Research a space invention that you'd like to recreate -- such as the Hubble Telescope, or the Mars Rover. Depending on your grade level, you might research the invention in-depth, or you might only research its basic capabilities.
Create a reasonable replica of the space invention, again at your grade level. To create the Hubble Telescope, for instance, you might use mirrors and metal if you are in college, but you might use a toilet paper roll if you are in kindergarten.
Write about the invention and display it for others to see.
Come up with your own space invention for a school project if you can't find one you want to recreate. Use your creativity to use a fishbowl for a deep-space breathing apparatus, or build a spaceship out of a refrigerator box.