Introduction

The F-117 & the B-2 have firmly ingrained the shape of stealth in our collective imagination. Stealth represents the pinnacle of technology, power & supremacy. To truly understand stealth we need to go back to the beginning.

Stealth is a form of camouflage. The earliest forms were natural cover for example in forests, armies marching by night or hunters disguising themselves to blend with their surroundings. In the early days of aviation stealth as a concept did not exist. Flying in WW1 was mainly at night or Zeppelins flew noiselessly at high altitudes or under cover of night.

The concept of Radar was first introduced in 1886 by Heinrich Hertz who observed that radio waves deflect off metal bodies. The development of Radar in the 1920s & 1930s by both Germany & Britain also began the idea of radar avoidance. There was little understanding of how Radars actually detected metal objects or the concept of RCS (Radar Cross Section).

The first experiments with stealth began in WW2 and the most famous example of stealth albeit accidental is the Ho-229 by the Horten Brothers. A flying wing that had a severely curtailed RCS due to its combination of design & materials. Another example of accidental stealth is the  DeHavilland Mosquito, which had a low RCS because it was made of wood.

These aircraft are considered stealth generation zero some stealth and high maneuverability.

The Lockheed SR-71 and the Blackbird Family of aircraft are the first aircraft where stealth was conciously applied.  The Blended Wing Fuselage (read : https://theaviationevangelist.com/2025/09/19/the-flying-wing-part-two-the-blended-wing-body/ ) and inward canted vertical stabilizers were intended to divert radio waves away from the emitter/receiver in addition to the fins being contructed from early composite materials.

The paint on the aircraft was radar absorbing and consisted of iron particles to convert radar waves to heat, plasma stealth was experimented on the A-12 Oxcart where fuel contained a cesium based additive that created an ionized cloud of exhaust to absorb radar waves. The RCS of the SR-71 was bigger than a bird but smaller than a man. The SR-71’s biggest weapon was its speed at over Mach 3.0

The Blackbird Family of aircraft are the first generation of stealth combining speed and low maneuverability.

The Concept of Stealth was formalized by Russian electrical engineer & mathematical physicist Pyotr Ufemtsev when he published his epochal research now known as ‘Physical Theory of Diffraction’ (PTD) in 1962.

Pyotr Ufemtsev

While at Institute 108 (a key institute in the research of radio & radar technology) in 1954 Ufemtsev began his research into the reflection of electromagnetic waves and began developing a high frequency theory for predicting the scattering of electromagnetic waves from 2 & 3D objects.The shapes of the objects included discs, cylinders, cones, flat bases and wires in addition to several other geometrical shapes. These findings together came to be known as PTD and were published in his book ‘ Method of Edge Waves in the Physical Theory of Diffraction’ (PTD for short) in 1962.

The Russian think tank deemed the findings to have no significant military value and okayed his book to be published internationally. And the book languished for over a decade, before it was rediscovered by Denys Overholser of Lockheed. However this comes later.

Ufemtsev continued with his research in yet another gray forgotten facility in the former USSR for another twenty years. Gorbachev’s Perestroika gained traction in 1985 and the scientific funding that most of the institutes in the USSR received began to dry up. In the words of Ufemtsev, science took a back seat and political reform took center stage.

In 1989 Ufemtsev was in Stockholm to attend the Technology Symposium when in his own words he was surrounded by about ten Americans who said they were his students. You can imagine his shock as most of these ‘students’ looked middle aged and were professors themselves. One of them was from the University of California and offered him a position of visiting faculty. By this time USSR had almost fallen and Ufentsev was free to leave, which he did and Ufemtsev & his family found themselves in sunny California in University accommodation. It was here that could resume his research that was close to his heart. He was asked for a plan of reserach and funds were released direct from NASA to UCLA.

All this while Ufemtsev claims he was unaware stealth aircraft were being developed using his theory. His lecture at the 1992 National Convention of Science & Technology in Nice, France was one which was closely anticipated and watched by the Americans! Why? You might ask, the lecture was about how to defeat stealth.

