the beam at the target is about equal to the size of the transmitter mirror, the intensity of the beam at the mirror would have to be from 100 to 300 times what it is required to be at the target. From this requirement another arises: if the laser light is to destroy the target without damaging the mirror, the mirror must be from 200 to 300 times more reflective than the target. If the opponent protected his missiles or aircraft with a reflective coating, however, the target would be almost as shiny as the mirror.

One could attempt to overcome this difficulty by building a large mirror that could focus the laser beam on a target a few kilometers away. The cross section of the beam at the target would then be smaller than the cross section at the mirror. This solution is impractical, however, because a mirror much larger than a meter in diameter is awkward to operate and point and is vulnerable to simple projectiles. Moreover, very large focusing mirrors would be ineffective because atmospheric turbulence would disturb and defocus a wide beam. An effort to build more reflective mirrors and to cool them could be countered by painting the target missiles with several coats of an ablative material that would burn off and carry away most of the incident energy from the laser beam. In a contest between improved lasers and counter-measures the laser is at an intrinsic disadvantage, since even in good weather the atmosphere works against it.

Another tactic for a laser weapon engaged in defense against missiles wold be to wait until the target was only about a kilometer away before attacking it with a laser. The intensity of the beam would then be degraded by a factor of about 10 instead of 300, and a reasonably reflective mirror could perhaps withstand the energy flux required to destroy the target. The weakness of this plan is a lack of time. A missile approaching at, say, twice the speed of sound covers the last kilometer of its fight in about 1.5 seconds. A laser weapon would not have enough time to engage more than one attacking missile. In the same length of time a rapidly firing cannon could direct several explosive shells at the target.

Even though laser light travels almost a million times faster than an ordinary projectile, a laser weapon would have no intrinsic operational advantage over a fastfiring cannon for close-range protection from missiles. On the contrary, the laser has several disadvantages. An attacking missile can be protected from laser light (particularly a continuous-wave beam of low intensity) by a thin film of a substance that is constantly excreted at the nose of the missile to absorb the energy of the beam and carry off the heat. Another defense would be to make the missile rotate so that it spread out the heat over the entire surface area. Furthermore, even over a range of one kilometer bad weather can completely neutralize a laser weapon.

A final consideration is that the process of detecting and tracking a target is more demanding with a laser weapon than it is with other defensive weapons, since the beam must actually hit the target if it is to have an effect. The standard of accuracy for the tracking system of a cannon that fires projectiles is much less stringent, particularly if the projectiles carry an infrared seeker that enables them to home in on the target.

On balance, then, laser weapons operating in the atmosphere offer no clear advantage over existing weapons for close-range defense. In addition they can be impeded by weather, they cannot operate effectively beyond a range of a few kilometers, they are easier to neutralize by countermeasures than ordinary projectiles or supersonic missiles and they require a much better tracking system. Under these circumstances it is difficult to see how the development and deployment of such fragile, complex and expensive weapons would improve the military capability of a nation.

It does not necessarily follow that research on high-energy lasers has no worthwhile objectives. Although lasers are decidedly unpromising as weapon systems, they may have valuable applications in industry, particularly in chemical engineering and in energy systems based on nuclear fusion. For these reasons rather than for unrealizable military applications the U.S. would do well to continue research on the many aspects of the technology of high-energy lasers.

APPENDIX 21

WASHINGTON POST ARTICLE of March 27, 1983, ENTITLED “No, MR. REAGAN, IT WON'T WORK"

(By Jan M. Lodal)

In his speech last Wednesday night, President Reagan urged American scientists "to turn their great talents to the cause of mankind and world peace: to give us the means of rendering . . . nuclear weapons impotent and obsolete."

The world would surely rejoice if such a feat were possible. Unfortunately, it is not. Following the president's proposed course would only create false hopes and, in all likelihood, intensify nuclear dangers rather than diminish them.

There are, to begin with, serious doubts about the technical feasibility of developing a defense against ballistic missiles that the Soviets could not easily counterdoubts that were aired widely in the late '60s and early '70s.

Our nation has overcome many technical challenges in the past, of course, and we certainly should not shrink from another if it would end or seriously reduce the threat of nuclear war. But the president's approach has problems that go far beyond technology. Consider just five:

DEFENDING AGAINST BOMBERS AND CRUISE MISSILES

Ballistic missiles are only part of the nuclear threat we face. For example, lowflying bombers and terrain-hugging cruise missiles could pass unaffected through a defense such as the president proposes.

In fact, as likely as it may seem, defending against nuclear-armed bombers and cruise missiles is an ever greater technical challenge than defending against ballistic missiles. And if the defense against the the bombers and cruise missiles were not perfect, the weapons that "leak through" could destroy the ground-based components of the ABM system itself. Unless a defense can keep out all types of weapons, it is useless in a nuclear war.

