Boeing's X-48B prototype

In cooperation with NASA and the U.S. Air Force Research Laboratory, Boeing [NYSE: BA] Phantom Works soon will begin ground testing of its X-48B Blended Wing Body (BWB) concept in preparation for flight testing early next year.
The X-48B ground and flight testing will take place at NASA's Dryden Flight Research Center at Edwards Air Force Base in California, where two high-fidelity 21-foot wingspan prototypes have been delivered.
The prototypes were produced to explore and validate the structural, aerodynamic and operational advantages of the BWB concept. They were designated the "X-48B" by the U.S. Air Force based on its interest in the design's potential as a future military aircraft.
"Earlier wind-tunnel testing and the upcoming flight testing are focused on learning more about the BWB's low-speed flight-control characteristics, especially during takeoffs and landings," said Norm Princen, Boeing Phantom Works chief engineer for the X-48B program. "Knowing how accurately our models predict these characteristics is an important step in the further development of this concept."
X-48B Ship 1 completed extensive wind tunnel testing at the Old Dominion University NASA Langley Full-Scale Tunnel this summer before being shipped to NASA Dryden as a backup to Ship 2, which will be used for flight testing early next year.
In preparation for first flight, the X-48B Ship 2 will undergo ground testing to validate its engine- and fuel-system integrity, battery endurance, telemetry link communication, flight-control software, and low- and high-speed taxiing characteristics.
The X-48B's three turbojet engines will allow the 500-pound, composite-skinned, 21-foot wingspan prototype to fly up to 120 knots and 10,000 feet in altitude during flight testing.
The X-48B research project is led by Phantom Works, Boeing's advanced R&D unit chartered to provide innovative technology and system solutions to meet future aerospace needs. Cranfield Aerospace, Ltd., in the United Kingdom built the two X-48B prototypes for Phantom Works in accordance with Boeing requirements and specifications. NASA's participation in the project is focused on fundamental, edge-of-the-envelope flight dynamics and structural concepts of the BWB, while AFRL is focused on the BWB's potential as a flexible, long-range, high-capacity military aircraft.

The SR 71:Incoming...

 
A NASA SR 71B variant


3 SR 71s at Dryden Flight Research Centre


An SR 71 inflight with a F/A 18 Chaser

December 1964,
     US government officials acknowledged the existence of a top-secret spy plane so technologically advanced, it could fly to the edge of space and cross the continent in an hour flat. The needle-shaped aircraft was powered by massive jet engines that propelled it at 35 miles a minute. Constructed with imported Russian titanium and painted midnight black, it had a sleek, sinister appearance straight out of science fiction.
     It was the SR 71 which was to serve the USAF for more than 30 years
     The Lockheed SR-71 was an advanced, long-range, Mach 3 strategic reconnaissance aircraft developed from the Lockheed YF-12A and A-12 aircraft by the Lockheed Skunk Works. The SR-71 was unofficially named the Blackbird; its crews often called it the Sled, or the Habu ("snake"). The SR-71 line was in service from 1964 to 1998.The SR-71 was one of the first aircraft to be shaped to reduce radar cross section. However, the aircraft was not stealthy and still had a large enough radar signature to be tracked by contemporary systems. The aircraft's defense was its high speed and operating altitude; if a surface-to-air missile launch was detected, the standard evasive action was to simply accelerate.

The SR 71:Cutting Edge

The SR 71 Cockpit

     The aircraft remains a technological marvel. Practically every area of design required new approaches or breakthroughs in technology. To withstand high temperatures generated by friction in the upper atmosphere during sustained Mach 3 flight, the Blackbird required an array of specially developed materials including high temperature fuel, sealants, lubricants, wiring and other components. Ninety-three percent of the Blackbird's airframe consists of titanium alloy that allows the aircraft to operate in a regime where temperatures range from 450 degrees Fahrenheit at its aft midsection to 950 degrees Fahrenheit near the engine exhaust. The cockpit canopy, made of special heat resistant glass, must withstand surface temperatures as high as 640 degrees Fahrenheit.
     Two Pratt & Whitney J58 turbojet engines with afterburners, each supplying more than 35,000 pounds of thrust, are housed in wing nacelles with diameters larger than the fuselage itself. Virtually every part of these complex powerplants had to be fabricated from special materials to meet the demands of triple-sonic flight. A translating (moveable) spike in each inlet controls airflow, retracting at speeds above Mach 1.6 to capture more air for the engines.