Most radars of the time were monostatic radars. To put it simply, both the receiver and the transmitter of the radar are in one unit, so radio waves travel both and forth down the same corridor. At full absorption the radio energy is at coefficient zero or 50% absorption. He further explained that stealth aircraft were surrounded by a dispersed energy field, however there was no physical manner of decoding this. 

The other manner of defeating stealth was to have the bistatic or multistatic radars, where the transmitters and receivers are separated by varying distances. This increases the complexity of the unit, however as stealth aircraft are primarily about deflecting the radio waves away from the transmitter, the chances of being caught in a multi static radar array are much higher. The technology has been around since the 1920s, however post Ufemtsev’s lecture and the continued rise of stealth, bi/multistatic radar has seen a resurgence since the 1990s.

Into his 90s now Ufemtsev is the father of stealth. 

Project Harvey

The 1973 Yom Kippur war was a major wake up call for the US. The 19 day war was lethal for US made aircraft. Of the total 102 aircraft lost, 85 were American made, 32 F-4 Phantoms & 53 A-4 Skyhawks. The Soviet made S-75 Dvina missiles were part of an integrated air defense system supplied by the USSR to the Egyptian & Syrian forces were lethal against Israeli aircraft.

The war and result was a huge wake up call for DARPA (Defense Advanced Research Projects Agency) who initiated Project Harvey. Harvey the name from Harvey the Rabbit an invisible six foot tall white rabbit from the 1950 movie.

US strategic planners realized the vulnerability US aircraft & forces faced if they were ever to be in a similar high threat environment. In 1974 Chuck Myers, Director of Air Warfares Programs, espoused the ‘ Harvey ‘ concept to Robert Moore, Deputy Director of DARPA. They needed a new aircraft that would be invisible to enemy radar, infrared and other sensors. The idea almost immediately gained the support of the Pentagon and DARPA took the lead. This led to the highly classified ‘Have Blue’ program. DARPA invited McDonnell Douglas, Grumman, General Dynamics, Fairchild & Northrop. Lockheed was a surprise entry, they were initially not invited, however they leveraged their experience with the A-12 & SR-71 projects with DARPA and won an invite.

The final two projects accepted by DARPA were Northrop & Lockheed and after testing both model mockups (they were surprisingly similar) Lockheed won, and this would result in the legendary F-117 Nighthawk.

Have Blue & The F-117 Nighthawk

Ben Rich who succeeded Kelly Johnson as Director of Lockheed Skunk Works put together a team of talented individuals across several critical fields,  they consisted of Bill Schroeder a veteran designer, Dick Sherrer preliminary designer, Denys Overholser among many famous names.

Denys Overholser recommended an aircraft with flat surfaces. In Overholser’s own words “Well, it’s simple, you just make it out of flat surfaces and tilt those surfaces over, sweeping the edges away from the radar view angle, and that way you basically cause the energy to reflect away from the radar”. Using Overholser’s recommendations, Dick Scherrer drew a preliminary aircraft with low RCS. The aircraft had faceted surfaces. The aircraft looked like anything but an aircraft and definitely did not look like it would fly.

Over the next several weeks Overholser and Scroeder put together a computer team to create a prediction software called ‘Echo 1’. Ufemtsev’s calculations were incorporated into the software (Ufemtsev’s work had been translated by USAF Systems Command Foreign Technology Division which Overholser accidentally discovered). The final design would be a faceted delta wing that was stuck with the name ‘Hopeless Diamond’ a reference to the famous Hope Diamond at Smithsonian. The team took six months to convert Ufemtsev’s calculus to design. On March 7th 1974 at 02:47 a.m the code had its moment of epiphany, pyramids reflected no radar. These shapes were to be incorporated into Have Blue. Kelly Johnson who was sceptical of stealth said to Ben Rich “Our old D-21 drone (a mach 3.3 drone, Kelly Johnson loved speed) has a lower cross section than that goddam diamond”. The shape of Have Blue was limited by the computing power available at the time to create complex shapes, and hence the extremely faceted design.

