Horten Ho 229

https://en.wikipedia.org/wiki/Horten_Ho_229

The Horten H.IX, RLM designation Ho 229 (or Gotha Go 229 for extensive re-design
work done by Gotha to prepare the aircraft for mass production) was a German
prototype fighter/bomber initially designed by Reimar and Walter Horten to be
built by Gothaer Waggonfabrik late in World War II. It was the first flying wing
to be powered by jet engines.

The design was a response to Hermann Göring's call for light bomber designs
capable of meeting the "3×1000" requirement; namely to carry 1,000 kilograms
(2,200 lb) of bombs a distance of 1,000 kilometres (620 mi) with a speed of
1,000 kilometres per hour (620 mph). Only jets could provide the speed, but
these were extremely fuel-hungry, so considerable effort had to be made to meet
the range requirement. Based on a flying wing, the Ho 229 lacked all extraneous
control surfaces to lower drag. It was the only design to come even close to the
3×1000 requirements and received Göring's approval. Its ceiling was 15,000
metres (49,000 ft).

The H.IX was of mixed construction, with the center pod made from welded steel
tubing and wing spars built from wood. The wings were made from two thin,
carbon-impregnated plywood panels glued together with a charcoal and sawdust
mixture. The wing had a single main spar, penetrated by the jet engine inlets,
and a secondary spar used for attaching the elevons. It was designed with a 7g
load factor and a 1.8× safety rating; therefore, the aircraft had a 12.6g
ultimate load rating. The wing's chord/thickness ratio ranged from 15% at the
root to 8% at the wingtips. The aircraft utilized retractable tricycle landing
gear, with the nosegear on the first two prototypes sourced from a He 177's
tailwheel system, with the third prototype using an He 177A main gear wheelrim
and tire on its custom-designed nosegear strutwork and wheel fork. A drogue
parachute slowed the aircraft upon landing. The pilot sat on a primitive
ejection seat. A special pressure suit was developed by Dräger. The aircraft was
originally designed for the BMW 003 jet engine, but that engine was not quite
ready, and the Junkers Jumo 004 engine was substituted.

Control was achieved with elevons and spoilers. The control system included both
long-span (inboard) and short-span (outboard) spoilers, with the smaller
outboard spoilers activated first. This system gave a smoother and more graceful
control of yaw than would a single-spoiler system.


Role
Fighter/Bomber

Manufacturer
Gothaer Waggonfabrik

Designer
Horten brothers

First flight
1 March 1944 (glider)

Primary user
Luftwaffe

Number built
3

The first prototype H.IX V1, an unpowered glider with fixed tricycle landing
gear, flew on 1 March 1944. Flight results were very favorable, but there was an
accident when the pilot attempted to land without first retracting an
instrument-carrying pole extending from the aircraft. The design was taken from
the Horten brothers and given to Gothaer Waggonfabrik. The Gotha team made some
changes: they added a simple ejection seat, dramatically changed the
undercarriage to enable a higher gross weight, changed the jet engine inlets,
and added ducting to air-cool the jet engine's outer casing to prevent damage to
the wooden wing.

The H.IX V1 was followed in December 1944 by the Junkers Jumo 004-powered second
prototype H.IX V2; the BMW 003 engine was preferred, but unavailable. Göring
believed in the design and ordered a production series of 40 aircraft from
Gothaer Waggonfabrik with the RLM designation Ho 229, even though it had not yet
taken to the air under jet power. The first flight of the H.IX V2 was made in
Oranienburg on 2 February 1945.

The V3 was larger than previous prototypes, the shape being modified in various
areas, and it was meant to be a template for the pre-production series Ho 229
A-0 day fighters, of which 20 machines had been ordered. The V3 was meant to be
powered by two Jumo 004C engines, with 10% greater thrust each than the earlier
Jumo 004B production engine used for the Me 262A and Ar 234B, and could carry
two MK 108 30 mm cannons in the wing roots. Work had also started on the
two-seat Ho 229 V4 and Ho 229 V5 night-fighter prototypes, the Ho 229 V6
armament test prototype, and the Ho 229 V7 two-seat trainer.

During the final stages of the war, the U.S. military initiated Operation
Paperclip, an effort to capture advanced German weapons research, and keep it
out of the hands of advancing Soviet troops. A Horten glider and the Ho 229 V3,
which was undergoing final assembly, were transported by sea to the United
States as part of Operation Seahorse for evaluation. On the way, the Ho 229
spent a brief time at RAE Farnborough in the UK, during which it was considered
whether British jet engines could be fitted, but the mountings were found to be
incompatible with the early British turbojets, which used larger-diameter
centrifugal compressors as opposed to the slimmer axial-flow turbojets the
Germans had developed. The Americans were just starting to create their own
axial-compressor turbojets before the war's end, such as the Westinghouse J30,
with a thrust level only approaching the BMW 003A's full output.

