$20 of minor parts from these guys (anti-gravity research). As fun as model rockets without the fire. Maybe more fun because the power water/air pressure is more surprising. You need a bike pump and 2ltr bottle. Clears 200 ft vertical.
Alternately, you can do a totally homemade version - lots of examples on YouTube.
Great book - 50 Dangerous things you should let your children do. We completed about 10 of the experiments including letting your child drive a car and putting unusual things in the microwave (read the book before attempting). Boiling water in a paper cup is astonishing, and shakes your thinking on why things burn. This is an ordinary coffee cup from Peets.
Taipei Grand Hyatt Taipei Longshan Temple - Guanzhou street Wistaria Teahouse - Din Tai Fung - famous soup dumplings Shilin night market - stinky tofu Sin Yeh Restaurant - A9 Brown Sugar - jazz club MediaTek - fabless semiconductor company TSMC - semiconductor fab BenQ Headquarters - consumer electronics Delta Electronics - power supplies Shangai Dumpling - Barcode Lounge / Room 18 - Landis Resort / Hot Springs - National Palace Museum - Chiang Kai-shek Memorial Hall - Fly to Hong Kong, then Bangalore