An eyewitness description, a secret test site, and a new analysis of advanced aeronautics paint a portrait of Aurora

* By Bill Sweetman

Does the U.S. Air Force - or perhaps one of America's intelligences agencies - have a new secret spy plane in action? A growing body of evidence suggest that the answer is yes. A startling disclouse came recently when Chris Gibson, a British oil engineer and highly trained aircraft-spotter produced a sketch that captured the shape and size of an unusual aircraft he saw during daylight hours in August 1989, flying over his drilling rig in the North Sea. The expert eye-witness's drawing is the keystone that, with other evidence, provides an understanding of a secret hypersonic reconnaisance aircraft that is widely rumoured to exist, but routinely denied by U.S. officials. Its nickname is Aurora.

Gibson - a former member of the disbanded Royal Observer Corps, a group of volunteer aircraft-spotters - was able to estimate the strange airplane's length and width by comparing it with the known dimensions of the K-135 refueling tanker and two F-111 bombers flying alongside. But it wasnt until last year, when he came across a magazine design, that Gibson suddenly made sense of the sharp triangualr silhouette he saw.

Analysts believe that Aurora is an operational spy plane that replaces the retired Lockheed SR-71 Blackbird. Like its predecessor, Aurora costs several million dollars per flight, and is sent out only in missions where the plane's sensors can gather vital information unobtainable by satelite reconnaissance or other means.

It's plausible that Aurora was used to photograph Iraq during Operation Desert Storm in an attempt to provide tactical intelligence to ground-based military commanders. Aurora's unique capabilities also equip it for surveillance of nuclear proliferation. The list of nations of varying political complexions that covertly possess or are pursuing nuclear arms capabilities include India, Iran, Iraq, Israel, North Korea, Pakistan, and South Africa. Suprise visits by an reconnaisance aircraft can give intelligence analysts clues - such as the presence of military trucks at an ostensibly civilian plant - which wouldnt be left out in the open when a spy satelite is scheduled to make its pass overhead.

Aurora overflights of Russia have probably not occured. Such missions would violate an agreement in place since a Lockheed U-2 plane was shot down over the Soviet Union in 1960. It is likely, that the Aurora monitors the submarine-building programs of Russia, China and other nations from well outside their airspace using side-looking sensors.

Gibson's North Sea sighting completes a puzzle that has obsessed military-aircraft analysts for several years. Consider the following pieces of evidence hinting at the existence of something unacknowlegded that flies high and fast:

* In February 1990, the Air Force retired its SR-71 spy planes. The official reason was saving the $200 million to $300 million a year it cost to operate the fleet of Blackbirds. Reporters were told tha the SR-71's role had been taken over by advanced spy satellites.

* The money saved was less than 7 percent of the approximately $4 billion the Air Force spends yearly on satellite reconnaisance - mere chicken feed by Pentagon standards. Keeping the SR-71's in service would have provided cheap insurance against an unlucky string of satellite and rocket failures, such as the ones that occured in 1985-'86.

* The Air Force actually discouraged congressional attempts to reverse this termination of its most glamorous aircraft mission. Never in its history had the flying service walked away from a manned mission without a fight.

* The pace of activity at the Air Force's top-secret Groom Lake test site in the Nevada desert has increased dramatically in recent years, suggesting the presence there of one or more secret aircraft programs. By comparing recent photos of the base with ones taken in the late 1970s, its apparant that several large new buildings were added during the 1980s. Always visible in the recent pictures are a number of chartered Boeing 737 airliners that ferry workers in from other defense-industry towns such as Palmdale, Burbank, or Edwards in Southern California, or from Nellis Air Force Base in Nevada.

* Since mid-1990, unexplained sonic booms have periodically rattled Southern California. Officials at the United States Geological Survey, the agency that monitors earth-quake activity, no doubt irked the military with their public statements that a very fast, high-flying aircraft was causing the "airquakes" registred on their array of seismographs.

* The federation of American Scientists, a private Washington, D.C.-based policy group, issued a report late last year on the likelihood that unacknowlegded military aircraft might exists. The cautious review of unclassified literature on the subject concluded that several new types of aircraft may indeed be covertly flying around.

"It is close to midnight, but all the clocks are set to 0730 Greenwich time. In a closed and guarded hangar, ground crews help two men into orange pressure suits clamber into a delta-shaped, dull black airplane. The pilot touches keys that tell computers to start the engines. At first, the aircraft emits a subdued whine, whcich builds up quickly and is joined by the sound of rushing air. Then there is a flash of light from the intake and exhaust ducts as a wave of noise explodes, rolling harshly over across the dry lake bed. Within the roar are the scream of small rockets, the cracking thunder of a huge fighter engine, and a massive pulsing - as low as one cycle per second - that shakes the entire desert base."

