Reports of plans for a high-performance piloted replacement for the SR-71 date back more than a decade. In 1979 it was reported that a "Mach 4+", 200,000-ft High altitude aircraft that could be a follow-on to the Lockheed SR-71 strategic reconnaissance vehicle in the 1990's has been defined by the Air Force Aeronautical Systems Division and Lockheed.

As previously noted, reports of the existence of a successor to the SR-71 surfaced repeatedly during the debate over the termination of the SR-71. Subsequent observations of mysterious aerial phenomena have been connected with the 1988 reports that Aurora was a Mach 6 stealthy reconnaisance aircraft that was being developed to replace the SR-71.

Analyst's predicted that the $10 billion program would result in the production of about 30 aircraft. More recently it was concluded that Lockheed was involved in a " Hypersonic replacement for the Mach 3 plus SR-71. Circumstantial evidence suggests that this project has been underway since 1987 and that the first flight occurred in 1989. Aurora could be operational in 1995, six years after the probable first flight."

This analysis suggested that the total development costs might range from $4.4 billion to $8 billion, with the procurement of 24 aircraft costing an additional $10 billion to $24 billion.

According to another report, by mid-1992 " Aurora was being flown from a base in the Nevada desert to an atoll in the Pacific, the on to Scotland to refuel before returning to the US at night. Specially modified tanker aircraft are being used to top up Aurora's tanks with the liquid methane fuel in mid-air. The Us Airforce is using the remote airbase at Macihanaish, Strathcyde, as a staging point. The mystery aircraft has been dropping in at night before streaking back to America across the North Pole at more than six times the speed of sound. An F111 fighter bomber is scrambling as the black-painted aircraft lands, flying in close formation to confuse prying civilian radars."

The rationale used most frequently by the Department of Defense for the SR-71's termination was financial. The Blackbird's operation and maintenance costs were very high. According to some reports, the Sr-71's O&M costs were very nearly $70 million in FY-90 and FY-91. Furthermore, they argued, imaging satellites could now conduct world-wide surveillance more efficiently and less expensively than manned reconnaissance aircraft.

Independant aerospace analyst's, however, deflated this argument somewhat by pointing to the unique advantages aircraft bring to the reconnaissance arena. Aircraft for example are inherently flexible and unpredictable. Though they are not as fast as satellites, they can fly lower and the interval between over the horizon, arrival and time-over-target is just as short. Aircraft have wide choice of routes, so tracking ships are unlikely to see it on the way in. Application of low observable technology ("stealth") could further reduce warning time. Thus it appears plausible that aircraft may still have a role in global reconnaissance.

Another analyst has considered the possibilities of " Aurora's" characteristics and capabilities. A long range aircraft follow-on to the SR-71 would be a blended delta with a 75 degree leading-edge sweep and retractable low-speed forplanes. It would be powered by two regenerative air-turboramjet (RATR) engines of 180kN sea-level static thrust. It would carry a crew of two and use a synthetic aperture radar with real-time downlink for reconnaissance. It is suggested that this type of platform could be very responsive, much more easily maintainable than the SR-71 and could deliver imagery of most points of interest within six hours of of the decision to go. A speed between Mach 5 and Mach 6+, and a cruising altitude of 40 kilometers, would make the aircraft invulnerable to any current missile system, and for the immediate future.

A wide range of reports of observations of mysterious aerial phenomena have been associated with the Aurora aircraft. These observations are also in regards, consistent with the suggested Exotic Propulsion Aircraft.Those reports relating to both possibilities are discussed here, while those reports unique to the Exotic Propulsion Aircraft are discussed subsequently. These unexplained phenomena have led some to conclude that "the US Goverment has secretly developed and deployed a hypersonic reconnaissance aircraft, probably as a replacement for SR-71."

There are two classes of reports relating to Aurora: those that are consistent with a limited experimental program; and those that are suggestive of the existence of an operational capability.Edwards Air Force Base in southern California is the primary facility used by the American military for the flight testing of experimental aircraft. In addition, the Groom Lake Facility at Nellis Air Force Base ( Area 51 ) in Nevada was used for the development of the F-117A, and has been associated with reports of other advanced aircraft. Given the geographical concentration, it would not be surprising if secret aircraft undergoing flight tests were to be observed in the Southwestern United States.

In October 1990 Aviation Week & Space Technology published reports of..."A high altitude aircraft that crosses the night sky at extremely high speed... The vehicle typically is observed as a single bright light - sometimes pulsing - flying at speeds far exceeding other aircraft in the area, and at altitudes estimated to be above 50,000ft. Normally, no engine noise or sonic boom is heard."More recently, a sighting by two British Airways pilots and other witnesses at Manchester Airport on January 6 1995 has been attributed to the Aurora aircraft. These sightings compare with an unknown "Black Triangle" which has been sighted in many places over Europe, the most famous being the "Belgian Incident" discussed later in this article.

