree. He was killed instantly. The prototype aircraft was completely destroyed. Despite this setback the project continued with sustained energy. On 12 March 1945, the Ho 229 jet was included in the Jäger-Notprogramm for accelerated production of inexpensive "wonder weapons." The prototype workshop was moved to the Gothaer Waggonfabrik (Gotha) in Friedrichroda. In the same month work commenced on the third prototype, the Ho 229 jet V3. The V3 was larger than previous prototypes, the shape was modified in various areas, and it was meant to be a template for the pre-production series Horten jet A-0 day fighters, of which 20 machines had been ordered. V3 was powered by two Jumo 004C engines, and could carry armament of two MK108 30mm cannon in the wing roots. Work had also started on the two-seat Horten jet V4 and Horten jet V5 night-fighter prototypes, the Horten 229 flying wing V6 armament test prototype, and the Ho-229 jet wing V7 two-seat trainer. During the final stages of the war, the U.S. military initiated Operation Paperclip, which was an effort by the various intelligence agencies to capture advanced German weapons research, and to deny that research to advancing Soviet troops. A Horten glider and the Ho 229 jet V3, which was undergoing final assembly, were secured and sent to Northrop Corporation in the United States for evaluation. Northrop was chosen because of their experience with flying wings, inspired by the Horten brothers' pre-war record-setting glider. Jack Northrop had been building flying wings since the N-1M in 1939. Engineers of the Northrop-Grumman Corporation had long been interested in the Horten 229 flying wing, and several of them visited the Smithsonian Museum's facility in Silver Hill, Maryland in the early 1980s to study the V3 airframe. In early 2008, Northrop-Grumman paired up television documentary producer Michael Jorgensen, another long-time fan of the airplane, 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. A team of engineers from Northrop-Grumman ran electromagnetic tests on the V3's multilayer wooden center-section nose cones. The cones are three-fourths of an inch (19mm) 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 slowed down considerably as it passed through the cone. In an experiment to determine the stealth characteristics of the model, Northrop-Grumman built a full-size reproduction of the V3, incorporating a replica glue mixture in the nose section. 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 used by the Chain Home radar network of the British in the early 1940s. RCS testing showed that an Horten jet approaching the English coast from France flying at 885 km/h (550 mph) at 15 - 30 metres (50 - 100 ft) above the water would have been visible at a distance of 80% that of a Bf 109. This implies an RCS of only 40% that of a Bf 109, from the front at the Chain Home frequencies. The most visible parts of the plane were the jet inlets and the cockpit, but caused no return through smaller dimensions than the CH wavelength. The Battle of Britain (German: Luftschlacht um England or Luftschlacht um Großbritannien) is the name given to the air war waged by the German Air Force (Luftwaffe) against the United Kingdom during the summer and autumn of 1940. The aim of the campaign was to gain air superiority over the Royal Air Force (RAF), especially Fighter Command. The name derives from a famous speech delivered by Prime Minister Winston Churchill in the House of Commons: "The Battle of France is over. I expect the Battle of Britain is about to begin..." The Battle of Britain was the first primary campaign to be fought entirely by air forces, and was also the largest and most sustained aerial bombing warto that date. From July 1940 coastal shipping convoys and shipping centers, such as Portsmouth, were the main targets; one month later the Luftwaffe shifted its attacks to RAF airfields and infrastructure. As the combat progressed the Luftwaffe also targeted aircraft factories and ground infrastructure. Eventually the Luftwaffe resorted to attacking areas of political significance and using terror bombing tactics. The inability of Germany to achieve its objectives of destroying Britain's air defenses, or forcing Britain to negotiate an armistice or an outright surrender, is considered its first major defeat and one of the imperative turning points in the war. If Germany had gained air superiority with the Luftwaffe, Adolf Hitler might have launched Operation Sea Lion, an amphibious and airborne invasion of Britain. The Luftwaffe's Messerschmitt Bf 109E and Messerschmitt Bf 110C squared off against the RAF's workhorse Hurricane Mk I and the less numerous Spitfire Mk I. The Bf 109E had a better climb rate and was 10 to 30 mph faster than the Hurricane, depending on altitude. In September 1940 the more powerful Mk IIa series 1 Hurricanes started entering service although only in small numbers. This version was capable of a maximum speed of 342 mph, some 25 to 30 mph faster than the Mk I. The accomplishment of the Spitfire over Dunkirk came as a surprise to the Jagdwaffe, although the German pilots retained a strong belief that the 109 was the superior fighter. However, the Bf 109E had a much larger turning circle than either the Hurricane or the Spitfire. The two British fighters were equipped with eight Browning 303 machine guns, while most Bf 109Es had two machine guns and two wing cannons. The Messerschmitt Bf 109E and the Spitfire were superior to each other in key areas; for instance, at some altitudes, the Bf 109 could out-climb the British fighter. In general, though, as Alfred Price noted in The Spitfire Story: ...the differences between the Spitfire and the Me 109 in performance and handling were only marginal, and in a combat they were almost always surmounted by tactical considerations: which side had seen the other first, had the advantage of sun, altitude, numbers, pilot ability, tactical situation, tactical co-ordination, amount of fuel remaining. The Bf 109 was also used as a fighter-bomber—the E-4/B and E-7 models could carry a 250 kg bomb under the fuselage. The Messerschmitt Bf 109, unlike the Stuka, could fight on equal terms with RAF fighters after releasing its ordnance. At the start of the attack, the twin-engine Messerschmitt