Astro-Inertial Navigation System (ANS)
    Blackbird precision navigation requirements for route accuracy, sensor pointing and target tracking preceded the development and fielding of GPS (the Global Position System and its family of position determining satellites).
    Nortronics, the electronics development organization of Northrop, had extensive astro-inertial experience, having provided an earlier generation system for the USAF Snark missile. With this background, Nortronics developed the Astro-Inertial Navigation System for the AGM-87 Skybolt missile, which was to be carried and launched from B-52H bombers. When the Skybolt Program was cancelled in December 1962, the assets Nortronics developed for the Skybolt Program were ordered to be adapted for the Blackbird program.
The ANS primary alignment was done on the ground and was time consuming, but brought the inertial components to a high degree of level and accuracy for the start of a mission. A "blue light" source star tracker, which could detect and find stars during day or night, would then continuously track stars selected from the system's digital computer ephemeris as the changing aircraft position would bring them into view. Originally equipped with data on 56 selected stars, the system would correct inertial orientation errors with celestial observations. The resulting leveling accuracies obtained limited accelerometer errors and/or position growth.
Rapid ground alignments and air start abilities were later developed and added to the ANS. Attitude and position inputs to on-board systems and flight controls included the Mission Data Recorder, Auto-Nav steering between loaded destination points, automatic pointing and/or control of cameras at control points and optical or SLR sighting of fix points (this mission data being tape loaded into the ANS prior to takeoff).
     Cooling in the Blackbird at a Mach 3.0+ cruising environment was a serious development challenge resolved by Lockheed and Nortronics engineers during the early test phases. The ANS became a highly reliable and accurate self-contained navigation system.

Sensors and Payloads
     Original capabilities for the SR-71 included optical/infrared imagery systems, side-looking radar (SLR), electronic intelligence (ELINT) gathering systems, defensive systems (for countering missile and airborne fighter threats) and recorders for SLR, ELINT and maintenance data.
     Imagery systems used on the Blackbird were diverse. At the simple end of the spectrum, SR-71s were equipped with a Fairchild tracking camera of modest resolution and a HRB Singer infrared-tracking IR camera, both of which ran during the entire mission to document where the aircraft flew and answer any post-flight "political" charges of overflight. Further advances included equipping Blackbirds with two of ITEK's Operational Objective Cameras (OOC) that provided stereo imagery left and right of the flight track or an ITEK Optical Bar Camera (OBC) that replaced the OOCs and was carried in the nose in place of the SLR. The ultimate advance in imagery was the HYCON Technical Objective Camera (TEOC) that could look straight down or up to 45 degrees left or right of centerline. SR-71s were equipped with two of them, each with a six-inch resolution and the ability to show such details as the painted lines in parking lots from an altitude of 83,000 feet. In the later years of the SR-71 operation, usage of the infrared camera was discontinued.
     Side-looking radar, built by Goodyear Aerospace in Arizona, was carried in the removable nose section (which could be loaded with the SLR antenna in the maintenance shop before installation on the Blackbird). It was eventually replaced by Loral's Advanced Synthetic Aperture Radar System (ASARS-1) and built and supported by Goodyear. Both the first SLR and ASARS-1 were ground mapping imaging systems and could collect data in fixed swaths left or right of centerline or from a spot location where higher resolution was desired. As an example, in passing abeam of an open door aircraft hangar, ASARS-1 could provide meaningful data on the hangar's contents.
     ELINT gathering systems, called the Electro Magnetic Reconnaissance System (EMR) built by AIL could be carried in both the left and right chine bays to provide a wide view of the electronic signal fields the Blackbird was flying through. Computer loaded instructions looked for items of special Intelligence Interest.
     Defensive systems, built by several leading electronic countermeasures (ECM) companies would be loaded for a particular mission to match the threat environment expected for that mission. They, their warning and active electronic capabilities, and the Blackbird's ability to accelerate and climb when under attack resulted in the SR-71's long and proven survival track record.
     Recording systems captured SLR phase shift history data (for ground correlation after landing), ELINT-gathered data, and Maintenance Data Recorder (MDR) information for post flight ground analysis of the aircraft and its systems' overall health
[Wikipedia]

