Earlier this year, former U.S. Chief of Naval Operations Admiral Jonathan Greenert asserted that current ballistic missile defense technology would "reac[h] the asymptote of our limits” within “about ten years.” This fact stands in stark contrast to another cold reality: the offensive ballistic missile capabilities of U.S. adversaries only appear to be accelerating. Despite critics’ calls to shy away from investing in ballistic missile defense (BMD) to address this threat, the U.S. must continue to vigorously research and develop revolutionary BMD technologies. Otherwise, it risks allowing the balance of offensive and defensive ballistic missile capabilities to grow increasingly asymmetric as defensive technological progress becomes asymptotic.

As then-Commanding General of U.S. Army Space and Missile Defense Command Lieutenant General David L. Mann testified before the Senate Armed Services Strategic Forces Subcommittee last April, “many foreign ballistic and cruise missile systems are progressively incorporating advanced countermeasures” to defeat present BMD systems. For example, along with integrating “maneuverable reentry vehicles, [maneuverable independent reentry vehicles], decoys, chaff, jamming, and thermal shielding” technologies into its ballistic missile arsenal, China has constructed the world’s largest hypersonic wind tunnel to realize its goal of developing a hypersonic re-entry vehicle. Russia reportedly has plans to deploy its own hypersonic glide vehicle by 2020. For context, these hypersonic weapons can travel at speeds up to Mach 10 – more than double the speed of most current BMD systems.

In light of these developments, Keith B. Payne, head of Missouri State University’s Graduate Department of Defense and Strategic Studies, has postulated that “U.S. ICBM survivability will once again become a concern” if nothing is done. Given the central role, ICBMs play in nuclear deterrence, this is a scary prospect indeed.

How will the U.S. address the looming gap in BMD capabilities? The Missile Defense Agency (MDA) is developing three primary solutions: directed energy weapons, railguns, and “left-of-launch” capabilities.

Directed energy weapons (DEW), including lasers and high-power microwaves, provide one potential answer to the threat posed by hypersonic glide vehicles and other ballistic missile enhancements. DEW provides the ability to engage targets at the speed of light, but are limited to line-of-sight engagements and must overcome atmospheric attenuation caused by inclement weather or scattering from intentionally released high albedo gasses. MDA is actively working to overcome these challenges and eventually plans to “deploy lasers on high altitude, long endurance Unmanned Aerial Vehicle (UAV) platforms,” according to MDA Director Vice Admiral James D. Syring. Utilized for boost-phase intercept – which engages targets before they reach hypersonic speeds or enable other countermeasures – this system has the potential to revolutionize BMD.

Railguns, another platform currently being explored by MDA, also act to close the speed gap created by hypersonic attacks. Presently capable of firing projectiles reaching speeds beyond Mach 5, railguns allow for multiple attempts at destroying missiles as they approach. While current railgun systems face questions regarding the endurance of their components, the ability to engage fast-moving targets on their final approach remains a vital component of MDA’s full spectrum BMD system.

Finally, left-of-launch capabilities – methods meant to stop a missile attack before it can take place, including cyber weapons – “remain a novel adjunct to wider antimissile efforts,” according to former Vice Chairman of the Joint Chiefs Admiral James A. Winnefield Jr. In fact, there has been some speculation whether cyber weapons were used to thwart North Korea’s failed missile test on March 22 of this year. Regardless of the role left-of-launch tactics play in MDA’s BMD toolkit, the unlikelihood that the U.S. will be able to stay ahead of every attack means, according to Winnefield, there will always be a need for a “solid right-of-launch capability.”

None of this is to say that development and deployment of the BMD technologies described above will mark an end to the missile proliferation threat as we know it. It will not. However, it will narrow the gap between offensive and defensive ballistic missile capabilities, and provide a modicum of stability to regions presently outside of an effective BMD umbrella. If Admiral Greenert’s estimation is to be heeded, the U.S. has less than ten years until it lies outside of this umbrella as well. The clock is ticking.