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Friday, May 13, 2016

That's Airpower For You!-1

Elephant Walks in South Korea During 
EX Beverly Herd 16-01
Now, what follows below is what one does not get to see, since they are all the end-products of 
In the late 1970s, the USAF initiated the Compass Cope R & D project to develop a tactical, survivable reconnaissance UAV. The mission envisioned for the aircraft would seem familiar today, for are nearly identical to that of the Northrop Grumman-developed Global Hawk UAV, and in many ways the two aircraft are similar. Boeing beat out Teledyne Ryan for the Compass Cope contract, only to have the project terminated soon after the competition ended in 1979. Around the time that Compass Cope was cancelled, the USAF had several aerospace companies study an Advanced Remotely Piloted Vehicle (ARPV). This would a mid-sized RPV with limited stealthy features and missions, including reconnaissance, EW, and precision-strike. Soon after the contractor studies were complete, the USAF ended the project. Beginning in 1978, Northrop Grumman began to study how to apply low observables experience gained from the Have Blue (and later Tacit Blue) projects to a number of roles, ranging from cruise missile carriers to loitering reconnaissance platforms. A number of older studies of flying-wing and span-loader aircraft were dusted off and scale-models were tested on indoor ranges to determine if any aircraft configurations had any ‘natural’ stealth qualities. 
The Have Blue project had left a very bad taste in Northrop Grumman’s mouth and it had nothing new lined up to keep money coming in, and Lockheed Martin’s XST had beaten its design by a considerable margin—largely due to Lockheed Martin’s experience with materials from the Oxcart project and the ECHO 1.0 software package. Northrop Grumman had little experience with the kind of computing required to predict RCS (ironically, Northrop Grumman’s employees started most of the world’s major computer and semiconductor companies, such as IBM) so they had to make do with trial-and-error and commercial radar absorbent materials. At DARPA’s request, Northrop Grumman in 1978 began studying a stealthy radar-carrying platform under the Battlefield Surveillance Aircraft Experimental (BSAX) project. At the same time, Northrop Grumman was working on its own to develop new projects that would be of interest to the US Dept of Defense. One of these was Tacit Rainbow--a loitering anti-radiation missile. Another concept was the Tactical High Altitude Penetrator, or THAP. Northrop Grumman had been looking at flying-wing span-loader aircraft for military use with great interest in the late 1970s. Recent advances in materials and flight-control technology made an advanced span-loader more possible than ever. Missions ranging from super heavylift transports and aerial refuelling tankers to intercontinental bombers were studied. A separate group at Palos Verdes investigated the span-loader as a stealthy platform. A great deal of indoor RCS work was done on span-loader scale-models in the late 1970s. In June 1991, AW & ST reported that this was the TR-3A Black Manta—a classified tactical reconnasissance aircraft supporting the F-117A force with laser target designation and bomb damage assessment. The article also identified the TR-3A as an outgrowth of the THAP concept, but it carried not a bay full of reconnaissance gear, but rather an internal weapons bay holding a Paveway-2 laser guided bomb, which in essence made it a manned Covert Survivable In-weather Recon/Strike (CSIRS) platform. 
The TR-3A is obviously optimized for high-altitude (50,000 feet and above) loitering over denied areas--like hanging out over a ‘SAM City’. This would suggest a reconnaissance role. Precision-strike aircraft are designed to get in and out fast to minimize exposure to enemy air-defences. Reconnaissance aircraft typically go one of two ways: fast in and out, like the SR-71; or long time over target to keep an eye on movements of the target and collect more targetting data. Anything that has to hang inside hostile airspace will be designed with stealth in mind. The TR-3A was thus optimized for low-observables (using off-the-shelf technology, no less) and it cruised at the uppermost reaches of the threat envelopes of SAMs. Only a few SAM systems can reliably hit something above 50,000 feet. But even those systems are only marginally effective at that altitude. And the small amount of radar energy reaching up there does not exactly help the SAM hit its target. So the chances of bringing down a TR-3A at mission altitude are pretty slim. Reportedly in 1983, an industrial consortium of General Dynamics and McDonnell Douglas received a contract from the USAF to produce 30 airframes under the name ‘Tactical Survivable Aircraft’. There are a number of missions that can be assigned to the TR-3A in wartime. For one, it could simply be a system for attacking the same targets as an F-117A, though from high altitudes. This would be similar to a tactical version of the B-2B attacking SAM sites as they turn on, or casing down mobile targets like C4I faculties and land-mobile tactical ballistic missile/cruise missile launchers.
By the late 1980s, the Pentagon had identified the need for a stealthy multi-role combat aircraft (MRCA) that can remain aloft for long periods and loiter close to enemy territory, and then switch to a high-speed mode to rush in and deliver a surgical blow before rushing back out at supersonic speeds. These two modes of flight require drastically different wing profiles for maximum efficiency. In the mid-1990s reports began to surface concerning a new swing-wing aircraft sighted near Cannon AFB, New Mexico and at Langley AFB in Virginia. In September 1994, that aircraft—developed by Northrop Grumman and known as the Switchblade (its utility patent was filed in November 1999)—was observed circling high over Amarillo, Texas, for several minutes at midday. The aircraft was not a standard variable swing-wing aircraft, rather it was employing a unique forward sweeping-wing mechanism that enables the aircraft to become an attack aircraft capable of delivering precision-guided munitions (PGM), super-manoeuvrability (for air combat) and Mach 3 ‘dash’ capability. 
It is thus a bomber, interceptor and high-speed aircraft all-in-one. The wings are attached to the fuselage at a pivot point toward the rear of the aircraft. With its wings fully swept aft the aircraft can slow to drop PGMs or land on short runways. When the wings are swept forward 20 degrees the aircraft takes advantage of the manoeuvrability that forward-swept wings offer, thereby becoming a highly agile air combat platform. Sweep the wings fully forward and they become flush, with the aircraft with the trailing edge becoming the leading edge, forming a highly swept 75-degree stealthy delta ideal for high-speed Mach 3 exits.
