* Although US missile defense programs have risen and fallen, at no time has the issue gone completely silent. In the 1990s, new missile defense programs were initiated, with one track pursuing "theater missile defense (TMD)", and another, more controversial track pursuing "national ballistic missile defense (NMD)".
* The reason for interest in TMD systems from the early 1990s was Saddam Hussein's use of Scud TBMs in the Gulf War, and the seemingly impressive ability of American Patriot missile to hit the Scuds. However, though during the war the US Army claimed "100% effectiveness" in intercepting Scud missiles, their own postwar analysis cut their claims in half. A team of researchers from the Massachusetts Institute of Technology (MIT) challenged even these results, claiming that analysis of video footage of the intercepts showed no evidence that the Patriots had managed to hit even one Scud. As is typical of missile defense politics, the debate was long and often hot.
Whatever the case, the Gulf War demonstrated the threat of TBMs missiles to the US military and the ineffectualness of existing defense systems. Even Patriot advocates admitted that the missile was originally designed to shoot down aircraft, not missiles, and had been enhanced to provide only a limited anti-missile capability, mostly through a series of software changes.
The Patriot is built by Raytheon. The Patriot variant as used in the Gulf War is designated the "MIM-104C Patriot Advanced Capability 2 (PAC-2)". It is 5.2 meters (17 feet 1 inch) long, has four tailfins with a span of 87 centimeters (2 feet 10 inches), weighs 914 kilograms (2,015 pounds), and has a range of at least 70 kilometers (43 miles). The PAC-2 is carried and launched from a trailer, known as the "M901 launch station (LS)", with the trailer towed by a "HEMMT" heavy field tractor-truck. Each M901 stows four missiles. A Patriot battery includes:
The Patriot PAC-2 uses a proximity-fuzed warhead that detonates when it comes near the target. In use against Scuds, the Patriots generally seemed to have just thumped a missile that was falling out of the sky anyway. In 1992, after the Gulf War, minor changes were instituted in a "Quick Response Program (QRP)" to improve the guidance and launch systems for greater effectiveness.
* The threat of TBMs and the limitations of the Patriot has led the US military to investigate TMD systems to protect combat forces in a war zone, with the design effort mostly under the umbrella of the BMDO.
The US Army developed a refinement of the venerable Hawk anti-aircraft missile to provide a limited defensive TMD capability, but the main focus is on a new version of the Patriot, designated the "MIM-104F PAC-3", that was designed from the outset to attack missiles with an HTK vehicle. PAC-3 has been phased into service in the form of software, guidance, and system upgrades to the existing PAC-2 systems, but the ultimate goal of these changes is support for the new PAC-3 missile.
The Lockheed Martin PAC-3 missile is an updated version of the Lockheed Vought "Extended-Range Interceptor (ERINT)" missile, which scored hits on missile targets in tests in 1993 and 1994. PAC-3 is effectively a slightly stretched ERINT with an improved guidance system, and has proven accurate in recent intercept tests. The PAC-3 is 5.2 meters (17 feet 1 inch) long, has a diameter of 25 centimeters (10 inches), has a tailfin system with a span of 48 centimeters (1 foot 7 inches), weighs 318 kilograms (701 pounds), and has a range of 20 kilometers (12.4 miles). The tailfin system, consisting of a set of cruciform fixed fins followed by maneuvering fins, is used for coarse flight control, while the forward section of the fuselage is ringed with 180 small solid-fuel thrusters for agile maneuvering.
The PAC-3 is fired from the same launch station as the PAC-2, though a launch station can accommodate 16 PAC-3s in contrast to 4 PAC-2s. The PAC-3's warhead can optionally release 24 steel slugs to increase kill probability when engaging an aircraft or cruise missile.
The PAC-3 is equipped with a millimeter-wave radar seeker linked to a processor that not only computes the interceptor's trajectory, but also matches the incoming warhead with a library of known warhead types to determine the optimum attack procedure. Although the PAC-3 has its own guidance system, it has an RF data link to maintain contact with the launch control center.
The Army is also emphasizing the usefulness of PAC-3 for cruise missile defense. While cruise missiles are much slower targets than a TBM, they are generally stealthy and fly low to the ground. Developing a seeker system that can pick such a target out of the "ground clutter" is tricky, but the PAC-3 has demonstrated the ability to destroy cruise missiles in tests.
