Silbervogel Sub-Orbital Intercontinental Bomber

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Silbervogel (“silver bird”) was a super-revolutionary design (actually more concept than a full-fledged design). It was decades (if not a hundred years) ahead of its time because even today’s technologies are not advanced enough to produce this weapon and make it operational.

Silbervogel was designed in the late 1930s by Eugen Sänger (Austrian aerospace engineer) and Irene Bredt (German engineer, mathematician and physicist) as rocket-powered sub-orbital intercontinental bomber. It was one of a number of designs considered for the Amerika Bomber project.

When Walter Dornberger attempted to create interest in military spaceplanes in the United States after World War II, he chose the more diplomatic term antipodal bomber when describing the Silbervogel project.

Although it was deemed impossible to produce as the just about all necessary technologies (propulsion system, navigation, protection from heat, etc.) simply did not exist (actually, were decades away), it still was an influential design.

Silbervogel was the first spaceplane design that incorporated liquid-fuel rocket technology, and the principle of the lifting body, foreshadowing future development of operational winged spacecraft such as the X-20 Dyna-Soar of the and the famous Space Shuttle (and its Soviet clone Buran).

The Silbervogel was intended to fly long distances in a series of short hops. The aircraft was to have begun its mission propelled along a 3 km long rail track by a large rocket-powered sled to about 800 km/h. Once airborne, it was to fire its own rocket engine and continue to climb to an altitude of 145 km, at which point it would be travelling at some 5,000 km/h.

It would then gradually descend into the stratosphere, where the increasing air density would generate lift against the flat underside of the aircraft, eventually causing it to “bounce” and gain altitude again, where this pattern would be repeated.

Because of aerodynamic drag, each bounce would be shallower than the preceding one, but it was still calculated that the Silbervogel would be able to cross the Atlantic, deliver a 4,000 kg [nuclear] bomb to the continental United States, and then continue its flight to a landing site somewhere in the Empire of Japan–held Pacific, a total journey of 19,000 to 24,000 km.

Postwar analysis of the Silbervogel design involving a mathematical control analysis unearthed a computational error and it turned out that the heat flow during the initial atmospheric re-entry would have been far higher than originally calculated by Sänger and Bredt.

Consequently, had the Silbervogel been constructed according to their flawed calculations the craft would have been destroyed during re-entry. The problem could have been solved by augmenting the heat shield, but this would have reduced the craft’s already small payload capacity (or would have required far more powerful rocket engines).

On 3 December 1941 Sänger sent his initial proposal for a suborbital glider to the Reichs Air Ministry (RLM) The 900-page proposal was regarded with disfavor at the RLM due to its size and complexity and was promptly rejected.

Professor Walter Gregorii had Sänger rework his report and a greatly reduced version was submitted to the RLM in September 1944. It was the first serious proposal for a vehicle which could carry a pilot and payload to the lower edge of space.

Two manned and one unmanned version were proposed: the Antipodenferngleiter (antipodal long-range glider) and the Interglobalferngleiter (intercontinental long-range glider).

Both were to be launched from a rocket-powered sled. The two manned versions were identical except in payload. The Antipodenferngleiter was to be launched at a very steep angle (which would shorten the range) and after dropping its bomb load on New York City was to land at a Japanese base in the Pacific.

However by that time RLM had much more pressing needs than the development of an intercontinental Amerika Bomber (which without a nuclear bomb was useless anyway). So the project was rejected again.

After the war ended, Sänger and Bredt worked for the French government and in 1949 founded the Fédération Astronautique. Whilst in France, Sänger was the subject of a botched attempt by Soviet agents to win him over.

Joseph Stalin had become intrigued by reports of the Silbervogel design and sent his son, Vasily, and scientist Grigori Tokaty to kidnap Sänger and Bredt and bring them to the USSR.

When this plan failed, a new design bureau was set up by Mstislav Vsevolodovich Keldysh in 1946 to research the idea. A new version powered by ramjets instead of a rocket engine was developed, usually known as the Keldysh bomber, but not produced. The design, however, formed the basis for a number of additional cruise missile designs right into the early 1960s, none of which were ever produced.

In the US, a similar project, the X-20 Dyna-Soar, was to be launched on a Titan II booster. As the manned space role moved to NASA and unmanned reconnaissance satellites were thought to be capable of all required missions, the United States Air Force gradually withdrew from manned space flight and Dyna-Soar was cancelled.

