557 January 13, 1987 TECHNOLOGY SPEEDS THE STRATEGIC DEFENSE INITIATIVE TIMETABLE INTRODUCTION As originally conceived, the Strategic Defense Initiative (SDI was a "research program1# to identify promising technologies for a strategic defense system this has paid off handsomely. Technologies have been identified as very promishg for use in near-term strategic defense deployment next step is to turn these promising technologies into reality by moving toward development and testing so that actual deployment ca'n begin Almost four years into the SDI program, The Among the gains so far Great progress has been made in technology for intercepting ballistic missiles outsi d e (exoatmosphere) as well as inside the atmosphere (endoatmosphere Technologies exist that could be upgraded and applied to a terminal defense against both short-range and long-range ballistic missile warheads Laser research has progressed to the point wh e re scientists are talking about laser radar and discrimination capabilities being available in the early 1990s An anti-missile laser prototype weapon could be available by the late 1990s And research on infrared sensors has made headway in detecting and t racking balli.stic missiles inside the atmosphere and in space.

The momentum of SDI research is greater than originally anticipated. What once seemed probable now seems certain. What once was possible now is probable. And what once was thought impossible i s now within reach. Clearly, advances in strategic defense technologies justify a strong vote of confidence for SDI.

PROMISING NEAR-TERM STRATEGIC DEFENSE TECHNOLOGIES One of the most enduring fallacies about SDI is that no system can be deployed for many years. Yet technologies already exist that could be used in a strategic defense system deployed either immediately or in the near future derived from existing air defense and ballistic missile defense systems: others are emerging from SDI research on adv a nced anti-ballistic missiles, radars, sensors, and interceptor systems Some of these technologies can be The Exoatmospheric Interceptor Subsystem The best candidate so far for a strategic defense system against missile warheads in the midcourse of their f light is the Exoatmospheric Reentry Vehicle Interceptor Subsystem, or ERIS, which is being developed by the U.S. Army. ERIS is an outgrowth of the Army's Homing Overlay Experiment (HOE) conducted at Kwajalein Atoll in the Pacific Ocean in June 19

84. During this experiment a missile interceptor successfully destroyed a Minuteman ICBM warhead traveling 20,000 feet per second that had been launched some 4,000 miles away at Vandenberg Air Force Base in California. HOE'S passive infrared sensor tracki n g system worked better than expected at acquiring, tracking and differentiating targets from decoys. The Homing Overlay Experiment success was so encouraging that the U.S. Army's Strategic Defense Command decided to develop the HOE system, now called ERIS over a five-year period.

The ERIS system will consist of a solid-fuel, ground-launched interceptor placed on a wheeled vehicle for mobility. The two-staged ERIS missile will be low-cost, lightweight, and capable of hitting incoming warheads at altitudes u p to 1,100 miles and up to 2,500 miles down range from the launch site A single ERIS ABM site deployed in the north central part of the United States with the appropriate radars and sensors (say, at the old U.S. ABM site at Grand Forks North Dakota) could . provide partial ballistic missile defense coverage for the entire North American continent. In Europe, the ERIS system 1. Specific ground targets such as missile silos or cities can be picked out for preferential defense by an ERIS system. A ground-based E RIS system deployed at Grand Forks therefore could protect not only MX missile fields in Wyoming but specific urban centers in the Midwest as well. A more comprehensive system would require a multilayered defense and greater discrimination techniques than are now technically feasible 2could help defend all of NATO territory against Soviet 88-20 intermediate-range nuclear missiles.

ERIS testing will begin sometime between 1988 and 1990, with full deployment possible as early as 19

93. The total life cycle cost of one ERIS site consisting of the 100 ABM interceptors permitted by the 1972 ABM Treaty would be $3.5 billion in 1986 fiscal year dollars over a ten-year period-or only 350 million annually. This price includes the cost of interceptor missiles, upgr aded tracking radars, and battle management systems. The price would increase if laser radars on a space surveillance and tracking system were used to discriminate between warheads and decoys in space.

Adding terminal defenses around U.S. and NATO missile silos military bases, and cities to supplement the midcourse ERIS defense would provide a more effective defense against an increased number of Soviet missiles satellites in space, such as is envisioned in the Pentagon's proposed Boost Surveillance and Tr a cking System (BSTS), for tracking Soviet missiles in their boost phase would give the ERIS system early warning of a missile's projected trajectory surveillance and tracking system to discriminate between decoys and reentry vehicles in space after the ICB M has launched its payload would be required for a fully effective defense against an all-out Soviet nuclear attack. Also needed to defend against this maximum threat are space-based rockets or kinetic-kill vehicles SBKKV capable of destroying targets in t h e boost, post-boost, and midcourse phases of the missile's trajectory Deploying a number of advanced high altitude Developing a.space-based Some analysts have argued that it makes no sense to deploy ERIS until the problem of discriminating between decoys and real warheads in space has been resolved. Such a delay, however is not warranted.