Lockheed Martin completed development of the PAC-3 in late 2001, having performed 12 successful tests in 12 shots, and the Army took over evaluation testing at that time. A decision was made to deploy the PAC-3 in early 2003, with 55 in service at the start of the Anglo-American invasion of Iraq in the spring of 2003, during which a number of PAC-3s were fired. PAC-3s have also been deployed to South Korea to defend the country against North Korean TBMs.
The US Army is now working on an improved version of the PAC-3 under the "Missile Segment Enhancement Program (MSEP)". The primary improvement will be a larger solid-rocket motor that will double the range against air-breathing threats and improve range by 50% against TBMs. It will have larger fins and a datalink system to provide data on engagement results. All PAC-3s are now being brought up to MSEP standard.
* The Netherlands and Germany are obtaining the PAC-3; the missile has been the centerpiece in a collaborative program between the US, Italy, and Germany designated the "Medium-Extended Air Defense System (MEADS)". MEADS was defined as a next-generation follow-on to existing Hawk and Patriot SAM systems, focused on developing a mobile tactical launch and control system built around the PAC-3 that will be more capable, reliable, and easily transported than the current Patriot system. Work on MEADS has been conducted by a consortium of Lockheed Martin, Alenia Marconi Systems, and EADS. However, the US pulled out in 2011; the Americans have continued to provide funds for development of a demonstration system, but have no intent of fielding MEADS themselves. Whether the other members will attempt to field it remains to be seen.
BACK_TO_TOP* The Patriot PAC-3 is intended as a last-ditch "lower tier" defense against incoming missiles at an altitude of 20 kilometers (12.5 miles) or less. The US Army also initiated a "Theater High Altitude Air Defense (THAAD)" system as an "upper tier" defense to hit incoming missiles at higher altitudes, from 40 to 100 kilometers (25 to 62 miles), with Lockheed Martin as the prime contractor. The program was later absorbed into BMDO and recast as "Terminal High Altitude Area Defense".
THAAD is a finless, spike-like missile with a length of 6.2 meters (12 feet 4 inches) and a launch mass of 900 kilograms (a ton). THAAD follows in the steps of a much cruder system named the "Exoatmospheric Reentry Vehicle Interception System (ERIS)" that was tested in the early 1990s, which was test fired twice and failed both times. ERIS was not an operational system in any case. The launch system was improvised from the second and third stages of a Minuteman missile, while the kill vehicle weighed hundreds of kilograms and featured a seeker that took a half hour to cool to operational temperature.
THAAD's kill vehicle, in contrast, weighs tens of kilograms and cools down immediately after launch. As currently envisioned, a THAAD defense systems is alerted to an incoming missile by orbiting satellites with infrared sensors. Once the incoming missile comes within range, the interceptors use ground-control radars to lock onto the target. THAAD's ground-control radar is a high-frequency X-band system designated the "AN/TPY-2", built by Raytheon, which can provide a detailed radar image of the target.
THAAD interceptors are fired from launchers carried on HEMTT four-axle heavy trucks, with each launcher stowing eight missiles. The launch system is designated "M1075". A typical THAAD battery will have nine M1075s, two command centers, and a single AN/TPY-2 radar. The mobile command centers have datalinks to allow them to hook into a wide-area defense system.
After launch, THAAD is guided to the vicinity of the target by the missile's autopilot, with course corrections as determined by satellites and the AN/TYP-2 X-band radar relayed over a datalink. Once the interceptor reaches an altitude of about 40 kilometers (25 miles), the booster portion of the missile falls away, with the hit-to-kill vehicle continuing on an intercept course. The kill vehicle is controlled by thrusters ringing its center of mass. When it reaches a certain range from the target, the kill vehicle opens a seeker head with a gimbaled infrared imaging array. The seeker can identify the warm target against the cold background of space, and its processor uses the image to direct a collision course optimized for the type of target. THAAD uses an infrared seeker because it attacks targets above the weather, while the lower-altitude PAC-3 uses a millimeter-wave radar seeker to locate targets in clouds.