In the summer of 1975 DARPA formally invited Northrop & Lockheed to develop the Experimental Survivable Testbest (XST). Both the shapes looked surprisingly similar. Northrop used a software called ‘GENSCAT’ similar to ‘Echo 1’. By Nov 1975 both Lockheed and Northrop were awarded $1.5 mn each to build a full scale mockup of their designs to be tested for their RCS signatures. It is important to remember here the designs were about stealth and not about aerodynamics. Lockheed won the round and were asked to build a flying test bed. Northrop were asked to continue with their own development, but were not part of Have Blue anymore.

Lockheed were to build two demonstrators for testing and Ben Rich raised over $10 mn from Lockheed management for development. The demonstrators were ¼ th the size of the final F-117 Nighthawk. They had a wing sweep of 72.5° and had an inverse V tail. It had a wingspan of 22’6” and a length of 47’3” and a MTOW of 12,500 lbs. The small aircraft was powered by two GE J85 turbojets that developed 2950 pounds of thrust each giving it a max speed of 600 mph.

The shape of the aircraft meant it was extremely unstable and it had a quadruple redundancy fly by wire control system that gave the aircraft normal flying characteristics. However actual flights tended to be extremely wobbly, something the F-117 shared with Have Blue and came to be called Woblin Goblin. The two prototypes flew a total of 88 flights between them, before both of them crashed. HB1001 flew a total of 36 sorties and HB1002 flew a total of 52 sorties. Both the pilots were safe. The Have Blue shape was very similar to what Ufemtsev had envisaged.

The final shape of the F-117 Nighthawk  had sides that were at least 30° off the vertical with multiple polygonal shapes. The aircraft now sported a V tail. The serrated edges that would be found on the F-117 Nighthawk were all about diverting radar waves away from the point of origin. The final radar cross section of the F-117 is about 0.001 m2 . The length was 65’11” and wingspan was 43’4”, the MTOW was 52,500 pounds with internal weapons bays.

The F-117 was powered by two modified GE F404 – F1D2 family of low bypass turbo fans. In the interest of stealth the engines had no afterburners. The engines were buried deep inside the aircraft to avoid radar waves hitting the fan blades as these give a very loud RCS return. Furthermore both the intakes were covered by a composite radar absorbing grill, so any radar waves that got in would not get out again. The exhaust was buried in a ‘platypus tail’ which was wide, rectangular and flat, furthermore exhaust heat was managed inside the long, buried exhaust duct lined with heat absorbing exhaust tiles. The bypass air was ducted over the tiles to cool them and further facilitate hot exhaust gas mixing with ambient cold air. Furthermore the hot exhaust air was directed at a very narrow angle just behind and above the aircraft.

The F-117 had almost one ton of radar absorbent material (RAM) consisting of several composites. The RAM actually impacted load and trim. The first was iron ball paint which consisted of polymer based paint infused with ferrite. The second was several layers of carbon based layered composite materials. When radar waves hit the iron balls oscillate and convert the electromagnetic waves to heat which is dissipated by the aircraft body. The RAM was cut much like a linoleum sheet and glued to the aircraft skin. The gaps between the panels were filled with a putty called butter. This ensured a seamless face to radar with no gaps. The glass of the cockpit was coated with a special composite mixture to absorb radar waves as well. In fact at one point of time Skunk Works toyed with filling up the cockpit with Carbon Monoxide, which would mask the pilot, however this was firmly rebutted by the pilots themselves!

The F-117 had a hinged radio antenna that hinged back into the aircraft body. Once retracted it meant the aircraft was silent with no contact. The pitot tubes themselves were designed to divert radar away from the emitter. In fact they were so sharp that one could cut a finger on them. The main pitot tube speed incicator had one hole that flew directly into the path of oncoming air for airspeed. This was also right out front in clean air. One of the reasons the F-117 did not go supersonic was to avoid shockwaves coming off the tube.

While Have Blue first flew in 1977, it was a black project and was only publicly disclosed in Nov 1988 after the disclosure of the B-2. 

The flyaway cost of each aircraft was $45 in 1981 dollars.

The F-117A is the second generation of stealth combining stealth with reasonable agility.

Tacit Blue & the B-2 Spirit

The Northrop Tacit Blue was a low observable stealth surveillance technology demonstrator aircraft. The aircraft could operate close or behind enemy lines with a high degree of survivability due its low probability of intercept radar (LIPR) and other sensors. The aircraft flew between 1982 – 85 but was publicly unveiled only in 1996.

