a first-order evaluation, the relative vulnerability of the SPS to that of a terrestrial system reduces to a comparison of the vulnerability of the spaceborne parts of the SPS (and launch sites) to the vulnerability of the terrestrial system’s fuel supply line(s). The spaceborne segment of the SPS will be vulnerable to military attack and to the activities of sabotuers. Vulnerability to terrorist attacks is not likely for some time because such attacks would require the use of either a high-technology space transportation system or sophisticated ground-based equipment capable of destroying a target 36,000 km away. Launch sites are vulnerable in much the same way as the terrestrial power plants except that security probably would be better at the launch sites. There is likely to be at least a nominal effort to harden the satellite components and space transportation units against the hits and explosions of a military attack and the resulting environment. Hardening may be needed against interceptor and satellite killer impacts and explosions, nuclear radiation, high-energy laser and particle weapons, and electronic warfare waged to obstruct the flow of radiation or to compromise and/or gain control of satellite functions. Passive hardening is unlikely to be effective in all these areas; therefore, it is believed that dependable hardening against military attack will necessarily include an active SPS self-defense system unless other assets capable of defending the SPS are available for this function at the time of SPS deployment (see appendix B).
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