"Silverbird" Orbital Bomber


 

In June 1935 and February 1936, Dr. Eugen Sänger published articles in the Austrian aviation publication Flug on rocket-powered aircraft.

This led to his being asked by the German High Command to build a secret aerospace research institute in Trauen to research and build his "Silverbird", a manned, winged vehicle that could reach orbit.

Dr. Sänger had been working on this concept for several years, and in fact he had began developing liquid-fuel rocket engines.

From 1930 to 1935, he  perfected (through countless static tests) a 'regeneratively cooled' liquid-fueled rocket engine that was cooled by its own fuel, which circulated around the combustion chamber.

This engine produced an astounding 3048 meters/second (10000 feet/second) exhaust velocity, as compared to the later V-2 rocket's 2000 meters/second (6560 feet/second). Dr. Sänger, along with his staff, continued work at Trauen on the "Silverbird" under the Amerika Bomber program.

The Sänger Amerika Bomber (or Orbital Bomber, Antipodal Bomber or Atmosphere Skipper) was designed for supersonic, stratospheric flight. The fuselage was flattened, which helped create lift and the wings were short and wedge shaped. There was a horizontal tail surface located at the extreme aft end of the fuselage, which had a small fin on each end. The fuel was carried in two large tanks, one on each side of the fuselage, running from the wings aft. Oxygen tanks were located one on each side of the fuselage, located forward of the wings. There was a huge rocket engine of 100 tons thrust mounted in the fuselage rear, and was flanked by two auxiliary rocket engines. The pilot sat in a pressurized cockpit in the forward fuselage, and a tricycle undercarriage was fitted for a gliding landing. A central bomb bay held one 3629 kg (8000 lb) free-falling bomb, and no defensive armament was fitted. The empty weight was to be approximately 9979 kg (22000 lbs).

An interesting flight profile was envisioned for the "Silverbird". It was to be propelled down a 3 km (1.9 mile) long monorail track by a rocket-powered sled that developed a 600 ton thrust for 11 seconds.

 



After taking off at a 30 degree angle and reaching an altitude of 1.5 km (5100'), a speed of 1850 km/h (1149 mph) would be reached.

At this point, the main rocket engine would be fired for 8 minutes and burn 90 tons of fuel to propel the "Silverbird" to a maximum speed of 22100 km/h (13724 mph) and an altitude of over 145 km (90 miles), although some sources list the maximum altitude reached as 280 km (174 miles).

As the aircraft accelerated and descended under the pull of gravity, it would then hit the denser air at about 40 km (25 miles) and 'skip' back up as a stone does when skipped along water. This also had the added benefit of cooling the aircraft after the intense frictional heating encountered when the denser air was reached. The skips would gradually be decreased until the aircraft would glide back to a normal landing using its conventional tricycle landing gear, after covering approximately 23500 km (14594 miles).

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The final test facilities for full-scale rocket engine tests were being built when Russia was invaded in June 1941. All futuristic programs were canceled due to the need to concentrate on proven designs. Dr. Sänger went on to work on ramjet designs for the DFS (German Research Institute for Gliding), and helped to design the Skoda-Kauba Sk P.14. Although the Luftwaffe did its best to stop Dr. Sänger from publishing his research results, a few
copies went unaccounted for and made their way to other countries.


Whether the ‘Amerika Bomber’ would have worked will never be known; the concept was way too far ahead of available technology to have had much chance of success, particularly in terms of avionics. Indeed, post-war analysis of the Silverbird design uncovered a mistake in the calculation of the effect of aerodynamic heating during re-entry - in fact had the Silverbird design ever made it into orbit it would almost certainly had burned up during re-entry. Furthermore, Germany would certainly have needed to develop an atomic bomb to make the attack worthwhile and, even if he survived the very high ‘G’ forces on take-off and the re-entry, the pilot would certainly be on a one-way mission, so the ‘Amerika Bomber’ was in reality a highly-advanced kamikaze vehicle. Nevertheless, when WW2 ended, both the Russians and the Americans studied Sänger’s research with great interest.

 

After the war, he was asked to work (along with mathematician Irene Bredt) for the French Air Ministry, where in a bizarre plot, he was almost kidnapped by Stalin, who recognized the value of the Amerika Bomber.

