CAPE CANAVERAL, FL - APRIL 29: A SpaceX rocket sits on launch pad 39A as it is prepared for the NROL-76 launch on April 29, 2017 in Cape Canaveral, Florida. SpaceX will attempt to deliver a classified payload to orbit and liftoff is scheduled for tomorrow at 7 a.m. ET from Kennedy Space Center. (Photo by Joe Raedle/Getty Images)