Asteroids come in all shapes and sizes. Most of them are round in shape, although many have features that make them difficult to land on – they are basically just masses of rock loosely held together by gravity. In space exploration terminology, they are known as “debris piles”. Many of the asteroids that humanity has visited are considered debris, including Itokawa and Dimorphos, the destinations of Hayabusa and Dart, respectively. However, as the Philae spacecraft’s experiments showed when it attempted to rendezvous with comet 67P/Churyumov-Gerasimenko, landing on this object with extremely low surface gravity can be challenging. Enter a new concept from researchers at the University of Colorado, Boulder. Their idea, known as Area-of-Effect Softbots (AoES), could help future asteroid explorers, and even miners, overcome some of the challenges they face with these small objects.
PI Jay McMahon and his team took on work originally supported by NASA’s Institute for Advanced Concepts (NIAC) in Phase 1 in 2017. Their idea was simple — to design a robot that can latch onto objects in low gravity while inserting machines that can drill into asteroids for valuable materials, be it water ice or precious metals.
This sounds a lot easier than it is. Asteroids have much lower gravity, so the spacecraft must use a stabilization system, which only works occasionally (again, see Philae’s retrograde flight). More importantly, once the spacecraft has docked to a location, it’s not easy to launch it again or redirect it to another part of the same asteroid.
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This is where the soft robot idea comes in. There are many prototype robots with shape-shifting bodies being developed on Earth. They are usually useful in search and rescue or hazardous environments such as nuclear reactors. But using it in space, especially when interacting with asteroids, is a new idea.
Softbots have four main advantages over other types of spacecraft when interacting with asteroids. They can stick to surfaces better than most. Once on the surface, they can crawl along it. They can also launch themselves from surfaces by “jumping”. Finally, they can reorient themselves to a different location on the asteroid with a simple solar sail.
First, let’s deal with adhesion – soft robots can have a large surface area, and that surface area can be made of almost any flexible material. How this material attaches to the surface of the asteroid is an important consideration for AoES. An asteroid usually has a small enough surface gravity that the other forces are the main forces holding a pile of debris together. Known as van der Waals forces, these forces apply force at every point of contact between rocks. Latching uses a similar method, allowing the robot’s “soft” parts to latch onto the surface of the asteroid.
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While AoES could use van der Waals forces to attach to asteroids, it would also apply a force known as “electrosticking” which uses electrodes in the flexible parts of the robot to induce charges within it, which in turn also induce opposite charges on the surface. This allows the robotic arm to “stick” to the surface using the bonding force of opposite electrical charges, thereby securing the robot more firmly to the asteroid’s surface.
But what if he doesn’t want to get stuck on the surface of the asteroid? One option is to crawl this surface, and AoES can do that. The designs discussed in Dr. McMahon for NIAC uses a type of actuator known as a HASEL actuator. This allows the robot to attach one part of its attachment (such as the tip) to the asteroid while contracting another part (such as the center), effectively allowing it to crawl along the asteroid’s surface while maintaining firm contact with the surface.
If this mode of transportation isn’t enough, AoES can actually jump to the next location. In a similar way to ‘crawling’, it selectively controls which part of the tip causes electrical cohesion to be forced while other parts contract, but in this case the contraction is released rapidly at the same time the electrical cohesion is turned off, effectively allowing AoES to push the asteroid back into surrounding space. Done right, it can even activate AoES to maneuver to the next target on an asteroid using only the force you put into its own jump.
Take a look at the interesting engineering of some of the soft robots we use on Earth.
But if that doesn’t work, AoES has another feature – it can turn into a solar sail. The AoES robot can effectively use light to propel itself in a certain direction by fully extending its appendages. So if the operator (or AI robot) wants to maneuver to another location farther than the jumps can do, it simply maneuvers itself using sunlight to get there. These techniques represent a radical departure from current small object landing methodologies, marking a leap forward in operations on asteroids.
So what will AoES do when you get there? In the concept discussed in the NIAC paper, the main goal is to get material into a central collection system, where it is ground or vaporized and can then be transported back to larger processing ships in orbit around the asteroid. In fact, multiple AoES can be active on an asteroid at any given time, and all of them can return material to their carrier.
This ability, and the flexibility to have more than one system on a given asteroid at a time, makes AoES very attractive as a moraine asteroid mining solution. However, it does not appear that AoES was selected for the second round of NIAC funding in 2018, despite research by Dr. McMahon and his team have been consistent since then, including papers on how to use AoES in low Earth orbit or to deflect potentially dangerous asteroids. Perhaps the idea was too early for its time, and we may see dozens or hundreds of soft-bodied robots hanging around potentially profitable asteroids in the not too distant future.
Learn more:
Jay McMahon – Splitting asteroid piles using AoES (Area of Impact Soft Robotics)
McMahon dkk. – Robotic and fuel-free soft servers for LEO spacecraft
Utah – Don’t bother trying to destroy the asteroid pile of debris
UT – A debris pile asteroid is probably the best place to build an extraterrestrial habitat
main picture:
A model of possible AoES spacecraft configurations.
Kredit – Jay McMahon
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2023-07-24 18:33:49
#Engineers #designing #robots #latch #crawl #navigate #asteroid #piles #debris