Shape-shifting MRCAs that can alter their wing configurations in mid-flight (i.e. variable-wing geometry, or swing-wing) can generate greater efficiency and performance in various flight modes.  With its wings swept perpendicular to its body, the Switchblade can fly at lower speeds to drop PGMs precisely on their targets. With its wings swept farther forward, the aircraft becomes extremely manoeuvrable for aerial combat. When the wings are swept fully forward, the trailing edge of the wing becomes the leading edge, and the Switchblade can dash away at speeds up to Mach 3. 
Back in 1986, there was speculation among US military pilots and industry insiders that a new secret aircraft was being developed having the mysterious designation F-19. The rumours were partially substantiated by leaks within the aerospace industry, and a US$9.95 scale-model was produced by Testors Model Corp, which incidentally became the biggest selling plastic model kit of all time. At the very least, the USAF added to the confusion by skipping a designation between the McDonnell Douglas F/A-18 Hornet, and the Northrop F-20 Tigershark. This left a gap for an aircraft that may have held the designation F-19. It was said that the F-19 was a low-observable stealth aircraft that was being developed by Lockheed Skunk Works. However, when the F-117 Nighthawk was finally revealed to the public on November 10, 1988 rumoirs of the mysterious F-19 disappeared. It was assumed that the F-19 was in fact the F-117. Subsequent research indicated that this assumption was fundamentally incorrect, and that there really was an F-19. In 1979, a retired SR-71 pilot was flying a Learjet north of what is commonly referred to as Area 51. After breaking through a group of clouds, the pilot noticed a very strange-looking aircraft just ahead and to his lower left position (he had been shadowing the craft for approximately 10 minutes). The aircraft measured approximately 65 feet in length. It was completely black in colour, and had a flattened football or rounded-diamond shape, and appeared slightly more elongated in the front half. The X-15-like cockpit was a fully enclosed blister that tapered back towards the aft end of the craft. There were two forward-facing triangular windows on either side of a wedge shaped splitter pillar. 
The internally-mounted engines were fed by two NACA air-intake ducts slightly aft and to either side of the cockpit. There were also two additional air-intakes on the lower surface of the aircraft. The craft featured what looked like trapezoidal shaped or trap-door exhaust ports near the aft end. There were control surfaces on the leading and trailing edges. The most unique feature however, was a very unusual dorsal and ventral tail arrangement. The vertical stabiliser looked very similar in appearance to that of the old B-17 Flying Fortress, but with an identical stabiliser on the bottom. The lower ventral fin retracted sideways and up, to allow clearance for landing. This particular craft had afterburner capability.
All of the evidence indicates that this was a twin-engined hybrid propulsion design aircraft. It would appear that this particular aircraft, built in 1976, was a proof-of-concept (first generation) design for what was to be commonly referred to as the Aurora. The pilot was quite startled after seeing this aircraft, and contacted air traffic control (ATC) at Nellis AFB to ask: “why did you not advise me of the other traffic in my vicinity?” At this point, there was a short pause, and then ATC responded by saying: “because there is no traffic in your vicinity, Sir.” Next, the Learjet pilot responded by saying: “the hell there isn't! I’ve got an all-black, diamond-shaped, no wings, single-seat, twin-engined aircraft with ventral and dorsal vertical stabilisers, flying 100 feet out in my 11 o’clock position right now! I’m looking out my windscreen at it as we speak.” After a pause of 10 seconds or so, the Learjet pilot saw the pilot of this other aircraft look out of his right windscreen, register an expression of extreme surprise, then abruptly bank away while simultaneously lighting up the afterburners, and disappearing into a cloud bank. After a pause of 20 seconds or so, a different voice came over the radio, (a much harsher sounding voice) which directed the Learjet pilot to vector south where he would be landing at Nellis AFB. The pilot complied, and was told to taxi to the end of the runway, shut down his engines, and to not depart his aircraft. At this point, the pilot was met by USAF security personnel, and was interrogated for the next 18 hours about his encounter with the mysterious ‘black jet’.
In 1974, the US Defense Advanced Research Projects Agency (DARPA) initiated a programme known as Project Harvey (named after the 6 feet 3 1/2 inches tall invisible white rabbit from the play of the same name). The ultimate goal was to develop a combat aircraft with as low a RCS as possible. Five aerospace OEMs were contracted US$1 million each to give it their best shot. Surprisingly, Lockheed Martin wasn’t among them. It was only an accidental tip-off that allowed Lockheed Martin’s Ben Rich to lobby for inclusion. Rich had been an engineer on the secret U-2 and SR-71 reconnaissance aircraft R & D projects and had by then advanced to become Lockheed Martin’s successor to the famous Lawrence Kelly Johnson as Director of the Skunk Works. The ‘Skunk Works’ is the official alias for the Advanced Developmental Projects Division that is responsible for all of Lockheed Martin’s highly secret advanced development projects. It was formed in 1943 to build the US’ first turbojet-powered combat aircraft, the P-80, and numerous other projects that belong to the shadowy world of military operations.
By the time Rich had gotten wind of Project Harvey, there was no money left for another developmental contract. So Lockheed Martin was offered a shot-for-a-dollar. But Rich wanted in and wisely turned down the token dollar. He knew that any new technologies developed with company funds would then be proprietary. Lockheed Martin was famous for building small fleets of extremely advanced aircraft-often used for highly secretive missions. During World War-2, it had built the P-80. Subsequently, Lockheed Martin skipped the Mach-1 era altogether and jumped right to fielding the first US-origin combat aircraft capable of speeds in excess of Mach 2, the F-104 Star Fighter. Along the way came the high-flying U-2, the higher-flying SR-71, the hypersonic D-21 drone (which would ride piggyback on an SR-71 until released), and other things not yet named. In Rich’s own words, the unsung hero of Lockheed Martin’s effort was an anonymous staff mathematician and electrical engineer named Denys Overholser. Overholser and his mentor, another mathematician named Bill Schroeder, had discussed the possibilities of utilising some of the equations associated with optical scattering (how electromagnetic waves bounce off variously shaped objects) on this project. Both had the rather odd hobby of reading obscure USSR-origin mathematics papers and had made the ultimate ‘nerd's nerd’ discovery. They had stumbled across a paper published in Moscow a decade earlier titled ‘Method of Edge Waves in the Physical Theory of Diffraction’. It had been written by Pyotr Ufimtsev, the Soviet Union’s chief scientist at the Moscow Institute of Radio Engineering and the last in a long line of scientists developing a long series of wave-equations originally derived centuries ago by the Scottish physicist James Clerk Maxwell.