One lasting legacy of the Silverbird design is the “regenerative cooling—regenerative engine” design, in which fuel or oxidizer is run in tubes around the engine bell in order to both cool the bell and pressurize the fluid. Almost all modern rocket engines use this design today and some sources still refer to it as the Sänger-Bredt design.

 

Bizarre Nazi Weapons – The Mistel Flying Bomb

Mistel

Mistel (German for “mistletoe”), was the larger, unmanned component of a composite aircraft configuration (i.e. the actual flying bomb) developed and used by Luftwaffe during the later stages of World War II.

The composite comprised a small piloted control aircraft mounted above a large explosives-carrying drone and as a whole was referred to as the Huckepack (“Piggyback”), also known as the Beethoven-Gerät (“Beethoven Device”) and Vati und Sohn (“Daddy and Son”). However, in practice Mistel commonly refers to the whole composite configuration.

The piloted aircraft was a single-seat fighter (Bf-109 or FW-190); the unmanned drone actually used was Ju-88 medium bomber (other fighters and bombers were proposed but never deployed).

The bomber component (which was often a new aircraft rather than surplus) was fitted with a 1,800 kg warhead. The warhead was a cone-shaped charge fitted with a copper or aluminum liner that could penetrate up to seven meters of reinforced concrete.

Some 250 Mistels of various combinations were built during the war, but they were largely unsuccessful (dismal failure would be a better assessment). The biggest deficiency of Mistel was that (unlike successful Fritz X bomb or a Hs 293 missile that inspired the Mistel weapon) the former was an unguided weapon.

Consequently given formidable air defenses deployed by the Red Army and the Allied forces, it is no wonder that just about none of the Mistels hit their intended targets.

They were first flown in combat against the Allied invasion fleet during the Battle of Normandy in June of 1944, targeting the British-held harbor at Courseulles-sur-Mer.

While Mistel pilots claimed hits, none of these match Allied records; they may have been made against the hulk of the old French battleship Courbet, which had been included as a component of the Mulberry harbor at Arromanches and specially dressed up as a decoy by the Allies.

Serious blast and shrapnel damage from a near-miss was suffered by HMS Nith, a River-class frigate being used as a floating headquarters on June 24th. Nine men were killed and 26 wounded, and Nith was towed back to England for repairs.

As part of Operation Iron Hammer in late 1943 and early 1944, Mistels were selected to carry out key raids against Soviet weapons-manufacturing facilities—specifically, electricity-generating power stations around Moscow and Gorky.

Those plants were known to be poorly defended by the Soviets and irreplaceable. However, before the plan could be implemented, the Red Army had entered Germany, and it was decided to use the Mistels against their bridgehead at Küstrin instead.

On April 12th, 1945, Mistels attacked the bridges being built there, but the damage caused was negligible and delayed the Soviet forces for only a day or two. Subsequent Mistel attacks on other bridges being thrown across the Oder were similarly ineffective.

In other words, Luftwaffe would have probably been much better off using bombers as, well, piloted bombers. Or developing a radio-guided version of Mistel with a two-seat fighter (pilot and weapon operator) as the control/piggyback aircraft.

 

Me 163 Rocket Interceptor

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Me 163 Komet (“Comet”) was not the only one rocket interceptor ever built (the Soviet Union tested but never deployed a BI-1 aircraft that had essentially the same concept), but it was (thankfully) the only one to be mass-produced (~320 have been built) and operationally deployed.

It was also the only such aircraft that saw actual combat – with disastrous results for Luftwaffe – and the first piloted aircraft of any type to exceed 1000 km/h in level flight. German test pilot Heini Dittmar in early July 1944 reached 1,130 km/h (700 mph), an unofficial flight airspeed record unmatched by turbojet-powered aircraft for almost a decade.

Although it was produced by Messerschmitt, it was actually designed by Alexander Lippisch – a pioneer of aerodynamics who made important contributions to the understanding of tailless aircraft, delta wings (now all but standard on fighter- and fighter/bomber aircraft) and the ground effect.

The basic idea behind development and deployment of Me 163 was understandable. Luftwaffe needed an extremely fast interceptor (thus immune to both defensive bomber guns and escort fighters) that (unlike Me-262 turbojet fighter) could be mass-produced using widely available non-strategic materials (e.g. wood), use fuel other than petrol that was in dire shortage and (hopefully) could be flown by relatively inexperienced pilots.

Me-163 was fast indeed; however, it had a number of crucial deficiencies that made it a highly inefficient interceptor (an abject failure, actually). First, it was too fast for an easy and successful intercept – its tremendous speed and climb rate meant a target was reached and passed in a matter of seconds.

