The US Nuclear Posture Review : Prompt Global Strike System

Towards Global Zero: Seeking Conventional Alternatives ?

In Sep 2008, a report entitled “National Security and Nuclear Weapons in the 21st Century”, was jointly released by the US Department of Defense and the Department of Energy. This is an invaluable document that provides very interesting insights into the American thinking consequent to the US Nuclear Posture Review (NPR). This report highlights that, “Prior to the 2001 Nuclear Posture Review, force sizing considerations were based on target defeat criteria with the objective of rendering a nuclear armed adversary incapable of prosecuting conflict and thereby terminating conflict on terms favourable to the US. The primary American nuclear adversary during the Cold War was the USSR. The NPR’s decision to reduce Strategic Nuclear Forces Posture to just 1,700-2,200 warheads by 2010 was based primarily on a new, more cooperative, less confrontational US-Russia relationship. This was the key to adjusting the size of the Nuclear Force. The Strategic deterrent continued to be based on a triad of delivery means. By 2012, this was to be reduced to 450xMinuteman ICBMs (ageing- life extended to 2030), 14xOhio Class SSBMs-ballistic missile Submarines and 20xB-2 and 56xB-52 Strategic Bombers. The force downsizing was premised on the assurance that the adversary could not pose a threat that could potentially negate the entire force.

Problem of Legacy Warheads

It must be noted that these US nuclear warheads (especially the W-76 warheads for Trident III ICBMs and B-61 Gravity Bombs) are legacy warheads of the Cold War era. These warheads have to be constantly refurbished to enhance their service/shelf life. Beyond a point this may no longer be sustainable. “Very specifically the Directors of the American nuclear weapon laboratories have expressed concern about the ability to ensure confidence in the reliability of the legacy stockpile over the long term without nuclear testing.”

“Successive efforts at extending the service life of the current inventory of warheads will drive the warhead configuration further away from the original design base line that was validated by using US test data. Repeated refurbishments will accrue technological changes that overtime might inadvertently undermine reliability and performance.”

However without nuclear testing at some time in the future, the US may be unable to confirm the effect of accumulating changes to tested warhead configuration. The legacy nuclear warheads therefore may no longer be very reliable. All this represents huge sunk costs and could explain the apparent new US enthusiasm for a nuclear weapons free world. The Global Zero would do away with an unusable resource that needlessly complicates the strategic picture as small rogue states/organisations acquire these Weapons of Mass destruction (WMD) capabilities and add manifolds to the complexities of decision-making in such a scenario.

The amazing fact that this report highlights is the news that during the 1980s and 1990s, the US shut down and dismantled the Nation’s nuclear weapons “pit” fabrication plant at Rocky Flats Colorado in 1989. In 1991 and 1992, President George Bush halted all nuclear weapons development (these were an unusable resource anyway), and in 1993, President Bill Clinton announced an indefinite moratorium on nuclear tests.

Reliable Replacement Warheads (RRW) Program

The US Departments of Defense and Energy have now proposed an alternative to indefinite extension of legacy warheads. They have proposed a gradual replacement of existing warheads with warheads of compatible capability that are less sensitive to manufacturing tolerances and to ageing of material. This promises improved safety and security and elimination of many hazardous elements in existing warheads. Besides, Advanced Computer Modeling and experimental facilities will enable designs and certification of the RRW without physical testing. In the longer term RRW will be the key to sustaining confidence in the nuclear stockpile.

This very significant technical factor in US Nuclear Decision-making must be understood by analysts and decision makers in our country. The US today spends US$ 708 bn a year on defense. This is more than what the next 10 countries (in terms of military capabilities) put together spend. A nuclear weapons free world would theoretically suit the US as it would enable it to press home its conventional military capabilities generated by the RMA; (such a nuclear weapons free world would equally suit India with its superior conventional military capabilities in the South Asian region). The move towards going in for RRW however indicates a US hedging strategy. Nuclear stockpiles will be reduced and curtailed. However their complete elimination does not seem possible in the foreseeable future. President Obama said it would not happen in his lifetime and Hillary Clinton amplified that “it could be many lifetimes.”

Reducing Reliance on Nuclear Weapons

Because of their ultimate doomsday nature, nuclear weapons however are a non-usable resource in a situation of nuclear symmetry. They are at best a strategic hedge that assures that the adversary is never tempted to use such weapons against theNWS (Nuclear Weapons State).

Due to the tremendous uncertainties of the existing internal security environment and the chances of sudden changes in political intentions/technical surprises, the report concludes that nuclear weapons will continue to play a unique role in supporting US National Security.The US National Security Strategy Document of 2006 states that nuclear weapons “deter in a way that simply cannot be replicated by any other weapon.”

Paradigm Shift in Security Environment

However, the US study highlights that the Global Security environment has undergone a major paradigm shift. During the Cold War, the greatest security concern of the US was the nuclear capabilities of the Soviet Union. The threats from regional states like China and North Korea were considered “lesser included cases” that could be addressed by the capabilities deployed to counter the Soviet threat. The current Global Security environment is radically different. The US is the nexus of violent extremists and regional states of concern that have or seek to attain WMDs.

