I really have no idea where I came up with this idea, but it just really worked. I know my kids still play with their super cool space walk jet packs.
You take a small piece of cardboard, around 10"x10" and drill/ poke four holes in it, two at the top and two at the bottom. Then attach two empty juice bottles (the Juicy Juice ones work best because they are flat) with duct tape. Spray the whole thing with silver spray paint. Thread flat elastic through the holes going in and out of the holes to form two loops that come out the opposite side of the bottles like a backpack (see my terrible drawing). Tie the elastic together and cover with another piece of duct tape. Then I printed off the Nasa logo on sticky label paper, but you could use cardstock and a hot glue gun for on top of the bottles. Voila, an astronaut's jet pack for space exploration.