The US intelligence community had helped translate this research paper and brought it to the West. The paper was in no way classified or related to weapons development at all. It was purely theoretical math. Years later, Ufimtsev immigrated to the US to teach at the University of California, Los Angeles, and only then discovered his inadvertent contribution to the development of stealthy aircraft. The equations that Ufimtsev had developed made the reflections of radio waves off hard surfaces predictable. Not invisible, transparent, or tactical in any way-just predictable. The problem for Lockheed Martin was that the calculations were so ferociously difficult that the most advanced supercomputers in the world at that time could only compute results for flat surfaces. Any attempt to perform the calculations for the curved surfaces you would find on a conventional aircraft--well, those machines would still be grinding away toward a solution today. Schroeder recognised how these equations could be applied to Lockheed Martin’s current project. The solution was not even to attempt to design an aircraft with any curved surfaces, but to build one with dozens, or perhaps hundreds, of individual flat triangular and rectangular plates. Then the challenge was to compute the reflection from each and every flat surface before adding them all together to build a picture of the aircraft’s total radar signature. Once you knew where every bit of radar reflection was coming from, you could then reorient those individual plates so that the reflection would go off in a direction away from the radar looking at it. This process became known as ‘faceting’. And that became the real secret--not to absorb all the RF emissions or make the aircraft somehow transparent, but to make the aircraft’s signature predictable. That predictability could then be used to shape a tactically useful aircraft. The aircraft would also be covered in thin sheets of radar-absorbing materials (RAM), but the bulk of the stealth effect was achieved by its shape.
Traditionally, a single engineering specialty will take the lead during the design of a new aircraft. An aerodynamicist may be in charge of pushing through a new wing or fuselage shape, as happened with the early delta wings and area-ruled fuselages of the ‘Century Series’ of interceptors. Sometimes it may be the powerplant guy: “Here’s the engine we’re going to use, build us an aircraft for it.” This is how the P-80 came about. Occasionally it may be the armaments people-- the A-10 Warthog is fundamentally a massive 30mm Gatling cannon with an aircraft  built around it. In this particular case, this was the first time the lead was owned by an electrical engineer. The computing programme designed by Overholser’s team to make these calculations was called Echo- 1. Armed with that tool, the first test subject, the Hopeless Diamond, was built. It was described as a diamond for obvious reasons and ‘hopeless’ for its aerodynamic qualities (or rather, its complete lack thereof). Early radar testing of the Hopeless Diamond turned out to be staggeringly successful. The White Sands experimental radar range near Holloman AFB was used. 
When the radar was fired-up for the initial testing, the only thing that showed up was the reflection of the pole on which the full-scale test-model was supposed to be mounted. Assuming that the model had fallen off the pole, the radar operators sent technicians downrange to fix the problem. To their surprise, the ten-foot model was still in place. To test the model at all, Lockheed Martin then had to design an invisible ‘stealthy pole’ to mount the model utilising the same technology as the proposed combat aircraft. The results were once again astounding, and incredulous USAF officials were called in to witness and verify the data. The first opportunity to impress these officials almost resulted in embarrassment. When the radars were turned on, the reflections, while still very small by aircraft standards, were orders of magnitude larger than what the USAF officials had been led to expect. They could still clearly see a small radar return from where the model was mounted. 
While the Lockheed Martin engineers were trying to explain this discrepancy, a radio call came in from a technician downrange. He reported that a bird was perched on the ten-foot model. The quick reply was an order to blow the horn of the pickup truck the guy was sitting in. As the startled bird flew away, the radar reflection on the test scope disappeared. The very idea that a combat aircraft could be made so invisible as to hide behind a bird was an opportunity that couldn’t be passed up. Everything associated with the programme became classified at the highest levels. The programme was consequently transferred from DARPA to the USAF’s Special Projects Office. The word ‘stealth’ was forbidden to be mentioned in any unclassified document. And in April 1976, the Ford Administration gave Lockheed Martin the go-ahead for a full-scale aircraft. The Skunk Works was officially in the stealthly, low-observable flying platform business.
In 1974, when DARPA was becoming more and more interested in the idea that an aircraft, or a remotely-piloted vehicle, could be almost totally invisible to hostile RF-based sensors, the consequent competition led to the emergence of the Lockheed Martin-developed F-117 Nighthawk. But this is the story about the loser. After fielding some secondary studies regarding the possibility of a combat aircraft that could pass completely unseen by enemy radars, the XST (eXperimental Survivable Tactical) project was formally launched and DARPA went searching for OEMs to pursue the project’s goals. What DARPA was looking for in particular from the initial phase of the project was to answer two primary questions: 1) What were the signature limits that an aircraft would have to meet to be undetectable at an operational range from enemy sensors? 2) What could each aerospace OEM bring to the table when it came to designing and building an aircraft with the signature-levels established in question one?