The designation YF-117D represents an evolution on both Have Blue & F-117 programs. Tacit Blue was about demonstrating not only the next level of stealth design but other advances such as radar sensor technology was part of the ‘ Assault Breaker ‘ program that included technologies such as lasers, electro optical sensors, data processors etc that could break up ground launches working together in unison.

Tacit Blue, nicknamed ‘ the whale / alien school bus’ featured a straight tapered wing with a V tail.. The fuselage was curved in a manner to cut RCS, and ended in a rectangular edge all round that protruded. The engines had a single flush inlet on top of the fuselage that led to a S shaped curve as did the exhaust. The exhaust did not have the ceramic tiles the F-117 had but was instead lined with radar absorbent and heat resistant coatings. The exhaust nozzle itself was flat, wide and a curved arc that blended into the highly curved body. The nozzle was placed between the V tail. The setup ensured the engines would have no exhaust / intake signature on radar. 

The aircraft featured concealed radar as mentioned earlier so it could be in touch with its ecosystem at all times. The radar did not interfere with its RCS signature. The shape of Tacit Blue was possible because of strides in computing power that in turn enabled more complex radar cheating shapes. Overall a look at Tacit Blue tells you of a shape is continuous with no breaks and very reminiscent of the B-2 Spirit.

The aircraft used two Garrett ATF-3-6 medium bypass turbofans that produced 5,440 pounds of thrust each. The engines propelled the whale at 290 mph, which is reasonable considering the aim of the aircraft was reconnaissance and not speed. The aircraft had a service ceiling of between 25-30,000 feet. 

The materials used on the aircraft were aluminium for the fuselage and wings structure with Titanium in structural components. The empennage, wing & fuselage leading edges used proprietary Northrop radar absorbent composite materials. The RAM continued to use ferrite materials that were highly radar absorbent, however unlike the F-117 the material could be applied to the continuous curved surfaces and not have to use butter in between panels.

Tacit Blue flew a total 135 sorties and 250 hours over a three year period and gathered valuable data that was used in the B-2 Spirit. 

The B-2 was the spiritual successor to Tacit Blue. It incorporated several technologies from both Tacit & Have Blue. The S shaped engine intakes and active exhaust gas management. The curved surfaces of Tacit Blue showed that improvements in computing power meant stealth aircraft shapes could be complex curves. The radar integration on Tacit Blue is on the B-2 as well. 

The Advanced Technology Bomber program as the B-2 was known began in 1979. The black project codenamed Aurora narrowed on the Northrop/Boeing & Lockheed/Rockwell teams to begin preliminary work. Both the teams came up with Flying Wing designs with Northrop’s proposal codenamed ‘Senior Ice’ & Lockheed’s as ‘Senior Peg’. Northrop’s proposal won as they already had experience with flying wings from their YB-35/49 days , their aircraft was larger & was a pure flying wing. Lockheed’s proposal was more like its Have Blue program featured a faceted design and incorporated a small tail. Northrop was awarded the contract in late 1981.

For the Northrop the B-2 Spirit was the culmination of almost 40 years on flying wing aircraft ( read: https://theaviationevangelist.com/2025/09/13/the-evolution-of-the-flying-wing-part-one/ ). Flying wings are naturally stealthy along with the technologies validated by participating in the Have Blue and Tacit Blue programs.

In its final form the B-2 is a lambda wing and is made of mostly carbon graphite composite material, with buried engines that have S shaped ducts for intakes and active exhaust management. The RAM on the B-2 is even more advanced than on the F-117 & Tacit Blue. While the material continues to be classified we can speculate it uses alternate high frequency material to reduce maintenance post each sortie. The iron ball paint technology is probably used as well in addition to signature control materials such as sealants (butter?), and conductive tapes. All of this gives the B-2 a radar profile of 0.1 m2 .To protect the coatings the B-2 is stored in environmentally controlled hangers called B-2 shelter systems (B2SS).

