By Bradley Perrett, Bill Sweetman, Michael Fabey
Source: Aviation Week & Space Technology
Credit: U.S. Navy
In the view of the U.S. Navy, the Mach 10 test of a hypersonic glide vehicle that China conducted on Jan. 9 reflects its predictions of future warfare. If and when China can put the technology into service, Beijing will have a weapon that challenges defenses and extends the range of its ballistic missiles against land and sea targets, but its offensive application is still some years away and depends on solving tough challenges in targeting and guidance.
The hypersonic glide vehicle (HGV) test appears to mark a step beyond China's anti-ship ballistic missile (ASBM) program, featuring a slower, shorter-range maneuverable reentry vehicle (RV)—and may point to a second-generation ASBM.
To some analysts, the test underscores the need for the U.S. to field directed-energy weapons, since interceptor missiles may be unable to handle targets that appear with little warning and then maneuver at speeds above Mach 5. The U.S. is developing directed-energy weapons, but it is not clear when they will be needed or available.
China's HGV, called WU-14 by the Pentagon, was launched into space by an intercontinental ballistic missile (ICBM) booster, after which it returned to the atmosphere to glide at up to Mach 10. The test was conducted within China, says the defense ministry in Beijing. On Jan. 19, another object was test-launched from the same space base at Taiyuan, says analyst Richard Fisher of the Washington-based International Assessment and Strategy Center. The Jan. 9 test was first detailed by Bill Gertz of the Washington Free Beacon.
China's achievement must be placed in perspective. The U.S. Air Force tested a Mach 15 HGV, the McDonnell Boost Glide Research Vehicle, four times in 1966-68, with two successful flights. A follow-on that represented an operational design, the McDonnell Douglas Advanced Maneuvering Reentry Vehicle (AMaRV), was tested in 1979-80. The tests did not lead to an in-service weapon because of a 1980s focus on basing modes, arms control and missile defense.
A conventional RV has no control mechanism and descends through the atmosphere on a predictable ballistic trajectory. Ballistic warheads were virtually invulnerable until the 1980s, but since then, ground and naval defense systems based on interceptor missiles have demonstrated the ability to defeat progressively longer-range (and therefore faster) incoming ballistic warheads, although only with great difficulty.
An HGV can execute a pull-up maneuver after entering the atmosphere and approach its target in a relatively flat glide. It will therefore be detected later than a ballistic warhead; there is less time to react to it or to shoot at it again after a miss. Because the HGV can maneuver aerodynamically, it is much harder to hit—the defensive missile must be able to outmaneuver it —and it can be guided with precision onto its target. Gliding extends the missile's range, so that the relatively vulnerable mid-course phase of its flight can occur farther from the target and its defenses.
A Chinese anti-ship ballistic missile, the DF-21D, is operational, according to the Pentagon, raising the possibility that HGV development will lead to a longer-range, more maneuverable anti-ship weapon. But the flight of the Chinese HGV is only part of a wider trend, says Adm. Samuel Locklear, commander of the U.S. Pacific Command. “The hypersonic test is just one of the things being looked at [when considering] implications for the future.”
At the 2014 annual Surface Navy Association Symposium Jan. 15, Locklear said, “a lot of nations are testing hypersonics. That particular test doesn't bother me. This is not about China. This system is going to proliferate. In the 21st century, somebody in the world is going to have that capability. Whether we become the best buddies in the world with China, we're going to face these challenges with somebody, somewhere in the world. It is what it is.”
The admiral hints that the U.S. has been following the WU-14's development. The Chinese were “able to go rapidly with the injection of technology” to get to the point of testing the missile, he says. “They have different processes that allow them to get to it faster.”
For example, purported DF-21D images that have appeared on the Internet show an RV similar to that of the Martin-Marietta Pershing II. The U.S. missile was deployed operationally in 1983, withdrawn in 1988 under the Intermediate Nuclear Forces treaty, and was similar in payload and range to the DF-21. Army training manuals for the Pershing II can be found on the Internet and it is extensively described in open-source literature.
The 1,400-lb. Pershing II RV was fitted with four control fins and designed to perform a Mach 8, 25g pull-up maneuver after atmospheric reentry followed by a 30-nm glide, during which its radar seeker imaged the target area. The guidance system matched the radar image to a pre-loaded template to provide high precision. Once the target was located, the weapon pitched into a terminal dive.
Higher-performance RVs and HGVs, such as the WU-14, tend to have different features, partly because the thermal environment is tougher: Not only are longer-range weapons faster, but the longer the glide segment, the greater the cumulative thermal load. The 1970s McDonnell Douglas AMaRV used a finless, biconic shape steered by trailing-edge flaps. The AMaRV concept was revived in mid-2000s Air Force studies of a Common Aero Vehicle, an intercontinental conventional strike weapon.
