Stealth Aircrafts

Thursday, May 27, 2010

" No aircraft detected .. Radar is clear ... airspace is secure .. !! ????"



STEALTH meaning to hide, work secretly, hidden ...

Lots of Hollywood movies with the help of special effects would show aircraft disappearing from visual ... and trying to show how stealth works buts that's not how actually it works.


EARLY DESIGNS :-

The earliest of Stealth Aircraft of the world is seen to be the Horten Ho 229 fighter-bomber, developed in Germany during the last years of WWII.



Designed by Reimar and Walter Horten and built by Gothaer Waggonfabrik. It was the first pure flying wing powered by a turbojet and was the first aircraft designed to incorporate what became known as stealth technology.


The Ho 229 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 1.8x 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.


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.


The aircraft utilized retractable tricycle landing gear, with the nosegear on the first two prototypes sourced from a He 177's tailwheel system. A brake parachute slowed the aircraft upon landing. The pilot sat on a primitive ejection seat.



DEVELOPMENT HISTORY :-


In the end days of the world war II , the US allied forces and the USSR red army, both were in the race to capture the German R&D facilities and developed prototypes of war. With the US launched Operation Paperclip - large portions of German prototypes were captured mainly V1, V2, V3 (Ho-229).. .and numbers of scientist involved in these projects were given US citizenship on request. USSR too had its share taking V1 and V2 and
Heinkel He - 178 and He - 280 prototypes.

Meanwhile, during the war US based Aircraft development company - Northrop - also was working on a similar project as of Ho-229 flying wing body aircraft known as YB - 49 series which later got scrapped due to funds problem as well as constant failures in YB - 49's flight stability.

The secured prototypes from Germany were sent to Northrop and Lockheed for analysis which laid the foundation for the advance stealth fighters in the coming years.

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After the war Reimar Horten said he used a mixture of charcoal dust with wood glue to absorb electromagnetic waves of radars. Though no documents exist to confirm that Germany was working on any stealth technology development, this information made grounds for further research. Later the theories of Mr. Horten on stealth were proved correct by Northrop- Grumman and Lockheed-Martin.


With the end of WWII and start of the cold war, the two most powerful states of the world were in a race to make each other feel inferior and to balance the power in the world. This lead to rapid development in various kind of technologies specially in the field of military and intelligence. USA and USSR fought numbers of wars , none face to face, but all with the weapons and intelligence gatherings. Thus it became important to both that they secure their countries, USSR started to develop a range of long-range RADARS and made it difficult for US to infiltrate its aerospace.


This initiated the requirement of a high altitude, Low Observable, High speed reconnaissance aircraft by USA. Lockheed-Martin's SKUNK WORKS under Clarence Kelly Johnson presented what is known as U-2 Spy plane codenamed "Dragon Lady".




Although not completely stealth , but designed to operate at very high altitudes U- 2 was suppose to be hidden from the radar detection of USSR air defense network. But on May 1, 1960 , a U-2 spy plane , flown by Francis Gary Powers, was shot down while taking photographs of USSR nuclear plants and vital SAM sites. This made clear that as previously expected , USSR 's long-range radar coverage was better than it was told.

With the aging of U-2 , USAF required a new and better spy plane. Once again Lockheed-Martin secured a contract. The previous research laid
the way for a very high speed , high altitude low observable aircraft now known as the SR - 71 BLACKBIRD. Designed to have low Radar cross sections and drag at high speeds .. Blackbird used RAM or Radar Absorbing Material (came from U-2) , Operating at an altitude of 70,000 to 80,000 feet and at a speed of Mach 3.2 to avoid radar contact, Blackbird served in many wars collecting vital data, pictures and information on enemy.

Image of SR-71 Balckbird Cutaway.


SR-71 remained a spy/reconnaissance plane forever. The success of the SR-71 project encouraged USAF to launch a project "
HAVE BLUE" for the development of a stealth fighter/bomber to invade enemy airspace and have first kill capability.

Image of a HAVE BLUE/ Hopeless Diamond prototype.


In 1964, Russian mathematician P.Y.Ufimtsev published a seminar on " Method of Edge Wave in Physical Theory of Diffraction"and showed that the returning RADAR waves after hitting aircraft body is more related to the edges present in the aircraft than its size and one can calculate the RCS or Radar Cross-Section Area across the wings and edges of the aircraft. Thus no matter how big a aircraft is in size, it RCS (representing a DOT on the RADAR screen) can be reduced by producing multiple edges at certain angles. However such a design will make the aircraft system aerodynamically unstable to fly.


After suffering heavy causalities on bombers against sophisticated SAMs of Soviet origins in Vietnam war,in 1980, USAF decided to get a bomber that can penetrate enemy air defense silently. Thus DARPA (Defense Advanced Research Projects Agency) announced the project "HARVEY". The contenders being Northrop and Lockheed.


The Lockheed advance projects team now called as SKUNK WORKS started to work on a top secret project codenamed "HOPELESS DIAMOND" as the initial prototypes for such a aircraft/bomber. The designs this time came from Ben Rich , a team member of Kelly Johnson 's, and a engineer in SR-71 team. Using the research of Ufimstev and computer aided control systems they presented two prototypes of hopeless diamond.

