Missileer
Active member
Some may be interested in this. I worked at this for three years maintaining radar and searchlights. I noticed it has been filmed during Spring and Summer when the boats aren't covered with ice and the river had 11 inches of ice up in Wisconsin.
http://www.mississippirivermuseum.com/invis.industry.pdf
http://www.mississippirivermuseum.com/invis.industry.pdf