Project Orion in the 1960s envisioned the use of nuclear shaped charges for propulsion. The nuclear explosion would turn a tungsten plate into a jet of plasma that would then hit the drive pusher plate. About 85% of the bomb's energy could be directed into the target as plasma, albeit with a very wide cone angle of 22.5 degrees. A 4,000 ton spacecraft would use 5 kiloton charges, and a 10,000 ton spacecraft would use 15 kiloton charges. Orion also researched the possibility of nuclear shaped charges being used as weapons in space warfare. These weapons would have yields of a few kilotons, could convert about 50% of that energy into a plasma jet with a velocity of 280 kilometers per second, and could theoretically get beam angles as low as 0.1 radians (5.73 degrees), quite wide but considerably narrower than the propulsion unit.