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Saucers of the Third Reich

There is no question that the Germans produced a number of scientific breakthroughs in their quest for war technology during World War II. The V-1 buzz bombs - a forerunner of today's cruise missiles - and the V-2 rockets that terrorized London are two of the most famous examples, along with the Messerschmitt 262, the world's first operational jet fighter.

As respectful British historian Barre Pitt noted:

The Nazi war machine swung into action utilizing as much as it could of the most up-to-date scientific knowledge available, and as the war developed the list of further achievements grew to staggering proportions. From guns firing shells of air to detailed discussions of flying saucers, from beams of sound that were fatal to a man at 50 yards to guns that fired around corners and others that could 'see in the dark' - the list is awe-inspiring in its variety.


Secret German Aerial Craft

We know from eye-witness accounts and recovered records that the German military machine was making great strides in experimental research. So successful in pioneering rocketry were they that immediately after the war, tons of material plus hundreds of scientists were siphoned off by the allies -- both east and west.


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In seems that no idea was considered too radical among designers of the German aircraft industry. The team who worked for Blohm und Voss developed four new aircraft between February and April 1944. The first design of this quartet was given the basic Projekt No. P-192. The arrangement of the airscrew/engine installation is unusual, but it had the advantage that the motor was mounted near the aircraft's centre of gravity. A tail-less craft, Projekt No. P-208 was dubbed the "Arrow Wing", and was flight-tested in the summer of 1944.

Just as interesting was the Sänger-Bredt rocket bomber project which was first instigated in 1936 (incredibly the first man-carrying rocket flight is credited to F. Stahmer in 1928, and the second to F. von Opel in 1929, both taking place in Germany), and theoretical work on the airframe and much practical research on its diesel-oil/liquid oxygen-fuelled motor was continued until 1941-42 at Trauen near Fassberg. A rocket-boosted sledge catapulted the bomber into the air after accelerating along a track 1.72 miles long and with the booster rockets consuming their fuel in 11 seconds burning time, 30 seconds after lift-off the bomber was already at a height of 32,800 ft. The pilot was then required to fire his own rocket motor, and the Sänger-Bredt rocket would then climb to a height of 90 miles where a speed of 13,500 mph was to be attained. The fuel consumed, the aircraft would then descend in a shallow glide and was expected to bounce on contact with the denser air layers surrounding the earth. The range depended on bomb load, but if a peak height of 155 miles could be reached after launching, it was calculated that the aircraft could easily fly a distance of 14,650 miles in a series of ever-decreasing ricochets with a long final glide back to base. New York could be hit with a 6-ton load, the round trip from Germany taking 1 hr, 44 min. This so-called "antipodal bomber" was finally shelved in 1942 . . . but it did provide the basic idea from which the Soviet T-4A and American Dynasoar were developed.



Near Kircheim on Teck in April 1945 a strange sight could be seen: ten steel launching ramps each 80 ft. in length pointing nearly vertically into the sky. At the base of each was what appeared to be a stubby, winged missile. These were in fact the first operational examples of a unique piloted, rocket-driven aerial vehicle called the Bachem Ba 349 Natter ("Adder"). The Natter was conceived by Dr Eric Bachem of the Bachem Werke in Würtemberg, and work on the project began in August 1944. Largely built of wood, the machine was a cheap, simple design which could be nailed and glued together by mechanics and other non-aircraft workers. After a nearly vertical launch on the power of its bi-fuel rocket motor and four jettisonable solid-fuel rocket motors, the Natter was expected to reach an altitude of 35,800 ft. in one minute. It was planned to launch the rocket planes as U.S. heavy bombers approached, guiding them automatically from the ground to within a mile of the enemy. The pilot would then taken over control, close the range and fire the nose battery of twenty-four R4M missiles in a single salvo; his task over, he was then to bale out of the armoured cockpit. Simultaneously the rear fuselage, containing the valuable rocket motor, would break off and be parachuted to earth, where the motor could be used again in a new Natter. Three manned test launches were successfully made, and thirty-six Ba 349As were completed, but the ten set up at Kircheim on Teck had to be destroyed when an American armoured unit approached the launching site. The sole Ba 349B was found by the Russians in a factory in Thuringia, where it had been sent as a production prototype.



