Archive for May, 2019
The Great Hypersonic Race
The X-51A WaveRider. Photo: Mike Cassidy/USAF
China, the US, and Russia are each striving to be the first nation to develop hypersonic systems: aircraft and missiles that can cruise and maneuver at five times the speed of sound (Mach 5) or faster. The winner of this technology contest will have daunting military advantages. Such weapons promise the ability to hit targets from very long ranges, yet with such speed and surprise that defending against them is extremely difficult.
Hypersonic weapons could give those that possess them tactical capabilities with potentially strategic effects. Its potential disruptive effect on military operations—the ability to fly at a mile a second at Mach 5—is most often compared to that of stealth and precision weapons when those technologies appeared in the 1980s.
The consensus view is that China, so far, is winning the hypersonics race, largely through financial brute force. USAF Gen. Paul J. Selva, vice chairman of the Joint Chiefs of Staff, said in January that China has made hypersonics research “a national program”—a kind of Manhattan Project—and it is “willing to spend … up to hundreds of billions to solve the problems of hypersonic flight, hypersonic target designation and then, ultimately, engagement.”
Chinese state media announced in March, for example, that China is building a 265-meter long wind tunnel to simulate the environment from Mach 10 to Mach 25, which is to be complete by 2020. It already has tunnels capable of simulating conditions between Mach 5 to 9. Though the US has hypersonic tunnels, most are quite small, for tests lasting less than a few seconds.
Russia, meanwhile, announced in March that it is testing the “Kinzhal” missile, which president Vladimir Putin boasted can fly at Mach 10, has a range beyond 2,000 kilometers, can carry conventional or nuclear warheads, and can defeat any existing “or prospective” air defense system. Although many leading US technologists scoffed at the claim, US Strategic Command chief Gen. John E. Hyten confirmed to reporters at a Colorado space conference in April that both China and Russia are flight-testing hypersonic concepts, saying “you should believe Vladimir Putin about everything he said he’s working on.”
While Hyten said it’s a “different issue” as to whether those systems are deployed, “we … listen to what they say very closely, and none of what he did … [or] said surprised me.”
Russian air-launched Kinzhal hypersonic missile being carried on a MiG-31. Photo: Russian Ministry of Defense
TORTOISE AND THE HARE
The US is believed to have had a commanding lead toward fielding hypersonic systems until about five years ago. In 2013, the X-51 program, building on several previous projects, achieved more than 200 seconds of air-breathing Mach 5 flight, proving it could be done. The program then concluded and wasn’t immediately followed up. A number of US successor programs were either terminated for budgetary reasons or cancelled for experiencing failures, even though the technology is in many ways still in its infancy. Pentagon and congressional leaders in the last two years have decried the risk-averse defense acquisition culture that favors only “sure things” instead of gambling on chancy but potentially high-payoff research.
Most hypersonic research follows one of two main avenues. One leads to a “boost-glide” vehicle in which an aerodynamic shape is mounted on a rocket and accelerated to hypersonic speed. The vehicle then detaches and coasts to its target, able to maneuver but gradually bleeding off its energy as it flies.
The other main approach aims for an air-breathing vehicle also propelled to hypersonic speed by a rocket, but then an internal supersonic combustion ramjet—or scramjet—takes over. The vehicle separates from the rocket and propels itself through the atmosphere, taking in air to mix with and burn internal fuel and creating thrust, but without the rotors and compressors of a turbine engine. Complex shaping of the inlet, exhaust and combustion chamber, along with highly precise holes, ducts, and bypasses is necessary to make this approach work.
Underlying technologies for hypersonics include advanced computers that can calculate shapes and airflow, additive or 3-D manufacturing that can make the exotic shapes necessary for the inlets and ducting, and materials—metals and ceramics—that can withstand the extreme temperatures and pressures of hypersonic flight. There will also need to be guidance mechanisms that can function under those same stresses without being crushed or melted.
Leading US technologists believe either the boost-glide or air-breathing approaches will yield operational missile systems in under five years, and more test flights akin to the X-51—possibly secret—are forecast to take place this year.
A more advanced concept, generally considered 10 years away or more, would make use of a “combined cycle engine” approach. The objective vehicle would take off from a runway, accelerate through Mach 1, achieve hypersonic speed, carry out a mission—spying, show of force, or delivering weapons—and return to base for reuse. This goal is challenging because the qualities that make for an efficient engine in the subsonic and transonic regimes simply won’t work in the hypersonic regime, because of the different way that air behaves at those speeds.
Meanwhile, China is plowing ahead. The Pentagon’s new research and engineering czar, Michael D. Griffin, said in March that China has made 20 times as many hypersonic technology tests as the US has in the last five years.
Speaking at a McAleese/Credit Suisse defense conference just days after taking the top Pentagon R&E job, Griffin, the former head of NASA, said the US must demonstrate its resolve to lead in hypersonics. If the Chinese are unchallenged in this area, they could “hold at risk our carrier battle groups … [and] our entire surface fleet,” Griffin warned. “They hold at risk our forward-deployed forces and land-based forces.”
Lacking either a defense or an ability to respond in-kind, the US faces poor choices. “Our only response is either to let them have their way, or go nuclear.” And that, he said, is “an unacceptable situation for the United States.”
Hypersonic technology, Griffin declared, is his “No. 1 priority.”
In a discussion at the Hudson Institute in April, Griffin said there are ways to defend against hypersonics, but there’s only a brief window for doing so. Such missiles “are relatively fragile during their long phase of cruise flight” and are “fairly easy to destabilize,” Griffin noted. They also glow brightly in the infrared, because of the heat they generate, and “yes, they can maneuver, but they can’t maneuver in their cruise phase as easily as an interceptor.”
Presumed test model of secretive Chinese WU-14 hypersonic glide vehicle. Photo: CCTV
However, “if you let [hypersonic weapons] get into terminal phase, where we’ve observed that they can pull many G’s, then that becomes a hard target,” Griffin allowed. “If you allow an attacking vehicle to get close enough to begin its terminal dive …and [that] might be from 100,000 feet … you’re probably dead meat because that’s a very hard intercept problem… at that point.”
He noted that hypersonic weapons “overfly our air defense systems and underfly our missile defense systems. So China has, over the last decade, with great care, [become] capable of … holding our forward-based assets at risk.”
Those carriers and forward-based forces are strategic assets and the “means by which we project strategic power short of nuclear deterrence.” Without countering it, “we allow their tactical systems to leverage our ability to project strategic power.”
The US will have to develop means to defend against hypersonic missiles soon, Griffin said. The Missile Defense Agency (MDA) will have that responsiblity, not the Defense Advanced Research Projects Agency (DARPA).
By July, Griffin was expected to finish a new hypersonics roadmap that would rationalize and coordinate at least a half dozen projects within and between the Air Force, Army and Navy, DARPA, the Pentagon’s Strategic Capabilities Office, NASA, and defense contractors. Deputy Defense Secretary Patrick M. Shanahan told reporters in April that Griffin had just delivered “80 percent” of the plan and was working on the final version.
“The overlap of the technical challenges is pretty high,” Shanahan said of the various approaches being taken. The basic physics of getting to hypersonic speed and maintaining it, while preserving maneuvering capability, are common to the various approaches underway, he asserted. The Pentagon will look for synergy between the programs, seeking to consolidate them where practical, saving money but also sharing information. The services would integrate their own unique requirements as to whether their specific vehicles are air-, land- or sea-launched.
The roadmap, Shanahan said, will cross “10 technical domains” and determine the critical tests that must be conducted in the next five years “to achieve capability within the next decade.”
The document might just as well be called a “hypersonic prototype plan,” Shanahan said. The roadmap will also inform the Pentagon’s five-year spending plan.
Mark J. Lewis, director of IDA’s Science and Technology Policy Institute, a former chief scientist of the Air Force and a leading expert in hypersonics, said there are “a couple of characteristics I would want to see in a generic [hypersonics] roadmap.” Lewis is not involved in developing the plan, which is likely classified. He spoke to Air Force Magazine as a sidebar to an AFA technology podcast.
Concept for Lockheed Martin’s Reusable Hypersonic Vehicle. Illustration: Lockheed Martin
DON’T RULE ANYTHING OUT
First, Lewis said the plan should “build directly on past successes. Meaning, stop reinventing the wheel.” At least one successor program to the X-51, he said, largely repeats what that project already achieved, with some minor additions.
Second, he said, the roadmap “shouldn’t zero-in to a single technology solution. It shouldn’t be just air-breathing or just boost-glide. They have different strengths [and] weaknesses and different applications.” Necking down to a single, quick-and-dirty approach “to me, would be a wrong answer.”
He also advised that while hypersonics as a conventional strategic weapon may very well be what China is looking for, it doesn’t have to be that and, for the US, “the winning applications are not the strategic applications.”
The US could develop hypersonic air-to-air missiles, for example, that could destroy enemy aircraft at great distances, before they could pose a threat. There is also the potential for air-to-ground missiles covering 100 miles in as many seconds, offering opportunities to destroy enemy air defenses from standoff range. Given the extreme destructive force of an impacting vehicle traveling at Mach 6, a warhead might not even be necessary.
Such applications “are the ones most likely to be useful to the United States, frankly,” Lewis asserted.
Air Force Research Laboratory chief Maj. Gen. William T. Cooley, in a February interview, took issue with the characterization of some post-X-51 efforts as a virtual repeat of that program.
“I would say that’s not true and largely because of the people,” Cooley averred. “The same scientists and engineers who had been working on the X-51 are continuing to advance our hypersonics portfolio, and so they are well aware … of the data that was collected” on that program. “We’re advancing the ball forward,” he added, saying the X-51 was “a point design …to prove out our understanding and we’re building on that.”
The Pentagon is taking hypersonics much more seriously—budget-wise—than it did in the past. Boeing hypersonics expert Kevin G. Bowcutt, whose experience stretches back to the National Aerospace Plane project of the early 1980s, said in an interview that Pentagon funding for hypersonics after NASP “has had an oscillatory funding profile,” going up and down between $50 and $100 million a year. In Fiscal 2017, the Defense Department funded hypersonics to the tune of just $85.5 million, and that rose to $108.6 million in Fiscal 2018, but exploded to $256.7 million in the 2019 budget request. Congress has indicated its willingness to support that figure, and even add to it.
“This may be a ‘Sputnik moment,’ ” Bowcutt said of the sudden turnaround in both interest and financial support of hypersonics, driven by the prospect of being behind China and maybe Russia.
Boeing illustration showing first-generation conceptual design of a reusable hypersonic aircraft. Illustration: Boeing
The Air Force has been working with DARPA for several years on two hypersonic projects. One is the Hypersonic Air-breathing Weapon Concept, or HAWC, and the other is the Tactical Boost-Glide program, or TBG. The Air Force chose Lockheed Martin and Raytheon to develop its HAWC concept, while Lockheed is the prime contractor for TBG.
Additionally, the Air Force is launching two new prototyping efforts in the Fiscal 2019 budget, with $260 million: the Air-Launched Rapid Response Weapon, or ARRW, and the Hypersonic Conventional Strike Weapon, HCSW, which USAF pronounces as “Hacksaw.” The service awarded Lockheed Martin the HCSW contract in late April; it has an ultimate value of $928 million.
Steven H. Walker, head of DARPA, told reporters in March the renaissance in hypersonics funding has been gelling for several years. He said he pitched former Deputy Defense Secretary Robert O. Work a “National Hypersonics Initiative,” which Work largely supported.
