The US Air Force has paid $125 million for the first portion of a $3 billion contract with Boeing Co. of Seattle to research whether space-based lasers can shoot down long-range missiles. Boeing is working in collaboration with Lockheed Martin Missiles and Space of Sunnyvale, Calif., and TRW Inc. of Redondo Beach, Calif., at the Air Force's Space and Missile Systems Center in Los Angeles. The initial work is slated for completion in about 18 months. Defense officials assure that the program does not violate the Anti-Ballistic Missile Treaty the US has with Russia, according to recent news releases. The treaty bars the development of a space-based missile defense system.