Germany's Messerschmitt Me 163B rocket fighter aircraft, the Komet, was the world's first operational rocket-driven fighter, but was severely handicapped by a very limited endurance. Less than 370 of the little fighters had been completed by the end of the war, and more advanced versions never passed the prototype stage. Hitler belatedly realised the importance of the jet fighter and in March 1945 S.S. General Hans Kammler was put in charge of the entire jet aircraft production program.

It begs the question then, If Hitler and his High Command really were in possession of aerial craft so far in advance of anything else on earth, why would they not have used such machines in order to reverse the fortunes of war? There were numerous blunders made in Germany throughout WW2 which included cancelling promising prototype aircraft. The few that appear on this page, while representing remarkable vision and feats of engineering, fall easily within the bounds of any country's achievements when all its resources are focused on producing only one result. By the spring of 1944, Germany was already feeling the crippling effects of a fuel shortage and could barely muster adequate sorties against raiding allied aircraft. An appropriate time, surely, for the unleashing of the Kugelblitz.


There is in circulation a photograph which purports to show a disc-shaped flying craft in the sky above Prague during the mid-1940s. Schriever and Habermohl, the scientists some claim to be responsible for its development, reportedly took off in the first flying disc on February 4, 1945, and climbed to an altitude of 40,000 feet in three minutes. After the war this story was quoted widely in books, with further claims that the machine reached a speed of 1,300 mph. Apparently another flying disc development by the same two scientists would have produced a craft capable of 3,000 mph, if it had reached completion.

History of German Rocketry in World War II

While some German technology was less developed than imagined at the time, some technologies were dangerously near to completion stage which could have reversed the war's outcome. Secret German weapons nearing completion in 1945 included the Messerschmitt 163 Komet and the vertically launched Natter rocket fighters, the jet-powered flying wing Horten Ho-IX and the delta-winged Lippisch DM 1.

Another secret weapon that might account for some of the "foo-fighter" reports was an antiradar, unmanned device called the Feuerball or Fire Ball. Piloted by remote control, the Fire Ball was designed to interfere with the ignition systems and radar operation of Allied bombers. According to author Renato Vesco, the Feuerball was "a highly original flying machine." It was circular and armored, resembling a tortoise shell, and was powered by a special turbojet engine, whose principles of operation, generated a great halo of luminous flames, Radio controlled at the moment of take-off, it then automatically followed enemy aircraft, attracted by their exhaust flames, and approached close enough without collision to wreck their radar gear.

Vesco claimed that the basic principles of the Feuerball were later applied to a "symmetrical circular aircraft" known as the Kugelblitz, or Ball Lightning, automatic fighter. He said this innovative craft was destroyed after a "single lucky wartime mission" by retreating SS (Schutzstaffel) or Defense Force troops and later kept secret from the Americans and Russians by the British military.

British author W. A. Harbinson wrote two novels based on the idea that the Nazis developed a flying saucer and secreted them away after the war in a hidden base in Antarctica. He claimed that he got his ideas after discovering postwar German articles concerning a former Luftwaffe engineer, Rudolf Schriever. According to articles gleaned from Der Spiegel, Bild am Sonntag, Luftfahrt International, and other German publications. Harbinson learned that Schriever claimed to have designed a "flying top" prototype in 1941, which was test-flown in June 1942. In 1944, Schriever said he constructed a larger jet version of his circular craft with the help of scientists Klaus Habermohl, Richard Miethe, and an Italian, Dr. Giuseppe Belluzzo. Drawings of this saucer were published in the 1959 British book German Secret weapons of the Second World War by Maj. Rudolf Lusar.

