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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Brilliant Pebbles | 5/9 | https://en.wikipedia.org/wiki/Brilliant_Pebbles | reference | science, encyclopedia | 2026-05-05T13:24:19.440513+00:00 | kb-cron |
George H. W. Bush became president in 1989, as the Cold War was coming to an end. He immediately ordered a review of all ongoing strategic programs. This led to the June 1989 National Security Directive 14, continuing the SDI program on the basis of the SDS. Meanwhile, Abrahamson's tenure at the helm of SDIO came to an end. He wrote an end-of-term report stating that Brilliant Pebbles should be aggressively pursued and that tests could be carried out within two years for a system deployment in five years at a total cost of $25 billion. Bush and Vice President Dan Quayle were vocal supporters of the Pebbles concept in the press; Quayle noted its low cost and light weight and stated that "it could revolutionize much of our thinking about strategic defense". Abrahamson's replacement, George L. Monahan, Jr., planned a rapid series of studies with the goal of moving to approval for deployment by the end of the year. Among the first of these studies was one prepared by the JASONs, a standing committee of science advisers administered by Mitre Corporation. Their report essentially stated that there were no apparent "show stopper" issues in the concept, although they did have concerns about possible countermeasures. Soon after, a similar report by the Defense Science Board offered largely the same assessment. A third review focussing on possible Soviet countermeasures did find that the system was possibly compromised by a number of issues, but pointed out that this was true for any other space-based system and these should not be the basis for selecting some other system over SDS. The final study, carried out late in 1989, was an Air Force report making one last comparison between the SDS concept with simplified "gun rack" garages versus a Pebbles system, which concluded the former would cost $69 billion and the latter $55 billion. This system included only 4,600 pebbles, and some of the savings were due to the removal of the high-orbit Boost Surveillance and Tracking System (BSTS), a role the pebbles themselves would fill. Monahan had already given the DAB a "heads up" that major changes to the SDS concept were coming, and had been told to prepare a report for them for early 1990. The new system relied on Brilliant Pebbles as the baseline design. BSTS was not cancelled outright, but instead passed to the Air Force as a replacement for their existing Defense Support Program satellites. Other parts of the original design, including the land-based ERIS missile and its host of supporting radars and low-orbit satellites, remained. Early contract tenders were sent to six suppliers for production vehicles. Testing was to run in a two-phase program, some of it in parallel. To start, LLNL would supply prototype pebbles interceptors that would be tested both on the ground and in space after launch on sounding rockets. This series would conclude in February 1993, in time to allow the President to review the system and decide whether to proceed. Information from these tests would be fed back into the production designs. The first of these prototypes would begin testing in June 1990 and end in June 1993.
=== Global Protection Against Limited Strikes ===
A month later, another independent review by Henry F. Cooper strongly supported Brilliant Pebbles over the alternatives. Cooper's report went much further. Considering the major changes to the strategic outlook with the ongoing dissolution of the Soviet Union, Cooper stated that the massive attack that SDS was designed to defeat was no longer the only concern, or even the main one. Instead, it was United States forces in the field that bore the brunt of the missile threat, this time from short and medium range missiles. Although the SDS system should move ahead, he suggested that the system be modified to provide defenses against these new threats. Cooper noted that pebbles in their current form were designed to operate against a missile in the boost phase. Against a short-range rocket, this period would be too short for a pebble to reach it. To make it effective in this "Protection Against Limited missile Strikes" concept, or PALS, the pebbles should be able to continue tracking the missiles after their motors had burned out. This would either require a dramatic increase in the capability of the pebble's seekers, or require a network of low-orbit satellites to provide this same information. Following Cooper's lead, Monahan began the Mid-and-Terminal Tiers Review (MATTR) in early 1990. Before this was complete, Cooper was appointed as the director of the SDIO on 10 July 1990, and Monahan retired. Within SDIO at least, PALS was now the mainline concept. In order to fill the need for a ground-based interceptor to back up the pebbles, the Army began development of the High Endoatmospheric Defense Interceptor (HEDI), essentially a short-range, mobile version of ERIS. A new lightweight interceptor, LEAP, would arm both ERIS and the Navy's Standard Missile. As work continued, the Gulf War broke out and Cooper's scenario of United States troops being attacked by short range missiles came true; the nightly news carried vivid images of Scud missiles being attacked by Patriot missiles. Bush praised Patriot, claiming that 42 launches had resulted in 41 intercepts. Congress, formerly skeptical of SDI, suddenly had a very different opinion of the matter, especially with the realignment of the concept towards the PALS concept which would have been helping deal with missiles like Scud. On 29 January 1991, Bush used the State of the Union speech to announce that SDI was being refocussed to the new "Global PALS", or GPALS, concept: