The New York Times reports: “China’s Weapon Tests Close to a ‘Sputnik Moment,’ U.S. General Says.”
THEODORE A. POSTOL, postol@mit.edu
Available for a limited number of interviews, Postol is professor emeritus of science, technology, and national security policy at MIT. He said today:
1. “The potential of hypersonic vehicles increasing the threat to the United States is essentially zero.
“The United States is already threatened by ballistic missiles and nuclear armed cruise missiles. Neither of these systems can be defended against. In particular, there is no capability of defending against ballistic missile warheads as the ability to deploy decoys is so simple and the inability of current systems to determine the difference between decoys and warheads is so complete that for all practical purposes it is not possible to intercept ballistic warheads.
“Cruise missiles can occasionally be intercepted with quick reaction low-altitude defenses surrounding target locations, but the technology for this kind of defense is so limited, that such defenses cannot be used to provide a practical national defense.
“Thus, the threat of a hypersonic vehicle that is also not subject to meaningful defense does not change offensive nuclear strike capabilities in any meaningful way.
2. “In the case of the United States, we are blessed with extraordinarily capable space-based early warning systems which have the ability to detect hypersonic vehicles as they descend into the atmosphere and become heated to very high temperatures.
“We also have the capability to detect the launch and powered flight of ballistic missiles that would accelerate and deploy hypersonic vehicles towards the North American continent. This detection capability does not translate into any significant defensive capability, but it does mean that the United States would have warning that such an attack was underway.
“It is very difficult to think of a scenario where such an attack was not accompanied by the launch of ballistic missiles, but that is a different matter than what I am currently addressing.
3. “The early warning situation for countries other than the United States is problematic, and could introduce problematic instabilities with regard to accidental nuclear war.
“Hypersonic delivery vehicles are launched onto trajectories that do not rise to extremely high altitudes like those associated with ballistic missile warheads.
“Because the earth is round, the detection of hypersonic delivery vehicles by conventional ballistic missile early warning radars is almost nonexistent because of limitations imposed by the curvature of the earth. There is likely some capability to detect hypersonic vehicles using Over-the-Horizon Backscatter (OTH) radars, which reflect their radar beams off the ionosphere. However, these radars are limited to low frequencies (between 5 and 30 MHz) and depend on being able to reliably reflect radar beams off the ionosphere. The ionosphere is unstable and cannot be used with certainty and therefore potentially limits the utility of these over the horizon radars.
“This means that countries like Russia (and China), which do not have highly capable space-based infrared detection systems, will have extremely limited or no warning of attack by hypersonic vehicles.
“These threats to ground-based early warning radars and command posts will not materially add to the already serious threat to ground-based early-warning systems posed by stealthy cruise missiles (which are no longer limited due to the U.S. withdrawal from the Intermediate Nuclear Forces Treaty). The introduction of hypersonic vehicles will not change this currently dangerous situation as long as the numbers of such vehicles are relatively small and their accuracy does not begin to approach that of what is already achievable with ballistic and cruise missiles at this time. Nonetheless, there would certainly be some additional concern in countries that depend only on vulnerable ground-based warning systems that hypersonic vehicles could be used to attack ballistic missile early warning radars and key command-and-control installations as precursors to larger attacks.
“In summary, the introduction of hypersonic vehicles into the arsenals of the major countries may not introduce significant threats to nuclear stability that do not already exist unless they become numerous enough and sufficiently accurate to pose a credible zero or short-warning attack threat to the command-and-control and early warning systems of countries like Russia and China. Since ballistic missiles are far more accurate and versatile for purposes of large-scale attacks, it is probable that the countries demonstrating hypersonic vehicle capabilities will not deploy them in any significant numbers.
“As such, hypersonic vehicles are almost certainly an activity aimed at getting the attention of other countries by demonstrating technological prowess, as they will have little or no meaning in terms of adding significant nuclear-strike capabilities.”