Project Excalibur was a Lawrence Livermore National Laboratory (LLNL) Cold Warera research program to develop an X-ray laser system as a ballistic missile defense (BMD) for the United States. The concept involved packing large numbers of expendable lasers around a nuclear device, which would orbit in space. During an attack, the device would be detonated, with the X-rays released focused by each laser to destroy multiple incoming target missiles. Because the system would be deployed above the Earth's atmosphere, the X-rays could reach missiles thousands of kilometers away, providing protection over a wide area.
Anti-ballistic missile (ABM) systems of the time only attacked the enemy nuclear warheads after they were released by ICBMs. A single ICBM could carry as many as a dozen warheads, so dozens of defense missiles were required per attacking missile. A single Excalibur device contained up to fifty lasers and could potentially destroy a corresponding number of missiles, with all of the warheads still on board. A single Excalibur could thus destroy dozens of ICBMs and hundreds of warheads for the cost of a single nuclear bomb, improving the cost-exchange ratio that had previously doomed ABM systems.
The basic concept behind Excalibur was conceived in the 1970s by George Chapline Jr. and further developed by Peter L. Hagelstein, both part of Edward Teller's "O-Group" in LLNL. After a successful test in 1980, in 1981 Teller and Lowell Wood began talks with US president Ronald Reagan about the concept. These talks, combined with strong support from The Heritage Foundation, helped Reagan ultimately to announce the Strategic Defense Initiative (SDI) in 1983. Further underground nuclear tests through the early 1980s suggested progress was being made, and this influenced the 1986 Reykjavík Summit, where Reagan refused to give up the possibility of proof-testing SDI technology with nuclear testing in space.
Researchers at Livermore and Los Alamos began to raise concerns about the test results. Teller and Wood continued to state the program was proceeding well, even after a critical test in 1985 demonstrated it was not working as expected. This led to significant criticism within the US weapons laboratories. In 1987, the infighting became public, leading to an investigation on whether LLNL had misled the government about the Excalibur concept. In a 60 Minutes interview in 1988, Teller attempted to walk out rather than answer questions about the lab's treatment of a fellow worker who questioned the results. Further tests revealed additional problems, and in 1988 the budget was cut dramatically. The project officially continued until 1992 when its last planned test, Greenwater of Operation Julin, was cancelled.
History Conceptual development
The conceptual basis of short-wavelength lasers, using X-rays and gamma rays, is the same as that of their visible-light counterparts. There were discussions of such devices as early as 1960, the year the first ruby laser was demonstrated.
The first announcement of a successful X-ray laser was made in 1972 by the University of Utah. Researchers spread thin layers of copper atoms on microscope slides and then heated them with pulses from a neodymium glass laser. This caused spots to appear on X-ray film in the direction of the layers and none in other directions. The announcement caused great excitement, but it was soon overshadowed by the fact that no other labs could reproduce the results, and the announcement was soon forgotten. In 1974, the University of Paris-Sud announced lasing in an aluminum plasma created by a pulse of laser light, but, once again, the results were regarded skeptically by other labs.
DARPA had been funding low-level research into high-frequency lasers since the 1960s. By late 1976 they had all but given up on them. They commissioned a report by Physical Dynamics, which outlined possible uses of such a laser, including space-based weapons. None of these seemed promising, and DARPA dropped funding for X-ray laser research in favor of the more promising free electron laser.
In June 1977, two well-known Soviet researchers, Igor Sobel'man and Vladilen Letokhov, displayed a film exposed to the output of plasmas of chlorine, calcium and titanium, similar to the Utah results. They were careful to point out that the results were very preliminary and further study was required. Over the next few years, a small number of additional papers on the topic were presented. The most direct of these was Sobel'man's statements at a 1979 conference in Novosibirsk when he said he was observing lasing in a calcium plasma. As with earlier announcements, these results were met with skepticism.
First attempts at Livermore
George Chapline had been studying the X-ray laser concept through the 1970s. Chapline was a member of Teller's speculative-project "O-Group" and began to discuss the concept with fellow O-Group member Lowell Wood, Teller's protégé. The two collaborated on a major review of the X-ray laser field in 1975. They suggested such a device would be a powerful tool in materials science, for making holograms of viruses where a conventional laser's longer wavelength did not provide the required optical resolution, and as a sort of flashbulb for taking images of the nuclear fusion process in their inertial confinement fusion devices. This review contained the calculations that demonstrated both the rapid reaction times needed in such a device and the extremely high energies required for pumping.
Chapline attended a meeting where Sobel'man was giving a talk on his work on X-ray lasers. Chapline had learned of the unique underground nuclear tests made on behalf of the Defense Nuclear Agency (DNA), where the burst of X-rays produced by the nuclear reactions were allowed to travel down a long tunnel while the blast itself was cut off by large doors that slammed shut as the explosion approached. These tests were used to investigate the effects of X-rays from exoatmospheric nuclear explosions on reentry vehicles. He realized this was a perfect way to pump an X-ray laser.
