 It involved removing the three main engines (they were slated to be reused on NASA's Space Launch System); the windows were given to project engineers for analysis of how materials and systems fared after repeated space exposure; the communications modules were removed due to national–security concerns; and hazardous materials such as traces of propellants were thoroughly flushed from the plumbing.The total cost of preparation and delivery via a modified Boeing 747 was estimated at $26.5 million in 2011 dollars.NASA ran a program to donate thermal protection system tiles to schools and universities for US$23.40 each (the fee for shipping and handling).