The range of THAAD is estimated at 200 kilometers (125 miles), with the missile able to perform intercepts at up to altitudes of 150 kilometers (95 miles). One or two THAADs would be fired to try to destroy the target at high altitude, and if they failed, several PAC-3s would be fired to destroy it at closer range. BMDO officials do not claim they can kill a single incoming warhead with a single missile, stating that "you need more than one shot to do it."
* That's the plan. In reality, while PAC-3 tests have gone well, tests of THAAD did not go smoothly at first. Early THAAD tests from 1995 were consistently failures, leading to an investigation and considerable reengineering that put flight testing on the back burner for a few years. Tests were resumed in 2005, with the trials proving much more successful. THAAD attained initial operating capability in 2009; a battery was set up in Hawaii to deal with potential missile attacks by North Korea.
Strong consideration is being given to development of a more powerful booster rocket, with a diameter of 53 centimeters (21 inches) as compared to the existing 37 centimeters (14.5 inches). The new booster would provide enhanced range.
BACK_TO_TOP* An issue with THAAD is that it encourages visions of an NMD system. Since a TMD system is intended to protect a battle area, there is no reason exactly the same system cannot be used to protect a small country. In fact, Israel and the US are collaborating on an upper-tier interceptor missile named "Arrow 2", which could possibly be used together with the PAC-3 to defend Israel from ballistic missiles, with Iran seen as the prime threat.
The original Arrow 1 was flown in the early 1990s but prove unsuccessful, with work then refocusing on the lighter, faster, and more agile Arrow 2. The first operational Arrow 2 battery was deployed in the spring of 2000. It appears to be a two-stage missile with capabilities intermediate between the Gulf War Patriot PAC-2 and THAAD, with longer range than the Patriot but a proximity fuzed warhead instead of an HTK vehicle. However, in a number of tests against TBM targets, the Arrow actually performed a direct hit much more often than not.
The Arrow 2 is launched from a trailer-mounted canister, with six canisters per trailer, and works in conjunction with a "Green Pine" active-array X-band radar system, which not only targets the incoming ballistic missile, but also identifies the missile's launch coordinates for a rapid counterstrike against the mobile missile launcher. The primary threats the Arrow 2 is designed to counter are Syrian Scud-D TBMs and the Iranian Shahab IRBM.
Israel originally intended to set up three separate Arrow 2 batteries, but decided later to consolidate and place all the command and control assets in a single defense center, though missile launchers are distributed in various locations. Officials say that the idea of setting up separate batteries ran into troubles with coordination between the three sites, but cost may have played a role as well.
The Arrow 2 has been improved through a series of "blocks", though the details are unclear, while an extended range "Super Green Pine" radar is now replacing the original Green Pine. In 2008, work on an "Arrow 3" was announced, with this weapon more along the lines of THAAD, with greater reach and a hit-to-hill warhead. It does not appear that Arrow 3 has been tested yet. The USA has worked closely with Israel on the Arrow program.
* Along with the potential threat of Iranian missiles, the Israelis have the active threat of bombardment by relatively small rockets launched by Palestinian Hamas and Lebanese Hizbullah fighters. Rafael of Israel is working on a program designated "Iron Dome" to develop short-range interceptors to destroy short-range rockets and artillery shells. Iron Dome will consist of a radar and control system linked to a battery of interceptor missiles.
The Iron Dome interceptor will have a range of 70 kilometers (44 miles) and will be guided to the target by radar control feeding course corrections via a datalink; the interceptor will have its own radar seeker for terminal engagement, destroying the target with a blast-fragmentation warhead. Engagement is expected to begin 5 seconds after target launch, with destruction of the target no more than 40 seconds after that. A single Iron Dome battery could provide coverage for a town the size of Haifa, but it is expected that multiple batteries will be set up in each defense sector to ensure a higher kill probability. Initial operational capability was attained in the spring of 2011, with Iron Dome then quickly intercepting a Palestinian rocket.
Critics claim that the interceptors will be far more expensive than the threats they are intended to neutralize, but in the first place, the consideration is less the cost of the threat than the cost of the damage it can do. In the second place, the Israeli government feels that the program would be worth its cost just in terms of getting out of the ugly circle of reprisals and escalations every time a rocket from Gaza lands in an Israeli neighborhood. It would make things much simpler politically if the rockets were simply blown out of the sky every time they were launched.
