Lockheed Martin SR-72
In the Lockheed Martin SR -72 is a concept for an unmanned hypersonic aircraft that is to perform at speeds of Mach 6 at high altitude ISR operations. It is being developed by Lockheed Martin Skunk in the works as the successor of the famous SR -71 Blackbird.
In the designation SR -72 is not an official identification of the U.S. Air Force.
After the SR -71 in 1998 was finally retired for financial reasons, there was a gap in the U.S. strategic reconnaissance between the large number of subsonic aircraft on the one hand and surveillance satellites on the other side. With the proliferation of drones in the context of the "war on terror" at first seemed no need for a replacement for the Blackbird to be necessary. However, the increasing use of anti-satellite weapons and the progress in the field of radar technology has led to the detection of stealth aircraft to (especially in connection with the upgrading of China ) that you drew on the concept of extremely high speeds again. The advantage of a Mach- 6 engine that can hold this speed even over a long period of time is that it can also penetrate into well-monitored and defended airspace, since the reaction time for the defender is extremely low. The first reports on the SR -72 came from the year 2007, with Lockheed Martin until 1 November 2013, the concept for the SR -72 officially introduced.
In order to reach speeds of up to Mach 6, Lockheed Martin developed since 2006 with Aerojet Rocketdyne an appropriate engine. Previous Mach 6 projects use ramjet engines that can work but only from speeds of Mach 3 to 3.5. Why have corresponding prototypes, such as X- 51, are brought to the necessary speed until a launch vehicle or a rocket booster. Since such a support system for operations would be too expensive, the focus of development in the SR -72 is that these appropriate on its own can achieve speeds. For Lockheed Martin falls back on the "turbine -based combined cycle " concept ( TBCC ): The engine should have a variable air flow, so this works at low speeds like a turbojet and high like a ramjet. Even the J58 engines of the SR -71 Blackbird work on a similar principle.
Lockheed Martin indicates that a possible Demonstrator in the size of modern fighter aircraft could be built by 2018, which is expected to reach Mach 6 for a few minutes to prove the basic functionality of the concept. A first prototype of the SR- 72 could then be built by 2023. A commissioning was not expected before 2030.