page_title: Brilliant Pebbles
section_title: Excalibur
hierarchical_section_title: Brilliant Pebbles / History / Excalibur
caption_attribution_description: English: Excalibur was a proposed x-ray laser based anti-missile technology. It used a nuclear warhead surrounded by a number of metal rods that acted to focus the output of the explosion into narrow beams that would be aimed at nuclear missiles and their warheads. This image shows a single Excalibur exploding in the upper left of the image and firing at three targets. In practice, each warhead would fire at dozens or thousands of targets at once
context_page_description: Brilliant Pebbles was a ballistic missile defense system proposed by Lowell Wood and Edward Teller of the Lawrence Livermore National Laboratory in 1987, near the end of Cold War. The system would consist of thousands of small missiles, not unlike conventional heat seeking missiles, which would be placed in orbits so that hundreds would be above the Soviet Union at all times. If the Soviets launched its ICBM fleet, the pebbles would detect their rocket motors using infrared seekers and collide with them. Because the pebble strikes the ICBM before the latter could release its warheads, each pebble could destroy several warheads with one shot.
  The name is a play on the idea of Smart Rocks, a concept promoted by Daniel O. Graham as part of the Strategic Defense Initiative. This used large battle stations with powerful sensors, carrying dozens of small missiles, the rocks. To keep enough missiles above the Soviet Union at any given time, a minimum of 423 stations would be needed. The United States Air Force pointed out that this would require an enormous space lift capability, well beyond what was available.
context_section_description: Around the same time that Graham was formulating his Smart Rocks concept, studies into X-ray lasers at Livermore made a sudden breakthrough. Nuclear explosions give off massive amounts of X-ray energy, and it appeared possible these could be focussed down into narrow beams as the basis for a long-range laser weapon. Previous systems had used carbon-based lasing materials, but calculations showed that the energy could be greatly increased by using a metal rod instead. The idea had been largely theoretical until a key test of the new concept in November 1980.
  By surrounding a nuclear warhead with dozens of rods, each could be independently aimed to shoot down an enemy missile. A single such warhead might be able to destroy 50 missiles in a radius of a 1,000 kilometers (620 mi) around it. A small fleet of such warheads could seriously disrupt any Soviet attack. In February 1981, Teller and Wood traveled to Washington to pitch the idea of a Manhattan Project-level development effort to produce these weapons in what they called Project Excalibur.
  Teller was also a member of the High Frontier group and began attacking Graham's Smart Rocks as "outlandish", and suggested his own Excalibur be used in its place. Graham countered by pointing out a serious flaw in Excalibur; he noted that it worked by blowing itself up, so in the event a Soviet anti-satellite weapon approached, it could either blow itself up to attack the ASAT, or allow itself to be blown up by the ASAT. In either case, the Excalibur would be destroyed. Teller was initially stumped but soon returned with a solution. In this concept, the Excalibur weapons would be placed on missiles on submarines and launched when needed.
  Seeing himself increasingly sidelined, Graham left the group in December 1981 to form High Frontier Inc. In March 1982, they published a glossy book on the topic. It claimed that the system could be "fully deployed within five or six years at a minimum cost of some $10–$15 billion." A pre-publication copy was sent to the Air Force, who dismissed it, saying that it "had no technical merit and should be rejected."
caption: Concept art of Excalibur. Had it worked, would have been able to attack multiple ICBMs in a single shot.
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