Some of the most alluring destinations in space exploration are frozen worlds of ice. Take Jupiter’s moon Europa, for example. Its warm salty ocean below the surface is buried under a lunar-wide ice sheet. What’s the best way to explore it?
Perhaps an ice robot could play a role.
Although the world’s space agencies – NASA in particular – are getting better and better at building robots to explore places like Mars, these robots have limitations. Perhaps one of these limitations is most important. As soon as a rover collapses on Mars – or in a location even further away – it’s game over. There’s no viable way to fix something like MSL Curiosity if it fails while exploring the Martian surface.
But what if the world you want to explore is frozen and the robot is made of ice? Could icy robots do a limited amount of self-repairing themselves? Could they actually be partially manufactured and assembled there?
A recent article entitled “Robots Made of Ice: An Analysis of Manufacturing Techniques” explored this possibility. The paper was presented at the 2020 International IEEE Conference (Institute for Electrical and Electronic Engineers) on robotics and systems. Devin Carroll and Mark Yim wrote it. Carroll is Ph.D. A robotics student at the University of Pennsylvania, and Yim is the director of the Grasp Lab and professor of mechanical engineering at the same institution.
The IceBot is currently just a concept with some components made of ice. Photo credit: GRASP Lab.
The entire robot would obviously not be made of ice. But part of the structure could be. The idea focuses on a modular structure that can self-repair or even replicate itself and can be completed after field deployment once terrain obstacles and the details of the mission’s tasks are better understood.
In their summary, the two authors write: “The ice allows greater flexibility in system design, so that the robot structure can be designed and built after use, after tasks and terrain obstacles have been better identified and analyzed.”
Obviously, there are many problems and obstacles with this potential technology. But that’s how they all start.
The couple of authors make it clear that this is preliminary work. “The authors examine a structure-driven approach to investigate compatible manufacturing processes, with an emphasis on the conservation of process energies,” they write. “A mobile robot platform made of ice will be presented as a proof of concept and first demonstration.”
The idea centers on a two-wheeled rover called the Icebot. Icebot is based on the design for Antarctic rovers and has structural elements made of ice.
In their work, the two authors conducted experiments to examine the whole idea. The work was based on two assumptions:
- The robot operates at sub-zero temperatures, and all calculations are based on average annual temperatures at McMurdo Station in Antarctica.
- Blocks of ice are readily available.
Your paper also presents three general design principles.
- Components must be designed in such a way that they can handle heat.
- All electronics, actuators and power sources must be isolated from the melt.
- The ideal way to shape the robot’s ice components depends on the final volume of the part in relation to the volume that needs to be removed from a raw sheet of ice.
There is another overriding condition in all of this as well. For robots that work on other worlds, energy is a precious commodity. Each mission has an energy budget that is carefully managed. Take the Voyager spacecraft, for example. Their impressive longevity is at least partly due to extremely conscientious energy consumption. Therefore, the amount of energy an ice robot uses to make and build itself is of vital importance.
The researchers tested an open flame as a method of melting holes in the ice into which the robot’s actuator would be inserted. Left: A butane torch is used to melt a hole in the ice blank.
Right: A heat map (in? C) of the butane torch and the ice blank. Photo credit: Carroll and Yim, 2020.
Under these conditions, the researchers came up with some interesting ideas.
First of all, the whole scenario would likely not involve a single robot but a couple working together. One unit would be the primary exploration vehicle, the other would be like a mother ship and have the manufacturing and repair capabilities.
In an interview with the IEEE Spectrum, Devin Carroll explained what this could look like. “When I think of an arctic (or planetary) exploration robot that includes self-modification or repair functions, I envision a system with two types of robots: the first explores the environment and collects materials necessary for self-enlargement or repair, and the Second is some kind of manipulator / manufacturing system. We can envision the exploration class of a robot returning to a central location with a request for a plow or other extension and the manufacturing system being able to attach the extension directly to the robot. “
The same arrangement would work for repairs. For example, if the explorer had a crack in one of its ice components, the mothership could create some sort of ice bandage.
The two scientists conducted some tests to substantiate their ideas. They looked at different ways of manipulating ice. For manufacturing, they looked at molding, which involves first melting ice and then pouring it into a mold to be molded. They also dealt with 3D printing and machining. Each method has its advantages and disadvantages, and each has different energy needs.
They also looked at the integration of actuators. As already explained, actuators themselves cannot be made of ice. Actuators are exposed to different loads that ice cannot handle. The integration of the actuators in components made of ice is therefore a critical process.
They experimented with four different ways of integrating actuators:
- Mechanical carving with something like a chisel.
- Melt a hole for the actuator with an open flame.
- Creating a hole for the actuator with a heated metal rod.
- Cutting, for example, with a hole saw.
Each of the methods has its strengths and weaknesses. Everyone also has their own energy needs. The following table lists the energy required for each method to create a mounting pocket for the actuator and freeze it.
Since this is preliminary work, the team did not reach any lasting conclusions. However, their experiments uncovered some pitfalls that must be overcome if on-site ice making and repair is ever to be effectively implemented.
They found that the finish of the essay is critical to its success, which is no surprise. In short, a larger surface area in the joint is better and helps the ice withstand stresses from torque and other forces. Ice thickness was also an issue, which is also not surprising.
The authors summarize their work in the paper’s conclusion. “This work is a step towards a lightweight, adaptable robotic system that can operate in sub-zero environments. This system is suitable for self-reconfiguration, self-replication and self-repair, ”they write.
Left: A heated rod used to melt a hole in the ice blank.
Right: A heat map (in? C) of the heated rod and the ice blank. Photo credit: Carroll and Yim, 2020.
“In order to advance the development of automated methods for creating and assembling this system, we plan to develop a joint module that can be simple
integrated with passive ice blocks, ”they write. That would make the IceBot system simpler and more modular.
They also explained what the future holds for their IceBot concept: “Other future work will include: determining a general class of surfaces that this system can move on, methods for using ice elements to interact with the environment, and further studies of strength limits of the connections between actuators and the ice. “
In the Spectrum IEEE interview, Carroll also spoke about what’s next for their IceBot efforts, highlighting the need for modularity. “My immediate focus is on developing a modular connection that allows us to easily and securely connect actuators to blocks of ice, as well as developing an end effector that allows us to manipulate blocks of ice without permanently deforming them through screw holes or other similar connection methods . ”
There is still a lot of work to be done before ice robotics technology can be implemented. But it’s a tempting development, and Europe and Enceladus are waiting. Agencies like NASA are carefully examining the resources on site for their missions to the moon and Mars.
Ice is widespread in the solar system. The room is cold and many bodies are covered with ice. Could there be an in-situ IceBot in the future?
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