One federal budget proposal is to end free admission to the Smithsonian museums. If this happened, museums in Washington, D.C., such as the National Air and Space Museum and the National Museum of Natural History, might charge $ 7.50 an adult. Apollo Command Module, at the National Air & Space Museum (Courtesy jurvetson/Flickr) The bipartisan panel tasked by President Obama to pinpoint policies to fix our national financies would like to add fees for entry to favorite institutions. (See the full proposal. It opens as a PDF; you can download free Adobe software here). A fee of about $ 7.50 an adult could earn the federal government about $ 225…