Earlier this month a handsome amount of $892,292 was awarded to Lockheed Martin by NASA to study the practicability of developing the SR-72, an unmanned hypersonic spy plane. First unveiled in November 2013, this super speed recon drone is believed to fly at speeds of Mach 6.0 or 4,500 mph. That is almost double the speed of its 50 year old predecessor Lockheed SR-71 Blackbird.
Officials at both Lockheed Martin Skunk Works and NASA Glenn Research Center are not talking about this recent award. According to Lockheed Martin website, Rocketdyne is working with them for the integration of a turbine engine, that will provide the speed of up to Mach 3 for the drone, with a supersonic ramjet engine or scram-jet, that will push the Mach 3 speed to a Mach 6.
Structurally speaking, the Scramjets are pretty simple. They contain no movable parts. There is an inlet, fuel injector, flame holder and a nozzle. Once the vehicle attains high enough speed, the supersonic air flow entering the inlet is compressed by the scram-jet, which is then mixed with the propellant and ignites everything in a matter of few milliseconds. The hot exhaust from the nozzle is not the fuel held by the plane, instead it’s the surrounding air, and this is why these are called ‘air-breathers.’
It’s been years, since the military has been experimenting on these designs. U.S Air Force tested a hypersonic Scramjet concept in between 2010 and 2013, called the X-51A WaveRider. Having a tungsten nose and an Inconel Nickel-Chromium Alloy Engine, the WaveRider was mounted on a rocket which was fired from the wing of a B-52. The WaveRider, having a cruise missile shape, was to dismount from the rocket and attain a high speed of as much as Mach 5.1.
The tests on the WaveRider were not as much of a success. The third and last test resulted in an out of control spin of the aircraft and disintegration of the aircraft after just 15 seconds of separation from the rocket. Still the Air Force is interested in whatever they can harvest from the project and gain experience, to develop the new High Speed Strike Weapon program.
According to the Lockheed website, the SR-72’s design will keep in account all those lessons learned earlier by different supersonic flight teams, namely rocket-launched Falcon Hypersonic Technology Vehicle 2 (HTV-2) program. Developed by DARPA, being part of what it called the Conventional Prompt Global Strike, the HTV-2 was an effort that was to accomplish the task of delivering a conventional weapon on any target on Earth within an hour.
Similar to the WaveRider, the test launches of HTV-2 were not much of a success either. The last one in August 2011, was able to attain the speed of Mach 20 (13,000 mph), but ended up blowing itself up over the Pacific Ocean, following the flight safety protocol on board, as the temperature of 3,500 degrees Fahrenheit generated by the plan was tearing it’s skin apart.
According to the remarks of U.S. Air Force Major Chris Schulz, the DARPA HTV-2 program manager, after the 2011 test, “We know how to insert the aircraft into atmospheric hypersonic flight. We do not yet know how to achieve the desired control during the aerodynamic phase of flight.” The Major was seen confident, that they’d overcome this issue.
According to Lockheed, development of SR-72 will be complete by 2030.
