Seoul [South Korea], March 20 (ANI): North Korea has successfully conducted a ground-jet test of a solid-fuel engine for a new type of intermediate hypersonic missile amid heightened tensions on the Korean peninsula, according to Yonhap News Agency. Reportedly, hypersonic missiles are on the list of sophisticated weapons North Korean leader Kim Jong-un vowed to develop during a key party congress in 2021, along with nuclear-powered submarines, spy satellites and solid-fuel intercontinental ballistic missiles. The missiles travel at a speed of at least Mach 5, five times the speed of sound, and…