The report also noted that the energy requirements for a directed energy weapon used as a BMD asset was much higher than the energy needed for the same weapon to be used against those assets. This meant even if the SDI weapons could be successfully developed, they could be attacked by similar weapons that would be easier to develop. The movement of space-based assets in well-known orbital paths also made them much easier to attack and exposed to attack for longer times compared to the same systems being used to attack ICBMs, whose initial positions were unknown and disappeared in minutes.