The question "Has the USA developed a top secret replacement for the SR-71?" is something that has intrigued numerous aviation enthusiasts, from professional aviation journalists to curious amateurs - such as myself. Firstly, I believe we need to start by establishing four simple facts:
Accepting those three facts leaves the inescapable conclusion that the USAF brought into service a replacement for the SR-71 and had the aircraft in operational service before the SR-71 was retired in 1990 - thirteen years ago. The official reason given for the retirement of the SR-71 was that the operating costs of between $200-$300 million a year simply couldn't be justified. Yet the costs were fairly 'flat', sufficient spares existed, there was plenty of life left in the airframes and $200-£300 million in the overall USAF budget was small change for the capability the aircraft provided - so that excuse simply doesn't hold water. The evidence certainly strongly suggests that the USAF were quite content for the SR-71 to be retired, because the manned reconnaissance capability it provided was already available on another manned platform.
Next the obvious questions - what is the replacement aircraft called, when did it enter service, who developed it, where is it based, what are it's performance characteristics and what does it look like?
Well for one I don't believe the aircraft, is called Aurora and there is probably more than one specific aircraft anyway. One of the aircraft may have had that 'nickname' bestowed on it briefly during development in the mid 1980's, but now it's probably referred to by a completely innocuous name in Top Secret documents, something with no obvious connection to hypersonic aviation, such as 'Tidespring', or any other obscure name you care to dream up. Secondly, since the USAF probably operates the aircraft, they will have bestowed on the aircraft some kind of unusual military designation - HSRA-6005 - or something else you might care to make up. Those that know are saying nothing, so the rest of us shall all have to wait until the aircraft emerge out of the 'black' world into the glare of the aviation media for the correct answers.
I believe you can narrow the companies with the capability to develop these aircraft away from the prying eyes of the public and media down to two - Lockheed and Northrop. Both those companies developed 'black' aircraft for a number of years without precise details becoming available - the F-117 and the B-2 and both have a long history of engaging in this kind of activity. Although the McDonnell Douglas Phantom Works recently displayed the unusual 'Bird of Prey', the company only set up this research unit in 1992, long after our aircraft were flying. Furthermore, the 'Bird of Prey' is effectively a research aircraft for a programme to develop a UCAV - rather than a possible hypersonic research aircraft - and probably lost out to the Boeing designed X-45A design when Boeing absorbed McDonnell Douglas in 1997. So, for arguments sake, lets assume that Lockheed and Northrop were awarded a contract back in the mid 1970's to early 1980's to develop, in competition with each other, a hypersonic replacement for the SR-71. Why award a contract to both companies? Well, firstly because their proposals operated right at and even beyond the boundaries of current knowledge, probably utilized different engine technologies YF-23s in formation and there was no guarantee that they would work as planned. Secondly, competition between companies on a winner take all contract tends to concentrate the minds and focus of the companies involved. Thirdly, the USAF and D of D have insisted on such a competition in all recent major contracts, such as the General Dynamics YF-16 v the Northrop YF-17 Lightweight Fighter competition, which led to the F-16 and F-18. In addition, the Advanced Tactical Fighter competition was between the Lockheed/Boeing/General Dynamics YF-22A and the Northrop/McDonnell Douglas YF-23 and resulted in the F-22. At this point it's worth remembering that after the 'flyoff' the prototype YF-23's were just flown to NASA Dryden and parked up - but we shall return to the YF-23 later.
Having built their prototype aircraft in secrecy, Lockheed and Northrop would have looked to the US Air Force in the mid 1980's to provide a secret facility where the aircraft could be tested well away from prying eyes. Groom Lake in Nevada is the most obvious location for this activity and, although there are other locations in the vast desert areas of the USA, such as Holloman AFB and White Sands in New Mexico, where this testing could have taken place, for the moment let's concentrate on Groom Lake. It's probably significant that Groom Lake already possessed an existing runway that extended across the salt lake to provide a total usable length of 25,000ft (7620m). Also, the first reports of an unusual sounding aircraft engine first surfaced from the Groom Lake area in the mid 1980's and the restricted area around Groom Lake was increased enormously in the mid 1980's - so Groom Lake seems the obvious candidate.
So, we now have the possibility of a 'fly-off' between a Lockheed and a Northrop designed replacement for the SR-71 taking place from the mid 1980's onwards at Groom Lake. What kind of aircraft would those companies have designed? Well, for one thing, working on the principal that strategic reconnaissance aircraft development has always been 'higher & faster', the performance of the new aircraft would be an even bigger jump than that between the U-2 and SR-71, the first a subsonic powered 'glider' capable of operating at around 70,000ft and the second capable of 90,000ft and Mach 3.2. So it's not unreasonable to consider the possibility of a hypersonic (Mach 6+) aircraft - but is such an aircraft really possible?
Well, if Lockheed and Pratt & Whitney could develop an airframe and engines in the late 1950s early 1960's (the A-12 first flew on 25 Apr 62) capable of 90,000ft and Mach 3.2, they would not have sat around doing nothing for the last 40 years! Also, in the intervening years the development of advanced materials, including composites and titanium-based alloys, allow the use of an airframe capable of maintaining structural integrity at very high temperatures. Heat is the enemy of hypersonic aircraft and, with temperatures around 1,800 to 2,000 degrees Fahrenheit in the cruise, any hypersonic aircraft will also need to employ some form of active cooling system to prevent the crew and avionics equipment becoming cooked. The engines that power the aircraft are certainly far removed from modern turbojets that would be useless at the height/speed the aircraft operates. The 25,000ft runway available at Groom Lake would allow the operation of an aircraft that accelerated very slowly, in other words an Donuts on a rope contrail aircraft powered by an prototype engine that initially produced low power, but with the thrust constantly building up as speed increased, necessitating a very long take-off run.