The length of the B-2 is 69 feet with a wingspan of 172 feet (same as the YB35/49) and a height of 17 feet. Its MTOW is 376,000 pounds. The engines on the B-2 are four GE F118 non afterburning low bypass turbofans that develop 17,300 pounds of thrust each. The cruise speed of the B-2 is 630 mph with a service ceiling of 50,000 feet and a range of 6,900 miles, all phenomenal statistics considering it is almost never seen!

By 2004 the total program had cost $44.75 bn. Calculating the cost over 21 aircraft produced the cost per aircraft comes to $2.1 bn!

The B-2 represents the third generation in the stealth technology evolution.

The YF-23 & the F-22 Raptor

By 1986 the Soviet Union had several emerging threats such as the Sukhoi Su-27, the Mikoyoyan MIG-29 fighters and the under development Beriev A-50 airborne warning & control system (AWACS) along with increasingly sophisticated SAMs. The US needed to replace its aging air superiority fighter the F-15 Eagle. The Advanced Tactical Fighter (ATF) would use the stealth technologies developed along with advanced avionics, fly by wire systems, and advanced propulsion systems. Lockheed and Northrop were invited by DARPA as lead contractors of their respective teams due to their previous experience with all of the above. Lockheed’s proposal was dubbed the YF-22 & Northrop’s YF-23. Both aircraft had very similar properties.

The YF-23 nicknamed ‘ Black Widow II’ had two prototypes built. Northrop teamed up with McDonnell Douglas and the prototypes would run both Pratt & Whitney and General Electric engines. So while this was a competition between airframe manufacturers it was a competition between engine manufacturers as well.

Three design concepts were studied, the Agile Maneuverable Fighter (AMF) with two vertical tails, that had the best handling but the least stealth was the first. The second was the Ultra Stealth Fighter (USF) that had the best stealth characteristics called the Christmas Tree due to its design and the third was the High Stealth Fighter (HSF) which balanced stealth and maneuverability. It had diamond shaped wings and all moving V tail rudders. The third would eventually become the YF-23.Northrop received $691 mn as did Lockheed and given 50 months to create for demonstration & validation (Dem/Val) two prototypes each.

The YF-23s faceted & blended fuselage with its diamond shaped wings had very good RCS return of 0.001m2 , the steeply canted V tail (at 50°) gave the aircraft the agility it needed while at the same time blocking out the engine exhausts. The tail itself had the span of a small aircraft. A top view of the aircraft shows an alignment of all the edges along a couple of axis, this is critical to control radar return in a very narrow corridor. The engine intakes (at the entrance had a porous section) again had S shaped ducts similar to the B-2 and the exhaust had active gas cooling with ceramic tiles similar to the F-117. All weapons and radars were carried internally. The RAM continued to use the ‘iron ball paint’. Critical parts such as the all moving tail were made of advanced composite materials with high radar absorption. 

The YF-23 was tested with both the engine options. On the P&W YF119 option YF-23A number 1 flew a total of 34 flights for 44.3 hours. The maximum AoA at minimum speed was 25°, while the max speed was Mach 1.8 at maximum altitude of 50,000 feet..impressive numbers.

Prototype number 2 flew with the GE YF120 option, clocked 16 flights for a total of 21.6 flight hours. The max AoA at min speed was 20°, while max speed was Mach 1.72 at 50,000 feet max altitude. 

Both sets of numbers are impressive, while both the engines had afterburners the YF-23 could cruise comfortably at Mach 1.4-1.6 without them. An F-16 needed to afterburn to keep up.

The final specs of the aircraft was a length of 67’5”, wingspan of 43’7” and height of 13’11”. A MTOW of 51,320 pounds. The engines tested were two P&W YF119 and two GE YF120 that generated 23,500 pounds of thrust each (YF120) dry or 35,000 pounds with afterburner. The prototypes had to be constructed within a 3 month month period as their 50 month deadline was running out.

Lockheed teamed up with Boeing and General Dynamics to create the YF-22 which would become the F-22 Raptor. As stealth took centre stage the design team at Lockheed Skunk Works led by Bart Osborne moved away from its SR-71 type designs and once again came up with a design very similar to the F-117s faceted shape as they used the same computer program Echo 1. This design gave very poor aerodynamic handling characteristics. They needed to get better. They needed a design more like Northrop’s curved blended aircraft.