Gibon's sighting now makes it spissible to reconstruct the Aurora program's history. The spy plane was operational, or nearly so, by August 1989, just before the Air Force parked its SR-71s for the last time. Aurora would have madeits first flight by 1986 at the latest, following a development effort that was launched in 1981.

This analysis elicited denials by high officials involved in defense and intelligence matters. Ohio Democratic Sen. John Glenn asserted that his sources in the intelligence community told him there was no such aircraft. "I think they're telling the truth", he said.

Pete Williams, chief spokesman for the Bush administration's Secretay of Defense, Dick Cheney, gave a standard answer to a query about Aurora. "If there were such a program, we wouldn't discuss it". Williams explained that Pentagon policy says the same answer "must always be given" to queries about secret programs - whether or not they actually exist - to avoid revealing the truth. Donald B. Rice, Bush's Secretary of the Air Force, stated :"There's no program in the Air Force, none anywhere else that I know of. It simply doesn't exist." To some observers the stridency of Rice's response was puzzling. Why didn't he simply utter the usual Pentagon disclaimer?

Black us the adjective most often applied to the hidden world in which such engineering activites unfold. In a 1985 Pentagon bugdet document requesting production funds for 1987, a censor's lip let the line item "Aurora" appear, grouped with the SR-71 and U-2 programs. Even if Aurora ectually was the project's name at the time, it almost certainly would have been changed after being thus compromised; "Senior Citisen" is one of new label that has been reported. Rated by the Pentagon as an "unacknowlegded special-access program," the plane's existence and real name are secret, and therefore deniable.

Unconfirmed reports of Aurora's existence first surfaced in 1986 and POPULAR SCIENCE conjectured about the airplane's likely design in the November 1988 issue. Now, fresh reports from secret-airplane hunters such as James Goodall, who heard the and felt bone-shaking sounds coming from the Groom Lake facility late in December, continue to flesh out the picture of Aurora and the technology that makes it work.

Armed with patience and braced for occasional confrontation with no-nonsense security patrols, resolute observers like Goodall trek trhough the harsh Nevada desert to a mountainside overlooking desiccated Groom Lake. From several miles away - as close as they can get without entering off-limits goverment land - the wathcers can see the large air base eith its motley collection of hangars. Some of the buildings are vast.

Yet, like a mirage the isolated facility with its six-mile runway doesn't exist - officially, that is. And its non-existence is longstanding. A 1992 Lockheed Corp. paper on the early days of the U-2 program refers to flight-testing at Groom Lake 35 years ago as having occured merely at "a remote location"

For some, montoring events on the dry lake bed provides the excitement of pursuing a mystery. Author and photographer Goodall, who has been chasing classfied programs for almost 30 years, is motivated by enthusiasm for aircraft and a conviction that he's entitled to know how his taxes are being spent. His earwitness account indicates that the airplane's propulsion system is unconventional to say the least. "We heard Aurora from 18 miles away. The sound was so intense that you feel it. It was quite something else - a pulsing noise that you'll never forget"

"The airplane begins rolling forward at half-past midnight, then accelerates and noses up into the sky like a hot fighter. Seconds later it is gone, trailing a shattering roar across the desert. In the cockpit, the pilot sees his course overlaid on a detailed map as the craft climbs through 60.000 feet at a steep 70-degree angle. Just minutes after takeoff, the plane is cruising northeast at six times the speed of sound, covering almost one mile per second. More than 20 miles above the ground, it passes unheard over Montana and North Dakota into Canadian airspace. Five thousand miles away, a loaded KC-135 tanker lifts heavily into the early morning sky from a secure air base in western Scotland. At a second base farther south, four F-111 crewmen walk toward their pair of aircraft. Only the crew and their base commander knows this will not be a routine training flight."

Aurora was almost certainly built Lockheed's fabled Skunk Works, now called the Lockheed Advanced Development Co. Of all known design organizations, only the Skunk Works has the proven ability to manage large programs incorporating breakthrough technology in total secrecy. Analysis of Lockheed's financial statements makes it possible to estimate Aurora's price tag at about $1 billion per aircraft. At most, 10 to 20 of the new spy planes have been built.

