In a 192-page report, commissioned by lawmakers in 2006, the National Academy of Sciences experts take issue with a Capitol Hill decision to eliminate this year's funding for the Conventional Trident Modification.
"The committee disagrees with the congressional decision not to fund testing of [the] CTM [missile] in 2008, and recommends instead that Congress fund" Conventional Trident Modification research and development "at a level sufficient to achieve early deployment if tests confirm system effectiveness," writes the group, composed of 18 national defense and nuclear weapons experts.
The Navy missile was to be the first weapon developed and deployed for a new mission called "prompt global strike," in which terrorist targets or rogue nations could be attacked within just one hour of a launch command. Currently, nuclear weapons are the only tools in the U.S. military arsenal available to hit urgent targets halfway around the world in such short order.
Lawmakers last year decided that the Navy project would be limited to basic research and development and must share a $100 million budget in fiscal 2008 with an array of other "promising conventional prompt global strike technologies." Critics on Capitol Hill cited concerns that, if launched from the same Ohio-class submarines that carry an identical nuclear weapon, a conventional D-5 ballistic missile might be mistaken for a nuclear salvo and elicit a violent response from other atomic powers like Russia or China.
In its report, the NAS Committee on Conventional Prompt Global Strike Capability argued that virtually any long-range weapon built for the mission might introduce some risk of the nuclear "ambiguity" that Congress seeks to avoid.
Calling nuclear ambiguity "an understandable concern" with the Conventional Trident Modification, the panel said that the risk of a conventional prompt global strike attack "being misinterpreted and leading to a nuclear attack on the United States could be mitigated and managed through readily available mechanisms."
These "cooperative measures" might include "providing information to bilateral partners about the [conventional prompt global strike] system, its operation and the doctrine for its use; immediately notifying of launches against countries; and installing devices (such as continuous monitoring systems) to increase the confidence that conventional warheads had not been replaced by nuclear warheads," according to the report, "U.S. Conventional Prompt Global Strike: Issues for 2008 and Beyond."
However, some critics of the conventional Trident option contend that land-based missile systems are better suited to reducing ambiguity and building confidence abroad.
"Some conventional prompt global strike systems, like some of the ground-based concepts, have gone out of their way to separate themselves from nuclear systems ... and [we] could open these to [international] inspections," one former military officer with considerable strategic policy experience said Friday. "The Navy submarine is nowhere near as open to inspection as the bomber or the ICBM."
The Army and Air Force have developed concepts for land-based conventional missiles that could be based at installations that house no nuclear weapons. Their launches might appear markedly different from those of current ICBMs, their warheads could be verified through on-site inspections and their activities could be monitored by spy satellites, said the former official, who was not authorized to address the matter publicly and requested anonymity.
The National Academy of Sciences panel found there are a number of "credible scenarios" in which a prompt global strike weapon might be useful, and noted that there are multiple future technologies that might augment or replace a submarine-based ballistic missile for the mission.
Threats might include "a ballistic missile launcher poised to launch a nuclear weapon at the United States or at an ally," a "gathering of terrorist leaders or a shipment of weapons of mass destruction during a brief period of vulnerability," or "an adversary's command-and-control capability as the leading edge of a broader combat operation," the report states.
"In light of the appropriately extreme reluctance to use nuclear weapons, conventional prompt global strike could be of particular value in some important scenarios," according to the science panel, "in that it would eliminate the dilemma of having to choose between responding to a sudden threat either by using nuclear weapons or by not responding at all."
The panel describes seven potential weapon systems that might be capable of undertaking the mission, including a couple of concepts that the committee itself developed:
- Existing systems: These include tactical aircraft, cruise missiles, armed unmanned aerial vehicles and bomber aircraft. Any of these would have to be deployed within range of a surprise threat to be successful at hitting the target within a 60-minute time frame.
- Conventional Trident Modification: The Navy concept involves converting two D-5 missiles on each of the Navy's 12 deployed ballistic missile submarines from nuclear- to conventionally armed. Available as early as 2011, each missile could carry as many as four re-entry vehicles with precision-targeting capability.
- Conventional Trident Modification-2: This committee concept calls for a missile that uses just two of the D-5's current three rocket stages, allowing for a bigger payload and additional options for the kind of munitions delivered. This version, which could be ready by 2013, would still achieve the weapon's objective 4,000-nautical-mile range, according to the report.
- Submarine-Launched Global Strike Missile: The Navy's mid- to long-term concept would be launched from so-called "SSGN" Ohio-class submarines, converted for conventional missions. This intermediate-range weapon, deployable before 2015, could carry a single, heavy warhead for attacking some hard targets or, like the CTM missile, could dispense kinetic-energy projectiles against buildings, vehicles or human targets.
- Conventional Strike Missile-1: This Air Force concept for a boost-glide weapon would launch like a ballistic missile from U.S. land installations and then fly at hypersonic speeds into its targets with considerable range and maneuvering capability. It could carry payloads similar to the Submarine-Launched Global Strike Missile but might not be available until 2016 or later.
- Conventional Strike Missile-2: This committee concept is for a variant with longer glide time than the initial CSM weapon, allowing extended range and increased capability to dispense multiple munitions, the document explains. Such a weapon, potentially available between 2018 and 2024, might also be able to dispense intelligence-gathering modules or offer re-attack capability, among other features.
- Hypersonic Cruise Missiles: Calling these concepts "long-term alternatives," the panel said such fast weapons could be launched from long-range aircraft, or deployed at sea or in foreign nations. Possibly available for fielding between 2020 and 2024, hypersonic cruise missiles might offer "considerable capability" for dispensing smart munitions or surveillance modules, the report states.
The committee addressed additional concerns about the prompt global strike mission, including some critics' view that detailed and reliable intelligence is rarely available to support a short-notice attack. In light of such worries, a fielded weapon should "be employed only on the order of the president," the panel advised.
Committee members also recommended that the U.S. government undertake "a comprehensive study of the military and diplomatic implications" of fielding and potentially using conventional prompt global strike capabilities.
The assessment should consider "factors such as the potential for inappropriate, mistaken, or accidental use; the implications for nuclear deterrence and crisis stability (including ambiguity considerations); the impact of [weapon] overflight and debris [potentially affecting foreign nations]; and the implications for arms control and associated agreements," the panel states.
The publication was preceded by an interim letter report in May 2007. Friday's document is the NAS committee's final report, according to the panel.