The final design submitted by Lockheed and team was vastly improved on the faceted design, incorporating curved shapes and surfaces. While the computers were not able to handle the design, physical reliance on radar range testing improved RCS while the curved shapes helped aerodynamics. The final design submitted for Dem/Val designated 090P had an arrow head forward fuselage, trapezoidal wings that had a steep crank on the leading edge and four empennage tail surfaces. The engines used the now familiar S shaped inlet and the rectangular exhaust nozzles and this is where the magic happened.

The nozzles featured a 2D thrust vectoring system that pivoted the exhaust stream down by up to 20°. This in conjunction with the all moving horizontal tail planes in conjunction with the twin vertical stabilizers (canted at 28°) gave the aircraft incredible pitch and stability control. And this probably won the F-22 Raptor contract.

The aircraft was constructed of composites which have now become a trend in stealth aircraft in addition to leading / trailing edge alignment all round. The large fins continue to mask the engine exhaust. The RAM on the YF-22 is a proprietary formula developed by Lockheed and Boeing an advancement on the iron ball paint formula and is done in layers. All hatches and openings on the aircraft are serrated much like the YF-23 to deflect radar waves away. In addition the surface of the aircraft is multiple shades of gray, these are different materials bonded together to further deflect radar waves and reduce RCS.

The first prototype with GE 120 engine first flew in September 1990 while the second with the P&W engines first flew in Oct the same year. The prototype with the GE 120 engines did a total of 43 flights for a total of 52.8 hours, maximum AoA at min speed was an insane 60°, while maximum speed was over Mach 2 at max altitude of 50,000 feet. The prototype with P&W engines flew a total of 31 flights for 38.8 flight hours, max AoA at min speed was 20° while max speed was MAch 1.81 at 45,000 feet. 

The YF-22 won, but it needs be said the YF-23 is a legendary aircraft in its own right. The F-22 Raptor final specs were a length of 62’1” and a wingspan of 44’6”. The MTOW is 83,500 pounds and is powered by P&W F119 engines that develop 26,000 pounds of thrust each dry and 35,000 pounds of thrust each with afterburner. The max speed is Mach 2.25 and range is 1,800 miles.

A total of 195 F-22 Raptors were constructed at a cost of $67.3 bn, at a unit program acquisition cost of over $350m each as the construction numbers were heavily curtailed from 750 as the costs proved to be prohibitively expensive and shifting priorities after the end of the Cold War.

The F-22 Raptor is the fourth generation of stealth incorporating speed and maneuverability.

The F-35 Lighting & The Democratization of Stealth

In 1993 DARPA launched the affordable Common Affordable Strike Lightweight Strikefighter (CALF) project to develop a stealth aircraft that would eventually repace the F-16, F-18 &Harrier across forces. The Joint Advanced Strike Technology project started in 1994. Congress order both of them to be merged and this became the Joint Strike Fighter (JSF). The fighter needed to a versitile fighter that was capable of Short Take Off & Vertical Landing (STOVL) and be capable of a supersonic dash while being stealthy. There were four submissions Mc Donnel Douglas, Northrop, Lockheed & Boeing.

By 1996 the two finalists were Lockheed and Boeing. Both were awarded $750 million each to build two concept demonstrators each. Boeing would develop the X-32 & Lockheed the X-35.

Boeing’s strategy was about keeping lifecycle costs down by minimizing variations across applications. The X-32 had a carbon fibre composite delta wing with a 55° sweep angle and a thick leading edge. This allowed the aircraft to have minimal transonic drag , aid lift at lower speeds and carry radio antennas internally.

The X-32 used a single P&W F119 powerplant that put out 28,000 pounds of thrust , dry and 43,000 pounds of thrust with afterburner. For STOVL the aircraft used thrust vectoring where the engine nozzle moved down upto 15°. The aircraft had a V tail canted to 58° each and an air intake that was directly beneath the cockpit reminicent of the F-16 and unfortunately could not achieve the kind of stealth required.