As first thought , just like its name , Hopeless Diamond was not quite satisfactory to the design team , still the RCS of the HOPELESS DIAMOND came out to be 1/10th of the RCS of Northrop-Grumman team.The radar operators used to check the presence of the prototypes as they became completely invisible on the screen during RCS tests by DARPA. Success of the HOPELESS DIAMOND initiated a dark project, completely top-secret and unknown to the world and even to the pilots and the R&D team known as project "HAVE BLUE".

The Have Blue prototypes being test vehicles missed many advancements and sophistication. After the contract was awarded to Lockheed the modifications started and the HAVE BLUE was was upgraded to "SENIOR TREND" which finally was renamed, after rigorous tests, as F-117A "Nighthawk" Stealth Bomber.



It was not until April 1990, that F-117 made their debut in a war. In 1990, US launched an offensive on Panama in Operation JUST CAUSE , and for the first time it checked the effectiveness and long waited war operational capability of the bomber.

But the actual test and experience came during Operation DESERT STORM, which witnessed large numbers of F-117As in combat. Only F-117A was allowed as the first wave of attack as well as to enter the fortified Baghdad. Although only 42 Nighthawks were used, they inflicted a 80% hit rate using GBU / Guided Bomb Unit (LGB and JDAM) munitions, hitting more than 30 % of the high profile targets in first 24 hours of the Operation Desert Storm, thus rupturing the backbone of enemy by destroying the targets as well as the air defense network achieving the objective it was designed for.

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F-117 design success came with certain problems regarding its limitations with range and payload (as a compromise for stealth). Thus , in 1979, "BLACK PROJECT" , which involved the R&D of top secret stealth programs, started to look for new bomber , much better, versatile , advanced and have a larger payload (also nuclear) and increased range capability, was termed as the Advanced Technological Bomber (ATB).

This time, as per the requirements, the Northrop-Grumman Designs were selected in competition with Lockheed/Rockwell designs.

Based on the old , and scrapped designs of Mr. Northrop, design team started working upon the YB -49's blueprints. With latest and advanced CAD (Computer Aided Design) and presence of the composite material made the "FLYING WING" design possible and the previously encountered flight instability was counter-measured using advance on-board computers. In 1989, Northrop introduced B-2 "Spirit" heavy bomber with advance LO (Low Observable) features or stealth.But no one expected that it would take a decade to get this advance technology war tested.





In 1999, following massive uprising and hostile environment in Yugoslavia, USA sent its B-2 stealth bombers to invade and fragile the air defense network. B-2 was responsible for the 33% hits of the Serbian targets in the first eight weeks of US involvement in Kosovo War.


RECENT DEVELOPMENTS :-

With F-117 and B-2 becoming successful and popular world over their technology also became obsolete for USA who always like to have a edge in technology in war. The developments of anti-stealth defense systems as well as the maintainance cost and various trade-offs (compromises) on conventional functions of aircraft like range, speed, aerodynamics, countermeasure systems, payload, limited role in war and cost of production ... led to initiate the development of more mordern and advance projects in USAF both being awarded to Lockheed/Rockwell .. YF -22 now know as F-22 "RAPTOR" advance, air-superiority, multi-role stealth aircraft and X-35 , known as the latest F- 35 "JOINT STRIKE FIGHTER".









F-22 incorporates various new features of stealth , without setting any trade off with speed and conventional aircraft features, although payload still being a factor of concern. It uses advance radar and avionics systems to locate the target, and attain the "FIRST LOOK - FIRST SHOT - FIRST KILL" capability. Both F-22 and F-35 have the capability to obtain the information from various ground systems as well as even from the enemy locations. Incorporating AESA radar and surface fused sensors technology.




Unlike F-117 and B-2, F-22 and F-35 have the afterburners for dogfights and high speed scenarios. F-22 also exhibits THRUST VECTORING whereas F-35 for the first time after BAE - SEA HARRIER aircraft incorporates a VTOL (Vertical Take-Off and Landing) System.





On the other hand , now Russia, with its always new designs have introduced SU-47 "BERKUT" or "GOLDEN EAGLE" with the ideal stealth designs with the help of carbon-composites - Forward Swept Wings - and state of art avionics.




More advance researches are still going on now with various nations to get the hold of stealth technology, which have now chaged the face of the war limiting it to few days time giving hard precise hits on enemy without getting a scratch.

NEW ONGOING RESEARCH:-

Russian/India - PAK FA - FGFA and lot many more. We still will be seeing lots of advancements, limited, but still to come in the chapter of stealth systems.







(Stealth Technology, Working and Terms will be included in the upcoming articles)


CONCLUDED


5 comments:

Anuj Shail Gupt said...

Hey... Good going man. Good to see that you are giving wings to your passion.

One suggestion: Dont use multiple fonts especially in a single post. That reduces the readability and makes it low on aesthetics.

RMB said...

Now its cool!!!!
Keep it up.

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