HUNTSVILLE, Ala. — Using advanced digital design methods, the two teams competing to develop the Missile Defense Agency’s Next-Generation Interceptor are nearing a key milestone by the end of the year: a preliminary design review for the all-up round. The agency chose two teams – Northrop Grumman working with Raytheon Technologies , an RTX company, and Lockheed Martin with Aerojet Rocketdyne – to design a replacement for the Ground-based Midcourse Defense system’s Ground-Based Interceptors .