* While calling Iron Dome an "ABM system" is a major stretch, second-phase work is also being performed by Rafael and Raytheon on a longer-range defense system named "David's Sling", with a reach of several hundred kilometers for defense against large unguided rockets or small tactical ballistic missiles.
In the TBM defense role, it could be used as a backup for the Arrow; current policy is to fire two Arrows at one target, but it would be much cheaper just to fire one and use the quick-reaction David's Sling in case of a miss. The "Stunner" interceptor being designed for David's Sling will be launched by a solid-rocket rocket booster, performing a hit-to-kill attack using a dual-mode radar / infrared seeker in a drooped "dolphin nose" that allows the radar seeker to stare over the top of the infrared seeker.
A David's Sling system will have four launch units with 16 missiles each, backed up by a multimode radar and fire control system. Although the Stunner will receive guidance from ground radar, it will use its own radar seeker to close in on the target and then use the infrared seeker for terminal attack. The system will have sophisticated "engagement logic" to prevent the debris from falling on a friendly area. Schedule for deployment is unclear. The US military is interested in the program.
BACK_TO_TOP* A group of European countries has been working on an air defense system based on the "Aster" surface to air missile (SAM), built by EuroSAM, a collaboration of the Anglo-French Matra BAe Dynamics Aerospace (MBDA) company, the French Thales (previously Thomson-CSF) company, and the Italian Finmeccanica / Alenia company. The Aster will be used as both a naval and a mobile ground-based SAM, and is being obtained by the armed forces of France, Italy, and Britain.
The initial Aster variants are the "Aster 15" and the "Aster 30". They are two-stage weapons, which differ only in the size of the solid-fuel booster. The short-range Aster 15 has a launch weight of 310 kilograms (684 pounds), a length of 4.2 meters (13 feet 9 inches), and has a range of 30 kilometers (18.6 miles); while the long-range Aster 30 has a launch weight of 450 kilograms (992 pounds), a length of 4.9 meters (16 feet 1 inch), and range of 120 kilometers (75 miles).
The Aster uses an inertial guidance system during most of its flight, with course corrections provided by the sea- or ground-based radar control system over a datalink, but uses an a fully active guidance system for terminal attack. It has a directed fragmentation warhead with a proximity fuze system; the warhead can break up into small fragments for soft targets or large fragments for hard targets. Although the missile is winged, it does use thrusters for high-speed terminal maneuvering, and can perform HTK intercepts.
There are two naval systems, the "Surface to Air Anti-Missile (SAAM)" system that uses the Aster 15 for defense against sea-skimming antiship missiles; and the "Principal Anti-Air Missile System (PAAMS)", which uses the Aster 15 and Aster 30 for defense against the wider range of airborne threats. The missiles are fired from vertical-launch silos on board the launch vessels, and are directed by a control system featuring a multimode phased array radar. French vessels will use the Arabel radar, while Italian vessels will use the Empar radar, and British vessels will use the Sampson radar.
The ground-based system is known as "SAMP/T", for "Sol-Air Moyenne Portee" or "Surface-to-Air Medium Mobile". It uses the Aster 30. SAMP/T features a mobile launcher with eight vertically-launched missiles and a fire control system based on the Arabel multimode phased array radar. The system is designed to be airlifted in standard military transports.
The initial Block 1 Aster 30 also has a limited TMD capability, but a "Block 2" system is now in discussion that will be much more capable, with an enlarged and improved upper stage and seeker system, giving an expanded engagement envelope. Work is underway for a satellite missile warning and tracking system to cue the missile, as well as for an advanced radar to provide missile guidance. The Block 2 Aster is expected to go into service in 2012. The European EADS organization has also been publicizing a concept for a high-altitude interceptor missile named "Exoguard", though details remain unclear.
European governments are very careful to refer only to development of a TMD capability to protect deployed forces, since talk of an NMD defense system is politically controversial. The emphasis is on developing an air-defense system that can take on TBMs as part of its brief, this being a cheaper approach than trying to develop a dedicated TMD system, and much easier to sell to the public.
* In the light of regional nuclear tensions, in 1999 India began work on a missile defense system. The initial concept was to obtain the Arrow 2, but that option fell through due to American resistance, with India then seeking a home-grown solution. However, India did continue to work with Israel on parts of the ABM system, in particular guidance radars.