Bf 110 long range Zerstörer ("Destroyer") was also expected to engage in air-to-air combat while escorting the Luftwaffe bomber fleet. Although the Messerschmitt 110 was faster than the Hurricane and almost as fast as the Spitfire, its lack of maneuverability and acceleration meant that it was a failure as a long-range escort fighter. On 13 and 15 August, 13 and 30 aircraft were lost, the equivalent of an entire Gruppe, and the type's worst losses during the action. This trend continued with a further eight and 15 lost on 16 and 17 August. Göring ordered the Bf 110 units to operate "where the range of the single-engined machines were not sufficient". The most productive role of the Messerschmitt Bf 110 during the battle was as a Schnellbomber (fast bomber). The Bf 110 usually used a shallow dive to bomb the target and escaped at high speed.One unit, Erprobungsgruppe 210, proved that the Messerschmitt Bf 110 could be used to good effect in attacking small or "pinpoint" targets. The RAF's Boulton Paul Defiant had some initial success over Dunkirk because of its resemblance to the Hurricane; Luftwaffe fighters attacking from the rear were surprised by its unusual gun turret. However, during the Battle of Britain, this single-engine two-seater proved to be hopelessly outclassed. For various reasons, the Defiant lacked any form of forward firing armament and the heavy turret meant that it could not out-run or out-maneuver either the Bf 109 or the Bf 110. By the end of August, after disastrous losses, the aircraft was withdrawn from daylight service. There has been some criticism of the decision to keep these aircraft (along with the Fairey Battles in RAF Bomber Command) operational instead of retiring and scrapping them, allowing their Merlin engines to be turned over to fighters and their pilots (about three thousand in all) to be retrained on Hurricanes, thereby freeing large numbers of high-time, combat-experienced Hurricane pilots for Spitfires.The Luftwaffe's four primary bombers were the Heinkel He 111, Dornier Do 17, and Junkers Ju 88 for level bombing, and the Junkers Ju 87 Stuka for diving attacks. The Heinkel He 111 was used in greater numbers than the others during the conflict and is better known, partly due to its distinctive wing shape. Each level bomber also had a few reconnaissance versions that were used during the battle. Although successful in previous Luftwaffe engagements, the Stuka suffered heavy losses in the Battle of Britain, particularly on 18 August, due to its slow speed and vulnerability to Spitfire fighter interception after the dive bombing. As a result of the losses and limited payload and range, Ju87 Stuka units were largely removed from operations over England and concentrated on shipping instead until they were re-deployed to the Eastern Front in 1941. The Ju87 Stuka dive bombers returned on occasion, such as on the 13 September attack on Tangmere airfield. The remaining three bomber types differed in their capabilities; the Heinkel 111 was the slowest, the Ju 88, once its mainly externally carried bomb load was dropped, was the fastest, and the Do 17 had the smallest bomb load. All three bomber types suffered heavy losses from British fighters, but the Ju 88 disproportionately so. Later in the conflict, when night bombing became more frequent, all three were used. However, due to its reduced bomb load, the lighter Do 17 was used less than the He 111 and Ju 88 for this purpose. On the British side, three bombers were mostly used on night operations against targets such as factories, invasion ports and railway centers; the Armstrong Whitworth Whitley, the Handley-Page Hampden and the Vickers Wellington were classified as heavy bombers by the RAF, although the Hampden was a medium bomber comparable to the He 111. The twin-engined Bristol Blenheim and the obsolescent single-engined Fairey Battle were both light bombers; the Blenheim was the most numerous of the aircraft equipping RAF Bomber Command and was used in attacks against shipping, ports, airfields and factories on the continent by day and by night, while the Battle was rarely used on operations. Before the war, the RAF's processes for selecting potential candidates were more concerned with social standing than actual aptitude. By summer 1940, there were about 9,000 pilots in the RAF for approximately 5,000 aircraft, most of which were bombers. However, the problem of pilot shortage was self-inflicted, due to inefficiencies in training and assignment. With aircraft production running at 300 each week, only 200 pilots were trained in the same period. In addition, more pilots were given to squadrons than there were aircraft. Another problem was that only about 30% of the 9,000 pilots were assigned to operational squadrons; 20% of the pilots were involved in conducting pilot training, and a further 20% were undergoing further instruction, like those offered in Canada and in Southern Rhodesia to the Commonwealth trainees, although already qualified. The rest were assigned to staff positions, since RAF policy dictated that only pilots could make many staff and operational command decisions, even in engineering matters. At the height of fighting, and despite Churchill's insistence, only 30 pilots were released to the front line from administrative duties. For these reasons, the RAF had fewer experienced pilots at the start of the battle, and it was the lack of accomplished pilots in the fighting squadrons, rather than the lack of aircraft, that became the greatest concern for Air Chief Marshal Hugh Dowding, Commander of Fighter Command. Drawing from regular RAF forces and the Auxiliary Air Force and the Volunteer Reserve, the British could muster some 1,103 fighter pilots on 1 July. Replacement pilots, with little flight training and often no gunnery training, suffered high casualty rates. Due mostly to more productive training, the Luftwaffe could muster a larger number (1,450) of more experienced fighter pilots. Drawing from a cadre of Spanish Civil War veterans, they had comprehensive courses in aerial gunnery and instructions in tactics suited for fighter-versus-fighter combat. Luftwaffe training manuals also discouraged heroism, stressing the utmost importance of attacking only when the odds were in the pilot's favor.