Lockheed Martin Is Developing A Hypersonic Spy Plane

No need to be stealth if you're flying at Mach 6.

SR-72 Concept Art

Where we're going, we don't need windows.Lockheed Martin

The SR-71 Blackbird, iconic supersonic Cold War spy plane adopted by the X-Men as their vehicle of choice, might finally have a replacement. The Blackbird was retired in 1999, and since then there's been a serious deficit in crazy-fast spy planes that inspire unimaginable wonder in children named Kelsey. Lockheed Skunk Works revealed Friday that it is developing the SR-72, designed to fly at twice the maximum speed of the Mach 3 SR-71. That's Mach 6, or six times the speed of sound. The biggest difference between the SR-71 and the SR-72 is that the new plane will could fly without a pilot on board; both manned and unmanned options are being considered.

Jet engines top out at around Mach 3. In 1990, the SR-71 set a speed record, flying at Mach 3.3 from Los Angeles to Washington, D.C., in barely more than an hour. To go faster than that, the SR-72 will use a scramjet, which takes super-compressed air, combines it with fuel, ignites it, and jets it out the back, sending the craft forward at supersonic or near-supersonic speeds. Scramjets go really, really fast, but because they need super-compressed air to work, they have problems at lower speeds. To solve this low-speed problem, Lockheed proposes a dual engine that shares a common air intake. A regular jet engine provides thrust from takeoff to Mach 3, and a scramjet takes over after that, propelling the plane from supersonic to hypersonic.

When the SR-71 retired, its high-altitude surveillance role was largely taken over by satellites. Yet satellites are not a perfect solution. Objects on the ground, like mobile missile launch stations, can move in between satellite orbits, but a hypersonic plane could spot them in time and then outrun any anti-air missiles they may fire.

The SR-71

The sound barrier was no match.US Air Force

Aviation Week has the full story. This nugget, describing the possibility of weapons on the SR-72, is particularly illuminating:

The SR-72 is being designed with strike capability in mind. “We would envision a role with over-flight ISR, as well as missiles,” Leland says. Being launched from a Mach 6 platform, the weapons would not require a booster, significantly reducing weight. The higher speed of the SR-72 would also give it the ability to detect and strike more agile targets. “Even with the -SR-71, at Mach 3, there was still time to notify that the plane was coming, but at Mach 6, there is no reaction time to hide a mobile target. It is unavoidable ISR,” he adds. Lockheed envisages that once the FRV has completed its baseline demonstrator role, it could become a testbed for developing high-speed ISR technologies and supporting tests of the SR-72’s weapons set, avionics and downlink systems.

Popular Science asked U.S. Air Force Lieutenant General Robert P. Otto, who has flown spy planes and worked in reconnaissance and surveillance for years, about the SR-72. He said he hadn't heard of the plane, but a high-altitude Mach 6 spy plane? That's a "tantalizing idea."

Indeed it is. Right now, Lockheed Martin is looking at a 2018 demonstration for a high-speed weapon the SR-72 could use, and a 2023 demonstration of the aircraft.

BONUS: In 1988, Popular Science investigated another proposed successor to the SR-71 Blackbird, called the Aurora. Read about the mysterious hypersonic plane in our November 1988 cover story, "Revealed! Mach 5 Spy Plane."

Update 11/5/2013 2:15: Corrected to include both unmanned and manned possibilities, and 2023 as the expected year of the flight test.