The Indian ABM system is to include an upper-tier interceptor, designated the "Prithvi Air Defense (PAD)" missile, with a maximum intercept altitude of 80 kilometers (50 miles); and a lower-tier interceptor, designated the "Advanced Air Defense (AAD)" missile, with a maximum intercept altitude of 30 kilometers (19 miles).
The PAD is a two-stage missile, with the first stage powered by storable liquid propellants and the second stage powered by solid fuel. The second stage has maneuvering thrusters to keep it on intercept track and carries a proximity-fuzed warhead. PAD is guided to the target by a ground-based "Long Range Tracking Radar (LRTR)" and an inertial guidance system, with an active radar seeker for terminal attack. Three tests have been performed so far, one each in 2006, 2009, and 2011, with a successful intercept in all cases.
The AAD is a smaller missile, with a single solid-fuel stage. Its guidance scheme is similar to that of the PAD -- radar-tracked guidance and terminal attack with an active seeker -- but it is a "hit-to-kill" interceptor. One test was performed in late 2007 and was a success; one test was performed in 2010 and was a failure, but a test in 2011 was a success. The Indian ABM system is scheduled to be deployed operationally in 2012, with improved interceptors planned for development from that time.
BACK_TO_TOP* The US Navy has been working on their own TMD system. The original effort included both a lower tier "Navy Area Wide (NAW)" interceptor and an upper tier "Navy Theater Wide (NTW)" interceptor, both based on the Navy's existing "Standard SM-2" SAM. NAW was to be based on a "Block 4A" variant of the SM-2. This was to add a fast-burn "Mark 74" booster stage to the missile; an infrared seeker mounted on the side of the nose; a modified proximity fuzing system; and a modified warhead to produce bigger fragments for improved kill probability.
Although some initial tests went well, NAW simply proved too costly, and the Navy abandoned it in December 2001. In early 2003, the Navy awarded a contract to Raytheon to develop a simplified version of the NAW under the "Extended Range Active Missile (ERAM)" program, but this weapon was only intended for long-range defense against aircraft, not for lower-tier missile defense. Raytheon was awarded the contract without a competition, since the Navy was in a hurry to field ERAM and Raytheon had most of the pieces already in place.
ERAM uses the SM-2 Block 4A airframe and warhead, coupled to an active radar seeker derived from that used on the AIM-120 AMRAAM air-to-air missile. Older Standard missiles use "semi-active" radar homing, which requires that the target be illuminated by shipboard radar. ERAM's active radar seeker is autonomous, allowing attacks on targets over the horizon. The Navy may try to see if ERAM can still perform attacks on ballistic missiles. Initial deliveries to the US Navy were in 2011; Australia is also obtaining ERAM.
* NTW is similarly based on an SM-2 with a fast-burn booster stage, but adds an HTK vehicle, known as the "Lightweight Endo-Atmospheric Projectile (LEAP)". The result is designated "SM-3".
Tests of the SM-3 began in 2001 and achieved reasonable progress. A decision was made in early 2003 to field the SM-3. A subset of Aegis cruisers and destroyers were upgraded to the "initial defensive operations (IDO)" configuration to handle the SM-3; it is unclear if all of them will be upgraded, and if so when.
The upgrade involves fit of an improved Aegis radar, the "SPY-1E". The SPY-1E has greater power, range, and target discrimination than its predecessor. Current thinking is that the SPY-1E will be followed by an "Air & Missile Defense Radar (AMDR)" that will combine an X-band radar for search and an S-band radar for engagement, though currently the pricetag on AMDR seems prohibitive. In any case, NTW's planned operation from cruisers and destroyers does give it an advantage, since such vessels can be sent to remote trouble spots as part of a normal naval deployment, lowering the profile of the introduction of missile defense weapons in such regions during a crisis. Work is underway on development of a "Block 2" NTW system. The Block 1 LEAP has an infrared seeker that operates at a single IR wavelength, while the Block 2 seeker operates on two wavelengths and has active radar sensing as well.