Lusar described the saucer as a ring of separate disks carrying adjustable jets rotating around a fixed cockpit. The entire craft had a height of 105 feet and could fly vertically or horizontally, depending on the positioning of the jets.

Schriever claimed that his "flying disc" had been ready for testing in early 1944 according to the novelist Harbinson. But with the advance of the allies into Germany, the test had been canceled, the machine destroyed, and Schriever's designs either mislaid or stolen. However. Schriever's story is disputed by an alleged eyewitness Georg Klein, who claimed that he had actually seen the test flight of the Schriever disc on February 14, 1945.


Schriever is reported to have died in the late 1950s, and according to a 1975 issue of Luftfahrt International, notes and sketches concerning a large flying saucer were found in his effects. The periodical also stated that Schriever maintained until his death that his original saucer concept must have been operational prior to the war's end. This possibility is acknowledged by British author Brian Ford.


Another candidate for an inventor of a German UFO was the Austrian inventor Viktor Schauberger, who reportedly was kidnapped by the Nazis and was forced to design a number of "flying discs" in 1940 using a flameless and smokeless form of electromagnetic propulsion called "diamagnetism." Schauberger also reportedly worked for the US government for a short time after the war before dying of natural causes. Shortly before his death, he was quoted as saying, "They took everything from me. Everything." No one knew for certain who he meant--the Nazis or the Allies.

 

While any number of books have strongly suggested that The Nazi hierarchy was involved in occult practices, there is no question that the Germans were experimenting with a wide variety of innovative aircraft and propulsion systems toward the end of the war. There is little doubt that they at least contemplated building a flying saucer. There are tantalizing bits of evidence that Nazi Germany indeed added a flying disc to its inventory of secret weapons. However, there is no indication of what became of it.

The solution to this puzzle might be found by studying the man in charge of Germany's high-tech weapons programs - SS- Obergruppenführer Dr. Hans Kammler. In mid-1943, SS Chief Heinrich Himmler sent a letter to Germany's minister for armaments and munitions, Albert Speer:

Reichsführer…..do hereby take charge of the manufacture of the A-4 instrument.

The A-4 was later designated by Hitler as the V-2--V for Vengeance weapon, the V-1 buzz bomb being the first. The V-2 was Germany's most secret high-tech weapons system.

Himmler then placed Kammler in overall command of the rocket program.

According to Speer, Kammler worked his way into all phases of the V-2 program until Hitler finally put him in charge of all air armaments, including any possible secret saucer project. He became commissioner general for all important weapons just weeks before the end of the war. As the war drew to a close, Himmler's SS gradually assumed total control over Germany's weaponry production and research.

With Kammler on the V-2 project were Wernher von Braun, who after the war headed America's National Aeronautics and Space Administration, and his superior, Lufftwaffe Maj. Gen. Walter Dornberger, who later became vice-president of Bell Aircraft Company and of Bell Aerosystems Company in the United States".

Alarmed by the progress on the V-2 rockets, Britain's Bomber command sent 597 bombers on the night of August 16-17, 1943, to raid Peenemünde, Germany's top-secret rocket facility built on an island at the mouth of the Oder River near the border of Germany and Poland. Because so much of Peenemünde was underground or well camouflaged, much was left undamaged. After the raid, it was quickly realized by the Germans that some of the facility needed to be dispersed throughout . Theoretical development moved to Garmisch-Partenkirchen, development went to Nordhausen and Bleicherode, and the main wind-tunnel and ancillary equipment went down to Kochel, some twenty miles south of Munich. It can be noted that a certain portion of top-secret Nazi weaponry was moved to an area near Blizna, Poland. Kammler, von Braun, Dornberger, and company worked feverishly to perfect the V-2s and other secret weapons, Himmler was working on separating his SS from normal party and state control. In the spring of 1944 Hitler approved Himmler's proposal to build an SS-owned industrial concern in order to make the SS permanently independent of the state budget.

