test got the liquid fuel engine going for five minutes.
The United States has apparently moved ahead with reviving its Cold War era hypersonic glide vehicle ballistic missile warheads. In late 2017 the U.S. revealed several active research projects like TBG (Tactical Boost Glide) and HAWC (Hypersonic Air-Breathing Weapon) which are similar in size and shape to the cruise missiles carried by bombers and launched from high altitudes into orbit or remain in the atmosphere but moving a hyper speeds (over 5,000 kilometers an hour). This is similar to the X-51A Waverider project that was halted in 2013 but not forgotten. The problem with X-51A was that it could not be made reliable enough. A 2010 flight test had the 8 meter (36 foot) long, cruise missile-like X-51 aircraft boosted to 3,300 kilometers an hour, using a solid fuel rocket, at which point the scramjet engine took over, and successfully operated for over two minutes, achieving speeds of nearly 6,000 kilometers an hour. This was the longest a scramjet had ever operated (the previous best was ten seconds). By 2013 the 4
What makes scramjets work is the compression of incoming air, without the use of a fan system (as in conventional jet engines). But while scramjets have been in development for half a century, the lack of adequate materials (that can handle the high heat and pressure), and adequate design tools, frustrated attempts to build workable, and reliable, scramjets. Scramjets have few moving parts, but must cope with very extreme conditions and the design challenges have proved very frustrating. The recent X-51 test, like all previous ones, ended with the aircraft crashing. The next step is to get longer hypersonic engine use, de-acceleration, and landing via parachute (and eventually an auxiliary engine.) Going beyond the 2013 test proved too expensive and time consuming to continue when there were cheaper alternatives available and these depended more on getting into orbit and letting gravity provide and maintain the high speed. It was definitely easier to achieve those high speeds with orbital technologies like TBG and HAWC. Or the new Chinese systems like DF-ZF.
Russia and the United States developed this orbital glide technology during the Cold War but the original work in this area was by the Germans during World War II. The U.S. and Russia both investigated the concept more during the Cold War but never deployed anything. In the 1990s the United States proposed reviving work on hypersonic glide vehicle for its Prompt Global Strike. This would put hypersonic glide vehicle warheads, using high-explosive and not nuclear explosives, on ICBMs producing a very expensive weapon that could hit a target anywhere on earth in less than an hour of the order being given.
In any event the United States successfully tested its version of the hypersonic glide vehicle in 2011 but with the defense budget shrinking at that point, the project was halted. This was also prompted by a 2014 hypersonic glide vehicle test that failed. Meanwhile Russia has resumed 2014 hypersonic glide vehicle development in 2013 but financial problems are preventing much progress. Then in late 2017 the U.S. Navy revealed that it had developed and tested a hypersonic glide vehicle warhead for its SLBMs (Sea launched ballistic missiles).
No one has deployed hypersonic glide vehicles in the form the Chinese appear to be using. Many believe the Chinese DF-ZF will mainly be used as an anti-satellite weapon program This situation got more interesting in 2014 when China revealed (apparently by accident) the existence of the DF-26 IRBM (Intermediate Range Ballistic Missile.) This one had a range of 3,500 kilometers and was based on the earlier DF-21. There had been reports of such a missile since 2007 and the DF-26C appears to have entered service sometime by 2013. The DF-26C is notable because it has the range to hit American military bases on the Central Pacific island of Guam. Armed with a maneuverable conventional warhead a DF-26 could take out key American military installations on Guam if enough of them were used at the same time. That would overwhelm existing American anti-missile systems there.
In early 2016 China revealed that they had perfected the technology for a maneuverable ballistic missile warhead. This came a little after it was revealed that since 2014 China had conducted six tests of a maneuverable gliding warhead for ballistic missiles. Five of the six tests were successful and this “hypersonic glide vehicle” was officially known as the DF-ZF. In effect this hypersonic glide vehicle is a warhead that can glide rather than simply plunging back to earth and is maneuverable enough to hit small moving targets in space or down on the surface. The DF-ZF was initially called WU-14 and developed further as China sought to perfect a version of the DF-21 ballistic missile that could hit moving warships at sea. DF-21 is a 15 ton, two stage, solid fuel missile that is 10.7 meters (35 feet) long and 140cm (4.6 feet) in diameter. The DF-21D (the carrier killer version) missile using the DF-ZF warhead is also more difficult for anti-missile missiles to hit and can also be used against low orbit satellites as well as land targets and moving warships. So far this combination has not been seen or confirmed. There appear to be guidance system problems which are taking longer than expected to solve. But a solution will be found, either by the Chinese or someone else.
As far back as 2008 there were rumors that the Chinese had reverse engineered, reinvented or stolen the 1970s seeker technology that went into the U.S. Pershing ballistic missile maneuverable warhead. This 7.5 ton U.S. Army missile also had a range of 1,800 kilometers and could put its nuclear warhead within 30 meters of its aim point. This was possible because the warhead was maneuverable and had its guidance system using radar. This kind of accuracy made the Russians very uncomfortable as it meant many of their command bunkers were suddenly very vulnerable. The Russians eventually agreed to a lot of nuclear and missile disarmament deals in order to get the Pershings decommissioned in the 1980s.
In early 2017, alarmed at the recent presence of American carriers off Korea and more regularly in or near the South China Sea, Chinese media ran stories claiming that the military had recently tested a ballistic missile that could hit a moving aircraft carrier at sea. While there is satellite photo evidence of similar tests (the most recent in April at a test site in western China) there is no evidence of a successful test against a moving target at sea. The missile in question is the DF-26C. The basic DF-26 entered service in 2013. The DF-26C is apparently still in development but is considered a credible future threat once the tech can be made to work in a realistic test.
There is also growing evidence that Chinese ballistic missile and warhead technology has evolved to the point where they could build a ballistic missile warhead that can hit U.S. carriers or small land targets over 3,000 kilometers away. The various components of such a system began to surface around 2006. By 2010 the U.S. believed that China had a version of their DF-21 ballistic missile with a conventional warhead that could hit a moving American carrier at a distance of 1,500 kilometers. There was no proof that such a system actually existed in a workable form. But over the last few years the necessary pieces of this mystery weapon began show up in working condition. The latest threat is not just to carriers at sea but to major American bases in the Pacific, particularly Guam.
Until 2013 there was no evidence that the DF-21D system had been tested using a maneuverable warhead. Then satellite photos showed a 200 meter long white rectangle in the Gobi Desert (in Western China) with two large craters in it. This would appear to be a “target” for testing the DF-21D, and two of the inert practice warheads appear to have hit the target. In early 2016 similar evidence appeared for a DF-26C warhead. But neither the DF-21D nor DF-26C has been tested under realistic conditions. American carriers are over 300 meters long, although the smaller carriers (amphibious ships with helicopter decks) are closer to 200 meters long. It appeared China was planning on using the smaller warships as well as carriers but do not yet feel confident enough to carry out a test at on, say, a recently retired large oil tanker operating under remote control over 2,000 kilometers from the Chinese mainland. The U.S. Navy believes such a test is not a matter of if but when. That apparently proved sufficient compelling to revive the American research that inspired the Chinese in the first place.