In 2011, the U.S. Army demonstrated a prototype of an Advanced Hypersonic Weapon, a fin-controlled vehicle designed for a fully endo-atmospheric trajectory. This was made possible with the help of high-temperature ceramic composite materials developed by Sandia National Laboratory.
Any ballistic missile could carry the HGV. Chinese ICBMs could use it to help ensure deterrence in the face of U.S. defenses. But shorter-range uses seem more likely, at least at first. “I suspect that the HGV is intended more for anti-ship or other tactical purposes than as a strategic bombardment system against American [or other countries'] cities,” says analyst Dean Cheng of the Heritage Foundation. “An HGV might help resolve difficulties of hitting maneuvering targets with a ballistic missile.”
A ground-bombardment missile is a likely first application, to avoid the complications of combining course correction with the new reentry technology, says Fisher. Chinese sources mention two possible early HGV weapon applications, he says. One is a rumored “DF-26,” apparently a DF-21 medium-range ballistic missile fitted with a maneuverable HGV warhead. “With an HGV, such a missile may be extended from 2,000 kilometers to over 3,000 kilometers in range,” Fisher says. “A second application would be to take the early DF-31 [ICBM] introduced in 1999 and extend this 8,000-kilometer-range missile to 12,000 kilometers,” he says.
Fisher sees an advantage in taking cheap, proven missiles and giving them greater reach with HGV warheads. The testing of the WU-14, and the prospective difficulty of intercepting it with missiles, greatly raises the urgency of developing U.S. directed-energy defenses, he adds.
Yet that depends on how soon the HGV is operational. At a conference this month organized by the Center for a New America Security, former Japanese navy commander Vice Adm. Yoji Koda suggested that in the future Chinese nuclear submarines would constitute the main threat in the waters near China, with ASBMs “intercepting incoming U.S. forces further out.” However, in his estimation, it could take 10-15 years before the ASBM becomes a major threat. An anti-ship HGV would be even more distant.
Hitting a ship with either a maneuvering or HGV warhead is not simple. The target has to be detected, identified, precisely located and tracked. Data must be passed from sensors to a command system, and perhaps to the missile, for mid-course correction. The missile's guidance system must be able to find the target within a zone of uncertainty that depends on how far the target can move in the time between location and intercept. The guidance system must resist jamming and discriminate between types of ships, such as carriers and destroyers. The fuse, if there is one, must not be disrupted.
U.S. Chief of Naval Operations Adm. Johnathan Greenert referred to that critical “chain of events” in May, and said the Navy was developing, or had developed, systems, means and procedures for disrupting or countering the DF-21D. As it did with the threat of Soviet missile-carrying Tu-22M aircraft in the Cold War, the Navy seeks to break early links in the chain, such as detection and identification, with maneuver and control of emissions—but Greenert himself cast doubt on that approach at the surface navy conference. Noting that the Navy needs a new emphasis on “electromagnetic maneuver warfare,” Greenert says, “we have to learn what our signature is when we use radar, communications and Wi-Fi. We think that we turn everything off and everything is silent. But we have done tests and we are not silent.”
Space-based radar, a leading candidate for searching large oceanic areas, has become less costly and more efficient, and there are hints of Chinese-Russian collaboration in this area. NPO Mashinostroyeniya launched its first Kondor-E synthetic aperture radar satellite on June 27 last year, to fill an order for an undisclosed customer. China's development of unmanned air systems with reduced radar cross sections, such as the joined-wing Soar Dragon, could also point to maritime surveillance uses.
At a briefing shortly before the surface navy conference, Jim Sheridan, Lockheed director of Aegis programs, was asked specifically about whether the Navy had approached the company about Aegis handling the DF-21D, and replied, “There's been some discussion. I'm not going into that area.”
In the event of a hit, analysts have often looked at the potential for a hypersonic missile to cause damage with kinetic energy alone. Andrew Davies of the Australian Strategic Policy Institute is skeptical, calculating that the energy of an inert object of a 500 kg RV at an impact velocity of Mach 6 would be comparable to the kinetic and explosive energy of a subsonic Boeing AGM-84 Harpoon, and only a quarter of Russia's supersonic Tactical Missiles Corp./Raduga P-270 Moskit. Raduga's Cold War “carrier-killer,” the Kh-22, is a 12,800-lb. weapon that hits at a speed above Mach 4 with a 2,200-lb.-class, shaped-charge warhead. However, classified studies carried out by McDonnell Douglas in the 1980s also showed that much smaller warheads—for instance, dispenser weapons with long-rod penetrators—would cause enough damage to a warship to put it out of commission, pending major repairs.
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