“We did receive a budget increase at DARPA and in some of the services to do more in hypersonics,” Walker said. “I don’t think we got everything” the agency asked for, “but it’s a good first step.”
The funding will underwrite studying “what we want to do with these systems, how effective they can be, how affordable we can make them, and how feasible is the propulsion system, and the maneuverability and the materials that we bring to the table.”
Walker said protoypes will “start flying in 2019.” DARPA is also beginning a new program with the Army, called “Operational Fires,” aimed at increasing the range of some of the Army’s ground-launched missiles.
He said the Air Force’s time line for an operational prototype of a boost-glide system is “in the ’22-’23 time period, so it’s close.”
Walker also noted that DARPA is working with NASA on a program called the Advanced Full Range Engine (AFRE), which “is basically developing the combined-cycle propulsion system you would need for a reusable platform. And we’re making good progress.” The AFRE was originally planned to power a project called “Blackswift;” one of those projects that was terminated over the last half-decade.
The AFRE program is only planned for ground tests in the NASA Glenn “10 X 10” wind tunnel in Ohio, Walker said. It will, however, take an “off-the-shelf turbine engine, combining it with a scramjet” and get it up to a speed representative of Mach 2. The scramjet would then take over, and “having that overlap … you can actually take off like an airplane, fly up to Mach 6, do your mission, then come back down, and do it again.” DARPA awarded Orbital ATK (now part of Northrop Grumman) an AFRE contract in January.
FLIGHT TESTS NEEDED
Air Force Materiel Command chief Gen. Ellen M. Pawlikowski told reporters in May that investments are being made in new wind tunnels at Arnold Engineering and Development Center in Tennessee “to bolster our hypersonics capability.” NASA has been involved in this work as well, she said, as has the Test Range Management Center, so it’s “a whole community involvement in this.”
The work done is “revitalization of some facilities that we haven’t used in a while, bringing them up to speed,” and this is “critical to being able to reduce the demand on flight tests” which are far more expensive than ground tests, Pawlikowski said. It’s also “much harder to control the environment” in a flight test, so the ground facilities investment will help the US “build better models” and “enable us to get to ground truth data … faster.”
Flight testing, though, is essential. Friction and airflow separation are tricky problems to solve, and in the real world, computer simulation code “tends to break down. They become more guesses than actual reality,” Walker said, so in hypersonics, “you’ve really got to fly.”
Air-launching prototypes from test aircraft such as the B-52 allows quicker and cheaper testing than putting the test vehicles on “big ballistic rockets” launched from the ground, he said.
As to whether the US will develop a large, reusable hypersonic platform capable of serving as an ISR craft or an attack vehicle, Walker said, “If I have anything to do with it, we will have a program.”
Lockheed Martin made news in 2013 when it announced it was working on such a platform, which it dubbed the “SR-72,” touting it as an unmanned successor to the SR-71 spyplane that could be more responsive to pop-up ISR needs than a satellite. Earlier this year, Lockheed Vice President of Strategy and Customer Requirements Jack O’Banion made news when, at an American Institute of Aeronautics and Astronautics (AIAA) forum, he showed a picture of the SR-72, and said that without recent digital modeling capabilities, “the aircraft you see there could not have been made.” Asked for clarification—whether Lockheed has really built, past tense, an SR-72—the company would only say the concept is a “far term solution that will be made possible by the pathfinding work we are doing today.”
Boeing, which built the X-51 with Rocketdyne, lost out to Lockheed and Raytheon on the HAWC, but made news in January, showing its own futuristic ISR platform at an AIAA event. Bowcutt, in an interview, said the concept would be about the same size as the SR-71, but a scaled-down version about the size of an F-16 could prove out the concept.
Bowcutt described it as “the smallest, lightest reusable hypersonic vehicle we could design,” because there was no evidence the Pentagon was prepared to spend “a couple of billion dollars” on a full-up reusable hypersonic platform. It has been financed so far with some government seed money and Boeing’s own independent research and development funds.