After the war, Reimar Horten said he mixed charcoal dust in with the wood glue
to absorb electromagnetic waves (radar), which he believed could shield the
aircraft from detection by British early-warning ground-based radar that
operated at 20 to 30 MHz (top end of the HF band), known as Chain Home. A
jet-powered flying wing design such as the Horten Ho 229 has a smaller radar
cross-section than conventional contemporary twin-engine aircraft because the
wings blended into the fuselage and there are no large propeller disks or
vertical and horizontal tail surfaces to provide a typical identifiable radar
signature.

Engineers of the Northrop-Grumman Corporation had long been interested in the Ho
229, and several of them visited the Smithsonian Museum's facility in Silver
Hill, Maryland in the early 1980s to study the V3 airframe, in the context of
developing the Northrop Grumman B-2 Spirit. A team of engineers from
Northrop-Grumman ran electromagnetic tests on the V3's multilayer wooden
center-section nose cones. The cones are 19 mm (0.75 in) thick and made from
thin sheets of veneer. The team concluded that there was some form of conducting
element in the glue, as the radar signal attenuated considerably as it passed
through the cone. However, a later inspection by the museum found no trace of
such material.

Expert Debunking of Stealth Claims

Due to the popularity of this documentary project, the Smithsonian has since
posted an extensive debunking of these claims citing their own research and the
paper published and presented at the 10th American Institute of Aeronautics and
Astronautics Aviation Technology, Integration, and Operations (ATIO) Conference
held September 13 through 15 in 2010, in Fort Worth, Texas by the Northrop
Grumman team followed in the Myth Merchant documentary.

In his later life, Reimar Horten promoted the idea that the Horten Ho 229 V3 was
intended to be built as a stealth aircraft, which would have placed this jet’s
design several decades ahead of its time. Reimar Horten claimed that he wanted
to add charcoal to the adhesive layers of the plywood skin of the production
model to render it invisible to radar, because the charcoal “should diffuse
radar beams, and make the aircraft invisible on radar” (Horten and Selinger
1983). This statement was published in his 1983 co-authored book Nurflugel
(which translates as “only the wing”). While this statement refers to the
never-made production model, it seems possible that the experimental charcoal
addition could have been used on the Horten Ho 229 V3 prototype. The mere
mention of early stealth technology sparked the imagination of aircraft
enthusiasts across the world and spurred vibrant debate within the aviation
community.

The stealth myth has been growing since the 1980s and was invigorated when the
National Geographic Channel, in collaboration with Northrup Grumman, produced a
documentary called "Hitler's Stealth Fighter" in 2009. The program featured the
Horten Ho 229 V3 as a potential "Wonder Weapon" that arrived too late in the war
to be used (Myth Merchant Films, 2009). The documentary also referred to the
jet's storage location as "a secret government warehouse," which added to the
mystique of this artifact. Since the airing of the documentary, public pressure
has increased to remove the jet from its so-called secret government warehouse
and put it on display. In fact, this secret warehouse is the Museum's Paul E.
Garber Facility in Suitland, Maryland where a team of conservators, material
scientists, a curator, and aircraft mechanic has been evaluating the aircraft.

The Smithsonian has performed a technical study of the materials used and
determined that there is "no evidence of carbon black or charcoal in the Horten
jet" thus invalidating the proposed mechanism for an essentially non-existent
radar absorbent property as compared to the control sample of plywood used in
the original testing.


"The Ho 229 leading edge has the same characteristics as the plywood except that
the frequency exactly match and have a shorter bandwidth. This indicates that
the dielectric constant of the Ho 229 leading edge is higher than the plywood
test sample. The similarity of the two tests indicates that the design using the
carbon black type material produced a poor absorber."

Dobrenz and Spadoni use the term 'absorber' to refer to the ability of the Ho
229 leading edge to absorb the radar signal rather than reflecting it back to
the antenna receiver. More absorption means less reflected signal and greater
stealth. The authors assumed in their paper that crafts persons used the "carbon
black material" to lower the RCS, however, our technical study findings
described above found no evidence of carbon black or charcoal in the Horten jet.

Specifications (Horten Ho 229A (V3))

From manufacturer's estimates—

General characteristics
Crew: 1
Length: 7.47 m (24 ft 6 in)
Wingspan: 16.76 m (55 ft 0 in)
Height: 2.81 m (9 ft 2 in)
Wing area: 50.20 m² (540.35 ft²)
Empty weight: 4,600 kg (10,141 lb)
Loaded weight: 6,912 kg (15,238 lb)
Max. takeoff weight: 8,100 kg (17,857 lb)
Powerplant: 2 × Junkers Jumo 004B turbojet, 8.7 kN (1,956 lbf) each

Performance
Maximum speed: 977 km/h (estimated) (607 mph) at 12,000 metres (39,000 ft)
Service ceiling: 16,000 m (estimated) (52,000 ft)
Rate of climb: 22 m/s (estimated) (4,330 ft/min)
Wing loading: 137.7 kg/m² (28.2 lb/ft²)
Thrust/weight: 0.26

Armament

Guns: 2 × 30 mm MK 108 cannon
Rockets: R4M rockets
Bombs: 2 × 500 kilograms (1,100 lb) bombs.





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