 



Sänger "Amerika" Orbital Bomber

 

Specific Features: One of the most "out there" aircraft conceived in a wide field of really crazy planes that often got really far in the design process, Sänger's "Amerika Bomber” was intended to be capable of rapidly deploying to attack any target anywhere in the world. The aircraft was revolutionary on many fronts, from its incredible (and likely terminal) speed to its bizarre launch method, Sänger was willing to "go there". His sort of fantastical approach to science was extremely popular with engineers and scientists in Germany, sometimes producing amazing technology; other times wasting incredible amounts of resources in otherwise obvious pipedreams.

 

The Amerika Bomber, had it ever passed the prototyping stage, would have been propelled into the air by a massive 600-ton thrust liquid fuel rocket. Not content to simply shoot stuff into the air, Sänger wanted to use this massive booster to shoot a rocket train into the air. The Amerika Bomber was to be mounted on a monorail dolly that also mounted the booster unit. The dolly would have shot down a three kilometer long angled rail in a mere 11 seconds and lifted the Amerika Bomber into the sky roughly a mile. At this point the aircraft's internal rocket thruster would have activated and lifted the plane to a low-orbit altitude of 145 kilometers and a speed of 22,100kph. The plane could have theoretically reached any location on the planet in under an hour and dropped a single 8,000lb bomb. With Germany's actual innovations in precision and wire-guided bombs this means individual buildings in major cities around the world could have been targeted by a massive conventional bomb. Other options include dropping in German storm troops, crazy battle robots, or possibly thousands of spiders.

 

After deploying its payload the bomber would have glided in to land at an airfield in Germany. It had only a single pilot sitting in a small pressurized cockpit at the front of the fuselage. Other than its payload the Amerika Bomber carried no weapons, relying on its speed and altitude for protection. It would have been obviously vulnerable as it glided in for landing, a flaw that marked many of Germany's real and imagined high-tech aircraft.

 

History: Hopes for the Amerika Bomber faded around the time Germany invaded the Soviet Union, which was probably to the advantage of the Germans as the whole thing was ridiculous. The air speed of the Amerika Bomber would have likely caused the plane to simply explode from friction before it even came close to reaching its top speed. The current air speed record from a powered aircraft is held by NASA's X-15 at 7,277kph; less than a third of the proposed top speed of the Amerika Bomber. NASA barely kept their plane from burning up, so there's virtually no chance that Sänger would have leapt a much higher hurdle, decades earlier. The pilot would have blacked out and died if he was lucky, or been liquefied or immolated if he was less fortunate. If Sänger had somehow overcome these problems then he still had the whole "giant length of elevated track and rail car" issue as American and British bombers marauded with virtual impunity across most of Europe. After the cancellation of the project, Sänger went on to work with other developers on more feasible ramjet interceptor projects. All that remains of the Amerika Bomber are some models, designs, and an engine.

 

 

 

Mystery 1945 German Hypersonic Bomber Prototype?


 



Sänger ramjet fighter concept from 1943 DFS report "Über ein Loreneintreib für Strahljäger" reproduced in 1947 NACA report TM 1106

In the late 1930s, Eugen Sänger, one of Germany's top theoreticians on hypersonic dynamics and ramjets, and his wife, mathematician Irene Bredt, had begun developing a suborbital rocket bomber, "RaBo"  (sometimes called the "Antipodal Bomber") that would be capable of attacking targets at intercontinental ranges.  Incorporating highly advanced concepts, including swept, wedge-shaped supersonic airfoils, a flat, heat-dissipating fuselage undersurface that anticipated the Space Shuttle's by thirty years, and rocket engines of extraordinary thrust, the RaBo concept would have taken many years to develop -- precious time that was running out for Nazi Germany.  In 1944, Sänger and Bredt were moved to a fantastic, isolated laboratory complex in the mountains near Lofer, Austria, where a number of bizarre research projects were underway, including impractical devices such as the infamous "sound cannon" and "wind cannon" and an electromagnetic railgun. 

Sänger's main known project centered on development of a high-speed, ramjet powered manned bomber interceptor that resembled a stubby missile.

