Two staff reports submitted to Sen. William Proxmire & J. Bennett Johnston in 1987 on the so-called Strategic Defense Initiative (SDI). The 1st is an update on significant problems strategic defenses faced. More than 60 SDI scientists, engineers, project managers, & ballistic missile defense experts were interviewed for this report. Extensive briefings were held at the nations 3 nat. weapons labs conducting SDI research, the A.F. Space Div., & with key defense contractors involved in SDI work. The 2nd report examines the sizable cost of the launch — putting the weapons, sensors & battle management systems in space — that is often overlooked.