He explained that the vehicle can be scaled up, because hypersonic combustion “is actually easier at large scale.” The secret lies in managing the “the amount of time the flow is resident in the engine or flameholder. And as you scale up, the time is higher; the speed of the air is the same, but it’s larger, so [air and fuel] is inside the engine and engine components for a longer period of time.”
The concept Boeing showed was notional. Its true inlet configuration was concealed for secrecy, Bowcutt said. It was inspired by the inlet configuration of the XB-70 Valkyrie, a supersonic bomber concept of the 1960s built by Rockwell, now part of Boeing. The platform as of late May had not been given an official name, but Bowcutt said that with proper funding, the combined cycle project could yield an ISR platform “in 10 years; call it the 2030 time frame.”
NOT NECESSARILY EXPENSIVE
Lewis said it’s probably a misnomer that hypersonic systems are necessarily very expensive. “If I’ve got a weapon that costs me twice as much, but it’s five times more effective, then I’m ahead of the game,” he said. However, even without that calculus, the idea that hypersonics equals high cost is “flawed.”
Yes, he said, “the materials are exotic. Yes, there’s an up-front [cost] that has to be amortized. But there are fewer moving parts in a hypersonic system; even in an air-breathing engine” because “it doesn’t have rotating turbomachinery onboard.” A hypersonic engine is mostly a carefully contrived space in which shockwaves and fuel injection do the work that, at lower speeds, must be done with fan blades and rotors. Hypersonics should be an affordable technology once producibility has been worked out and the “legwork” done, Lewis insisted.
Asked to place the international competitors in order of progress, Lewis said China is unquestionably in the lead in hypersonics.
“I think it’s an absolutely true statement that in terms of practical, fieldable systems, we are behind … by every metric I can construct,” Lewis said. This is true whether it’s in test facilities, projects, or even published papers (although the US is classifying many of the papers written in the US).
As for Russia, “it’s a little more complicated,” Lewis said. Russia and China “seem to have different emphases.” The Russians, he said, “keep talking about defeating our missile defense system,” but “our missile defense system isn’t aimed at them.”
TAILOR-MADE FOR CHINA
China’s interests, though, “are more tangible and practical. If I were looking to defend my territory—what I think of as my territory, my sphere of influence—hypersonic systems make a lot of sense.” Lewis added that hypersonics “factors very nicely” into China’s island-building campaign and expanding its outer defense line.
While China is probably not afraid “of the US Army, it probably does fear the US Air Force and Navy,” Lewis asserted. “If I wanted to hold the Air Force … and the Navy at risk, I’d have a hard time coming up with a better solution than hypersonic weapons.”
Lewis offered “a glimmer of hope” that the US can still come from behind and win the hypersonics arms race, however.
“I have yet to see a single concept or breakthrough from either Russia or China that I would consider to be seminal in any way. We still own the intellectual leadership in this area,” Lewis said. “Now, I don’t know how much longer we will, but if you look at all the creative ideas—everything from fundamental understanding of the field to the development of the field … the real intellectual heavy lifting …that’s all us, that’s all US.”
Other countries have simply “taken the ball and run with it,” he added.
However, he said countries pursuing new technologies are a lot like college students. As undergraduates, “they mostly parrot back information,” but as graduate students, “we expect them to think on their own. I tend to think countries follow a similar model. The first thing they do is copy what we’ve done, and then they start coming up with their own creative ideas.”
In his February speech, Griffin said he’s not interested in regaining “parity” with America’s hypersonics competitors. “I want to ‘see and raise’ them,” he said, achieving deterrence by restoring America’s ability to surprise and take the initiative. Acknowledging that there are still some who question whether hypersonics is indeed important or the Pentagon’s top priority, he said, “anyone who doesn’t see it that way, … I have no time for you.” He added that Secretary of Defense Jim Mattis and Shanahan agree with him, and, “I don’t care about people who can’t overrule me.”
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