Ralph Semmel

This image made available by the Johns Hopkins University Applied Physics Laboratory on Wednesday, May 31, 2017 depicts NASA's Solar Probe Plus spacecraft approaching the sun. On Wednesday, NASA announced it will launch the probe in summer 2018 to explore the solar atmosphere. It will be subjected to brutal heat and radiation like no other man-made structure before. (Johns Hopkins University Applied Physics Laboratory via AP)

Replacing this federal scientist requires a nationwide search

Ralph Semmel, director of the Applied Physics Laboratory for the last 15 years, is stepping down, and discusses his work for DoD, NASA and national security.

Technology