OUR ALLIES

President Reagan said that our defense should destroy Soviet missiles before they reach "our own soil or that of our allies." But the Soviets have many ways to launch nuclear weapons against our allies in Europe that would be unaffected by an ABM defense. They could use aircraft, nuclear artillery or even armored vehicles carrying "atomic demolition munitions" with an invading force. It is inconceivable that an effective nuclear defense could be developed for Europe.

TREATY COMMITMENTS

The president says he will carry out his program "consistent with our obligations under the ABM treaty." But that treaty explicitly prohibits not only the deployment but even the development of any system based in space-the most likely candidate for the technological breakthrough the president seeks.

DESTABILIZING THE NUCLEAR BALANCE

One can envision a world in which the nuclear powers have limited offensive capabilities and effective defenses. A small residual offensive nuclear force would still deter some wars, while the defense would eliminate threats from third countries and concerns about accidental attacks, and perhaps even the threat of massive destruction should war occur. But how do we get from where we are to this Nirvana? Without a complete political reconciliation with the Soviet Union (which Reagan certainly does not anticipate), the initiation of large-scale ABM deployments by either side would be seen as an attempt by the other to enhance its capability to fight a nuclear war successfully.

The Soviets would understand this and undoubtedly respond with countermeasures to any ABM we deployed. The result would be a new escalation of the arms race greatly exacerbated international tensions, and increased risk of nuclear war.

COST

A full-scale ABM program, carried out in combination with the other necessary elements of such a posture (defense against bombers and cruise missiles, civil defense, defense of our allies, and a buildup of conventional weapons to offset the re

38-353 0-84--20

duction in nuclear deterrence) could easily double our current $250 billion-a-year defense budget.

The national could afford this if it had to-defense would still be only about 12 percent of our Gross National Product. But it would call for an overwhelming national effort, requiring all elements of our society to be involved in active preparation for the possibility of war. If is inconceivable that the American public would support such an approach.

The president obviously is sincere in his concern about the risk of nuclear war and in his desire to marshall our scientific strength to reduce or eliminate this risk. But unfortunately, some problems simply are not susceptible to easy technological solution.

There is no way we can turn the technological clock back on the overwhelming power of nuclear weapons. Our best hope is to negotiate effective arms control agreements that contain the risk and ultimately eliminate it. As we pursue negotiations, we must maintain strong and effective military programs that will deter Soviet aggression. But it is folly to pin our hopes on the chimera of a perfect or safe defense.

APPENDIX 22

AVIATION WEEK AND SPACE TECHNOLOGY ARTICLE OF OCTOBER 31, 1983, ENTITLED "SHUTTLE MAY AID IN SPACE WEAPONS TEST"

(By Clarence A. Robinson, Jr.)

WASHINGTON.-Defense Dept. and the Air Force are considering an industry proposal to use the space shuttle and begin within two years technology demonstrations in orbit for space-based weaponry to defend U.S. satellites. The technology later could be applied to ballistic missile boost-phase intercepts using directed-energy weapons for defense.

Teledyne Brown Engineering's proposal, known as Validator, could result in the final phase of flight test in space of a demonstration of a high/energy laser or kinetic energy hit-to-kill weapon against spacecraft targets.

A three-phased demonstration program, the Validator concept is based on utilizing existing technologies and off-the-shelf hardware, some of which has already been flight tested on boosters in the Army's ballistic missile defense program.

The Teledyne Brown proposal generally follows recommendations made to the President by a Senior Interagency Group (AW&ST Oct. 17, p. 16), and Defensive Technologies Study Team (AW&ST Oct. 24, p. 50) in reports on an advanced ballistic missile defensive system for the U.S. Both groups called for early feasibility demonstrations of the technologies involved.

Defense Secretary Caspar W. Weinberger also recommended to Reagan a $26-billion program for defensive technology development from Fiscal 1985 through Fiscal 1989. It includes options for early demonstrations.

Close friends and advisers of the President have stressed to Reagan the importance of early technology demonstrations to establish the credibility of U.S. technological prowess for an advanced ballistic missile defense capability. This would dispel the aura of Star Wars associated with the President's plan to move the nation away from the offense-dominated mutual assured destruction strategy of the superpowers to an assured survival defensive capability for the nation.

Briefings of the Validator concept were presented to the Defensive Technologies Study Team, the Defense Dept.'s Advanced Research Projects Agency and to USAF's Space Div.

In the initial phase of Validator, a long wavelength infrared sensor would be tested along with a low-light-level electro-optical sensor in a package on the shuttle orbiter. The technology also applies to USAF's space-based surveillance system, a separate new program, and to acquisition, pointing and tracking systems generally. The first phase of the Validator program would cost approximately $50 million. The estimated cost through all three proposed phases would be $500 million.

The first phase experiments could be accommodated in scheduled shuttle missions, Pentagon officials said, using the multipurpose experiment support structure already tested in orbit on Mission 7 of the shuttle.

"The Validator test equipment mounted on the multipurpose support structure would take only about 3 ft. in the shuttle cargo bay and the support structure is already on the shuttle's manifest for experiments," one Pentagon official said. "The NASA support structure would be adapted to a small military payload."

