The ability to move between air and water with miniature robots would allow distributed
water sampling and monitoring of a variety of unstructured marine environments,
such as coral reefs and coastal areas. To enable such applications, we are developing a
new class of aerial-aquatic robots, called Aquatic Micro Aerial Vehicles (AquaMAVs),
capable of diving into the water and returning to flight. One of the main challenges in
the development of an AquaMAV is the provision of sufficient power density for take-off
from the water. In this paper, we present a novel system for powerful, repeatable aquatic
escape using acetylene explosions in a 34 gram water jet thruster, which expels water
collected from its environment as propellant. We overcome the miniaturisation problems
of combustible fuel control and storage by generating acetylene gas from solid calcium
carbide, which is reacted with enviromental water. The produced gas is then combusted in
air in a valveless combustion chamber to produce over 20N of thrust, sufficient to propel
small robots into the air from water. The system for producing combustible gases from
solid fuels is a very compact means of gas storage, and can be applied to other forms of
pneumatic actuation and inflatable structure deployment.