Five major aerospace OEMs were approached to take part in the competition to build a scale-model concept that would demonstrate a substantial reduction in radar cross-section for a manned tactical air vehicle. Originally, Lockheed Martin was not even one of these companies. Word got around that the shadowy project was in the launch phase, and legendary Lockheed Skunk Works engineer Ben Rich went and persuaded the powers-that-be at the Pentagon to give him and his Skunk Works team a shot. He wanted in so badly that and he proposed competing for free, while all the other competitors would receive a paying contract for their R & D work. Nowadays, it is almost unbelievable to think that Lockheed Martin was not even on the US Department of Defense’s (DoD) list for the XST competition, but then again, the mid-1970s were a low time for Lockheed Martin. Having not produced a combat aircraft for more than a decade, their commercial aircraft division was also in deep public turmoil. The company was facing a possible fire-sale, after which its bones would be picked apart piece by piece. Still, what many in the DoD did not know was that the Skunk Works built the first stealthy aircraft, the A-12 Oxcart and SR-71 Blackbirds, although its low-observable features were still highly classified at that time. After starting with a half dozen competitors, the XST competition was narrowed down to consist of the aforementioned Lockheed Martin Skunk Works team, a Northrop Grumman team and a McDonnell Douglas team that would later also drop out of the competition. Skunk Works, being accustomed to working on highly classified projects, had every element of the XST team working together openly. Powerplant, flight controls, low-observables, aerodynamics and so on, were all at the same collaborative design table. Northrop Grumman , on the other hand, had built an almost firewall-like divide between the highly classified low-observable folks and the less sensitive aircraft systems and design folks. This mistake would result in a very inefficient design process that would cost them later on in the competition, and would once again uphold the management structure of Kelly Johnson as superior to all others in the classified aircraft development business.
As noted above, Team Skunk Works used a fairly obscure research paper from a Soviet scientist named Pyotr Ufimtsev to build a then cutting-edge computer programme called ‘ECHO-1’ that could predict effects of radar waves on an object. This resulted in the famed ‘Hopeless Diamond’ design, which was shaped like a rough-cut gem, and was fully faceted to reflect radar waves away from the transmitter/receiver from almost every direction with great efficiency. When it came to its radar signature, the ephemeral ‘Hopeless Diamond’ was downright exciting. But when it came to its aerodynamics, it was a messy conundrum to say the least. Which was something that Kelly Johnson, Ben Rich’s boss, was not too excited about. Meanwhile, the Northrop Grumman team had been working closely with Hughes Radar Systems Group since early on for its XST contender. Hughes, the gold standard purveyor of US-origin military sensors at the time, gave Northrop Grumman a deep theoretical understanding of how radars and infra-red sensors detect targets, and what shapes were hard to detect under various conditions. With this in mind, and without Lockheed’s novel ECHO-1 computer-based radar cross-section modelling programme, Northrop Grumman’s design moved forward, albeit clumsily. The aforementioned intense compartmentalization at Northrop Grumman, between the highly classified low-observables team, the aircraft systems team, and the airframe design team, was proving to be almost impossible to work through. Some individuals who were active in Northrop Grumman’s XST R & D effort at the time have since described this unsatisfactory arrangement as like trying to build the most advanced aircraft design in the world via playing a game of telephone. Nonetheless, leveraging their work with Hughes, the team began experimenting with different shapes and configurations, and in a learn-as-you-go creative process, a design began to materialise. DARPA, by this time having realised the promise of low-observables technology, had upgraded the project from a theoretical design study to one that would provide a flyable prototype. With this in mind, the name of the project changed to eXperimental Survivable Testbed. A winner-take-all “pole off” showdown, in which scale-models of both manufacturers unique designs would be evaluated mounted on a pole at a radar cross-section measurement range, was set for the summer of 1975. Only the winner would get the chance to see their exotic design take flight as a real-life technology demonstrator. Lockheed Martin’s ‘Hopeless Diamond’ was tweaked a bit to better resemble a plausible aircraft. The whole design was still made up of a series of flat panels, or diamond-like facets, but its rear trailing edge would be notched in instead of shaped like one-half of a diamond. It would also feature more highly swept wings, its inlets would be mounted behind both sides of the cockpit and the aircraft’s exhaust would exit through slits in the upper rear trailing edge of the fuselage to mask its infra-red signature. Northrop Grumman’s design looked more like a plausible flying machine, with the cockpit set far forward and a large air inlet, covered by a fine mesh grill, was set high atop the fuselage. It did not feature a complex array of facets like Lockheed Martin’s entry, rather it used smooth, broad surfaces and finely rounded edges to reflect radar energy, as well as a diamond-delta like wing platform. The aircraft’s exhausts were mounted deeply inward of the trailing edge, shrouded between the inward canted vertical tails. Both designs were very impressive, to say the least, having achieved massive reductions in overall RCS returns as well as dampening their theoretical infra-red signature to a large degree. Northrop Grumman, not having the luxury of Lockheed Martin’s ECHO-1 programme, and being handicapped by a fragmented design team, concentrated on making the aircraft as invisible as possible from its front and rear quadrants. Their thinking was that the most risk for a penetrating attack aircraft is posed when it is approaching and leaving the target area, so this is where their signature reduction goals were focussed. The Northrop Grumman team accomplished this goal very well, but when the aircraft design was viewed by radar from the side hemisphere, the aircraft’s RCS return spiked higher than Skunk Works’ Hopeless Diamond-based competitor. The Northrop Grumman XST’s less competitive side-on radar signature seemed to be more of a result of the stiff compartmentalisation within the Northrop Grumman design team than just the design philosophy alone, and it is possible that with some tweaks the Northrop Grumman XST offer would have featured a lower overall RCS than the Lockheed Martin contender. Northrop Grumman’s XST design was also already optimised to have a lower RCS over a broader range of radar frequencies. Additionally, the argument was made that Northrop Grumman’s design would have provided better aerodynamic performance and airframe adaptability, as well as lower overall production risk than Lockheed Martin’s wildly faceted design. In other words, there have been multiple voices, not just from within the Northrop Grumman camp, that think that the Northrop Grumman XST would have been a better choice than Lockheed Martin’s design, especially considering how immature the designs, and their team’s accompanying low-observable knowledge bases really were at the time. Still, regardless of these opinions, Lockheed Martin’s design best met the particular design goals laid out by the Pentagon, as such, there was no denying Lockheed Martin won the pole off. Interestingly, years after the XST competition concluded, Northrop Grumman’s non-faceted design philosophy seems much more ahead of its time than Lockheed Martin’s faceted approach, especially when you consider that second- and third-generation stealthy aircraft and unmanned systems have much more in common with Northrop Grumman’s XST design than Lockheed Martin’s XST design.