For one thing, limited discrimination techniques could be developed in the near term to deal with the limited threat of an accidental nuclear launch or a possible errant missile fired by a deranged Soviet submariner. For another thing, a perfect solution to the discrimination problem may take a very long time. Perfection however, is an unrealistic standard to set for any weapons system-or any technological development, fo r that matter progress being made in space surveillance technology already demonstrate that enough real warheads could be identified and tracked in space to warrant deployment of an ERIS system to protect against a limited nuclear attack. As space surveill a nce technology improves The successes of the Homing Overlay Experiment and the general moreover, the capability of an ERIS warheads and decoys will improve as to this seems to be Congress, whose forced the SDI office to scale back tracking program system t o discriminate between well. The only serious impediment SDI budget cuts this year have its space surveillance and 3The Hiah EndoatmosDheric InterceDtor If incoming missiles are not destroyed outside the atmosphere they can be intercepted in the upper par t of the atmosphere.

Pentagon is studying a new concept to do this called the High Endoatmospheric Interceptor, or HEDI an endoatmospheric defense against those nuclear warheads that leak through the boost and midcourse layers of a space-based strategic de fense system. HEDI interceptors would carry explosive or fragmentation warheads designed to destroy reentry vehicles 20 to 40 miles down range from HEDIIs point of launching and at an altitude of around 65 miles The It would be the first layer of There ar e many other promising technologies for intercepting incoming warheads in the upper part of the atmosphere. The U.S. can draw on the High-Acceleration Booster Experiment, or HIBEX, a modified l1Sprinttn hypervelocity interceptor capable of destroying warhe ads by crashing into them. There also are new technologies arising from the Smal12Radar Homing Intercept Technology (SR-HIT) developed by the U.S.

Army. The SR-HIT is a self-guided missile steered by radar which could knock down nmaneuverablell warheads, t hose capable of changing their course in the terminal phase of flight. Some version of SR-HIT could be used not only against strategic missile warheads reentering the atmosphere from outer space but against tactical short-range ballistic missiles, such as the Soviet SS-21 based in Eastern Europe that do not leave the atmosphere.

Flexible Lightweight Agile Guided Experipent, or FLAGE, was tested at white Sands Missile Range in New Mexico. Using radar for guidance the 12-foot-long FLAGE hypervelocity missile destroyed a 44-inch diameter sphere that was hung 12,000 feet in the air by a balloon.

While the April 12 test was against a stationary target, future tests will be conducted against air-launched moving targets.

This experiment showed that an anti-balli stic missile could be accurate enough to destroy a target inside the atmosphere with a conventional explosion has been a longtime aim of ballistic missile defense research. The On April 20, 1986, an updated version of the SR-HIT, called the This capabilit y to hit a bullet with a bullet 2. The "Sprint" was a high-velocity anti-ballistic missile deployed in 1974 as part of the Safeguard" anti-ballistic missile system at Grand Forks, North Dakota. The "Sprint" was nuclear-armed and intended for intercepting i n coming warheads in the upper layers of the atmosphere. The "Safeguard" system was deactivated in 1976 3 Army Tests Guidance Accuracy of Radar Homing Device Aviation Week and SDace Technolonv, May 12, 1986, p. 60 4FLAGE experiment demonstrated that radar g u idance software can be integrated into flight hardware to provide the accuracy required for intercepting short-range ballistic missiles. Future tests against moving targets are required to ensure system.effectiveness in a real battlefield situation a FLAG E system could be used in an anti-tactical ballistic missile system in Europe or Israel and in a U.S.-based strategic defense agaipst low-flying ballistic missiles launched from submarines at sea Matched with space-based and airborne sensors The Low Endoat m ospheric IntercetAor For the lowest end of the terminal defense spectrum, thesU.S. is developing the Low Endoatmospheric Interceptor (LEDI) system. This interceptor missile would be deployed on the ground to defend highly valued but relatively small targe t s such as missile silos and command and control centers which most likely would be protected in "hardened concrete bunkere. By intercepting nuclear warheads at least 4 miles from their targets, LEDI could save a large number of "hardened1' U.S nuclear mis sile silos from a Soviet first strike. It also could be used to protect targets against non-nuclear warheads launched on short-range ballistic missiles.

Guided by radar LEDI will intercept incoming-warheads at an altitude of at least 4 miles above the grou nd. The Flexible Lightweight Agile Guided Experiment, or FLAGE, can be applied to developing LEDI by modifying the range of the interceptor to deal with threats at the lower end of the atmosphere.