This in turn could point towards the employment of either a Pulse Detonation Wave Engine (PDWE), some form of advanced pulsejet, or some combined cycle engine that can function initially as a low powered turbojet and later as a high power ramjet, depending on the speed of the aircraft. This might also explain the low frequency, rumbling, pulsing sounds, often as low as one cycle per second, which have been heard around Groom Lake for many years. It might also explain the unusual 'donuts on a rope' contrails that have been sighted and even photographed in the western USA. The advanced engines would also have to be powered by some exotic fuel to function in the intended flight regime, possibly a form of super-cold liquefied gas, such as methane or hydrogen.
So what we're looking at is an aircraft capable of operating at Mach 6 at between 200,000-300,000ft. At these speeds and heights the aircraft would be invulnerable to any known AA missile and could go anywhere on the globe with impunity. But, just like the SR-71, it almost certainly requires air-to-air refuelling for long sorties and so must also be capable of operating and manoeuvring safely at high subsonic speed at around 30,000ft, enabling it to formate behind a specially modified KC-135. The security requirements and special support necessary to operate the aircraft probably means it has never operated from anywhere other than Groom Lake. Certainly stories of the aircraft operating from say Machrihanish in Scotland are pure and utter fantasy. There used to be a Nuclear Weapons Store and a US Navy SEAL unit based there, but the SEALs were there because it was conveniently close to the US submarine base at Holy Loch, that was really all. It's no co-incidence that the SEALs departed almost as soon as Holy Loch ceased to be used by US submarines. The other airfield facilities at Machrihanish were basic to say the least and that was the reason few if any large aircraft ever operated, even briefly, out of that god-forsaken dump. Furthermore, operating such as unusual aircraft even from remote US bases, such as Diego Garcia in the Indian Ocean or Kwajalein Atoll in the Pacific, would have only attracted the attention of bored or just curious US servicemen and women, and by now a photograph would have got out.
For arguements sake lets assume that Lockheed won the fly-off at Groom Lake. The appearance of their hypersonic aircraft would be determined, just like the Northrop design, entirely by the speed at which it is intended to operate. For clues as to the appearance of the aircraft, I think we need look no further than the X-30 NASP, which was 'cancelled' in the mid-1990's. The NASP had its roots in a highly classified DARPA project called Copper Canyon that ran from 1982-5, which again points to the right timescale. Informed commentators have all agreed that the overall shape of the NASP conforms with the requirements for a hypersonic aircraft. So although officially the NASP was never flown, there is every possibility that this programme served as a cover for the SR-71 replacement and that in secret an aircraft was flown and then accepted into service in the late 1980's early 1990's.
At this point we should return to the Northrop/McDonnell Douglas YF-23 - this aircraft was just too good to abandon, but perhaps Northrop weren't bothered because they already had another 'black' version of the YF-23 in service! Although the YF-22 won the fly-off and was more manoeuvrable, the YF-23 was stealthier and blisteringly fast, even with inadequate underwing fixed engine inlets. So here we have an aircraft which could form the basis for a very stealthy, fast, tactical reconnaissance aircraft to work in conjunction with the F-117, which for arguments sake let's call the RF-23. The RF-23 would certainly have been an ideal aircraft for this role, but with UAV's now providing so much reconnaissance capability, would there be a need for such an aircraft? Perhaps the aircraft is known as the EF-23 and is employed as a fast, stealthy ECM aircraft, flying ahead of a strike package to identify enemy radars, pinpoint their location and then data link the information back to the SEAD aircraft following on behind. Either way, I am convinced that the YF-23 formed the basis for a 'black' aircraft that is now in service.
Of course all of the above is, like everything else written about the SR-71 replacement. just speculation based on events. Disinformation is one of many methods used by those inside the 'black' world to ensure their secrets are not revealed until they're ready, so everyone who has ever written on this topic could well be very wide of the mark and barking up completely the wrong tree - me included. For all anyone knows the USA might have decided to undertake the SR-71 mission with stealthy UAV's instead of manned aircraft. Perhaps they've developed a photographic satellite capable of obtaining detailed images from geo-stationary orbit - who knows?
Sadly, the whole Area 51 / Aurora story has spawned a cottage industry which, in recent years, has largely been taken over by every conceivable form of crank, conspiracy theorist and general whacko. No authentic photo of the actual aircraft has emerged, but this has not deterred various weirdo's, who need to get a life, from publishing all kinds of fake photographs - a task within the capabilities of every schoolboy with a decent digital camera and a reasonable computer. There are also dozens of artful drawings of what the aircraft could look like, some reasonably sensible, others complete flights of fancy. In the end the simple fact is Fake 'Aurora' photo that nobody has any idea what the aircraft looks like, other than it has to conform to certain basic design criteria if it is to be capable of hypersonic performance. There's little doubt that eventually the full story will slowly emerge, but only when the US government decide the time is right. By then the technology that was used to design the aircraft will once again have moved on apace and so, when we do finally see what the SR-71 replacement looks like, the chances are that it's replacement will already have been flying for some time and will probably be in actual service - so the whole cycle of speculation will begin all over again.