Visitors on a bus tour from the U.S. Space & Rocket Center make a stop at the historic Redstone test site, a National Historic Landmark at the NASA Marshall Space Flight Center, on Wednesday, April 9, 2014, in Huntsville, Ala.( Smiley N. Pool / Houston Chronicle )


Visitors on a bus tour from the U.S. Space & Rocket Center make a stop at the historic Redstone test site, a National Historic Landmark at the NASA Marshall Space Flight Center, on Wednesday, April 9, 2014, in Huntsville, Ala.( Smiley N. Pool / Houston Chronicle )