 

Some sources also indicate that work on the Raketen Bomber, which had been suspended around 1942, was revived, and plans for a dedicated "Amerika Bomber" version, specifically intended to drop a 10,000 kg projectile on New York City, were put forward.  Sänger produced calculations concerning the enormous energy liberated when the ten ton projectile impacted in lower Manhattan at meteoric speeds.  This project paralleled in some respects the equally impressive Peenemünde concept for a two-stage version of the V-2, the A-9/10, that was also intended to strike New York and other northeast US cities

 

 

The Sänger-Bredt RaBo and its postwar Soviet derivative  both used a long rocket sled to propel the vehicle to its takeoff speed of several hundred mph.  After launch, an onboard engine of some 200,000 lbs thrust would propel the craft into a ballistic trajectory that peaked at altitudes of several hundred miles.  The German version was intended to be able to reach friendly territory after making its strike -- or possibly ditch near a U-boat.

The Soviet version had ramjets to provide ascent boost and possibly return-to-base cruise capability after velocity decayed into the supersonic range. 



Most sources indicate that nothing much came of the Amerika Bomber project at Lofer, but this is clearly not the case.  The Soviets recovered copies of Sänger's RaBo reports and were so fascinated with the concept (particularly Stalin, who seems to have been riveted by its implications) that they dedicated a great deal of effort to designing an updated RaBo equipped with huge ramjet engines for boost and cruise propulsion.  Stalin's son Vasili and rocket expert Grigoriy Tokaty-Tokayev were detailed to follow Sänger to Paris, where he had moved after the war, in a failed attempt to recruit or kidnap him in 1947.  The RaBo influenced Soviet manned and unmanned rocket work for years after the war.

 

It influenced US work too, leading directly to the Walter Dornberger-sponsored Bell "BoMi" (Bomber Missile) project of the early 1950s, and ultimately the USAF/Boeing X-20 Dyna Soar hypersonic glider program that laid the technical groundwork for the Space Shuttle.

 

No reference source on the Sänger-Bredt project indicates that any RaBo hardware was built at Lofer.  But a 1947 US technical intelligence manual on the Lofer base contains this fascinating, maddeningly blurry photograph (below) of what appears to be the incomplete nose and forward fuselage of a very unconventional aircraft.  The caption reads simply, "A futuristic airplane in a plant near Lofer.  It was never flown." There are no references to this aircraft in the text of the report.

 

The fuselage appears to have a flat upper and lower surface, and there appears to be a cockpit area at the right end of the structure.  The general shape and size agree with extant RaBo illustrations.  Was this a full-scale wooden mockup of the hypersonic bomber?  If so, there is little wonder that the Soviets were so impressed with the design.  But it raises questions about the lack of documentation on this important prototype.

 

What was this "futuristic airplane?"  Who designed it?  What was its intended mission?  Why has it been lost?  Was it a forgotten part of the Sänger-Bredt program, an ancestor of the US Space Shuttle and Soviet Buran orbiters?  If it was not related to the RaBo, what was it
it?


 


 

 

Diagram of RaBo trajectory

After arcing to altitudes of several hundred miles at speeds of over 10,000 mph, the spacecraft would descend and encounter the upper atmosphere. The pilot would execute a high-g pullout as the craft "skipped off the atmosphere like a stone skipping on water." This cycle would be repeated several times as the vehicle slowed and descended on its global path. When it neared its target, the spacecraft would release a large conventional-explosive bomb that would enter the atmosphere at meteor speeds and strike with tremendous force.

 

It is conceivable that USAAF technical intelligence knowledge of this unique and strange concept resonated with Kenneth Arnold's June 1947 story of supersonic UFOs "skipping like saucers on water" and provided some Air Materiel Command UFO analysts with leverage for study of the saucer phenomenon on the basis of possible Soviet origin.

 


WWII German diagram shows RaBo inertial reference planes and trajectory measurement axes. Pilot was to navigate by taking star bearings during exoatmospheric ballistic peaks.


Diagram shows nuclear-bomb-like energy dissipation and radius of destruction produced by hypersonic impact of RaBo's ten metric ton conventional weapon on its primary target -- lower Manhattan