In moves that were to be emulated in later years by the Central Intelligence Agency, SS leaders created a number of business fronts and other organizations--many using concentration-camp labor--with an eye toward producing revenue to support SS activities. SS officers neither required nor desired any connection with Germany.


Just five days before World War II broke out, on August 27, 1939, the He 178 became the world's first jet aircraft to take flight.

Developed from the He 178 the He 280 was the world's first jet fighter and flew in early 1941. Its development was delayed by engine problems and political indifference, and when the jet program was finally pressed ahead, it was abandoned in favour of the more advanced Me 262.

Only nine were built. The world's first jet fighter, the Heinkel He 280, took the air on March 30, 1941 in a flight lasting just three minutes - this was a scant six weeks before a specially built Gloster plane (E.28/39) flew using Frank Whittle's turbojet design. This took place on May 15, 1941

Hitler spent a great deal of time asking for "wonder weapons" that could win the war at a stroke. 

German research was indeed very active throughout the war, perhaps too active since the vast number of weapon and secret projects diluted Germany's limited resources.

Arguably a wonder weapon existed well before the end of the war in the form of a jet powered interceptor that was 100 mph (240 km/h) faster than any allied plane. The superb Messerschmitt Me 262 was the world's first jet fighter to enter operational service. With four 30mm guns in the nose of the plane the 262 packed devastating firepower.

But progress on the Me 262 was slow and tortuous with a marked lack of interest by the Luftwaffe for the first three years of the war and significant problems with the Jumo turbo-jets that would power the airframe. On November 2, 1943 Herman Göring paid a visit to the Messerschmitt works at Augsburg and asked Messerschmitt how many bombs the jet plane could carry. Later, on the 26 of November, Hitler attended an airshow at Insterburg and saw the jet aircraft for the first time and was suitabily impressed. But much to the horror of fighter General Adolf Galland and others present Hitler announced that this new weapon was to be built as a Blitz bomber and not a fighter. This marked a major setback to the eventual deployment of the Me 262 as a fighter in good numbers.

Despite Hitler's orders only one Me 262 was fitted with bomb racks and equipped to be a "Blitz" bomber. The rest were produced as fighter/ interceptors. On May 23, 1944 Hitler learned that the Me 262 was being manufactured only as a fighter. In a rage he removed Erhard Milch from head of procurement for the Luftwaffe and ordered that all existing Me 262 jets be converted to Blitz bombers.

Although only 100-300 actually flew operations and fought against Allied aircraft they downed far more than 100 enemy planes.



Why Jet Power?

 

Even before the war it was becoming apparent to some aircraft designers that propeller driven aircraft were nearing the limits of their possible performance. With the world speed record smashed by the Heinkel He 100 and shortly after by the Me 209 it was clear that no matter how much power a piston-engine plane possessed it could only approach the speed of sound, an entirely new method of propulsion would be needed to achieve greater performance.

 

Three different methods seemed possible: rocket, turbo jet and the 'ram' jet. All of these provide forward thrust by constant recoil verses the propeller which literally drags a plane through the air. A rocket motor works independent of the atmosphere carrying its own oxygen and fuel but also consuming them in a relatively short time. The 'ram' jet is simple in concept with the force of air ramming into the engine being sufficient for fuel to be introduced and ignited. The hot gases shooting through a tail pipe push the engine and the attached plane forward. Unfortunately, a 'ram' jet doesn't begin to function unless its already travelling at a decent speed, requiring a second power plant to bring the aircraft up to speed for the 'ram' jet to take over.

 

A turbo jet is more complex requiring a rapidly spinning compressor to push enough air into the combustion chamber so the engine can generate sufficient thrust. The biggest obstacle to realizing the dream of jet powered flight was in producing a compact turbojet that gave good thrust while standing up to extreme heat and vibration.

