un interessante articolo, con video, dalla NASA:
http://www.nasa.gov/content/goddard/...l#.VCCY7WIayK2
https://www.youtube.com/watch?v=TWjtYSRlOUI
http://www.nasa.gov/content/goddard/...l#.VCCY7WIayK2
https://www.youtube.com/watch?v=TWjtYSRlOUI