The SR 71:Before and after Take Off

 
A close up of the SR 71 cockpit taken from a KC 135

 The SR 71 refuelling in midflight from a KC 135 tanker

Picture Courtesy: NASA SR 71 image gallery

When the aircraft has completed its pre-flight checks, it will pull out of the barn and move onto the runway. From there, the SR-71 will perform engine run-ups and then the ground crew will pull the chocks. The SR-71 will start to roll down the runway slowly and then accelerate rather rapidly after the afterburner is lit. The feel has been described as a freight train moving down hill. At approximately 230 knots, the airplane lifts off of the runway.
Before any flight, the crew would receive a high protein, low residue meal of steak and eggs. After that, the crew would have a brief medical examination. Following the examination, the crew would get suited up and the Physiological Support Division would check the suit integration.Since the SR 71 operates at a maximum speed of Mach 3.3 at an altitude more than sixteen miles, or 25,908 m (85,000 ft), above the earth,the crew have to wear pressure suits similar to those worn by astronauts. These suits were required to protect the crew in the event of sudden cabin pressure loss while at operating altitudes The suits that the SR-71 crew members wear are identical to those worn by the crews on the space shuttle. After the crew is suited up, they breathe in pure oxygen and filter out any other gas from their body before takeoff. Then the crew would go out to the van for the trip to the barn where the SR-71 is housed. When the crew arrives at the hangar, they shake hands with the buddy crew and then shake hands with each other before entering the aircraft. The pilot and his RSO enter the aircraft and the pilot will tell the ground crew to start the engines. The pilot will then move up the throttle about half way. TEB is shot into the tailpipe of the aircraft and a green flash is seen out of the ejector. Then there are about 25 minutes of pre-flight checks before takeoff.

FUEL
In order for the SR-71 to fly the worldwide missions, it has a special fleet of modified KC-135Q tankers for refueling. SR-71s run on JP-7 fuel, that fills the six large tanks in the fuselage. The component parts of the Blackbird fit very loosely together to allow for expansion at high temperatures. At rest on the ground, fuel leaks out constantly, since the tanks in the fuselage and wings only seal at operating temperatures. There is little danger of fire since the JP-7 fuel is very stable with an extremely high flash point. Originally developed for the A-12 Oxcart plane in the late 1950s, the JP-7 jet fuel had a relatively high flash point (60 °C) to cope with the heat. In fact, the fuel was used as a coolant and hydraulic fluid in the aircraft before being burned. The fuel also contained fluorocarbons to increase its lubricity, an oxidizing agent to enable it to burn in the engines, and even a cesium compound, A-50, which disguised the exhaust's radar signature. As a result, JP-7 was claimed to be more expensive than single malt Scotch whisky.JP-7 is very slippery and extremely difficult to light in any conventional way. The slipperiness was a disadvantage on the ground, since the aircraft leaked fuel when not flying, but at least JP-7 was not a fire hazard. When the engines of the aircraft were started, puffs of triethylborane (TEB), which ignites on contact with air, were injected into the engines to produce temperatures high enough to initially ignite the JP-7.
After the SR-71 takes off, it has a rendezvous with a KC-135Q tanker seven minutes later. The SR-71 takes off with a very light fuel load and after this refueling, the plane can fly up to 2,500 miles without refueling. The aircraft then accelerates to speed and altitude which is about Mach 3.2 at 85,000 feet. The SR-71 then takes photos of the targeted area and has another rendezvous with a tanker before returning home. After the flight, the photography equipment is removed and is analyzed immediately. The photography is then sent to the CIA, or whomever needs this valuable intelligence.

