Even as Nike Ajax was being tested, work started on Nike-B, later renamed Nike Hercules (MIM-14). It improved speed, range and accuracy, and could intercept ballistic missiles. The Hercules had a range of about 100 miles (160 km), a top speed in excess of 3,000 mph (4,800 km/h) and a maximum altitude of around 150,000 ft(30 km). It had solid fuel boost and sustainer rocket motors. The boost phase was four of the Nike Ajax boosters strapped together. In the electronics, some vacuum tubes were replaced with more reliable solid-state components.