From left, Wayne Arrington, a Boeing Company technician, and Steve Presti, a mechanical technician at NASA's Marshall Space Flight Center in Huntsville, Ala., install Developmental Flight Instrumentation Data Acquisition Units in Marshall's Systems Integration and Test Facility. The units are part of NASA's Space Launch System (SLS) core stage avionics, which will guide the biggest, most powerful rocket in history to deep space missions. When completed, the core stage will be more than 200 feet tall and store cryogenic liquid hydrogen and liquid oxygen that will feed the vehicle's RS-25 engines. The hardware, software and operating systems for the SLS are arranged in flight configuration in the facility for testing. The new Data Acquisition Units will monitor vehicle behavior in flight -- like acceleration, thermal environments, shock and vibration. That data will then be used to validate previous ground tests and analyses models that were used in the development of the SLS vehicle.