The SR 71:Heatshock Stealth Armour

 The SR 71:Engine flame and turbulence as it attains Mach velocity

 A Front view of the SR 71 showing Chines and Vert.Stabilizers

     THE AIRFRAME of the SR-71 is very unique. To withstand the friction-generated heat at Mach 3+, over 90 percent of the airframe is made of titanium composite. Also to withstand heat, the main gear tires have been impregnated with aluminum and are filled with nitrogen.The airframe was made of titanium obtained from the USSR during the height of the Cold War. Lockheed used all possible guises to prevent the Soviet government from knowing what the titanium was to be used for. In order to keep the costs under control, they used a more easily worked alloy of titanium which softened at a lower temperature. Finished aircraft were painted a dark blue (almost black) to increase the emission of internal heat (since fuel was used as a heat sink for avionics cooling) and to act as camouflage against the sky.Before the Blackbird, titanium could only be found in aircraft in high-temperature exhaust fairings and other small parts directly related to supporting, cooling, or shaping high-temperature areas. The decision to build the Blackbird's structure using 85% titanium and 15% composite materials was a first in the airplane industry. The advances made by Lockheed in learning to deal with this material have been used in subsequent high-speed aircraft such as most modern fighters.
Studies of the aircraft's titanium skin revealed the metal was actually growing stronger over time due to the intense heating caused by aerodynamic friction, a process similar to annealing.Major portions of the upper and lower inboard wing skin of the SR-71 were actually corrugated, not smooth. The thermal expansion stresses of a smooth skin would have resulted in the aircraft skin splitting or curling. By making the surface corrugated, the skin was allowed to expand vertically as well as horizontally without overstressing, which also increased longitudinal strength.
Due to the great temperature changes in flight, the fuselage panels did not fit perfectly on the ground and were essentially loose. Proper alignment was only achieved when the airframe warmed up due to the air resistance at high speeds, causing the airframe to expand several inches. Because of this, and the lack of a fuel sealing system that could handle the extreme temperatures, the aircraft would leak its JP-7 jet fuel onto the runway before it took off. The aircraft would quickly make a short sprint, meant to warm up the airframe, and was then air-to-air refueled before departing on its mission. Cooling was carried out by cycling fuel behind the titanium surfaces at the front of the wings (chines). Nonetheless, once the plane landed no one could approach it for some time as its canopy was still hotter than 300 °C. Non-fibrous asbestos was also used, as in non-ceramic automotive brakes, due to its high heat tolerance

The Stealth Element
     The aircraft was designed to minimize the radar cross-section and as such, the SR-71 was an early attempt at stealth design.There were a number of features in the SR-71 that were designed to reduce its radar signature.Lockheed hoped to achieve this by carefully shaping the airframe to reflect as little transmitted radar energy (radio waves) as possible, and by application of special paint designed to absorb, rather than reflect, those waves. This treatment became one of the first applications of stealth technology, but it never completely met the design goals. The first studies in radar stealth seemed to indicate that a shape with flattened, tapering sides would reflect most radar away from the place where the radar beams originated. To this end the radar engineers suggested adding chines* to the design and canting the vertical control surfaces inward. The plane also used special radar-absorbing materials which were incorporated into sawtooth shaped sections of the skin of the aircraft, as well as cesium-based fuel additives to reduce the exhaust plumes' visibility on radar. However, the radar signature aspects of the SR-71 design did not take into account the extremely hot engine exhaust and the particles in the hot exhaust reflect radar extremely well. Ironically, the SR-71 was one of the largest targets on the FAA (Federal Aviation Administration) long range radars, which were able to track the plane at several hundred miles.Despite Lockheed's best efforts, it was still easy to track by radar (and had a huge infrared signature when cruising at Mach 3+). It was visible on air traffic control radar for hundreds of miles, even when not using its transponder**.This fact is further corroborated by the fact that missiles were fired at them quite often after they were detected on radar.The SR-71 was the first operational aircraft designed around a stealthy shape and materials. The most visible marks of its low radar cross section (RCS) are its inwardly-canted vertical stabilizers and the fuselage chines. Comparably, a plane of the SR-71's size should generate a radar image the size of a flying barn, but its actual return is more like that of a single door. Though with a much smaller RCS than expected for a plane of its size, it was still easily detected, because the exhaust stream would return its own radar signature (even though the special cesium compound was added to the fuel to reduce this signature). Furthermore, this is no comparison to the later F-117, whose RCS is on the order of a small ball bearing
[*Chine is an aerodynamic term referring to the intersection of the upper and lower fuselage surfaces of the SR-71 Blackbird which form a 'lip' around the forward fuselage of the aircraft. These chines generate lift-bearing vortices at high angles of attack and reduce the aircraft's lateral radar signature]
[**The type of transponder occurs in friend or foe identification systems in military aviation and in air traffic control secondary surveillance radar (beacon radar) systems for general aviation]
     The red stripes found on some SR-71s are there to prevent maintenance workers from damaging the skin of the aircraft. The curved skin near the center of the fuselage is thin and delicate. There is no support underneath with exception of the structural ribs, which are spaced several feet apart.

