Renato Vesco, Feuerball and Kugelblitz
One individual - only partially aware that he was doing anything of the sort - turned the press reports of 'foo fighters' into armed, controlled, high-performance flying discs. His name was Renato Vesco, an Italian who wrote three books in his own language, only one of which was translated into English. He also had an article published in the August 1969 edition of the US men's magazine Argosy, which was probably little more than a hack writer's rendering of material in the book. The article was titled Aerospace expert claims Flying Saucers are Canada's Secret Weapon, and in the introduction to the piece there first appears the statement which lies at the heart of the authority which Vesco has come to command over the years. It said
"Renato Vesco is a fully licensed aircraft engineer and a specialist in aerospace and ramjet developments. He attended the University of Rome and, before WWII, studied at the German Institute for Aerial Development. During the war, Vesco worked with the Germans at the Fiat Lake Garda secret installations in Italy. In the 1960s, he worked for the Italian Air Ministry of Defense as an undercover technical agent, investigating the UFO mystery." 
It is in the context of this statement that many writers have first considered the material set out by Vesco in the first of his three books, often without having actually seen the book itself. Here are some key selections of what Vesco says about the supposed Feuerball and Kugelblitz in the paperback version of 'Intercept UFO'.
"Another center, run by Speer and the S.S. Technical General Staff, had adopted the idea of employing "proximity radio interference" on the very much more delicate and hence more vulnerable electronic apparatuses of the American night fighters . . . Thus a highly original flying machine was born; it was circular and armored, more or less resembling the shell of a tortoise, and was powered by a special turbojet engine, also flat and circular, whose principles of operation recalled the well-known aeolipile of Hero, which generated a great halo of luminous flames. Hence it was named Feuerball (Fireball). It was unarmed and pilotless. 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 radio gear.
The fiery halo around its perimeter - caused by a very rich fuel mixture - and the chemical additives that interrupted the flow of electricity by overionising the atmosphere in the vicinity of the plane, generally around the wing tips or tail surfaces, subjected the H2S radar on the plane to the action of powerful electrostatic fields and electromagnetic impulses (the latter generated by large klystron radio tubes protected with special antishock and antiheat armor). Since a metal arc carrying an oscillating current of the proper frequency - equal, that is, to the frequency used by the radar station - can cancel the blips (return signals from the target), the Feuerball was almost undetectable by the most powerful American radar of the time, despite its nighttime visibility.
In addition, the builders of the device hoped - and their hopes were fulfilled - that when the Allied flyers, not knowing their nature or purpose, noticed that the fiery balls were apparently harmless, they would not fire on these enormous-looking (because of their large halos of fire) "inoffensive" devices for fear of being caught in some gigantic explosion. More than one, in fact, as they fearfully watched those huge lights close in, the American pilots thought that some German technician on the ground was perhaps getting ready to push a button and cause the Foo Fighter to explode.
Project Feuerball was first constructed at the aeronautical establishment at Wiener Neustadt, with the help of the Fluggfunk Forschungsanstalt of Oberpfaddenhoffen (F.F.O.) in so far as radio control of the missile was concerned (but was it really a missile?) One person who saw the first short test flights of the device, without its electrical gear, says that "during the day it looked like a shining disc spinning on its axis and during the night it looked like a burning globe".
Hermann Göring inspected the progress of the work a number of times, for he hoped, as in fact happened, that the mechanical principle could also later be used to produce an offensive weapon capable of revolutionising the whole field of aerial warfare.
When the Russians began to press on toward Austria, the construction of the first Fireballs was apparently continued by a number of underground plants in the Schwarzwald that were run by the Zeppelin Werke. The klystron tubes were supplied by the section of the Forschungsanstalt der Deutschen Reichpost (F.D.R.P.) of Aach bei Radolfzell on Lake Constance, and later also by the F.D.R.P. section of Gehlberg, whose products, however, were not as perfect as those delivered by the F.D.R.P., a fact that caused a number of Fireballs to be used simultaneously in formation." 
Expressly identifying the reports of aerial lights known in some parts of the US Air Force as 'foo fighters' as being evidence of the amazing, hitherto and hereafter unheard of secret weapon he called the Feuerball, Vesco sets out some more technical details
"The Foo Fighters did contain a strong explosive charge to destroy them in flight in case serious damage to the automatic guidance system made it impossible for the operators to control it. It seems, however, that during the time they were last seen, at least one American flyer opened fire on a Foo Fighter from a safe distance without succeeding in shooting it down, although he had it well within his sights. A convincing detail, this, especially in view of the fact that under the armored covering of the Foo Fighters there was a thin sheet of aluminum attached to it (but electrically insulated) that acted as a switch. When a bullet pierced the outer covering, contact between the two sheets was established and the consequent closing of the circuit that operated the maximum acceleration device of the craft (generally in a vertical direction) caused the Foo Fighter to fly off, taking it out of the range of further enemy fire." 