And its very short flight time (7.5 minutes of powered flight) meant that (1) the pilot had only one chance of hitting its target and (2) after the Komet ran out of fuel it was transformed into a glider highly vulnerable to both defensive guns and Allied escort fighters.

Although the Me 163 was a stable gun platform, it required excellent marksmanship to bring down an enemy bomber as at least four 30mm hits were typically needed to take down a B-17. The Komet was equipped with two 30 mm MK 108 autocannons which had a relatively low muzzle velocity of 540 meters per second, and were accurate only at short range (<600m), making it almost impossible to hit a slow moving bomber.

Its fuel – hydrogen peroxide – was highly flammable and thus presented a high risk of a spontaneous explosion (which killed several pilots). And its takeoff/landing gear – takeoff dolly jettisoned after the fighter got airborne and retractable landing skid – was prone to malfunction during both takeoff and landing and thus presented more danger to is pilots than enemy guns.

Consequently, it is no surprise that Mei163 was a dismal failure – it accounted for no more than eighteen destroyed Allied bombers with ten combat losses of the Komet. Many more aircraft were destroyed (and pilots killed) during takeoff or landing or in training accidents.

As part of their alliance, Germany provided the Japanese Empire with plans and an example of the Me 163.[64] One of the two submarines carrying Me 163 parts did not arrive in Japan, so at the time, the Japanese lacked all of the major parts and construction blueprints, including the turbopump which they could not make themselves, forcing them to reverse-engineer their own design from information obtained in the Me 163 Erection & Maintenance manual obtained from Germany. The Japanese J8M crashed on its first powered flight and was completely destroyed.

 

Ta-183 Next-Generation Jet Fighter

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The Focke-Wulf Ta 183 Huckebein was a design for a next-generation German jet-powered fighter aircraft intended as the successor to the Messerschmitt Me 262 and other day fighters in Luftwaffe service during World War II (hence the “next-generation”).

The name Huckebein is a reference to a trouble-making raven (Hans Huckebein der Unglücksrabe) from an illustrated story in 1867 by Wilhelm Busch (German humorist, poet, illustrator and painter).

Ta-183 was developed only to the extent of wind tunnel models when the war ended; however, it was ultimately a highly influential design which to a significant extent shaped the functionality of all modern fighter aircraft.

Whether its design influenced post-war Soviet (MiG-9), American (F-86 Sabre) and Swedish (Saab 29 Tunnan) and French (Ouragan), is highly questionable (although “all of the above” one way or the other did get hold of Ta 183 design documentation).

The only aircraft undoubtedly based on Ta 183 design was the Argentinian FMA IAe 33 Pulqui II (“Arrow”) designed by Kurt Tank (chief designer of Ta 183) who after the war emigrated to that Latin American country.

Ta 183 was a genuinely revolutionary designed because from the very beginning it was intended to carry both autocannons and guided air-to-air missiles (four Ruhrstahl X-4 wire-guided AAM).

The first operational fighter to carry AAM as a standard armament was the US Navy Grumman F-9 Cougar which entered service at the beginning of 1953 and was being armed with AIM-9 Sidewinder guided AAM from 1956.

Nowadays all fighter aircraft carry both guns and missiles; the only difference with Ta 183 being that the former are using a single multi-barrel cannon (e.g. M61 Vulcan) while the former was armed with four single-barrel 30mm MK-108 guns.

 

Nazi SAM Projects – Conclusions

Enzian2

As usual, five Luftwaffe SAM projects were four too many. And (again as usual), the Allies did not win the air war over Germany – the Nazis lost it. By the end of 1941 when blitzkrieg in Russia failed (not miserably, but still failed), they had everything to design, mass-produce, deploy and efficiently use a powerful anti-aircraft weapon that would have all but closed the German skies to Allied bombers by the end of 1942 at the latest.

That weapon (not surprisingly) was the Enzian Surface-to-Air Missile – an unmanned (drone) version of the Me-163 – a rocket-powered interceptor aircraft. Instead of continuing work on Me-163 (which ultimately was an abject failure), the Germans should have focused completely on developing the proper engines, guidance system and proximity fuse for the Enzian. Which was far easier to do for a subsonic than for a supersonic missile.

Enzian was perfectly suited for mass-production using widely available non-strategic materials, was highly mobile, had the most powerful warhead by far and had plenty of room for a sophisticated onboard guidance system, proximity fuse and the like. Obviously, all other SAM projects should have been abandoned immediately.