 

Frank Whittle in England and Hans von Ohain of Germany developed the first turbo-jet engines independent of each other


The principle of all jet engines is essentially the same. The engine draws air in at the front and compresses it. The air then combines with fuel and the engine burns the resulting mixture. The combustion greatly increases the pressure of the gases which are then exhausted out of the rear of the engine. The process is similar to a four stroke cycle, but with the processes - induction, compression, ignition and exhaust - taking place continuously. The engine generates thrust because of the acceleration of the air through it - the equal and opposite force this acceleration produces (Newton's third law) is thrust. A jet engine takes a relatively small mass of air and accelerates it by a large amount, whereas a propeller takes a large mass of air and accelerates it by a small amount. The efficiency of the process, like any heat engine, is defined as the ratio of the compressed air's volume to the exhaust volume.

 

The advantage of the jet engine is its efficiency at high speeds (especially supersonic speeds) and high altitudes. On slower aircraft, a propeller (powered by a gas turbine), commonly known as a turboprop is more common. Very small aircraft generally use conventional piston engines to drive a propeller.

 

History


The earliest attempts at jet engines were hybrid designs, in which an external power source supplied the compression. In this system (called a thermojet by Secondo Campini) the air is first compressed by a fan driven by a conventional gasoline engine, mixed with fuel, and then burned for jet thrust. Three known examples of this type of design were the Henri Coanda's Coanda-1910 aircraft, the much later Campini Caproni CC.2, and the Japanese Tsu-11 engine intended to power Ohka kamikaze planes towards the end of World War II. None were entirely successful, and the CC.2 ended up being slower than a traditional design with the same engine.

 

The key to the useful jet engine was the gas turbine, used to extract energy to drive the compressor from the engine itself. Work on such a "self-contained" design started in England in 1930 when Frank Whittle submitted patents for such an engine (granted in 1932) using a single turbine stage in the exhaust to drive a centrifugal compressor. In 1935 Hans von Ohain started work on a similar design in Germany, seemingly unaware of Whittle's work.

 

Ohain approached Ernst Heinkel, one of the larger aircraft industrialists of the day, who immediately saw the promise of the design. Heinkel had recently purchased the Hirth engine company, and Ohain and his master machinist Max Hahn were set up there as a new division of the Hirth company. They had their first HeS-1 engine running by 1937. Unlike Whittle's design, Ohain used hydrogen as fuel, which he credits for the early success. Their subsequent designs culminated in the HeS-3 of 1,100 lb (5 kN), which was fitted to Heinkel's simple He 178 airframe and flew in August 1939, an impressively short time for development. The He 178 was the world's first jetplane.

 

In England, Whittle had significant problems in finding funding for research, and the Air Ministry largely ignored it while they concentrated on more pressing issues. Using private funds he was able to get a test engine running in 1937, but this was very large and unsuitable for use in an aicraft. By 1939 work had progressed to the point where the engine was starting to look useful, and Whittle's Power Jets Ltd. started receiving Air Ministry money. In 1941 a flyable version of the engine called the W.1, capable of 1000 lb (4 kN) of thrust, was fitted to the Gloster E28/39 airframe, and flew in May 1941.

 

One problem with both of these early designs was that the compressor works by "throwing" air outward from the intake to the sides of the engine, where the air is then compressed by being "crushed" up against the side. This leads to a very large cross section for the engine, as well as having the air flowing the wrong way after compression - it has to be collected up and "bent" to flow to the rear of the engine where the turbine is located.

 

Anselm Franz of Junkers' engine division (Jumo for Junkers Motoren) addressed this problem with the introduction of the axial-flow compressor. Essentially this is a turbine in reverse. Air coming in the front of the engine is blown to the rear of the engine by a fan, where it is crushed against a set of non-rotating blades called stators. The process is nowhere near as powerful as the centrifugal compressor, so a number of these pairs of fans and stators are placed in series to get the needed compression. Even with all the added complexity, the resulting engine is much smaller. Jumo was assigned the next engine number, 4, and the result was the Jumo 004 engine. This was the first jet engine to see service, when it powered the Messerschmitt Me 262 in 1944. The Messerschmitt 262 was by far the fastest airplane of WW II. Mass production started in 1944, too late for a decisive impact.