This radically transformed threat scenario calls for a whole new range of highly lethal, highly responsive and highly accurate response capabilities. It was in keeping with this threat analysis that the US Nuclear Posture Review of 2001 had sought to deal with this more complex security environment by creating a triad of capabilities that consisted of:-

• Strike Systems These would be nuclear, non-nuclear or kinetic and would include long range Precision conventional strikes.
• Defensive Active/Passive defensive systems – more specifically Ballistic Missile Defense Systems and Shields to guard against attacks by rogue states/non-state actors.
• Responsive Capacities In terms of improving the infrastructure for updating/replacing existing nuclear stockpiles to ensure their reliability and readiness.

The Review postulated that future offensive and defensive capabilities will increase the options available to national leaders to address a broader range of potential contingencies and will mitigate risks associated with significant nuclear reduction.

There has been an exponential increase in terms of modern Intelligence acquisition capabilities. Their reach, speed and levels of accuracy and responsiveness have been dramatically enhanced. There is a need therefore for a highly responsive weapon system that can provide rapid overwhelming respose capabilities against highly significant fleeting targets such as Osama Bin Laden in a cave complex in North Waziristan or intelligence about North Korea moving a nuclear missile to its launch site. These would require a rapid and pinpoint response capability of very high precision and lethality. Above all the conventional time window for response would be very small and fleeting.

Prompt Global Strike Program

The program under which Washington is developing its prompt response strategy is called Prompt Global Strike or alternately referred to as Conventional Prompt Global Strike. This capability could be based on a triad of three technology systems:-

• Trident Submarine Launched Ballistic Missiles
• Hypersonic Cruise Missiles (Air launched/mounted on Minuteman ICBMs (eg. Air Force A-51). The Hypersonic technology vehicle program is managed by DARPA, the conventional strike Missile Program by US Air Force Space and Missile Centre and the Advanced Hypersonic Weapons Program by the Army Space and Missile Defense Command respectively.
• Super Stealthy Strategic Bombers able to avoid detection by radar and thus evade ground to air defences.
• Orbital Global Strike Systems. In addition to the above three options that are being developed there is the option of Orbital Strike Systems.These would be placed in earth’s orbit and strike anywhere on the Globe in less than an hour.

The PGS Philosophy

The ambitious aim of this program is to be able to field a system capable of a high precision conventional weapon strike, anywhere across the world in just one hour. Such a PGS system, said US Gen James Cart Wright, would complement the forward deployed Forces of the US. These include:-

• The Air Expeditionary Forces These could be deployed within 48 hours.
• Carrier Battle Groups These can respond within 96 hours.

Thus today, unless you want to go nuclear, response times are usually measured in days, maybe weeks, till the military can respond with regular forces. The complexity of the existing security environment and enhanced RSTA (Reconnaissance, Surveillance and Target Acquisition) capabilities can generate situations, which calls for an urgent response that is measured in minutes. That is the basis of the US quest for a PGS system. However, the critical factor is that such a strike system presupposes the ability to acquire and transmit intelligence at such high speeds. On 28 Aug 1998, Osama Bin Laden had been located in Eastern Afghanistan. By the time he was targeted with cruise Tomahawk missiles, fired by the USS Abraham Lincoln Carrier Battle Group, he had already left that cave complex. With a top speed of 550 mph, the Cruise Missiles had taken two hours to do the 1,100 mile trip to the target area. It had missed Laden reportedly by less than half an hour. Keeping these performance parameters in view, the US military had begun its quest for a PGS from 2001 Nuclear Posture Review onwards. In the Bush era, the emphasis was on a Trident Nuclear Submarine based system.

The Trident Solution

The respected science magazine,Popular Mechanics gave details of this system. In 1988, Lockheed Martin’s Trident II D S Nuclear Ballistic Missiles entered service on Ohio Class submarines. In the PGS system, each submarine would be armed with 22 Tridents along with two retrofitted Trident missiles, each with four independently targetable conventional warheads. Gas pressure would eject the Trident from the submarine. Once the missile clears the water, the first stage ignites and burns in about 65 seconds. When the missile is locked on to targets at maximum range (roughly 6,000 nautical miles), this falls away. The second stage ignites for another 65 second burn that carries the missile 500-800 miles down range. The third stage now ignites for 40 seconds concluding the boost phase that lifts the Trident some 600 miles above the earth (the altitude of weather satellites). The post boost vehicle (or bus) now receives navigational updates and deploys four independently targetable warheads (that travel at 13,000 mph and have an accuracy of 30 ft). The warheads are GPS guided on decent by means of tiny flaps. Two types of warheads are planned:-

1. The Fragmentation version which shatters tungsten rods (each upto 12 times more destructive than a 50 caliber bullet). Anything within a 3,000 sq ft area is obliterated by this metallic storm.
2. The Bunker Busting version This has a bunker-busting metal “shock-impactor”, which relies on kinetic energy for its destructive power. This can tackle targets in deep cover/underground bunkers or caves.

