Louis Dijour Smullin was an American electrical engineer who spend most of his career at the Massachusetts Institute of Technology. He is best known for his work with Giorgio Fiocco to measure the distance to the Moon using a ruby laser in 1962, shortly after that device was invented. Earlier, he had worked in the microwave radar field at the MIT Radiation Laboratory and was instrumental in creating the Lincoln Laboratory that carried on this work. Later he worked on developing instrumentation for nuclear fusion research and many other projects. He retired in 1986 but worked in the department until 2001.