 

After the end of World War II, the German Me 262 aircraft were extensively studied by the victorious allies, and led to early Soviet and US jet fighters.

 

British engines also were licensed widely in the US. American designs wouldn't come fully into their own until the 1960s. Their most famous design, the Nene, would also power the USSR's jet aircraft after a technology exchange.

 

There are a number of types of jet engines:

 

Turbojet


Whittle's and von Ohain's designs are now classified as turbojets, mostly to distinguish them from some of the types outlined below. Generally turbojets are arranged around a central shaft running the length of the engine, with the compressor and turbine connected to the shaft at either end. In the middle is a combustion area, typically in the form of a number of individual "flame cans" which are used to stabilize the combustion.

 

Like all heat engines, the efficiency of a jet engine is strongly dependent upon the temperature of the exhaust gas -- a higher temperature means more energy from the fuel. As shown by the ideal gas law, temperature and pressure in a gas are inversely related. A simplification is to compare the pressure of gas taken in to when it is burned, the so-called compression ratio. Early jet engines had compression ratios as low as 5 to 1, compared to an otto cycle engine at anywhere from 6 to 1, to 9 to 1. The limiting factor is the temperature at the front of the turbine; increasing the compression ratio means that there is considerably more fuel/air mixture (the charge) burning in the flame cans, and a higher temperature. If the temperature in the engine gets too high, it can melt or burn the materials used to build the engine. This is primarily a problem when taking off; as the aircraft climbs the ambient pressure drops and the compressor can be run at higher ratios.

 

German engines had serious problems in this regard. Their early engines averaged only 10 hours of operation before failing--often with chunks of metal flying out the back of the engine when the turbine overheated. British engines tended to fair much better due to better metals. For a time some US jet engines included the ability to inject water onto the engine to cool the exhaust in these cases. This was particularly notable because of the huge amounts of smoke that would pour out of the engine when it was turned on.

 

Today this problem is no longer a concern. Better materials have increased the critical temperature, and automatic throttle controls have made it nearly impossible to overheat the engine. However, the most effective solution has been to bleed off some of the air from the compressor, run it down the shaft, and blow it through the middle of hollow turbine blades. This made the blades quite expensive to build. The quality of these bleed systems has continued to improve to the point where the latest Rolls-Royce Trent designs operate at a compression ratio of 44:1, considerably better than piston engines.

 

The compressor uses up about 60 to 65% of all of the power generated by a jet engine. This explains why they aren't used in cars: the engine would be burning the fuel needed for a race while sitting still at a red light. Every bit of efficiency in running the compressor is needed, so one common design technique is to use more than one turbine to drive the compressors at various speeds. Most such designs that use two stages are are known as "two spool" engines. A few have used three stages.

 

Given that 60% of the engine's power is being used for driving the compressor, one option for better efficiency is to do less compression - that is, make a smaller engine. This seems self-defeating, but it's not the case. If the engine uses some of that energy not to compress the air, but to push it, it can generate thrust without compression.

 

Turboprop or turboshaft


By adding another turbine stage to the engine, all of the jet exhaust can be used for rotary force rather than jet thrust. Coupling this second (or third) turbine to a propeller makes for a very efficient engine due to the inherent efficiency of a propeller at low speeds. This is called a turboprop, and can be found on many smaller commuter planes, cargo planes, and helicopters (where it is often known as a turboshaft). Propellers lose efficiency as aircraft speed increases, which is why they are not used on higher-speed aircraft.

 

Similar engines are used for many applications. Connected to a generator, they make excellent light-weight and very reliable power sources. In fact, almost all large aircraft include a much smaller engine to provide power while parked at the airport, called an auxiliary power unit. The small pop-up doors often visible near the tail of an airliner are the air vents for these engines..

 

Larger versions of the same design are found in many industrial applications, peak-demand power generation stations, and military ships.