On 20 February 2008, an SM-3 fired from the Aegis cruiser LAKE ERIE from off of the Hawaiian actually intercepted a satellite. The satellite was a classified spacecraft, designated "NROL-21", that had failed in orbit after being launched in December 2006. It was falling to Earth anyway, with the stated rationale for the interception merely to ensure that it was broken up thoroughly so it wouldn't present a hazard when it came down. However, the Chinese had performed a test of an antisatellite system not long before and it seems plausible the Americans wanted to drop a hint that they had the capability to respond in kind. If so, the hint appears to have been effective, since the Chinese protested loudly.
* Japan is cooperating with the US on the NTW program, formally initiating a program in late 2003 to obtain a missile-defense system, based the Patriot PAC-3. 124 PAC-3s have been obtained, with 32 provided by the US and the rest license-built by Mitsubishi Heavy Industries. The Japanese are deploying a new, indigenously-designed radar system, the FPS-XX, at four sites to prove missile tracking capabilities, working jointly with US X-band radars. The Japanese Maritime Self-Defense Force (JMSDF) is also acquiring the SM-3 for JMSDF Aegis-class vessels, with their radars upgraded accordingly. The first test launch of an SM-3 from a JMSDF vessel was in late 2007, with the SM-3 kill vehicle hitting a target vehicle simulating a North Korean ballistic missile. The political message behind the test was blatantly obvious.
South Korea has considered a ballistic missile defense, and the possibility that a TMD system could be based in Taiwan has brought protests from the government of mainland China. The mainland Chinese have been upset about American missile-defense efforts, even though China was not a signatory to the ABMT. The country relies heavily on ballistic missiles as a military capability, and an effective missile defense against their relatively small and crude arsenal of long-range strategic weapons could leave them vulnerable to attack.
* The current SM-3 is the "Block IB", updating the previous Block IA with a kill vehicle featuring an improved two-color seeker, avionics, and maneuvering thruster system. It will be followed by a "Block II" that would increase range by expanding the diameter of the second stage from 35 to 53 centimeters, matching the width of the fast-burn booster. The Block II will be followed in turn by the "Block IIA" that adds a larger kill vehicle with a smarter seeker and more powerful divert thrusters, and ultimately the advanced "Block IIB", still in definition, with more reach for boost-phase intercept.
The service has also considered next-generation technology for TMD. One concept is for a "Mass Moment Missile (3M)", which would achieve directional control by shifting a mass around inside its airframe, instead of thrust vector controls. The result would be a lighter and faster missile. Improved seeker technology is another item being investigated. One option is a simplified, cheaper passive infrared seeker that would have a 220 degree field of view, using a panoramic mirror to reflect infrared energy onto a fixed detector. An alternative option is an advanced active seeker, probably using millimeter-wave radar technology.
Given the success of the SM-3, there is considerable interest in developing a land-based variant of the SM-3, coupled to the X-band radar system developed for THAAD. As discussed below, the Obama Administration seems to be very intrigued with this option.
* There was considerable work in parallel with development of US TMD weapons on what were known as "boost phase intercept (BPI)" systems that would hit an adversary missile when it was accelerating just after launch. At that time, the target would be moving slowly, wouldn't have deployed decoys, and would fall back on into the launch area when shot down -- the last being a big plus if the missile had a biological or chemical warhead. Several BPI systems were investigated:
Incidentally, there was interest in parallel with work on the ABL in developing a chemical laser satellite for NMD, but no such program has come close to producing flight hardware. Although use of lasers for TMD and NMD seems to be in a holding pattern for the time being, the US military remains very interested in the development of high powered lasers for missions such as shooting down battlefield rockets and artillery shells. Considerable progress has been made on solid-state laser systems for such tasks, though none are remotely close to fielding. However, this is a topic that needs to be discussed elsewhere.
The US still remains interested in BPI, the current focus being on a derivative of the AMRAAM designated the "Network-Centric Airborne Defense Element (NCADE)". NCADE looks very much like a standard AMRAAM from the outside, but it is actually a two-stage weapon -- split behind the midwings and with a powered HTK second stage that is fitted with an infrared seeker derived from the AIM-9X Sidewinder, instead of the radar seeker of the standard AMRAAM. The seeker is protected by a nose fairing until the missile performs its terminal attack. NCADE's capabilities are secret, but apparently it can in principle intercept low-orbiting satellites.
