An artist's rendering of the X-51A | U.S. Air Force graphic
The Air Force will likely have high-speed, long-range and deadly hypersonic weapons by the 2020s, providing kinetic energy destructive power able to travel thousands of miles toward enemy targets at five-times the speed of sound.
"Air speed makes them much more survivable and hard to shoot down. If you can put enough fuel in them that gets them a good long range. You are going roughly a mile a second so if you put in 1,000 seconds of fuel you can go 1,000 miles - so that gives you lots of standoff capability," Air Force Chief Scientist Greg Zacharias told Scout Warrior in an interview.
While much progress has been made by Air Force and Pentagon scientists thus far, much work needs to be done before hypersonic air vehicles and weapons are technologically ready to be operational in combat circumstances.
"Right now we are focusing on technology maturation so all the bits and pieces, guidance, navigation control, material science, munitions, heat transfer and all that stuff," Zacharias added.
Zacharias explained that, based upon the current trajectory, the Air Force will likely have some initial hypersonic weapons ready by sometime in the 2020s. A bit further away in the 2030s, the service could have a hypersonic drone or ISR (intelligence, surveillance, reconnaissance) vehicle.
"I don't yet know if this is envisioned to be survivable or returnable. It may be one way," Zacharias explained.
A super high-speed drone or ISR platform would better enable air vehicles to rapidly enter and exit enemy territory and send back relevant imagery without being detected by enemy radar or shot down.
By the 2040s, however, the Air Force could very well have a hypersonic "strike" ISR platform able to both conduct surveillance and delivery weapons, he added.
A weapon traveling at hypersonic speeds, naturally, would better enable offensive missile strikes to destroy targets such and enemy ships, buildings, air defenses and even drones and fixed-wing or rotary aircraft depending upon the guidance technology available.
A key component of this is the fact that weapons traveling at hypersonic speeds would present serious complications for targets hoping to defend against them – they would have only seconds with which to respond or defend against an approaching or incoming attack.
Hypersonic weapons will quite likely be engineered as "kinetic energy" strike weapons, meaning they will not use explosives but rather rely upon sheer speed and the force of impact to destroy targets.
"They have great kinetic energy to get through hardened targets. You could trade off smaller munitions loads for higher kinetic energy. It is really basically the speed and the range. Mach 5 is five times the speed of sound," he explained.
The speed of sound can vary, depending upon the altitude; at the ground level it is roughly 1,100 feet per second. Accordingly, if a weapon is engineered with 2,000 seconds worth of fuel – it can travel up to 2,000 miles to a target.
"If you can get control at a low level and hold onto Mach 5, you can do pretty long ranges," Zacharias said.
Although potential defensive uses for hypersonic weapons, interceptors or vehicles are by no means beyond the realm of consideration, the principle effort at the moment is to engineer offensive weapons able to quickly destroy enemy targets at great distances.
B-52 carries the X-51 Hypersonic Vehicle out to the range for launch test. | US Air Force photo by Bobbi Zapka
Some hypersonic vehicles could be developed with what Zacharias called "boost glide" technology, meaning they fire up into the sky above the earth's atmosphere and then utilize the speed of decent to strike targets as a re-entry vehicle.
For instance, Zacharias cited the 1950s-era experimental boost-glide vehicle called the X-15 which aimed to fire 67-miles up into the sky before returning to earth.
China's Hypersonic Weapons Tests
Zacharias did respond to recent news about China's claimed test of a hypersonic weapon, a development which caused concern among Pentagon leaders and threat analysts.
While some Pentagon officials have said the Chinese have made progress with effort to develop hypersonic weapons, Zacharias emphasized that much of the details regarding this effort were classified and therefore not publically available.
Nevertheless, should China possess long-range, high-speed hypersonic weapons – it could dramatically impact circumstances known in Pentagon circles and anti-access/area denial.
This phenomenon, referred to at A2/AD, involves instances wherein potential adversaries use long-range sensors and precision weaponry to deny the U.S. any ability to operate in the vicinity of some strategically significant areas such as closer to an enemy coastline. Hypersonic weapons could hold slower-moving Navy aircraft carriers at much greater risk, for example.
An April 27th report in the Washington Free Beach citing Pentagon officials stating that China successfully tested a new high-speed maneuvering warhead just last week.
"The test of the developmental DF-ZF hypersonic glide vehicle was monitored after launch Friday atop a ballistic missile fired from the Wuzhai missile launch center in central China, said officials familiar with reports of the test," the report from the Washington Free Beacon said. "The maneuvering glider, traveling at several thousand miles per hour, was tracked by satellites as it flew west along the edge of the atmosphere to an impact area in the western part of the country."
Scientists with the Air Force Research Laboratory and the Pentagon's research arm are working to build a new hypersonic air vehicle that can travel at speeds up to Mach 5 while carrying guidance systems and other materials.
Air Force senior officials have said the service wants to build upon the successful hypersonic flight test of the X-51 Waverider 60,000 feet above the Pacific Ocean in May of 2013.
The Air Force and DARPA, the Pentagon's research entity, plan to have a new and improved hypersonic air vehicle by 2023.
The X-51 was really a proof of concept test designed to demonstrate that a scram jet engine could launch off an aircraft and go hypersonic.
US Air Force photo
The scramjet was able to go more than Mach 5 until it ran out of fuel. It was a very successful test of an airborne hypersonic weapons system, Air Force officials said.
The successful test was particularly welcome news for Air Force developers because the X-51 Waverider had previously had some failed tests.
The 2013 test flight, which wound up being the longest air-breathing hypersonic flight ever, wrapped up a $300 million technology demonstration program beginning in 2004, Air Force officials said.
A B-52H Stratofortress carried the X-51A on its wing before it was released at 50,000 feet and accelerated up to Mach 4.8 in 26 seconds. As the scramjet climbed to 60,000 feet it accelerated to Mach 5.1.
The X-51 was also able to send back data before crashing into the ocean -- the kind of information now being used by scientists to engineer a more complete hypersonic vehicle.
"After exhausting its 240-second fuel supply, the vehicle continued to send back telemetry data until it splashed down into the ocean and was destroyed as designed," according to an Air Force statement. "At impact, 370 seconds of data were collected from the experiment."
This Air Force the next-generation effort is not merely aimed at creating another scramjet but rather engineering a much more comprehensive hypersonic air vehicle, service scientists have explained.
Hypersonic flight requires technology designed to enable materials that can operate at the very high temperatures created by hypersonic speeds. They need guidance systems able to function as those speeds as well, Air Force officials have said.
The new air vehicle effort will progress alongside an Air Force hypersonic weapons program. While today's cruise missiles travel at speeds up to 600 miles per hour, hypersonic weapons will be able to reach speeds of Mach 5 to Mach 10, Air Force officials said.
The new air vehicle could be used to transport sensors, equipment or weaponry in the future, depending upon how the technology develops.
Also, Pentagon officials have said that hypersonic aircraft are expected to be much less expensive than traditional turbine engines because they require fewer parts.
For example, senior Air Force officials have said that hypersonic flight could speed up a five- hour flight from New York to Los Angeles to about 30 minutes. That being said, the speed of acceleration required for hypersonic flight may preclude or at least challenge the scientific possibility of humans being able to travel at that speed – a question that has yet to be fully determined.