Though other authors have reported the use of dry ice for making
bombs, the goal here was to harness this energy for
propulsion. To this end, John Van Hyfte and I
created a rocket to be propelled by dry ice sublimation.
Theory:
Carbon dioxide sublimes from the solid to the gas state at -78 deg C
under 1 atm of pressure. It's heat of vaporization is 5539 J/mol and its
density is 1.03 g/cm^3 at -20 deg C.
If frozen CO2 is placed into warm tap water, the gas will immediately
begin subliming and will increase dramatically in volume. The increasing
volume will raise the pressure in a containment vessel and if there is
a hole in the vessel, will force material through the hole.
Our rocket was designed with a nozzle so that expanding CO2 would force
liquid water out. The resulting d(mass)/dt would provide thrust and
thus propel the rocket.
Results:
Our rocket (a small plastic Dr. Pepper bottle) was only able to generate
small amounts of thrust and did not move appreciably. After several attempts
we decided to simply throw some CO2 into a bottle, fill it with water and
cap it. The result was a bottle which slowly grew and hissed for about
10 minutes and then exploded wildly. The sound was the equivalent of a
12 ga. shotgun and scared at least one of my neighbors nearly to death.
The bottle was torn into three shredded plastic strips. The bomb blew
a crater in my yard and splattered grass and mud onto my fence.
Pictures:
The photos below show (clockwise from top left): John with the dry-ice
rocket on a guide-wire; John arming a second version of the rocket; The
festering bomb; and the crater and remains of the bomb explosion.