A hypersonic prototype paved the way for Aurora. In 1975, Lockheed proposed a small hypersonic research aircraft that would be launched from the back of an early version of the SR-71. And a definite survey of Lockheed aircraft, published in 1982, stated that the company have already flown a mach 6 experimental craft.By the late 1970s the US goverment probably had two main reasons for going ahead with Aurora. The first: improved Soviet surface-to-air missile (SAM) systems posed an increasing threath to the SR-71, whcih flies at Mach 3.2 (2.100 mph) and reaches altitudes above 80.000 feet. By 1980, two potent new Soviet antiaircraft weapons, the SA-10 Grumble and the SA-12 Gladiator/Giant, were under development. Both have a maximum altitude of about 100.000 feet and feature advanced tracking and guidance systems. The second reason for building Aurora was that the satelites alone are not the best solution to reconnaisance requirements. While they take superb pictures, satellites also have inherent limitations. They follow fixed, predictable orbits, which make their appearance no suprise to a shrewd adversary. Although earthbound controllers can command satellites to fire thrusters to adjust their orbits, this ability is strictly limited by a finite on-board fuel supply. In addition, because it is difficult to supply the amount of power needed to operate an all-weather radar, most satellites carry only daylight or low-light cameras.

Although they cost several hundred million dollars apiece, spy satellites last, on average, only five years before they are dumped into the atmosphere and replaced. And it is difficult to increase surveillance quickly in a crisis unless a stockpile of reserve satellites and launchers is kept ready - as the former Soviet Union once did.

Aircraft are much more flexible. They can be dispathed exactly where and when they are needed, and they can be fitted with day, night, or bad-weather sensors, depending on the conditions in the target area.

"During the hour it takes to reach the initial point for descent, the pilot and reconnaisance systems officer (RSO) in the backseat are fully occupied with checking equipment to see how it operates in the 1,000 Fahrenheit friction heat soaking into their aircraft's structure - a delicate balance between speed, altitude, and deceleration rate. Over the North Sea, the tanker and the F-111s gather into a loose formation and follow a racetrack pattern. Appearing suddenly, the black jet turns in behind the KC-135 and connects with its refueling boom, wavering a little while matching the tanker's low speed. During the next ten minutes, 40 tons of liquid methane flow into the spy plane before it turns away and hurtles skyward. Already, another loaded methane tanker and two more F-111s are preparing to depart from their base in Britain."

An analysis of Aurora's three-dimensional shape can be extrapolated from its 75-degree swept triangular outline. the aircrafr corresponds almost exactly in form and size to hypersonic reconnaisance aircraft studied in the 1970s and 1980s by McDonnel Douglas, according to Paul Czysz, now a professor of aerospace engineering at St.Louis University. Czysz worked on hypersonics while at McDonnel Douglas, including the company's proposal for the National Aerospace Plane program, and is an acknowlegded expert in the field. Effient hypersonic planes "are basically air-breathing propulsion systems," he says.

Like the SR-71, Aurora has a crew of two. Flying it is quite unlike piloting a conventional aircraft. There is little if any outside view, because a normally angled windshield causes to much drag and gets too hot. For these reasons, Aurora may have a retractable windshield used only for takeoffs and landings; at other times, the windshield would be covered by a heat shield. Aurora's pilot is really a mission manager, monitoring the aircraft and its systems and following the course of the flight on large-format video displays. His or her most important function is to cope with the unexpected; shifts in upper-atmosperic temperature, weather developments over the target area or refueling zone, or developments with the plane's mechanical or electronic systems.The RSO supervises a battery of sensors. The mst important is a synthetic-aperture radar (SAR), a side-looking instrument that takes a sequence of snapshots of the target as the aircraft moves and compiles them into a single rader image that is as sharp as if had been acquired using an antenna hundreds of feet wide. The best SAR images are classified, but have benn described as "near-photographic," allowing different types of land vehicles to be easily distinguished from more than 100 miles away, regardless of clouds or smoke.

In clear weather, Aurora uses daylight and infrared cameras for ultra-detailed work. And unlike a satellite, the craft can be scheduled to make its reconnaissance passes at the golden hour for covert imaging; early morning, when the low sun provides even illumination and long shadows that highlight features on the ground, before heat-induced haze forms. A phased-array antenna built into Aurora's upper surface - near the tail end, where aerodynamic heating is minimal - allows the airplane to transmit real-time or near real-time imagery to the Pentagon's satellite network.

"In a Middle Eastern country, a bored radar operator in an underground shelter fails to notice a faint blip on one egde of his screen. The system's computer can't make sense of an echo that's too high to be an airplane and stops displaying it. A few miles from a medium-size city lies a walled, heavily guarded compound containing equipment test stands and several small factory buildings. From time to time a siren sounds, and temporary covers thrown over sensitive equipment. All activity ceases for the few minutes it takes a known spy satellite's imaging path to pass over the base. But no warning is given this morning. Technicians, including two blond Caucasians, are busily preparing a rocket motor for testing on an open stand, and a truck that left a Czech machine-tool factory several days earlier is being unloaded. All of this detail is faithfully stored on a battery of hard-disk memories by a camera with a 48-inch telephoto lens. Three hours and 15 minutes after its takeoff from Nevada, the spy plane makes a wide turn back toward Northern Europe. The RSO selects the clearest image and transmits them to a satellite with a few keystrokes. In five minutes, hard copues as sharp as an original negative are rolling out of a processing machine 6.000 miles away."