The final specs of the aircraft show a length of 45’0.1”, wingspan of 36’ & height of 17’3.8”. The MTOW of the aircraft was 38,000 pounds with all weapons to be carried internally. The max speed of the aircraft was 1,200 mph max range across profiles was 850 miles in the USAF profile. 

The X-35 used many design elements from the F-22 Raptor (and does not need to repeated) and the VTOL exhaust duct from the Covair Model 200 from 1972. Furthermore Lockheed had purchased technical data from the cancelled Russian Yak-141 for examination of its swivel nozzle in 1991. The aircraft used helmet mounted display systems that had already been around to integrate into the hardware.

The stand out element of the X-35 was the shaft driven lift turbofan. The design was pateneted by Lockheed engineer Paul Bevilaqua and developed by Roll Royce. During normal flight the engine behaved as a normal medium bypass turbofan with afterburners. The turbofan also acted as a turboshaft engine where the engine produces shaft power instead of jet thrust a concept used in helicopters.

Where the X-35 differs is only a portion of the jet’s power is directed to the shaft, the rest of the power is still directed towards a thrust vectoring engine nozzle for hover mode. The nozzle can swvel to an astonishing 95° using the 3 Bearing Swivel Duct Nozzle (3BSD). The aircraft can transition from normal flight mode to hover inflight. The shaft in turn drove a two stage titanium lift fan that was 50” in diameter. The entire fan assembly and housing weiged in 1.2 tons, a deadweight during normal flight. In the interests of stealth the far was closed out from both top & bottom when not in use and was a dead weight during normal flight.

The final specs of the aircraft was a length of 50’5” , wingspan of 33’ & height of 13’3”. The MTOW was 50,000 pounds and powerplant was the P&W F119 turbofan that generated 25,000 pounds of thrust dry and 40,000 pounds with afterburner. The max speed was Mach 1.5+ and a max range of 1,400 miles with a service ceiling of 50,000 feet.

The X-35 won mainly on the basis of its extremely versitality and would become the F-35 Lightening. The final unit cost of an average of just over $100 mn a unit across variants represents a huge improvement in costs.

The F-35 represents the Fifth Generation of stealth aircraft.

Since the 2010s as stealth technology has been better undertood & costs bought down countries such as China & Russia we have seen a raft of stealth aircraft make their way into pubic awareness. Of these the J-50 & J-36 from China stand out as they incorporate All Moving Wingtips (AMT) along with tailess designs ( read here : https://theaviationevangelist.com/2025/10/02/lambda-wings-moving-wingtips-flying-wings-part-3/ ). The Chinese also have the J-20. Tailess aircraft being naturally stealthy. A late edit: A Chinese Team has recently unveiled an evolutionary new stealth material that has a durable and flexible coating that is extremely thin at just 0.1mm. Furthermore one of its properties is impedance tuning , adjusting dynamically to ambient surroundings including temperature. Such a property is critical to advanced stealth as it controls the material’s interaction with incoming electromagnetic waves from radars within range. This is a developing story and not many details are known yet.The Russian Su-57 is another example of stealth technology at work. The US has the B-21 Raider the the F-47 under development, both of them promise to be interesting developments in the evolution of stealth.

Stealth is the standard by which air superiority aircraft are measured.

The Future

The advent of drones like the loyal wingman, the Lockheed Vectiss is a stealth drone that flies ahead in high risk environments and ensure surviveability for airmen. This also represents the connected environment stealth enconpasses, it’s not just about stealth its about communicating effectively.

Stealth has spurred the evolution of radars. Bistatic & multistatic radars are getting more sophisticated (they are complex). RAM is optimized for high frequency but low frequency are getting better at stealth aircraft detection. Over the Horizon radars have the ability to monitor vast areas by bouncing their waves off the ionosphere. AI is playing a big hand in patching multiple data points to create a single picture this strenthens existing infrastructure. 

Quantum radar is in its infancy. Quantum radar looks at subtle changes in photons through quantum entanglement , this will render current stealth technology ineffective. We are getting better at detecting Ufemtsev’s theoretical radiation bubble around stealth aircraft. 

The next level of stealth is a cloaking device much like Star Trek!

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