Still, both teams had solid manufacturing capabilities, competitive cost estimates, and aggressive timelines, so all things being fairly equal, Northrop Grumman’s slightly less stealthy pole model gave DARPA something to hang their final decision on, and the Skunk Works design was chosen for flight testing. This action would result in the ‘Have Blue’ technology demonstrators, then the ‘Senior Trend’ project, which resulted in the YF-117 and eventually the famous F-117 Nighthawk as we know it today. The loss from the XST competition did not mean the end for Northrop Grumman when it comes to low-observable aircraft. Quite the contrary, in fact. The team regrouped and learned from its mistakes over the next few years, and eventually fielded the absolutely game-changing platform known as the Battlefield Surveillance Aircraft Experimental, otherwise known as the ‘Tacit Blue’ technology demonstrator. This aircraft, aptly nicknamed ‘The Whale’, paved the way for Northrop Grumman to win the contract for developing the B-2 Spirit bomber, build the YF-23 Advanced Tactical Fighter contender, and even the Global Hawk and X-47B unmanned aircraft testbeds as we know them today. Strangely, the Tacit Blue concept would also indirectly lead to the Lockheed Martin RQ-170 Sentinel, and the General Atomics Avenger UAV. In fact, the rumoured Northrop Grumman RQ-180 is supposedly the final implementation of the concept that ‘Tacit Blue’ proved more than 30 years ago. Seeing how close the XST decision was, and taking into account just how handicapped Northrop Grumman was by having two compartmentalised teams working on one integrated aircraft, as well as not having the help of the groundbreaking ECHO-1 computer modelling programme, one has to wonder just how successful its stealthy aircraft could have been with more time to mature. 
In November 2013, Lockheed Martin announced that it, along with Aerojet Rocket­dyne, was developing the SR-72 reconnaissance aircraft that will be able to accelerate up to Mach 6, or 4,567mph (7,349kph) when powered by a twin turbofan-/dual ramjet based combined-cycle propulsion system. Lockheed Martin describes the SR-72—to be available by 2030—as being an intelligence, surveillance, reconnaissance, and strike platform, but its exact mission tasking/payload remains a secret. 
Ramjets forgo the big rotary compressors needed on turbofans and instead rely on their own forward motion to compress air. First, air is scooped into an inlet and compressed as it funnels into a diffuser. The diffuser also slows the air to subsonic speeds for easier combustion. From there, air and fuel are fed into a combustion chamber and ignited. Finally, an exhaust nozzle accelerates the resulting burst of hot, expanding air, producing massive thrust. Turbofans can take an aircraft from runway launch to about Mach 3; speeds faster than that require an air-breathing ramjet, which compresses high-speed air for combustion, but which typically begins operating at about Mach 4. To bridge the gap, engineers of Aerojet Rocket­dyne are developing a hybrid engine that can operate in three modes. The aircraft will accelerate to about Mach 3 under turbofan power, then switch to ramjet power to take it to about Mach 5, and then switch again to scramjet mode, which uses supersonic air for combustion. Aerodynamic friction at speeds exceeding Mach 5 will heat an aircraft’s exterior to 2,000 degrees Celsius. At that point, conventional steel airframes will melt. Hence, Lockheed Martin’s engineers are looking at composites—the same kinds of high-performance carbon, ceramic, and metal mixes used for the nosecones of ICBMs, SLBMs and space shuttles. Every joint and seam of the airframe must be sealed. Any air-leak at hypersonic speed, and the in-rushing heat would cause the aircraft to collapse. (That’s what had doomed the space shuttle Columbia). The stresses on an aircraft shift as it travels through subsonic, supersonic, and hyper­sonic speeds. For instance, when an aircraft is accelerating through subsonic flight, the centre-of-lift moves toward the back of the aircraft. But once the aircraft hits hypersonic speeds, drag on the aircraft’s leading egdes cause the centre-of-lift to move forward again. If the centre-of-lift gets too close to the centre-of-gravity it can cause dangerous instability. The SR-72’s shape must tolerate these changes, and more, to keep the aircraft from tearing apart. 
However, what remains unanswered till this day is why would Lockheed Martin’s Skunk Works and Aerojet Rocket­dyne spend exorbitant amounts of R & D funds on the SR-72 when they have already developed hypersonic aircraft like the SR-75 Penetrator, which uses pulse detonation wave engines (PDWE) and an aero-thermodynamic airframe design. On a hypersonic vehicle, thermal management is very critical, the cooling capacity of the fuel must be used carefully and efficiently, or else the range and endurance of the aircraft will be limited by heating rather than the actual fuel tank capacity. So how does the SR-75 reach such hypersonic speeds? Choosing the right type of fuel is crucial to the success of the SR-75. Because various sections of the craft will reach cruising-speed temperatures, its fuel must both provide energy for the PDWE engines and also act as a structural coolant extracting destructive heat from the airframe’s surface. At hypersonic speeds, even exotic kerosene such as the special high-flashpoint JP-7 fuel used by the SR-71 Blackbird can’t absorb enough heat. The only plausible solution therefore is cryogenic fuel. The best possibilities are methane and hydrogen. Liquid hydrogen provides more than three times as much energy and absorbs six times more heat per pound than any other fuel. The downfall is its low density, which means larger fuel tanks, a larger airframe and more drag. 