 

Turbofan


If the propeller is better at low speeds, and the turbojet is better at high speeds, it might be imagined that at some speed range in the middle a mixture of the two is best. Such an engine is the turbofan (originally termed bypass turbojet by the inventors at Rolls Royce). Turbofans essentially increase the size of the first-stage compressor to the point where they act as a ducted propeller (or fan) blowing air past the "core" of the engine.

 

This type of engine runs best from about 250mph to 650mph, which is why the turbofan is by far the most used type of engine for aviation use.

 

The bypass ratio (the ratio of bypassed air mass to combustor air mass) is an important parameter for turbofans. Early turbofans (and most modern jet fighter engines) are low-bypass turbofans with bypass ratios less than 1. However, the "large mouthed" engines on almost all modern civilian jet aircraft are high-bypass turbofans which generally have bypass ratios of 3 or more.

 

Turbofans (especially high bypass engines) are fairly quiet. The noise of a jet engine is strongly related to the temperature of the air coming out the back. In the turbofan this hot air is mixed with the cold air bypassing the engine, so the result is a much lower temperature. Jet aircraft are often considered loud, but a conventional piston engine delivering the same tens of thousands of horsepower would be much louder.

 

Propfan


The reason propeller engines lose efficiency at high speed is the same reason that airplanes find it difficult to fly at supersonic speeds: an effect known as wave drag significantly increases drag just below the speed of sound, and led to the concept of the sound barrier.

 

In the case of a propeller this effect can happen any time the prop is spun fast enough that the tips of the prop start travelling near the speed of sound, even if the plane is sitting still. This can be controlled to a large degree by adding more blades to the prop, using up more power at a lower speed. This is why most WWII fighters started with two-blade props and were using five-blade designs by the end of the war. As their engines increased in power, they couldn't just spin the prop faster. However this solution does not help as the plane itself accelerates; at some point the forward speed of the plane combined with the rotational speed of the propeller will once again result in wave drag problems.

 

A method of decreasing wave drag was discovered by German researchers in WWII: sweeping the wing backwards. Today almost all aircraft designed to fly much above 450 mph (700 km/h) use a swept wing. In the 1970s NASA started researching propellers with similar sweep. Since the inside of the prop is turning more slowly than the outside, the blade became progressively more swept toward the outside, leading to a curved shape.

 

Propfans are turbofans without ducts. The ducting of the normal turbofan has the side effect of containing the sonic boom of the fan inside the engine where it is largely muted. Such is not the case on a propfan. Propfans were at one time thought to be the next logical step in engine development for subsonic aircraft, but their very high noise levels made them unattractive, and work on them has since stopped.

 

Propfans are also known as ultra high by-pass (UHB) engines.

 

Ramjet


At the other end of the scale from the increasing complexity of the fans is the ramjet. When air enters a jet engine its speed decreases and its pressure increases, called the ram compression effect. At high speeds this process can be fairly effective, and can compress enough oxygen to efficiently burn the fuel for the engine all on its own. Typically the speed needed to make this process work effectively is above 600 mph (1000 km/h), and doesn't outperform traditional designs until supersonic.

 

Ramjets are built to utilize this compression effect through a careful inlet design. Beyond that the engine is largely nothing more than a well-designed tube. A ramjet thus contains no (major) moving parts and is particularly useful in applications requiring a small and simple engine for high speed use. On the downside they need to be flying at high speed to start with, making them less than useful for general tasks. They have found use almost exclusively in missiles, where they are boosted to operating speeds by a rocket motor, or by being attached to another aircraft (typically a fighter). Today ramjets have been generally replaced by small turbofans or rockets.

 

Pulsejet


The pulsejet was invented in the first half of the 20th century and was the power plant that propelled the world's first cruise missile, the German V1 flying bomb.

 

Like most jet engines, the pulse jet engine is very simple in design -- consisting primarily of a long tube into which air enters and is mixed with fuel to create a combustible (stoichiometric) mixture. Where the pulsejet differs from other engines such as the Turbojet or Ramjet is that the combustion inside the engine is not continuous but occurs in the form of repeated explosions, hence the name "pulsejet".