Maintaining the AMRAAM form factor allows NCADE to be carried by any aircraft that can carry AMRAAM; targeting can be performed by advanced "active array" radars now becoming common on first-line combat aircraft like the F-15 Eagle, featuring greater range and capability than the previous generation of aircraft radars. High-speed datalinks fitted to the launch aircraft would permit integration into a wider defensive network. The notion of carrying weapons such as NCADE on UAVs has been revived by the MDA, partly because larger UAVs are now available, partly because avionics systems have been improved; the Israelis seem to be thinking along similar lines, envisioning a UAV carrying a variant or derivative of the Stunner missile.
The MDA has also been experimenting since 2009 with a set of MQ-9 Reaper UAVs fitted with an "Airborne Infrared (ABIR)" system to track missile launched for targeting by anti-missile defense systems. There's no commitment to deployment, but the MDA is considering the matter; whether the Reapers could also carry NCADE is an interesting question.
BACK_TO_TOP* As mentioned, work on TMD systems revived interest in a US NMD network. Conservative think-tanks envisioned a range of missile defense scenarios, such as ships carrying loads of ABM interceptors steaming off the coasts of America, able to launch missiles cued by orbiting satellite missile warning and tracking networks, and new ground-based radars.
Military officials working on TMD were nervous about the push for NMD, since it muddied the waters for TMD efforts. However, the potential threat of ICBMs in the hands of smaller powers gave NMD advocates in the US Congress and the military a lever to push for fielding a pilot NMD system. BMDO initiated a NMD investigation program, with Boeing as the prime system contractor. The core of the NMD system was to be a Raytheon HTK interceptor, designated the "Exoatmospheric Kill Vehicle (EKV)", designed to attack missiles at altitudes of hundreds of kilometers. Space-based intercept is trickier in some ways than atmospheric intercept, since balloon decoys and chaff remain effective until the RV enters the atmosphere.
The EKV includes an infrared imaging array, and a hydrazine thruster space maneuvering system. The EKV is launched from the ground by a multistage booster to hit targets in space. Research is underway to develop improved infrared arrays and a complementary laser radar that may be used in an improved NMD EKV or other missile defense systems.
The NMD system also involves an early-warning satellite network. The current "Defense Support Program (DSP)" early-warning satellite network will be used at first, but the NMD system is expected to eventually make use of the next-generation "Space Based Infrared System (SBIRS)" satellite constellation. The satellites will cue a ground-based radar system, based on a new X-band radar, plus upgrades of existing long-range radar assets. The existing Ballistic Missile Early Warning System (BMEWS), with sites in Alaska, the UK, and Greenland, and Pave Paws national early warning radars are being improved to the "Upgraded Early Warning Radar (UEWR)" standard. All the elements will be integrated through a "Battlefield Management Command, Control, & Communications (BMC^3)" system.
* NMD tests began in 1999, initially with the EKV launched by surplus Minuteman II ICBMs from Kwajalein Atoll in the central Pacific, against surplus Minutemen used as targets. Tests over the next decade had mixed results, but by 2008 the system was judged effective -- at least against a small number of targets that lacked countermeasures.
The Minuteman booster used to launch the EKV in the initial tests was just a stopgap. Development of the production "Ground Based Interceptor (GBI)" originally followed two tracks, one at Boeing that was later handed off to Lockheed Martin, the other at Orbital Sciences (OSC). The Lockheed Martin GBI never flew and was ultimately canceled. The OSC GBI performed its first flight in February 2003, with following tests again having mixed results but working towards maturity.
The Orbital GBI is a three-stage solid-fuel missile, derived from the Orbital Pegasus, Taurus, and Minotaur boosters. It is a relatively big weapon, 16.8 meters (55 feet) long, 1.27 meters (4 feet 2 inches) in diameter, with a launch weight of 12.7 tonnes (14 tons). It has an astounding ceiling of 2,000 kilometers (1,250 miles). The GBI of course carries the Raytheon EKV as its payload. Incidentally, OSC has also developed targets for GBI tests, with the targets based on off-the-shelf solid rocket boosters.