While liquid hydrogen is the fuel of choice for space launch vehicles that accelerate quickly out of the atmosphere, studies have shown that liquid methane is better for an aircraft cruising at Mach 5 to Mach 7. Methane is widely available, provides more energy than jet-fuels, and can absorb five times as much heat as kerosene. Compared with liquid hydrogen, it is also three times denser and easier to handle. So, at regular speeds, the SR-75 is powered by traditional turbofans built into the lower fuselage. Once it hits supersonic speed, the PDWE takes over. A PDWE works by sending liquid methane or liquid hydrogen into the engine. The fuel mist is then ignited. This detonation is made inside a specially designed chamber and occurs when the aircraft is travelling at supersonic speeds. At such speeds, a ‘thrust wall’ is created. This is when the aircraft is travelling so fast, air is pushed near the nose that creates a ‘wall’. When the detonation occurs, the aircraft’s thrust-wall is pushed forward, and this is repeated numerous times to propel the aircraft forward. The consequent jet stream looks like ‘donuts-on-a-rope’.
There is also work now underway in the US, France and Japan to develop pulse detonation turbines for higher efficiency power generation. Pratt & Whitney is developing a new combustor for turbofans that uses shockwaves for more efficient combustion through a process known as continuous detonation. GE Aero Engines has also been working on pulse detonation. When fitted to a conventional turbofan, CDWE technology offers to transform overall engine performance and simplify its design by using detonation waves to combust the fuel and oxidizer mixture. Theoretically, this system can operate from subsonic up to a hypersonic flight-speeds of roughly Mach 5, with higher efficiency than existing turbofans. This is because a detonation-wave rapidly compresses the mixture and adds heat at constant volume, thereby providing a thermal efficiency improvement of approximately 25%.
The SR-75’s airframe may well incorporate stealth technology, but it does not really require it should its mission simply involve high-altitude reconnaissance. Hypersonic aircraft are much harder to shoot down than a ballistic missile. Although a hypersonic aircraft isn’t very manoeuvrable, its velocity is such that even a small turn puts it miles away from a SAM’s projected (via the proportional navigation technique) interception point. 
The UK’s Ministry of Defence would have you believe that nothing untoward occurred at Boscombe Down, Wiltshire, on the night of September 26, 1994. But something sinister did happen at the airfield that night. The fact that the incident involved the US’ most highly-classified black project aircraft helps to explain the scale (and to some extent the subtlety) of the disinformation campaign which ensured. The story had begun to unfold on that windswept night as the aircraft began its takeoff run along Runway 23. Whatever happened in the few seconds following application of takeoff power was sufficiently catastrophic for the two-man USAF aircrew to abort departure immediately. Military controllers at the London Air Traffic Control Centre (LATCC) were alerted either directly or indirectly to the fact that a serious incident had occurred, and that the runway was blocked. Later that night, the stranded aircraft was seen by at least one witness near the eastern end of Boscombe Down’s Runway 23. A tarpaulin-covered frame had already been erected above the aircraft’s forward section, around which were a number of emergency-response vehicles. The rear section appeared unnaturally elevated by virtue of an apparent nose-wheel collapse, the only clearly definable characteristic being inward canting twin fins. Early the next day, one of four British Army Air Corps Agusta A-109 helicopters transited to Boscombe Down from Bournemouth-Hurn. All four A-109s were then exclusively operated by the Special Air Service (SAS), which has a base at Poole, near Hurn. Is it possible that a covert sealing-off operation was set in motion? It has also been suggested that at least one RAF Chinook was scrambled from Odiham to Boscombe Down late that night for just that purpose. The sighting was followed that same evening by a separate sighting of a grey USAF C-5 Galaxy on the ground at Boscombe Down. The aircraft had been monitored on airband radio as it cancelled its flight-plan to the USAF European HQ at Ramstein in Germany, and requested a diversion to Boscombe Down. On arrival, the C-5 parked on the ramp outside the DRA/DTEO hangar. It is likely that the incident aircraft was normally housed in one of Boscombe’s hardened air shelters (HAS). However, in the aftermath of the incident the first priority would have been to move the aircraft under cover to a place where the C-5 could undertake a loading or unloading procedure with minimum risk. With the taxiways leading to the shelters unable to accommodate an aircraft as large as the C-5, the most logical option would indeed have been to move the aircraft to the DRA/DTEO hangar. Despite these precautions, an unidentifiable tarpaulin-covered object was seen to be loaded into the C-5. This flight-plan (evidence of which has since disappeared) used a non-standard callsign of Lanc 18, but more noteworthy was its destination which was listed as KPMD. This is the ICAO airfield designator for Palmdale, California, better known as Air Force Plant 42 and home to the assembly lines of both the Lockheed Martin and Northrop Grumman Electronic Systems and Integration Division. The Boscombe Down incident aircraft is designated as the ASTRA, was originally referred to as AV-6 (Air Vehicle Six, its construction number), and was allocated USAF serial 90-2414. It routinely used frequencies in the 500 to 510 mHz range (highly unusual and beyond the tuning range of standard UHF scanner radios) and was operating with the callsign Blackbuck 11. It had been operating in tandem with at least one other aircraft. ASTRA is an acronym standing for Advanced Stealth Technology Reconnaissance Aircraft. The prime contractor was Northrop, with McDonnell Douglas (MDC) involvement, and the aircraft is directly related to the YF-23 (unsuccessful ATF contender). No doubt most controversial of all, the ASTRA is believed to be the Mach 5+ hypersonic tactical reconnaissance aircraft, most commonly referred to until now as Aurora. This, along with its YF-23 lineage, will be a major surprise to those who either denied the existence of a manned hypersonic project, or assumed it to be a product of Lockheed Skunk Works. Lockheed Martin has consistently denied involvement in a hypersonic project but in June 1991, Northrop Grumman had quietly set up its own version of the ‘Skunk Works’, called the Advanced Technology and Design Center, to pursue what it acknowledged to be both manned and unmanned ‘black project’ developments. It also began testing a distributed-exhaust/pressurised wing concept. The technology was said to be related to at least one US Dept of Defense ‘black aircraft’ project. It may be that the ASTRA is actually the project involved (rather than a special forces transport type as suggested), given that the concept involves using bleed-air from the engines and pumping it through the wings’ upper surfaces, and given that the YF-23 had bleed-air doors in the wing upper surface near the leading-edge wing-root, the purpose of which was claimed to be suction removal of the boundary layer from the underwing air intake.