Now and then, Vesco includes references which support his claims, but he never does so with regard to the Feuerball. Let's analyse what he is actually saying here, and what sense (if any) it makes, because, thanks to Vesco, and Vesco alone, we know that this device designed to achieve “proximity radio interference”
* was circular and armored, more or less resembling the shell of a tortoise
* was “enormous-looking”
* during the day it looked like a shining disc spinning on its axis and during the night it looked like a burning globe
* was powered by a special turbojet engine, also flat and circular, which generated a great halo of luminous flames around its perimeter.
* was unarmed and pilotless.
* was radio-controlled at the moment of take-off
* “automatically” followed enemy aircraft, attracted by their exhaust flames,
* approached close enough to the enemy aircraft, without collision, to wreck their radio gear.
* carried large klystron radio tubes protected with special antishock and anti-heat armor
* could be used simultaneously in formation with other Feuerballs
* contained a strong explosive charge to destroy it in flight in case serious damage to the automatic guidance system made it impossible for the operators to control it
* had under its armored covering a thin sheet of aluminum attached to it (but electrically insulated) that acted as a switch. When a bullet pierced the outer covering, contact between the two sheets was established and the consequent closing of the circuit that operated the maximum acceleration device of the craft (generally in a vertical direction) caused it to fly off, taking it out of the range of further enemy fire
* had chemical additives (in its fuel?) that interrupted the flow of electricity by overionising the atmosphere in the vicinity of the plane, generally around the wing tips or tail surfaces, subjecting the H2S radar on the plane to the action of powerful electrostatic fields and electromagnetic impulses, making it almost undetectable by the most powerful American radar of the time
I don’t want to labour the point here - we could go on for a long time making fun of this nonsense - but this is not a description of anything real. We aren’t told what its actual size was. We know that it had no wings, but that it did carry a powerful engine, two layers of metal to protect it and trigger its escape when hit, liquid fuel (lots of it, presumably), large klystron radio tubes protected with special antishock and antiheat armor, a strong explosive charge, radio control equipment, and the absolutely mysterious devices which interfered with radio transmissions and made it nearly invisible to radar. It must, therefore, have been a dense, heavy, tortoise-shaped package. We can only speculate how it developed the lift not only to reach heights of 10,000 to 25,000 feet (the range within which bombing raids usually took place), at speeds in excess of 200mph just to follow the bombers, and faster to accelerate away from them.
It seems to have been radio-controlled at launch (however launch was achieved, let alone landing - were these devices meant to be landed and reused?), and also, because otherwise why would it contain “a strong explosive charge to destroy it in flight in case serious damage to the automatic guidance system made it impossible for the operators to control it” during flight. Between 2 and 5 miles up. In the dark. Following aircraft travelling at 200mph or so, apparently over considerable distances. We are again left to speculate how the operators knew what they were controlling, what was happening to their particular Feuerball at any given moment, or what form of radio control could, in 1943 - 1945, work that accurately over that distance. Vesco does not address the question of how direction or speed of flight (if the motion of an armoured wingless tortoise can be accurately described as flight) was controlled or determined.
Other questions arise. How did the Feuerball distinguish an enemy aircraft from a friendly one? How did it stop following the exhaust flames? Where did it go when it stopped? Why, when it was travelling laterally behind the engines of an enemy aircraft, attracted by its exhaust flames, did it suddenly depart “generally in a vertical direction” when hit? Which “chemical additives interrupted the flow of electricity by overionising the atmosphere in the vicinity of the plane”? Just how did that work? How did it wreck the radio gear of enemy aircraft? Where? When? And how, for pity’s sake, could these devices ever have flown “in formation with other Feuerballs”?
Those of you who actually know about aeronautical engineering - as Vesco is supposed to have done - will be able to phrase these questions far better than I. Perhaps Vesco himself would like to put his mind to answering them: I certainly can’t. At present, though I’m happy to be persuaded otherwise, and to publish any hard evidence to that effect, my view is that the Feuerball - which even Lusar had never heard of - is a fantasy. How this fantasy came to be published, I’m really not sure. But I wondered for a year or two how he had come to construct these pseudo-technical descriptions, which originate absolutely and only with Vesco. Eventually I realised that what he had done was to look at the few reports of 'foo fighters' that he quotes - from the 'American Legion Magazine' and 'Amazing Stories', because he didn't have the benefit of the excellent investigative work done by Roberts or Lindell - and to build round those descriptions of the behaviour of those lights, speculative technical explanations which he considered matched their reported performance. The only reasonable conclusion available to me is that Vesco - or one of his obviously careless editors or publishers - put these 'technical' descriptions in his book knowing that they had no factual basis. Passing time, the laziness of later authors, and the inexplicable readiness to believe in the wonders of Nazi intellect has gradually turned these dumb speculations into accepted facts.