Probably the most compelling evidence for such flight tests are the series of unusual sonic booms reported above Southern California, beginning in mid to late 1991. On at least five occasions, these sonic booms were recorded by at least 25 of 220 US Geological Survey sensors across Southern California used to pinpoint earthquake epicentres. The incidents were recorded in June, October, November and late January 1991. Seismologists estimate that the aircraft were flying at speeds between Mach 3 and 4 and at altitudes of 8 to 10 kilometres. The aircraft's flight path was in a North Eastern direction, consistent with the flight paths to secret test ranges in Nevada ( Groom Lake/Area 51). Seismologists say that the sonic booms were characteristic of a smaller vehicle than the 37 metre long Shuttle Orbiter. Furthermore, neither the shuttle nor NASA's single SR-71B were operating on the days t

One of the seismologists, Jim Mori noted....

We can't tell anything about the vehicle. They seem stronger than other sonic booms that we record once in a while. They've all come on Thursday mornings about the same time, between 6 and 7 in the morning."
These "skyquake" are a continuing phenomenon, with the most recent report over Orange County, California, coming on July 20 1996. It is reported that the "Quake" occurred around 3pm PST, fitting the "skyquake" pattern in the following respects.

• Described as similar to an earthquake in some respects(rattling of loose objects,etc)
• . but also like a boom(but no distinct double bang as far as is known).
• Severe enough to light up Goverment and media switchboards, but no known damage.
• Not an earthquake (Cal Tech sensors saw nothing)
• Local military bases deny any knowledge(Well they would anyway)
• No known other source (eg. explosion)

Reported sightings:

Unusual high performance aircraft are not confined to the Sothwestern United States.More recently, such observations have been reported in other parts of the US as well as in Europe. These reports are particularly intriguing because they are difficult to reconcile with an experimental test program, since there would be no reason for test flights to be conducted over Europe. Rather, these reports would have to be understood in the context of the deployment of an operational aircraft.

One unexplained set of observations was reported at Beale Air Force Base, the California facility that was long home to the SR-71. On two consecutive nights in late February 1992, observers reported sighting a triangular aircraft displaying a distinctive diamond shaped lighting pattern, comprised of a red light near the nose - similar to the F117 configuration - two "whitish" lights near what would be conventional wing tips and an amber light near the tail.While the wing lights are reportedly much brighter than normal navigation lamps, they do not illuminate the aircraft's platform. Observers claim the vehicles wing lights are approximately twice as far apart as those on the F117, and nose-to-tail light spacing is about 50 percent longer than that on the stealth fighter.

In early 1992 it was reported that...

" RAF radars have aquired the hypersonic target travelling at speeds ranging from about Mach 6 to Mach 3 over a NATO-RAF base at Macrihanish, Scotland, near the tip of the Kyle of Lochalsh peninsula, last November and again this last January 1993."

 A reputable source has said that these triangular shaped planes have actually been in service since 1989. In fact, there is believed to be a small squadron operating out of Beale AFB, in California.Some believe that the aircraft is able to cruise at altitudes of above 180,000 feet and travel at a speed of Mach 8. At 5,280 mph, this is more than 2 times the official world record. It’s been reported that Aurora operates mainly at night and incorporates the latest radar-evading "stealth" advancements. An aircraft traveling at Mach-8 could reach any point on the globe in less than three hours.

Finally, stealth aircraft were limited to nighttime flying as they could be spotted at ease during the day. This leads to the subsequent task in future stealth aircraft development…the creation of a plane invisible to the eye. Lockheed’s legendary ‘Skunk Works’ experimental arm is known to be developing new electro-chromic materials. Their aim is to create camouflage panels which can change color or tint when subjected to an electrical charge. Other engineers like Boeing and Northrop, are also working on similar stealth technologies. One of these systems is the "electrochromic polymer" that is being developed at the University of Florida. These thin sheets cover the aircraft’s skin and sense the hue, color and brightness of the surrounding sky and ground. The image received is then projected onto the aircraft’s opposite side. When charged to a certain voltage, these panels undergo color change. Another similar "skin" is being tested at the top-secret Groom Lake facility at Area 51 in Nevada. It is reputed to be composed of an "electro-magnetically conductive polyaniline-based radar-absorbent composite material." The system also utilizes photo-sensitive receptors all over the plane that scan the surrounding area, subsequently the data is interpreted by an onboard computer which outputs it much like a computer screen making the aircraft virtually invisible to site.

Stealth is clearly the future of air combat. In the future, as air defense capabilities grow more accurate and deadly, stealth can be a factor for a decisive victory by one country over an other. In the future, stealth will not only be incorporated in fighters and bombers but also in ships, helicopters, tanks and transport planes. Ever since the Wright brothers flew the first powered flight, the advancements in this particular field of human endeavor has seen staggering heights. Stealth is just one of the advancements that we have seen. In due course of time we will see many improvements in the field of aviation which could one-day even make stealth obsolete.