After a few weeks of work, he came up with a testable concept. At this time the DNA was making plans for another of its X-ray effects tests, and Chapline's device could easily be tested in the same "shot". The test shot, Diablo Hawk, was carried out on 13 September 1978 as part of the Operation Cresset series. However, the instrumentation on Chapline's device failed, and there was no way to know if the system had worked.
Congress directed that $10million be given to both Lawrence Livermore National Laboratory (LLNL) and Los Alamos National Laboratory (LANL) for weapons tests on entirely new concepts. Chapline was given the go-ahead to plan for a new test dedicated to the X-ray laser concept. In the DNA tests, the reentry vehicle had to be retrieved for study after the test, which demanded the complex system of protective doors and other techniques that made these tests very expensive. For the X-ray laser test, all of this could be ignored, as the laser was designed to be destroyed in the explosion. This allowed the laser to be placed at the top of the vertical access shaft, which greatly lowered the cost of the test from the typical $40million needed in a DNA shot. Given the schedule at the Nevada Test Site, their test would have to wait until 1980.
Dauphin success
Peter Hagelstein was in an undergraduate physics program at MIT in 1974 when he applied for a Hertz Foundation scholarship. Teller was on the Hertz board, and Hagelstein soon had an interview with Lowell Wood. Hagelstein won the scholarship, and Wood then went on to offer him a summer position at LLNL. He had never heard of the lab, and Wood explained they were working on lasers, fusion, and similar concepts. Hagelstein arrived in May 1975, but nearly left when he found the area to be "disgusting" and immediately surmised they were working on weapons research when he saw the barbed wire and armed guards. He stayed on only because he met interesting people.
Hagelstein was given the task of simulating the X-ray laser process on LLNL's supercomputers. His program, known as XRASER for "X-Ray laser", eventually grew to about 40,000 lines of code. He received his master's degree in 1976 and took a full-time job at the lab, intending to lead the development of a working laser. The idea was to use the lab's powerful fusion lasers as an energy source, as Hagelstein and Wood had suggested in their review paper. Hagelstein used XRASER to simulate about 45 such concepts before he found one that appeared to work. These used the lasers to heat metal foils and give off X-rays, but by the late 1970s, none of these experiments had been successful.
After the Diablo Hawk failure, Hagelstein reviewed Chapline's idea and came up with a new concept that should be much more efficient. Chapline had used a lightweight material, a fiber taken from a local weed, but Hagelstein suggested using a metal rod instead. Although initially skeptical, Wood came to support the idea and successfully argued that both concepts be tested in Chapline's shot. The critical test was carried out on 14 November 1980 as Dauphin, part of Operation Guardian. Both lasers worked, but Hagelstein's design was much more powerful. The lab soon decided to move forward with Hagelstein's version, forming the "R Program", led by another O-Group member, Tom Weaver.
Renewed interest
Hagelstein published his PhD thesis in January 1981 on the "Physics of Short-wavelength-laser Design". In contrast to Chapline and Wood's earlier work which focused on civilian applications, the thesis' introduction mentions several potential uses, even weapons taken from science fiction works.
Hagelstein soon returned to the civilian side of the X-ray laser development, initially developing a concept in which the lab's fusion lasers would produce a plasma whose photons would pump another material. This was initially based on fluorine gas confined inside a chromium foil film. This proved to be too difficult to manufacture, so a system more like the earlier Soviet concepts was developed. The laser would deposit enough energy in a selenium wire to cause 24 of the electrons to be ionized, leaving behind 10 electrons that would be pumped by collisions with the free electrons in the plasma.
After several attempts using the Novette laser as an energy source, on 13 July 1984 the system worked for the first time. The team calculated that the system produced laser amplification of about 700, which they considered to be strong evidence of lasing. Dennis Matthews presented the success at the October 1984 American Physical Society Plasma Physics Meeting in Boston, where Szymon Suckewer of Princeton University presented their evidence of lasing in carbon using a much smaller laser and confined the plasma using magnets.
Teller in Washington, AvWeek "leaks"
The success of the Dauphin test presented a potential new solution to the BMD problem. The X-ray laser offered the possibility that many laser beams could be generated from a single nuclear weapon in orbit, meaning a single weapon would destroy many ICBMs. This would blunt the attack to such an extent that any US response would be overwhelming in comparison. Even if the Soviets launched a full-scale attack, it would limit US casualties to 30million. In February 1981, Teller and Wood traveled to Washington to present the technology to the policy makers and request greater financial support to pursue the development.