The SR 71:Here to Stay....Why?

 
The SR 71 in reconnaisance flight

 Very High Service ceiling and supersonic capability favours Synoptic Coverage

     In the 1970s the SR-71 was placed under closer congressional scrutiny and with budget concerns the program was soon under attack. Both Congress and the USAF sought to focus on newer projects like the B-1 Lancer and upgrades to the B-52 Stratofortress (whose replacement was being developed). While the development and construction of reconnaissance satellites was costly their upkeep was less than that of the nine SR-71s then in service. The SR-71 had never gathered significant supporters within the Air Force making it an easy target for cost conscious politicians. Also, parts were no longer being manufactured for the aircraft, so other airframes had to be cannibalized in order to keep the fleet airworthy. The Air Force saw the SR-71 as a bargaining chip which could be sacrificed to insure the survival of other priorities. A general misunderstanding of the nature of aerial reconnaissance and a lack of knowledge about the SR-71 in particular (due to its early secretive development and usage) was used by its detractors to discredit the aircraft. In 1988 Congress was convinced to allocate $160,000 to keep six SR-71s (along with a trainer model) in flyable storage that would allow the fleet to become airborne within 60 days. The USAF refused to spend the money. The decision to release the SR-71 from active duty came in 1989. Funds were redirected to the financially troubled B-1 Lancer and B-2 Spirit programs. Four months after the plane's retirement, General Norman Schwarzkopf, Jr. was told that reconnaissance which the SR-71 could have provided was unavailable during Operation Desert Storm.After Desert Storm tactical commanders stressed that they were not getting the timely intel they needed. It's also obvious that there was no "other system" waiting in the wings. In 1995 Congress ordered the reactivation of some of the existing SR-71s.
     The SR-71 can fly within hours of notification Its flight path can, if necessary, be changed in a short time. There is no advance warning of its coming. Flying at cruise speed and altitude, it moves along a flight path unknown to those being surveyed. It collects data and is gone before assets on the ground can be moved or hidden, before those surveyed realize what happened; that is, until they feel the punch of the plane’s sonic boom. The SR-71 is the only reconnaissance platform that can penetrate hostile territory along an unpredictable flight path, accomplish wide-area synoptic coverage and survive. Very simply, the SR-71 can collect intelligence data that no other reconnaissance system can, intelligence data that, as we have seen, is otherwise unobtainable.
     After the cruise missile attacks on terrorist bases in Afghanistan in 1999, there was a problem. Bomb damage assessment (BDA) on the targets was not available due to limitations of the U.S. resources in providing information.The first reason for lack of BDA was that it was nighttime in the region; later, it was because of weather. To date the only BDA the USAF had was some low-resolution satellite photos, and those were obtained days after the attack. In other words, for days the USAF were blind as bats, without knowledge of what damage their missiles had done. Even then, the results were hardly impressive.Fortunately, in this instance, the delay in obtaining intelligence was not that critical. In another scenario, such a delay could prove catastrophic.
     The SR-71 has a long history of delivering up-to-date intelligence data when needed, not days later.
 Without the SR 71, our reconnaissance capability is greatly diminished; not only reconnaissance as in the instances noted above, but also for battle situations like those in the Gulf War. There are two basic types of reconnaissance systems; aircraft and satellites. Only one airborne vehicle can operate over hostile territory with impunity -- the SR-71,Period.It is a reconnaissance vehicle, airborne, which can provide synoptic coverage.Synoptic coverage is the collection of data on a very large target area during a single flight. For example, the SR-71, in a single mission, can collect intelligence on all of Iraq, effectively providing a snapshot of Iraq’s assets at one point in time. Satellites must make many passes to accomplish the same coverage, with considerable time lapse between each pass.