 

There are two basic types of pulsejets. The first is known as a valved or traditional pulsejet and it has a set of one-way valves through which the incoming air passes. When the air/fuel is ignited, these valves slam shut which means that the hot gases can only leave through the engine's tailpipe, thus creating forward thrust.

 

The second type of pulsejet is the valveless pulsejet. These engines have no valves; indeed they have no moving parts at all and in that respect they are even simpler than a ramjet. With these engines, the intake and exhaust pipes usually both face the same direction. This often necessitates bending the engine in half (the Lockwood design is made this way) or placing a 180 degree bend in the intake tube. This is necessary because when the air/fuel mixture inside the engine ignites, hot gases will rush out both the intake tube and the exhaust tube, there being no valves to stop them. If both tubes weren't facing in the same direction, little or no thrust would be generated because the reactions from the intake and exhaust tubes would cancel each other out.

 

The advantage of the valveless pulsejet is simple and obvious, there are no moving parts to wear out so they are far more reliable and a lot simpler to build.

 

However, despite this advantage, pulsejets are seldom considered to be practical power plant due to their high fuel consumption, noise, and significant vibration levels. Today, they survive as a powerplant for model aeroplanes.

 

Scramjet


When the air inside a ramjet exceeds the speed of sound (meaning an aircraft speed of around Mach 5+) combustion fails to occur properly. This is overcome in a scramjet (supersonic combustion ramjet). Scramjets are a new concept still in the research stages. Usually, the inlet is much wider (typically the entire underside of the craft) so the compression is less and the air remains at supersonic speeds. Some designs use reactive chemicals or gases other than standard jet fuel. Normally, the design of the jet is much more complex. Like a ramjet the scramjet must already be moving extremely fast before it will start working, but theoretically, speeds in excess of Mach 20 are possible.

 

Turbo-rocket


Rocket engines need to carry both their fuel and "air", which makes them carry around much more weight than a jet for the same amount of fuel burned. The turborocket is an attempt to reduce the amount of oxygen (or to be exact, oxidizer) that needs to be carried by extracting some from the air the rocket flies through. Typical designs use a compressor similar to that of a traditional jet engine, but mix that along with additional oxidizer from the tanks. The compressor is turned off when reaching altitudes where there is no longer enough air to make this practical. Note that there are several other systems for extracting oxider from the air as well, designs known as LACE.

 

Air intake design


For subsonic aircraft, the air intake to a jet engine presents no special difficulties, and consists essentially of an opening which is designed to minimise drag, as with any other aircraft component. However, the air reaching the compressor of a normal (not scramjet) jet engine must be travelling below the speed of sound, even for supersonic craft. Special intakes are used to ensure this. The earliest types of supersonic aircraft featured a central shock cone used to form a shock wave ahead of the air intake. Being behind the shockwave, the air was travelling subsonically. This type of shock cone is clearly seen on the English Electric Lightning and MiG-21 aircraft, for example. The same approach can be used for air intakes mounted at the side of the fuselage, where a half cone serves the same purpose with a semicircular air intake, as seen on the F-104 Starfighter and BAC TSR-2. A more sophisticated approach is to angle the intake so that one of its edges forms a leading blade. A shockwave will form at this blade, and the air ingested by the engine will be behind the shockwave and hence subsonic. The Century series of US jets featured a number of variations on this approach, usually with the leading blade at the outer vertical edge of the intake which was then angled back inwards towards the fuselage. Typical examples include the Republic F-105 Thunderchief and F-4 Phantom. Later this evolved so that the leading edge was at the top horizontal edge rather than the outer vertical edge, with a pronounced angle downwards and rearwards. This approach simplified the construction of the intakes and permitted the use of variable ramps to control the airflow into the engine. Most designs since the early 1960s now feature this style of intake, for example the F-14 Tomcat, Panavia Tornado and Concorde.