The first evidence of flights by hypersonic vehicles emerged in 1989, with eyewitness reports of the characteristic ‘doughnuts on a rope’ contrails produced by the pulsing motion of a PDWE, which detonated the fuel in the jetpipe and expelled some of the gases created through inlets at the forward end of the pipe. At this early stage in flight-testing there were probably no more than two prototypes in the programme, with 1987 fiscal serials corresponding to the original project go-ahead. In February 1985 (just after Tacit Blue was grounded), there was an inadvertent leak in the US federal budget regarding Aurora funding, which showed US$80 million being requested for FY 1986, rising to a massive US$2.2 billion in 1987, the same year in which the YF-23 prototypes were funded. If the ASTRA was nested in Aurora, or indeed came to be the new name used when Aurora’s cover had been blown, then the funding request is consistent with the funding of one or two prototypes in 1987, which would not have been completed and flown until 1989. The greater proportion of hypersonic aircraft activity took place after February 1992, with night sightings of unusual activity at Beale AFB, and loud anomalous noises described as similar to sustained artillery firing, likely to have been caused by ground runnings of the PDWE. The aircraft were only present at Beale AFB for a matter of months, probably for pre-operational familiarisation. In addition, it is known that a security policeman at Beale AFB reported seeing a YF-23-like aircraft hangared there (in one of the SR-71 sheds) in nearly 1992. There was apparently little attempt to disguise the aircraft's presence, because it was surrounded by personnel wearing blue MDC overalls. The YF-23 prototypes themselves had ceased flying in late December 1990, pending the ATF contract award in April 1991.
In August 1989, Chris Gibson, a Scottish oil-exploration engineer and, at the time, a member of the British Royal Observer Corps (ROC), was working on the oil rig Galveston Key in the North Sea when he noticed an aircraft in the shape of a pure isoceles triangle refuelling from a USAF KC-135 Stratotanker alongside two USAF F-111s. The unknown aircraft, cruising in a formation northward through Air-to-Air Refuelling Area (AARA) 6A, is what people have come to believe, was the mysterious AV-6 Astra, which used to use the RAF airbase at Machrihanish, Strathclyde—with its three-mile-long runway—as a staging post for Mach 4, 200,000 feet-high dashes home across the North Sea. The aircraft has also been spotted across the US, in Norway and the Netherlands, often to the accompaniment of a deafening sonic boom and its characteristic ‘donuts-on-a-string’ contrail. Below, Chris Gibson explains precisely what happened, as well as giving an insight into himself.
“I welcome any questions on my North Sea sighting, as I am of the opinion that too much is taken at face value in the black aircraft snark hunt. I think that the snark hunt has degenerated into an exercise in regurgitating the same old stories with little or no new research being done. A bit about me. I work as a drilling technologist for a major oil field service company. I hold an Honours degree in geology, with some engineering, geophysics and chemistry thrown in. I also did a post graduate course in systems analysis, I was a member of the ROC for 13 years and was a member of the ROC’s aicraft recognition team for 12 of those years. In this field I was considered to be an expert and produced an aircraft recognition manual for the ROC. Some will obviously know the sighting story, but I will fill you in on what happened from my point of view. I was working in the indefatigable field on the jack-up rig ‘Galvestion Key’ in August 1989. My colleague, Graeme Winton, went out on deck but returned immediately. He told me to “have a look at this.” We went outside and Graeme pointed skywards. I had been at university with Graeme and he knew of my interest in aircraft. As far as Graeme was concerned it was a formation of aircraft and he reckoned I’d be interested. I looked up, saw the tanker and the F-111s, but was amazed to see the triangle. I am trained in instant recognition, but this triangle had me stopped dead. My first thought was that it was another F-111, but there was no gaps, it was too long and it didn’t look like one. My next thought was that it was an F-117, as the highly swept planform of the F-117 had just been made public. Again the triangle was too long and had no gaps. After considering and rejecting a Mirage IV, I was totally out of ideas. Here was an aircraft, flying over head, not too high and not particularly fast. A recognition gift and I was clueless. This was a new experience. Graeme asked me what was going on. I watched as the formation flew overhead and told him that the big one was a KC-135 Stratotanker, the two on the left were F-111s and that I didn’t know what the fourth aircraft was. Graeme said “I thought you were an expert?” I said “I am.” To which Graeme replied “Some expert.” It was obvious to me that this aircraft was something ‘dodgy’. I watched the formation for a minute or two and went back inside with Graeme. At the time I was writing the aircraft recognition manual and had a Danish Luftmelderkorpset Flykendingsbog in my briefcase. This is probably the best aircraft recognition book ever produced. I looked through it, but nothing matched. I then sketched what I had seen and sent this to Peter Edwards, who was a Group Officer in the ROC and was also on the recognition team. We discussed what to do about it but decided that if it was reported through official channels, it would be at best rubbished, at worst lead to trouble. Having signed the Official Secrets Act I didn’t want to jeopardise my position in the recognition team, so I kept my mouth shut. I told other members of the recognition team in the hope that they could shed some light on the subject. On returning home I had a look through my book collection. The only aircraft which came close to matching what I had seen was a Handley Page HP-115. It was not one of them. Whether this aircraft was a Aurora is debatable—my background precludes jumping to conclusions based on a single piece of evidence. I wrote to Bill Sweetman (Stealth expert) after being sent an illustration from Janes Defense Weekly, which matched what I had seen.” 
In an article titled: ‘Sightings and Engineers’ Dreams Taking to Skies as Black Aircraft’, written by Bill Scott, and published in Aviation Week & Space Technology on December 24, 1990, on page 42, paragraph 2 speaks of “well choreographed show-and-tell sessions given to selected members of the US Congress and key government officials”. At one such ‘dog and pony’ show held at Norton AFB on November 12, 1988, the second-generation ‘Aurora’ aircraft was put on display. This exhibit of various classified aircraft was arranged to garner further financial backing for special access or ‘black’ programmes. The second-generation Aurora looked very similar in appearance to the F-19, with the exception of the pilot and tail assembly. It also featured eight air-intakes instead of the four used on the manned F-19 version. A clear lineage of this specific aircraft type can now be identified.