The SR 71 Blackbird:A Few Details

 
One of the Pratt and Whitney J58 engines

   The SR 71 Blackbird in lowflight with J58 engines operating as ordinary jets

 SR The SR 71 configuration:3 View

General characteristics
Crew: 2
Payload: 3,500 lb (1,600 kg) of sensors

DIMENSIONS
Length: 107 ft 5 in (32.74 m)
Wingspan: 55 ft 7 in (16.94 m)
Height: 18 ft 6 in (5.64 m)
Wing area: 1,800 ft2 (170 m2)
The SR-71 is a large aircraft that can be compared respectfully to the size of a Boeing 727. The SR-71 is approximately 103.876 feet excluding the nose probe, which is four feet, eleven inches. The wingspan of the airplane is 55.62 feet and the height is 18.5 feet. The vertical stabilizers, which are the two large fins at the rear of the aircraft, have a total area of 150.76 square feet and the fuselage is approximately five and a third feet in diameter.

Powerplant: 2× Pratt & Whitney J58-1 continuous-bleed afterburning turbojets, 32,500 lbf (145 kN) each.To climb and cruise at supersonic speeds, the Blackbird's Pratt & Whitney J-58 engines were designed to operate continuously in afterburner. While this would appear to dictate high fuel flows, the Blackbird actually achieved its best "gas mileage," in terms of air nautical miles per pound of fuel burned, during the Mach 3+ cruise.Each J58 engine has 32,500 lbs. of thrust, enough to drive the largest ocean liners. They are the largest of their kind and used to be the most powerful in the world. The engine is one part of a propulsion system, which includes an inlet, and an ejector, each producing thrust. In order for the system to work properly over a long period of time, the inlet must capture the onrushing air properly. To do this, a large spike is placed in the inlet and moves forward and back as conditions change. When the air is not captured properly, an event called an unstart occurs. An unstart is best described as a violent yaw where the aircraft pulls to the side where the engine has unstarted. To correct the problem, the pilot must push the spike totally forward and adjust it to capture the air properly, this is called a manual intake. The J58 engines operate as ordinary jets at low speeds, switching to become ramjets at high speeds above 2,000 mph.

Empty weight: 67,500 lb (30 600 kg)
Loaded weight: 170,000 lb (77 000 kg)
Max takeoff weight: 172,000 lb (78 000 kg)
Wheel track: 16 ft 8 in (5.08 m)
Wheel base: 37 ft 10 in (11.53 m)
Aspect ratio: 1.7
[In aerodynamics, the aspect ratio is an airplane's wing's span divided by its standard mean chord (SMC:Standard Mean Chordis defined as wing area divided by wing span). It can be calculated more easily as span squared divided by wing area]
PERFORMANCE
Maximum speed: Mach 3.3+ (2,200+ mph, 3530+ km/h) at 80,000 ft (24,000m)
Range:
             i)Combat: 2,900 nm (5400 km)
             ii)Ferry: 3,200 nm (5,925 km)
Service ceiling: 85,000 ft (25,900m, 16 miles)
Rate of climb: 11,810 ft/min (60 m/s)
Wing loading: 94 lb/ft2 (460 kg/m2)
Thrust/weight: 0.382
The estimated maximum speed of the aircraft is Mach 3.2 and some sources say that it can accelerate to Mach 3.5. The estimated maximum altitude is 85,000 feet but some sources say that the SR-71 can fly up to 100,000 feet and can probably go even higher.
The SR-71 is the fastest and highest flying production aircraft in the world. The only aircraft that is faster is the X-15 that can reach a speed of over 4,000 mph. The only aircraft ever to come close to the SR-71's speed besides the X-15 is the Russian MiG-25 Foxbat. The MiG-25 could only reach speeds of over Mach 3 for a few minutes. The Anglo-French Concorde is the only aircraft besides the SR-71 that can fly at supersonic speeds for hours at a time.