Online, there are many astronomy projects for young children in elementary school. Out of the four or five I checked out, Star Child (http://www.starchild.nasa.gov) was by far the best one for teaching the basics of astronomy. It asked questions and had ready answers.
At this site, there is a list of those who have contributed to the space science with full biographies and their accomplishments. Some of the names like Sally Ride, Buzz Aldren, Neil Armstrong, Alan Shepherd, Isaac Newton, Galileo, and many others, they may have already read about. If any of these are selected for a project they need look no further for information than at Star Child.
Space probes are defined and their purpose is given. The Hubble space probe is explained here and for projects concerning this communication satellite the only missing ingredient would be a child's imagination. Possibly a space probe could be made out of something around the house and made to look as authentic as only a third or fourth grade student could make it.
Interesting details such as what happens to these space probes once they are no longer useful are potential good astronomy projects. A child, once learning that they seldom return to earth but often land on other planets, would have a field day deciding what would happen to his space ship'.
In the same line of thought, the twin space rovers, Spirit and Opportunity that were launched in 2003 could be furtherd explored. These two busy little robots that rolled all over the surface of Mars in 2004 would make wonderful astronomy projects for prospective astronauts. What they were looking for was water, and there's evidence that there has been a lot of it on Mars. A project here would be not only educational, but lots of fun. The student would be the earth scientist telling the rovers where to go. These experiments would not necessarily be difficult today since for a six or seventh grader; they could refashion their toy remote cars and jeeps. They would need only to supply the facts, and the art work, and the detailing.
Or a project could concern itself with space suits. Possibly youngsters would be asked to put together something resembling a space suit. The information needed could be found at this site and some old clothes and a big roll of duck tape.
All the necessary information is found at the Star Child. I am sure they will be happy to know that while in the space craft the astronauts will not have to clunk around in the heavy suits; they can dress as they normally do. They will only have to wear the heavy equipment on entry and when landing back on earth. Of course if they expect to do any space traveling they will have special equipped suits for this, as well.
And the message of study, study, study hopefully will not be lost on these potential astronauts. That is the only requirement at this stage of their preparation. And with the help of projects that will whet their appetite for such adventures, and the ready information that can be found on-line, what's stopping these future moon walkers?