Regarding the propulsion system used on the aircraft shown at Norton AFB, it featured hundreds of tiny fuel ejector holes located just aft of a ridge that ran laterally across the widest part of the aircraft. Looking from the side, it resembled a flattened football shape with a distinctive raised ridge or high-point that tapered back to the aft end. As for the external appearance, it looked like the entire aircraft was composed of black space shuttle heat-resistant tiles, which showed signs of scorched heat thermal erosion, due to the exotic propulsion system. The concept being, conventional turbofans would propel the craft to approximately Mach 3. At this point, the eight NACA ducts would close, providing for a smooth aerodynamic surface. Next, the craft would switch propulsion systems by turning off the turbofanss, and begin spraying a highly modified slush hydrogen fuel directly at the raised portion of the craft. By now, the craft, travelling in excess of Mach 3, would begin to glow in a very dull red colour at the leading edges and mid-section. Airflow over the vehicle at supersonic speeds caused a ‘wake separation’ to occur at the slight lateral ridge, and fuel injected into this superheated, highly compressed air-stream spontaneously combusted, expanding between the tapered ‘after-body’ of the craft, and the supersonic shock wave which separated at the ridge.
The TR-3B triangle-shaped nuclear-powered aerospace platform, built in the mid-1980s by Lockheed Martin and Teledyne Ryan, was developed under the Aurora programme—a top-secret, multi-tier developmental roadmap for advanced aerospace vehicles. The TR-3B’s outer coating is reactive to electrical stimulation and can change colour, reflectiveness, and radar absorptiveness. This is also the first US vehicle to use quasi-crystals in the vehicle’s skin. This polymer skin, when used in conjunction with the TR-3B’s ECM suite, can make the vehicle look like a small aircraft or a flying cylinder or even tricking radars into falsely detecting a variety of aircraft, no aircraft, or several aircraft at various locations. A circular, mercury-based plasma-filled accelerator ring called the Magnetic Field Disrupter (MFD) surrounds the rotatable crew compartment and is far ahead of any imaginable technology. The plasma is pressurized at 250,000 atmospheres at a temperature of 150 degrees Kelvin, and accelerated to 50,000 RPM to create a super-conductive plasma with the resulting gravity disruption. Sandia National Labs and Lawrence Livermore Labs co-developed the MFD, which generates a magnetic-vortex field that disrupts or neutralises the effects of gravity on mass within proximity by 89%. This is not anti-gravity, for anti-gravity provides a repulsive force that can be used for propulsion. The MFD creates a disruption of the Earth’s gravitational field upon the mass within the circular accelerator. The mass of the circular accelerator—and all mass within the accelerator, such as the crew capsule and the nuclear reactor—are reduced by almost 90%. This causes the effect of making a vehicle extremely light and able to outperform and outmanoeuvre (horizontally and vertically) any aircraft yet constructed. Except, of course, those ‘Unconventional Flying Objects’ (UFO) not of Earthly origin. The TR-3B’s aerodynamic performance is limited only the stresses that its human aircrew can endure. Which is a lot, really, considering along with the 89% reduction in mass, the G forces are also reduced by 89%. The TR-3B’s aircrew can therefore comfortably sustain up to 40Gs which, when reduced by 89%, will be about 4.2 Gs. 
By using electromagnetic forces to contain rotating systems, it is possible for the masses to reach relativistic velocities. Thus, a comparatively small amount of matter, if dense enough and moving fast enough, can produce usable gravitational effects. The requirement for a dense material moving at relativistic speeds would explain the use of Mercury plasma (heavy ions). If the plasma really spins at 50,000 RPM and the Mercury ions are also moving in a tight pitched spiral, then the individual ions would be moving probably hundreds, perhaps thousands of times faster than the bulk plasma spin, in order to execute their ‘screw thread’ motions. It is quite conceivable that the ions could be accelerated to relativistic speeds in this manner. For this to happen, it is necessary to strip the free electrons from the plasma, making a positively charged plasma, since the free electrons would tend to counter-rotate and reduce the efficiency of the MFD. One of Dr Albert Einstein’s postulates of general relativity (GR) says that gravitational mass and inertial mass are equivalent. This is consistent with claims of the inertial mass within the mercury-based plasma ring also being reduced by 89%. This also explains why the TR-3B is triange-shaped. Since it still requires conventional thrusters for propulsion, the thrusters would need to be located outside of the ‘mass reduction zone’ or else the mass of the thrusters reaction material would also be reduced, making them terribly inefficient. Since it requires a minimum of three legs to have a stable stool, it follows that one would need a minimum of three thrusters to have a stable aerospace platform. Three thrusters, located outside of the plasma ring, plus appropriate structural support, would naturally lead to a triangular shape for the vehicle. 
The nuclear reactor heats the liquid hydrogen and injects liquid oxygen in the supersonic thruster nozzles (developed by Rockwell), so that the hydrogen burns concurrently in the liquid oxygen afterburner. This multi-mode propulsion system can operate in the atmosphere, with thrust being provided by the nuclear reactor, in the upper atmosphere, with hydrogen propulsion; and in orbit, with the combined hydrogen/oxygen propulsion. Directional propulsion is thus provided by the three multi-mode thrusters mounted at each bottom corner of the triangular platform. The TR-3B is a sub-Mach 9 vehicle until it reaches altitudes above 100,000 feet. It is 600 feet across, which would make it similar in size to an aircraft carrier. At least three prototypes were built, each measuring about 60 metres across, and the operational model is about 180 metres (600 feet) across. The TR-3B can thus be used as a reconnaissance platform with an indefinite loiter time.