The SR 71:Epilogue

 An SR 71Blackbird of the USAF

     Much speculation exists regarding a replacement aircraft for the SR-71, most notably an aircraft identified as the Lockheed Aurora. This is due to limitations on the use of spy satellites which are governed by the laws of orbital mechanics. It may take 24 hours before a satellite is in proper orbit to photograph a particular target, far longer than the time requirements of a reconnaissance plane. Spy planes can provide the most current intelligence information and collect it when lighting conditions are optimum. The fly-over orbit of spy satellites may also be predicted and can allow the enemy to hide assets when they know the satellite is above - a drawback spy planes do not suffer. These factors have lead many to doubt that the United States military has abandoned the concept of spy planes to complement reconnaissance satellites.
     The fact that the SR-71 was still able to perform its duties with an excellent service record at the time of its retirement, that the need for its reconnaissance duties had not subsided at the time of its retirement, and that it was retired then pressed back into active service for a short time before being quickly retired again, give credibility to the rumors of a successor aircraft. Whether that aircraft is the Lockheed SR-91 Aurora is still unknown to the general public.
     Such a successor may be linked to a classified project rumored to exist at the Lockheed Skunk Works in the early 1980s to build a hybrid scramjet-powered reconnaissance aircraft capable of speeds near Mach 5. Production of the aircraft may have been incorporated into the 1988 Department of Defense budget, with the aircraft becoming operational around 1989. The fact that none of the systems suggested as replacements for the SR-71 are capable of effectively fulfilling the SR-71 duties, with regard to time sensitive reconnaissance and penetration of highly defended areas, gives additional weight to the existence of an undisclosed replacement. It is also possible that the SR-71 was retired due to shift from spy planes to low-speed "stealthy" unmanned aerial vehicles (UAVs) and a reliance on reconnaissance satellites.

Last Heard.....October 15, 1999
     A 1999 four-flight research series for the SR-71 Blackbird, with a 41-foot-long test fixture mounted atop of the rear section of the aircraft, wrapped up Sept. 27 at Dryden. The flights showed that the fixture barely impacted the SR-71's stability, handling and flying characteristics while soaring at Mach 3, or three times the speed of sound.

     The SR-71 stopped short of reaching one test point of going more than Mach 3 due to the failure of the liquid nitrogen system that was used to purge the test fixture. Without proper purge, there was a concern of overheating the fixture's internal systems. This purge system had proven to be very effective in past flights

      The cause of the purge system failure was understood and procedures were instituted to prevent this failure in the future. Although the two-hour flight did not reach Mach 3.2, the combined four-flight series proved that the SR-71 is a viable testbed for future technologies that need a high-speed, high-altitude flight environment.

     Data obtained on the previous flight to Mach 3 can be confidently extrapolated to Mach 3.2. Unlike wind tunnels that are constrained by its walls, the SR-71 airplane flies in actual atmospheric conditions, such as moisture and temperatures, at extreme altitudes and speeds making it an ideal testbed for supersonic flight.

NASA's Revolutionary Concepts (REVCON) project is one example of possible future use of the SR-71 as a testbed. The RevCon project encourages the development of ideas that could lead to revolutionary experimental planes.

The Pulse Detonation Engine (PDE), one of the first RevCon projects, is a revolutionary approach for future high-speed jet propulsion. The engine will have fewer parts, yet greater propulsion efficiency, resulting in lower maintenance and direct operating costs. A proposal to fly the PDE captive carry atop the rear section of Dryden's SR-71 Blackbird is being discussed.

Why are we still using Spy Planes? Brendan I. Koerner has something to say:Read it!