The demonstration would provide badly needed data for a space surveillance system and for acquisition, pointing and tracking required for space-based laser weapons. The initial equipment demonstrated would take advantage of existing long wavelength infrared sensors using a sensor in the class of the Hughes Aircraft/ Army designating optical tracker. The sensor was flight tested five times on boosters fired into space in a program with Boeing as the prime contractor.

Other long wavelength infrared sensors are under consideration for the Validator flight. A long wavelength sensor by Vought Corp., built for the Defense Advanced Research Projects Agency Scoop program, is one. It was flight tested from White Sands Missile Range, N.M., for satellite tracking tests. An Air Force SIRE (space infrared experiment) infrared sensor also could be available for the test.

The first phase could include up to three missions in the shuttle using the infrared sensor coupled to a television camera with a 25-centimeter aperture. "The concept is to use the infrared sensor to acquire the target and hand it over to the electro-optical sensor with its higher resolution and imaging capability for precision tracking," a Defense Dept. official explained. "We could use this approach to speed up and obtain critical data that apply to space-based sensors across the board for application to any type of orbiting defensive weapon system. The technology also would apply directly to antisatellite or defensive satellite systems."

In the second phase of the proposed program, similar experiments would be conducted with a larger 1-meter-dia. aperture on the low-light-level TV sensor for increased resolution. A low-power laser for target illumination might be added to the shuttle package. The laser would be a frequency doubled neodymium YAG off-theshelf device. Average power is only a few watts, with peak power to 60 megawatts. This experiment with the long wave-length infrared sensor, low-light-level television and illuminating laser would be to demonstrate active target tracking, and semi-active homing, if a laser-guided missile were used for target intercept. The company has proposed in the final phase the use of an existing hydrogen or deuterium fluoride laser operating at 2 megawatts as a logical progression for test against a target vehicle. This phase also could include a terminal homing hit-to-kill kinetic energy weapon.

Some Defensive Technologies Study Team members wanted the demonstration to be based in the third phase on target intercepts using a hit-to-kill device fired from the shuttle at a target.

"This is a competing final test if the program is approved, but this test and the use of a high-energy laser are not exclusive," a White House official confirmed. "Until recently there hasn't been much support for using a laser in the Validator concept, but that may all change. There is pressure for the President to establish the credibility of the technology, and this could mean coupling a laser weapon in space with a target."

A number of feasibility demonstrations are being proposed to the Defense Advanced Research Projects Agency (DARPA) that could accelerate the technology for an advanced ballistic missile defense system. Other technology already in development in parallel service or laboratory programs could be applied to early feasibility demonstrations.

A recent DARPA concept is known as Skylight. It would take advantage of the Hughes Aircraft beam director in the canceled Navy Sea Lite laser program, and integrate the optical system with a 3.8-micron, 2-megawatt deuterium fluoride laser device to conduct ground-based tests with a pointing precision of under 100 nanoradians root mean square.

"It could be used in tests against targets for a gee whiz experiment, but it would not provide a basic military capability," an Administration official said. It has the potential to provide lethality demonstrations against spacecraft targets. "Another idea is predicated on a ground-based, medium-range applied technology approach using a small 500-kw. TRW 3.8-micron deuterium fluoride chemical laser mated with a 1-meter-dia. telescope from the Fire Pond program," he said.

Fire Pond is another laser development effort by Massachusetts Institute of Technology and Lincoln Laboratory. "This would provide a precision pointing and tracking demonstration against targets in orbit."

One of the technology-development programs strongly recommended to the President in studies of U.S. ballistic missile defensive technology is the use of small, inexpensive rare gas halide excimer lasers with a ground-based beam director to propagate the laser beam through the atmosphere to an orbiting relay mirror for ballistic missile defense boost-phase engagements.

The same technology could be used for antisatellite missions, with feasibility experiments within five years, Defense Dept. experts said. Several approaches are being studied for the optical requirement, which is likely to be a 10-meter-dia. mirror.

A high-quality laser beam would be extracted from low-cost laser devices using a hydrogen Raman cell (AW&ST July 18, p. 19). The technology is considered a major breakthrough to enhance laser performance including scaling to higher power devices with defraction-limited capability. Adaptive optics would be used to compensate for atmospheric turbulence.

One optical system concept for the ground-based excimer laser with its short visible wavelength benefits is based on phased-array type technology with a segmented mirror functioning along the lines of an electrically steered radar beam. Several small excimer laser devices could be used to illuminate segments. The beams would be combined and remain in phase for propagation to a target in space.

The excimer laser device that would be used in that concept is expected to come from DARPA's EMRLD (excimer repetitively pulsed laser device) program, a competitive effort involving industry. Avco and Rocketdyne are teamed, and are competing against TRW, Northrop and Maxwell Laboratory. The companies are exploring scaling to higher powers with a xenon fluoride laser. Competition is expected to continue into 1984.

"In the past few months, we have had a major breakthrough with excimer lasers, methods that allow an extension of performance in several different directions,"

a