SR-91 Aurora

Aurora (SR-91 Aurora) is the popular name for a hypothesised United States reconnaissance aircraft, alleged to be capable of hypersonic flight.

According to the hypothesis, the Aurora was developed in the 1980s or 1990s as a replacement for the aging and expensive SR-71 Blackbird. A British Ministry of Defence report from May 2006, released under the Freedom of Information Act, refers to USAF priority plans to produce a Mach 4–6 highly supersonic vehicle. In September 2007, DARPA and the USAF signed a memo of understanding to build a Mach-6 unmanned aircraft called "Blackswift" under the Force Application and Launch from Continental United States (FALCON) program, but that does not explain the earlier reports. It is believed that the Aurora project was canceled due to a shift from spyplanes to high-tech unmanned aerial vehicles and reconnaissance satellites which can do a similar job as a spyplane, but with less risk of casualties or loss of highly expensive, sensitive equipment.

Unconfirmed reports of Aurora's existence first surfaced in 1986. Popular Science magazine conjectured about the airplane's likely design in its November 1988 issue (right, middle).

Sounds: Most of the evidence for Aurora's existence is anecdotal. Among these tales are the reports of unusual sonic booms above Southern California, dating back to mid and late 1991. On at least five occasions, the booms were recorded by at least 25 of the 220 US Geological Survey sensors across Southern California used to pinpoint earthquake epicenters.

Chris Gibson sighting

In late August 1989, while working as an engineer on the jack-up barge GSF Galveston Key in the North Sea, Chris Gibson and another witness saw an unfamiliar isosceles triangle-shaped delta aircraft, apparently refueling from a KC-135 Stratotanker and accompanied by a pair of F-111 bombers. Gibson and his friend observed this spectacle for several minutes, until the aircraft went out of sight. Having dismissed the F-117, Mirage IV and fully-swept wing F-111 as the identity of this unfamiliar aircraft, Gibson drew a sketch of the formation. Gibson had been in the Royal Observer Corps' trophy-winning international aircraft recognition team since 1980; in other words, he was highly skilled and experienced at identifying military aircraft. Despite this, Gibson was unable to identify the aircraft he saw flying over the North Sea.

When the sighting was made public in 1992, the British Defence Secretary Tom King was told, "There is no knowledge in the MoD of a 'black' programme of this nature, although it would not surprise the relevant desk officers in the Air Staff and Defence Intelligence Staff if it did exist."

Steven Douglas sighting

On March 23, 1992, near Amarillo, Texas, Steven Douglas photographed the "doughnuts on a rope" contrail and linked this sighting to distinctive sounds. He described the engine noise in the May 11, 1992, edition of Aviation Week & Space Technology (p. 62-63) as a:

“

(...) strange, loud pulsating roar... unique... a deep pulsating rumble that vibrated the house and made the windows shake... similar to rocket engine noise, but deeper, with evenly timed pulses.

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In addition to providing the first photographs of the distinctive contrail previously reported by many, the significance of this sighting was enhanced by Douglas' reports of intercepts of radio transmissions:

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Air-to-air communications... were between an AWACS aircraft with the call sign "Dragnet 51" from Tinker AFB, Okla., and two unknown aircraft using the call signs 'Darkstar November' and 'Darkstar Mike.' Messages consisted of phonetically transmitted alphanumerics. It is not known whether this radio traffic had any association with the "pulser" that had just flown over Amarillo. (Darkstar is also a call sign of AWACS aircraft from a different squadron at Tinker AFB)

”

A month later, radio enthusiasts in California monitoring Edwards AFB Radar (callsign "Joshua Control") heard early morning radio transmissions between Joshua and a high flying aircraft using the callsign "Gaspipe".

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You're at 67,000 ft, 81 miles out" was heard, followed by "seventy miles out now, 36,000 ft, above glideslope.

”

At the time, NASA was operating both the SR-71 and the U2-R from Edwards, but it has been confirmed that neither of these types were flying at the time Gaspipe was heard. Curtis Peebles claims in his book Dark Eagles that the intercepted radio transmissions were probably a prank on the part of Edwards security personnel.

Sonic booms

A series of unusual sonic booms were detected in Southern California, beginning in mid to late 1991. On at least six occasions, these sonic booms were recorded by at least 25 of the 220 U.S. Geological Survey sensors across Southern California used to pinpoint earthquake epicenters. The incidents were recorded in June, October and November 1990, late January 1991, and in mid 1994. Seismologists estimate that the aircraft were flying at speeds between Mach 5 and 6 (3,300-4,000 mph) and at altitudes of 8–10 km (26,200-32,800 ft). The aircraft's flight path was in a north-northeast direction, consistent with flight paths to secret test ranges in Nevada. Seismologists say that the sonic booms were characteristic of a smaller vehicle rather than the 37-meter long shuttle orbiter. Furthermore, neither the shuttle nor NASA's single SR-71B was operating on the days the booms were registered. It is not definitively known if these events can be tied to the Aurora program or to other acknowledged or secret programs.

In the article "In Plane Sight?" which appeared in the Washington City Paper on July 3, 1992 (p. 12-13), 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."

Former NASA sonic boom expert Dom Maglieri studied the 15-year old sonic boom data from the California Institute of Technology and has deemed that the data showed "something at 90,000 feet (c. 27.4 km), Mach 4 to Mach 5.2". He also said the booms did not look like booms from aircraft that had traveled through the atmosphere many miles away at LAX, rather, they appeared to be booms from a high-altitude aircraft directly above the ground moving at high speeds. The boom signatures of the two different aircraft patterns are wildly different.

General characteristics

• Crew: 2 (1 pilot, 1 reconnaissance systems officer)
• Length: 35 m (115 ft)
• Wingspan: 20 m (65 ft)
• Height: 6 m (19 ft)
• Wing area: 300 m² (3,200 ft²)
• Empty weight: 29,480 kg (65,000 lb)
• Max takeoff weight: 71,215 kg (157,000 lb)
• Powerplant: (Low Speed) 4× afterburning turbofans, (unknown thrust) each, (High Speed) 4× ramjets, scramjets or pulse detonation engines (267 kN est. thrust) (High Speed) 4× ramjets, scramjets or pulse detonation engines each

Performance

• Maximum speed: Mach 5-10 at altitude (unknown at sea level)
• Range: 15,000 km (9,320 mi)
• Service ceiling: 40,000 m (131,000 ft)
• Thrust/weight: unknown

Fuel types

• Methane, MCH, LH₂ or hydrogen fuel cells.
• Possible use of liquid oxygen and hydrogen oxides.
• Possible use of MHD (MagnetoHydroDynamics) technology.

Other equipment

• Cameras
• IR sensors
• Other advanced recon sensors