North Korea has dramatically ramped up missile tests this year and launched a suspected intercontinental ballistic missile (ICBM) on Friday that Japan's defence minister said was capable of striking the U.S. mainland. Here are some characteristics of ICBMs, and North Korea's ICBM arsenal. WHAT ARE ICBMS? ICBMs are ballistic missiles with a minimum range of about 5,500 kilometres (3,400 miles), chiefly designed for nuclear weapons delivery. Some are capable of travelling 10,000 km (6,200 miles) or farther. Some missiles carry only one warhead, but modern ICBMs can carry multiple warheads, each able to it a separate aimpoint, on independently targetable…