Other candidates for a LEDI system include 1) some version of the "Aegis" surface-to-air missile SAM) currently deployed on U.S.

Navy air defense cruisers: 2) a modified French-manufactured 1nAster-301t SAM, a ground-launched two-stage solid propellant missile with a range of around 20 miles for use against aircraft and short-range ballistic missiles: 3) the IIPatriot" air defense s ystem currently deployed in Western Europe by NATO, which travels at a speed of 5,000 miles per hour and can intercept aircraft at a range of nearly 65 miles. The "Patriot" could be converted into an anti-ballistic missile by modifying its radar and assoc i ated computer software, warhead, and rocket engine for use in a terminal defense 5. For a detailed study of anti-tactical ballistic missile defense in Europe, see Michael Ruehle, 1 (London: The Institute for European Defence and Strategic Studies, 1986 6. For a more detailed discussion of LEDI, see Manfred R. Hamm and Kim R. Holmes Anti-Tactical Ballistic Missile Defense, Deterrence, and the Conventional Defense of NATO Washinaton Ouarterlv, Spring 1987 5against either missile warheads coming from space or short-range ballistic missiles that have a low trajectory path No matter which system is developed, LED1 can provide a good last minute defense of highly valued targets against not only nuclear-armed strategic ballistic warheads reentering the atmosphere f rom !space but low-flying, conventionally armed short-range ballistic missiles as well SDace-Based Kinetic-Kill Vehicles Promising too in the near term are space-based kinetic-kill vehicles (SBKKV or very small, Ilsmart,ll terminally guided rockets placed on platforms in space. Deployed on hundreds of space platforms, these rockets would be shot at a missile shortly after it was launched or at a reentry vehicle flying through space. Guided by information supplied by short- and long-wave infrared sensors, t h ese rockets would head for a target, and using homing detectors on the rocket itself, maneuver at the last minute to destroy the target by crashin9 into it directly or by exploding a non-nuclear warhead nearby. For intercepting boosters, shost-wave infrar e d homing devices could be employed to identify and track the hot rocket plume of the booster in the first 200 to 300 seconds of flight, or in the so-called boost phase. In the post-boost and midcourse phases, when the rocket plume has been greatly diminis h ed or cut off entirely long-wave infrarfd sensors capable of picking up cooler targets would have to be used The space-based kinetic-kill vehicle is a very promising strategic defense technology because: 1) Space rockets can use well-established ballistic missile technologies involve such technical and economic factors as making rocket components small Benough and at a low enough cost to put them in space in large numbers. in the boost-phase. So doing, they could destroy a missile before it had fired its i n dependently targeted reentry vehicles. The result is that many enemy warheads are lnkilled,lt in effect, by one U.S. shot The major challenges thus are not scientific but rather 2) Space kinetic-kill vehicles could be employed against missiles 7. Office o f Technology Assessment, Ballistic Missile Defense Technolovies (Washington, D.C Office of Technology Assessment, 1985), p. 155 8. pp. 156-157 9. Information provided by the Strategic Defense Initiative Organization 63) Due to their versatility, SBKKVs cou l d threaten targets in the boost, post-boost, and midcourse phases of a ballistic missile's tra j ectory The technical challenges posed by the space-based kinetic-kill vehicle program include the miniaturization of electronics, valves batteries, coolers, g u idance systems, and other components of conventional rocket systems. This is needed to reduce the weight of the space-based platform and to make the rockets fast and maneuverable enough to engage targets at very high speeds have to be accurate enough and h ave sufficient fuel to change course repeatedly as it maneuvers to strike a target guidance system, meanwhile, will have to be devised to ensure that the space rocket actually hits the missile body in the boost phase and not the hot rocket plume that trig g ers the infrared sensors The rocket also will A tracking and With sufficient funding, officials at the Strategic Defense Initiative Organization are confident that these technical challenges could be met and an operational system deployed by the early 199 0 s. be not only cost-effective but valuable force multipliers in a multilayered strategic defense system Pentagon officials are convinced that SBKKVs will prove to PROMISING LONG-TERM TECHNOLOGIES One of the most promising directed energy technologies for s trategic defense is the free electron laser. This FEL is a powerful light beam produced by first detaching electrons from their orbit around atomic nuclei and then accelerating them almost to the speed of light through a linear array of magnets. 'The tube in which this already occurs is called a "wiggler." It is almost 10 feet long and lined with 120 electromagnets. Actual SDI applications, of course would require a much longer tube. The magnets "wiggle" the electrons until they line up in a synchronous os c illatory motion electrons-decelerate, the kinetic energy of the electrons is transformed into radiation or laser light light is small enough, the free electron laser could be aimed through the atmosphere over tremendous distances to knock down ballistic m issiles or warheads in space or in the very high atmosphere.

