Comparing lasers, railguns and hypersonic weapons as potential gamechangers
A report compares directed-energy and railgun weapons systems with hypersonic systems in terms of technical readiness, investment strategies, and plausible applications of these systems by the separate armed services. These weapon systems may not be sufficient by themselves to accomplish a revolutionary change in American military operations, but they indicate whether such changes are possible and perhaps necessary to facilitate a third offset strategy.
A preliminary appraisal of one of those technologies-hypersonic weapons systems-frequently nominated as a "gamechanging" capability that might serve as the centerpiece of and a pathway toward a more complex and complete offset strategy. The US seeks to use technology advancement to maintain military dominance over Russia and China. Previously precision weapons and stealth technology were the sustainable gamechangers.
Today, hypersonic systems take two principal approaches: "scramjets" using a rocket to accelerate a vehicle to hypersonic speeds but then, hybrid-like, switching to an air-breathing engine to sustain that high speed, and rocket-assisted "boost-glide" systems. The scramjet uses three components: an inlet to draw in the air surrounding the vehicle, a combustor to burn fuel combined with that air, and a nozzle to release the pressurized air to maintain the vehicle's hypersonic speed.
The boost-glide approach to hypersonic speed uses multiple-stage rocket engines to take the vehicle into the upper atmosphere. Then that vehicle rapidly descends, skipping across the atmosphere to sustain its hypersonic speed to its final destination.
Hypersonic weapons overcome the tyranny of distance, time, and defenses that currently limits conventional power projection. Owing to their unprecedented speed, hypersonic weapons systems shorten the decider-shooter-target loop, compressing the time between actionable intelligence and weapons effects on a time-sensitive target. As concerns mount regarding an adversary's ability to push US power projection forces further from a prospective battlefield through "anti-access/area denial" (A2/AD) capabilities, hypersonic weapons can hold at risk multiple target sets from afar without the flight-time penalty of conventional subsonic munitions. Hypersonic weapons systems may also contribute to the strategic requirement for conventional prompt global strike.
Modern air defense systems including networked (and exported) Russian S-300 and S-400 surface-to-air missiles can deter nonstealthy aircraft from flying within 200 nautical miles of the battlefield. Shore-based batteries
with antiship precision-guided ballistic and cruise missiles might dissuade Navy ships from moving to forward offensive positions.
Hypersonic weapons systems could take the form of cruise missiles powered by a scramjet that flies several hundred miles in a matter of minutes or the form of conventional bombs or cluster munitions that reach hypersonic speed on a rocket booster and then glide at that speed over long ranges to impact a target with precision.
Hypersonic weapons would also be valuable in negating adversaries' investments in modern air defense systems. By striking such systems, these
weapon systems could act as a "tip of the spear," suppressing air defenses to allow the penetration of slower-moving, nonstealthy forces. These supersonic systems appear nearly invulnerable to those air defense networks, using their high speed, rather than stealthy design, to overcome existing detecting and tracking radars and command and control systems. For example, enemy defenses fortunate enough to detect a hypersonic weapon at a range of 150 miles would have only about two minutes to launch an interceptor-and that system would need to be capable of hitting a target travelling five times the speed of sound or faster. This hypersonic speed further compresses the adversary's decision-making cycle, allowing US forces to operate well within the adversary's observation and reaction loop
Perhaps as important as placing hypersonic weapons systems high on the agenda of the third offset is recognizing the likelihood that the competition in precision-guided munitions will also extend to high-speed weapons. As documented in the Mitchell Institute report, Russia and China are making major strides in hypersonic design, prototyping, testing, and investment. The Russian navy's efforts include testing the BrahMos II, a short-range hypersonic missile with speeds of Mach 5-7, as a replacement for its current supersonic antiship missile.
The Russians intend to test a new hypersonic weapon by 2020. Additionally, in response to the US "phased adaptive approach" of placing Aegis missile defense systems on destroyers in the Eastern Mediterranean and ashore in Romania and Poland to defend against a plausible Iranian missile launch, Russia is pursuing hypersonic missiles and munitions to thwart those systems.
Chinese hypersonic missile tests have focused on short-range systems, leading analysts to believe that China sees these weapons as underwriting their plans for regional hegemony rather than adding to their long-range strike capability.
Other Offsets: Directed-Energy Weapons and Railguns
In many respects railguns and directed-energy weapons systems seem just
as attractive as hypersonic weapons to those planners seeking to sustain America's precision strike advantage. All three increase the speed of flight of precision munitions to improve their ability to penetrate defended areas for use against time-sensitive targets. All three are in various stages of development and testing. The Department of Defense and the armed services planning on using these weapons systems face important
decisions in determining tradeoffs among technical readiness, cost, size, range, accuracy, and reliability. As Vice Chairman Selva observed, placing multiple bets on would-be breakthrough technologies is probably the right approach to pushing and sustaining the third offset. Those technologies that appear to be able to "change the pace and scope of the fight on the battlespace" will be those most deserving of future investment
True "offsets" in military affairs do not result from single technologies, and forces developed through both the first and second offset strategies relied on various weapons concepts and technologies. Eisenhower's New Look spawned the nuclear triad of long-range bombers, land-based intercontinental ballistic missiles, and submarine-launched ballistic
missiles. Within that triad, each of the three legs developed additional innovations, such as cruise missiles and multiple independently targeted reentry vehicles. Equally, the second offset-spurred by precision-guided munitions, wide-area sensors, and automated command and control systems that gave rise to conventional "reconnaissance-strike complexes" and the "revolution in military affairs"-featured combinations of systems. Unsurprisingly, a third offset strategy will also consider various technological candidates as game-changers in an effort to preserve US global power projection capability.
Two of those munitions programs worth a brief mention here, in effect complements to hypersonic weapons systems, are railguns and directed-energy weapons.
Electromagnetic railguns use electricity to fire inert projectiles placed between two rails at speeds of Mach 6 (4,500 mph). This enormous amount of energy is transferred to the target at impact over a range of roughly 125 miles. Suitable as a kinetic kill system for fixed land-based targets, the railgun is often portrayed in a defensive mode to shield valuable assets from a missile attack through its ability to rapidly fire its rounds for long times at an intense rate of fire. That rate of fire poses a challenge for the weapon system in terms of the continuing generation of large amounts of electricity. Therefore, the platform most commonly seen as hosting a railgun system is a Navy ship.