Unless strong and reliable evidence appears to the contrary, I think we can dismiss the Feuerball - and its even less defined relative the Kugelblitz, to which Vesco mistakenly gave the name of a Flak Panzer in development early in 1945 - as objects that never had any physical reality, and were probably never even designed. I think that we could, quite reasonably do this on technical and scientific grounds alone.
Yet Vesco continues to be highly influential, regarded as the leading authority of the Axis on secret technological developments in aeronautics. And, given his background, his experience and his authority, as summarised in the article in 'Argosy', what could be wrong with that?
Had readers looked as far as the cover of the book from which these claims came, they would have found a substantially different version of Vesco's authority to that given in 'Argosy'. This didn't say that he had, before WWII, "studied at the German Institute for Aerial Development." Or that, during the war, he had "worked with the Germans at the Fiat Lake Garda secret installations in Italy." Nor did it claim that "In the 1960s, he worked for the Italian Air Ministry of Defense as an undercover technical agent, investigating the UFO mystery." Instead, it said that
"Renato Vesco was born in Arona, Italy, in 1924. A licensed pilot, in 1944 he commanded the technical section of the Italian Air Force. In 1946-47 he served in the Reparto Tecnico Caccia. Mr Vesco has been a senior member of the Italian Association of Aerotechnics since 1943, and is a student of aeronautical problems, particularly in the field of jet propulsion. He is a contributor to various aeronautical publications." 
There is clearly something very wrong here. Born in 1924, Vesco would have been 14 or 15 when WWII broke out. Surely, by that age, he had not attended the University of Rome and studied at the German Institute for Aerial Development? If he worked with the Germans at the Fiat Lake Garda secret installations in Italy, why didn't other authorities mention him?
Would he really have "commanded the technical section of the Italian Air Force" at the age of 19 or 20, and "been a senior member of the Italian Association of Aerotechnics" at the age of 18 or 19? Surely, if he really were that remarkable, that important, his name would have appeared in the index or references of at least one of the countless books about the war that I've examined? Yet it doesn't. Who was Vesco, and what did he really know about wartime German aircraft? Where did his material come from?"
Thanks to the highly-respected Italian researchers Maurizio Verga and Eduardo Russo, we now have clear answers to these questions: they both know Vesco personally. As Verga says
"Vesco exists, definitely! . . He is an old man now, born in 1924. What's written by him by people like Al Pinto on the Internet and BBSs, as well as by Harbinson, is complete rubbish. His introduction in the 1971 English translation of his first book is quite accurate, even though he was not commanding any "technical section" in the Italian Air Force . . He was an aeronautical engineer and he got an interest in flying saucers (always seen as a secret development of man-made aircraft) in the late 40's. He published several articles (about German secret weapons, flying saucers, aviation and other subjects) since the very early '50s, soon becoming a real skeptic against the then-common idea of ETH visits (he commented and explained some sightings due to atmospheric or conventional phenomena). The manuscript of his first book was ready in 1956, but he stopped publication because he was to go abroad for a long time, due to his job. When he was back in the '60s, after collecting a huge quantity of additional stuff, he had hundreds and hundreds of written pages, later to be turned into his three books. Vesco claims his sources are BIOS and CIOS reports dating between 1945 and 1947, plus other military and intelligence documents, mostly British. He told me "important persons" (I guess high-ranking officers from the Italian Air Force and other foreign Air Forces) contributed to his research with information and documents still classified. He promised not to make public their names, even though he says that most of them are surely dead. I know he borrowed the BIOS/CIOS reports he quoted in his books from some Italian AF officers, through the library or libraries of the IAF itself . . It is true he is the only aviation student who introduced the 'Feuerball' and 'Kugelblitz' devices, at least as far as I know. Please also note that 'Kugelblitz' was a name given to other German weapons, including a Flak Panzer.
Vesco thinks the Schriever & Co stories simple bullshits, while Vril and Haunebu pure science-fiction." 
The deceptive biographical information provided by Vesco’s various publishers has succeeded in misleading many later writers and researchers, and in providing support for the false claims of others. Like all too many of those involved in the world of Nazi UFOs, Vesco gave an impression of authority, and that authority was accepted without challenge.
It now appears that Vesco was a man with an interest in man-made UFOs, who was strongly opposed to the extra-terrestrial hypothesis (ETH), used to explain many early ‘flying saucer’ sightings. He provides, in the Feuerball and Kugelblitz accounts given in a book we now know was completed by 1956, what sounds like a convincing hypothesis for explaining away, without the involvement of spacemen and interplanetary travel, not only the 'foo fighter' reports of which he was aware, but also the very ‘physical’ sightings and photographs of the late ‘40s and early ‘50s. It is unfortunate that, in seeking to use his knowledge of aeronautical engineering to popularise what he apparently saw as a rational explanation for a body of irrational reports and interpretations, he only succeeded in co-founding the Nazi UFO mythos, a living and growing belief system which, for sheer irrationality and unpleasantness, came to far exceed anything from those innocent early days of ufology.