Aurora uses ramjet engines, because no other type can work as efficiently at the speeds the plane travels. In its simplest form, a ramjet is a pinched tube that slows, compresses, and heats the incoming supersonic airstram before adding fuel to it, producing enormous thrust from the hot gas expanding out the exhaust nozzle. However, the compression process also generates tremendous drag. The ramhet designer's challenge is to keep the level of drag from canceling out the slim margin of thrust that propels the aircraft. One way to make a ramjet engine efficient is to stretch it along the entire length of the vehicle. In a hypersonic ramjet aircraft, the underside of the forward body is a ramp that initially compresses the air before it enters the inlet ducts, and the curved underside of the afterbody guides the expansion of the exhaust gas.

ITS A LIFTING BODY

The compressed air underneath the body serves a second purpose: It holds the airplane up. At Mach 6, conventional wings would be superfluos appendages creating horrendous drag. Accordingly, the tips of Aurora's delta planform are mainly there to provide stability and control. The basic problem with ramjets is that they don't work at all unless the aircraft is moving quite fast, and they are not very efficient at speeds less than Mach 2.5. Therefore, Aurora needs some other systems to reach this speed. There are two clues to the way Aurora's designers solved the low-speed propulsion problem. The team for the X-30/National Aerospace Plane (NASP), though tight-lipped about the "accelerator" portion of the NASP engine design, has indicated that it functions as a ducted rocket in parts of its operating cycle. The seconds clue is that Aurora has been associated with two unusual noises: very-low-frequency pulsing sounds and an extremely loud roar on takeoff.

SUPER COLD FUEL

Even though Aurora is 80 to 90 feet long, which is about 20 feet shorter than the SR-71, it could weigh more - as much as 170.000 pounds when fully loaded. A clear two-thirds of its total mass would be fuel. Choosing the right fuel was crucial to Aurora's design. Because various sections of the craft will reac crusing-speed temperatures ranging from 1.000 fahrenheit to more than 1.400 fahrenheit, its fuel must both provide energy for the engines and extract destructive heat from the airplane's structures. This is done on the SR-71, but at hypersonic speeds even an exotic kerosone, such as the special high-flashpoint JP-7 fuel used by the Blackbird, cannot absorb enough heat. The solution for Auroa is a cryogenic fuel - a cold liquefied gas.

The best candidates identified so far are methane and hyudrogen. liquid hydrogen provides more than twice as much energy and absorbs six times more heat per pound than any other fuel. The snag is its low density, which means bigger fuel tanks, a large airframe, and more drag. While liquid hydrogen is the fuel of choice for a spacelaunch vehicle that accelerates quickly out of the atmosphere,studies have shown that liquid methane is better for an aircraft cruising at Mach 5 to Mach 7. Methane (natural gas) is widely avaliable, provides more energy than jet fuels, and can absorb five times as much heat as kerosene. Compared with liquid hydrogen, it is three times denser and easier to handle - inflight refueling has been studied and poses no problem. Aurora can fly at subsonic speeds because its entire body, which has a great deal of area, is a lifting surface. Also, its sharply swept leading egde - like the Concorde's wing - generates a powerful vortex at nose-high flight angles, which clings to the leading edge and boosts the body's lift. Unencumbered by aerodynamic freeloaders such as a conventional fuselage, Aurora's shape is structurally efficient. It packs a lot of fuel and useful equipment into a relativelu small volume that saves weight and minimizes friction drag.

The spy plane's airframe may incorporate some stealth technology, but it hardly needs it. Hypersonic aircraft are actually much harder to shoot down than a ballistic missile, Although a hypersonic plane isn't very maneuverable in the traditional sense, its velocity is such that, within tens of seconds, even a gentle turn puts it miles away from a SAM's projected interception point. So why bother with stealth?

"Having refueled a seconds time from a tanker over the North Sea after its Mideast photo session, the black plane heads east at hight altitude across the Atlantic Ocean, North America, and beyond the California coast. Decelerating and descending above the Pacific Ocean, the craft drags a sonic boom over the water behind it. As it turns back towards its Nevada base, part of the inevitable shock wave bends through the upper atmosphere and rumbles across Southern California as Angelenos are getting ready for work. "There goes another one," they say, wondering wether it's a minor earthquake or "that plane we hear about." Time elapsed from takeoff to landing: 6.5 hours. Distance traveled: 15,500 miles"