 

Wasserfall SAM

Peenemünde, Start Fla-Rakete "Wasserfall"

Wasserfall (‘Waterfall’) was essentially a SAM version of the V-2 (A4) missile, sharing the same general layout and shaping. Since the missile had to fly only to the altitudes of the attacking bombers, and needed a far smaller warhead to destroy these, it could be much smaller than the V-2, about one-fourth the size.

The final specifications of 2 November 1942 called for an interceptor missile with a top speed of Mach 2, able to hit airborne targets flying at up to 900 kph at 5 to 20 km altitude within a radius of 50 km. First versions were to use radio command guidance, to be followed by a self-guiding radar system in later models.

Unlike the V-2, Wasserfall was designed to stand ready for periods of up to a month and fire on command (and thus had to use a very different fuel). Guidance was to be a simple radio control manual command to line of sight (MCLOS) system for use against daytime targets.

The missile operator was mounted beside a chair on a framework that allowed the operator to tilt back to easily look at targets above him, rotating as needed to keep the target in sight.

Night-time use was considerably more complex because neither the target nor the missile would be easily visible. For this role a new system known as Rheinland was under development. Rheinland used a radar unit for tracking the target and a transponder in the missile for locating it in flight.

A simple analog computer guided the missile into the tracking radar beam as soon as possible after launch, using a radio direction finder and the transponder to locate it. Once it entered the radar beam the transponder responded to the radar signals and created a strong blip on the display. The operated then used the joystick to guide the missile so that the blips overlapped.

The original design had called for a 100 kilograms warhead, but because of accuracy concerns it was replaced with a much larger one of 306 kilograms, based on a liquid explosive.

The idea was to create a large blast area effect amidst the enemy bomber stream, which would conceivably bring down several airplanes for each missile deployed. For daytime use the operator would detonate the warhead by remote control.

An arguably revolutionary weapon, Wasserfall required considerable development work, which was not completed before the end of the war. After the first successful firing on March 8th, 1944, three trial launches were completed by the end of June 1944. A launch on January 8, 1945 was a failure, with the engine “fizzling” and launching the missile to only 7 km of altitude at subsonic speeds.

Thirty-five Wasserfall trial firings had been completed by the time Peenemünde was evacuated on February 17, 1945.

Wasserfall was arguably the closest design to the modern SAM systems. So it is no surprise that it became the most influential SAM developed by Nazi Germany. It was produced in the USA as the Hermes surface-to-surface missile, in the USSR as the R-101, and in France as the R.04. In Russia it also became the starting point for the (in)famous R-11/R-17 Scud surface-to-surface missile.

 

Rheintochter SAM

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Rheintochter was a German surface-to-air missile developed by Rheinmetall-Borsig. Its name comes from the mythical Rheintöchter (Rhine Maidens) of Richard Wagner’s (no surprises here) opera series Der Ring des Nibelungen.

The original (R1) version of the Rheintochter was a two-stage, solid-fuel missile that used a canard aerodynamic layout. The first stage boost consisted of a solid rocket charge which in only 0.6 seconds accelerated the missile to 300 m/s. The sustainer (second-stage) engine was located ahead of the warhead (rather than behind, as is more usual).

When the missile was within 20m range of its target, an acoustic proximity fuse triggered the 150 kg HE warhead. Six flares on the second stage were used by the operator to visually orient and guide the path of the missile.

Several variants of the R-1 version of the missile were built between August 1943 and January 1944. Three were launched, achieving 6 km altitude and 10 to 12 km range. These tests did not please the Ministry of Aviation, who needed a rocket that could reach an altitude of 10 to 12 km.

The R2 version was supposed to remedy this shortcoming, but failed to do so. Consequently, Rheinmetall-Borsig had to develop the R3 version which now had a liquid-fuel second stage which finally reached the necessary altitude. Work had begun in May 1944, and six launches of the prototype were made in January 1945.

However the missile never reached the stage of state trials testing. Peenemuende was abandoned on 20 February 1945, by which time only 15 R-3’s had been completed. The solid rocket motor for the R-3R had reached the stage of stand tests on 6 February 1945, but further work was cancelled.

No fewer than five different guidance systems (optical and radio) were developed for the Rheintochter, but none of them was ever tested in flight.

After the war, the Rheintochter became the basis for SE.4300 – French surface-to-air missile project (canceled in 1950).