Since one of the objections to NMD is the difficulty of intercepting multiple warheads or warheads protected by decoys, further development work has been conducted on a "miniature kill vehicle (MKV)", about the size of a coffee can, with a weight on the order of 5 kilograms (11 pounds), and fitted with an infrared imaging array. A single interceptor missile would carry a cluster of dozens of MKVs, programming them to attack individual targets before dispersal and then providing them with command updates after dispersal. Lockheed Martin was awarded an initial MKV development contract in early 2004, with Raytheon then brought into the exercise later. However, this effort was canceled without flying a prototype.
* Early NMD tests brought the missile defense issue back into the headlines and onto the first rank of issues for the Clinton Administration and proved a political quagmire. Both hawks and doves were critical of the proposed NMD plans, though for different reasons, and there was no broad-based consensus for deployment. The Chinese were uniformly critical of TMD as well as NMD; the Russians shuffled between fear and derision, while the Europeans seemed lukewarm on the subject.
The "lame duck" Clinton Administration logically passed the issue on to the incoming Bush II Administration, and the whole quarrelsome matter went quiet until the spring of 2001, when President Bush began to push for deployment of an NMD system. A few months later, in early December 2001, Bush announced that the US would pull out of the ABM Treaty in six months. He stated that the ABMT was a "relic" that blocked timely missile defense testing and deployment, which was judged "indispensable" as a defense against terrorists and rogue states. At the beginning of 2002, BMDO was renamed the "Missile Defense Agency (MDA)" to further emphasize the stature of NMD in the eyes of the Bush Administration, and at the end of 2002, the administration gave the go-ahead for operational development and deployment.
Under the "Ground-Based Midcourse Defense (GMD)" system, missiles have been sited, with 30 in place at Fort Greeley, Alaska, and 30 more at Vandenberg Air Force Base in California. The Fort Greeley missiles are supported by the "Sea Based Radar (SBR)", an X-band radar on a floating platform, while the Vandenberg missiles are supported by a ground-based X-band radar at Beale AFB in California. This would give a defense shield against "northeast Asia" (read as "North Korea"). However, the program has run into difficulties, with the last successful intercept by a GBI taking place in 2008, and later tests failing, mostly due to problems with the EKV. Tests were suspended while the bugs were tracked down; two intercept tests were performed in 2010, with both proving failures, and so tests were suspended again.
* In the meantime, the Bush II Administration worked to set up a defense against Middle Eastern nations -- read as "Iran" -- with updates of the BMEWS radar sites at Fylingdales in the UK and Thule, Greenland. A battery of interceptor missiles was to be set up in Poland while the X-band radar at Kwajalein was to be relocated to the Czech Republic. The Russians made very angry noises at the idea of setting up a missile defense system in Eastern Europe, though it appears the protests were at least partly for domestic consumption.
Although the Obama Administration continued bringing up the Pacific-based NMD system, work on deploying the GBI system in Eastern Europe was canceled in the summer of 2009. The stated rationale was that intelligence assessments indicated Iran was no longer focusing on very long range missiles, and so a theater defense system was more appropriate. The solution is now expected to be the SM-3 Block IIB, with deployment in 2020 at earliest. As an interim solution, the Obama Administration maintained two Aegis-class vessels armed with the SM-3 on patrol in the Persian Gulf at all times.
BACK_TO_TOP* The debate over missile defense is very convoluted and eye-glazing, with the rhetoric clearly outstripping the facts. I had such trouble sorting my way through all the pros and cons that I finally came to the solution of covering the controversies in the overview section of this document, allowing me to set them in the background in the rest of the text so I could deal with the technical details with minimal distraction.
* Sources include:
The Federation of American Scientists (FAS) website was surveyed for this document as well.
* Revision history:
v1.0 / 01 jun 00 v1.1 / 01 jul 00 / Review & polish. v1.2 / 09 jul 00 / Update on NMD test failure. v1.3 / 01 jan 01 / New details, broke into two chapters. v1.0.4 / 01 oct 01 / Review & polish. v1.0.5 / 01 may 02 / Review & polish. v1.1.0 / 01 mar 04 / General update, broke into three chapters. v1.1.1 / 01 mar 06 / Review & polish. v1.1.2 / 01 mar 08 / Review & polish. v2.0.0 / 01 feb 10 / Dropped lasers, cut down to two chapters. v2.0.1 / 01 jan 12 / Review & polish.BACK_TO_TOP