The problem with this solution began with the strident response of the Russians and the Chinese. They warned that they would not be able to distinguish between the launch of such Trident missiles that were armed with nuclear/conventional warheads. This could trigger off accidental nuclear responses and result in a nuclear holocaust. Apparently the US Congress was thus alarmed enough to cancel funding for this program.

The Boeing XM-51 Hypersonic Wave Rider Program

The other programme in the PGS capability envelope is the Hypersonic Cruise Missile like the Boeing XM-51 missile. This missile is carried upto 45,000 ft by a B-52 bomber or a fighter jet. A rear mounted Army Tactical Missile System rocket kick-fires it to propel the 1,800 pound missile to Mach 4.5 and 100,000 ft. The rocket then drops away and the XM-51’s engine takes over. The shock waves produced by the hypersonic speeds open the internal inlet and compress the air. The compressed air mixes with JP-7 jet fuel and is ignited. This scram jet then pushes the missile to Mach 5 speeds (3,000 mph). In tests in the USA, Mach 10 (7,000 mph) speeds have already been achieved. A flight from Arabian Sea to Southern Afghanistan at Mach 5 would take just 20 minutes to destroy a target with just its own kinetic energy.

Minute Man Mounted Hypersonic Missile

Conventional bombers, says Gen James O’Cartwright, are however too slow and too intrusive for many global strike missions. Hence, as of 2010, the US Air Force is fielding a prototype modified Minuteman III ICBM with a maneuverable conventional warhead. This could even be a Hypersonic Cruise Missile. It is said that US$ 12 million were appropriated for this Conventional Ballistic Missile Program in 2007. However, once again the primary complication is based on the Ambiguity problem- how do the Russians/Chinese distinguish between a conventional/nuclear warhead armed ICBM? Various bizarre solutions have been suggested, eg. Keep the missile trajectory low so that it remains within the atmosphere. The second is to have separate launch sites for such conventional armed nuclear missiles, which the Russians and Chinese would be periodically allowed to inspect. Both the Russians and Chinese have highlighted strong chances of triggering off an accidental nuclear war with such conventional weapons.

However, on 11 April 2010, US Secretary of defense, Robert Gates indicated that the US already has a global strike capability. This could be based on the Trident system that was repeatedly shelved earlier. The hypersonic cruise missiles would be ready by 2015 and the Minuteman based conventional warhead by 2017 or so. Rick Rozoff reports that the Obama administration has requested US$ 239.9 million for a prompt Global Strike System across the military services in fiscal 2011. At this rate, the Pentagon would have spent some US$ 2 bn on PGS by the end of Fiscal Year 2015.

Conclusion

To conclude, the Prompt Global Strike (PGS) program aims at enabling the United States to plan and deliver military strikes anywhere on the globe in less than one hour. In technical terms, It aims to provide the US President with the ability to plan and deliver, limited duration and extended range strikes anywhere on the globe in less than one hour. The 2001 Nuclear Posture Review (NPR) formally introduced the global strike concept as part of a new triad that integrates conventional and nuclear force options into an offensive strike capability suited for the 21st Century. Gen Cartwright, the former Commander of the US Strategic Command had agreed in a 2006 congressional hearing that a PGS capability is necessary because, “it is unlikely that we will have forces in every place we need them at the crucial moment, when we have an opportunity to stop a WMD armed threat far from our shores.” The anchor premise that underlies the PGS concept therefore is based on two critical assumptions:-

• That elusive threats to national security can suddenly emerge (to include WMD threats by rogue states/non-state actors).
• The US must possess the capability to strike rapidly without relying on existing forward bases. These can respond in 48 to 96 hours or more, which is simply not good enough to deal with the new order of threats.

The primary concern of the US Congress in sanctioning funds for such PGS program is the Ambiguity problem or the fear of triggering off of an accidental nuclear war because of the inability of the other countries to distinguish between the launch of conventional/nuclear warhead tipped Trident or Minuteman Missiles. This is the current grey area in the PGS revolution that now seems around the corner. It seeks to reduce reliance on nuclear capabilities by creating equally responsive and destructive conventional military capabilities, which can respond within minutes to the significant intelligence, eg. Impending terrorist WMD threat/rogue state missile attack). However, such capabilities could equally provide the means to destroy/disable conventional air defense systems in sudden surprise attacks that set the stage for a more conventional invasion of an adversarial State. We are now looking at a whole new order of possibilities.

India has made impressive strides in the field of rocket science, missile capabilities and telemetry. We need to carefully study the technological advances now opening up in this field. These have graduated beyond science fiction and could be concrete capabilities by as early as 2015, if not earlier. In the face of repeated mass casualty terrorist strikes on our major population centres, do we need such a capability? What would be its impact in a conventional war scenario? Would it enable a crippling Counter- Force strike or a sudden crippling attack on our Command and Control centres and air-defense assets? These are critical aspects for study and analysis.