Hypersonic Lockheed Martin SR-72: the problem of technologies and solutions
Lockheed Martin hypersonic aircraft concept
According to various reports and sources, since the end of the 72s, Lockheed Martin, through its special Skunk Works division, has been developing a promising hypersonic aircraft. The machine, known as the SR-XNUMX, will be able to show the highest flight performance and solve special combat missions. Very little is known about this project, if it is indeed being developed. However, it is clear that the most modern and promising technologies and components will be needed to solve the set tasks.
Secret hypersound
The first mentions of the SR-72 project date back to 2007, and then it was reported that development had been going on for several years. Subsequently, new publications of an unclear degree of reliability about the goals and technologies of the project, as well as the timing of its implementation, repeatedly appeared in specialized publications. Until a certain time, there was no official information.
However, the statements of representatives of "Lockheed-Martin" did not clarify the situation. So, for a long time, it has been repeatedly mentioned that the company is conducting research into hypersonic technologies. In mid-2017, the media reported on the first flight tests, but then the development company indicated that such an aircraft could only be created in the early twenties.
Already in February 2018, information about plans to create the SR-72 was denied. At the time, it was argued that key technologies remain immature, and the development of the aircraft is impractical. However, in November of the same year, information from a source in Lockheed Martin appeared in foreign media, according to which the first flight of the SR-72 could take place until 2025. At the same time, they reported about the possibility of using the new aircraft as an interceptor armed with hypersonic air-to-air missiles ".
Concept revealed in one of the Pentagon reports
According to open publications, the SR-72 will be able to reach speeds of the order of 6M. High speed will ensure its combat stability, and therefore less attention will be paid to the glider stealth issues. Special engines are being developed for hypersonic flight. The aircraft can be unmanned or optionally manned.
The resulting SR-72 can be used as a high-altitude reconnaissance aircraft, well protected from the interception of modern air defense, or as an interceptor capable of quickly reaching the line of use of weapons. Impact functions are also not excluded. At the same time, combat modifications will be able to carry hypersonic weapons for various purposes.
New stealth
The SR-72 aircraft, capable of speeds up to M = 6, needs a special glider. It must accommodate all the necessary components and assemblies, the crew (optional) and the payload. In this case, the aerodynamic appearance must meet the requirements of hypersonic flight, and the structure must withstand the arising mechanical and thermal loads.
A glider that meets all these requirements will have to be created from scratch, although the design will be based on existing research and developments. The airframe can be made of heat-resistant steel alloys, titanium and other metals with the desired combination of strength and durability. It is also possible to use modern and advanced composites, ceramics, etc. The stability of the structure should be increased by cooling systems for surfaces and units experiencing high thermal loads.
One of the versions of the SR-72's appearance and the design of its power plant. Graphics Thedrive.com
In recent years, a large scientific work has been carried out in the United States to find the optimal options for the aerodynamic appearance of hypersonic aircraft. Obviously, the results of these studies are used in the hypothetical SR-72 project. Thus, the future aircraft may outwardly resemble some of the previous missiles.
Perhaps the exterior of the SR-72 will be formed by smooth or smoothly curved surfaces and clear edges. The aircraft can have a swept or delta wing, and the fuselage will have to receive bucket air intakes with a wedge. For obvious reasons, the entire payload, regardless of the tasks being solved, will be transported inside the fuselage.
It is clear that a glider of this kind will not be inconspicuous in the usual sense. In addition, in flight at hypersonic speed, the aircraft will unmask itself. However, this is said to be not a problem. Hypersonic flight in itself will become the main defense method. Intercepting a maneuvering target at 6M speed is at least extremely difficult - if not impossible with current or future technology.
Engine issue
A separate problem in the SR-72 project is the creation of a power plant. The characteristics of turbojet engines are insufficient for hypersonic flight, and ramjets require initial acceleration means. The use of rocket engines for various purposes is impractical. In this regard, it is necessary to develop a fundamentally new propulsion system.
It should be recalled that the SR-71 reconnaissance aircraft at one time used Pratt & Whitney J58-P4 engines with turbojet and direct-flow circuits. At speeds up to 1,6M, the main part of the thrust was created by the turbojet part, and further acceleration was carried out using the direct-flow one. At the same time, the engines were extremely complex and expensive, and also needed a special grade of fuel, special lubricants, etc.
Reconnaissance SR-71A landing. Photo by NASA
Since the mid-58s, Lockheed Martin and Aerojet Rocketdyne have been working on a promising J4-PXNUMX combined cycle engine. It included a direct-flow circuit capable of providing hypersonic flight. The profile press reported successful design and some testing, but the finished engine has not yet been presented. This fact can indicate both the lack of significant success and the unwillingness to disclose a breakthrough project ahead of time.
Equipment and armament
The manned or unmanned version of the SR-72 needs advanced electronic equipment for various purposes. First of all, it is necessary to ensure effective flight control at all speed modes, regardless of the presence of a pilot. Automation must monitor flight parameters and respond in a timely manner to dangerous changes. In particular, she will have to prevent overly energetic maneuvers and the occurrence of unacceptable overloads.
Special requirements apply to unmanned vehicles. During hypersonic flight, radio communication with the operator is practically impossible, and the autopilot must be able to independently fly the aircraft and solve the assigned tasks in the most critical modes.
The publications on the topic mention the use of the SR-72 as a reconnaissance agent. However, optical reconnaissance by aircraft forces at present and in the future does not seem appropriate. In addition, it is unclear how aerial cameras can take pictures through the plasma "envelope" around the aircraft. The presence of plasma virtually excludes electronic reconnaissance.
Application as a fighter or missile carrier looks more reasonable, although it leaves some questions. First of all, it is a drop in combat load. Launching a missile from an internal compartment at a supersonic or hypersonic speed is a very complex engineering task, on the solution of which the very possibility of the aircraft's combat use depends. In turn, braking to acceptable speeds before dropping negates the advantages of hypersonic flight.
Motorcycle nacelle SR-71. The movable cone was responsible for the distribution of air between the two circuits of the J58-P4 engine. Photo Wikimedia Commons
Uncertain Future
Thanks to research in recent decades, the United States has accumulated a certain amount of experience in the field of hypersonic technology. Right now, it is being implemented in projects for guided missiles and warheads for various purposes. In addition, according to various reports, the issue of creating a full-fledged aircraft on this basis is being worked out. However, missiles and warheads are already on display in open materials, while the aircraft design remains secret - if it exists at all.
It is easy to see that Lockheed-Martin and related enterprises have technologies, materials and ideas for solving part of the tasks within the framework of the proposed SR-72 project. At the same time, other questions of no less importance remain unanswered. Perhaps such solutions already exist, but they are not disclosed for reasons of secrecy. However, there may be another explanation associated with the lack of the necessary technologies.
Whether the Pentagon is supporting the SR-72 is unknown. Obviously, the multipurpose hypersonic aircraft is of great interest to the Air Force. However, the real combat capabilities and promising prospects of such a machine remain uncertain, as well as the feasibility of supporting the project.
Thus, the US hypersonic program in recent years has reached the stage of developing military systems, but so far it can show only limited results. Warheads and missiles of a new class have been created and are being tested, while a hypersonic aircraft, at its best, has not yet left the stage of designing and testing individual components. Whether Lockheed Martin and other organizations will be able to find all the necessary technology and build the expected SR-72 - time will tell.
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