First, an FEL weapon could be deployed on the ground, thereby avoiding the costly task of putting the laser power source in space. Secondly As the If the wavelength of the The free electron laser is promising for a number of reasons 10. Information provided by the Strategic Defense Initiative Organization 7the FEL shows the most'technical promise of achieving high power at short wavelengths A FEL has already been produced at the Lawrence Livennor e National Laboratory in California, and scientists there are very much encouraged by the prospects of developing a free electron strategic defense weapon.

Great.progress already has been made in three key areas of free electron laser technology 1) Laser e fficiency or the measure of how efficiently the kinetic energy of electrons is converted into laser light. The more efficient the laser, the more promising it is as a weapon. In 1985 scientists at the Livennore Laboratory produced a free electron laser, w h ich converted 40 percent of the electrons' kinetic energy into coherent radiation or laser light. Components of the FEL now under development at Livennore Laboratory which will lead to a much more powerful free electron laser operating at shorter waveleng t hs by the early 1990s 2) The free electron laser at high levels of power. Thus far a free electron laser has been created only at a low average power level, that is, by generating around one gigawatt (one billion watts of unsustainable power instantaneous ly. But to create a weapon it is necessary to boost the laser beam with very high levels of average sustainable power electron beam injectors and new magnetic pulse power units which will be applied to a new FEL test facility currently under construction.

These new technologies hold enormous promise for increasing the input of power required for an operational free electron laser weapon The Livermore Laboratory is working on new 3) Reducing the wavelength of the free electron laser. To propel a laser throu g h the atmosphere, it is necessary to reduce its wavelength so that it can travel through the relatively densely packed malecules of the earth's atmosphere. An experiment currently underway at Livermore Laboratory ailms at lowering the' free electron laser ' s wavelength to 10 microns. The goal is one micron or below at high levels of average power. Livermore scientists are confident that with sufficient funding a free electron laser will reach these short wavelengths at higher levels of sustained power by ar o und 1993 The Boost Surveillance and Trackina Svstem The most effective way to destrov ballistic missiles is to eliminate them in the firs5 50 to 200-seconds or so of their flight-in their boost phase. It is far more effective to kill a missile carrying it s many warheads than to wait until they have separated from the missile in space. Critical to boost-phase 11. A micron is a unit of length equal to one millionth of a meter (39.37 inches or one thousandth of a millimeter 8interception is the ability to ide n tify and track missiles from the moment they are launched. It is also necessary to collect data on missiles and to hand it over to space-based surveillance and tracking systems (SSTS which can help guide laser or kinetic-kill vehicles to destroy warheads f rom missiles that have escaped the boost-phase defense Addressing this is the Boost Surveillance and Tracking System BSTS) experiment. The Strategic Defense Initiative Organization is looking at ways to detect a ballistic missile's gaseous plume with spac e-based infrared sensors as soon as the missile is launched.

Getting a reading on the missile's plume can be used not only to guide a laser or space-based kinetic-kill device to the missile, but to establish its trajectory and projected point of impact if it.and its warheads should escape boost-phase interception.

The specific purpose of the BSTS experiment is to determine whether a satellite using infrared sensors can collect adequate data on a missile against the earth's background prototype now in the w orks will not be used for anti-ballistic missile defense purposes, it will tell scientists a great deal about what they can expect from more advanced versions of BSTS technology currently planned, BSTS will have two important spinoffs: 1) it wili provide a more survivable and accurate early warning system against ballistic missile attack; and 2) it will allow the U.S. to monitor Soviet tests of multiple independently targetable reentry vehicles MIRVs) with greater accuracy and reliability. This would impro v e the ability of the U.S. to verify Soviet compliance with anus control agreements Although the BSTS As CONCLUSION There are many new technologies and concepts arising from SDI A terminal research midcourse defense system could begin in the early 1990s de f ense against ballistic missiles in the upper and lower parts of the atmosphere could be built on existing technologies. Much progress has been made on producing a free electron laser, which could be'deployed on the ground for intercepting missiles in all phases of their trajectory missiles in the boost-phase hold8 promise not only for boost-phase interception but for improving the U.S. early warning system.as well.

Some of these concepts could make deployment of a strategic defense system a reality within a half dozen!years. Other more advanced systems show great promise in the mid- to late 1990s. No matter what the timetable for deployment, more than enough promising SDI technologies exist to confirm that strategic defense is Tests show that deployment of an effective nationwide ERIS And the sensor technology for identifying and tracking 9technically feasible. Deployment options ,are already emerging, and more are sure to follow as SDI technologies'mature.

Kim R. Holmes, Ph.D.

Deputy Director of Defense Policy Studies 10