The Horten Ho 229 was built and flown on several occasions but development was held back by numerous factors and the type never entered service.
Low observable technology, widely known to the world as stealth, aims to reduce as much as possible the infrared, visual, acoustic, and radar signatures emitted by vehicles, whether they are seaborne, airborne, or on the ground.
Even though advances in technology allow us to carry out aircraft missions without being detected, the history of signature management goes back over 100 years, as explained by David Baker in his book Fifth Generation Fighters.
The element of surprise had been sought by air fighters from the earliest days of aerial combat, where usually the sun was used to hide the presence of an attacker homing on an intended victim. With the introduction of radar targeting and interception during the Second World War, first for night-fighting and then generally for air defence, the parameters shifted to the electromagnetic spectrum. Radar works by receiving a return signal reflected from a solid object, the strength of the signal being proportional to the observed visibility of the object. That ‘observed visibility’ is a measure of the object’s radar he cross-section (RCS) and is dependent on the proportion of the signal which is reflected back.
Considerable secrecy surrounded the work on radar and ways to evade detection were carried out in German laboratories during the Second World War. After the German surrender, as the victorious Allied powers sought to obtain as much of this work for their own exploitation some ideas were researched and investigated using data and result from extensive studies and tests conducted toward the end of the war. One of those was the marriage of flying-wing design concepts and low-observables (LO) technology.
Some of the claims made by German designers were pure myth while other techniques inadvertently did contain stealth characteristics. One example was the Horten Ho 229 which was developed by Reimar and Walter Horten, advocates of tailless ‘flying-wing’ designs and built by the Gotha works in 1944. The German Air Ministry wanted a bomber capable of carrying a 1000kg (2200lb) bomb a distance of 1000km (620mls) at 1000km/hr (620mph). Only by reducing the cruise power, said the Horten brothers, could this condition be met. That could most easily be achieved by significantly reducing drag by creating a tailless, blended wing-body shape powered by jet engines buried in the wing/fuselage root. The Ho 229 was built and flown on several occasions but development was held back by numerous factors and the type never entered service.
The Horten brothers had been correct in selecting this design concept for minimum drag and the aircraft was certainly less visible to radar than a conventional aircraft of this size would have been. There were no abrupt angles between the wing and the fuselage, no large vertical tail to reflect radio waves and no propellers to appear as bright discs on a radar screen. When the type was subjected to a detailed analysis by Northrop Grumman long after the war it was determined that, with a wing span of 55ft (16.8m), it had only 80% of the visibility presented by a lightweight fighter such as the Messerschmitt Bf 109, which had a wing span of 32ft (9.8m).
But claims by Reimar Horten that he had mixed charcoal with the glue to bond the wood laminates of which the structure was made in an attempt to achieve a low reflection were rebuffed by a chemical analysis which showed there was no evidence of such a substance. However, we may be too quick to rebut this claim as there was indeed a noticeable change in the dielectric constant. Horten maintained the carbon charcoal, which would have significantly absorbed propagated radio waves, was to have been used in production versions while the V3 prototype taken to the US, and subject of tests, was the early-build which may not have had that additive.
The reason for this detailed scrutiny of the Ho 229 story is that, if it were true that the aircraft was conceived not only as a low-drag bomber but also to have stealth qualities, it was about 30 years ahead of its time. Yet the reality of this is lost in obfuscation, confusion, lying and finger-pointing.
After the war German scientists, engineers, technicians and labourers were only too willing to blame those no longer alive (usually in high political or military positions in the Third Reich) for missed opportunities, clearly ineffective decision-making or deliberate mismanagement; these men were also quick to claim they were aware of applications that, in reality, only became apparent when allied brains were matched with those from the German research facilities to point out subtle possibilities such as the variation of a shape to effectively produce a more stealthy design.
Fifth Generation Fighters is published by Mortons Books and is available to order here.
Photo credit: Michael.katzmann at English Wikipedia