subject
http://dbpedia.org/resource/Boeing_X-20_Dyna-Soar
http://dbpedia.org/resource/OK-GLI
http://dbpedia.org/resource/Hopper_(spacecraft)
http://dbpedia.org/resource/Space_Shuttle_Pathfinder
http://dbpedia.org/resource/Buran_(spacecraft)
http://dbpedia.org/resource/HOPE-X
http://dbpedia.org/resource/Hermes_(spacecraft)