Manta rays and flying fish transition from the sea into the air in breathtaking fashion. Now, a team of scientists has developed aerial-aquatic robots that can glide and have a similar ability to transition seamlessly between the air and sea.
The new type of robot could be used in areas where quick movement is needed, such as disaster relief zones, reservoir management, and agriculture.
A new propulsion approach
Researchers have created untethered robots that react with water to generate combustible gas in order to blast from pools of water into the air. Once in the air, the robots were able to glide for a short time before reaching the ground.
This new approach could be used as a critical design feature for aerial-aquatic robotics. These could be used in disaster response for floods, agriculture, reservoir management, and oceanography.
The robots could also be used in situations where time and resources are of the essence. We can imagine them being used in remote watery terrains such as caves to find people who have been trapped in dangerous conditions.
Transitioning from water to flight
Designing a robot to move seamlessly from water to flight requires a power-intensive unit that is especially challenging to make in a small size.
The more traditional method of combustion usually requires a tethered robot connected to supplies. This would make it difficult for the robot to glide.
Raphael Zufferey and his colleagues have designed untethered robots that they were able to launch multiple times from the water using an impulsive actuation force that was over 25 times the robot’s weight. After the launch, the robot was able to immediately start gliding.
They managed this by adding a small reserve (0.2 grams) of calcium carbide powder to the robot, which reacts with the water when exposed. When reacting, combustible acetylene gas is formed, which is ignited in a small combustion chamber, allowing the thrust that launched the robot out of the water like a manta ray.
The prototype could achieve a flight distance of 26 meters and was able to run a total of 22 flight on 160 grams of calcium carbide powder, in an indoor tank and an outdoor pond.
The robot can operate over small waves, though big ones are still a stumbling block. The researchers will look to make future models more robust.