In a replay of cold war rivalries, a new missile race is shaping up but this time America and Russia are joined by India and China. All of these countries are rushing to develop hypersonic anti-ship missiles that threaten to reshape naval warfare and alter global balances of power.
It's all about who can design the fastest missiles with the latest engine technology.
American Tomahawk cruise missiles are powered by conventional turbofans, which are essentially compact versions of passenger jet engines. These propel the missiles at 880 km/h -- 70 per cent the speed of sound, or Mach 0.7.
Much faster speeds can be reached with a ramjet, which has no moving mechanical parts. Travelling at supersonic speed, air is rammed into the engine. This heats the air to ensure more powerful combustion with fuel further down the engine. Since ramjets only work at high speeds, however, they must first be accelerated by another system.
The Brahmos missile, co-developed by India and Russia, is a good example of the capabilities of ramjet-powered missiles. The Brahmos starts off with a conventional rocket, which falls away when the missile gets up to speed. Then the ramjet-powered stage with the warhead takes over, cruising at Mach 2.8 (3,400 km/h) for 290 kilometres. It can fly at an altitude of 15 kilometres, or just meters above the waves. This weapon is already in service with the Indian navy.
The high speeds of supersonic missiles leave little time for ships to deploy defensive countermeasures. This increases the likelihood of a missile slipping past a vessel's screen of defences -- but supersonic weapons can be stopped.
However, there is presently no reliable defence against the much faster next generation of anti-ship missiles. These weapons are designed to travel at hypersonic speeds -- greater than Mach 5, or 6,100 km/h -- and therefore present a much more lethal threat.
Hypersonic speeds can be attained with scramjets, which are similar to ramjets but with combustion occurring at supersonic rather than subsonic speeds. They are designed to ensure the high-speed air flow doesn't blow out the flames. The U.S. Air Force compares running a scramjet to "lighting a match in a hurricane and keeping it burning." Once again, the missile must first be boosted to operational speed by a conventional rocket.
India and Russia are working on the hypersonic Brahmos II, which is expected to be in service by 2013. Cruising at about Mach 6 (7,300 km/h), this scramjet-powered missile will carry six times more kinetic energy than a similar weapon at Mach 1.
It would, therefore, pack a much larger punch if used to slam through hardened bunkers or underground nuclear or biological weapons facilities. It can also be used against ships.
China is developing its own hypersonic anti-ship missile, the Dong Feng 21D. This isn't a cruise missile but rather a ballistic missile launched toward space and arcing back to Earth. The DF-21D is capable of hurtling down at speeds of about Mach 10 and covering a range of 1,500 kilometres.
Dubbed the "carrier killer," it is believed this new weapon would be used against American aircraft carriers to destroy U.S. naval supremacy in the western Pacific and block America from coming to the defence of Taiwan.
The technology behind the DF-21D is nothing new -- the weapon is a variant of a proven Chinese medium range ballistic missile. What is new -- and a potential game-changer -- is the possibility of precisely striking ships at long range with non-nuclear warheads. China, however, has yet to prove it can accurately hit a moving vessel with a ballistic missile falling at Mach 10.
The chief of India's navy is dismissive of China's anti-ship missile program. As reported by the Indian Express, Adm. Nirmal Verma said "Targeting ships on the high seas is not an easy task ... There are limitations in terms of maritime reconnaissance and long-range searches."
He added that it was a "complex problem" to use a conventional missile against a moving target on the high seas.
With enough time and resources, however, China could overcome these technical challenges and threaten America's crucial carriers with the DF-21D.
"China's ability to bypass America's robust air-defence capability and strike ships at sea with ballistic missiles could severely limit American naval power," according to Abraham Denmark and James Mulverson of the Center for a New American Security.
Newsweek quotes retired U.S. rear admiral and defence attaché to Beijing Eric McVadon as describing China's anti-ship weapons as "pretty daunting."
To counter these new weapons, America will need to rely on ballistic missile defence systems. The U.S. has invested heavily in such technology but it is still in its infancy and not fully reliable.
Directed-energy beams such as lasers can be countered with reflective materials and, for a slowly spinning ballistic missile, there would be little effect on any one spot. Furthermore, hypersonic cruise missiles and ballistic warheads are hardened with materials capable of withstanding the scorching heat from high speed flight.
The most practical defensive measure is to strike the incoming weapon with another hypersonic missile, the proverbial "hitting a bullet with another bullet." The United States has proven it can do this, albeit in controlled tests and with inconsistent results. Further ballistic missile defence research could be applied to dealing with threats posed by the DF-21D and hypersonic cruise missiles like the Brahmos II. However, a dependable missile defence system is a long way off.
The United States has its own hypersonic missile development program. The X-51A Waverider is designed to demonstrate scramjet technology for missiles and spaceplanes. The first test took place last May and lasted only about 200 seconds. The US Air Force, however, notes this marked the first flight of a practical hydrocarbon-fueled scramjet (the engine runs on a special jet fuel).
With this confirmed success, America appears to have taken the lead in the hypersonic missile race. The competition, however, isn't far behind and the stakes are high for America's position in the global balance of power. This was clearly explained by U.S. Secretary of Defence Robert Gates in his address to an Air Force Association Convention in 2009.
"When considering the military-modernization programs of countries like China," Gates said, "we should be concerned less with their potential ability to challenge the U.S. symmetrically -- fighter to fighter or ship to ship -- and more with their ability to disrupt our freedom of movement and narrow our strategic options. Their investments in... anti-ship weaponry and ballistic missiles could threaten America's primary way to project power and help allies in the Pacific -- in particular our forward air bases and carrier strike groups."
The race is on to develop the next generation of anti-ship missiles and reshape naval warfare -- and possibly dictate who will rule the waves.
Tom Simko is an engineer living in Brockville, Ont. He writes about aerospace for the Winnipeg Free Press.